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1
Maende, Cleophas Makokha. "An application of a model of maize growth to maize production by smallholders in Kenya". Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240744.
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Drost, Roelof Gerrit. "MAIS, a mechanistic model of maize growth and development". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ61892.pdf.
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Schortemeyer, Marcus. "Effects of nitrogen form on the growth of maize seedlings /". [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10739.
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Massignam, Angelo Mendes. "Quantifying nitrogen effects on crop growth processes in maize and sunflower /". St. Lucia, Qld, 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17639.pdf.
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Verheul, Michel J. "Seedling growth of maize (<> L.) genotypes under chilling conditions /". [S.l.] : [s.n.], 1992. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=9855.
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Anil, Leena. "The growth and utilization of forage maize intercrops for livestock production". Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266795.
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Raymond, Fred Douglas. "Reducing Corn Yield Variability and Enhancing Yield Increases Through the Use of Corn-Specific Growth Models". Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/36304.
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Crop simulation models (CSMs) are used to evaluate management and environmental scenarios on crop growth and yields. Two corn (Zea Mays L.) crop growth simulation models, Hybrid-Maize, and CERES-Maize were calibrated and validated under Virginia conditions with the goal of better understanding corn response to variable environmental conditions and decreasing temporal yield variation. Calibration data were generated from small plot studies conducted at five site-years. Main plots were plant density (4.9, 6.2, 7.4, and 8.6 plants m-2); subplots were hybrids of differing relative maturity (RM) [early = Pioneer® Brand â 34B97â (108 day RM); medium = Pioneer® Brand â 33M54â (114 day RM); and late = Pioneer® Brand â 31G66â (118 day RM)]. Model validation was generated from large scale, replicated strip plot trials conducted at various locations across Virginia in 2005 and 2006. Prior to model adjustments based on calibration data, both CSMs under predicted corn grain yield in calibration and validation studies. CERES-Maize grain yield prediction error was consistent across the range of tested plant density while accuracy of Hybrid-Maize varied with plant density. Hybrid-Maize-estimated biomass production was highly accurate. Greater leaf area index (LAI) and biomass production were measured than was predicted by the CERES-Maize CSM. Both CSMs were modified based on calibration data sets and validated. Validation results of the calibrated CSMs showed improved accuracy in simulating planting date and environmental effects on a range of corn hybrids grown throughout Virginia over two years. We expect that both modified models can be used for strategic research and management decisions in mid-Atlantic corn production.Master of Science
8
Traynor, Mary. "Root growth in drying soil : a role for ABA?" Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322894.
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Siqueira, Rafael Telles Tenorio de. "Characterizing nitrogen deficiency of maize at early growth stages using fluorescence measurements". Thesis, Colorado State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10138898.
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Among all nutrients that are important for crop production, nitrogen (N) is one of the least efficiently utilized, mainly due to its high mobility in soil. The possibility of using crop sensing in real-time to detect variability in N deficiency within a field has the potential to enhance N efficiency, increase crop yield, and reduce potential environmental risks and crop production costs. Potassium (K), another important crop nutrient, can also lead to higher yield when applied in the right amount and manner. Real-time fluoro-sensing is a new technology for crop sensing and studies have shown that it could enable variable rate nutrient management for precision agriculture practices. The objective of this study was (1) to evaluate if fluorescence sensing can detect variability of N and K in crop canopy at early growth stages of maize (prior to V6 crop growth stage) under controlled condition (greenhouse), (2) to evaluate the effect of different fertilization dosages of N over the plant growth, and (3) to verify if induced fluorescence can detect in situ N variability at early growth stages of maize. Research was conducted in two stages, first in a greenhouse condition and later in field spread over three site-years. The greenhouse research was conduct in year 2011 and plants were grown in plant-pots with silica sand and supplied with modified Hoagland solution with different rates of N and K. Field trials were conducted in year 2012 and 2013 in northern Colorado. For the greenhouse study, data collected via fluorescence sensor (Multiplex®3) were analyzed using ANOVA and Tukey’s HSD to test significant differences among treatments in each experiment. For the N experiment, regression analysis between the seven fluorescence indices and N uptake was performed for the 12 days of data acquisition at five different growth stages (i.e. 2-leaf to 6-leaf growth stages) and coefficient of determination was used to identify the best fluorescence indices to detect N status. Also, root mean square error (RMSE) was used to test the precision of the estimates for each index. Results of this study indicated that all fluorescence indices were able to detect N variability in maize canopy prior to V2 growth stage. However, the fluorescence indices failed to identify K deficiency as the maize plants with K treatments showed small variability at early crop growth stages. For the field study, two site-years had 5 N rate treatments applied as UAN 32% (urea ammonium nitrate; 32-0-0), while one site-year had 6 N treatments applied pre-planting. Sensors used in this study were the Multiplex®3 for fluorescence sensing and the GreenSeeker® for reflectance sensing (NDVI). Sensor measurements were correlated with aboveground biomass, N content, and N uptake measured at two growth stages (V6 and V9 maize growth stage). The aboveground biomass, N content, N uptake, yield, and sensors readings were analyzed using ANOVA and Tukey’s HSD to test significant differences among the N treatments. Also, a regression tree between N uptake and the fluorescence indices was fitted along with the coefficient of determination (R2 ). The N rates had no effect on aboveground biomass, N content and N uptake (for both sampled growth stages). Under field conditions, fluorescence indices failed to detect N variability in maize at early growth stages for all three site-years. This finding may require further investigation, as for most of the N treatment plots, maize plants had sufficient N levels and another biotic or abiotic stress may be responsible for unexplained differences in N variability as measured by fluorescence sensor. Contrasting findings under greenhouse conditions versus field conditions limit the application of fluorosensing sensor. Further field studies are needed to evaluate the potential of this sensor for detecting N variability in situ.
10
Yang, Rick L. "Tissue specificity of signal transmission and differential growth during maize root gravitropism". Connect to resource, 1992. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1244222463.
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Ali, Rao Sajjad. "The potential for breeding Zea mays (L.) for saline conditions". Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387451.
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Bello, Zaid Adekunle. "Effect of soil nutrient status on growth, reproductive development and yield components of maize in a long term field trial". Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/28237.
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The research objectives were to examine the effect of soil nutrient status on the growth rate, reproductive development, yield components and yield of maize in a long-term trial. On the Experimental Farm of the University of Pretoria, treatments selected for this investigation were O (control), PK (nitrogen deficient), NK (phosphorus deficient), NP (potassium deficient), NPK (balanced nutrient), and WNPKM (mixture of balanced nutrient and manure). Growth analyses were performed, embryonic tassel and ear development recorded, developmental stages and rate of tasseling and silking were monitored while yield components were determined at maturity. The balanced nutrient treatment (WNPKM) plants showed the highest growth rate and produced the highest biomass while the P and K deficient treatments resulted in low growth rates and low biomass. The PK and NPK treatments were intermediate in terms of growth rate and biomass production. The WNPKM, NPK and PK treatments exhibited a high net assimilation rate (NAR) and crop growth rate (CGR), illustrating that an adequate supply of N, P and K is required for high growth rate and biomass production. Plants in the WNPKM plots exhibited early tassel initiation and ear differentiation and larger reproductive organs. Reproductive development in the PK treatment was ahead of those of the NP and NPK treatments. Nutrient stress delayed initiation and differentiation resulting in smaller reproductive organs. A linear relationship was found between leaf area indices (LAI) and the sizes of the reproductive structures. The higher the LAI the larger the size of the reproductive structures. Emergence of inflorescences was timely in plants exposed to the balanced nutrient but delayed in nutrient deficient treatments. Grain yield and the yield components were positively affected by the balanced nutrient treatment while the nutrient stress treatments reduced the yield. Copyright 2008, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bello, ZA 2008, Effect of soil nutrient status on growth, reproductive development and yield components of maize in a long term field trial, MSc(Agric) dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02122009-105701 / > E1251/gmDissertation (MSc(Agric))--University of Pretoria, 2008.
Plant Production and Soil Science
unrestricted
13
Macharia, J. N. M. "Growth and photosynthesis of maize (Zea mays L.) in sub-optimal environments with particular reference to Britain and Kenya". Thesis, University of Essex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234197.
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Hugo, Elbé. "Growth responses, competitiveness and control of Digitaria nuda (Schumach.) in maize (Zea mays)". Thesis, University of Pretoria, 2014. http://hdl.handle.net/2263/43354.
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Digitaria species infestation levels have recently increased in South Africa due to the
prevailing misconception amongst producers and herbicide agents that acetanilide
herbicides will control all Digitaria spp. equally effective, irrespective of species differences.
Since 2008 a relatively unknown Digitaria spp was noticed in maize fields and was positively
identified as D. nuda (naked crabgrass). Research on naked crabgrass world-wide is limited;
it has been reported to be of importance in sugarcane in Brazil and is considered as a
serious grass weed in West Africa. Growth chamber trials were conducted to elucidate the
germination characteristics of naked crabgrass. Germination of fresh naked crabgrass seed
was less than 20%. Pre-treatment of fresh seed, by means of soaking seed for 24 h in
distilled water, increased germination to 99%. Stored seed (1-yr old) germinated best (100%)
in a 0.2 M KNO3 solution. Naked crabgrass germinated best at constant temperature greater
than 25 °C and at fluctuating regimens of 30/15 °C, with alternating light/dark conditions.
Naked crabgrass emerged faster and total seedling emergence was 20% higher on clay soil.
Above-ground biomass was 5.0 g per plant on clay soil compared to 2.3 g on sandy soil.
Seedling emergence was reduced by 27% after burial at a depth of 1 cm and only 5% seeds
emerged at a depth of 6 cm. In a replacement series glasshouse trial naked crabgrass was
more aggressive with regard to root mass (AI=0.3) and large crabgrass (D. sanguinalis) with
regard to shoot mass (AI=0.04). Naked crabgrass was more competitive in a wet soil profile
(CR=1.88) and large crabgrass in a dry soil profile (CR=2.02). Both grass weeds are making
similar demands on the available resources (RYT=1). The competition effect of both naked
and large crabgrass was determined in glasshouse trials in two soil types at different
watering regimens. A negative linear relationship was recorded between grass density and
maize plant height, shoot- and kernel weight. Estimated yield loss of maize varied between
29 and 76% and was described by the hyperbolic equation of Cousens (1985). Large
crabgrass had a higher damage coefficient (4.1 on sandy soil) compared to naked crabgrass
(3.1 on clay soil). A critical period of weed control was established in field trials for naked crabgrass. The beginning of the critical period of weed control when a 10% yield loss is
estimated varied between the two and six leaf stage of maize, ending at the twelve leaf
stage or two weeks after tasseling, indicating a need for season-long control of naked
crabgrass. Yield loss of maize in the field trials ranged between 28 and 82% in the seasonlong
weedy control treatments. In field and glasshouse trials the efficacy of naked crabgrass
control was evaluated with different herbicides registered on maize. Naked crabgrass is
more tolerant to acetochlor and s-metolachlor and started to emerge two weeks after
applications. Large crabgrass is still effectively controlled by these herbicides. More than
85% of naked crabgrass was controlled when PRE applications of acetanilide herbicides
were followed by triketone herbicides. Indiscriminate identification of all crabgrass species as
“large crabgrass” can cause a shift from large crabgrass to naked crabgrass since the latter
is more difficult to control. Extrapolation of characteristics and factors affecting germination
and growth between similar species is perilous and should be verified. Results of this study
proved that both grass weeds are severe competitors of maize, causing significant yield
losses, but species specific characteristics could be distinguished and will improve decision
making processes significantly to control naked crabgrass effectively in maize.Thesis (PhD)--University of Pretoria, 2014.
lk2014
Plant Production and Soil Science
PhD
Unrestricted
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BEN, HASSINE MORTADHA. "GROWTH, NITROGEN UPTAKE AND MAIZE NITROGEN RECOVERY OF COVER CROPS IN CONSERVATION AGRICULTURE". Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/702471.
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Planting winter cover crops has several benefits compared to keeping the soil bare. The choice of the cover crop species and sowing date is crucial to have the best cover crops establishment and weed suppression. The seeds germination of cover crops is affected by the sowing date with a preference of early sowing. However, the appropriate date of cover crops sowing is not known. Also, cover crops nitrogen dynamics is variable among species. In a conservation agriculture context, we conducted two field experiments in Northern Italy and one laboratory experiment under controlled conditions of temperature and soil moisture. The objectives were to (i) assess the growth and nitrogen uptake of five pure winter cover crops (black oat, Avena strigosa Schreb.; cereal rye, Secale cereale. L.; white mustard, Sinapis alba L.; Egyptian clover Trifolium alexandrinum L.; and hairy vetch, Viccia villosa Roth) as influenced by plant species from three botanical families and two sowing dates (SD1 and SD2), (ii) assess the effect of cover crops presence/absence (bare soil) on weed suppression and maize productivity, (iii) estimate and assess the cover crops contribution to the following main crop (maize) in terms of nitrogen recovery and immediate availability, (iv) establish the course of nitrogen mineralization from pure cover crops in laboratory incubation conditions and (v) assess the effect of three managements of winter-hardy cover crops termination methods and control of weed in maize (chemical vs. mechanical) on maize productivity. The field experiments were carried out in Orzinuovi, Brescia, Italy. Relevant differences in cover crops growth were observed among species, with white mustard SD1 having the highest biomass in November (5.3 and 3.2 t ha-1, respectively for the first and the second year) and Egyptian clover the lowest (less than 1 t ha-1). Also, we demonstrated that hairy vetch SD1 had the highest nitrogen uptake in November (114 kg N ha-1). The presence of cover crops reduced weed infestation compared to a bare soil. Sowing cover crops at end of August, instead of mid-September, had a positive effect on production, establishment, nitrogen uptake, and weed suppression. Maize yield following cover crops was not affected by the cover crop sowing dates and species during the two years of experiment. The maize nitrogen recovery was variable within years; the highest recovery was for maize following hairy vetch SD2 (+67%). The importance of sowing cover crops was demonstrated by the higher nitrogen recovery of maize following cover crops compared to maize following no cover crop treatment. In a laboratory incubation experiment of 84 days, cover crop shoots were collected from cover crops grown in the field, mixed with soil and kept under controlled temperature of 20 °C and soil moisture of 100% field capacity. We demonstrated differences in nitrogen mineralization among the five pure cover crops and weed shoots with hairy vetch, collected in March (C/N ratio of 10.1), having the highest and immediate net nitrogen mineralization from the beginning of incubation until 84 days after start of incubation. Black oat collected in March (C/N ratio of 19.8), had also an immediate net nitrogen mineralization during the whole incubation period but at a lower rate compared to hairy vetch. Egyptian clover collected in November (C/N ratio of 11.4), started nitrogen mineralization 7 days after start of incubation. White mustard collected in November (C/N ratio of 17.7), had a low rate of nitrogen mineralization. Shoots of weed, cereal rye, white mustard and black oat collected in March immobilized nitrogen during the whole incubation period at different rates; cereal rye had the highest rate of immobilization and was not able to start nitrogen mineralization 84 days after start of incubation. In the second field experiment our results indicated that a “post-glyphosate” scenario (mechanical termination of cover crops and chemical control of weed in maize) is the best management to produce the highest yield of maize compared to a “business-as-usual” management (chemical termination of cover crops and weed control in maize) and “organic” management (mechanical termination of cover crops and weed control in maize).
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Saropulos, Athanassios S. "Chilling-induced physiological dysfunction in leaves of Zea mays L. and Capsicum annuum L. seedlings". Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283693.
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Gurney, Anita L. "Growth and photosynthetic responses of maize and sorghum to the parasitic weed Striga hermonthica". Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267174.
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Cho, In-jeong. "Function of abscisic acid in maintenance of maize primary root growth under water deficit". Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4459.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file plus two media files. Title from title screen of research.pdf file (viewed on May 1, 2009) Vita. Includes bibliographical references.
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Shonjani, Saeed. "Salt sensitivity of rice, maize, sugar beet, and cotton during germination and early vegetative growth". [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965829588.
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Magallón, Servin Paola. "Development of an inoculant of phosphate rock-solubilizing bacteria to improve maize growth and nutrition". Thesis, Université Laval, 2014. http://www.theses.ulaval.ca/2014/30283/30283.pdf.
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L'utilisation directe de roche phosphatée (RP) est une alternative viable pour remplacer les coûteux fertilisants chimiques dans les pays en voie de développement. L'utilisation de bactéries solubilisatrices de RP (BSRP) est un bon moyen pour augmenter la réactivité de la RP. L'objectif principal de ce travail a été d'obtenir des isolats provenant de la mycorhizosphère du maïs possédant une grande capacité de solubilisation de RP, compatibles avec la mycorhize arbusculaire (MA) et présentant des traits associés aux rhizobactéries favorisant la croissance de plantes (RFCP) pour le développement d'un inoculant bactérien pour le maïs.À partir de 118 isolats obtenus de maïs biologique cultivé au Québec, huit BSRP ont été identifiés comme Asaia lannaensis Vb1, Pseudomonas sp. Vr14, Rahnella aquatilis (Vr7, Vr13 et Sr24) et Pantoea agglomerans (Vr9, Ve16 et Vr25). En milieu liquide, les isolats ont dissous le P des RP selon leur réactivité (Gafsa>Tilemsi>Maroc). La solubilisation des RP s'est effectuée par la production d'acides organiques (OA) et l'abaissement du pH. Les meilleures BSRP de chaque groupe: (A. lannaensis Vb1, Pseudomonas sp. Vr14, R. aquatilis Sr24 et P. agglomerans Vr25) ont été sélectionnées selon leur capacité élevée de solubilisation de la RP et de leur production d'acide indolacétique (AIA) et de sidérophores. L’importance des biofilms formés, ainsi que le degré de motilité variaient selon les isolats et tous étaient compatibles avec le Glomus irregulare (Gi). L’étude de la colonisation des racines montre que R. aquatilis Sr24 et P. agglomerans Vr25 ont été les meilleurs colonisateurs. Lors des expériences en serre, certains mélanges contenant R. aquatilis Sr24, P. agglomerans Vr25 et Gi, ont amélioré la biomasse, l'absorption des nutriments et la colonisation de la plante en association avec un champignon mycorhizien indigène du maïs cultivé dans un sol non stérile et fertilisé avec la RP Marocaine. Nous attribuons ces résultats à leur capacité d'être de bonnes BSRP colonisatrices des racines. Elles sont aussi compatibles avec Gi et sont capables de produire de l'AIA et des sidérophores. Cette thèse démontre donc le potentiel d'utilisation de BSRP comme inoculant afin d'améliorer l'efficacité de l'utilisation directe de RP comme fertilisant phosphaté pour l'agriculture durable du maïs.Phosphorous is the second most important nutrient for plant growth, but its availability is often reduced. Therefore high quantities of expensive soluble P-fertilizers are added to soil. Direct use of phosphate rock (PR) is an alternative to chemical P-fertilizers in developing countries and for sustainable agriculture. In order to increase PR reactivity the use of phosphate rock-solubilizing bacteria (PRSB) is a good alternative. Therefore, the main objective of this work was to obtain mycorrhizosphere-competent PRSB presenting other PGPR-associated traits to be used for the development of an inoculant to improve maize growth and P nutrition. Out of 118 isolates obtained from organically grown maize in Quebec, eight PRSB were identified as Asaia lannaensis Vb1, Pseudomonas sp. Vr14, Rahnella aquatilis (Vr7, Vr13 and Sr24) and Pantoea agglomerans (Vr9, Ve16 and Vr25). All isolates were able to mobilize P from different sparingly soluble P sources in solid media. In liquid medium the isolates were able to solubilize P from PRs according to their reactivity (Gafsa>Tilemsi>Morocco). PRs were solubilized by the production of organic acids (OAs) and by lowering the pH. The best PRSB from each group (A. lannaensis Vb1, Pseudomonas sp. Vr14, R. aquatilis Sr24 and P.3 agglomerans Vr25) were selected based on their high PR solubilization, and capacity for indolacetic acid (IAA) and siderophore production. These four isolates presented different biofilm formation and motility capacities and were compatible with Glomus irregulare (Gi). A root colonization study showed that R. aquatilis Sr24 and P. agglomerans Vr25 were the best root colonizers. Vr25 was very competitive when used with other PRSB. In greenhouse trials, plant inoculation with R. aquatilis Sr24 and P. agglomerans Vr25 in addition to Gi, increased the biomass, nutrient uptake in non-sterile soil amended with Moroccan PR (MPR). We attribute these results not only to their PR-solubilizing capacity but also for their ability to be good PRSB, competitive root colonizers, compatible with Gi and to produce IAA and siderophores. This thesis shows that PRSB with AM fungi can be used as inoculants to improve the efficiency of the direct use of PR as P fertilizer for sustainable maize production.
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Kanton, Roger Adamu Lure. "Growth, yield components and resource use by morphologically contrasting maize-pea sole crops and intercrops". Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408994.
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Magallón-Servin, Paola y Paola Magallón-Servin. "Development of an inoculant of phosphate rock-solubilizing bacteria to improve maize growth and nutrition". Doctoral thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/24965.
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L'utilisation directe de roche phosphatée (RP) est une alternative viable pour remplacer les coûteux fertilisants chimiques dans les pays en voie de développement. L'utilisation de bactéries solubilisatrices de RP (BSRP) est un bon moyen pour augmenter la réactivité de la RP. L'objectif principal de ce travail a été d'obtenir des isolats provenant de la mycorhizosphère du maïs possédant une grande capacité de solubilisation de RP, compatibles avec la mycorhize arbusculaire (MA) et présentant des traits associés aux rhizobactéries favorisant la croissance de plantes (RFCP) pour le développement d'un inoculant bactérien pour le maïs.À partir de 118 isolats obtenus de maïs biologique cultivé au Québec, huit BSRP ont été identifiés comme Asaia lannaensis Vb1, Pseudomonas sp. Vr14, Rahnella aquatilis (Vr7, Vr13 et Sr24) et Pantoea agglomerans (Vr9, Ve16 et Vr25). En milieu liquide, les isolats ont dissous le P des RP selon leur réactivité (Gafsa> Tilemsi> Maroc). La solubilisation des RP s'est effectuée par la production d'acides organiques (OA) et l'abaissement du pH. Les meilleures BSRP de chaque groupe: (A. lannaensis Vb1, Pseudomonas sp. Vr14, R. aquatilis Sr24 et P. agglomerans Vr25) ont été sélectionnées selon leur capacité élevée de solubilisation de la RP et de leur production d'acide indolacétique (AIA) et de sidérophores. L’importance des biofilms formés, ainsi que le degré de motilité variaient selon les isolats et tous étaient compatibles avec le Glomus irregulare (Gi). L’étude de la colonisation des racines montre que R. aquatilis Sr24 et P. agglomerans Vr25 ont été les meilleurs colonisateurs. Lors des expériences en serre, certains mélanges contenant R. aquatilis Sr24, P. agglomerans Vr25 et Gi, ont amélioré la biomasse, l'absorption des nutriments et la colonisation de la plante en association avec un champignon mycorhizien indigène du maïs cultivé dans un sol non stérile et fertilisé avec la RP Marocaine. Nous attribuons ces résultats à leur capacité d'être de bonnes BSRP colonisatrices des racines. Elles sont aussi compatibles avec Gi et sont capables de produire de l'AIA et des sidérophores. Cette thèse démontre donc le potentiel d'utilisation de BSRP comme inoculant afin d'améliorer l'efficacité de l'utilisation directe de RP comme fertilisant phosphaté pour l'agriculture durable du maïs.L'utilisation directe de roche phosphatée (RP) est une alternative viable pour remplacer les coûteux fertilisants chimiques dans les pays en voie de développement. L'utilisation de bactéries solubilisatrices de RP (BSRP) est un bon moyen pour augmenter la réactivité de la RP. L'objectif principal de ce travail a été d'obtenir des isolats provenant de la mycorhizosphère du maïs possédant une grande capacité de solubilisation de RP, compatibles avec la mycorhize arbusculaire (MA) et présentant des traits associés aux rhizobactéries favorisant la croissance de plantes (RFCP) pour le développement d'un inoculant bactérien pour le maïs.À partir de 118 isolats obtenus de maïs biologique cultivé au Québec, huit BSRP ont été identifiés comme Asaia lannaensis Vb1, Pseudomonas sp. Vr14, Rahnella aquatilis (Vr7, Vr13 et Sr24) et Pantoea agglomerans (Vr9, Ve16 et Vr25). En milieu liquide, les isolats ont dissous le P des RP selon leur réactivité (Gafsa> Tilemsi> Maroc). La solubilisation des RP s'est effectuée par la production d'acides organiques (OA) et l'abaissement du pH. Les meilleures BSRP de chaque groupe: (A. lannaensis Vb1, Pseudomonas sp. Vr14, R. aquatilis Sr24 et P. agglomerans Vr25) ont été sélectionnées selon leur capacité élevée de solubilisation de la RP et de leur production d'acide indolacétique (AIA) et de sidérophores. L’importance des biofilms formés, ainsi que le degré de motilité variaient selon les isolats et tous étaient compatibles avec le Glomus irregulare (Gi). L’étude de la colonisation des racines montre que R. aquatilis Sr24 et P. agglomerans Vr25 ont été les meilleurs colonisateurs. Lors des expériences en serre, certains mélanges contenant R. aquatilis Sr24, P. agglomerans Vr25 et Gi, ont amélioré la biomasse, l'absorption des nutriments et la colonisation de la plante en association avec un champignon mycorhizien indigène du maïs cultivé dans un sol non stérile et fertilisé avec la RP Marocaine. Nous attribuons ces résultats à leur capacité d'être de bonnes BSRP colonisatrices des racines. Elles sont aussi compatibles avec Gi et sont capables de produire de l'AIA et des sidérophores. Cette thèse démontre donc le potentiel d'utilisation de BSRP comme inoculant afin d'améliorer l'efficacité de l'utilisation directe de RP comme fertilisant phosphaté pour l'agriculture durable du maïs.
Phosphorous is the second most important nutrient for plant growth, but its availability is often reduced. Therefore high quantities of expensive soluble P-fertilizers are added to soil. Direct use of phosphate rock (PR) is an alternative to chemical P-fertilizers in developing countries and for sustainable agriculture. In order to increase PR reactivity the use of phosphate rock-solubilizing bacteria (PRSB) is a good alternative. Therefore, the main objective of this work was to obtain mycorrhizosphere-competent PRSB presenting other PGPR-associated traits to be used for the development of an inoculant to improve maize growth and P nutrition. Out of 118 isolates obtained from organically grown maize in Quebec, eight PRSB were identified as Asaia lannaensis Vb1, Pseudomonas sp. Vr14, Rahnella aquatilis (Vr7, Vr13 and Sr24) and Pantoea agglomerans (Vr9, Ve16 and Vr25). All isolates were able to mobilize P from different sparingly soluble P sources in solid media. In liquid medium the isolates were able to solubilize P from PRs according to their reactivity (Gafsa> Tilemsi> Morocco). PRs were solubilized by the production of organic acids (OAs) and by lowering the pH. The best PRSB from each group (A. lannaensis Vb1, Pseudomonas sp. Vr14, R. aquatilis Sr24 and P.3 agglomerans Vr25) were selected based on their high PR solubilization, and capacity for indolacetic acid (IAA) and siderophore production. These four isolates presented different biofilm formation and motility capacities and were compatible with Glomus irregulare (Gi). A root colonization study showed that R. aquatilis Sr24 and P. agglomerans Vr25 were the best root colonizers. Vr25 was very competitive when used with other PRSB. In greenhouse trials, plant inoculation with R. aquatilis Sr24 and P. agglomerans Vr25 in addition to Gi, increased the biomass, nutrient uptake in non-sterile soil amended with Moroccan PR (MPR). We attribute these results not only to their PR-solubilizing capacity but also for their ability to be good PRSB, competitive root colonizers, compatible with Gi and to produce IAA and siderophores. This thesis shows that PRSB with AM fungi can be used as inoculants to improve the efficiency of the direct use of PR as P fertilizer for sustainable maize production.
Phosphorous is the second most important nutrient for plant growth, but its availability is often reduced. Therefore high quantities of expensive soluble P-fertilizers are added to soil. Direct use of phosphate rock (PR) is an alternative to chemical P-fertilizers in developing countries and for sustainable agriculture. In order to increase PR reactivity the use of phosphate rock-solubilizing bacteria (PRSB) is a good alternative. Therefore, the main objective of this work was to obtain mycorrhizosphere-competent PRSB presenting other PGPR-associated traits to be used for the development of an inoculant to improve maize growth and P nutrition. Out of 118 isolates obtained from organically grown maize in Quebec, eight PRSB were identified as Asaia lannaensis Vb1, Pseudomonas sp. Vr14, Rahnella aquatilis (Vr7, Vr13 and Sr24) and Pantoea agglomerans (Vr9, Ve16 and Vr25). All isolates were able to mobilize P from different sparingly soluble P sources in solid media. In liquid medium the isolates were able to solubilize P from PRs according to their reactivity (Gafsa> Tilemsi> Morocco). PRs were solubilized by the production of organic acids (OAs) and by lowering the pH. The best PRSB from each group (A. lannaensis Vb1, Pseudomonas sp. Vr14, R. aquatilis Sr24 and P.3 agglomerans Vr25) were selected based on their high PR solubilization, and capacity for indolacetic acid (IAA) and siderophore production. These four isolates presented different biofilm formation and motility capacities and were compatible with Glomus irregulare (Gi). A root colonization study showed that R. aquatilis Sr24 and P. agglomerans Vr25 were the best root colonizers. Vr25 was very competitive when used with other PRSB. In greenhouse trials, plant inoculation with R. aquatilis Sr24 and P. agglomerans Vr25 in addition to Gi, increased the biomass, nutrient uptake in non-sterile soil amended with Moroccan PR (MPR). We attribute these results not only to their PR-solubilizing capacity but also for their ability to be good PRSB, competitive root colonizers, compatible with Gi and to produce IAA and siderophores. This thesis shows that PRSB with AM fungi can be used as inoculants to improve the efficiency of the direct use of PR as P fertilizer for sustainable maize production.
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Wu, Yajun. "Cell wall proteins and growth maintenance of the maize primary root at low water potentials /". free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9720531.
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Mampana, Reedah Makgwadi. "Cropping system effects on soil water, soil temperature and dryland maize productivity". Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/43165.
Texto completoResumen
Improved soil water conservation has become an important subject in semi-arid areas due to low and erratic rainfall which is often combined with higher temperatures to provide unsuitable conditions for successful crop productivity. Dryland agriculture remains vulnerable to yield losses in these areas. This calls for implementation of conservation agricultural practices that would improve dryland maize productivity. An on-station field trial was started in 2007 at Zeekoegat experimental farm (24 kilometers north of Pretoria), to establish the effect of different conservation agriculture practices on soil and plant properties. The experimental lay-out was a split-plot randomized complete block design, replicated three times, with each replicate split into two tillage systems (whole plots) and then each whole plot (reduced tillage (RT) and conventional tillage (CT)) was subdivided into 12 treatments (two fertilizer levels x 6 cropping patterns). The present study explored the impacts of different tillage practices, cropping patterns and fertilization levels on soil water content, soil temperature and dryland maize productivity during the 2010/11 and 2011/12 growing seasons. To improve the quality of soil water content (SWC) data, the effect of correction for concretions on soil bulk density and the relationship between volumetric soil water content (SWC) vs neutron water meter (NWM) count ratios was also investigated. Corrections for concretions on soil bulk density did not improve NWM calibrations in this study. In all seasons, significantly higher mean SWC was found under RT treatment than in CT at all depths except at 0-300 mm. For example, during the 2010/11 growing season, SWC under RT was 1.32 % and 1.10 % higher than CT for the 300 – 1350 mm and 0 – 1350 mm soil profiles, respectively. The mean weekly SWC was consistently higher for RT throughout both the growing seasons. Significantly higher SWC was also found under monoculture at all soil depths (except at 0-300 mm during 2011/12) compared to treatments under intercropping. For example, during 2010/11, at 0-300mm, SWC under maize monoculture was 1.72 % higher than under intercropping. The maximum and minimum soil temperatures were significantly higher at 100 and 400 mm soil depths under CT than under RT during 2010/11. During 2011/12, significantly higher minimum soil temperatures at 100 mm depth and lower temperature differences (maximum – minimum soil temperatures) at 400 mm depth were observed under intercropping. Despite the higher SWC and reduced soil temperature under RT, the maize seeds emergence rate was lower and plant stand was reduced. This is attributed to other factors associated with RT systems such as increased soil penetration resistance which often leads to poor root development. The lower soil temperatures under RT were generally within the range that would not be expected to inhibit growth and uptake of nutrients. Slower growth under RT resulted in lower biomass and grain yield. Plants that received high fertilizer rates grew more vigorously than plants under lower fertilizer levels when water was not a limiting factor, but produced lower grain yield due to water shortage in March, especially in 2011/12. The harvest index was therefore lower for treatments that received high fertilizer levels. Maize biomass under monoculture x low fertilizer level was significantly lower compared to other fertilizer x cropping pattern treatments. Maize plant growth under intercropping was improved throughout the seasons, which led to significantly higher grain yield than under maize monoculture. It is therefore recommended that farmers in dryland areas take the advantage of intercropping maize with legumes to obtain higher maize productivity. Further research should focus on investigating the possibility of roots restrictions occurring under RT conditions and under various environmental and soil conditions.Dissertation (MScAgric)--University of Pretoria, 2014.
lk2014
Plant Production and Soil Science
MScAgric
Unrestricted
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Ashraf, Zakira Naureen. "Identification of rhizobacteria from rice and maize for plant growth promotion and biological control of rice diseases". Thesis, Lancaster University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578244.
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The scope of this study was the selection of bacterial strains from rice and maize and evaluation of their potential for plant growth promotion and biological control of rice diseases. 103 bacterial strains isolated from roots, rhizosphere and soil of rice and maize were assayed for production of siderophores, antibiotics, hydrolytic enzymes and HCN. From these, 33 strains were found to produce siderophores, eight were capable of producing diffusible antibiotics and four produced volatile antibiotics, while only one strain was found to produce HCN. Dual culture antagonistic assays were used to select strains capable of inhibiting growth of three major rice pathogens, Xanthomonas oryzae pv. oryzae (bacterial blight), Rhizoctonia solani (sheath blight) and Magnaporthe grisea (rice blast). When inoculated into soils, a number of strains suppressed the incidence of rice blast and sheath blight diseases in two different rice varieties. A strong correlation between siderophore production and in vitro antagonism was found, which extended to biocontrol assays for rice blast disease in the variety Super Basmati, but not Azucena, suggesting that bacterial strains use different mechanisms in suppressing the same pathogen in different rice varieties. As there was no direct contact between the pathogen and bacterial strains, the proposed mechanism for disease suppreSSIOn is induced systemic resistance (ISR). Gene expression analysis for sheath blight experiments confirmed the enhanced induction of chitinase IIb and the peroxidase P0X22.3 by selected bacterial strains. Selected bacterial strains from rice were also observed to enhance plant growth and yield, and this may be related to their ability to fix nitrogen (detected by acetylene reduction assay), solubilize phosphates and/or produce auxin. This study led to the isolation, selection and evaluation of potentially useful bacterial strains from rice and maize that were genetically diverse and persistently abundant in the rhizosphere and can be further utilized for integrated pest management of rice. Moreover, as these strains are . also capable of improving plant health and enhancing grain yield, they could be further utilized either individually or in consortia for integrated nutrient management of rice and maize.
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Otukpa, Faith Obiye. "Metabolomic analysis of maize (Zea mays  L.) seedlings treated with selected plant growth promoting rhizobacteria". Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/77875.
Texto completoResumen
Global food production has significantly increased mainly due to the use of high-yield crop varieties, fertilisers, fungicides and pesticides, and improved irrigation methods. Despite the increase in production, there has been a significant cost to the environment in the form of pollution, and to farmers in the form of rising fertiliser and pesticide costs. The impacts on the environment include but are not limited to groundwater contamination, declining soil health and increased pest and pathogen resistance, all which increase the financial cost to farmers. To reverse or rather salvage the situation, more sustainable agricultural practices need to be employed that will maintain high productivity with little to no damage to the environment, and will reduce agrochemical use, thus, reducing the financial strain on farmers. A potential solution would be to exploit soil dwelling rhizospheric microorganisms to improve plant growth with little to no application of agrochemicals.
The rhizosphere refers to the region of soil directly influenced by plant roots and is home to microorganisms known as plant growth promoting rhizobacteria (PGPR). These PGPR have been found to stimulate plant growth via numerous mechanisms, which directly affect the plant metabolome and in turn translates into observable effects in the plant phenotype. The plant metabolome has been described as the bridge between the genotype and phenotype, thus metabolomics acts as a useful tool to evaluate the contribution of external influences on the plant phenotype based on metabolic changes. The effect of PGPR on the plant metabolome is vital in understanding their mode of action, which will further validate their use in farming.
The overall aim of this project was to assess the effect of selected PGPR strains with known plant growth promoting activity on the metabolic profile of maize seedlings; and to evaluate if these changes in the metabolic profile directly correlate with the observable effects on the growth of the seedlings. To achieve this aim, firstly, the effect of Lysinibacillus sphaericus (T19), Paenibacillus sp. (T29) and Bacillus megaterium (A07) on early maize growth, i.e., the effects on dry root and shoot biomass, leaf chlorophyll content, stem diameter and shoot length, was assessed. Secondly, the effect of single strain PGPR inoculation on the metabolic profile of maize was evaluated. Finally, metabolomics analysis was conducted on the roots and shoots of the maize seedlings inoculated with strains T29 and T19 respectively. Statistical analysis of the metabolomics results was conducted to find significant pathways and discriminating metabolites between the control and inoculated plants. To assess the effects of the PGPR strains on early maize growth, a greenhouse trial was first conducted. Non-invasive techniques were used to measure the growth parameters that could be recorded prior to harvest. Next an untargeted metabolomics approach was used to analyse the metabolome of harvested roots and shoots. Metabolomics data acquisition was achieved using ultra-performance liquid chromatography hyphenated to quadrupole time of flight mass spectrometry detection (UPLC/QTOF-MS). Finally, to evaluate the effect of single strain inoculation on the maize root and shoot metabolome, univariate and multivariate methods were applied.
The results of the greenhouse trial showed a tendency of strains T19 and T29 in stimulating shoot growth and root growth respectively in the maize seedlings. Pathway analysis using results from univariate analysis revealed a number of pathways affected by T19 and T29 in the shoots and roots respectively. Multivariate statistical analysis also showed that the inoculated samples differed from the control samples, albeit with varying trends, which indicates differing metabolic states. Some of the metabolic pathways deemed significant in the inoculated shoots and roots were amino acid, nucleotide metabolism or carbon fixation related. A number of discriminating features were found to be differentially regulated in the inoculated roots and shoots. Overall, the results showed that T19 and T29 inoculation stimulated metabolic responses in maize shoots and roots linked to plant growth and development.Dissertation (MSc)--University of Pretoria, 2019.
Biochemistry
MSc
Unrestricted
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West, Molly E. J. "Stacked Bt Proteins Exacerbate Negative Growth Effects of Juvenile (F. rusticus) Crayfish Fed Corn Diet". Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1555337338986411.
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Van, Tonder Nicolaas Christiaan Petrus. "Seed treatment of maize, sorghum and sunflower with effective micro- organisms". Thesis, [Bloemfontein?] : Central University of Technology, Free State, 2012. http://hdl.handle.net/11462/141.
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Thesis (M. Tech. Agriculture) -- Central University of Technology, Free state, 2012A series of incubation studies and greenhouse experiments were conducted to evaluate the use of EM seed treatments, at different application levels, handling techniques and soil conditions on germination and seedling vigour of selected cultivars of maize, sorghum and sunflower. Two incubation studies were conducted to evaluate the germination and seedling vigour of maize, sorghum and sunflower seeds treated with M-EM from three different suppliers, multiplied at two different ratios (1% and 3%) and diluted at three different levels (0.01%, 0.1% and 1.0%) compared to a control treated with pure water. Results revealed no significant differences under optimum germination conditions, while seedlings under cold stress indicated that M-EM treatments positively affected germination and seedling vigour compared to the control treatments. Two incubation studies were also conducted to evaluate the germination and seedling vigour of maize, sorghum and sunflower seeds treated with M-EM from three different suppliers, multiplied at two different ratios (1% and 3%) and exposed to the influences of irradiation and temperature fluctuation. From the results became clear that the correct storage and handling is essential in optimizing the effect of M-EM on seeds. Even though M-EM was exposed to irradiation and temperature fluctuation, M-EM still had positive effects on germination and seedling vigour. Pot experiments were conducted to determine the effect of EM as seed treatment, at different dilutions, on germination, seedling vigour and dry mass of maize, sorghum and sunflower at different planted depths. Germination were not affected by the M-EM treatment, while shoot length results indicated that seed treated with M-EM could have significant effect on seedling survival. A greater effect was visible on the shoot length of shallow planted seeds, than on deeper planted seeds. From the results no single company, ratio or dilution could be prescribed as paramount. To further investigate the effect of M-EM subjected to the influences of irradiation and temperature fluctuation; maize, sorghum and sunflower seeds were treated with M-EM from three different suppliers, multiplied at two different ratios (1% and 3%) and exposed to the influences of irradiation and temperature fluctuation and planted in soil. M-EM treatments only benefited the germination of deeper planted sorghum seeds compared to the control treatments. The shoot lengths of deeper planted maize and sunflower seed were positively increased by the M-EM treatments while also resulting in significant results for the overall shoot length of sorghum. The third pot study was conducted to determine the influence of EM as a seed treatment on maize, sorghum and sunflower planted in three different soils, namely: sterilized soil, soil treated with M-EM and Fusarium containing soil. Germination and seedling vigour results of the sterilized and M-EM treated soil revealed to be superior to that of the Fusarium containing soil. From the results was concluded that M-EM treatments will probably improve early seedling growth of maize, sorghum and sunflower compared to untreated seed and that M-EM seed treatment and a pre-plant EM soil treatment might assist seeds in unfavourable germination and growth conditions.
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Istain, Brandon. "Isolation and characterization of plant growth promoting endophytic bacteria from Medicago lupulina for enhanced drought tolerance in Maize". University of the Western Cape, 2019. http://hdl.handle.net/11394/7870.
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>Magister Scientiae - MScMaize is one of the major staple foods in many African nations however, this crop is sensitive to environmental stressors. Drought is a major environmental stressor affecting maize production. Due to global warming, drought episodes are expected to increase in duration and frequency. Therefore, it is vital to improve maize drought tolerance thereby increasing food security. Many studies have looked at improving maize drought tolerance through genetic engineering techniques which has shown promising results, nonetheless GMOs have been under scrutiny due to public concerns regarding unknown side effects.
2024-02-24
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Rudolph, Nicole. "Efficacy of selected rhizobacterial isolates for biocontrol of Rhizoctonia solani and growth promotion of maize in South Africa". Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/79181.
Texto completoResumen
Plant growth promoting rhizobacteria (PGPR) are bacteria that colonize the volume of soil surrounding plant roots (known as the rhizosphere) which, when in association with a suitable host plant, promote plant growth. The growing demand for sustainable crop production strategies has placed increasing emphasis on PGPR and their potential use in agriculture. The current study therefore focused on the beneficial effects of PGPR isolates (selected from the PGPR culture collection at the University of Pretoria) on maize (Zea mays L.) and the ability of these isolates to control Rhizoctonia solani Kühn.
The seed quality and vigour of two maize cultivars (PAN 6236B and PAN 6Q-308B) was determined using the standard germination, moisture and various vigour tests. PAN 6Q-308B was found to have lower vigour and was selected for use in the remainder of the tests performed in the study. In a modified seed germination bioassay the percentage germination, seedling mass, shoot and root length of PAN 6Q-308B was increased by selected PGPR isolates. The vigour index (VI) of PAN 6Q-308B was also increased by five isolates (S6, S7, T19, T29 and A32) which were then selected for evaluation in the greenhouse.
In the greenhouse pot trial isolates T19, S7 and T29 gave the most promising results in terms of increasing the dry mass of maize seedlings. These isolates were evaluated in a formulation efficacy trial where they were applied individually and in combination as a soil drench, seed treatment and liquid suspension or powder formulation applied to a pelletised compost carrier. The four most effective treatments at increasing the dry root mass of maize included a soil drench application of either isolate T29 or T19, a soil drench application of the consortium of isolates T19, T29 and S7, and a powder formulation of isolate T29 applied onto the compost pellet carrier.
Isolates A08, A07 and T19 were the most effective at reducing the disease symptoms of R. solani Kühn and increasing dry root matter above that of the R. solani inoculated control in a seedling tray trial. Pot trials were conducted to assess the efficacy of isolates A08, A07 and T19 for control of R. solani, when applied as a seed treatment or soil drench. All three isolates failed to control the pathogen when applied as a seed treatment but a soil drench of isolate T19 was found to be very effective.
A six month shelf-life study was conducted to determine the survival of the PGPR isolates T19, S7 and T29 applied to a novel carrier comprising pelletised composted chicken manure. The isolates were individually applied to the pellets in a liquid or powder form. The latter was found to be the most suitable for supporting the survival of the PGPR isolates up to six months at 25˚C. The study revealed that the viability of the isolates decreased more rapidly at a temperature of 35˚C as opposed to 25˚C, and that the cell numbers of isolate T19 remained the most stable throughout the six months incubation period in comparison with the other isolates.Dissertation (MSc)--University of Pretoria, 2014.
Microbilogy and Plant pathology
MSc
Unrestricted
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Thobatsi, Jacob Thobatsi. "Growth and yield responses of maize (Zea mays L.) and cowpea (Vigna unguiculata L.) in an intercropping system". Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-10122009-184005.
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Pharudi, Joseph Albert. "Effect of mycorrhizal inoculation and phosphorus levels on growth and yield of wheat and maize crops grown on a phosphorus deficient sandy soil". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5135.
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FORMENTI, SILVIA. "FUSARIUM VERTICILLIOIDES IN MAIZE: HOW ABIOTIC AND BIOTIC FACTORS CAN INFLUENCE GROWTH AND FUMONISINS PRODUCTION IN FIELD AND DURING STORAGE". Doctoral thesis, Università Cattolica del Sacro Cuore, 2010. http://hdl.handle.net/10280/773.
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In questa tesi di dottorato sono stati indagati i punti critici legati ai fattori biotici e abiotici che possono influenzare la crescita del fungo Fusarium verticillioides, produttore di fumonisine in mais. le fumonisine sono metaboliti secondari prodotte da funghi appartenenti al genere Fusarium e sono state classificate come possibili cancerogene per l’uomo e per gli animali. Gli argomenti trattati nei vari capitoli sono stati: parametri ecologici che condizionano la crescita e l’accumulo di fumonisine nelle prime fasi post raccolta e durante lo stoccaggio; relazione che intercorre tra aw, umidita’ relativa e tipo di ibrido; controllo con mezzi chimici e biologici in campo e in vitro su F. verticillioides e A. flavus.The aim of this work was to collect missing information about critical point related to abiotic and biotic factors that can influence the growth of Fusarium verticillioides in maize and the consequent production of fumonisins in kernels. Fumonisins are secondary metabolites reported as toxigenic in humans and animals. Issues treated are: variables influencing growth and toxin accumulation during post-harvest and storage; the relationship between aw, relative humidity and type of hybrids; chemical and biological control of F. verticillioides e A. flavus in field and in vitro.
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FORMENTI, SILVIA. "FUSARIUM VERTICILLIOIDES IN MAIZE: HOW ABIOTIC AND BIOTIC FACTORS CAN INFLUENCE GROWTH AND FUMONISINS PRODUCTION IN FIELD AND DURING STORAGE". Doctoral thesis, Università Cattolica del Sacro Cuore, 2010. http://hdl.handle.net/10280/773.
Texto completoResumen
In questa tesi di dottorato sono stati indagati i punti critici legati ai fattori biotici e abiotici che possono influenzare la crescita del fungo Fusarium verticillioides, produttore di fumonisine in mais. le fumonisine sono metaboliti secondari prodotte da funghi appartenenti al genere Fusarium e sono state classificate come possibili cancerogene per l’uomo e per gli animali. Gli argomenti trattati nei vari capitoli sono stati: parametri ecologici che condizionano la crescita e l’accumulo di fumonisine nelle prime fasi post raccolta e durante lo stoccaggio; relazione che intercorre tra aw, umidita’ relativa e tipo di ibrido; controllo con mezzi chimici e biologici in campo e in vitro su F. verticillioides e A. flavus.The aim of this work was to collect missing information about critical point related to abiotic and biotic factors that can influence the growth of Fusarium verticillioides in maize and the consequent production of fumonisins in kernels. Fumonisins are secondary metabolites reported as toxigenic in humans and animals. Issues treated are: variables influencing growth and toxin accumulation during post-harvest and storage; the relationship between aw, relative humidity and type of hybrids; chemical and biological control of F. verticillioides e A. flavus in field and in vitro.
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Atadja, Franklin Komla. "Sustainability Challenges for Maize and Cassava Farmers in Amankwakrom Subdistrict, Ghana". Thesis, Walden University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10243184.
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Agricultural system in Ghana underperformed because of limited financing, which constrained some small-scale maize and cassava farmers. The purpose of this case study design was to explore the methods that some small-scale maize and cassava farmers in Amankwakrom Subdistrict used in obtaining farm financing. Two themes from the literature review were a lack of collateral for small-scale farm financing and the small-scale farmers cooperative associations? role in farm financing. Regional-scale management sustainability index formed the conceptual framework for this study. Data collection included semistructured face-to-face interviews with 8 fluent English speaking small-scale maize and cassava farmers who have obtained farm financing in the previous years. Using the Microsoft Excel and Non-numerical unstructured data indexing and theorizing software program for data analysis method, 3 major themes emerged: the farmer?s membership benefits of working in cooperative associations; farmer?s ability to provide the collateral requirements for the financial institutions; and farmer?s good loan repayment history. The study findings indicated that some small-scale maize and cassava farmers obtained farm loans because they used the cooperative associations as their collateral assets in order to satisfy for the requirements of the financial institutions. Social implications include the potential to guide the small-scale maize and cassava farmers to access farm credits to use in expanding their farm sizes. Expansion in farm sizes may result in more maize and cassava production that can help eliminate hunger and reduce poverty in the Amankwakrom Subdistrict of Ghana.
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Dal, Cortivo Cristian. "Improving root growth in cereals for sustainable cultivation". Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3422686.
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The topic of my PhD research addresses the study on the effects that some new sustainable crop management practices have on enhancing root growth in two globally important cereal crops, wheat and maize.
The structure of the thesis consists of five chapters, corresponding to as many manuscripts already published (2 of 5) or on the way to be published in international scientific journals. In detail, in the first and second chapter were studied the application effects of plant growth promoting microorganisms (PGPMs) on common wheat. The aspects taken under study after their inoculation were: the ability of selected endophityc bacteria and mycorrhizal fungi to colonize and interact with plant organs, the effects on root growth, the promotion of shoot development, the nutitional improvement by increasing N fixation and nutrient availability, the effects on grain yield and other agronomic parameters and finally the environmental significance by evaluating the possibility of cutting chemical fertilization. Microscope investigations revealed an excellent ability of bacteria to adhere to the surface of intact leaves and roots, and to colonize both leaf mesophyll and root vascular tissues in aseptic conditions. Also the mycorrhizal fungus was able to colonize wheat roots efficiently. Bacteria increased the number of root tips and ramifications in sterilized rhizobox soil, regardless of the method of application, and the volumetric root length density in the open field with medium and high N supply, resulting in greater N accumulation. Although the N dose had clear positive effects, no significant variations in grain yield or other agronomic parameters could be ascribed to bacteria inoculation. The arbuscular mycorrhizal fungus allowed remarkable increases in volumetric root length density and root area density at flowering stage at medium and high N fertilization rates in both years, but not a low N rate. While inoculation had a negligible effect on grain yield, which followed a typical N dose-response model, improved uptake of N and other nutrients, particularly P and Zn were recorded at any fertilization rate, although only seldom significant.
Last three chapters aimed at investigating the potential rooting activity on maize plants of the recently market-introduced seed-applied fungicide Sedaxane (Syngenta Crop Protection), a novel succinate dehydrogenase complex II inhibitor (SDHI) against soil-borne pathogenic fungi. Laboratory investigations demonstrated that sedaxane has significant auxin-like and gibberellin-like effects, which induced marked morphological and physiological root changes according to an approximate saturation dose-response model. Sedaxane enhanced leaf and root glutamine synthetase (GS) activity resulting in greater protein accumulation, particularly in the shoot, while glutamate synthase (GOGAT) activity remained almost unchanged. Sedaxane also improved leaf phenylalanine ammonia-lyase (PAL) activity, which may be responsible for the increase in shoot antioxidant activity (phenolic acids), mainly represented by p-coumaric and caffeic acids. Under controlled conditions in a greenhouse we evaluated the root growth enhancement side-effect of sedaxane, regardless of the main protective action against pathogenic fungi, in pot-cultivated maize plants subjected to both biotic and abiotic stress conditions in the early phenological stages. The secondary effect of sedaxane on root growth was detectable both in absence and with high Rhizoctonia solani pressure, but it was more evident in the last situation. Significant enhancements in root biomass, length, area and tips quantity were observed, but also shoot parameters, like leaf chlorophyll content and total biomass. Seed-treated plants highlighted positive responses to both adverse growing conditions performed in the experiments reported in the last chapter, a decreasing soil fertility and a drought stress during early phenological stages. Results showed increased growth of shoot, with higher SPAD values, nutrient uptake and antioxidant activity (phenolic acids), as well as a greatly enhanced root growth than controls. Particularly under severe water stress condition, these parameters did not show marked differences from controls, but plants from treated seeds with fungicide were able to maintain a higher rate of transpiration to a lower value of transpirable water in the soil.Le ricerche condotte durante il mio dottorato hanno riguardato lo studio degli effetti che alcune nuove pratiche sostenibili di gestione colturale hanno nel promuovere la crescita radicale di due colture di importanza globale, frumento e mais. La struttura della tesi consta di cinque capitoli, corrispondenti ad altrettanti articoli già pubblicati (2 di 5) o che stanno per essere pubblicati in riviste scientifiche internazionali. Nel dettaglio, il primo e secondo capitolo riportano lo studio degli effetti dell’applicazione di alcuni microrganismi promotori della crescita (PGPM - plant growth promoting microorganisms) in frumento tenero. Gli aspetti considerati sono stati l’abilità dei batteri endofiti e dei funghi micorrizici selezionati di colonizzare i diversi tessuti vegetali, gli effetti sulla crescita radicale, la promozione dello sviluppo epigeo, l’incremento nutrizionale delle piante dato dalla fissazione azotata e dall’aumento della disponibilità di nutrienti nella rizosfera, gli effetti sulla resa e sugli altri parametri agronomici, la possibilità di ridurre gli apporti azotati da fertilizzanti di sintesi. Le indagini al microscopio hanno evidenziato un’eccellente abilità da parte dei batteri inoculati di aderire alla superficie sia radicale che fogliare delle piante trattate e di colonizzare anche il mesofillo fogliare e i tessuti vascolari delle radici in condizioni di sterilità. I batteri hanno incrementato il numero di apici e ramificazioni radicali delle piante di frumento coltivate in rhizobox con suolo sterilizzato, indipendentemente dal metodo di applicazione (concia del seme o irrorazione fogliare), mentre in pieno campo hanno migliorato la densità di lunghezza radicale con livelli medio-alti di concimazione azotata, determinando anche un incremento dell’accumulo di azoto nei tessuti epigei in confronto alle piante non inoculate. Nessuna variazione significativa della resa o di altri parametri si è invece potuta attribuire all’inoculazione batterica. Anche l’inoculo con i funghi micorrizici ha consentito di incrementare marcatamente la lunghezza e l’area radicale del frumento allo stadio di fioritura con livelli di concimazione azotata medio-elevata, in entrambi gli anni di sperimentazione, mentre nessun effetto è stato osservato impiegando la dose più bassa. Mentre la loro inoculazione ha determinato un effetto del tutto trascurabile sulla resa, che ha seguito il tipico modello di risposta alla dose azotata, un aumento dell’assorbimento di N ed altri nutrienti (P e Zn in particolare) è stato osservato a qualsiasi dose di concimazione adottata, sebbene gli incrementi siano risultati solo in qualche caso significativi. Gli altri tre capitoli riguardano lo studio della potenziale attività biostimolante di sviluppo radicale di un fungicida conciante recentemente introdotto nel mercato contenente Sedaxane® (Syngenta Crop Protection), una nuova sostanza attiva della classe SDHI efficace contro la lotta ad alcuni funghi patogeni terricoli dei cereali. Le analisi condotte in laboratorio hanno dimostrato che il Sedaxane possiede dei significativi effetti auxino- e giberellino-simili, che inducono evidenti modifiche morfologiche e fisiologiche dell’apparato radicale in accordo ad un modello approssimativo di saturazione dose-risposta. Il sedaxane migliora l’attività dell’enzima glutammina sintetasi (GS) sia nelle radici che nelle foglie, risultando in un maggiore accumulo di proteine soprattutto a livello epigeo, mentre l’attività della glutammato sintetasi (GOGAT) è rimasta sostanzialmente invariata. L’applicazione al seme di Sedaxane ha anche incrementato l’attività fogliare della fenilalanina ammonio liasi (PAL), causa del possibile aumento dell’attività antiossidante delle foglie (acidi fenolici), rappresentata principalmente dalla sintesi di acido p-Cumarico e Caffeico. In condizioni controllate in serra è stato valutato l’effetto secondario di accrescimento radicale promosso dal Sedaxane, al di la dell’azione strettamente protettiva nei confronti dei funghi patogeni, in piante di mais coltivate in vaso soggette a stress di tipo biotico e abiotico nei primi stadi fenologici di crescita. L’effetto biostimolante di accrescimento radicale del Sedaxane è stato osservato sia in assenza che in presenza di un’elevata pressione di Rhizoctonia solani, risultando molto più evidente in questa ultima situazione. La biomassa, lunghezza, area e quantità di apici delle radici, ma anche il contenuto di clorofilla nelle foglie e la biomassa epigea, sono aumentati significativamente grazie al trattamento. Le piante sviluppate dai semi trattati con Sedaxane hanno evidenziato risposte positive ad entrambi le condizioni avverse di crescita imposte negli esperimenti descritti nell’ultimo capitolo della tesi, ovvero la mancanza di nutrienti o di acqua disponibile nel terreno durante le prime fasi di crescita. I risultati ottenuti mostrano un incremento della crescita epigea delle piante trattate, con valori di SPAD, assorbimento di nutrienti e attività antiossidante (sintesi di acidi fenolici) maggiori, cosi come un accrescimento radicale superiore rispetto a quello dei controlli in condizioni di stress. In particolare, in una condizione di forte stress idrico, questi parametri non hanno evidenziato differenze sostanziali dai controlli ma le piante sviluppate dai semi trattati sono state in grado di mantenere un tasso di traspirazione maggiore più a lungo, ovvero a livelli elevati nonostante una bassa quantità di acqua disponibile nel terreno.
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Nadeem, Muhammad. "Remobilization of seed phosphorus reserves and exogenous phosphorus uptake during germination and early growth stages of maize (Zea mays L.)". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14439/document.
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Le phosphore (P) est un élément indispensable pour la croissance des plantes. De nombreux travaux montrent des réponses très précoces à une limitation de la disponibilité en P. Pendant la germination et la croissance juvénile, la demande en P des plantules peut être satisfaite par la remobilisation des réserves en P des graines et le prélèvement racinaire. Les objectifs de la thèse sont d’étudier la contribution respective de la remobilisation des réserves en P des graines et du prélèvement racinaire de P à l’alimentation en P des plantules de maïs, et les interactions entre ces deux processus. Différentes expériences ont été conduites pour i) étudier les cinétiques de la remobilisation des réserves en P des graines, ii) identifier précisément le début du prélèvement de P exogène par les racines, iii) quantifier la contribution relative de ces flux à l’alimentation en P de la plantule, iv) comprendre les interactions entre ces flux. Des graines riches et des graines pauvres en P on été cultivées à différents niveaux de disponibilités P exogènes pendant quatre semaines. Le traçage isotopique du P exogène (32P) a été utilisé pour quantifier le flux de prélèvement et calculer le flux de remobilisation du P des graines. Initialement, 86% du P sous forme phytate et 13% du C de la graine est localisé dans le scutellum indépendamment du niveau de richesse en P de la graine. 4 jours après le semis, 98% des phytates des graines sont hydrolysés. La cinétique d’hydrolyse des phytates est indépendante de la richesse en P des graines et de la disponibilité en P dans le milieu. Le P issu de l’hydrolyse des phytates est stocké temporairement dans la graine avant d’être transporté vers les organes en croissance de la plantule. Le prélèvement de P exogène commence dès l’émergence de la radicule (4ième jour) et dépend de la disponibilité en P dans le milieu. L’initiation du prélèvement et son intensité ne dépend pas du flux de remobilisation des réserves en P de la graine. Le P issu de la remobilisation et du prélèvement est distribué dans les mêmes proportions entre les parties ariennes et racinaires. Un bilan de P à l’échelle de la plantule entière et de la graine a permis de mettre en évidence un efflux de P depuis la graine vers l’extérieur pendant la phase d’hydrolyse des phytates. La modélisation des flux de P pendant la germination et la croissance précoce permet de rendre compte des observations sous l’hypothèse d’absence d’interaction entre les flux de remobilisation et de prélèvement de P bien que ces deux processus se chevauchent dans le temps. Nos résultats démontrent l’importance de la disponibilité locale en P dans le milieu pendant les stades précoces indépendamment du niveau de richesse en P des grainesPhosphorus (P) is an essential element for plant growth. Many studies have shown a very early seedling response to the limitation on the availability of P. During germination and early growth, the seedling P demand may be satisfied by the remobilization of seed P reserves and exogenous P uptake by developing roots. The objective of the thesis was to study the relative contribution of remobilization of seed P reserves, the exogenous P uptake by seedling roots and the interaction between these two processes. Various experiments were conducted to i) study the kinetics of the remobilization of seed P reserves, ii) identify precisely the beginning of exogenous P uptake by seedling roots, iii) quantify the relative contribution P fluxes in developing seedlings and iv) the interaction between these two P fluxes. Seeds with low and high P reserves were cultivated at different levels of exogenous P availability for the growth period of four weeks. The exogenous P was labelled with radioactive P (32P) to identify and quantify the P flux in young seedlings coming from exogenous P uptake and seed P reserves remobilization. Initially, 86% of P in the form of phytate and 13% C of seed reserves is localised in scutellum regardless of P initial seed P reserves. Four days after germination, 98% of seed phytate reserves are hydrolyzed. The kinetics of seed phytate hydrolysis was independent of seed P reserves and exogenous P availability. The hydrolyzed forms of phytate were temporarily stored in the seed before being translocated towards newly growing seedling compartments. The exogenous P uptake started soon after the radicle emergence (4th day) and depend mainly on the availability of exogenous P in the growth medium. The beginning of exogenous P uptake and its intensity was not influenced by the seed P reserves remobilization. The proportion of distribution of remobilized seed P reserves and the exogenous P uptake was similar among seedling shoot and roots. The whole seed and seedling P budget showed the significant P losses from germinating seeds by P efflux with the beginning of phytate hydrolysis in seeds. We proposed a model for the seed P remobilization and exogenous P uptake during germination and early growth. Assuming no interaction between seed P reserves remobilization and exogenous P uptake, the simulations were found to be in close agreement with experimental data. Our results showed the importance of exogenous P availability in growth medium during early growth stages regardless of seed P reserves
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Wilson, Glen H. "The regulation of intracellular pH and ammonium in intact rice (Oryza sativa) and Maize (Zea mays) roots : an investigation of the mechanism(s) of NHâ†3 toxicity". Thesis, University of Greenwich, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264710.
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Shahzad, Muhammad [Verfasser]. "Growth-related changes in subcellular ion and protein patterns in maize and field bean leaves under salt stress / Muhammad Shahzad". Kiel : Universitätsbibliothek Kiel, 2012. http://d-nb.info/102114018X/34.
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Nciizah, Adornis Dakarai. "Cattle manure, scalping and soil wetness effects on some physical properties of a hardsetting soil and associated early maize growth". Thesis, University of Fort Hare, 2011. http://hdl.handle.net/10353/349.
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Most soils in the Eastern Cape Province, South Africa are shallow and are low in organic matter. Therefore these soils are structurally fragile and highly susceptible to inherent degradative processes like hardsetting. The objective of this study was to determine the effect of cattle manure, scalping and soil wetness on aggregate stability, penetration resistance and early maize growth in hardsetting soils. Glasshouse and field studies were conducted to determine the effect of cattle manure on aggregate stability and penetration resistance of freshly exposed topsoils by scalping at 0, 10 and 20 cm depths. In the glasshouse cattle manure was applied at 0 and 20 Mg/ha and matric suction was kept at ~ 30 and ~ 400 kPa; contrasting high and low soil wetness. Three soils were put in pots and arranged in a randomized complete block 3 2 2 factorial design. The field study was done at the University of Fort Hare research farm and the treatments were arranged in a split-plot complete randomized design with three replications. Scalping treatment was the main plot whilst the quantity of the cattle manure applied was the sub plot. Cattle manure increased mean weight diameter (MWD) by between 48% and 71% under glasshouse and between 18% and 33% under field conditions, depending on the soil wetting rate. Cattle manure reduced MWD when the soil under field condition was subjected to mechanical shaking. Soil penetration resistance decreased linearly, with increasing soil wetness but it rapidly increased with increase in matric suction up to ~200 kPa and thereafter the rate of increase reduced. In the glasshouse, all treatments had no significant effects on shoot dry weight but low matric suction increased root dry weight by 133%. Interaction of cattle manure and low matric suction reduced shoot length by 6%, shoot fresh weight by 25%, root surface area by 36%, root length by 5% and root fresh weight by 29% compared to the control. In contrast, application of cattle manure and high matric suction increased shoot length by 37%, shoot fresh weight by 136%, root surface area by 159%, root length by 94% and root fresh weight by 119%. In the field, cattle manure application increased root length density and shoot dry matter by 26% and 30% respectively. Cattle manure improved the stability of aggregates of the hardsetting soil under rapid or slow water intake conditions experienced during rainfall or irrigation. However, under field conditions cattle manure acted as a deflocculant and decreased the stability of aggregates when mechanical stress was applied. The effectiveness of cattle manure in improving maize growth in hardsetting soils was determined by matric suction.
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Bello, ZAID Adekunle. "Effect of soil nutrient status on growth, reproductive development and yield components of maize in a long term field trial". Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-02122009-105701.
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Mditshwa, Sithembele. "Estimating maize grain yield from crop growth stages using remote sensing and GIS in the Free State Province, South Africa". Thesis, University of Fort Hare, 2017. http://hdl.handle.net/10353/6016.
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Early yield prediction of a maize crop is important for planning and policy decisions. Many countries, including South Africa use the conventional techniques of data collection for maize crop monitoring and yield estimation which are based on ground-based visits and reports. These methods are subjective, very costly and time consuming. Empirical models have been developed using weather data. These are also associated with a number of problems due to the limited spatial distribution of weather stations. Efforts are being made to improve the accuracy and timeliness of yield prediction methods. With the launching of satellites, satellite data are being used for maize crop monitoring and yield prediction. Many studies have revealed that there is a correlation between remotely sensed data (vegetation indices) and crop yields. The satellite based approaches are less expensive, save time, data acquisition covers large areas and can be used to estimate maize grain yields before harvest. This study applied Landsat 8 satellite based vegetation indices, Normalized Difference Vegetation Index (NDVI), Soil Adjusted Vegetation Index (SAVI) and Moisture Stress Index (MSI) to predict maize crop yield. These vegetation indices were derived at different growth stages. The investigation was carried out in the Kopanong Local Municipality of the Free State Province, South Africa. Ground-based data (actual harvested maize yields) was collected from Department of Agriculture, Forestry and Fisheries (DAFF). Satellite images were acquired from Geoterra Image (Pty) Ltd and weather data was from the South African Weather Service (SAWS). Multilinear regression approaches were used to relate yields to the remotely sensed indices and meteorological data was used during the development of yield estimation models. The results showed that there are significant correlations between remotely sensed vegetation indices and maize grain yield; up to 63 percent maize yield was predicted from vegetation indices. The study also revealed that NDVI and SAVI are better yield predictors at reproductive growth stages of maize and MSI is a better index to estimate maize yield at both vegetative and reproductive growth stages. The results obtained in this study indicated that maize grain yields can be estimated using satellite indices at different maize growth stages.
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Moore, Nicolle Maureen. "Investigating the use of Arbuscular Mycorrhizas and Plant Growth Promoting Bacteria to improve the drought tolerance of maize (Zea mays L.)". Thesis, Rhodes University, 2016. http://hdl.handle.net/10962/54587.
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Maize (Zea mays L.) is a direct staple food crop in Africa and remains an essential component of global food security, with maize crops accounting for over 60% of the total harvested area of annual food crops. Stress caused by drought and high soil salinity limits crop growth and productivity more than any other single environmental factor, with grain yield reductions up to 76% depending on the severity of the drought and the plant growth stage. Arbuscular mycorrhizal (AM) fungi and Plant Growth Promotion Rhizobacteria (PGPR) have previously been shown to improve tolerance of plants to drought stress through a number of chemical and physiological processes. The aim of this investigation was to determine whether mycorrhizal fungi and rhizobacteria adapted to drought and saline conditions and possessing plant growth promoting (PGP) traits were able to stimulate plant growth responses when applied to Zea mays seeds growing under greenhouse conditions Bacterial isolates selected were tolerant to concentrations of NaCl up to 600 mM and maintained 50% growth at low water potentials (-1.44 MPa). They were positive for Indole Acetic Acid (IAA) production, phosphate solubilisation and secretion of siderophores. Bacterial isolates showing plant growth promoting potential were identified using 16S rDNA gene sequencing as Achromobacter xylosoxidans strains A8 and C54 and Klebsiella oxytoca strain M1. Mixed inoculum was prepared from indigenous communities of mycorrhizas in soils sampled from the Cerebos Salt Pan and the Kalahari Desert. Mycorrhizal diversity was investigated using 454-Pyrosequencing which revealed that the community composition was dominated by species in the Ambispora, Glomus and Paraglomus genera with a rare component represented by species in the Redeckera, Archaeospora and Geosiphon genera. Microscopic examination of plant roots at the end of the trial revealed the presence of diagnostic mycorrhizal structures within the root cells, confirming that colonization was successful. Plant growth response to microbial inoculation was assessed by monitoring changes in plant photosynthetic capacity over the duration of a 7 week pot trial. A significant difference in photosynthetic and biomass data was observed between drought and well-watered groups but no mycorrhizal or bacterial treatment effect was evident within the groups, despite the high levels of colonization by mycorrhizas. These results suggest that the beneficial effects of mycorrhizal colonization may be primarily attributed to improved nutrient and mineral uptake in conditions where nutrients are limiting, resulting in improved growth. The improved growth may then have secondary effects on the plant‟s ability to withstand drought. Having controlled for nutrient deficiency, it was not evident in this study that mycorrhizal fungi were able to stimulate a change in plant physiology and confer drought tolerance under the conditions imposed.
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Trachsel, Samuel. "Genetic analysis of root morphology and growth of tropical maize and their role in tolerance to desiccation, aluminum toxicity and high temperature /". [S.l.] : [s.n.], 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18243.
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Kgasago, Hans. "Effect of planting dates and densities on yield and yield components of short and ultra-short growth period maize (Zea mays L.)". Diss., University of Pretoria, 2007. http://hdl.handle.net/2263/28056.
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In general, yield reduction in most dryland maize growing areas of South Africa occur because seasonal rainfall distribution is erratic with annual variation that cannot be predicted accurately. Cultivar selection, planting date and plant density are other factors that consistently affect maize yield. Long growing season maize cultivars are higher yielding, particularly under conditions of good moisture and nutrient supply. However, as both moisture and nutrient availability becomes more limiting, yield tends to decline. Short growing season maize cultivars could yield more than long season counterparts because they can maximize the growing season and potentially reach the critical flowering stage before traditional midsummer droughts occur. The short growing season maize cultivars, which have only recently been developed, have traits, which can address the problem of reduced yield, which is ascribed to midsummer drought. There has been no previous effort to evaluate the effects of planting dates and plant densities on yield and yield components of these short and ultra-short growth period maize cultivars. This prompted research in the 2004/05 growing season. One field experiment was conducted at each of two selected areas (Bethlehem&Potchefstroom) in the “Maize Triangle” of South Africa. The aim was to evaluate the response of short and ultra-short growth period maize cultivars to planting dates and plant densities at two localities with distinct environmental conditions. The effects of planting date, plant density and cultivar on yield and yield components were investigated. Both yield and yield components were affected by planting date, plant density and cultivar at both localities. At both localities early and optimum planting dates as well as low and optimum plant densities promoted increases in yield components, which contributed to increased grain yield. As for the cultivars, PAN6017 proved to be the most consistent since it out-performed other cultivars in terms of both vegetative growth, yield components and grain yield at both localities. At both localities, plant height, leaf area index and dry matter yield were affected by both planting date and plant density, with optimum planting date and optimum plant density contributing to highest yield components and yield. PAN 6017 was superior to the other cultivars at all planting dates and plant densities at both localities. In order to make findings from a study such as this applicable to the “Maize Triangle”, more research on short and ultra-short growth period maize cultivars should be conducted over a wider range of locations and seasons.Dissertation (M Inst Agrar (Agronomy))--University of Pretoria, 2007.
Plant Production and Soil Science
M Inst Agrar
unrestricted
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Dignat, Grégoire. "Dissection génétique de la croissance foliaire et de ses composantes écophysiologiques chez le maïs". Thesis, Montpellier, SupAgro, 2012. http://www.theses.fr/2012NSAM0041.
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L'objectif de cette thèse était d'analyser le déterminisme génétique de la croissance foliaire (LER) du maïs (Zea mays L.). Nous avons combiné plusieurs approches visant à (i) résumer l'information génétique tirée de trois populations de cartographie de QTL (une d'origine tropicale et deux tempérées), (ii) tester l'effet de l'introgresssion de diversité allélique dans les QTL les plus prometteurs, (iii) évaluer jusqu'à quel point les QTL de croissance foliaire affectent la croissance d'autres organes de la plante (iv) disséquer des QTLs d'intérêt par cartographie fine ou génétique d'association locale. La première partie de ce travail concerne le déterminisme génétique de la croissance foliaire maximale (LERmax) évaluée dans des conditions optimales la nuit. LERmax, telle que mesurée en plateforme de phénotypage, partage dans une forte proportion, son contrôle génétique avec la croissance d'autres organes. Des QTL qui affectaient LERmax ou/et la croissance d'autres organes ont alors été disséqués. Une région génomique a été cartographiée avec 23 lignées quasi-isogéniques (NILs) séquentiellement introgressées dans les bins 1.10-11, réduisant ainsi l'intervalle de confiance du QTL d'un facteur 3. Une seconde région génomique a été analysée par une méthode innovante fondée sur une étude d'association ciblée sur une région génomique dans un série allélique générée par introgression de 62 allèles donneurs tirés des lignées parentales d'hybrides cultivés et de populations historiques de maïs d'Amérique Latine dans une lignée élite. L'étude d'association dans cette région relativement petite révèle plus de polymorphismes causaux qu'attendus (six SNP en faible déséquilibre de liaison vs trois QTL consensus).La seconde partie de ce travail considère la sensibilité de la croissance foliaire à la demande évaporative et au déficit hydrique du sol. Un détermisme génétique commun aux deux sensibilités a été mis en évidence par méta-analyse de QTLs initialement détectés dans trois populations en ségrégation et par le test de NILs. Huit métaQTL situés dans quatre régions génomiques ont été testés avec 6 à 17 allèles introgressés pour identifier des NILs qui manifestaient les plus forts effets sur le phénotype. Nous avons initié une cartographie fine dans une de ces régions génomiques à partir d'une populations de recombinants issues de l'introgresssion d'un donneur d'origine tropicale dans B73The objective of this thesis was to analyze the genetic control of the Leaf Elongation Rate (LER) of maize (Zea mays L.). We combined approaches that (i) summarize the QTL information of three mapping populations (one tropical, two temperate), (ii) tested the impact of the introgression of allelic diversity at most promising QTLs, (iii) test to what extent QTLs of LER affect different traits (iv) dissect QTLs of interest by fine mapping or local association mapping.The first part of this document focuses on the genetic control of maximum LER (LERmax) measured in near-optimal conditions during the night. LERmax, as measured in a phenotyping platform, shares an appreciable proportion of its genetic control with the growth abilities of other organs. QTLs affecting LERmax and/or the growth of other organs were therefore dissected. One genomic region was fine-mapped with 23 Near-Isogenic Lines (NILs), sequentially introgressed in the bins 1.10-11, resulting in a reduction of the confidence interval by a factor 3. A second genomic region was analysed after the development of an innovative method of local association mapping on a collection of NILs, introgressed with 62 donor parents from historical populations from different altitude and latitudes in Latin America. This relatively small region harbors more causal polymorphisms than expected (six associated markers in low linkage disequilibrium vs three cQTLs).The second part focuses on the sensitivities of LER to evaporative demand or to soil water deficit. The two sensitivities share a large part of their genetic control as demonstrated by a metaQTL analysis on three mapping populations and the test of NILs. Eight metaQTLs in four genomic regions were tested with 6 to 17 different alleles to find the NILs that best impact the phenotype. We started a fine mapping on one genomic region by using one population of NILs involving a tropical donor
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Kgasago, Hans. "Effect of planting dates and densities on yield and yield components of short and ultra-short growth period of maize (Zea mays L.)". Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-09202007-163045.
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Neto, Francisco Bezerra. "Effects of spatial arrangement and density on efficiency, yield and yield components, dry matter partitioning and growth of an annual cotton/cowpea/maize intercrop". Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186205.
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The effects of spatial arrangement and density on agronomic efficiency, yield and yield components, dry matter partitioning and growth of an annual cotton/cowpea/maize intercrop were examined in 1990 and 1991 in Tucson, Arizona. The 1990 experiment consisted of four spatial arrangements crossed with four densities of cowpea and maize in a complete factorial design. The 1991 experiment consisted of two densities of cowpea and maize selected from the 1990 experiment in the best spatial arrangement crossed with five densities of cotton in a complete factorial design. A land use efficiency of 12% (or a land equivalent ratio of 1.12) was obtained in the spatial arrangement of single rows of cowpea and maize between singles rows of cotton, whereas a land use efficiency of 11% was obtained for cowpea and maize at a combined density of 50,000 plants/ha intercropped with cotton at a density of 50,000 plants/ha. Maize provided a greater contribution to the land use efficiency than either cotton or cowpea. Cotton yield was highest in the spatial arrangement of single rows of cowpea and maize between single rows of cotton. For the two food crops, cowpea yield was highest in the spatial arrangements in which cowpea and maize were grown in different rows between rows of cotton, whereas maize yield was highest in the spatial arrangements in which cowpea and maize were grown in the same rows between rows of cotton. Cotton fiber quality was not influenced by spatial arrangement, cowpea/maize density, and cotton density. Number of cowpea pods was affected by spatial arrangement in a manner similar to cowpea yield. Number of maize ears increased as cowpea/maize density increased, whereas number of kernels/ear, weight of 100 kernels and length of kernel rows decreased as cowpea/maize density increased. Dry matter accumulation in leaves, stems, and fruits of cotton and cowpea was greatest in the spatial arrangements in which cowpea and maize were grown in different rows between rows of cotton. Weekly cotton growth rate increased as cotton density increased from 39 to 74 days after sowing.
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Batista, Bruna Durante. "Promoção de crescimento em milho (Zea mays L.) por rizobactérias associadas à cultura do guaranazeiro (Paullinia cupana var. sorbilis)". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/11/11137/tde-25032013-154749/.
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O uso de fertilizantes minerais nas culturas, inclusive no milho, é uma prática agrícola que provoca danos ambientais e prejuízos econômicos. Uma alternativa promissora, visando melhorar a produtividade e reduzir o uso de fertilizantes, é a utilização de microrganismos benéficos associados às plantas, particularmente as rizobactérias promotoras de crescimento. Essas bactérias vivem na rizosfera e são capazes de colonizar diversos tecidos vegetais, beneficiando o desenvolvimento das plantas através de mecanismos de promoção de crescimento. Na busca por alternativas sustentáveis e mais rentáveis, o presente trabalho teve como objetivo isolar, caracterizar, selecionar e monitorar rizobactérias associadas ao guaranazeiro da Amazônia que possuíssem características promotoras de crescimento vegetal para serem usadas como inoculantes em sementes de milho. Amostras de solo rizosférico de cinco plantas de guaranazeiros foram coletadas e foi realizado o isolamento das rizobactérias. A caracterização molecular foi realizada através do sequenciamento do gene 16S rDNA para análise da diversidade microbiana e identificação das linhagens. Avaliou-se a capacidade das linhagens de produzir ácido indol acético (AIA), fixar nitrogênio atmosférico, solubilizar fosfato inorgânico e de produzir sideróforos. A análise da diversidade microbiana indicou semelhança entre a comunidade bacteriana isolada da rizosfera do guaranazeiro e a do milho encontrada na literatura. Foi observada predominância do filo Proteobacteria, sendo em sua maioria representado pelo gênero Burkholderia. Do total das 101 linhagens obtidas, 89% foram capazes de produzir AIA, 23% fixaram nitrogênio atmosférico, 43% solubilizaram fosfato inorgânico e 24% produziram sideróforos. Cinco linhagens foram selecionadas para o ensaio de promoção de crescimento de milho em casa de vegetação, essas foram identificadas pelo sequenciamento completo do gene 16S rDNA e compuseram os tratamentos como segue: RZ2MS9 - Bacillus sp. (T1), RZ2MS16 - Burkholderia ambifaria (T2) e consórcio (T3) de 5 linhagens (RZ1MS6 - Burkholderia vietnamiensis, RZ1MS11 - Burkholderia sp., RZ2MS9 - Bacillus sp., RZ2MS16 - Burkholderia ambifaria e RZ4MS18 - Delftia acidovorans). As análises estatísticas comprovaram que as linhagens RZ2MS9 (Bacillus sp.) e RZ2MS16 (Burkholderia ambifaria) foram eficientes como promotoras de crescimento em milho, aumentando a altura cerca de 39 e 33%, respectivamente, em relação ao controle, o peso seco da parte aérea cerca de 236 e 114% e do sistema radicular cerca de 248 e 136%, respectivamente, comparado ao controle não inoculado. A linhagem RZ2MS9 (Bacillus sp.) aumentou o conteúdo de Ca nas plantas inoculadas. Para o monitoramento da colonização da bactéria na planta, a linhagem RZ2MS16 (Burkholderia ambifaria) foi transformada com o plasmídio pCM88 e passou a expressar a proteína GFP, sendo possível observar, por microscopia óptica de fluorescência, que, 12 dias após a inoculação na planta, a bactéria encontra-se concentrada no cilindro central da raiz da mesma de onde pode se inserir em algum vaso condutor e colonizar a planta sistematicamente, o que demonstra que a mesma se comporta como endofítica da planta de milho. Assim, fica evidente a importância da exploração de plantas de clima tropical, como o guaranazeiro, como reservatórios de bactérias com enorme potencial biotecnológico. As bactérias estudadas nesse trabalho tem grande potencial para serem utilizadas futuramente como inoculantes.The use of mineral fertilizers on agricultural crops, including maize, is a practice that causes environmental damage and economical losses. A promising alternative, to improve productivity and reduce fertilizer use is the use of benefical microrganisms associated with plants, particulary the growth-promoting rhizobacteria. These bacteria live in the rhizosphere and are capable of colonizing different plant tissues, benefiting plant growth through mechanisms of growth promotion. In the search for sustainable and more profitable alternative, this study aimed to isolate, characterize, monitor and select rhizobacteria associated with Amazonian guarana that possessed characteristics of plant growth promoters for use as inoculants in maize seeds. Rhizosphere soil samples from five guarana plants were collected and the isolation of rhizobacteria was performed. Molecular characterization was performed by sequencing the 16S rDNA for analysis of microbial diversity and identification of strains. It was evaluated the ability of strains to produce indole acetic acid (IAA), fix atmospheric nitrogen, solubilize inorganic phosphate and produce siderophores. The analysis of microbial diversity indicated similarity between the bacterial community isolated from the rhizosphere of guarana and that found in the literature to maize. It was observed predominance of Proteobacteria phylum, being mostly represented by the genus Burkholderia. Of the total 101 strains obtained, 89% were able to produce IAA, 23% fixed atmospheric nitrogen, 43% solubilized inorganic phosphate and 24% produced siderophores. Five strains were selected for testing growth promotion of maize under greenhouse conditions; these were identified by complete sequencing of the 16S rDNA and compose the treatments as follows: RZ2MS9 - Bacillus sp. (T1), RZ2MS16 - Burkholderia ambifaria (T2) and consortium (T3) of 5 strains (RZ1MS6 - Burkholderia vietnamiensis, RZ1MS11 - Burkholderia sp., RZ2MS9 - Bacillus sp., RZ2MS16 - Burkholderia ambifaria and RZ4MS18 - Delftia acidovorans). Statistical analyzes showed that the strains RZ2MS9 (Bacillus sp.) and RZ2MS16 (Burkholderia ambifaria) were effective as growth promoters in maize, increasing the height about 39 and 33%, respectively, compared to control, shoot dry weight about 236 and 114% and root system about 248 and 136%, respectively, compared to uninoculated control. The strain RZ2MS9 (Bacillus sp.) increased Ca content in inoculated plants. For monitoring of colonization of the bacteria in the plant, the strain RZ2MS16 (Burkholderia ambifaria) was transformed with the plasmid pCM88 and passed to express GFP, being possible to observe by fluorescence microscopy that, 12 days after inoculation on the plant, the bacteria is concentrated in the root central cylinder where the same can be inserted into a vessel conductor and consistently colonize the plant, proving the endophytic life style of this strain during maize interaction. Thus, it is clear the importance of tropical plants, like guarana, as reservoirs of bacteria with great biotechnological potential. The evaluated bacteria accessed in this work have great potential to be used in future as inoculants.
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Tchuisseu, Tchakounte Gylaine Vanissa. "Assessing the role of native plant growth-promoting rhizobacteria (PGPR) isolated from Cameroon soil as bio-inoculant in improving plant growth". Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22323.
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Der Mangel an Nährstoffen im Boden, hauptsächlich an Phosphor (P) und Stickstoff (N), verbunden mit einem hohen Salzgehalt und der generellen Verarmung landwirtschaftlicher Böden , sind ein ernstes Problem für die landwirtschaftliche Produktion weltweit. Daher besteht ein dringender Bedarf an Forschung und Entwicklung geeigneter landwirtschaftlicher Praktiken, um ungünstige Bodenbedingungen zu verringern und wenn möglich die Fruchtbarkeit von Kulturland wiederherzustellen. Die Verwendung von Rhizobakterien, die das Pflanzenwachstum (PGPR) fördern, kann sich bei der Entwicklung von Strategien zur Erleichterung des Pflanzenwachstums unter normalen Wachstumsbedingungen sowie unter abiotischen Stress als nützlich erweisen. Diese Bakterien bieten ihren pflanzlichen Wirten Vorteile, indem sie die Aufnahme von Bodenmineralien fördern und Pflanzen vor schädlichen Umwelteinflüssen schützen. Die vorliegende Arbeit bewertet die Rolle von in Kamerun natürlich vorkommenden PGPR an Mais und untersucht deren Potenzial als Bioimpfstoffe zur Steigerung des Pflanzenwachstums in Kamerun. Wir prüfen die Hypothese, dass einheimische Bakteriengemeinschaften aus Kamerun einen hohen Anteil an Bakterien aufweisen, deren Eigenschaften Kulturpflanzen helfen, mit ungünstigen Bedingungen umzugehen. In der vorliegenden Arbeit wurden dazu Bakteriengemeinschaften der Rhizosphäre von in Kamerun angebautem Mais isoliert und untersucht. Zum ersten Mal erfolgte eine umfassende phylogenetische Zuordnung aller kultivierbaren Bakterien, auf Grundlage ihrer potenziellen Fähigkeiten zur Förderung des Pflanzenwachstums.Nutrient deficiencies in soil, mainly in phosphorus (P) and nitrogen (N), coupled to salinity and the impoverishment of agricultural soils, are a severe problem for agricultural production worldwide. Therefore, there is an urgent need for research and development of more suitable agricultural practices in order to reduce unfavorable conditions, and if possible, to restore the fertility of cultivated lands. The use of rhizobacteria, which promote plant growth (PGPR), can prove useful in developing strategies to facilitate plant growth under normal as well as under abiotic stress conditions. These bacteria offer benefits to plant hosts by promoting the uptake of soil minerals and protecting plants from environmental stresses. The thesis evaluates the role of native PGPR associated with maize as potential bio-inoculants for plants growth in Cameroon. We hypothesized that native bacterial communities from Cameroon include a high potential of bacteria helping the plant cope with unfavorable conditions. Here, we provide for the first time a comprehensive phylogenetic affiliation of cultivable bacterial communities associated with maize rhizosphere grown in Cameroon in relationship to their potential plant growth-promoting abilities.