Academic literature on the topic 'Phytopathogenic microorganisms Biological control'
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Journal articles on the topic "Phytopathogenic microorganisms Biological control"
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Malta, Camilla Martins, Eskálath Morganna Silva Ferreira, Thamar Holanda Da Silva, Divina Anne Batista Oliveira, Filipe Miguel Pereira Da Silva, Juliana Fonseca Moreira Da Silva, and Raphael Sanzio Pimenta. "Isolation of epiphytic yeasts from Eugenia dysenterica DC. fruits and evaluation of their antimicrobial activity against phytopathogenic fungi." Boletim do Museu Paraense Emílio Goeldi - Ciências Naturais 14, no. 2 (August 27, 2019): 223–31. http://dx.doi.org/10.46357/bcnaturais.v14i2.176.
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Plants commonly interact with microorganisms that may influence their physiology and performance. Epiphytic yeasts are microorganisms that can be found in the phylosphere, in significantly larger numbers in fruits than in other plant tissues due to their higher nutritional content. The present study aimed to contribute to knowledge of epiphytic yeasts associated with Eugenia dysenterica DC. fruits and to evaluate their antimicrobial activity against phytopathogens. E. dysenterica fruits were collected, washed in saline solution, and sonicated. Each fruit solution was plated in three Petri dishes with NYDA medium. Yeast identification was performed through morphological and physiological criteria, and richness evaluation was performed using the Jackknife 1 estimator. All isolated yeasts were tested for diffusible substances against three phytopathogenic fungi. Only four of 42 isolates were inhibited sporulation of Aspergillus parasiticus, but none was able to inhibit or diminish mycelium growth of any tested phytopathogen. The present study contributes to the characterization of the E. dysenterica microbiome, presenting the first report of in vitro A. parasiticus sporulation inhibition by epiphytic yeasts and suggesting their promising use in biological control of this phytopathogen.
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Moreno-Gavíra, Alejandro, Victoria Huertas, Fernando Diánez, Brenda Sánchez-Montesinos, and Mila Santos. "Paecilomyces and Its Importance in the Biological Control of Agricultural Pests and Diseases." Plants 9, no. 12 (December 10, 2020): 1746. http://dx.doi.org/10.3390/plants9121746.
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Incorporating beneficial microorganisms in crop production is the most promising strategy for maintaining agricultural productivity and reducing the use of inorganic fertilizers, herbicides, and pesticides. Numerous microorganisms have been described in the literature as biological control agents for pests and diseases, although some have not yet been commercialised due to their lack of viability or efficacy in different crops. Paecilomyces is a cosmopolitan fungus that is mainly known for its nematophagous capacity, but it has also been reported as an insect parasite and biological control agent of several fungi and phytopathogenic bacteria through different mechanisms of action. In addition, species of this genus have recently been described as biostimulants of plant growth and crop yield. This review includes all the information on the genus Paecilomyces as a biological control agent for pests and diseases. Its growth rate and high spore production rate in numerous substrates ensures the production of viable, affordable, and efficient commercial formulations for agricultural use.
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GHARBI, Samia, Pelias RAFANOMEZANTSOA, Ryme TERBECHE, Nassima DRAOU, and Noureddine KARKACHI. "Evaluation of the antagonistic potential of bacterial strains isolated from Algerian soils for the biological control of phytopathogenic fungi." Journal of Applied and Natural Science 14, no. 2 (June 18, 2022): 647–51. http://dx.doi.org/10.31018/jans.v14i2.3479.
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Antagonistic bacteria contribute to the management of plant diseases by stimulating the natural defenses in the host and/or by ensuring direct biocontrol of the aggressors. The objective of this work was to isolate, identify and evaluate (in vitro) various Bacillus spp. for their potential to control phyopathogenic fungi. Selection of the 40 strains of Bacillus previously isolated from the soil in various areas of western Algeria was carried out by direct confrontation on the mycelial growth of four phytopathogens (Fusariumoxysporumf.splycopersici, Alternaria tenuis , Phytophthorainfestans, Ascochytapisi). This strategy involved using the antagonistic potential of microorganisms found in the plant environment in Algeria. The second part of this work consisted of the characterization and identification of tested strainsThe identification of the selected strains was carried out by biochemical tests. The results obtained showed that at the end of the fifth day, the most promising isolates showed antifungal activity and reached an inhibition rate of the mycelial growth of phytopathogenic fungi, respectively, F. oxysporumf. splycopersici 75%, A. tenuis 80%, P. infestans 83.30%, Ascochytapisi 67%. The potential antagonist of Bacillus tested in vitro by direct confrontation against 04 phytopathogenic fungi showed that all strains of Bacillus decreased fungal mycelial growth. Two strains of Bacillus B30 and B41 were found to have the most efficacy against Fusarium oxysporum f.sp. lycopersici, Alternaria tenius, Phytophtora infestans et Ascochyta pisi, with an inhibition rate of 65.25 and 72.25% respectively These results demonstrate that Bacillus sp. presenteds a potential for biological control. However, it is important to understand the mechanisms implemented by these bacteria to develop effective protection strategies.
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Natsiopoulos, Dimitrios, Apostolos Tziolias, Ioannis Lagogiannis, Spyridon Mantzoukas, and Panagiotis A. Eliopoulos. "Growth-Promoting and Protective Effect of Trichoderma atrobrunneum and T. simmonsii on Tomato against Soil-Borne Fungal Pathogens." Crops 2, no. 3 (June 29, 2022): 202–17. http://dx.doi.org/10.3390/crops2030015.
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Trichoderma fungi are promising candidates for biocontrol agents and plant growth promoters. Trichoderma atrobrunneum and T. simmonsii were evaluated for the control of soil-borne phytopathogenic fungi, in the present study. Dual culture tests with Rhizoctonia solani and Fusarium oxysporum f. sp. lycopersici were used to conduct in vitro evaluation. In the presence of Trichoderma, phytopathogen’s growth rate was inhibited up to 59.70% for R. solani and 42.57% for F. oxysporum. Greenhouse trials with potted tomato plants demonstrated that Trichoderma caused a significant increase of stem height and fresh stem weight in pathogen-inoculated plants, compared with the negative control (plants artificially inoculated with the phytopathogen only). Except for T. simmonsii, plant growth was not significantly enhanced by a Trichoderma presence in the positive control (healthy plants). The overall performance of the two Trichoderma species studied was equivalent to that of the T. harzianum T22 commercial strain. All the tested species were found to be effective in suppressing colony growth and disease development of the soil borne pathogens in dual cultures and potted plants, indicating that they could be used as biocontrol agents. Our findings are discussed in the context of enhancing endophytic microorganisms’ application in crop production systems.
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Billar de Almeida, Angela, Jonathan Concas, Maria Doroteia Campos, Patrick Materatski, Carla Varanda, Mariana Patanita, Sergio Murolo, Gianfranco Romanazzi, and Maria do Rosário Félix. "Endophytic Fungi as Potential Biological Control Agents against Grapevine Trunk Diseases in Alentejo Region." Biology 9, no. 12 (November 26, 2020): 420. http://dx.doi.org/10.3390/biology9120420.
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Grapevine trunk diseases (GTDs) are the most widespread fungal diseases, affecting grapevines in all the major growing regions of the world, and their complete eradication is still not possible. Aiming to search alternatives to avoid the spread and high incidence of these diseases, the present work intended to molecularly identify the grapevine endophytic community, the phytopathogenic fungi associated with GTDs in vineyards within the Alentejo region, and to test potential antagonist microorganisms as biological control candidates against GTDs-associated fungi. Grapevine endophytic community showed a wide variety of fungi in GTDs’ asymptomatic and symptomatic plants, nine of them previously described as GTDs-associated fungi. GTDs prevalent fungi identified in symptomatic plants were Diaporthe sp., Neofusicoccum sp., and H. viticola. Almost all these fungi were also detected in asymptomatic plants, which shows the importance of investigating the interactions of fungal communities and confirms the need for early diagnosis of these diseases. Direct inhibition antagonism tests were performed among identified endophytes and GTDs phytopathogenic fungi, and all the endophyte fungi showed potential as biocontrol agents. Our findings suggest that endophytes are promising candidates for their use in biological control due to their antagonistic activity against the mycelia growth of some GTDs-associated fungi.
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Basso Valeria, González. "Biological control, an important tool for sustainable agriculture." Journal of Applied Biotechnology & Bioengineering 9, no. 5 (2022): 176–80. http://dx.doi.org/10.15406/jabb.2022.09.00307.
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Biological Control (BC) with antagonistic microorganisms is one of the tools within the Integrated Management of Pests and Diseases (MIPE), being an important sustainable alternative to mitigate the negative effects that refer to the quality and productivity of agricultural crops. Therefore, this bibliographic review study reports on the research that needs to be carried out, such as: antagonistic studies on the various phytopathogens, efficacy studies on a wide range of microorganisms, evaluations of specificity between antagonists and phytopathogens, studies of the viability in the introduction of an antagonistic agent in a plant-soil-environment system and of the complex interactions between plants, people, and the environment. It also discusses the uses and types of CB, and the variety of CB strategies available for use
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SCHRADER, Stefan, Friederike WOLFARTH, and Elisabeth OLDENBURG. "Biological Control of Soil-borne Phytopathogenic Fungi and their Mycotoxins by Soil Fauna." Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Agriculture 70, no. 2 (November 25, 2013): 291–98. http://dx.doi.org/10.15835/buasvmcn-agr:9743.
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Yield loss through harmful fungi is a serious problem in crop production worldwide. Cereal residues like straw are frequently infected by Fusarium fungi, which produce mycotoxins like deoxynivalenol (DON). Mycotoxins lead to quality losses in cereal-based food and feed which endangers human and animal health. Especially under conservation tillage, when mulching techniques are applied to protect soil from erosion, run-off etc., residues should be efficiently degraded to protect the currently cultivated crop from fungal infection and mycotoxin contamination. The objective of this review is to give an overview on which role decomposing soil fauna plays in the fate of Fusarium fungi and there main mycotoxin DON in the soil system. Generally, soil fauna benefits from conservation tillage compared to conventional tillage. Results from experiments in the laboratory and field revealed that earthworms as primary and secondary decomposers as well as fungivorous collembolans and soil nematodes contribute to the ecosystem services of pathogen depression and toxin degradation with respect to Fusarium and DON. Fusarium seems to be an attractive food source. Furthermore, the mycotoxin DON does not cause any harm to the soil fauna tested. Key factors for the control of Fusarium development by antagonistic soil fauna are: (1) interaction with soil microorganisms; (2) interaction of soil fauna species; (3) soil texture; (4) residue exposure. Ecosystem services of antagonistic soil fauna are vital to crop production and the functioning of agroecosystems. They will be discussed in a broader context of soil health and conservation tillage.
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Zhou, Yang, Shuoxing Yi, Yi Zang, Qing Yao, and Honghui Zhu. "The Predatory Myxobacterium Citreicoccus inhibens gen. nov. sp. nov. Showed Antifungal Activity and Bacteriolytic Property against Phytopathogens." Microorganisms 9, no. 10 (October 12, 2021): 2137. http://dx.doi.org/10.3390/microorganisms9102137.
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The application and promotion of biological control agents are limited because of poor efficacy and unstable performance in the field. Screening microorganisms with high antagonistic activity, effective adaptability, and high field-survival should be prospected. Myxobacteria are soil predatory bacteria with wide adaptability, which are considered as good antagonists. Here, we report a myxobacterium strain M34 isolated from subtropical forest soil in South China using the Escherichia coli baiting method. Based on the morphological observation, physiological test, biochemical characteristics, 16S rRNA gene sequence, and genomic data, strain M34 was identified as a novel genus and novel species, representing a new clade of Myxococcaceae, for which the name Citreicoccus inhibens gen. nov. sp. nov. is proposed (type strain M34T = GDMCC 1.2275T = KCTC 82453T). The typical features of M34, including fruiting body formation and extracellular fibrillar interconnection, indicated by microscopic observations, contributed to cell adaption in different environments. Furthermore, the strain showed antifungal activity against phytopathogenic fungi and predatory activity to both Gram-negative and Gram-positive phytopathogenic bacteria. The bioprotective mechanisms are attributed to the presence of pyrrolnitrin and derivative with antifungal activity and the extracellular proteins with lytic activity against pathogenic bacteria. Due to its multiple beneficial traits, strain M34 has the potential to be developed into a versatile biocontrol agent for the management of both fungal and bacterial phytopathogens.
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Fontana, Daniele Cristina, Samuel de Paula, Abel Galon Torres, Victor Hugo Moura de Souza, Sérgio Florentino Pascholati, Denise Schmidt, and Durval Dourado Neto. "Endophytic Fungi: Biological Control and Induced Resistance to Phytopathogens and Abiotic Stresses." Pathogens 10, no. 5 (May 8, 2021): 570. http://dx.doi.org/10.3390/pathogens10050570.
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Plant diseases cause losses of approximately 16% globally. Thus, management measures must be implemented to mitigate losses and guarantee food production. In addition to traditional management measures, induced resistance and biological control have gained ground in agriculture due to their enormous potential. Endophytic fungi internally colonize plant tissues and have the potential to act as control agents, such as biological agents or elicitors in the process of induced resistance and in attenuating abiotic stresses. In this review, we list the mode of action of this group of microorganisms which can act in controlling plant diseases and describe several examples in which endophytes were able to reduce the damage caused by pathogens and adverse conditions. This is due to their arsenal of molecules generated during the interaction by which they form a kind of biological shield in the plant. Furthermore, considering that endophytic fungi can be an important tool in managing for biotic and abiotic stresses due to the large amount of biologically active substances produced, bioprospecting this class of microorganisms is tending to increase and generate valuable products for agriculture.
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Asaturova, Anzhela, Natalya Zhevnova, Natalya Tomashevich, Marina Pavlova, Oksana Kremneva, Galina Volkova, and Nikita Sidorov. "Efficacy of New Local Bacterial Agents against Pyrenophora tritici-repentis in Kuban Region, Russia." Agronomy 12, no. 2 (February 1, 2022): 373. http://dx.doi.org/10.3390/agronomy12020373.
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The phytopathogenic fungus Pyrenophora tritici-repentis is a causal agent of tan spot. Antagonistic microorganisms can be used as a non-chemical alternative treatment against the tan spot of wheat. Bacillus velezensis BZR 336 g and BZR 517 stains were selected as the most active microorganisms and potential biocontrol agents. We found that B. velezensis strains BZR 336 g and BZR 517 exhibited antagonistic activity against P. tritici-repentis Kr-15/2016 in vitro: they inhibited mycelium growth by 72.4–94.3% and caused its degenerative changes. Treatment of seeds and plants with strains BZR 336 g and BZR 517 provided a biological efficiency of 31.2–38.4% against tan spot, while artificial inoculation of plants provided only 28.4–43.8% biological efficiency. Treatment of seeds and plants with BZR 336 g and BZR 517 in a three-year field trial demonstrated 24.6–50% biological efficiency. BZR 336 g and BZR 517 provided 5.0–7.6% additional yield. We conclude that BZR 336 g and BZR 517 are promising options for novel bioproducts that can control P. tritici-repentis tan spot.
Dissertations / Theses on the topic "Phytopathogenic microorganisms Biological control"
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Kabir, Nasreen Zahan. "Selection of effective antagonists against Rhizoctonia solani (AG-3), the causal agent of Rhizoctonia disease of potato." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27351.
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Rhizoctonia solani (AG-3), the causal agent of Rhizoctonia disease of potato, overwinters as sclerotia on potato tubers. To develop a biocontrol strategy based on the prevention of the sclerotial germination, an isolation of microorganisms colonizing sclerotia of infected potato tubers (cultivars Norland, Atlantic and Souris), was conducted. In vitro screening was used to select effective antagonistic fungi against Rhizoctonia solani. Fifty fungal isolates were selected in order to cover all identified genera and potato variety and examined for their ability to inhibit germination of sclerotia which were incubated with the test fungus for 14 days. Twenty-four (24) fungal isolates were retained based on their ability to reduce sclerotial viability by more than 50% as compared with 100% viability of untreated sclerotia. These 24 isolates were further examined for their ability to protect Table beet seedlings against the pathogen in greenhouse soils. Based on their ability to protect Table beet seedlings from Rhizoctonia infections and to increase the number of secondary roots and root length isolates, F2, F11, F132, F158, and F258 were screened and test their efficacy to increase beet seed germination in field soils. (Abstract shortened by UMI.)
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Alfaro, Lemus Ana Lilia. "Factors influencing the control of citrophilous mealybug Pseudococcus calceolarie (Maskell) by Coccophagus gurneyi Compere in the Riverland of South Australia." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09IM/09iml562.pdf.
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Includes bibliographical references (leaves 102-114) The highly successful biological control of the citrophilous mealybug Pseudococcus calceolarie (Maskell) (CM) by the parasitic wasp Coccophagus gurneyi Compere in several countries led to the release of this parasitoid in the Riverland of South Australia as part of an integrated pest management program. However CM has not been successfully controlled in this region. The results of this study may help to explain the lack of effective biological control of CM in Riverland citrus.
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Mphahlele, Mogalatjane Patrick. "Honey bee dissemination of Bacillus subtilis to citrus flowers for control of Alternaria." Diss., University of Pretoria, 2003. http://hdl.handle.net/2263/24207.
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The initial phase in the development of a biological control strategy is screening of biological control agents. Secondary to this phase is the establishment of accurate, effective application techniques. However, successful control requires a thorough understanding of all factors affecting the relationship between host plant, pathogen and other microbes. The purpose of this study was to screen and identify potential bacterial antagonists against Alternaria, a fungal citrus pathogen, attachment of the antagonists to bees, and bee dissemination of the antagonist to citrus flowers. A total of 568 bacterial epiphytes were screened on agar plates for antagonism against Alternaria. Only eight of these isolates, which were identified as Bacillus subtilis, B licheniformis, B. melcerons, B. polymyxa, B. thermoglycodasius, B. sphaericus, B. amiloliquefaciens, and B. coagulans, showed inhibitory effects on the growth of Alternaria. The most effective isolates were B. subtilis and B. licheniformis. Further screening was done with B. subtilis and B. subtilis commercial powder (Avogreen). These bacteria were sprayed on citrus flowers for colonisation studies. Mean populations of B. subtilis and the commercial powder recovered from the flowers were 104 and 103 cfu/stamen respectively. The organisms colonised the styler end and ovary of the flowers when observed under scanning electron microscope (SEM). Avogreen was placed in an inoculum dispenser, which was attached to the entrance of the hive. Honeybees emerging from the beehive acquired 104 cfu/bee. The powder attached to the thorax and thoracic appendages, as revealed by SEM. One active beehive was placed in an enclosure with fifteen flowering citrus nursery trees in pots for dissemination trials. Mean populations of commercial B. subtilis recovered from the flowers visited by bees were 104 cfu/stamen. Electron microscope studies revealed that the antagonist was colonising the styler end and ovary of the flowers. Field dissemination studies were unsuccessful due to low yields.Dissertation (Magister Institutiones Agrariae)--University of Pretoria, 2006.
Plant Production and Soil Science
unrestricted
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Ghajar, Feridon Ghasem Khan. "Stimulatory and inhibitory effects of UVA and UVB radiation on some physiological and pathogenic characteristics of fungal biocontrol agents to enhance mycoherbistat effectiveness." View thesis, 2004. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20050722.084927/index.html.
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Gumede, Halalisani. "The development of a putative microbial product for use in crop production." Thesis, Rhodes University, 2008. http://eprints.ru.ac.za/1352/.
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Becker, John van Wyk 1975. "Evaluation of the role of PGIPs in plant defense responses." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/17476.
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Dissertation (PhD)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: Plants have developed sophisticated means of combating plant diseases. The events that prepare the plant for, and follow plant-pathogenic interactions, are extremely complex and have been the topic of intensive investigation in recent years. These interactions involve a plethora of genes and proteins, and intricate regulation thereof; from the host and pathogen alike. Studying the contribution of single genes and their encoded proteins to the molecular dialogue between plant and pathogen has been a focus of plant molecular biologists. To this end, a gene encoding a polygalacturonase-inhibiting protein (PGIP) was recently cloned from Vitis vinifera. These proteins have the ability to inhibit fungal endopolygalacturonases (ePGs), enzymes which have been shown to be required for the full virulence of several fungi on their respective plant hosts. The activity of PGIP in inhibiting fungal macerating enzymes is particularly attractive for the improvement of disease tolerance of crop species. The VvPGIP-encoding gene was subsequently transferred to Nicotiana tabacum for high-level expression of VvPGIP. These transgenic plants were found to be less susceptible to infection by Botrytis cinerea in an initial detached leaf assay. Also, it was shown that ePG inhibition by protein extracts from these lines correlated to the observed decrease in susceptibility to B. cinerea. This study expands on previous findings by corroborating the antifungal nature of the introduced PGIP by whole-plant, timecourse infection assays. Six transgenic tobacco lines and an untransformed wildtype (WT) were infected and the lesions measured daily from day three to seven, and again at day 15. The transgenic lines exhibited smaller lesions sizes from three to seven days post-inoculation, although these differences only became statistically significant following seven days of incubation. At this point, four of the six lines exhibited significantly smaller lesions than the WT, with reductions in disease susceptibility ranging between 46 and 69% as compared to the WT. Two of the lines exhibited disease susceptibility comparable to the WT. In these resistant plant lines, a correlation could be drawn between Vvpgip1 expression, PGIP activity and ePG inhibition. These lines were therefore considered to be PGIP-specific resistant lines, and provided ideal resources to further study the possible in planta roles of PGIP in plant defense. The current hypothesis regarding the role(s) of PGIP in plant defense is twofold. Firstly, PGIPs have the ability to specifically and effectively inhibit fungal ePGs. This direct inhibition results in reduced fungal pathogenicity. Alternatively, unhindered action of these enzymes results in maceration of plant tissue and ultimately, tissue necrosis. Subsequently, it could be shown that, in vitro, the inhibition of ePGs prolongs the existence of oligogalacturonides, molecules with the ability to activate plant defense responses. Thus, PGIPs limit tissue damage by inhibition of ePG; this inhibition results in activation of plant defense responses aimed at limiting pathogen ingress. Several publications reported reduced susceptibility to Botrytis in transgenic plant lines overexpressing PGIP-encoding genes. However, none of these publications could expand on the current hypotheses regarding the possible in planta roles of PGIP in plant defense. In this study we used transgenic tobacco lines overexpressing Vvpgip1 as resources to study the in planta roles for PGIP. Transcriptomic and hormonal analyses were performed on these lines and a WT line, both before and following inoculation with Botrytis cinerea. Transcriptomic analysis was performed on uninfected as well as infected tobacco leaf material utilizing a Solanum tuberosum microarray. From the analysis with healthy, uninfected plant material, it became clear that genes involved in cell wall metabolism were differentially expressed between the transgenic lines and the WT. Under these conditions, it could be shown and confirmed that the gene encoding tobacco xyloglucan endotransglycosylase (XET/XTH) was downregulated in the transgenic lines. Additionally, genes involved in the lignin biosynthetic pathway were affected in the individual transgenic lines. Biochemical evidence corroborated the indication of increased lignin deposition in their cell walls. Additionally, phytohormone profiling revealed an increased indole-acetic acid content in the transgenic lines. These results show that constitutive levels of PGIP may affect cell wall metabolism in the Vvpgip1-transgenic lines which may have a positive impact on the observed reduced susceptibilities of these plants. An additional role for PGIP in the contribution to plant defenses is therefore proposed. PGIP may directly influence defense responses in the plant leading to the strengthening of cell walls. This might occur by virtue of its structural features or its integration in the cell wall. These reinforced cell walls are thus “primed” before pathogen ingress and contribute to the decrease in disease susceptibility observed in lines accumulating high levels of PGIP. Transcriptional and hormonal analyses, at the localized response, were performed on Botrytis-infected leaf tissue of the transgenic lines and a WT line. Several Botrytis responsive genes were found to be upregulated in both the WT and the transgenic lines. Although limited differential expression was observed between the two genotypes, the analyses identified a gene which was upregulated two-fold in the transgenic lines, as compared to WT. This was confirmed by quantitative Real-Time PCR. This gene is involved in the lipoxygenase pathway, specifically the 9-LOX branch, leading to the synthesis of the divinyl ether oxylipins colneleic and colnelenic acid, which show inhibitory effects on Botrytis spore germination. Phytohormone profiling revealed that the transgenic lines accumulated more of the defense-related hormone pool of jasmonates. These are formed via the 13-LOX pathway and have been shown to be important for the restriction of Botrytis growth at the site of infection. Collectively, the results from the infection analyses indicate that in these transgenic lines, both branches of the lipoxygenase pathway are differentially induced at the level of the localized response to Botrytis infection. Similarly, an increased induction of the synthesis of the defense-related hormone salicylic acid could be observed, although this hormone did not accumulate to significantly higher levels. These results are the first report of differential induction of a defense-related pathway in pgip-overexpressing lines and substantiate the proposal that following ePG inhibition by PGIP, signaling which activates plant defense responses, takes place. Taken together, these results significantly contribute to our understanding of the in planta role of PGIP in plant defense responses.
AFRIKAANSE OPSOMMING: Plante het deur evolusie gesofistikeerde meganismes teen die aanslag van plantsiektes ontwikkel. Die gebeure wat die plant voorberei, asook dié wat op plant-patogeen interaksies volg, is uiters kompleks en vorm die kern van verskeie navorsingstemas die afgelope paar jaar. Etlike plant- én patogeengene en proteïene is by hierdie interaksies betrokke en aan komplekse reguleringsprosesse onderworpe. Die bestudering van die bydrae van enkelgene en hul gekodeerde proteïene tot die molekulêre interaksie tussen ‘n plant en patogeen is ‘n sterk fokus van plant-molekulêre bioloë. Met hierdie doel as fokus, is ‘n geen wat vir ‘n poligalakturonaseinhiberende proteïen (PGIP) kodeer, van Vitis vinifera gekloneer. Hierdie proteïene beskik oor die vermoë om fungiese endopoligalakturonases (ePG's), ensieme wat benodig word vir die virulensie van verskeie fungi op hul gasheerplante, te inhibeer. Die inhibisie van ePG's deur PGIP en die gepaardgaande verminderde weefseldegradasie is ‘n baie belowende strategie vir die verbetering van verboude gewasse se patogeentoleransie. Die VvPGIPenkoderende geen is gevolglik na Nicotiana tabacum oorgedra vir hoëvlakuitdrukking van VvPGIP. Daar is gevind dat hierdie transgeniese plante minder vatbaar vir Botrytis cinerea-infeksies was in ‘n inisiële antifungiese toets wat gebruik gemaak het van blaarweefsel wat van die moederplant verwyder is. Daar is ook ‘n korrelasie gevind tussen B. cinerea-siekteweerstand en ePG-inhibisie deur proteïenekstrakte van die transgeniese populasie. Die huidige studie bou voort op en bevestig vorige bevindinge betreffende die antfungiese aard van die heteroloë PGIP in die heelplant en oor tyd. Ses transgeniese tabaklyne en 'n ongetransformeerde wilde-tipe (WT) is geïnfekteer en die lesies is vanaf dag drie tot sewe, en weer op dag 15, gemeet. Die transgeniese lyne het in die tydperk van drie tot sewe dae ná-inokulasie kleiner lesies as die WT getoon, alhoewel hierdie verskille slegs statisties beduidend geword het na sewe dae van inkubasie. Op daardie tydstip het vier van die ses lyne aansienlik kleiner lesies as die WT getoon, en verlagings in siektevatbaarheid het, in vergelyking met die WT, van 46% tot 69% gewissel. Twee van die lyne het siektevatbaarheid getoon wat vergelykbaar was met dié van die WT. In die siekteweerstandbiedende plantlyne was daar 'n verband tussen Vvpgip1-ekspressie, PGIP-aktiwiteit en ePG-inhibisie. Hierdie plantlyne is dus as PGIP-spesifieke siekteweerstandslyne beskou en dien dus as ideale eksperimentele bronne vir die ontleding van die moontlike in plantafunksies van PGIP in plantsiekteweerstandbiedendheid. Die huidige hipotese betreffende die funksie(s) van PGIP in plantsiekteweerstand is tweeledig. Eerstens het PGIP die vermoë om fungusePG's spesifiek en doeltreffend te inhibeer. Hierdie direkte inhibisie veroorsaak ‘n vermindering in patogenisiteit van die fungus op die gasheer. Indien ePG's egter hulle ensimatiese aksie onverstoord voortsit, sal weefseldegradasie en uiteindelik weefselnekrose die gevolg wees. Daar kon ook bewys word dat die in vitroinhibisie van ePG's deur PGIP die leeftyd van oligogalakturoniede, molekules wat die vermoë het om die plantweerstandsrespons aan te skakel, kan verleng. PGIP het dus nie net die vermoë om ePG's, en dus weefseldegradasie, te inhibeer nie; maar hierdie inhibisie lei ook daartoe dat plantweerstandsresponse aangeskakel word met die oog op die vermindering van patogeenindringing. Verskeie publikasies het reeds gerapporteer oor verminderde Botrytisvatbaarheid in PGIP transgeniese plantlyne. Geeneen van hierdie publikasies kon egter uitbrei op die huidige hipotese aangaande die moontlike in planta-funksie van PGIP in plantsiekteweerstand nie. In hierdie studie is transgeniese tabaklyne wat PGIP ooruitgedruk gebruik om hierdie moontlike in planta-funksies vir PGIP uit te klaar. Transkriptoom- en hormonale analises is op hierdie plantlyne en ‘n WT voor en ná inokulasie met die nekrotroof Botrytis cinerea uitgevoer,. Transkriptoomanalises is uitgevoer op ongeïnfekteerde, sowel as geïnfekteerde tabakblaarmateriaal deur gebruik te maak van ‘n Solanum tuberosum-mikroraster. Die analises met gesonde, ongeïnfekteerde plantmateriaal het daarop gewys dat gene betrokke by selwandmetabolisme tussen die transgeniese lyne en die WT verskillend uitgedruk was. Dit kon bewys word dat, sonder infeksiedruk, die geen wat xiloglukaan-endotransglikosilase (XET) kodeer, in die transgeniese lyne afgereguleer was. Gene wat betrokke is in die lignien-biosintetiese pad was ook in die individuele transgeniese lyne beïnvloed. Biochemiese toetse het ook die aanduiding van verhoogde ligniendeposisie in die transgeniese lyne se selwande bevestig. Addisionele fitohormoonprofiele het getoon dat hierdie lyne ook beskik oor verhoogde vlakke van indoolasynsuur (IAA). Hierdie resultate wys daarop dat konstitutiewe vlakke van PGIP selwandmetabolisme in die Vvpgip1-transgeniese lyne moontlik kan beïnvloed, wat plantsiekteweerstand in dié lyne positief kan beïnvloed. Dit wil dus voorkom asof PGIP 'n bykomende funksie in plantsiekteweerstand het. Plantweerstandsreponse kan direk deur PGIP beïnvloed word, wat tot die versterking van plantselwande kan lei; dit kan geskied by wyse van die strukturele eienskappe van die proteïen of die integrasie daarvan in die selwand. Hierdie selwande is dus “voorberei” alvorens patogeenindringing plaasvind en kon bydra tot die verminderde siektevatbaarheid wat waargeneem is in lyne wat hoë vlakke van PGIP akkumuleer. Transkriptoom- en hormonale analises is ook uitgevoer op Botrytisgeïnfekteerde blaarmateriaal van beide die transgeniese lyne en ‘n WT. Verskeie Botrytis-responsgene is in beide die transgeniese lyne en die WT opgereguleer. Differensïele geenekspressie tussen die twee genotipes was taamlik beperk, maar in die analises kon ‘n geen geïdentifiseer word wat tweevoudig in die transgeniese lyne opgereguleer was in vergelyking met die WT. Hierdie resultaat is ook bevestig met behulp van die “Real-Time” Polimerasekettingreaksie (PKR). Hierdie geen is betrokke in die lipoksigenase (LOX) -pad (spesifiek die 9-LOXarm), wat tot die sintese van die diviniel-eter oksilipiene “colneleic-” en “colnelenic”-suur lei. Daar is al bewys dat hierdie twee verbindings Botrytisspoorontkieming kan inhibeer. Fitohormoonprofiele van die geïnfekteerde plante het gewys dat die transgeniese lyne verhoogde vlakke van die poel van jasmonate wat plantsiekteweerstands-hormone is, ná inokulasie akkumuleer. Hierdie hormone word in die 13-LOX-arm van die lipoksigenase pad gevorm en is belangrik vir die beperking van Botrytis by die infeksiesetel. Die resultate van die analises wat op Botrytis-infeksie volg, dui daarop dat beide arms van die lipoksigenasepad in die transgeniese lyne verskillend by die lokale respons geïnduseer word. ‘n Verhoogde induksie van ‘n ander plantsiekteweerstandshormoon, salisielsuur, kon ook opgemerk word, alhoewel die totaal geakkumuleerde vlakke nie beduidend hoër was as dié van die WT nie. Hierdie resultate is die eerste wat onderskeidende induksie van ‘n siekteweerstandspad in enige van die pgip-ooruitgedrukte plantlyne rapporteer. Daarmee ondersteun dit ook die hipotese dat, seintransduksie wat plantweerstandsresponse aanskakel, ná inhibisie van ePG deur PGIP plaasvind. Die resultate wat met hierdie studie verkry is, dra dus beduidend by tot die huidige kennis van die in planta-funksie van PGIP in plantsiekteweerstandsresponse.
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Pretorius, Rudolph Johannes. "A plant health management system for aphididae on lettuce under variable shadehouse conditions in the central Free State, South Africa." Thesis, Bloemfontein : Central University of Technology, Free State, 2008. http://hdl.handle.net/11462/114.
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Thesis (M. Tech) --Central University of Technology, Free State, 2008Aphids (Hemiptera: Aphididae) are amongst the most destructive insects in agricultural crop production systems. This reputation stems from their complex life cycles which are mostly linked to a parthenogenetic mode of reproduction, allowing them to reach immense population sizes within a short period of time. They are also notorious as important and efficient vectors of several plant viral diseases. Their short fecund life cycles allow them to be pests on crops with a short growth period, e.g. lettuce (Lactuca sativa L.). It is common practice to provide this crop with some degree of protection from environmental extremes on the South African Highveld. Shadehouses are popular in this regard, but aphids are small enough to find their way into these structures, and their presence on lettuce is discouraged due to phytosanitary issues. In addition, the excessive use of insecticides is criticized due to the negative influence on human health, and because aphids can rapidly develop resistance. This necessitates the use of alternative control options in order to suppress aphid numbers. Biological control is popular in this regard and the use of predatory ladybirds (Coleoptera: Coccinellidae) is a popular choice. This study investigated the aphid and coccinellid species complex encountered under varying shadehouse conditions on cultivated head lettuce in the central Free State Province (South Africa). Their seasonality was also examined, along with variations in their population size throughout a one-year period. Finally, the impact of varying aphid populations on some physical characteristics of head lettuce was examined, and recommendations for aphid control (using naturally occurring coccinellid predators) were made. Two shadehouse structures were evaluated during this study. One was fully covered with shade netting and designed to exclude the pugnacious ant, Anoplolepis custodiens (Hymenoptera: Formicidae), while the other was partially covered with shade netting (on the roof area) allowing access to the ants. Six cycles of head lettuce were planted and sampled four times during each cycle. These were scheduled to monitor the seedling, vegetative and heading stage of lettuce. Four important aphid species were recorded on the lettuce, namely Acyrthosiphon lactucae, Nasonovia ribisnigri, Myzus persicae and Macrosiphum euphorbiae. Both structures harboured similar aphid and coccinellid species, but their population dynamics differed. A. lactucae dominated in the absence of A. custodiens in the fully covered structure (whole study), while N. ribisnigri dominated in the partially covered structure in the presence of these ants during the warmer months (December – January). M. euphorbiae replaced this species as the dominant species in the absence of A. custodiens (April – September). M. persicae occured during the winter (May – August) in the fully covered structure. Promising coccinellid predators were Hippodamia variegata and Scymnus sp. 1, and to a lesser extent, Exochomus flavipes and Cheilomenes lunata. However, the fully covered structure hampered the entrance of the larger adult coccinellid species, resulting in their lower occurrence. Aphid and coccinellid activity peaked during the summer months (October – January), and the fully covered structure attained the highest aphid infestation levels and coccinellid larval numbers during this time. On the other hand, aphid numbers were higher in the partially covered structure during the cooler months of the year (April – July) and this structure also harboured more adult coccinellids. In most cases, aphid infestation levels did not affect the amount of leaves formed. However, symptomatic damage in terms of head weight reduction did occur under severe infestation levels. Specific environmental conditions within a shadehouse structure concurrently contributed to this reduction, with less favourable conditions accelerating this condition. Results from this study have shown that even though the type of shadehouse structure does not influence the insect species complex found on lettuce, it does have an influence on detrimental and beneficial insect population dynamics. Aphid species infesting lettuce have been identified, along with coccinellid predators that could potentially be used in their control. Both types of structures had advantages and disadvantages, and therefore, decisions concerning shadehouses should not be focused on which type of structure to use, but rather which type of structure to use during different seasons of the year.
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Helps, Joseph Christopher. "Cultivar mixtures and the control of plant pathogens." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708199.
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Kay, Stuart James. "The biological control of sapstain of Pinus radiata with microorganisms." Thesis, University of Auckland, 1995. http://hdl.handle.net/2292/2474.
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A total of six hundred and sixteen fungal and two hundred and thirty two bacterial isolates were obtained either from the sapwood of Pinus radiata or from other sources, including UV mutagenesis. All isolates were screened on Pinus radiata wood chips for their survival and colonisation attributes. Of these isolates, two hundred and eighty two failed to grow or caused permanent deep seated discolourations or decay and were eliminated from the study. The remaining five hundred and sixty six isolates were assessed for their antagonistic ability against sapstain. In a dual screen on Pinus radiata wood chips, one hundred and twelve fungal and four bacterial isolates inhibited the growth of the known sapstain fungus, Ophiostoma piceae. In a second biological control screen, on Pinus radiata wood blocks, isolates of Gliocladium viride, Gliocladium roseum, Trichoderma hamatum, Trichoderma harzianum, Trichoderma sp., Trichothecium roseum and an isolate of the Thelephoraceae proved inhibitory to the sapstain isolates Ophiostoma piceae and Sphaeropsis sapinea providing between 94 and 100% control. These isolates were considered for further examination in the field. The remaining isolates provided poor or inconsistent inhibition or were mould fungi and, therefore, not suitable for direct application. All fungal and bacterial isolates that had shown inhibitory ability in the initial biological control screen and the remaining non-staining bacteria were examined for their ability to produce non-volatile metabolites that were inhibitory to sapstain. The bacterial isolates were examined in a preliminary dual plate screen in which 91 isolates were identified as producing inhibitory compounds. The best of these bacterial isolates were screened, with the fungal isolates, in a non-volatile metabolite trial utilising filter sterilised culture filtrates. Isolates of Bacillus sp., Fusarium solani, Gliocladium roseum, Gliocladium virens, Trichoderma harzianum, Trichoderma sp., Trichoderma viride and Trichothecium roseum were found to be significantly inhibitory to the growth of Ophiostoma piceae at concentrations of 50% or less. However, the filtrates did not provide adequate sapstain control, when tested on Pinus radiata wood block, to prompt consideration for further examination in the field. Studies are currently examining several of these isolates for the production of biologically active compounds. The six most promising isolates, from the wood chip and wood block trials, were tested in the field for their ability to control sapstain on unseasoned Pinus radiata sapwood and/or peeled logs. These were Gliocladium viride (FK75), Trichoderma hamantum (FK561), Trichoderma harzianum (FK228), Trichoderma sp. (FK247), Trichothecium roseum (FK238) and an isolate of the Thelephoraceae (FK33). The fungi were prepared as mycelial/spore homogenates. For application to the timber, the homogenates were mixed with 0.2% Alcosorb gel, producing 108 cfu/ml suspensions, these suspensions were applied by dipping. Diluted homogenates, 108 cfu/ml, were applied as spray treatments to the logs. All of the biological control agent treatments reduced the level of sapstain on either the logs or timber with Trichoderma harzianum (FK228), Trichoderma sp. (FK247) and Trichothecium roseum (FK238) providing control equivalent to that of the fungicides NP-1 and Diffusol for portions of the trial. Trichoderma sp. (FK247) and Trichothecium roseum (FK238) gave sapstain control in excess of 90% for the first 30 days of the timber trial equalling the control provided by NP-1 and Diffusol. In another trial, Trichoderma harzianum (FK228) was more effective than NP-1, providing 60% sapstain control, after six months, on the internal tissue of Pinus radiata logs. The six isolates selected for the field trials were examined in additional studies. In a dual inoculation study, Trichoderma sp. (FK247) exhibited localised antibiotic ability causing the lysis of mycelium of sapstain fungi. There was no evidence of mycoparasitic action by any of the six isolates. Trichoderma harzianum (FK228), Trichoderma sp. (FK247) and Trichothecium roseum (FK238) were observed to degrade cellulose. However, neither these nor the other isolates caused a significant change in the mechanical properties of Pinus radiata timber when compared to untreated controls. Decreasing pH or the addition of nitrate were identified as having potential for the promotion of biological control agent growth. The potential of mixed biological control agent inoculations was also examined. While these results are preliminary, they are extremely encouraging and provide a basis from which future studies can develop.
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Morin, Louise. "Development of the field bindweed bioherbicide, Phomopsis convolvulus : spore production and disease development." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59614.
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Phomopsis convolvulus Ormeno, a foliar pathogen of field bindweed, is a good candidate to be developed as a bioherbicide. Large numbers of infective propagules were produced in shake-flask liquid fermentation with modified Richard's (V-8) medium and in solid-substrate fermentation with pearl barley grains. In complex liquid media, pycnidium-like structures were observed. Most conidia stored at $-$70$ sp circ$C remained viable and virulent for at least six months.In controlled environment studies, a minimum of 18 hr of dew was required for severe disease development on inoculated plants. The addition of gelatin, Sorbo $ sp{ rm TM}$, or BOND$ sp{ rm TM}$ to the inoculum did not enhance the disease under various leaf wetness periods. A continuous dew period of 18 hr was superior to the cumulative effect of three interrupted 6 hr dew periods. Secondary inoculum was produced on diseased plants placed under moist conditions for 48 hr or more.
In greenhouse experiments, seedlings at the cotyledon and 3- to 5- leaf stage were severely diseased and killed when inoculated with 10$ sp9$ conidia/m$ sp2$. This inoculum density adversely affected the regenerative ability of 4 wk old seedlings and established plants, but few plants were killed. Inoculation of the healthy regrowth from plants previously inoculated with the fungus resulted in much less disease symptoms than expected.
Books on the topic "Phytopathogenic microorganisms Biological control"
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S, Gnanamanickam S., ed. Biological control of crop diseases. New York: M. Dekker, 2002.
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Dale, Walters, ed. Disease control in crops: Biological and environmentally-friendly approaches. Oxford, UK: Wiley-Blackwell, 2009.
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1954-, Boland Greg J., and Kuykendall L. David 1952-, eds. Plant-microbe interactions and biological control. New York: Marcel Dekker, 1997.
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1939-, Chet Ilan, ed. Innovative approaches to plant disease control. New York: Wiley, 1987.
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International Symposium on Biological Control of Plant Diseases for the New Century--Mode of Action and Application Technology (2001 Taichung, Taiwan). Proceedings of the International Symposium on Biological Control of Plant Diseases for the New Century--Mode of Action and Application Technology. Taichung: Dept. of Plant Pathology, National Chung Hsing University, 2001.
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Rice, Elroy L. Biological control of weeds and plant diseases: Advances in applied allelopathy. Norman: University of Oklahoma Press, 1995.
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Finckh, Maria R., Ariena H. C. van Bruggen, and Lucius Tamm. Plant diseases and their management in organic agriculture. St. Paul, Minnesota: The American Phytopathological Society, 2015.
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G, Mukerji K., Chamola B. P, and Upadhyay R. K. 1953-, eds. Biotechnological approaches in biocontrol of plant pathogens. New York: Kluwer Academic/Plenum Publishers, 1999.
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Campbell, R. E. Biological control of microbial plant pathogens. Cambridge: Cambridge University Press, 1989.
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Agriculture, National Research Council (U S. ). Committee on Biological Control Research Needs and Priorities in Plant-Microbe Interactions in. The ecology of plant-associated microorganisms: Basic research needed to support development of biological control of plant diseases. Washington, D.C: National Academy Press, 1989.
Find full textBook chapters on the topic "Phytopathogenic microorganisms Biological control"
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Rhodes, D. J. "Formulation of biological control agents." In Exploitation of Microorganisms, 411–39. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1532-2_16.
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Selari, Priscila Jane Romano Gonçalves, Sarina Tsui, Tiago Tognolli de Almeida, Luiz Ricardo Olchanheski, and Manuella Nôbrega Dourado. "Biological Control of Phytopathogenic Fungi: Mechanisms and Potentials." In Agricultural Biocatalysis, 3–39. New York: Jenny Stanford Publishing, 2022. http://dx.doi.org/10.1201/9781003313144-2.
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TeBeest, D. O. "Biological control of weeds with fungal plant pathogens." In Exploitation of Microorganisms, 1–17. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1532-2_1.
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Weeks, Richard, and Michael Leonidas Chikindas. "Biological Control of Food-Challenging Microorganisms." In Food Microbiology, 733–54. Washington, DC, USA: ASM Press, 2019. http://dx.doi.org/10.1128/9781555819972.ch28.
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Pérez-García, Alejandro, Diego Romero, Houda Zeriouh, and Antonio de Vicente. "Biological Control of Phytopathogenic Fungi by Aerobic Endospore-Formers." In Soil Biology, 157–80. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-19577-8_8.
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Li, Juan, James Borneman, Paul Ruegger, Lianming Liang, and Ke-Qin Zhang. "Molecular Mechanisms of the Interactions Between Nematodes and Nematophagous Microorganisms." In Progress in Biological Control, 421–41. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-51034-3_16.
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Guigón López, César, Héctor Adrián García Ramírez, and Laila Nayzzel Muñoz Castellanos. "Control of Pepper Powdery Mildew Using Antagonistic Microorganisms: An Integral Proposal." In Progress in Biological Control, 385–420. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-51034-3_15.
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Sindhu, Satyavir S., and Anju Sehrawat. "Rhizosphere Microorganisms: Application of Plant Beneficial Microbes in Biological Control of Weeds." In Microorganisms for Sustainability, 391–430. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-6241-4_19.
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Parulekar-Berde, Chanda Vikrant, Sujog Ashok Joshi, and Vikrant Balkrishna Berde. "Fungal Communities as Biological Control Agents for Different Phytopathogenic Organisms." In Fungal Biology, 189–201. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-60659-6_8.
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Kerry, Brian. "The use of microbial agents for the biological control of plant parasitic nematodes." In Exploitation of Microorganisms, 81–104. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1532-2_4.
Full textConference papers on the topic "Phytopathogenic microorganisms Biological control"
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Vasilchenko, N. G., A. V. Gorovtsov, V. A. Chistyakov, and M. S. Mazanko. "BACTERIA OF THE ORDER BACILLALES AS PROMISING ANTAGONISTS OF FUSARIUM PATHOGENS AND THEIR IMPACT ON WINTER WHEAT PLANTS." In INNOVATIVE TECHNOLOGIES IN SCIENCE AND EDUCATION. DSTU-Print, 2020. http://dx.doi.org/10.23947/itno.2020.324-327.
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The possibility of using bacteria of the order Bacillales as agents of biological control of phytopathogenic fungi of the genus Fusarium was studied. In the work, 28 soil samples were studied, from which antagonist bacterial strains were isolated. Antagonism was detected by cultivating a pasteurized soil suspension with a culture of the fungus Fusarium graminearum on wort agar. In the course of this work, 1040 antagonist bacterial strains were isolated. Subsequently, the influence of the selected strains of microorganisms on the germination winter wheat seeds and several other morphometric parameters was studied.
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Янковская, Е., Дмитрий Войтка, М. Федорович, and А. Михнюк. "Антагонистическая активность энтомопатогенных грибов в отношении фитопатогенных микромицетов." In VIIth International Scientific Conference “Genetics, Physiology and Plant Breeding”. Institute of Genetics, Physiology and Plant Protection, Republic of Moldova, 2021. http://dx.doi.org/10.53040/gppb7.2021.85.
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The researches on evaluation the influence of entomopathogenic fungi of the genuses Beauveria, Isaria and Lecanicillium influence on phytopathogenic microorganisms Alternaria solani, Botrytis ciner-ea, Sclerotinia sclerotiorum, Rhizoctonia solani, Fusarium solani, Phytophtora alni are presented. The antifungal peculiarities of tested strains – a potential basis of complex action biological preparations for plant protection are shown in vitro. The highest level of antagonistic activity has been revealed in strains Beauveria brongniartii МХ, Lecanicillium sp. аph and Isaria fumosorosea 21-2.
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Zhenchenko, K. G., E. N. Turin, and A. A. Gongalo. "Effect of Pisum sativum L. seed treatment with the complex of microbiological preparation on the plants’ growth and development under direct sowing." In РАЦИОНАЛЬНОЕ ИСПОЛЬЗОВАНИЕ ПРИРОДНЫХ РЕСУРСОВ В АГРОЦЕНОЗАХ. Federal State Budget Scientific Institution “Research Institute of Agriculture of Crimea”, 2020. http://dx.doi.org/10.33952/2542-0720-15.05.2020.27.
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We studied the use of the complex microbial preparation (CMP) in 2016-2018 at the experimental field of the Research Institute of Agriculture of Crimea. The soil is southern chernozem. Long-term annual precipitation – 428 mm; long-term annual air temperature – 12 °С. Pisum sativum L. variety – ‘Madonna’. Chemical treating agent Vitavax 200 FF (water suspension concentrate) at the rate of 0.75 l/ha was used in the control variant. Seeds were inoculated with CMP on the day of planting (FSBSI “Research Institute of Agriculture of Crimea” is the owner of CMP). The composition of the studied complex – 1) symbiotic nitrogen fixers; 2) phosphorus mobilizing microorganisms; 3) microorganisms that inhibit the growth and development of phytopathogenic bacteria and fungi. On average, over three years of research, the height of pea plants was the same and amounted to 82.3 cm in the control and 80.7 cm in the experimental variant. The symbiosis of PS and CMP had a significant effect on the number of beans per plant. In the control, 7.6 pieces were formed; under the influence of CMP – 8.6. In our experiments, the grain size was influenced both by the conditions of the growing season in a particular year and the treatment with CMP. The most favorable conditions were in 2016, which contributed to the largest 1000-grain weight (on average 284 g). In extremely arid 2018, the smallest peas were formed (1000-grain weight – 258 g). On average for 2016-2018, the yield in the variant with inoculation was 0.2 t/ha higher. The small Pisum sativum L. yield in 2018 can be explained by the low air humidity and the absence of productive precipitation.
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Lukjanova, Е. А., А. N. Sysoeva, D. А. Ivasenko, D. А. Ivasenko, and Y. А. Frank. "EFFECT OF THE “BIOBAKT “MICROCLIMATE” BIOLOGICAL PREPARATION ON MICROFLORA OF INDOOR LIVESTOCK FARM SECTIONS." In STATE AND DEVELOPMENT PROSPECTS OF AGRIBUSINESS. DSTU-PRINT, 2020. http://dx.doi.org/10.23947/interagro.2020.1.683-685.
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Experiments were performed to evaluate the effect of the biological preparation "BioBact" Microclimate" based on Bacillus subtilis D18 on the microflora of indoor livestock farm sections. Experimental treatment of farrowing sections was carried out at one of the livestock farms in Tomsk region, West Siberia. Monitoring of the sanitary-indicative microorganisms counts revealed a decrease in the total aerobic microbial counts, number of E. coli group bacteria, enteric bacteria and Staphylococcus spp. in the experimental sections of the livestock farm compared to control conditions.
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Soldatenko, E. A. "PIG COLIBACTERIOSIS IN THE CONDITIONS OF INDUSTRIAL COMPLEXES AND MEASURES TO COMBAT THIS DISEASE." In DIGEST OF ARTICLES ALL-RUSSIAN (NATIONAL) SCIENTIFIC AND PRACTICAL CONFERENCE "CURRENT ISSUES OF VETERINARY MEDICINE: EDUCATION, SCIENCE, PRACTICE", DEDICATED TO THE 190TH ANNIVERSARY FROM THE BIRTH OF A.P. Stepanova. Publishing house of RGAU - MSHA, 2021. http://dx.doi.org/10.26897/978-5-9675-1853-9-2021-22.
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In modern conditions of pig breeding, an epizootic situation is developing when constantly evolving strains of microorganisms with varying virulence are isolated from animals, which are not included in the composition of vaccines manufactured at biological enterprises. Therefore, polyvalent vaccines against porcine Escherichiosis were prepared from local strains circulating in animals of large pig breeding enterprises. The use of manufactured inactivated vaccines from local strains of Escherichia made it possible to reduce the incidence of young pigs compared with control from 6.0% to 0.5%, to provide newborn piglets with colostral immunity to strains of microorganisms circulating at the enterprise and to maintain a stable epizootic welfare of pig farms for colibacillosis.
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Shuliko, N. N. "THE BIOLOGICAL ACTIVITY OF THE RHIZOSPHERE OF SPRING BARLEY UNDER THE APPLICATION OF FERTILIZERS IN THE CONDITIONS OF THE SOUTHERN FOREST STEPPE OF WESTERN SIBERIA." In 11-я Всероссийская конференция молодых учёных и специалистов «Актуальные вопросы биологии, селекции, технологии возделывания и переработки сельскохозяйственных культур». V.S. Pustovoit All-Russian Research Institute of Oil Crops, 2021. http://dx.doi.org/10.25230/conf11-2021-270-274.
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The biological activity of the rhizosphere soil increased upon the application of mineral fertilizers (N18P42) and their combination with straw (N18P42 + straw) by 58 and 70 %, in comparison to the control. Of the three studied factors, the application of mineral fertilizers had the highest positive effect on the number of microorganisms in the barley rhizosphere, both separately and in combination with the studied factors.
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Chaikovskaya, L. A., V. V. Klyuchenko, M. I. Baranskaya, and O. L. Ovsienko. "Influence of microbial preparations and mineral fertilizers on the yield and quality of winter wheat grain." In CURRENT STATE, PROBLEMS AND PROSPECTS OF THE DEVELOPMENT OF AGRARIAN SCIENCE. Federal State Budget Scientific Institution “Research Institute of Agriculture of Crimea”, 2020. http://dx.doi.org/10.33952/2542-0720-2020-5-9-10-116.
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The use of biological products based on effective strains of microorganisms with a range of useful properties is one of the aspects of biological farming. The long-term field experiments were conducted in the soil and climatic conditions of the Crimea. А positive effect of the combined use of mineral fertilizers (NPK calculated at P30) and pre-sown inoculation of seeds (biopreparation based on L. nimipressuralis CCM 32-3) on the yield and quality of winter wheat grain was shown. The increase in grain productivity of winter wheat by 31 % compared to control (on average for 3 years) and grain quality indicators: protein and gluten – up to 12.5% and 28.0 % (in the control 9.9% and 19.2%, respectively) was revealed.
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Kruteakova, V., Nina V. Pilyak, V. Dishliuk, and O. Nikipelova. "The influence of bioderified on the basis of urban wastewater sediments on agricultural productivity on the example of corn on grain." In International Scientific Symposium "Plant Protection – Achievements and Prospects". Institute of Genetics, Physiology and Plant Protection, Republic of Moldova, 2020. http://dx.doi.org/10.53040/9789975347204.27.
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Sewage sludge (SS) is a secondary resource that can be used in modern biotechnology to produce fertilizers. This is the bioconversion of organic waste – obtaining available organic raw materials (compost) with the participation of phosphate-mobilizing microorganisms with the addition of fillers. Biofertilizers based on SS of biological treatment plants (SBU) "Southern" and "Northern" of Odessa with different fillers (winter wheat straw and sunflower seed husk) were studied. The effectiveness of biofertilizers was studied in a field experiment on chernozem ordinary medium humus. Culture in the experiment: corn for grain (medium-ripe hybrid FAO 400). According to the results of determining the biological activity of the soil, the highest indicators of corn yield are shown when using new biofertilizers in comparison with the control, which provided an increase in corn yield per grain and improved economic performance.
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Shi, Xiang, Julia R. de Rezende, and Kenneth Sorbie. "Microbial Ecology Metrics to Assess the Effect of Biocide on Souring Control and Improve Souring Modelling." In SPE International Oilfield Corrosion Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205037-ms.
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Abstract Reservoir souring is a long-standing issue for the oil and gas industry caused by sulfate-reducing microorganisms (SRM) producing H2S from sulfate ions. In this work, we investigated the connections between the development of souring and the change in three key microbial ecology metrics: the abundance, alpha diversity and community structure of a souring microbiota under the biocide treatment of 100 ppm glutaraldehyde (henceforth referred to as GA). These are studied in sand-packed flow-through bioreactors during and after the biocide treatment using cutting-edge DNA assays. Our study suggests that the rebound of microbial sulfide production after the 100 ppm GA treatment is closely associated with the recovery in microbial abundance and microbial alpha diversity. The study also shows that 100 ppm GA treatment may lead to a measurable shift in the SRM community structure. By comparing the effluent microbial community with the sand microbial community, the study suggests that the change in alpha diversity of the produced water microbial community might be an early warning for the sulfide breakthrough due to souring recurrence in practice. This work explores the relationship between souring and the underlining microbial community behaviours in response to the 100 ppm GA treatment and, to characterise these changes, we propose measurable metrics. A conceptual model is also proposed describing the near-term biological process behind the biocide treatment-recovery cycle in a souring scenario. Finally, this work highlights the potential applications and caveats of harnessing the increasingly available field microbial community data for the improvement of souring modelling and field souring control strategies.
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Mikhailouskaya, N. A., D. V. Voitka, E. K. Yuzefovich, and T. B. Barashenko. "Effect of three-component microbial inoculant on winter rye and spring barley yields." In РАЦИОНАЛЬНОЕ ИСПОЛЬЗОВАНИЕ ПРИРОДНЫХ РЕСУРСОВ В АГРОЦЕНОЗАХ. Federal State Budget Scientific Institution “Research Institute of Agriculture of Crimea”, 2020. http://dx.doi.org/10.33952/2542-0720-15.05.2020.17.
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One of the modern techniques of improving microbial preparations efficiency is a combination of several microorganisms with different beneficial properties in one inoculant. Taking into account the role of nitrogen and potassium nutrition and their synergism, it is essential to develop preparations of N2-fixing and K-mobilizing rhizobacteria, especially Azospirillum sp. and Bacillus sp. Effective biological control of root infections is of great importance in order to prevent crop yield losses. Among soil antagonistic fungi, Trichoderma sp. is the most promising one. Microbial inoculant includes three components: Azospirillum brasilеnse 2(b)3 + Bacillus circulans K-81 + Trichoderma longibrachiatum L-7 (1:1:1). Combined application of rhizobacteria A. brasilense + B. сirculans induced significant hormonal effect. Roots dry mass increased by 28%, roots length per plant – by 25%, stem dry mass – by 33%. In the field experiment, the treatment of barley by microbial inoculant provided the reduction of root rot incidence by 52.0–58.0%, disease development (waxy ripeness) – by 2.6–2.9 times, biological efficiency was 66.3–69.5%. Treatment of winter rye resulted in the reduction of disease incidence by 42.4–45.0%, disease development (milky ripeness) – by 2.0–2.6 times, biological efficiency – 50.2–61.2% according to soil-erosion catena. Beneficial influence of inoculation on plant development and nutrition, as well as effective biological control of plant diseases, provided significant crop responses: for winter rye – 3.8-4.5 c ha-1 or 7.0% - 9.8%, for spring barley – 5,2 – 4.9 c ha-1 or 9.3% – 9.2% according to soil-erosion catena. Microbial inoculant exhibits the properties of plant growth promoter, biological fertilizer, and biological fungicide.
Reports on the topic "Phytopathogenic microorganisms Biological control"
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Cytryn, Eddie, Mark R. Liles, and Omer Frenkel. Mining multidrug-resistant desert soil bacteria for biocontrol activity and biologically-active compounds. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7598174.bard.
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Control of agro-associated pathogens is becoming increasingly difficult due to increased resistance and mounting restrictions on chemical pesticides and antibiotics. Likewise, in veterinary and human environments, there is increasing resistance of pathogens to currently available antibiotics requiring discovery of novel antibiotic compounds. These drawbacks necessitate discovery and application of microorganisms that can be used as biocontrol agents (BCAs) and the isolation of novel biologically-active compounds. This highly-synergistic one year project implemented an innovative pipeline aimed at detecting BCAs and associated biologically-active compounds, which included: (A) isolation of multidrug-resistant desert soil bacteria and root-associated bacteria from medicinal plants; (B) invitro screening of bacterial isolates against known plant, animal and human pathogens; (C) nextgeneration sequencing of isolates that displayed antagonistic activity against at least one of the model pathogens and (D) in-planta screening of promising BCAs in a model bean-Sclerotiumrolfsii system. The BCA genome data were examined for presence of: i) secondary metabolite encoding genes potentially linked to the anti-pathogenic activity of the isolates; and ii) rhizosphere competence-associated genes, associated with the capacity of microorganisms to successfully inhabit plant roots, and a prerequisite for the success of a soil amended BCA. Altogether, 56 phylogenetically-diverse isolates with bioactivity against bacterial, oomycete and fungal plant pathogens were identified. These strains were sent to Auburn University where bioassays against a panel of animal and human pathogens (including multi-drug resistant pathogenic strains such as A. baumannii 3806) were conducted. Nineteen isolates that showed substantial antagonistic activity against at least one of the screened pathogens were sequenced, assembled and subjected to bioinformatics analyses aimed at identifying secondary metabolite-encoding and rhizosphere competence-associated genes. The genome size of the bacteria ranged from 3.77 to 9.85 Mbp. All of the genomes were characterized by a plethora of secondary metabolite encoding genes including non-ribosomal peptide synthase, polyketidesynthases, lantipeptides, bacteriocins, terpenes and siderophores. While some of these genes were highly similar to documented genes, many were unique and therefore may encode for novel antagonistic compounds. Comparative genomic analysis of root-associated isolates with similar strains not isolated from root environments revealed genes encoding for several rhizospherecompetence- associated traits including urea utilization, chitin degradation, plant cell polymerdegradation, biofilm formation, mechanisms for iron, phosphorus and sulfur acquisition and antibiotic resistance. Our labs are currently writing a continuation of this feasibility study that proposes a unique pipeline for the detection of BCAs and biopesticides that can be used against phytopathogens. It will combine i) metabolomic screening of strains from our collection that contain unique secondary metabolite-encoding genes, in order to isolate novel antimicrobial compounds; ii) model plant-based experiments to assess the antagonistic capacities of selected BCAs toward selected phytopathogens; and iii) an innovative next-generation-sequencing based method to monitor the relative abundance and distribution of selected BCAs in field experiments in order to assess their persistence in natural agro-environments. We believe that this integrated approach will enable development of novel strains and compounds that can be used in large-scale operations.
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Werren, John H., Einat Zchori-Fein, and Moshe Coll. Parthenogenesis-Inducing Microorganisms in Parasitic Hymenoptera: Their Mode of Action and Utilization for Improvement of Biological Control Agents. United States Department of Agriculture, June 1996. http://dx.doi.org/10.32747/1996.7573080.bard.
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Wolbachia are intracellular bacteria known to cause reproductive and sex ratio disorders in many insects. In various parasitic Hymenoptera, Wolbachia induce thelytokous reproduction. The overall goal of this research was the improvement of biological control agents by reversion of their mode of reproduction. This was attempted from two directions: 1) studying the effect of naturally occurring Wolbachia on the thelytokous species Muscidifuraxuniraptor and 2) trying to transmit thelytoky-inducing Wolbachia to Nasoniavitripennis. In M. uniraptor, gamete duplication was found to be the mode of diploidy restoration and Wolbachia density had a strong effect on sex ratio but not on host fitness. Studies on the natural horizontal transmission of Wolbachia between Nasonia wasps and their Protocalliphora hosts using the Wolbachia Outer Surface Protein (WOSP) gene revealed that (a) two Nasonia species (N. giraulti and N. longicornis) possess closely related strains of B-group Wolbachia, but N. vitripennisapparently acquired B Wolbachia by horizontal transmission from an unknown source, (b) Nasonia and its Protocalliphora host have similar Wolbachia, and (c) the Protocalliphora Wolbachia WOSP gene is a recombinant between the one found in N. giraulti/longicornis and N. vitripennis. Results show parasitoid-host insect transmission of Wolbachia and recombination among Wolbachia strains. Results from gynandromorph studies suggest a novel mechanism of sex determination in Nasonia.
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Wilson, Charles, and Edo Chalutz. Biological Control of Postharvest Diseases of Citrus and Deciduous Fruit. United States Department of Agriculture, September 1991. http://dx.doi.org/10.32747/1991.7603518.bard.
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The objectives of this research were to develop control measures of postharvest diseases of citrus and deciduous fruits by using naturally-occurring, non-antibiotic-producing antagonists; study the mode of action of effective antagonists and optimize their application methods. Several antagonists were found against a variety of diseases of fruits and vegetables. One particularly effective yeast antagonist (US-7) was chosen for more in-depth studies. This antagonist outcompetes rot pathogens at the wound site for nutrients and space; it is better adapted than the pathogen to extreme environmental conditions such as temperature, humidity and osmotic changes, and is relatively resistant to common postharvest fungicides. Our data suggests that other modes of action may also be involved. These are induction of host resistance by the antagonists or its products, and direct interaction between the antagonists and the pathogen with the possible involvement of an extracellular material and/or cell wall degrading enzymes produced by the antagonist. However, these interactions were not fully elucidated. The antagonistic activity of US-7 and other biocontrol agents isolated, was enhanced by calcium salts. While the mode of action is not known, the addition of these salts had a significant effect both in laboratory experiments and in large-scale tests. Compatibility of the yeast antagonist with present packinghouse treatments and procedures was determined. An integrated control procedure was developed, utilizing the antagonists together with ultra-low dosages of fungicides and activity-enhancing additives. This cooperative research resulted in numerous publications describing the antagonistic agents. their mode of action and possible commercial application. Patents were developed from this research and a commercial company is pursuing the licensing of these patents and the testing of the procedure on a commercial scale. Our research findings have expanded the potential for using non-antibiotic-producing antagonistic microorganisms in the control of postharvest diseases of fruits and vegetables; thus meeting a critical need to find alternatives to the use of synthetic fungicides on food products.
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Lindow, Steven E., Shulamit Manulis, Dan Zutra, and Dan Gaash. Evaluation of Strategies and Implementation of Biological Control of Fire Blight. United States Department of Agriculture, July 1993. http://dx.doi.org/10.32747/1993.7568106.bard.
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The main objective of this study was to develop data that would facilitate a consistently effective method of biological control of fire blight disease to be developed and to enable its implementation for disease control by ensuring its compatibility with variations in the biological, environmental, and chemical conditions present in pear orchards. As considerable information on the pathogen and biological control of fire blight was already gathered from studies in California and elsewhere, an emphasis was placed on investigating the genetics and ecology of Erwinia amylovora, the causal agent of fire blight in Israel. Studies of plasmid profile, virulence on several host, serological characteristics, as well as DNA fingerprints with selected primers all revealed E. amylovora strains in Israel to be homogeneous. Strains did vary in their resistance to streptomycin, with those from more northern locations being resistant while those in the southern costal plain were all sensitive to streptomycin. Resistance appeared to be conferred by chromosomal mutations as in streptomycin-resistant strains in California. The biological control agent Pseudomonas fluorescens strain A506 colonized flowers of both the Costia and Spodona pear cultivars in Israel as well as Bartlett pear in California. Flowers that were open at the time of spray inoculation of trees subsequently harbored from 105 to 107 cells of strain A506 per flower, while those that opened subsequent to spraying developed population sizes of about 105 cells/flower within 5 days. The incidence of fire blight infections were reduced about 3-fold in several trials in which moderate amounts of disease occurred in the plot areas; this degree of biological control is similar to that observed in California and elsewhere. On two occasions warm and moist weather that favored disease led to epidemics in which nearly all flowers became infected and which was so severe that neither P. fluorescens strain A506 nor chemical bactericides reduced disease incidence. A novel method for identifying antagonistic microorganisms for biological control of fire blight and other diseases was developed. A bacterial ice nucleation gene was introduced into E. amylovora to confer an Ice+ phenotype and the population sizes of this modified pathogen on flowers that had been pre-treated with potential control agents was estimated by measuring the freezing temperature of colonized flowers. Antagonistic strains that prevented the growth of E. amylovora in flowers were readily detected as those in which flowers froze at a low temperature. The method is both rapid and unbiased and several bacterial strains with substantial biological control potential have been identified using this method.
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Lindow, Steven, Isaac Barash, and Shulamit Manulis. Relationship of Genes Conferring Epiphytic Fitness and Internal Multiplication in Plants in Erwinia herbicola. United States Department of Agriculture, July 2000. http://dx.doi.org/10.32747/2000.7573065.bard.
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Most bacterial plant pathogens colonize the surface of healthy plants as epiphytes before colonizing internally and initiating disease. The epiphytic phase of these pathogens is thus an important aspect of their epidemiology and a stage at which chemical and biological control is aimed. However, little is known of the genes and phenotypes that contribute to the ability of bacteria to grow on leaves and survive the variable physical environment in this habitat. In addition, while genes such as hrp awr and others which confer pathogenicity and in planta growth ability have been described, their contribution to other aspects of bacterial epidemiology such as epiphytic fitness have not been addressed. We hypothesized that bacterial genes conferring virulence or pathogenicity to plants also contribute to the epiphytic fitness of these bacteria and that many of these genes are preferentially located on plasmids. We addressed these hypotheses by independently identifying genes that contribute to epiphytic fitness, in planta growth, virulence and pathogenicity in the phytopathogenic bacterium Erwinia herbicola pv gypsophilae which causes gall formation on gypsophila. This species is highly epiphytically fit and has acquired a plasmid (pPATH) that contains numerous pathogenicity and virulence determinants, which we have found to also contribute to epiphytic fitness. We performed saturation transposon mutagenesis on pPATH as well as of the chromosome of E.h. gypsophilae, and identified mutants with reduced ability to grow in plants and/or cause disease symptoms, and through a novel competition assay, identified mutants less able to grow or survive on leaves. The number and identity of plasmid-borne hrp genes required for virulence was determined from an analysis of pPATH mutants, and the functional role of these genes in virulence was demonstrated. Likewise, other pPATH-encoded genes involved in IAA and cytokinin biosynthesis were characterized and their pattern of transcriptional activity was determined in planta. In both cases these genes involved in virulence were found to be induced in plant apoplasts. About half of avirulent mutants in pPATH were also epiphytically unfit whereas only about 10% of chromosomal mutants that were avirulent also had reduced epiphytic fitness. About 18% of random mutants in pPATH were avirulent in contrast to only 2.5% of random chromosomal mutants. Importantly, as many as 28% of pPATH mutants had lower epiphytic fitness while only about 10% of random chromosomal mutants had lower epiphytic fitness. These results support both of our original hypotheses, and indicate that genes important in a variety of interactions with plant have been enriched on mobile plasmids such as pPATH. The results also suggest that the ability of bacteria to colonize the surface of plants and to initiate infections in the interior of plants involves many of the same traits. These traits also appear to be under strong regulatory control, being expressed in response to the plant environment in many cases. It may be possible to alter the pattern of expression of such genes by altering the chemical environment of plants either by genetic means or by additional or chemical antagonists of the plant signals. The many novel bacterial genes identified in this study that are involved in plant interactions should be useful in further understanding of bacterial plant interactions.
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Droby, Samir, Joseph W. Eckert, Shulamit Manulis, and Rajesh K. Mehra. Ecology, Population Dynamics and Genetic Diversity of Epiphytic Yeast Antagonists of Postharvest Diseases of Fruits. United States Department of Agriculture, October 1994. http://dx.doi.org/10.32747/1994.7568777.bard.
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One of the emerging technologies is the use of microbial agents for the control of postharvest diseases of fruits and vegetables. A number of antagonistic microorganisms have been discovered which have the potential to effectively control postharvest diseases. Some of this technology has been patented and commercial products such as AspireTM (Ecogen Corporatin, Langhorne, PA, USA), Biosave 10TM and Biosave 11TM (Ecoscience Inc., Worchester, MA, USA) have been registered for commercial use. The principal investigator of this project was involved in developing the yeast-based biofungicide-AspireTM and testing its efficacy under commercial conditions. This research project was initiated to fill the gap between the knowledge available on development and commercial implementation of yeast biocontrol agents and basic understanding of various aspects related to introducing yeast antagonists to fruit surfaces, along with verification of population genetics. The main objectives of this study were: Study ecology, population dynamics and genetic diversity of the yeast antagonists Candida guilliermondii, C. oleophila, and Debaryomyces hansenii, and study the effect of preharvest application of the yeast antagonist C. oleophila naturally occurring epiphytic microbial population and on the development of postharvest diseases of citrus fruit during storage. Our findings, which were detailed in several publications, have shown that an epiphytic yeast population of grapefruit able to grow under high osmotic conditions and a wide range of temperatures was isolated and characterized for its biocontrol activity against green mold decay caused by Penicillium digitatum. Techniques based on random amplified polymorphic DNA (RAPD) and arbitrary primed polymerase chain reaction (ap-PCR), as well as homologies between sequences of the rDNA internal transcribed spacers (ITS) and 5.8S gene, were used to characterize the composition of the yeast population and to determine the genetic relationship among predominant yeast species. Epiphytic yeasts exhibiting the highest biocontrol activity against P. digitatum on grapefruit were identified as Candida guilliermondii, C. oleophila, C. sake, and Debaryomyces hansenii, while C. guilliermondii was the most predominant species. RAPD and ap-PCR analysis of the osmotolerant yeast population showed two different, major groups. The sequences of the ITS regions and the 5.8S gene of the yeast isolates, previously identified as belonging to different species, were found to be identical. Following the need to develop a genetically marked strain of the yeast C. oleophila, to be used in population dynamics studies, a transformation system for the yeast was developed. Histidine auxotrophy of C. oloephila produced using ethyl methanesulfonate were transformed with plasmids containing HIS3, HIS4 and HIS5 genes from Saccharomyces cerevisiae. In one mutant histidin auxotrophy was complemented by the HIS5 gene of S. cerevisiae is functionally homologous to the HIS5 gene in V. oleophila. Southern blot analysis showed that the plasmid containing the S. cerevisiae HIS5 gene was integrated at a different location every C. oleophila HIS+ transformant. There were no detectable physiological differences between C. oleophila strain I-182 and the transformants. The biological control ability of C. oleophila was not affected by the transformation. A genetically marked (with b-glucuronidase gene) transformant of C. oleophila colonized wounds on orange fruits and its population increased under field conditions. Effect of preharvest application of the yeast C. oleophila on population dynamics of epiphytic microbial population on wounded and unwounded grapefruit surface in the orchard and after harvest was also studied. In addition, the effect of preharvest application of the yeast C. oleophila on the development of postharvest decay was evaluated. Population studies conducted in the orchard showed that in control, non-treated fruit, colonization of wounded and unwounded grapefruit surface by naturally occurring filamentous fungi did not vary throughout the incubation period on the tree. On the other hand, colonization of intact and wounded fruit surface by naturally occurring yeasts was different. Yeasts colonized wounded surface rapidly and increased in numbers to about two orders of magnitude as compared to unwounded surface. On fruit treated with the yeast and kept on the tree, a different picture of fungal and yeast population had emerged. The detected fungal population on the yeast-treated intact surface was dramatically reduced and in treated wounds no fungi was detected. Yeast population on intact surface was relatively high immediately after the application of AspireTM and decreased to than 70% of that detected initially. In wounds, yeast population increased from 2.5 x 104 to about 4x106 after 72 hours of incubation at 20oC. Results of tests conducted to evaluate the effect of preharvest application of AspireTM on the development of postharvest decay indicated the validity of the approach.