Дисертації з теми "Plant salinity tolerance"

Wild Hordeum species, from the four genome groups of X, H, I and Y, were assessed for physiological traits associated with tolerance to salinity and waterlogging. When grown in saline conditions, a number of wild Hordeum species had exceptional ‘exclusion’ of Na+ and Cl- from the young leaves, and also maintained tissue K+ concentrations, compared with Hordum vulgare ssp. vulgare (cv. ‘Golf’). For example, at 150 mol m-3 NaCl, the K+:Na+ in youngest, fully expanded leaf blades of wild Hordeum species averaged 5.2, compared with 0.8 in H. vulgare. H. marinum was more salt tolerant than H. vulgare, with a relative growth rate 30% higher than H. vulgare at 150 mol m-3 NaCl. At 300 mol m-3 NaCl, glycinebetaine plus proline contributed to 15% of πsap in expanding leaf blades of H. marinum, compared with 8% in H. vulgare. When grown in stagnant conditions, 16 accessions (approximately half of those evaluated) formed a barrier to radial O2 loss (ROL) in basal zones of adventitious roots. In the Triticeae, this trait had previously only been described in one species, H. marinum. The barrier to ROL occurred only in accessions from wetland or intermediate habitats, and was also related to genome type, being present in accessions with the X or the H genome (Hordeum vulgare has the I genome). In stagnant conditions, aerenchyma formed was, on average; 22% in accessions with the X genome; 19% in those with the H genome; and 15 and 16% in those with the I or the Y genomes, respectively. The combination of a barrier to ROL and aerenchyma enhances longitudinal O2 movement in adventitious roots, permitting roots to penetrate deeper into anaerobic substrates. In H. marinum, induction of the barrier to ROL was associated with a 97% reduction in apparent O2 diffusivity across the external layers of the basal zones of roots, compared with near the root tip. The barrier results from physical resistance to radial O2 movement, although when roots were cooled to suppress respiration some additional leakage of O2 was detected, indicating respiration also contributes to the low rates of ROL from the basal regions of roots. Low radial O2 permeability in the roots of stagnantly-treated H. marinum was associated with secondary thickening, putatively lignin or suberin deposits, in the hypodermis. These changes in root structure, however, did not influence root hydraulic conductivity, assessed for individual adventitious roots and whole root systems. Thus, diversity amongst Hordeum species in expression of traits for tolerance to waterlogging (an inducible barrier to ROL and aerenchyma) and salinity (Na+ and Cl- ‘exclusion’) were documented in this study. Traits for root aeration did not compromise the capacity of roots to take up water, presumably being of importance for growth in soils with fluctuating water levels (i.e. wet/dry cycles). The high degree of salinity tolerance in several Hordeum species, and especially in H. marinum, is consistent with field observations that these species occur in salt affected areas

The possibility of manipulating calcium (Ca2+) and potassium (K+) levels in seeds of Brassica rapa by altering parent plant nutrition and investigating the potential for increased salinity tolerance during germination, given that considerable amounts of literature imply that greater amounts of available exogenous Ca2+ and K+ can ameliorate the effects of salinity on both whole plant growth and germination, was evaluated. The investigation consisted of four growth trials. Two preliminary growth trials suggested that seed ion manipulation was possible without affecting the overall growth and vigour of the plant. After developing suitable high and low Ca2+ and K+ nutrient solutions for growth, a trial was carried out in a growth room and greenhouse, with various substrates and the seed of a certain size category was collected for subsequent ion and salinity tolerance analysis. Seed Ca2+ and K+ was significantly affected by growth substrate and nutrient solution and data showed that a significant negative regression relationship existed between seed Ca2+, K+ and Ca2+ + K+ levels and salinity tolerance. Further experimentation using hydroponic culture attempted to remove any possible effects of substrate and also to compare size categories of seed with a view to elucidating localisation of Ca2+ and K+. Seed Ca2+ was found to be significantly altered by nutrient solution in the two different sizes tested and higher Ca2+ nutrient solution was found to increase salinity tolerance in daughter seed. One significant negative regression correlation between salinity tolerance and seed K+ concentration existed in smaller seed, but disregarding seed size in a regression analysis of seed ion content and salinity tolerance, a significant negative relationship existed between seed Ca2+, K+ and Ca2++ K+. The results, especially in terms of Ca2+ nutrition, contradict much previous research that suggests increased salinity tolerance at germination can arise with the increased presence of Ca2+ and/or K+. Salinity tolerance was greater in seeds of larger size across all nutritional treatments and the smaller size range exhibited increased Ca2+ and K+ per μg seed. Ca2+ concentration in smaller seeds with greater surface area:volume ratios provided a clue to the potential localisation of Ca2+. Cross sectional staining showed that a greater proportion of seed Ca2+ may reside in the coat. This was confirmed by analysis which showed an approximate 50% split of total extractable seed Ca2+, regardless of size, between coat and embryo within a seed; the majority of which, per μg, resides in the coat. Further work looked at the relative solubility of the Ca2+ and K+ in these tissues and whole seed to look at the potential bioavailability of Ca2+ during germination from various parts of the seed. Most water soluble Ca2+ exists in the embryo and most insoluble Ca2+ exists in the coat, but coat Ca2+ was found to be ionically exchangeable and therefore bioavailable. K+ appeared mostly water soluble in embryo and coat. In line with previous whole plant research in this species, most Ca2+ is readily water soluble or ionically exchangeable in form and the possible negative effects of how increasing bioavailable Ca2+ may reduce salinity tolerance was discussed.

Thesis (PhD(Agric) (Plant Biotechnology))--University of Stellenbosch, 2010.
Includes bibliography.
ENGLISH ABSTRACT: Salinity is one of the major limiting abiotic stresses on legume plant yield, leading to early senescence of root nodules. This occurs because of accumulation of reactive oxygen species (ROS) in plant cells under salinity stress. Concurrent with the increase in cellular reactive oxygen species levels is the increase in cellular antioxidants and corresponding antioxidant enzymes. This feature is observed mostly in the shoots and roots of more tolerant genotypes compared to the susceptible genotypes. It is accepted that the mechanism of plant tolerance to stress is dependent upon the response of the antioxidant systems. Most studies carried out on shoot tissues suggest that scavenging of ROS by the plant antioxidant system is modulated by nitric oxide (NO). However, the pathways by which NO mediates such antioxidant responses are not fully understood. For legumes, salinity stress has adverse effects on yield and this is in part due to inhibition of nitrogen fixation in the root nodules of the legumes, which causes severe nitrogen starvation in nitrogen-deficient soils. Nodules are specialized organs comprising of both the rhizobia and the plant tissue, hence the physiological aspects may vary from the findings from the leaves. It was therefore deemed necessary to establish the role of NO on the nodule antioxidant system in the absence and presence of salinity stress. For the purposes of this study, the effect of both exogenously applied NO and endogenous NO on superoxide dismutase, glutathione peroxidase and glutathione content was determined. The studies involved the use of nitric oxide donors like sodium nitroprusside (SNP) and diethylenetriamine/nitric oxide adduct (DETA/NO), their respective fixed controls potassium ferricyanide and diethylenetriamine (DETA), plus a nitric oxide synthase inhibitor (to inhibit nitric oxide production by the enzyme nitric oxide synthase) on nodulated roots. The data obtained in this work points out specifically at roles played by nitric oxide in regulating superoxide dismutases, glutathione peroxidase and glutathione during salinity stress and proposes a link between nitric oxide-mediated changes in these antioxidant systems and salinity stress tolerance. Both the exogenously applied and endogenous nitric oxide increases the enzyme activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and glutathione reductase (GR). However, there is both time dependency and nitric oxide concentration dependency on the enzyme activities. The total SOD enzyme activity increases upon nitric oxide exposure and with time of exposure. The individual SOD isoforms identified and studied in the root nodules all contribute to this increase in SOD activity upon nitric oxide treatment except for MnSOD I. This increase in activity is regulated at transcriptional level as the RT-PCR results targeting the individual isoforms reveals an increase in transcript levels after 6 hours of nitric oxide treatment. However, the CuZn SOD I isoform transcripts are reduced upon nitric oxide treatment. A similar response was also observed in GPX enzyme activity in which nitric oxide increased the GPX activity above all the controls. The GR enzyme activity exhibits an opposite response because the activity decreases with time of exposure to NO and concentration of NO. In order to determine the effect of NO under saline conditions, an experiment was set up that involved incubation of nodulated roots in solutions containing 150 mM NaCl. The stressed nodules exhibited generally higher levels of enzyme activities than the non-stressed nodules. Furthermore, exposure to nitric oxide donor in combination with NaCl induced even higher activities of SOD and GPX than NaCl or nitric oxide donor alone. There were also higher levels of reduced glutathione and total glutathione recorded under stress compared to optimal conditions. Nitric oxide increased the concentration of these forms of glutathione, suggesting an improved redox status based on the GSH/GSSG ratios under salinity stress in the presence of nitric oxide. Attenuation of nitric oxide synthesis with L-Nω-Nitroarginine methyl ester (L-NAME) reverses all the recorded effects of nitric oxide on antioxidant enzymes and glutathione pool. This was observed in salinity stressed nodules and non-stressed nodules. This work further establishes that NO plays a pivotal role in modulating the enzymatic activities through a pathway that is mediated by guanosine 3,5-cyclic monophosphate (cGMP). The experiment involving the inhibition of soluble guanylyl cyclase (sCG) (an enzyme that catalyzes the biosynthesis of cGMP), cell-permeable cGMP anaologue and L-NAME revealed that GPx activity is modulated through a cGMP-dependent pathway and NO is positioned up-stream of cGMP in the pathway leading to improved GPX activity. Cyclic GMP also modulates the GPX activity in a concentration dependent manner. NO improves the redox status of the cell under both saline conditions and non-saline conditions and this effect is modulated through a cGMP-dependent pathway. It is thus rational to conclude that; in the root nodules of legumes, like in other plant tissues, the increased accumulation of antioxidants and the increased activity of their corresponding enzymes, as modulated through the cGMP-dependent pathway by nitric oxide, confer root nodule tolerance to salinity. This concept directly points out at an attractive strategy for developing legumes that are genetically improved for enhanced root nodule tolerance to salinity; via differential regulation of antioxidants and antioxidant enzyme genes in the root nodules under abiotic stress. Towards attaining the goal for such genetic improvement, experiments involving construction of an abiotic stress-responsive and nodule-specific chimeric promoter were carried out. By fusing the 5-untranslated (5-UTR) region of the LEA gene that contains an abiotic stress-responsive cis-acting element (from theGmPM9 promoter) to the nodulin N23 promoter bearing the highly functional cluster of motifs for nodule specificity, the candidate nodule specific promoter that is abiotic stress responsive (ASREF/NSP) was constructed. The construct harbouring this ASREF/NSP chimeric promoter was fused to the -glucuronidase (GUS) reporter gene so as to study the functionality of the promoter in Medigaco truncatula plants. The construct was delivered into the Medicago plants through Agrobacterium rhyzogenes mediated transformation to produce composite Medicago plants. The transgenic roots have been cultured for futher manipulation and to confirm the functionality of the promoter. Furthermore several strategies can be deployed via the use of this chimeric promoter so as to enhance the nodular antioxidant system. This would involve either gene regulator-chimeric promoter fusion or the use of a single gene approach. As part of this work, the MtNOA gene homologous to AtNOAs, has been cloned from Medicago trancatula and put as ASREF/NSP fusion in a binary vector pBINPLUS and delivered into Medicago trancatula for nodule-specific and abiotic stress-induced nitric oxide synthesis. Since there is no plant NOS identified to date, the possibility of the use of a regulatory gene in this aspect is still limited. There are other options involving the use of the chimeric promoter with the individual genes encoding the antioxidant enzyme genes such as genes encoding SOD, GPX and the glutathione synthatase to enhance the plant antioxidant system during abiotic stress.
AFRIKAANSE OPSOMMMING: Geen opsomming was ingedien met die tesis

The accumulation of salts in soil is an important agricultural problem that limits crop productivity. Salts containing sodium (Na⁺) are particularly problematic, as cytosolic Na⁺ can interfere with cellular metabolism and lead to cell death. Maintaining low levels of cytosolic Na⁺, therefore, is critical for plant survival during growth in salt. Mechanisms to regulate Na⁺ accumulation in plant cells include extrusion of Na⁺ from the cell and sequestration of Na⁺ into intracellular compartments. Both of these processes are controlled in part through the action of Na⁺/H⁺ exchangers belonging to the Cation/Proton Antiporter-1 (CPA1) gene family. Genes belonging to this family have been identified in both salt-sensitive and salt-tolerant species, suggesting that salt-tolerant species may have evolved salt tolerance through modification of these existing pathways. The research presented here has focused on understanding how salt tolerance has evolved in Brassicaceae species, and particularly on the role that CPA1 genes have played in the adaptation to salinity of Eutrema salsugineum. Specific projects have sought to understand 1) how copy number variation and changes in coding sequences of CPA1 genes contribute to salt tolerance in E. salsugineum and its salt-tolerant relative Schrenkiella parvula, 2) whether functional or regulatory changes in Salt Overly Sensitive 1 (SOS1) from E. salsugineum (EsSOS1) contribute to its enhanced salt tolerance, and 3) whether accessions of Arabidopsis thaliana differ significantly in their response to salt stress.The results indicate that EsSOS1 and SOS1 from S. parvula (SpSOS1) both confer greater salt tolerance in yeast than SOS1 from A. thaliana (AtSOS1) when activated by the complex of the SOS2 kinase and SOS3 calcium-binding protein, whereas only EsSOS1 confers enhanced salt tolerance in the absence of activation. When expressed in A. thaliana, EsSOS1 also confers greater salt tolerance than AtSOS1 through regulatory changes that likely involve differences in expression pattern. Together, the results presented here suggest that mechanisms regulating cellular Na⁺ accumulation that exist in salt-sensitive crop species could be altered to enhance growth in salty soils. In addition, the 19 A. thaliana accessions used to create the MAGIC population were shown to differ significantly in their response to salt stress.

There have been a number of studies that have examined the Eucalyptus spp. for their salt and waterlogging tolerance: but they have done so using conventional methods. A wide range of plants are known to produce greater amounts of proline when stressed, be it salt, temperature, 'drought or several other types of stress. This study looked at production of proline in salt stressed eucalypts to determine whether it can be used to differentiate between individuals andspecies. A range of Eucalyptus species and salt tolerant clones of E. camaldulensis were grown to investigate their proline response to salt stress.

Two groups of plant growth regulators (PGRs), seaweed extract and triazole chemical, have been used in turfgrass management for improving turf quality and strengthening turfgrass to]erance to environmental stress. In order to understand the physiological functions and stress-tolerance mechanisms of the PGRs on turfgrass, a series of studies were conducted with perennial ryegrass (Lolium perenne L.). Ryegrass was treated with or without propiconazole (PPC) (1-( (2-(2,4- dichlorophenyl)-4-propyl-l,3-dioxolan-2yl)methyl) IH-l,2,4-triazole) and a proprietary fortified seaweed extract (FSE), which were combined with or without drought and salinity stress treatment. Total lipids, fatty acid conlposition of polar lipids, and total free and conjugated sterols were determined by the thin layer chromatograph, gas chromatograph, and scanner densitometer. This study indicates that ppe and FSE affected the unsaturation of polar lipid fatty acids and concentration of free sterols, which are major factors in changing cell membrane fluidity and permeability. The PGR-induced alteration of cell membrane lipid composition could be an adaptive process to protect plant nlembrane function under drought and salinity stresses. However, the metabolic effects of PPC and FSE may be different. It was found that PPC had a strong inl1uence on unsaturation of polar lipid fatty acids, whereas FSE had a strong effect on free sterol concentration. Furthermore, a radish cotyledon expansion bioassay analysis showed that the FSE had cytokinin or cytokinin-like activity and could stimulate endogenous cytokinins in ryegrass, whereas an inhibition of cell expansion was seen in PPC-treated plants. The possibility of using the PGRs to reduce fertilizer requirements was also studied. A higher uptake efficiency of most essential elements was found in PPCand FSE-treatedKentucky bluegrass (Poa pratensis L.) than in the control (without PGR treatments). This effect was greater at lower than at higher fert::!L.dtion levels. The utilization efficiency of some major nutrient elements also was higher in PPCand FSE-treated bluegrass than in the control. The possibility of reducing fertilization by PGR application is positive.
Ph. D.

ABSTRACT EFFECTS OF RECYCLED WATER ON LANDSCAPE PLANTS Casey Ray Miranda Recycled water is water that has been previously used, has suffered a loss of quality, and has been properly treated for redistribution (Wu et al. 2001). The use of recycled water as an alternative to fresh water in the landscape can have positive and negative effects. Experimentation on 40 different plant species during a 32 week period (2 phases of 16 weeks), was conducted to analyze the effects of recycled water irrigation on the appearance of landscape plants. Each species of plant was planted into 10 individual number 2 pots and irrigated with recycled water daily. Media and water were tested for nutrients and other constituents. In phase I there were four different species of grasses and grass-like plants, five different perennials, five species of shrubs, and four annuals tested; while phase II tested four species of herbaceous perennials, eight different species of shrubs, six species of groundcovers, and four species of annuals. All tests were conducted at the Paso Robles Waste Water Treatment Plant. Of the grasses and grass like species Yucca spp. and Buchloe spp. performed best. Osteospermum fruticosum, Lavandula angustifolia, Rosmarinus officinalis, Phormium tenax, and Pennisetum setaceum had the best appearance of the herbaceous perennials tested. For the shrubs, Coprosma repens, Cistus purpureus, Dodonea viscosa, Eleagnus pungens, Baccharis pilularis, Ceanothus thysiflorus, Thuja orientalis, and Nerium oleander had the best appearance when irrigated with recycled water. The best annuals were Senecio cineraria, Antirrhinum majus, Primula spp., Viola spp., and Calendula officinalis. Of the groundcovers Heuchera spp., Lonicera japonica, Vinca major, Hedera helix, and Ceanothus griseus had the best results. From the experiment a list of tolerant and non-tolerant plants was compiled (Appendices 1 and 2). While many plants were capable of developing and growing normally, other plants were sensitive to recycled water irrigation. In order to prevent salt damage to plants and expand the use of recycled water, salt tolerance of landscape plant material must be identified (Niu et.al, 2006).

Thesis (MSc)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Late Embryogenesis Abundant (LEA) genes have been irrefutably linked to the osmotic stress response since their initial discovery in maturing cotton seeds. They have since been reported from a multitude of other organism where their occurrence is often associated with general responses to abiotic stress. Many studies have been conducted using LEA genes in over expression strategies to improve abiotic stress resistance. Of the known classes of LEAs, the group 1 LEAs have been widely reported, in plants, to only occur in seeds during late stages of development. Their expression coincides with the seeds acquisition of desiccation tolerance. In this thesis we present a group 1 LEA isolated from the desiccated vegetative tissues (leaves) of the resurrection plant Xerophyta humilis. Using E.coli and Arabidopsis we attempted to use XhLEA to improve salt and water deficit stress-responses, respectively. To this end we conducted soil-drought trials on two independent transgenic Arabidopsis lines expressing XhLEA under a drought inducible-promoter and monitored their responses as compared to untransformed WT (Col-0 ) controls. Solid substrate E.coli growth assays and liquid media growth curves under both stress and unstressed conditions were conducted. We found no obvious beneficial effect through the expression of XhLEA in either of the organisms.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar

The salinity tolerance of golden barrel cactus (Echinocactus grusonii), ocotillo (Fouquieria splendens), saguaro cactus (Carnegiea gigantea), and Gentry’s agave (Agave parryi truncata) was tested. Plants were irrigated with a solution of EC 0.6, 5.0, 10.0, and 15.0 dS/m. Duration of treatments were 18 weeks for saguaro and 26 weeks for the other three species. In general, fresh weight, dry weight, and moisture content decreased with increasing salinity levels, with the exception of saguaro dry weight which was not affected by the treatments, and ocotillo moisture content which increased with increasing salinity. Runoff was collected three times during the experiment and indicated that ion uptake was higher for barrel cactus than the other three species. EC of runoff averaged for all dates and species showed an increase of 17%, 54%, 46%, and 64% over the salinity treatment solutions of 0.6, 5.0, 10.0, and 15.0 dS/m, respectively.

Bacterial endophytes are the organisms that live inside the plant for a full or a part of their life cycle. Endophytic bacteria have captured the interest of agriculture industry due to their plant beneficial properties, such as synthesis of phytohormones, solubilization of soil nutrients, and alleviation of biotic and abiotic stresses. Several studies have reported that stress tolerant endophytic bacteria can work with a similar performance as non-stressed conditions when inoculated to the plants under stressed conditions. Combination of abiotic stresses such as salinity, drought and low nitrogen stress can have additive or agonistic effects on bacterial and plant growth, and their interactions. However, very few studies have reported the impact of combined stress on endophytic bacterial assisted plant growth promotion. Therefore, understanding the underlying mechanisms of endophytic bacterial assisted plant’s tolerance abiotic stresses may provide the means of better exploiting the beneficial abilities of endophytic bacteria in agricultural production. Thus, the aim of this thesis was to study the stress tolerance mechanisms, beneficial characteristics, and plant growth promotion characteristics of endophytic bacteria under individual and combined abiotic stresses. Transcriptome analysis of endophytic bacteria revealed that tolerance mechanisms to deal with one kind of stress is different than concurrent stresses. Salinity and drought stress largely modulated the genes involved in flagellar assembly and membrane transport, showing reduced motility under stress conditions to preserve the energy. Additionally, bacterial endophyte that can fix nitrogen was studied with maize plant growth promotion under drought and low nitrogen stress conditions. The results suggested that diazotrophic bacterial endophyte can promote plant growth under moderate individual and combined stress conditions. Plant growth promoting endophytic bacteria can be utilized as an efficient tool to increase crop production under individual and concurrent abiotic stresses.

[ES] Durante siglos de cultivo en la Península Ibérica después de su introducción en el siglo XVI, las judías se adaptaron a nuevos entornos, evolucionando numerosas variedades locales. Se evaluaron cultivares españoles locales de Phaseolus lunatus (frijol lima) y su resistencia a la salinidad, en dónde se expusieron las plantas a varios tratamientos de sal, con el fin de evaluar el efecto de la salinidad en el crecimiento y el rendimiento del cultivo. Se observó que el estrés salino redujo el peso fresco de los órganos aéreos, lo que permitió clasificar los cuatro genotipos según su tolerancia a la salinidad. la prolina aumentó en todos los cultivares, más notablemente en el cv. VPH-79, con las concentraciones absolutas más altas registradas en los cultivares más tolerantes a la sal. Estos hallazgos indican que P. lunatus es moderadamente tolerante a la sal y que sus principales mecanismos para adaptarse al estrés salino son el mantenimiento de altas concentraciones de K+ y la acumulación de prolina en las hojas. Por otra parte, se analizaron en invernadero 24 genotipos locales de P. vulgaris de España durante dos temporadas consecutivas. De cada genotipo, se cultivaron cinco plantas y se caracterizaron (17 rasgos cuantitativos y 15 cualitativos) utilizando los descriptores del IBPGR. Los resultados obtenidos indican una alta variabilidad para la mayoría de los rasgos, especialmente los relacionados con el rendimiento y sus componentes. Además, se analizaron las respuestas a los tratamientos por déficit hídrico y estrés salino, en cuanto a inhibición del crecimiento y contenido de prolina foliar (Pro), en 47 genotipos de Phaseolus vulgaris de diferentes orígenes. Para la mayoría de las variables de crecimiento analizadas y Pro, los efectos del cultivo, el tratamiento y sus interacciones fueron altamente significativos (p<0.001); los rasgos morfológicos de las raíces, el diámetro del tallo y el número de hojas se debieron principalmente a una variación incontrolada, mientras que la variación del peso fresco y el contenido de agua de los tallos y las hojas fue inducida claramente por el estrés. Bajo las condiciones experimentales, los efectos promedio del estrés salino sobre el crecimiento de las plantas fueron relativamente más débiles que los del déficit hídrico. . Pro, por su parte, fue la única variable que mostró una correlación negativa con todos los parámetros de crecimiento, pero particularmente con los de tallos y hojas mencionados anteriormente, como lo indican los coeficientes de correlación de Pearson y los PCA. Se propone el uso de Pro como un marcador bioquímico adecuado para exámenes simples, rápidos y a gran escala de genotipos de judía, para excluir los más sensibles, aquellos que acumulan concentraciones más altas de Pro en respuesta a tratamientos de estrés hídrico o salino. Asimismo, se han analizado las respuestas a la salinidad en seis cultivares de judía común: cuatro variedades locales de España y dos líneas experimentales de Cuba. La prolina fue usada para clasificar la tolerancia de los cultivares, Las concentraciones de azúcares solubles totales variaron con los tratamientos y entre los genotipos, pero fue difícil evaluar su papel en la tolerancia al estrés de las plantas analizadas. Los cambios en el contenido de malondialdehído (MDA) no indicaron peroxidación de la membrana inducida por sal como resultado del estrés oxidativo secundario; en consecuencia, no se detectó acumulación de compuestos fenólicos totales y flavonoides, como mecanismo de defensa antioxidante. Estos resultados destacan la confiabilidad del uso de prolina como marcador bioquímico del estrés salino en judía y la importancia del mecanismo relacionado con el transporte de potasio a las hojas para conferir tolerancia al estrés a algunos cultivares de judía.
[CA] Durant segles de cultiu a la Península Ibèrica després de la seva introducció en el segle XVI, les mongetes es van adaptar a nous entorns, evolucionant nombroses varietats locals. Es van avaluar conreessis espanyols locals de garrofó (fesol llima) i la seva resistència a la salinitat, a on es van exposar les plantes a diversos tractaments de sal, per tal d'avaluar l'efecte de la salinitat en el creixement i el rendiment de l'cultiu. Es va observar que l'estrès salí va reduir el pes fresc dels òrgans aeris, el que va permetre classificar els quatre genotips segons la seva tolerància a la salinitat. la prolina augmentar en tots els conreessis, més notablement en el cv. VPH-79, amb les concentracions absolutes més altes registrades en els conreessis més tolerants a la sal. Aquestes troballes indiquen que P. lunatus és moderadament tolerant a la sal i que els seus principals mecanismes per adaptar-se a l'estrès salí són el manteniment d'altes concentracions de K + i l'acumulació de prolina en les fulles. D'altra banda, es van analitzar en hivernacle 24 genotips locals de P. vulgaris d'Espanya durant dues temporades consecutives. De cada genotip, es van conrear cinc plantes i es van caracteritzar (17 trets quantitatius i 15 qualitatius) utilitzant els descriptors de l'IBPGR. Els resultats obtinguts indiquen una alta variabilitat per a la majoria dels trets, especialment els relacionats amb el rendiment i els seus components. A més, es van analitzar les respostes als tractaments per dèficit hídric i estrès salí, pel que fa a inhibició de l'creixement i contingut de prolina foliar (Pro), en 47 genotips de Phaseolus vulgaris de diferents orígens. Per a la majoria de les variables de creixement analitzades i Pro, els efectes de l'cultiu, el tractament i les seves interaccions van ser altament significatius (p <0.001); els trets morfològics de les arrels, el diàmetre de la tija i el nombre de fulls es van deure principalment a una variació incontrolada, mentre que la variació de l'pes fresc i el contingut d'aigua de les tiges i les fulles va ser induïda clarament per l'estrès. Sota les condicions experimentals, els efectes mitjana de l'estrès salí sobre el creixement de les plantes van ser relativament més febles que els de el dèficit hídric. . Pro, per la seva banda, va ser l'única variable que va mostrar una correlació negativa amb tots els paràmetres de creixement, però particularment amb els de tiges i fulles esmentats anteriorment, com ho indiquen els coeficients de correlació de Pearson i els PCA. Es proposa l'ús de Pro com un marcador bioquímic adequat per a exàmens simples, ràpids i a gran escala de genotips de mongeta, per excloure els més sensibles, aquells que acumulen concentracions més altes de Pro en resposta a tractaments d'estrès hídric o salí. Així mateix, s'han analitzat les respostes a la salinitat en sis conreessis de mongeta comú: quatre varietats locals d'Espanya i dues línies experimentals de Cuba. La prolina va ser usada per a classificar la tolerància dels conreessis, Les concentracions de sucres solubles totals van variar amb els tractaments i entre els genotips, però va ser difícil avaluar el seu paper en la tolerància a l'estrès de les plantes analitzades. Els canvis en el contingut de malondialdehid (MDA) no van indicar peroxidació de la membrana induïda per sal com a resultat de l'estrès oxidatiu secundari; en conseqüència, no es va detectar acumulació de compostos fenòlics totals i flavonoides, com a mecanisme de defensa antioxidant. Aquests resultats destaquen la fiabilitat de l'ús de prolina com a marcador bioquímic de l'estrès salí en jueva i la importància de l'mecanisme relacionat amb el transport de potassi a les fulles per conferir tolerància a l'estrès a alguns conreessis de mongeta.
[EN] During centuries of cultivation in the Iberian Peninsula after their introduction in the 16th century, beans adapted to new environments, evolving numerous landraces.In this study was also evaluated the resistance to salinity of several local Spanish cultivars of Phaseolus lunatus L. (lima bean). Plants were subjected to various salt treatments and growth and biochemical parameters were determined. It was observed that salt stress reduced the fresh weight of aerial organs, which allowed us to classify the four genotypes according to their tolerance to salinity. In addition, proline increased in all cultivars, most notably in cv. VPH-79, with the highest absolute concentrations recorded in the most salt tolerant cultivars. These findings indicate that P. lunatus is moderately salt tolerant and that its main mechanisms for adapting to salt stress are the maintenance of high K+ concentrations and proline accumulation in leaves. In studies conducted in this research project, 24 landraces of P. vulgaris from Spain were analyzed in greenhouses during two consecutive seasons. From each genotype, five plants were grown and characterized for 17 quantitative and 15 qualitative traits using IBPGR descriptors. . The results obtained indicate high variability for most of the traits, especially those related to yield and its components. On the other hand, this study analyzed the responses to water deficit and salt stress treatments, in terms of growth inhibition and leaf proline (Pro) content, in 47 Phaseolus vulgaris genotypes of different origins. For most of the growth variables analyzed and Pro, the effects of cultivar, treatment and their interactions were highly significant (p <0.001); root morphological traits, stem diameter and number of leaves were mainly due to uncontrolled variation, whereas variation in fresh weight and water content of stems and leaves was clearly induced by stress. Under our experimental conditions, the average effects of salt stress on plant growth were relatively weaker than those of water deficit. . Pro, in turn, was the only variable that showed a negative correlation with all growth parameters, but particularly with those of stems and leaves mentioned above, as indicated by Pearson's correlation coefficients and PCAs. We propose the use of Pro as a biochemical marker suitable for simple, rapid, large-scale screening of bean genotypes to exclude the most sensitive, those that accumulate higher concentrations of Pro in response to water or salt stress treatments. In addition, responses to salinity were analyzed in six common bean cultivars: four local varieties from Spain and two experimental lines from Cuba. Proline was used to rank the relative tolerance of the cultivars. Concentrations of total soluble sugars varied with treatments and among genotypes, but it was difficult to assess their role in stress tolerance of the plants tested.. Changes in malondialdehyde (MDA) content did not indicate salt-induced membrane peroxidation as a result of secondary oxidative stress; consequently, accumulation of total phenolic compounds and flavonoids, as an antioxidant defense mechanism, was not detected. These results highlight the reliability of the use of proline as a biochemical marker of salt stress in common beans and the importance of the mechanism related to potassium transport to leaves in conferring stress tolerance to some common bean cultivars.
Arteaga Castillo, SM. (2021). Cultivos para el cambio climático: selección y caracterización de variedades de judía (Phaseolusvulgaris L.) y Phaseolus lunatus tolerantes a la sequía y salinidad [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/168450
TESIS

Both salinity and drought stresses induce osmotic stress. Thus, cross-tolerance responses and mechanisms may occur in plants. The overall objectives of this study were to determine morphological and physiological responses and mechanisms of turfgrasses and woody species under salinity and drought stress conditions, and determine the relationship between drought and salinity tolerance ability in those species. Five turfgrass entries, ‘Gazelle’ and ‘Matador’ tall fescue (TF), ‘Midnight’ Kentucky bluegrass (KBG), PI368233 (Tolerant KBG), and PI372742 (Susceptible KBG), and three woody species, bigtooth maple (xeric-non saline), bigleaf maple (mesicnon saline) and Eucalyptus (mesic-saline) were compared. For the drought study, water was withheld in Chapter 2 while the dry down treatment was based on daily evapotranspiration (ET) in Chapters 5 and 6. For the salinity study, NaCl and CaCl2 in turfgrasses at electrical conductivity (EC) of 1, 6, 12, 18, and 30 dS m-1 (Chapter 3) and woody species at EC of 1, 3, 6, 9, and 12 dS m-1 (Chapter 4). Susceptible KBG was sensitive to s

Continued irrigation with saline water on Arizona's already salty farm lands will increase the need for crops that are able to maintain yields under stress. We investigated responses of gemùnation salt- tolerant alfalfa (Medicago sativa L.) to salt and temperature stress interactions in comparison to Mesa - Sirsa. Significant interactions were found for the populations, salts and temperatures and their effects on percent germination. The germination salt - tolerant cycles proved to be more cold and heat tolerant under salt stress then Mesa - Sirsa.

>Magister Scientiae - MSc
In an ever changing environment, plants are constantly challenged by various abiotic stresses such as salinity, which limits global crop production. This directly affects food availability for the global population, which is projected to increase to 9.5 billion by 2050, which in turn places great pressure on natural resources and food security. These environmental adversities induce the accumulation of reactive oxygen species (ROS) hydrogen peroxide, hydroxyl and superoxide radicals which cause severe oxidative damage to plants. The equilibrium between the production and detoxification of ROS is then dependent on the modulation of enzymatic and non-enzymatic antioxidants to achieve plant homeostasis.
2024

This study was conducted on plots established by the Benson Institute in the Tamborada region of Cochabamba, Bolivia. The objective of the study was to evaluate the seed production of tall grasses that are tolerant to drought and salinity. A design of randomized blocks in divided plots with and without fertilizer was used. The results showed that the species with the greatest number of stems and inflorescence was Bromus inermis with 10.9 and 88.67 respectively. It was determined that fertilization has an effect on plant height. Furthermore, the species with the greatest seed yield was Festuca arundinacea with 30.4 kg/ha.

A concentração de sais na água é um dos principais aspectos a ser observado para se definir uma estratégia de manejo da irrigação, podendo levar a prejuízos pela salinização do solo, com conseqüente redução do rendimento das culturas. Visto que culturas tolerantes à salinidade apresentam maiores teores foliares de certos nutrientes, então a adubação em culturas sensíveis poderia ser conduzida de modo a elevar os teores destes nutrientes nas folhas, promovendo aumento da tolerância da cultura aos sais. Este trabalho teve o objetivo de estudar os efeitos de três doses de N e K na tolerância da cultura do tomateiro à salinidade, bem como avaliar a performance de medidores de íons específicos (MIE) na determinação de nutrientes na solução do solo e na seiva da planta. Mudas de tomateiro, híbrido Facundo, foram transplantadas em 23/10/2001 em vasos contendo 60 kg de solo franco-argilo-arenoso, no espaçamento de 1,0 x 0,5 m, em um ambiente protegido com cobertura de polietileno. Os tratamentos foram compostos pela combinação de três níveis de N (7,5; 15,0 e 22,5 g planta-1) e três níveis de K (8, 16 e 24 gK2O planta-1) aplicados via fertirrigação por gotejamento, no esquema fatorial 3x3 com cinco repetições, sendo que à água de irrigação foram adicionados os sais cloreto de sódio e cloreto de cálcio para obtenção de condutividade elétrica da água de 9,5 dS m-1. Foram realizadas coletas da solução do solo e da seiva do pecíolo para determinações dos nutrientes pelos MIE, cujos valores foram comparados com as determinações pelos métodos-padrões. Não foram observados efeitos significativos dos tratamentos sobre o desenvolvimento e a produtividade das plantas, bem como sobre a qualidade dos frutos. As concentrações de nutrientes na solução do solo determinadas com os MIE apresentaram boa correlação com as determinações pelos métodos-padrões, e as concentrações de nutrientes na seiva do pecíolo foram bem correlacionadas aos teores na matéria seca das folhas. A condutividade elétrica e a concentração iônica na solução do solo não puderam ser estimadas a partir dos valores medidos no extrato de saturação ou na solução 1:2 apenas pela correção de umidade, com exceção do K e Na, cujas estimativas foram satisfatórias para baixas concentrações destes elementos na solução do solo.
The concentration of salts in the water is one of the main aspects to be observed to define a strategy of irrigation management, which could take to damages due to the soil salinization, with consequent reduction of crops yield. Once tolerant crops to salinity present larger tenors of some nutrients in the leaves, then the fertilizing in sensitive crops could be conducted in order to increase the tenors of these nutrients in the leaves to increase the crop tolerance to salts. This work had the objective of studying the effects of three doses of N and K in the tomato tolerance to salinity, as well as to evaluate the performance of cardy-ion meters (CIM) in the determination of nutrients in the soil solution and in the sap of the plant. Tomato seedlings, hybrid Facundo, were transplanted in 10/23/2001 in vases containing 60 kg of a sandy-clay-loam soil, spaced 1.0 x 0.5 m, in a greenhouse covered with polyethylene film. The treatments were composed by the combination of three levels of N (7.5; 15.0 and 22.5 g plant-1) and three levels of K (8, 16 and 24 gK2O plant-1) applied by drip fertigation, in the 3x3 factorial scheme with five replications. Salts (sodium chloride and calcium chloride) were added to the irrigation water for obtaining an electric conductivity of 9.5 dS m-1. Soil solution and petiole sap were collected for determinations of the nutrients with the CIM, whose values were compared with the determinations by the standard methods. Significant effects of the treatments were not observed for the development and yield of the plants, as well as for the fruits quality. The concentrations of nutrients in the soil solution determined with CIM showed good correlations with the determinations by the standard methods, and the concentrations of nutrients in the petiole sap were well correlated to the tenors in the dry matter of the leaves. The electric conductivity and the ionic concentration in the soil solution could not be estimated from the measured values in the saturation extract or in the solution 1:2 only by the correction of the water content, except for K and Na, whose estimates were satisfactory for low concentrations of these elements in the soil solution.

Salinity is a challenge for crop productivity. Hence, plants exposed to saline environments reduce their vegetative and reproductive growth due to adverse effects of specific ions on metabolism and water relations. In order to cope with salinity, plants display physiological mechanisms based on three main aspects: i) source-sink relationships, ii) resource allocation and iii) alterations in endogenous hormone levels. The roles of developmental and hormonal mechanisms in salt response were investigated here. We employed mutants and transgenic tomato plants affecting different aspects of plant development and hormone response in the same genetic background (cultivar Micro-Tom). The following genotypes were used: Galapagos dwarf (Gdw), Lanata (Ln), lutescent (l), single flower truss (sft), sft heterozygous (sft/+), diageotropica (dgt), entire (e), Never ripe (Nr), epinastic (epi), procera (pro), notabilis (not), anti sense Chloroplastic carotenoid cleavage dioxygenase 7 (35S::asCCD7) and Salicylate hydroxylase (35S::nahG). Among the developmental genotypes studied, sft and l, involved in flower induction and senescence, respectively, were less affected when exposed to salt stress. Although l is considered deleterious due to its precocious senescence, it presented greater shoot biomass and leaf area during salinity. The heterozygous sft/+, whose high productivity was recently linked to an improved vegetative-to-reproductive balance, changed this balance and lowered its yield more than the control MT upon salt treatment. In the analysis of genotypes affecting hormonal status/signaling four kinds of salt responses among the genotypes were observed: i) High shoot growth in spite of high Na:K ratio presented by the strigolactone deficient and high branching CCD7 transgene; ii) High shoot growth and reduced accumulation of Na in tissues (probably due to dilution) presented by the auxin constitutive response e mutant; iii) The opposite response observed in \"ii\" presented by the low auxin sensitivity dgt mutant and iv) growth inhibition combined with reduced levels of Na and higher accumulation of K presented by the not mutant, which produces less ABA. Taken together, the results presented here points to novel developmental mechanisms, such as the promotion of moderate senescence and vegetative growth, and hormonal imbalances to be explored in the pursuing of crops resistant to salt stress.
A salinidade é um desafio para a produtividade agrícola, uma vez que plantas expostas à salinidade tem o crescimento vegetativo e reprodutivo reduzido devido aos efeitos adversos de íons específicos no metabolismo e nas relações hídricas. A fim de lidar com a salinidade, as plantas desempenham mecanismos fisiológicos baseados em três principais características: i) relações fonte-dreno; ii) alocação de reservas e iii) alterações nos níveis endógenos de hormônios. Nesse trabalho, investigamos a relação entre os processos de desenvolvimento e de regulação hormonal com a resposta à salinidade. Para tanto foram usados genótipos de tomateiro com alteração em diferentes vias de desenvolvimento e de produção ou sinalização de hormônios vegetais. Os seguintes genótipos foram usados: Galapagos dwarf (Gdw), Lanata (Ln), lutescent (l), single flower truss (sft), sft heterozygous (sft/+), diageotropica (dgt), entire (e), Never ripe (Nr), epinastic (epi), procera (pro), notabilis (not), anti sense Dioxigenase cloroplastídica de carotenoide 7 (35S::asCCD7) e Salicilato hidroxilase (35S::nahG). Entre os genótipos de desenvolvimento estudados, sft e l, relacionados à menor indução floral e senescência respectivamente, foram os menos afetados quando expostos à salinidade. O genótipo l acumulou maior biomassa e área foliar, apesar de ser considerado deletério devido à senescência precoce. As plantas heterozigotas, sft/+, cuja maior produtividade foi recentemente relacionada a um melhor balanço vegetativo/reprodutivo, alteraram esse balanço sob salinidade e reduziram sua produtividade mais que o controle MT sob estresse salino. Na análise dos genótipos com alteração hormonais foram observados quatro tipos de respostas à salinidade: i) elevado crescimento da parte aérea, apesar da razão Na:K ser alta no genótipo CCD7 cujo transgene induz deficiência de estrigolactona e excessiva ramificação; ii) elevado crescimento e acúmulo reduzido de Na nos tecidos (devido provavelmente a diluição) apresentada pelo mutante de resposta constitutiva a auxina e; iii) o oposto da resposta anterior foi apresentado pelo mutante pouco sensível à auxina , dgt; iv) inibição do crescimento combinado com nível reduzido de Na e alto acúmulo de K apresentada pelo mutante not que produz menos ácido abscísico. Considerados em conjunto, os resultados apresentaram temas para novos mecanismos de desenvolvimento, como a promoção moderada de senescência e do crescimento vegetativo além dos desbalanços hormonais, para serem explorados na busca de culturas resistentes ao estresse salino.

Soil salinity and the arid climate in Libya are major constraints in agriculture and predominantly in foodstuff production which are limiting wheat production and yield. The effect of pre-sowing seed treatments with 50 mM of KCl, NaCl, CaCl2, and distilled water as hydropriming on germination and early seedling growth in two wheat (Triticum aestivum L.) cultivars S-24 (tolerant) and Slambo (untested before) under 0, 100, 200 and 300 mM NaCl concentrations was examined. CaCl2 was the only priming treatment that significantly improved the germination percentage, germination rate, and mean germination time in both cultivars under almost all NaCl concentrations. Thus, priming with CaCl2 was selected for further experiments. In the greenhouse, seeds primed with 50 mM of CaCl2 also improved the emergence percentage, emergence rate, shoot and root length, and fresh and dry weight of shoots and roots of both cultivars under all NaCl concentration except at 300 mM where the emergence was completely inhibited. The response of wheat cultivars to three compost treatments including cow manure compost (CC), greenwaste compost (GC) and 50:50 mixture (mix) between them and sand at percentage inclusions of 10 and 30 % by weight under 0, 100, 200, and 300 mM of NaCl was also investigated. Among all compost treatments, 30% GC and 30% mix were the best treatment and improved almost all growth parameters under salt stress, and 30% GC was also the only treatment that had any emergence at 300 mM NaCl. 30% GC and 30% mix were selected for further experiments. The effect of the combination of the selected priming agent (CaCl2) and the best two compost treatments (30% GC and 30% mix) on the emergence and early seedling growth of both cultivars was tested. The results showed that all the treatments enhanced plant growth parameters including seedling ion uptake in both cultivars, with preference to primed seeds sown in 30% GC. The treatments had the following order of the performance of both cultivars under salt stress. Primed seeds sown in 30% GC > unprimed seeds sown in 30% GC > primed seeds sown in 30% mix > unprimed seeds sown in 30% mix. This enhancement is possibly due to the provision of Ca2+ and / or the improvement in the availability of water as both of them were improved by the application of priming and compost.

[Truncated abstract] Eucalyptus occidentalis, a timber species from south Western Australia, is highly salt and waterlogging tolerant. Screening identified genotypes tolerant of high salt concentrations and waterlogging. Tolerance at provenance, family and individual level, and how phenotypic performance under salt and waterlogging was inherited was explored to provide a breeding population. Salt and/or waterlogged screening was carried out under controlled conditions up to extreme salt levels to determine tolerance between genotypes. This tank method was shown to produce repeatable results. Seedlings of 30 families from 9 provenances were used for screening. At low salt concentration (up to 300 mM NaCl), differentiation occurred for some traits but in general there was only a slight reduction in growth under salt, and waterlogging alone was not detrimental. At high salt concentration (550 mM) differentiation occurred among genotypes for all traits. Equivalent genotypes were also planted in field trials at three sites, two with medium (583 - 847 mm) and one with low rainfall (372 - 469 mm), in southern Western Australia. Survival was low (<53%) after 9 months due to an exceptional dry season followed by 3 months waterlogging in Kirkwood (38 - 1360 mSm-1), but was high >89% after 33 months in saline fields in Sandalwindy (96 - 976 mSm-1) and Roberts (88 - 1424 mSm-1). Some families were similarly in high rank for height under saline conditions in controlled and field trials. Height had the highest narrow-sense heritability value, especially under controlled saltwaterlogging (0.85) treatment and 20% selection enabled a gain of 8-14% under controlled conditions and in the field. Leaf production under salt was not an inherited trait. Systems were developed to hasten deployment of selected material. Extended daylength (16 h) and paclobutrazol (1 mg a.i/mm stem circumference) stimulated flowering in 2 year-old plants. Clonal propagation was possible. Grafting success varied from 0-100% depending on scion/rootstock provenances. ... There was only a slight reduction in heterozygosity from species level to provenance and family levels, and two superior genotypes maintained high diversity. v Crossing was possible using one stop pollination of cut immature styles and capsule retention varied from 0-34% and germination rate from 2-96%. Genetic distance between parents was correlated with seed set and offspring fitness. Wider genetic distances increased capsule retention, seed germination and seedling survival. Under 500 mM salt-waterlogging, offspring heights were similar when parental genetic distances were similar. High heritability value for height from ANOVA-REML parental screening was confirmed using parent-offspring regression. Screened superior genotypes, which withstood very high salt concentration, provide a breeding population for further breeding and for plantations under saline regions in low-medium rainfall areas in Western Australia and other parts of the world. These trees provide an economic return in areas where no other plants may survive and an environmental service in potentially reducing waterlogging, salinity and its spread.

This thesis is a comparative study of the life history strategies, and in particular seed germination requirements, in Australian species of the halophyte plant genus Frankenia L. (Frankeniaceae). Frankenia is a cosmopolitan genus that occurs in Mediterranean, semi-arid, and arid regions on distinctive soil types – commonly on saline, sodic or gypseous soils – in habitats such as coastal cliffs, and on the margins of salt lakes, salt-pans and saltmarshes (Summerhayes 1930; Barnsley 1982). The plants are small shrubs or cushion-bushes with pink, white or pale purple flowers, and salt-encrusted recurved leaves. This project investigates germination requirements for Frankenia in relation to seed age, light requirements, temperature preferences, salinity tolerance, and soil characteristics. It also explores two divergent reproductive strategies – notably seed packaging strategies – in relation to environmental variables. Within the 46 currently recognized endemic Australia species, some species have a few ovules per flower and produce only a few larger seeds per fruit, while other species have many ovules per flower and produce many small seeds per fruit. Large-seededness is thought to increase the probability of successful seedling establishment in drought and salt-stressed environments. As both larger- and smaller-seeded species of Frankenia co-occur in close geographical proximity, hypotheses regarding the advantages of large-seededness in stress environments can be tested. By restricting the analysis of seed mass variation to similar habitats and within a single plant genus, it is possible to test ecological correlates that would otherwise be masked by the strong effects of habitat differences and phylogenetic constraints. Overall, larger-seeded Frankenia species were demonstrated to be advantageous for rapid germination after transitory water availability, and for providing resources to seedlings if resources became limiting before their successful establishment. Smaller-seeded species delayed germination until both soil-water availability and cooler temperatures persisted over a longer time period, improving chances of successful establishment for the more slowly growing seedlings that are more reliant on their surroundings for resources. This study produces information on the seed and seedling biology of many Australian species of Frankenia including several that are of conservation significance, e.g. F. crispa with its isolated populations, and the rare and endangered F. plicata. This information is important for the development of conservation management plans for these and other arid zone, halophyte species. In addition, the results of this study are of practical significance in determining the suitability of Frankenia for inclusion in salinity remediation and mine-site rehabilitation projects, and for promoting Frankenia as a drought and salt tolerant garden plant.

[EN] Pepper is a vegetable of extraordinary economic and social importance in our country. Unfortunately, the persistent exploitation of the land, the monoculture and the intensification of production processes, lead to the development of soil diseases. This coupled with the abiotic stress, mainly the salinity of waters and soil, suboptimal temperatures and water stress, can induce the appearance of physiological disorders in peppers as the Blossom-end rot (BER) and cracking or cracked, induce plant senescence and decrease not only production, but also the quality of the product. Salinity and water shortages are two among the biggest environmental problems that crops have to face in the Mediterranean area. A way to overcome the stresses under the prism of an ecological or integrated crop management, is the use of grafted plants as adaptation strategy. Although there has been remarkable progress in this technique (mainly in tomato, melon, watermelon), in the cultivation of pepper use remains rare. In this Doctoral thesis several pepper genotypes have been selected through different physiological parameters which indicate tolerance to salt and water stress. Commercial cultivars were grafted onto the selected genotypes and were grown under water stress, salinity and control conditions studying several physiological, agronomic responses and the interaction rootstock/scion. The results obtained concluded that genotypes selected and used as rootstocks improved commercial varieties to salt and water stress tolerance, both in terms of performance (commercial production) compared to other commercial characters and variety without grafting. Different physiological mechanisms explain the tolerance to stress, such as the ability to maintain the water potential through an osmotic adjustment, stimulation of the antioxidant system, exclusion or retention of toxic ions (Na+ and Cl-) in saline in the roots and the maintenance of photosynthesis which allows to maintain the metabolic functions of grafted plants and production.
[ES] El pimiento es una hortaliza de extraordinaria importancia económica y social en nuestro país. Lamentablemente, la persistente explotación del suelo, el monocultivo y la intensificación de los procesos de producción, conducen al desarrollo de enfermedades del suelo. Esto unido a los estreses abióticos, principalmente la salinidad de las aguas y del suelo, temperaturas subóptimas y estrés hídrico, puede inducir la aparición de fisiopatias en el pimiento como el Blossom-end rot (BER) y cracking o rajado, inducir senescencia vegetal y disminuir no solo la producción, sino también la calidad del producto. La salinidad y la escasez de agua son unos los mayores problemas medio ambientales a los que tienen que hacer frente los cultivos en el área Mediterránea. Un modo de sortear los estreses bajo el prisma de un manejo integrado o ecológico del cultivo, es la utilización de plantas injertadas como estrategia de adaptación. Aunque se ha producido un notable avance en esta técnica (principalmente en tomate, melón, sandía), en el cultivo del pimiento su utilización es poco frecuente aun. En esta Tesis Doctoral se han seleccionado mediante parámetros fisiológicos diferentes genotipos de pimiento tolerantes al estrés salino e hídrico. Los genotipos seleccionados fueron validados como patrones tolerantes a condiciones de estrés hídrico y salino injertados sobre una variedad comercial mediante el estudio de las respuestas fisiológicas, agronómicas y de la interacción patrón/variedad en ambas condiciones de estrés. De los resultados obtenidos se concluye que los genotipos seleccionados y utilizados como patrones mejoraron la tolerancia de las variedades comerciales a la salinidad, en términos de rendimiento (producción comercial) de frutos comparando con otros patrones comerciales y la variedad sin injertar. Diferentes mecanismos fisiológicos explican la tolerancia al estrés, como la capacidad de mantener el potencial hídrico mediante un ajuste osmótico, estimulación del sistema antioxidante, exclusión o retención de los iones tóxicos salinos (Na+ y Cl-) en las raíces y el mantenimiento de la fotosíntesis que permite mantener las funciones metabólicas de las plantas injertadas y la producción.
[CAT] El pimentó és una hortalissa d'extraordinària importància econòmica i social al nostre país. Lamentablement, la persistent explotació del sòl, el monocultiu i la intensificació dels processos de producció, conduïxen al desenrotllament de malalties del sòl. Açò unit als estressos abiòtics, principalment la salinitat de les aigües i del sòl, temperatures subòptimes i estrés hídric, pot induir l'aparició de fisiopaties en el pimentó com el Blossom-end rot (BER) i cracking, induir senescència vegetal i disminuir no sols la producció, sinó també la qualitat del producte. La salinitat i l'escassetat d'aigua són uns els majors problemes mitjà ambientals als que han de fer front els cultius en l'àrea Mediterrània. Una manera de sortejar els estressos davall el prisma d'un maneig integrat o ecològic del cultiu, és la utilització de plantes empeltades com a estratègia d'adaptació. Encara que s'ha produït un notable avanç en esta técnica (principalment en tomaca, meló, meló d'alger), en el cultiu del pimentó la seua utilització és poc freqüent. En esta Tesi Doctoral s'han seleccionat per mitjà de paràmetres fisiològics diferents genotips de pimentó tolerants a l'estrés salí i hídric. Els genotips seleccionats van ser validats com a patrons tolerants a condicions d'estrés hídric i salí empeltats sobre una varietat comercial per mitjà de l'estudi de les respostes fisiològiques, agronòmiques i de la interacció patrón/variedad en ambdós condicions d'estrés. Dels resultats obtinguts es conclou que els genotips seleccionats i utilitzats com a patrons van millorar la tolerància de les varietats comercials a la salinitat, tant en termes de rendiment (producció comercial) de fruits comparant amb altres patrons comercials i la varietat sense empeltar. Diferents mecanismes fisiològics expliquen la tolerància a l'estrés, com la capacitat de mantindre el potencial hídric per mitjà d'un ajust osmòtic, estimulació del sistema antioxidant, exclusió o retenció dels ions tòxics salins (Na+ i Cl-) en les arrels i el manteniment de la fotosíntesi que permet mantindre les funcions metabòliques de les plantes empeltades i la producció.
Penella Casañ, C. (2015). SCREENING PEPPER GENOTYPES TO OBTAIN TOLERANT ROOTSTOCKS TO SALT AND WATER STRESS: PHYSIOLOGICAL AND AGRONOMICAL RESPONSES OF THE GRAFTED PLANTS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/58767
TESIS
Premiado

[Truncated abstract] Dryland salinity is a major environmental challenge facing agriculture in Australia. One option to manage dryland salinity is the use of perennial forages that increase water use of agricultural systems. However, the current array of perennial forages is limited. Forage species that satisfy the range of climatic and edaphic environments, and production systems, in southern Australia are needed (Chapter 1). In particular, low rainfall regions lack options other than lucerne (Medicago sativa L.) (Chapter 1). The Dorycnium genus (canary clovers) contains perennial species that might be useful forage plants for southern Australia. Dorycnium are sub-shrubs and their plant form differs from current perennial forages (Chapter 1). The aim of this project was to investigate some of the agronomic traits of several species of the genus Dorycnium to explore where they might be used in Australia and how they might be integrated into agricultural systems for management of dryland salinity. First, two desktop investigations assessed the potential adaptation and role of Dorycnium species in southern Australia: a review of the current literature on the agronomic characteristics of Dorycnium (Chapter 2) and an eco-geographical analysis to explore the ecology of Dorycnium species (Chapter 3). The agronomy of Dorycnium has been previously researched mainly in New Zealand, and although this provides some indications on where and how Dorycnium might be best used in Australia, this still requires testing in Australia. In particular, the aluminium tolerance of Dorycnium species indicates that they may be more suitable for acid soils than lucerne. Little ecological data was obtained for germplasm and herbarium collection sites of Dorycnium species. Climate comparisons between the native distribution of Dorycnium species in the Mediterranean basin and Australia, using spatial aridity data and CLIMEX climate match modelling, revealed that D. hirsutum and D. rectum might be suitably adapted to the temperate pasture regions of southern Australia. Suitable germplasm of D. pentaphyllum may also exist, but subsequent investigations in this project focussed on D. hirsutum and D. rectum.

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CNPq
Capes
Enquanto para várias culturas encontram-se na literatura informações sobre o grau de tolerância ao estresse salino, para flores tropicais não existem quaisquer indicativos relacionados à salinidade da água ou do solo. Diante da falta de resultados de pesquisas envolvendo a tolerância de flores tropicais a salinidade da água de irrigação, este trabalho teve por objetivos avaliar a tolerância das espécies H. psittacorum x H. spathocircinata cv. Golden Torch; H. rostrata; H. psittacorum cv. Surinaame Sassy; H. latispatha cv. Red-Yellow Gyro (Laranja); H. psittacorum cv. Red Opal eH. x nickeriensis a diferentes níveis de salinidade da água (CEa) de irrigação (0,3, 0,8, 1,3, 1,8, 2,3 e 2,8 dS m"1) na fase inicial de crescimento. O experimento foi conduzido por 170 dias na casa de vegetação da Universidade Federal de Campina Grande, PB. Os tratamentos foram resultantes da combinação fatorial entre os seis níveis de salinidade e as seis espécies de helicônias, resultando no esquema fatorial 6x 6 com delineamento experimental inteiramente casualizado. As águas de irrigação foram preparadas pela adição de NaCl, para CEa do respectivo nível salino. De acordo com os resultados obtidos, constatou-se que a salinidade de água de irrigação interferiu de forma não contundente na viabilidade dos rizomas e no numero de perfilhos emitidos; Todavia a altura das plantas foi influenciada significativamente pela salinidade da água de irrigação e pelo fator helicônias. Entre os genótipos de helicônas, o teor da água na planta (TAP) variou entre 72,70 e 57,37 %. Conforme os estudos de regressão, a influência da salinidade sobre o teor de água na planta (TAP) foi linear decrescente. Com o aumento da CEa da água ocorre decréscimo linear das variáveis analisadas da fitomassa. O consumo médio de água, decresceu com o aumento da CEa de irrigação. A irrigação com água de salinidade superior a 0,8 dS m", afetou negativamente a emissão de folhas, o numero de perfilhos e o crescimento em altura, sendo maior redução na heliconia We (Nickeriensis). Os níveis de salinidade da água de irrigação acima de 0,8 dS m"1 foram críticos para o crescimento dos genótipos de H. psittacorum x H. spathocircinata cv. Golden Torch e H. x nickeriensis, pois a partir deste nível começaram a ser afetados e os níveis acima de 1,3 dS nf1 foram críticos para o crescimento dos demais genótipos de helicônias. A H. x nickeriensis apresentou os menores índices em relação as variáveis analisadas em comparação as demais helicônias avaliadas, sendo o genótipo mais susceptível a salinidade da água de irrigação.
While for several cultures exist literature information on the degree of tolerance to the saline stress, for tropical flowers don't exist indicative related to the salinity of the water or of the soil. Because the lack of results of researches involving salinity with relationship to the cultivation of tropical flowers, mainly helicônias, this work objectives is study the tolerance of the species H. psittacorum x H. spathocircinata cv. Golden Torch; H. rostrata, H. psittacorum cv. Suriname Sassy; H. latispatha Benth Red-Yellow Gyro (Orange); H. psittacorum cv. Red Opal and H. x nickeriensis at different irrigation water salinity leveis (0,3, 0,8, 1,3, 1,8, 2,3 and 2,8 dS m"1) in the rhizomes viability and growth, determining the criticai leveis for each one. The experiment was led at the greenhouse of the Federal University of Campina Grande, PB. The treatments were resulting of the factorial combination between the six salinity leveis and the six heliconia species, resulting in the factorial outline 6x 6 with with randomized blocks experimental design. The irrigation waters were prepared for the addition of NaCI. The amount of NaCl used in the preparation of the irrigation waters was determined in way obtaining the electric conductivity of the respective saline levei. Considering the results, it was verified that the salinity of irrigation water didn't interfere in the rhizomes viability and shoot emission of heliconia species. The plant heights were influenced significantly by the irrigation water salinity and for the factor heliconia. Among the heliconia genotypes, TAP varied between 8,49 and 7,32 g. According to the regression studies, the influence of the salinity on TAP demonstrated a linear decreasing. With the increase of the water occurs CEa linear decrease of the biomass variables. The average consumption of water, decreased with increasing CEa irrigation. Irrigation with water of salinity above 0.8 dS m"1, negatively affected the issue of leaves. the number of tillers and growth in height, with greater reduction in heliconia H6 (Nickeriensis). The leveis of salinity of irrigation water up to 0.8 dS m"1 were criticai for the growth of genotypes of H. psittacorum x H. spathocircinata cv. Golden Torch and H. x nickeriensis, because from this levei began to be affected and the leveis above 1.3 dS m"1 were criticai for the growth of other genotypes of helicônias. The H. x nickeriensis presented the lowest values for the variables in comparison to other helicônias evaluated, the genotype is more susceptible to salinity of irrigation water.

Salinity is a major issue for the sustainability of agriculture worldwide. Salinity causes an initial hyperosmotic stress and subsequently, secondary nutritional imbalance and oxidative stress through ion toxicity. Many studies focus on identifying genes and the molecular mechanisms involved in salinity tolerance. The identification of such genes may then be used in the development of more salt tolerant crops required for a sustainable global food production. Calcineurin B-like protein interacting protein kinases (CIPKs) are key regulators of pretranscriptional and post-translational responses to abiotic stress. Arabidopsis thaliana CIPK16 (AtCIPK16) was identified from a forward genetic screen as a candidate gene that mediates lower shoot salt accumulation and improves salinity tolerance in Arabidopsis and transgenic barley. However, relatively little is known about the pathways in which CIPK16s operate to affect salinity tolerance and even about the presence of orthologues in cereals. A transcriptomic study was conducted using Arabidopsis thaliana plants subjected to salt stress. The experiment included overexpressing AtCIPK16 and null transgenic plants that were salt stressed or controls. Our analysis characterizes the transcriptional landscape of AtCIPK16 overexpression dependent salt responsiveness in Arabidopsis. These transgene-dependent salt responsive genes suggest an involvement of transcription factors and phytohormones, such as ethylene, jasmonic acid and auxin in downstream signaling pathways. Whether these transcription factors and possible hormone changes have an impact on the plants’ physiological aspect needs to be experimentally determined. Although enhanced salt tolerance has been demonstrated in transgenic barley plants overexpressing AtCIPK16, the presence of a CIPK16 orthologue in barley has not been established. The second part of the project therefore was involved with a molecular phylogenetic analysis of CIPK16 homologues in terrestrial plant species. We mined genome sequence databases, including monocot and dicot species, for CIPK16 homologues. The subsequent phylogenetic analysis revealed a clade containing AtCIPK16 along with two segmentally duplicated CIPKs: AtCIPK5 and AtCIPK25. We found no evidence for an AtCIPK16 orthologue in any monocots but instead found homologues which formed a group basal to the entire CIPK16, 5 and 25 clade. Our analyses also revealed that CIPK16s contain a unique inDel (MMPEGLGGRRG) and a putative nuclear localization signal (PPTKKKKKD). Whether these synapomorphic characters have a biological function will require further experimental validation.We investigated the transcriptome of a subset of six barley cultivars with varying Na+ accumulation in the leaf blade and sheath using the RNA-Seq data generated for the leaf blade, leaf sheath and root tissues from plants grown in saline conditions. Based on prior knowledge we specifically investigated genes involved in sodium transport and salt response and examined their expression and genetic variation (SNPs and indels) across the 6 accessions. Our results showed that allelic variations in HvHKT1;5 may be one of the crucial factors in determining the level of Na+ in the shoots of barley. We hypothesise that for high shoot Na+ accumulating cultivars such as Alexis, Commander and Maritime genes such as HvNHXes (e.g. HvNHX4) may play a role in dealing with high levels of Na+, through sequestrating Na+ into the vacuole or K+ homeostasis.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2018

For more than half of the world’s population, rice (Oryza sativa L.), the most saltsensitive cereal, is a dietary staple. Soil salinity is a major constraint to rice production worldwide. Thus, to feed 9 billion people by 2050, we need to increase rice production while facing the challenges of rapid global environmental changes. To meet some of these challenges, there is a vital requirement to significantly increase rice production in salinized land and improve photosynthetic efficiency. Exposure of plants to soil salinity rapidly reduces their growth and transpiration rates (TRs) due to the ‘osmotic component’ of salt stress (sensu Munns and Tester), which is hypothesized to be related to sensing and signaling mechanisms. Over time, toxic concentrations of Na+ and Cl− accumulate in the cells of the shoot, known as the ‘ionic component’ of salt stress, which causes premature leaf senescence. Both osmotic and ionic components of salinity stress are likely to impact yield. Despite significant advances in our understanding of the ionic components of salinity tolerance, little is known about the early responses of plants to salinity stress. In my PhD project, the aim was to analyze naturally occurring variation in salinity tolerance of rice and identify key genes related to higher salinity tolerance using high-throughput phenomics and field trials. I used a forward genetics approach, with two rice diversity panels (indica and aus) and recently published sequencing data (McCouch et al., 2017). Indica and aus were phenotyped under controlled conditions, while the indica diversity panel was also further studied under field conditions for salinity tolerance. I also examined previously unexplored traits associated with salinity tolerance, in particular the effects of salinity on transpiration and transpiration use efficiency. The non-destructive high-throughput experiments conducted under controlled conditions gave insights into the understudied shoot ion-independent component of salinity tolerance. In parallel, the field experiments increased our understanding of the genetic control of further components of salinity tolerance, including the maintenance of yield under saline conditions. Importantly, this project also aimed to improve the current association methods of GWAS by exploring and testing novel Mixed Linear Models. One major benefit of this Ph.D. project was the development of a more holistic approach that recognizes the complexity of the genotype–phenotype interaction. The purpose of my work was to shed more light on the genetic mechanisms of salinity tolerance in rice and discover genes associated with traits contributing to higher photosynthetic activity under both controlled and field conditions. This will ultimately lead to further exploration of the genetic diversity present in the PRAY indica panel, in order to develop higher yielding rice varieties.

Salt tolerant plants are able to survive in saline soils by the virtue of an array of channels and pumps that minimise sodium entry into roots and loading into the xylem, as well as the sequestration of sodium in the vacuole of the cells of both root and shoot. Regulation of genes involved in conferring salt tolerance is thought to occur via a network of transcription factors. In this project, the aim is to identify transcription factors that are important in regulating genes involved in salinity tolerance. Affymetrix Rice 57K GeneChip data from a previous project were used to analyse gene expression with and without salt stress in the shoots and roots of the salt sensitive Oryza sativa cultivar IR29 and the salt tolerant cultivars FL478, IR63731 and Pokkali. Transcription factors showing differential expression between the salt sensitive and salt tolerant cultivars were identified and confirmed by qRT-PCR. Six transcription factors with confirmed expression patterns were selected and transgenic rice plants were generated either constitutively or salt inducibly over-expressing each of the transcription factor coding sequences. Plants were also made expressing artificial microRNAs designed to reduce levels of transcripts of each transcription factor. The altered expression of five transcription factors, OsOrphan19, OsEREB67, OsbHLH17, OsLUX and OsMYB54 affected plant salinity tolerance, as evidenced by changes in Na⁺ and K⁺ accumulation and plant fresh weight. These five transcription factors show significant homology to other previously known stress responsive genes thus suggesting their involvement in plant stress responses. Further experiments such as chromatin immunoprecipitation sequencing and RNA-sequencing of transgenic plants need to be performed to identify the target promoters and downstream genes, respectively, to determine the precise role of these transcription factors in plant responses to salt stress.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2012

Soil salinity is responsible for significant reductions in crop yield. The salinity tolerance of crops can be improved by minimising the amount of sodium ions (Na⁺) accumulating in the shoot. One hypothesis for reducing shoot Na⁺ accumulation is to minimise Na⁺ entering the plant via the root. Previous studies indicate that in most plants, the majority of Na⁺ entry into root cells is through voltage-insensitive non-selective cation channels (vi-NSCCs), however, the molecular identities of these channels are unclear. Recently two genes that belong to the PQL family were identified as putative vi-NSCCs in yeast. This project aims to functionally characterise three orthologous PQL genes from Arabidopsis thaliana (AtPQL1, AtPQL2 and AtPQL3) and investigate their role in Na⁺ entry into cells and into roots. Bioinformatic tools and in planta techniques were used to determine gene expression profiles, analyse protein sequences and determine the cellular and subcellular localisations of AtPQL1-3. The plasma membrane localisation of AtPQL1 and 2 agrees with the proposed function of vi-NSCCs as ion transport channels. Furthermore, the suggested role of vi-NSCCs in facilitating initial Na⁺ entry into the roots was supported by in silico expression profiles of AtPQL2 and 3 and by observations of reporter proteins driven by PQL promoters in root tissues. Heterologous expression of AtPQL1 in yeast resulted in yeast which were more salt sensitive than controls, suggesting a role in Na⁺ influx into cells. Furthermore, this sensitivity could be ameliorated by the addition of CaCl₂, (indicating Ca²⁺ inhibited the movement of Na⁺), an attribute which corresponds with known properties of vi-NSCCs. A number of transgenic Arabidopsis lines were generated to have altered expression of AtPQL1 to 3 and were then phenotypically analysed in hydroponics under a range of salt treatments. Results of these experiments proved largely inconclusive primarily because individual plants with significantly altered expression of AtPQL1, 2 and/or 3 could not be obtained.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2013

碩士
國立高雄大學
生物科技研究所
100
High salinity stress is the main factor of reducing crops productivity. Plants possess a number of strategies against this damage including ROS generation, induction of stress-related genes expression, accumulation of ABA and proline and up-regulation of antiporters. Reactive oxygen species (ROS) are not only the by-product of metabolism but also involving signal transduction pathway. Previous studies have been reported that continuously expression of PFLP in transgenic plants encourages the generation of ROS and participates in pathogen-resistant mechanism and root-hair development. However, the function of PFLP in plants response to abiotic stress is unclear. In order to investigate the role of PFLP under high salinity stress, pflp-transgenic rice have been generated and studied. In this report, we demonstrated that pflp-transgenic plants exhibit higher salt tolerance compared with TNG67 rice. Earlier ROS production, higher activities of antioxidant enzyme, more ABA accumulation and up-regulated expression in stress-related genes including OsRBOHa, Cu/Zn SOD, OsAPX, OsNCED, OsSOS, OsCIPK24 and OsNHX2 were found in pflp-transgenic plants under high salinity condition. Additionally, the Na+ content of leaf tissues in pflp-transgenic rice were lower than that of TNG67. Here, we demonstrate overexpression of pflp in transgenic rice improves tolerance against high salinity.

Vacuolar proton-pumping pyrophosphatase (H+-PPase) genes encode membrane bound proteins responsible for hydrolysing cytosolic pyrophosphate (PPi) and generating an electrochemical potential difference for protons (H+) across cellular membranes. Constitutive expression of H+-PPase genes, in particular the Arabidopsis thaliana AVP1 gene, significantly improves the growth of several plant species, under control and stress conditions. Despite considerable research, little is known about these genes in bread wheat (Triticum aestivum) and whether they can be utilised to improve wheat growth and/or stress tolerance. The first focus of this research project was to further investigate the role of AVP1 in Arabidopsis. Metabolomics analysis of AVP1 mutant and AVP1 over-expressing Arabidopsis lines showed the concentrations of multiple metabolites were reduced in the mutants compared to wild-type, while concentrations of many metabolites were increased in the AVP1 over-expressing lines compared to wild-type. This analysis suggests that expression of AVP1 could potentially influence pathways involved in the biosynthesis of ascorbic acid, tryptophan and sucrose. The second focus of this project was to investigate the role of AVP1 in bread wheat. To address this, transgenic wheat lines (cv. Bob White), containing constitutive (ubi:AVP1) and stress-inducible (rab17:AVP1) AVP1 expression, were characterised under control and saline conditions. When grown in control and saline hydroponics conditions, however, no phenotypic differences were observed between the ubi:AVP1 or rab17:AVP1 transgenic lines and the null segregants. These findings suggest that, either AVP1 expression does not have a beneficial impact on growth and salt tolerance in bread wheat, or that the promoters and/or experimental methodologies used to characterise these lines were not suitable. The third focus of this project was to identify native wheat H+-PPase (TaVP) genes, and to investigate the role of these genes in vitro and in planta. Using the NRGene wheat reference genome assembly, 15 TaVP genes were identified and were shown to vary in gene sequence and expression. Expression patterns differed greatly between genes, tissue types, developmental stages and wheat varieties, which will be useful for the development of genetic markers for breeding purposes. To characterise the role of these genes, TaVP homologs from the B genome were expressed in a salt-sensitive mutant yeast strain. Analysis of TaVP expressing yeast suggested that TaVP2-B and TaVP4-B may be more beneficial for improving salt tolerance. Transgenic wheat lines (cv. Fielder) constitutively expressing the TaVP1-B and TaVP2-B genes were generated and phenotyped in soil under control and saline conditions. The transgenic wheat lines had significantly reduced plant biomass at maturity, decreased time to flowering, and increased leaf Na+ and Cl- accumulation. These results indicate that TaVP1-B and TaVP2-B influence ion accumulation, plant development and floral transition when constitutively expressed in bread wheat. Overall, the findings of this research project suggest that wheat TaVP genes are likely to have diverse roles in regulating plant growth and salt tolerance, and variation amongst these genes could potentially be utilised to enhance the growth and stress tolerance of bread wheat through selective breeding and gene editing in the future
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2018

Chloride (Cl⁻) is an essential plant micronutrient, but is toxic when accumulated to high concentrations within the cytoplasm, especially in the shoot. Exclusion of Cl⁻ from the shoot is an important trait contributing to salinity tolerance of plants, particularly for Cl⁻ sensitive woody perennials (e.g. grapevine, citrus and avocado) and legumes (e.g. soybean and lotus), where Cl⁻ is considered to be more toxic than the sodium ion (Na⁺). To enhance plant salinity tolerance, it is necessary to understand the mechanisms of Cl⁻ transport through the plant and how it is regulated in response to salinity stress. However, when compared with Na⁺, much less is known about the transport processes involved in controlling Cl⁻ accumulation in the shoot. Two candidate genes encoding putative Cl⁻ transporters in Arabidopsis, proton dependent oligo-peptide transporter 1 (AtPOT1) and AtPOT2 were investigated to examine their role in controlling the loading of Cl⁻ into the apoplastic vessels of root xylem, and therefore Cl⁻ accumulation in the shoot. Transient expression of yellow fluorescent protein (YFP)::AtPOT1 or YFP::AtPOT2 in Arabidopsis mesophyll protoplasts, along with stable expression of green fluorescent protein (GFP)::AtPOT1 or GFP::AtPOT2 determined that both AtPOT1 and AtPOT2 are targeted to the plasma membrane, a location necessary for both POTs to be involved in facilitating Cl⁻ efflux from a cell. Promoter:UidA fusions showed that pAtPOT1 drives expression of the AtPOT1 predominantly in the root stelar cells, suggesting the involvement of AtPOT1 in long distance transport in vasculature tissue. In contrast, AtPOT2 was shown to be located in the cortex of the mature root. Use of quantitative real-time PCR to determine the levels of mRNA transcripts in response to salt stress demonstrated that AtPOT1 transcripts are significantly reduced by both salt and ABA treatments, whereas AtPOT2 transcripts are increased by salt stress. As AtPOT1 transcripts are reduced by ABA and as AtPOT1 encodes an anion transporter located at the plasma membrane of the cells bordering root xylem vessels, it is hypothesised that AtPOT1 is responsible, at least partially, for loading of Cl⁻ into the conductive cells of xylem in roots. Electrophysiological characterisation of AtPOT1 in Xenopus laevis oocytes showed that AtPOT1 is able to facilitate Cl⁻ efflux across the cell membrane at negative membrane potentials, suggesting a role of AtPOT1 in the efflux of Cl⁻ across the plasma membrane of xylem parenchyma cells into the apoplastic xylem transpiration stream. This flux was not affected by the changes in external pH, consistent with the Cl⁻ transport being a uniport, independent of the movement of H⁺. There were no knockout mutants of AtPOT1 available. Therefore, in order to test the effect of alterations of AtPOT1 expression on Cl⁻ accumulation in the shoot, artificial microRNA knockdown constructs were designed and used to transform Arabidopsis Col-0 plants. AtPOT1 transcripts were shown to be reduced by up to 80% in the knockdown lines when compared with nulls, which resulted in a reduction in shoot Cl⁻ concentration by up to 60%. AtPOT1 expression was found to be negatively correlated with shoot Cl⁻ concentration (R² = 0.77). Conversely, constitutive over expression of AtPOT1 increased shoot Cl⁻ accumulation, indicating the important role that AtPOT1 plays in facilitating Cl⁻ xylem loading in Arabidopsis. It is concluded that AtPOT1 mediates Cl⁻ flux into the conductive cells of root xylem in Arabidopsis and the expression of the AtPOT1 is down-regulated during salinity stress. Manipulations of AtPOT1 transcript levels altered shoot Cl⁻ concentrations, which could be utilised for enhancing shoot exclusion of Cl⁻, and hence plant salinity tolerance. Although more functional data is required, AtPOT2 might be involved in the efflux of Cl⁻ from the root to the soil. Therefore, reducing AtPOT1 expression and increasing AtPOT2 expression, may be two strategies for excluding Cl⁻ from the shoot under saline conditions.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2013

Increasing salinity is a worldwide problem, but the knowledge on how salt enters the roots of plants remains largely unknown. Non-selective cation channels (NSCCs) have been suggested to be the major pathway for the entry of sodium ions (Na+) in several species. The hypothesis tested in this research is that PQ loop (PQL) proteins could form NSCCs, mediate some of the Na+ influx into the root and contribute to ion accumulation and the inhibition of growth in saline conditions. This is based on previous preliminary evidence indicating similarities in the properties of NSCC currents and currents mediated by PQL proteins, such as the inhibition of an inward cation current mediated by PQL proteins by high external calcium and pH acidification. PQL family members belonging to clade one in Arabidopsis and barley were characterized using a reverse genetics approach, electrophysiology and high-throughput phenotyping. Expression of AtPQL1a and HvPQL1 in HEK293 cells increased Na+ and K+ inward currents in whole cell membranes. However, when GFP-tagged PQL proteins were transiently overexpressed in tobacco leaf cells, the proteins appeared to localize to intracellular membrane structures. Based on q-RT-PCR, the levels of mRNA of AtPQL1a, AtPQL1b and AtPQL1c is higher in salt stressed plants compared to control plants in the shoot tissue, while the mRNA levels in the root tissue did not change in response to stress. Salt stress responses of lines with altered expression of AtPQL1a, AtPQL1b and AtPQL1c were examined using RGB and chlorophyll fluorescence imaging of plants growing in soil in a controlled environment chamber. Decreases in the levels of expression of AtPQL1a, AtPQL1b and AtPQL1c resulted in larger rosettes, when measured seven days after salt stress imposition. Interestingly, overexpression of AtPQL1a also resulted in plants having larger rosettes in salt stress conditions. Differences between the mutants and the wild-type plants were not observed at earlier stages, suggesting that PQLs might be involved in long-term responses to salt stress. These results contribute towards a better understanding of the role of PQLs in salinity tolerance and provide new targets for crop improvement.

Concentrate (when discharged to the ocean) may have chronic/acute impacts on marine ecosystems, particularly in the mixing zone around outfalls. The environmental impact of the desalination plant discharges is very site- and volumetric specific, and depends to a great extent on the salinity tolerance of the specific marine microbial communities as well as higher order organisms inhabiting the water column in and around this extreme discharge environment. Scientific studies that aim to grant insight into possible impacts of concentrate discharge are very important, in order to understand how this may affect different marine species when exposed to elevated salinity levels or residual chemicals from the treatment process in the discharge site. The objective of this PhD research was to investigate the potential environmental effects of the concentrate discharge in the near-field area around the submerged discharge of the King Abdullah University of Science and Technology (KAUST) seawater reverse osmosis (SWRO) plant by a combination of biological and hydrological studies. Possible changes in microbial abundance were assessed by using flow cytometric (FCM) analysis on a single-cell level in 107 samples, taken from the discharge area, the feed-water intake area and two control sites. Results indicate that changes in microbial abundance in the near-field area of the KAUST SWRO outfall are minor and appear to bethe result of a dilution effect rather than a direct impact of the concentrate discharge. In order to also investigate potential impacts on higher order organisms, a longterm in-situ salinity tolerance test at the discharge site was conducted on the coral Fungia granulosa and its photophysiology. The corals were exposed to elevated levels of salinity as a direct result of concentrate discharge. Their photosynthetic response after exposure to extreme salinity conditions around the full-scale operating SWRO desalination discharge was measured. A pulse amplitude modulated (PAM) fluorometer was used to assess photochemical energy conversion in photosystem II (PSII) measured under constant concentrate discharge conditions. Based on a literature review, we anticipated distinct impairment of photosynthetic characteristics as a response to elevated salinity levels. We also expected particularly quick indications of bleaching for the specimens exposed to the highest salinity levels. The hypothesis was strongly rejected as symbiotic dinoflagellates of Fungia granulosa demonstrated high tolerance to hyper saline stress as measured by effective quantum yield of PSII (ΔF/Fm’) during this study. A series of propulsion driven autonomous underwater vehicle (AUV) missions with velocity and salinity measurements were used for possible plume detection and evaluation of the discharge. The Cornell Mixing Zone Expert System (CORMIX) was additionally utilized in order to assess discharge performance under different ambient velocity magnitudes. Results show that AUV missions could provide significant insight with regards to plume identification and effluent discharge environmental impact studies. Combined with robust in-situ field measurements, models and expert systems were used to evaluate possible impacts on the marine environment in comparison with regulatory mixing zones and dilution criteria. Based on the findings and existing environmental governance (national and international), a revised regulatory framework for mixing zones within the Kingdom of Saudi Arabia is recommended.

The hypothesis that inoculation of transplants with vesicular-arbuscular mycorrhizal (VAM) fungi before planting into saline soils would alleviate salt effects on growth and productivity was tested on lettuce (Lactuca sativa L.) and onion (Allium cepa L.). A secondary hypothesis was that the fungi isolated from a saline soil would be more effective than those from a nonsaline soil. VAM inocula from a high-and a low-salt soil were trap-cultured, their propagules quantified, adjusted, and added to a pasteurized growth medium in which seeds germinated and seedlings grew for a few weeks. These seedlings, once colonized by VAM fungi, were transplanted into saline soil. Seedlings were exposed to high concentrations of NaCl at the time of transplant; in this respect, our technique aimed to simulate conditions of high salinity prevalent in soils affected by NaCl. Preinoculated lettuce and onion transplants grown for 10 weeks had increased shoot biomass compared with nonVAM plants at all salinity (NaCl) levels tested. Leaves of VAM lettuce at the highest salt level were significantly greener than those of the nonVAM lettuce. NonVAM onions were stunted due to available P deficiency in the soil, but inoculation with VAM fungi alleviated P deficiency and salinity effects except at the highest salinity level; nevertheless, VAM onions were significantly larger at all salinity levels. Increasing the level of available P by weekly applications to nonVAM plants partially alleviated the salinity effects on onion growth. VAM fungi from the saline soil site were not more effective in ameliorating the reduction on plant growth caused by salt than those from the nonsaline site. Colonization of roots and length of soil hyphae produced by the test fungi decreased with increasing salt. Results indicate that preinoculation of transplants with VAM fungi can effectively alleviate deleterious effects of saline soils on crop productivity.
Graduation date: 2000

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.
Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 0815. Adviser: Hans J. Bohnert. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

One of the major challenges for agricultural research in the 21st century is to increase crop productivity to meet the growing demand for food and feed. Biotic (e.g. plant pathogens) and abiotic stresses (e.g. soil salinity) have detrimental effects on agricultural productivity, with yield losses being as high as 60% for major crops such as barley, corn, potatoes, sorghum, soybean and wheat, especially in semi-arid regions such as Saudi Arabia. Plant growth promoting bacteria isolated from pioneer desert plants could serve as an eco-friendly, sustainable solution for improving plant growth, stress tolerance and health. In this dissertation, culture-independent amplicon sequencing of bacterial communities revealed how native desert plants influence their surrounding bacterial communities in a phylogeny-dependent manner. By culture-dependent isolation of the plant endosphere compartments and a number of bioassays, more than a hundred bacterial isolates with various biochemical properties, such as nutrient acquisition, hormone production and growth under stress conditions were obtained. From this collection, five phylogenetically diverse bacterial strains were able to promote the growth of the model plant Arabidopsis thaliana under salinity stress conditions in a common mechanism of inducing transcriptional changes of tissue-specific ion transporters and lowering Na+/K+ ratios in the shoots. By combining a number of in vitro bioassays, plant phenotyping and volatile-mediated inhibition assays with next-generation sequencing technology, gas chromatography–mass spectrometry and bioinformatics tools, a candidate strain was presented as a multi-stress tolerance promoting bacterium with potential use in agriculture. Since recent research showed the importance of microbial partners for enhancing the growth and health of plants, a review of the different factors influencing plant-associated microbial communities is presented and a framework for the successful application of microbial inoculants in agriculture is proposed. The presented work demonstrates a holistic approach for tackling agricultural challenges using microbial inoculants from desert plants by combining culturomics, phenomics, genomics and transcriptomics. Microbial inoculants are promising tools for studying abiotic stress tolerance mechanisms in plants, and they provide an eco-friendly solution for increasing crop yield in arid and semi-arid regions, especially in light of a dramatically growing human population and detrimental effects of global warming and climate change.

Many higher plants can synthesize methyl chloride gas via a common metabolic route, also known as the biological chloride methylation. The reaction is catalyzed by an S-adenosyl-L- methionine (AdoMet) dependent halide/thiol methyltransferase (H/TMT). It is speculated that plants use chloride methylation to remove excess chloride via volatilization and hence maintain homeostatic levels of cytoplasmic chloride ion, suggesting a role of H/TMT in salt tolerance. In this project, the effect of engineering a Brassica oleracea thiol methyltransferase (BoTMT) into tomato was studied to determine the physiological relevance of this enzyme in conferring salt tolerance. Transgenic tomato plants acquired the ability to release methyl chloride in response to NaCl treatment, but exhibited no greater tolerance to NaCl, based on several morphological and physiological measurements, as compared to the wild-type plants. The results indicate that AdoMet dependent chloride methylation is unlikely to contribute to an increase in salt tolerance in higher plants.

碩士
國立中山大學
海洋環境及工程學系研究所
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For understanding the effect of the artificial floating island which was placed on the water surface in the saltwater type constructed wetland, on the treatment of wastewater experiment was designed to have some salt tolerant plants cultivated on the artificial floating islands, which was selected for common aquatic plant species including: two emerged plants (Sesuvium portulacastrum (L.) L.and Suaeda nudiflora (Willd.) Moq). Five treatment systems were put in parallel, one was without the plant and floating island (BK), another was placed the floating island without the plant (CK), another was consisted of the populations of S. portulacastrum (L.) L. (100% S.p.), another was consisted of the populations of S. nudiflora (Willd.) Moq (100% S.n.), and the other was consisted of the populations of 50% S. portulacastrum (L.) L. with S. nudiflora (Willd.) Moq. The experiment facilities were simulated to constructed wetland and applied continuous flow with the artificial seawater preparation which was added to some enough levels of nutrient. The goal is to mimic Qifeng Constructed Wetland, for that we to wish place the floating island in the wetland to mitigate the nutrient load. This study showed that the rate of nitrification of the plant-group was increased more significantly than those for non-plant groups, in which these content of nitrogen was found obviously lower (86.1~95%&88~99.4%). Likewise, total nitrogen and nitrate content in the plant-groups still kept reducing. However, when the ammonia nitrogen of the water was increased, the rate of nitrification in the non-plant groups was presented slow down, and as the ammonia nitrogen was raised, the reduced content of nitrogen was become less and less. On the contrary, the plant-group was found having high removal efficiency in these experiment. The data indicated that artificial island with plants could strengthen the rate of nitrification, and assist the constructed wetlands for nitrogen removal. Additionally, the different of hydraulic retention time (HRT) in the constructed wetland systems had an effect on removal efficiency of the floating island. When extending, feedback effect was occurred in the system that could deterioration water quality. But shortening, the nutrient couldn’t be removed from the wastewater. Therefore, for different treatment goal, the constructed wetland is needed to get a suitable HRT, while regularly thinning of plants on the artificial floating island, could be efficient to increase removal efficiency of the nutrient.