Drought Susceptible Genotypes Research Articles

Antioxidant, physiological and biochemical responses of drought susceptible and drought tolerant mustard (Brassica juncea L) genotypes to rhizobacterial inoculation under water deficit stress

Response of drought susceptible (DS) genotype Pusa Karishma LES-39 and drought tolerant (DT) mustard genotype NPJ-124, to rhizobacterial inoculation under water deficit stress, was compared in the present study to determine the influence of inoculants on biochemical and physiological attributes of these two different genotypes. Inoculation was observed to improve root and shoot dry weight in both the genotypes, although better results were observed in the DS genotype. There was variation in the response of the two genotypes to rhizobacterial inoculation, under water deficit stress. Significant improvement in most of the physiological and biochemical parameters including antioxidative enzyme activities of the DS genotype; with concomitant decrease in starch content, accumulation of H2O2 and lipid peroxidation upon inoculation of rhizobacteria was observed. In contrast, there was improvement in only few physiological and biochemical parameters in the DT genotype in response to inoculation with rhizobacteria. There was significant increase in catalase enzyme activity along with concomitant decrease in lipid peroxidation. Thus, drought susceptibility of the mustard genotypes, NPJ-124 and Pusa Karishma LES-39, determined their physiological, biochemical and antioxidative responses to rhizobacterial inoculation under water deficit stress. Expression of drought stress responsive genes belonging to ABA-dependent (RD20 and RD26) and ABA-independent (DREB2 and DREB1-2) pathways was studied in the DS genotype. Expression of DREB2 and DREB1-2 genes was considerably enhanced due to inoculation under water deficit stress; indicating that in Bacillus-mediated priming for drought stress tolerance, in this genotype, ABA-independent pathway probably played key role in enhancing tolerance to drought stress.

IN-VITRO SCREENING OF DIFFERENT TOMATO GENOTYPES AGAINST PEG INDUCED WATER STRESS

Tomato (Lycopersicum esculentum L.) is one of the most economically important plants in the Solanaceae family. Water scarcity is one of the major climatic constraints which is affecting all crops including tomato in the world. Selection of water stress tolerant cultivars is an important strategy to overcome this problem. Therefore the present research was conducted to determine the effect PEG induced water stress on germination percentage and early growth stages of tomato seedlings. Fifteen different tomato genotypes were screened under in-vitro conditions using two different concentrations of PEG (2% and 4%). The experiment was arranged in a completely randomized design (CRD) with three replications. Parameters like germination percentage (%), root length (cm), shoot length (cm) and seedling biomass (g) were recorded during the experiment. Results indicated that PEG induced water stress significantly reduced germination percentage (%) and other growth parameters in drought susceptible tomato genotypes (RUS-1, Rustam, R-2017, Pakit, 17904, Kashmiri, Kiara, Avinash, and K.K.2). Whereas in other genotypes “R. Wonder, Naqeeb, Rio grande, T-4, Patfeeder and Nagina” all parameters increase with an increase in PEG concentration. However among these genotypes, “Patfeeder” exhibited highest germination percentage (100 %) with maximum root and shoot length and seedling biomass at highest PEG concentration 4%. Based on experimental results, “Patfeeder” was considered a drought tolerant genotype due to its better performance in different levels of water stress.

Transcriptomic and metabolomic profiling of drought-tolerant and susceptible sesame genotypes in response to drought stress

BackgroundSesame is an important oil crop due to its high oil, antioxidant, and protein content. Drought stress is a major abiotic stress that affects sesame production as well as the quality of sesame seed. To reveal the adaptive mechanism of sesame in response to water deficient conditions, transcriptomic and metabolomics were applied in drought-tolerant (DT) and drought-susceptible (DS) sesame genotypes.ResultsTranscriptomic analysis reveals a set of core drought-responsive genes (684 up-regulated and 1346 down-regulated) in sesame that was robustly differently expressed in both genotypes. Most enriched drought-responsive genes are mainly involved in protein processing in endoplasmic reticulum, plant hormone signal transduction photosynthesis, lipid metabolism, and amino acid metabolism. Drought-susceptible genotype was more disturbed by drought stress at both transcriptional and metabolic levels, since more drought-responsive genes/metabolites were identified in DS. Drought-responsive genes associated with stress response, amino acid metabolism, and reactive oxygen species scavenging were more enriched or activated in DT. According to the partial least-squares discriminate analysis, the most important metabolites which were accumulated under drought stress in both genotypes includes ABA, amino acids, and organic acids. Especially, higher levels of ABA, proline, arginine, lysine, aromatic and branched chain amino acids, GABA, saccharopine, 2-aminoadipate, and allantoin were found in DT under stress condition. Combination of transcriptomic and metabolomic analysis highlights the important role of amino acid metabolism (especially saccharopine pathway) and ABA metabolism and signaling pathway for drought tolerance in sesame.ConclusionThe results of the present study provide valuable information for better understanding the molecular mechanism underlying drought tolerance of sesame, and also provide useful clues for the genetic improvement of drought tolerance in sesame.

Selection Criteria for Drought-Tolerant Bread Wheat Genotypes at Seedling Stage

Diminishing water resources as a result of excessive use of water for irrigation and climate change posture a severe global threat to food security. Herein, an experiment was conducted to determine the selection criteria for drought-tolerant bread wheat genotypes at the seedling stage using morphological and photosynthetic pigmentation-related traits. A panel of 105 wheat landraces, historical Pakistani varieties, and advance breeding lines were evaluated under normal and drought stress using factorial completely randomized design. The root length, fresh weight, dry weight, cell membrane thermo-stability, and chlorophyll b were positively correlated among themselves under both normal and stress conditions. Hence, selection of any one of these traits enhances the performance of other traits. The shoot length was non-significant and negatively associated with all other studied characters except relative water content. The results suggested that selection for shoot length could not improve genetic gain for drought tolerance. Out of 10 principal components (PCs), the first three PCs were showed significant genetic variation under both conditions. The first three PCs showed 74.6% and 76% cumulative genetic variation under normal and drought conditions, respectively. Based on PCA, 10 drought-tolerant and five drought-susceptible genotypes were identified. Overall results suggested that selection for root length, fresh weight, dry weight, cell membrane thermo-stability, and chlorophyll b at the seedling stage would improve genetic gain for drought tolerance. The outperforming genotypes under drought stress conditions can be useful in future wheat breeding programs, and early selection for the traits recommended in this study will be effective for developing high-yielding and drought-tolerant wheat varieties.

Transcriptomic and physiological analyses reveal drought adaptation strategies in drought-tolerant and -susceptible watermelon genotypes

Drought stress has become one of the most urgent environmental hazards for horticultural crops. In this research, we analyzed watermelon adaptation strategies to drought stress in drought-tolerant (M20) and -susceptible (Y34) genotypes via transcriptomic and physiological analyses. After drought stress, a total of 6228 and 4311 differentially expressed genes (DEGs) were observed in Y34 and M20, respectively. Numerous DEGs were involved in various defense responses such as antioxidation, protein protection, osmotic adjustment, wax accumulation, hormone signaling, and melatonin biosynthesis. Accordingly, the contents of ABA, melatonin, wax, and some osmoprotectants were increased by drought stress in both Y34 and especially M20. Exogenous application of melatonin or ABA induced wax accumulation and drought tolerance and melatonin may function upstream of ABA. In comparison to Y34, M20 was more able to activate ABA signaling, melatonin biosynthesis, osmotic adjustment, antioxidation, and wax accumulation under drought stress. These stronger responses confer M20 tolerance to drought. Photosynthesis and most DEGs involved in photosynthesis and cell growth were decreased by drought stress in both M20 and especially Y34. For drought-susceptible genotypes, growth retardation may be an important mechanism for saving and redistributing resources in order to reprogram stress signaling networks.

Diversity and Tissue Preference of Osmotolerant Bacterial Endophytes Associated with Pearl Millet Genotypes Having Differential Drought Susceptibilities.

Genetic and functional diversity of osmotolerant bacterial endophytes colonizing the root, stem, and leaf tissues of pearl millet genotypes differing in their drought susceptibility was assessed. Two genotypes of pearl millet, viz., the drought tolerant genotype TT-1 and the drought susceptible genotype PPMI-69, were used in the present study. Diazotrophs were found to be the predominant colonizers, followed by the Gram positive bacteria in most of the tissues of both the genotypes. Higher proportion of bacterial endophytes obtained from the drought tolerant genotype was found to be osmotolerant. Results of 16S rRNA gene-ARDRA analysis grouped 50 of the highly osmotolerant isolates into 16 clusters, out of which nine clusters had only one isolate each, indicating their uniqueness. One cluster had 21 isolates and remaining clusters were represented by isolates ranging from two to four. The representative isolates from each cluster were identified, and Bacillus was found to be the most prevalent osmotolerant genera with many different species. Other endophytic bacteria belonged to Pseudomonas sp., Stenotrophomonas sp., and Macrococcus caseolyticus. High phylogenetic diversity was observed in the roots of the drought tolerant genotype while different tissues of the drought susceptible genotype showed less diversity. Isolates of Bacillus axarquiensis were present in all the tissues of both the genotypes of pearl millet. However, most of the other endophytic bacteria showed tissue/genotype specificity. With the exception of B. axarquiensis and B. thuringiensis, rest all the species of Bacillus were found colonizing only the drought-tolerant genotype; while M. caseolyticus colonized all the tissues of only the drought susceptible genotype. There was high incidence of IAA producers and low incidence of ACC deaminase producers among the isolates from the root tissues of the drought-tolerant genotype while reverse was the case for the drought-susceptible genotype. Thus, host played an important role in the selection of endophytes based on both phylogenetic and functional traits.

Drought responsive transcriptome profiling in roots of contrasting rice genotypes

Drought avoidance is an important strategy exhibited by cereals for maintaining productivity under water deficit conditions. Most of the modern rice varieties stop their root growth during drought whereas few traditional cultivars have the ability to maintain root growth. An upland rice genotype Nootripathu was found to maintain its root growth under drought when compared to a shallow rooted IR20. Drought responsive transcriptome profiling of roots of IR20 and Nootripathu revealed that tolerant Nootripathu showed relatively more number of DEGs (4287) than susceptible IR20 (3081). Drought stress significantly affected expression of genes encoding cellulose synthases and expansins, two major gene families involved formation of cell walls in the shallow rooted drought susceptible genotype IR20. Genes involved in the biosynthesis of phytohormones namely ABA and Brassinosteroids were found to be significantly up-regulated in roots of Nootripathu during drought. Up-regulation of autophagy related genes involved in degradation of denatured/misfolded proteins in roots of IR20 indicates the severe progression of stress in IR20. Co-localization analysis of DEGs against QTL hotspots identified several putative candidate genes including a zinc finger domain containing protein, a bZIP transcription factor, a MYB factor and an OsMADS7 requiring further functional validation.

Integrated omics data of two annual ryegrass (Lolium multiflorum L.) genotypes reveals core metabolic processes under drought stress

BackgroundAnnual ryegrass (Lolium multiflorum L.) is a commercially important, widely distributed forage crop that is used in the production of hay and silage worldwide. Drought has been a severe environmental constraint in its production. Nevertheless, only a handful of studies have examined the impact of short-term drought stress on annual ryegrass. The aim of this study was to explore how stress-induced core metabolic processes enhance drought tolerance, or adaptation to drought, in annual ryegrass.ResultsWe profiled the transcriptomes, proteomes, and metabolomes of two annual ryegrass genotypes: the drought-resistant genotype “Abundant 10” and drought-susceptible genotype “Adrenalin 11.” We identified differentially expressed metabolites and their corresponding proteins and transcripts that are involved in 23 core metabolic processes, in response to short-term drought stress. Protein–gene–metabolite correlation networks were built to reveal the relationships between the expression of transcripts, proteins, and metabolites in drought-resistant annual ryegrass. Furthermore, integrated metabolic pathways were used to observe changes in enzymes corresponding with levels of amino acids, lipids, carbohydrate conjugates, nucleosides, alkaloids and their derivatives, and pyridines and their derivatives. The resulting omics data underscored the significance of 23 core metabolic processes on the enhancement of drought tolerance or adaptation to drought in annual ryegrass.ConclusionsThe regulatory networks were inferred using MCoA and correlation analysis to reveal the relationships among the expression of transcripts, proteins, and metabolites that highlight the corresponding elements of these core metabolic pathways. Our results provide valuable insight into the molecular mechanisms of drought resistance, and represent a promising strategy toward the improvement of drought tolerance in annual ryegrass.

Water restriction and physiological traits in soybean genotypes contrasting for nitrogen fixation drought tolerance

Biological nitrogen fixation (BNF) is essential to the economic viability of the soybean [Glycine max (L.) Merrill] crop in Brazil, but drought may impair the BNF processes. We evaluated physiological traits of nitrogen fixation drought-tolerant (NFDT) (R01-581F, R01-416F and R02-1325) and drought-susceptible (CD 215 and BRS 317) genotypes of soybean subjected to drought or regular water supply between 45 and 55 days after emergence, in an experiment under greenhouse conditions in pots containing non-sterile soil. R01-581F had more stable photosynthetic and transpiration rates, and higher intercellular CO2 levels under drought. Drought reduced the chlorophyll concentration in all genotypes, but with less intensity in R01-581F and R02-1325. The NFDT genotypes generally showed higher concentrations of N, K and Mn in shoots, irrespective of the water condition. Exposure to drought increased total soluble sugars in nodules in all genotypes, as well as the concentrations of ureides in leaves and nodules, whereas ureides in petioles increased only in the susceptible genotypes. Drought negatively affected photosynthetic and BNF attributes; however, R01-581F showed the best performance, with potential for use in breeding programs aiming at drought-tolerant varieties.

Identification and Validation of Reference Genes and Their Impact on Normalized Gene Expression Studies across Cultivated and Wild Cicer Species.

Quantitative Real-Time PCR (qPCR) is a preferred and reliable method for accurate quantification of gene expression to understand precise gene functions. A total of 25 candidate reference genes including traditional and new generation reference genes were selected and evaluated in a diverse set of chickpea samples. The samples used in this study included nine chickpea genotypes (Cicer spp.) comprising of cultivated and wild species, six abiotic stress treatments (drought, salinity, high vapor pressure deficit, abscisic acid, cold and heat shock), and five diverse tissues (leaf, root, flower, seedlings and seed). The geNorm, NormFinder and RefFinder algorithms used to identify stably expressed genes in four sample sets revealed stable expression of UCP and G6PD genes across genotypes, while TIP41 and CAC were highly stable under abiotic stress conditions. While PP2A and ABCT genes were ranked as best for different tissues, ABCT, UCP and CAC were most stable across all samples. This study demonstrated the usefulness of new generation reference genes for more accurate qPCR based gene expression quantification in cultivated as well as wild chickpea species. Validation of the best reference genes was carried out by studying their impact on normalization of aquaporin genes PIP1;4 and TIP3;1, in three contrasting chickpea genotypes under high vapor pressure deficit (VPD) treatment. The chickpea TIP3;1 gene got significantly up regulated under high VPD conditions with higher relative expression in the drought susceptible genotype, confirming the suitability of the selected reference genes for expression analysis. This is the first comprehensive study on the stability of the new generation reference genes for qPCR studies in chickpea across species, different tissues and abiotic stresses.

Evaluation of groundnut genotypes for late season drought tolerance

Fifty genotypes of groundnut including released varieties and advanced breeding lines were used to assess th drought tolerance. These genotypes were evaluated both in managed drought stress (DS) and non stress (NS) situations during post rainy season (Jan- April), 2011 at Oilseeds Farm, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India. The drought stress was imposed by withholding irrigation after 60 days after sowing for t drought stress trial. Observations were recorded for pod yield per plant and kernel yield per plant on random chosen five plants per entry per replication. The data were subjected to ANOVA and drought tolerance parameter <italic>viz.</italic>, drought susceptibility index (DSI) for pod yield per plant and kernel yield per plant. The results indicated that genotypes differed significantly for pod and kernel yield per plant. Among the genotypes, 7 and 6 genotypes were observed as highly drought tolerant based on pod and kernel yield per plant respectively. A total of 6 and 9 genotypes recorded as highly susceptible to drought for pod and kernel yield per plant respectively. Among these genotypes, each three drought tolerant (ICGV 91114, K1375 and ICGV 02125) and drought susceptible (ICGV 01279, ICGV 98170 and ICGV 98175) genotypes were selected for hybridization programme to develop mapping populations.

Responses in gas exchange and water status between drought-tolerant and -susceptible soybean genotypes with ABA application

The purpose of this study was to investigate the physiological responses of drought-tolerant and drought-susceptible soybean genotypes to exogenous abscisic acid (ABA) application during progressive soil drying at seedling stages. Five-day old soybean seedlings were transplanted into PVC tubes filled with soil mixture. Seedlings were watered daily with similar water volumes until second trifoliate leaves emerged, and thereafter soil drying with or without exogenous ABA application was imposed. Half of the seedlings of each genotype were left for regular watering as control plants. Soil water status declined significantly over seven days of withholding water supply for both genotypes. Leaf expansion rate, stomatal conductance (gs), leaf water potential (ψw), and relative water content of leaves (%RWC) declined significantly under soil drying as well as soil drying with ABA application, compared to their values for well-watered soybean genotypes. However, a drought-tolerant genotype (C12) responded more rapidly than a drought-susceptible genotype (C08) after imposition of soil drying and soil drying with exogenous ABA. In addition, application of exogenous ABA to water-restricted soybeans resulted in higher %RWC and ψw in the drought-tolerant than in the drought-susceptible genotype. Compared to the drought-susceptible genotype, the drought-tolerant genotype was more responsive to exogenous ABA application, resulting in a higher root-to-shoot ratio.

Understanding abiotic stress tolerance mechanisms in soybean: A comparative evaluation of soybean response to drought and flooding stress

Many sources of drought and flooding tolerance have been identified in soybean, however underlying molecular and physiological mechanisms are poorly understood. Therefore, it is important to illuminate different plant responses to these abiotic stresses and understand the mechanisms that confer tolerance. Towards this goal we used four contrasting soybean (Glycine max) genotypes (PI 567690 – drought tolerant, Pana – drought susceptible, PI 408105A – flooding tolerant, S99-2281 – flooding susceptible) grown under greenhouse conditions and compared genotypic responses to drought and flooding at the physiological, biochemical, and cellular level. We also quantified these variations and tried to infer their role in drought and flooding tolerance in soybean. Our results revealed that different mechanisms contribute to reduction in net photosynthesis under drought and flooding stress. Under drought stress, ABA and stomatal conductance are responsible for reduced photosynthetic rate; while under flooding stress, accumulation of starch granules played a major role. Drought tolerant genotypes PI 567690 and PI 408105A had higher plastoglobule numbers than the susceptible Pana and S99-2281. Drought stress increased the number and size of plastoglobules in most of the genotypes pointing to a possible role in stress tolerance. Interestingly, there were seven fibrillin proteins localized within the plastoglobules that were up-regulated in the drought and flooding tolerant genotypes PI 567690 and PI 408105A, respectively, but down-regulated in the drought susceptible genotype Pana. These results suggest a potential role of Fibrillin proteins, FBN1a, 1b and 7a in soybean response to drought and flooding stress.

Effect of PEG induced osmotic stress on osmolytes and antioxidative enzymes in sorghum seedlings

The present investigations were undertaken to evaluate the levels of proline and glycine betaine osmolytes and activities of antioxidative enzymes under PEG-6000-induced osmotic stress in drought susceptible, tolerant and stay-green sorghum genotypes. A total of forty-eight drought susceptible, tolerant and stay-green rabi sorghum genotypes were screened to evaluate proline and glycine betaine accumulation under osmotic stress of PEG-6000. Among the tolerant genotypes, RSLG-262 and RSV-1366 accumulated the highest proline content, whereas, RSV-458 and Hadgaon local accumulated the highest glycine betaine content than susceptible genotypes. The high proline accumulating tolerant genotypes, RSLG-262 and RSV-1366 also exhibited correspondingly the highest ∆1_pyrroline-5-carboxylate synthetase activity. The mean activities of antioxidative enzymes such as superoxide dismutase, catalase, peroxidases and relative leaf water content were higher in the leaves of stay-green genotypes, followed by tolerant and susceptible types. Within stay-green genotypes, B-35 and E-36-1 and a drought tolerant genotype RSLG-262 recorded higher antioxidative enzyme activities as compared to other genotypes. The stay-green genotypes, B-35 and E-36-1 and a tolerant genotype RSLG-262 appeared to be the most promising ones.

Physiological Studies on Moisture Stress Tolerance in Chickpea (Cicer Arietinum L.) Genotypes

Drought is a major constraint that limits seed yield in chickpea (Cicer arietinum L.). It is important to establish the relative importance many of these drought-related traits for prioritizing their consideration in breeding for drought tolerance improvements. The objective of this study was to categorize the drought tolerant and susceptible chickpea genotypes on the basis of physiological parameters. An experiment was conducted with five chickpea genotypes in field under irrigated and rain fed conditions. Observations were recorded on relative water content (RWC), and the contents of chlorophyll (Chl), carotenoid (Car), proline (Pro) and protein in the five chickpea genotypes. RWC and contents of Chl, Car and protein decreased under moisture stress, whereas Pro content increased with the increase in moisture stress. Pusa-1108, Pusa-362, Pusa-1103 were able to maintain relatively higher RWC, Chl, Car and protein content and greater Pro accumulation, while Flip 90-166 and SBD- 377 showed comparatively greater decline in the RWC, Chl, Car and Protein and less accumulation of Pro under moisture stress. The data suggest that chickpea genotypes can be categorized into drought tolerant and susceptible types based on the variations in RWC, Chl, Car, Pro and protein content.

Effect of PEG Induced Osmotic Stress on Peroxidase and Superoxide Dismutase Isozymes in Sorghum Seedlings

The present investigation was undertaken to understand the effect of PEG-6000– induced osmotic stress on isozymes of superoxide dismutase and peroxidase as well as their activities in four each of drought susceptible, tolerant and stay-green sorghum genotypes at seedling stage. Total number of isozymes of superoxide dismutase was more under stressed than unstressed condition, whereas the band intensity was also higher under stressed condition. Two to four new peroxidase isozymes with very high colour intensity bands were observed in most of the genotypes under stressed condition. The mean activity of superoxide dismutase and peroxidase were higher in the stay-green genotypes, followed by tolerant and susceptible genotypes.

Effect of soil drought on the yield structure, protein and phenolics content in Pisum sativum and Lupinus luteus

The aim of this study was to determine the susceptibility to drought of selected genotypes of pea and yellow lupine. An analysis was made of the changes in protein and phenolics content and how they affect the yield parameters. The plant material consisted of six genotypes of pea and yellow lupine. Seedlings (plants with 5–6 leaves) were subjected to drought at 25% field water capacity for 2 weeks. Soil drought decreased the relative water content (RWC) in the leaves of pea and lupine. On the 14th day of drought the increase in protein content was almost two-folds higher in lupine plants than in pea. The phenolics content showed an increase in both pea and lupine plants on the 1st day of drought (20% and 15%, respectively), while on the 14th day the phenolics content decreased by 2% in pea, and was not significantly different in lupine. Soil drought reduced the values of almost all yield components. Only the 1000-seed weight increased under drought conditions. Based on the drought susceptibility index values for RWC, protein and phenolics content, seed yield and biomass, the least drought-susceptible genotypes were Batuta (pea) and Morocco 4 (lupine), as they had the lowest values of these parameters.

Epigenetic responses to drought stress in rice (Oryza sativa L.)

Cytosine methylation polymorphism plays a key role in gene regulation, mainly in expression of genes in crop plants. The differential expression of cytosine methylation over drought stress response was analyzed in rice using drought susceptible but agronomically superior lines IR 20 and CO 43, and drought tolerant genotypes PL and PMK 3 and their F1 hybrids. The parents and hybrids were subjected to two moisture regimes viz., one under drought condition and another under control condition. The cytosine methylation polymorphism in genomic DNA was quantified under both the conditions at the reproductive stage of the plant using the Methylation Sensitive Amplified Polymorphism (MSAP) technique devised by Xiong et al. (261:439-446, 1999). The results depicted that under drought condition, hyper-methylation was predominant in the drought susceptible genotypes while drought tolerant genotypes presented hypo-methylation behavior. While imposing drought, spikelet sterility per cent was positively correlated to percentage of methylation whereas, panicle length, number of seed per panicle, panicle weight, 100 seed weight, and yield/plant were negatively correlated indicating the role of epigenetic regulation in yield attributing traits in response to drought. Thus, methylation can be considered as an important epigenetic regulatory mechanism in rice plants to adapt drought situation. From this study, we speculate that the hyper- methylation may be an indicator of drought susceptibility and the hypo-methylation for drought tolerance and this methylation polymorphism can be effectively used in drought screening program.

Identification of microsatellite markers associated with grain protein content in durum wheat grown under drought stress at terminal growth stages

Grain protein content (GPC) in durum wheat is a crucial determinant of pasta quality and as such is an important economic factor. This study was carried out to determine the microsatellite markers (SSRs) as associated with GPC in durum wheat grown under normal and moisture stress conditions. F3 and F4 population derived from 151 F2 individuals developed from a cross between Oste-Gata (drought tolerant) and Massara-1 (drought susceptible) genotypes, were used. The population was evaluated under four environmental conditions (two irrigation regimes in two growing seasons). The results of single marker regression analysis (SMA) revealed that 2, 4 and 10 markers to be associated with GPC, test weight (TW) and 1000 grain weight (TGW), respectively. These markers explained between 4.4 and 21.8% of the phenotypic variation in either environmental condition. The most significant marker observed for GPC was located on 5B chromosome near Xgwm408 under normal conditions and the other marker was observed on 1A, explaining about 15% of phenotypic variance. However, it was not recognized any marker related to GPC under drought stress conditions. Xgwm408 marker was coincident with the markers identified for TW, TGW and components of grain yield under drought stress conditions. In spite of 5B, the other chromosomes such as 2B and 3B were related to quantitative traits like TW and TGW. Composite interval mapping (CIM) identified 4 and 5 putative minor and major QTL for TW and TGW, respectively. Two QTL near Xbarc101 and Xbarc124 markers on 3B and 2B chromosome, explained up to 45.2 and 6% of phenotypic variations of TGW and TW, respectively.

Identification of RAPD and ISSR markers for drought tolerance in wheat (Triticum aestivum L.)

Drought tolerance is the essential trait that needs to be incorporated in cereal crops, particularly those grown under the rainfed cultivation. Drought tolerance being contributed by several regions of the genome requires identification of these regions, using suitable molecular markers. Therefore, present investigation was aimed at analyzing the genetic diversity present among the cultivars of rainfed and the irrigated areas with respect to the drought tolerant trait. In all, 14 RAPD and 90 ISSR markers were used to identify these genomic regions. Out of 14 RAPD markers, one RAPD primer exhibited polymorphic banding pattern with 18.6% polymorphism, clearly separating drought tolerant and drought susceptible genotypes. Out of 90 ISSR primers, only 3 ISSR primers revealed polymorphism in relation to the drought tolerance trait exhibiting 21.38% polymorphism.