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.

Roots enable the plant to survive in the natural environment by providing anchorage and acquisition of water and nutrients. In this study, root architectural traits of 153 mungbean genotypes were compared under optimum and low phosphorus (P) conditions. Significant variations and medium to high heritability were observed for the root traits. Total root length was positively and significantly correlated with total root surface area, total root volume, total root tips and root forks under both optimum P

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Mungbean (Vigna radiata L.) is an important food grain legume, but its production capacity is threatened by global warming, which can intensify plant stress and limit future production. Identifying new variation of key root traits in mungbean will provide the basis for breeding lines with effective root characteristics for improved water uptake to mitigate heat and drought stress. The AVRDC mungbean mini core collection consisting of 296 genotypes was screened under modified semi-hydroponic screening conditions to determine the variation for fourteen root-related traits. The AVRDC mungbean mini core collection displayed wide variations for the primary root length, total surface area, and total root length, and based on agglomerative hierarchical clustering eight homogeneous groups displaying different root traits could be identified. Germplasm with potentially favorable root traits has been identified for further studies to identify the donor genotypes for breeding cultivars with enhanced adaptation to water-deficit stress and other stress conditions.

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Mungbean or green gram (Vigna radiata L. Wilczek) is a major pulse crop of Southeast Asia. This is the most liked pulse in India because of its good palatability, nutritional quality and easy digestibility. It is mainly grown in subsistence farming systems in India. The crop species has evolved in a diverse range of agroclimatic conditions and therefore the local germplasm has rich genetic diversity. However, this diversity has not been explored to identify useful traits and germplasm to utilise in crop improvement programmes. Therefore, a study was performed on 1,232 mungbean accessions using 8 quantitative, 18 qualitative traits and 4 seed morphometric traits to understand genetic diversity of the crop and identify trait‐specific germplasm. Wide range of variation was observed for days to flowering, days to maturity, pod length, number of seeds/pod and 100‐seed weight. Relative high phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) was observed for 100‐seed weight, flowering period, seed length and seed breadth. Broad sense heritability (h2) analysis indicated that days to 50% flowering, flowering period, days to 80% maturity, 100‐seed weight and seed‐dimension‐related traits are highly suitable for mungbean breeding programmes. Agglomerative hierarchical clustering analysis based on morphological quantitative traits indicates that the diversity in the mungbean germplasm has no significant relationship with respect to their geographical origin. Principal component analysis (PCA) revealed that the first five principal components (PCs) explained 91.4% of total variation. The maximum variance was explained by PC1 (44.61%) followed by PC2 (21.15%). Plotting of observations in two‐dimensional space corresponding to PC1 and PC2 revealed wide distribution of accessions, and certain accessions were found associated with variables. The agromorphological variability and its genetic nature revealed from this study may prove very useful in ongoing and future breeding programmes.

To understand the physiological basis of tolerance to combined stresses to low phosphorus (P) and drought in mungbean (Vignaradiata (L.) R. Wilczek), a diverse set of 100 accessions were evaluated in hydroponics at sufficient (250 μM) and low (3 μM) P and exposed to drought (dehydration) stress. The principal component analysis and ranking of accessions based on relative values revealed that IC280489, EC397142, IC76415, IC333090, IC507340, and IC121316 performed superior while IC119005, IC73401, IC488526, and IC325853 performed poorly in all treatments. Selected accessions were evaluated in soil under control (sufficient P, irrigated), low P (without P, irrigated), drought (sufficient P, withholding irrigation), and combined stress (low P, withholding irrigation). Under combined stress, a significant reduction in gas exchange traits (photosynthesis, stomatal conductance, transpiration, instantaneous water use efficiency) and P uptake in seed and shoot was observed under combined stress as compared to individual stresses. Among accessions, IC488526 was most sensitive while IC333090 and IC507340 exhibited tolerance to individual or combined stress. The water balance and low P adaptation traits like membrane stability index, relative water content, specific leaf weight, organic acid exudation, biomass, grain yield, and P uptake can be used as physiological markers to evaluate for agronomic performance. Accessions with considerable tolerance to low P and drought stress can be either used as ‘donors’ in Vigna breeding program or cultivated in areas with limited P and water availability or both.