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Drought poses the most significant environmental constrain that limits the growth and yield efficiency of vegetables around the world. The major challenges lies is to identify potential genetic resources and technology development that improve quality and productivity of vegetable crops under declining land, reducing natural resources and increasing environmental stresses. Varied responses of different crop species/genotypes to water-deficit condition have been studied for a long time, and several morphological, physiological and biochemical characters have been suggested to be responsible for drought tolerance. Understanding the morphological, physiological and biochemical responses to drought is essential for a holistic perception of plant resistance mechanisms to water-limited conditions and also to design screening techniques for drought tolerance that may be employed in crop breeding. Drought stress lead to the overproduction of reactive oxygen species (ROS) in plants which inactivate enzymes and damage important cellular components. The effects of the action of free radicals on membranes include the induction of lipid peroxidation and fatty acid de-esterification. Plants possess very efficient enzymatic and non-enzymatic antioxidant defense systems which work in concert to control the cascades of uncontrolled oxidation and protect plant cells from oxidative damage by scavenging of ROS. In this review the important morphological, physiological and biochemical traits that are influenced by drought stress, and may be important indices for identification/screening of drought tolerant genotypes in vegetable crops has been described.

In the present study, genetic variation among 40 cucumber genotypes was analyzed by means of morpho-physiological traits and 21 EST-SSR markers. Diversity was observed for morpho-physiological characters like days to 50% female flowering (37-46.9, number of fruits/plant (1.33-5.80), average fruit weight (41-333), vine length (36-364), relative water content (58.5-92.7), electrolyte leakage (15.9-37.1), photosynthetic efficiency (0.40-0.75) and chlorophyll concentration index (11.1-28.6). The pair wise Jaccard similarity coefficient ranged from 0.00 to 0.27 for quantitative traits and 0.24 to 0.96 for EST-SSR markers indicating that the accessions represent genetically diverse populations. With twenty-one EST-SSR markers, polymorphism revealed among 40 cucumber genotypes, number of alleles varied 2-6 with an average 3.05. Polymorphism information content varied from 0.002 to 0.989 (mean = 0.308). The number of effective allele (Ne), expected heterozygosity (He) and unbiased expected heterozygosity (uHe) of these EST-SSRs were 1.079-1.753, 0.074-0.428 and 0.074-0.434, respectively. Same 21 EST-SSR markers transferability checked in four other Cucumis species: snapmelon ( var. ), muskmelon ( L.), pickling melon ( var. ) and wild muskmelon ( var. ) with frequency of 61.9, 95.2, 76.2, and 76.2%, respectively. Present study provides useful information on variability, which can assist geneticists with desirable traits for cucumber germplasm utilization. Observed physiological parameters may assists in selection of genotype for abiotic stress tolerance also, EST-SSR markers may be useful for genetic studies in related species.

Out of 103 microsatellite markers used for studying the genetic diversity among local landraces of species, 56 were found polymorphic, including 38 gSSR and 18 eSSR, respectively. A total of 197 amplification products were obtained. The mean number of alleles per locus was 3.52. The PIC ranged from 0.037 to 0.986, while size of amplified product ranged from 105 to 500 bp. Cucumber-derived SSRs were amplified within (68%), (61.16%), and (60.2%), with an average of 63.12% cross-transferability. The Jaccard's coefficient ranged from 0.66 to 0.97, with an average of 0.81. High genetic variability was observed for node of 1st hermaphrodite flower (6.4-17), days to 1st hermaphrodite flower (38-52.1), days to 1st fruit harvest (43-65), number of fruit per cluster (1-5.9), fruit length (3.9-25 cm), fruit weight (18.4-175 g), number of fruit per plant (20-147.5), and yield per plant (2.2-4.7 kg). Two sub-populations were identified including 21 genotypes (sub-population I) and 06 genotypes (sub-population II), these two sub-populations showed 0.608-0.395% of the ancestral relationship to each other. This study provides information for future exploration, collection, and utilization of genotypes, as well as the polymorphic markers identified could be available for the study of landmarks in linkages, genomic structures, evolutionary ecology, and marker-assisted selection (MAS) in species.

Background: Principal component analysis and Finlay-Wilkinson stability analysis were carried out at research farm of ICAR-Indian Institute of Vegetable Research, Varanasi to identify diverse french bean genotypes for green pod yield and suitable genotypes for stable yield and yield related parameters.Methods: All the 24 genotypes were laid out in randomized block design with two replications during winter, 2017 and 2018. Principal component analysis and stability analysis was done to identify the diverse and stable genotypes.Result: Eight principal components were observed and the maximum variability was concentrated in the first three principal components PC1, PC2 and PC3 which contributed to 68.61% variance. Cluster analysis from principal component scores formed three clusters with a maximum of seventeen genotypes in cluster I followed by six genotypes in cluster II and one genotype in cluster III. High heritability was observed for 10 pod weight, number of pods per cluster and number of seeds per pod and moderate heritability was observed for yield per plant. Finlay-Wilkinson stability analysis identified the stable genotypes viz., FMGCV 1378, FMGCV 0958, Arka Suvidha, Valentino, Banoa and VRFBB-14-2 for green pod yield per plant, Cartagenta for pod length (cm) and Paulista, Slender Pack, Arka Suvidha, Valentino, FMGCV 0958, Banoa, FORC 6V 1136, VRFBB-14-1, VRFBB-14-2 for number of pods per plant.