Plant stresses causing accumulation of reactive oxidative species (ROS) are scavenged by effective antioxidant defense systems. Therefore, the present study performed genome-wide identification of superoxide dismutase (SOD) and glutathione peroxidase (GPX) gene families in cultivated and wild soybeans, and 11 other legume species. We identified a total of 101 and 95 genes of SOD and GPX, respectively, across thirteen legume species. The highest numbers of SODs and GPXs were identified in cultivated (Glycine max) and wild (Glycine soja). A comparative phylogenetic study revealed highest homology among the SODs and GPXs of cultivated and wild soybeans relative to other legumes. The exon/intron structure, motif and synteny blocks were conserved in both soybean species. According to Ka/Ks, purifying the selection played the major evolutionary role in these gene families, and segmental duplication are major driving force for SODs and GPXs expansion. In addition, the qRT-PCR analysis of the G. max and G. soja SOD and GPX genes revealed significant differential expression of these genes in response to oxidative, drought and salinity stresses in root tissue. In conclusion, our study provides new insights for the evolution of SOD and GPX gene families in legumes, and provides resources for further functional characterization of these genes for multiple stresses.

Plants coevolved with their antioxidant defense systems, which detoxify and adjust levels of reactive oxygen species (ROS) under multiple plant stresses. We performed whole-genome identification of ascorbate peroxidase (APX) and catalase (CAT) families in cultivated and wild soybeans. In cultivated and wild soybean genomes, we identified 11 and 10 APX genes, respectively, whereas the numbers of identified CAT genes were four in each species. Comparative phylogenetic analysis revealed more homology among cultivated and wild soybeans relative to other legumes. Exon/intron structure, motif and synteny blocks are conserved in cultivated and wild species. According to the Ka/Ks value, purifying selection is a major force for evolution of these gene families in wild soybean; however, the APX gene family was evolved by both positive and purifying selection in cultivated soybean. Segmental duplication was a major factor involved in the expansion of APX and CAT genes. Expression patterns revealed that APX and CAT genes are differentially expressed across fourteen different soybean tissues under water deficit (WD), heat stress (HS) and combined drought plus heat stress (WD + HS). Altogether, the current study provides broad insights into these gene families in soybeans. Our results indicate that APX and CAT gene families modulate multiple stress response in soybeans.

| Due to the global increase in temperature, heat stress has become a great threat for the crops production worldwide. This research was conducted to assess the genotypic variability and relationship of accumulation of glycine betaine, proline, chlorophyll contents, and cell membrane thermostability with yield in different cauliflower varieties under heat stress. Heat stress was imposed by early sowing of genotypes (in July as compared to September sowing). Under the early sown condition, the high temperature was experienced by the plants during the curd development stage. Heat tolerance ability of the genotypes was assessed by their ability to curd induction and development at high temperature and also based on different physiological traits. Heat susceptible genotypes showed lengthened curd induction stage. Further, decrease in chlorophyll and osmoprotectants contents was also seen in heat susceptible genotypes. TSX-C40 was identified as most susceptible genotype to heat stress due to low accumulation of glycine betaine and proline, and greater relative cell injury percentage, along with lengthened curd induction stage. Curd induction in TSX-C40 was seen when the maximum temperature was between 21.5-26.0 ˚C. While CF-Early was identified as heat tolerant genotype as curd induction was started at an average maximum temperature of 34 ˚C. Further CF-Early showed high chlorophyll contents, and more glycine betaine, and proline accumulation. Less relative cell injury percentage resulted in less damage to cell membranes and the protection of the photosynthetic apparatus during the heat stress of CF-Early. In addition, the accumulation of more osmoprotectants in CF-Early may lead to reactive oxygen species scavenging to protect cell membranes.

| Genetic diversity is the baseline of any breeding program as determining the variability of germplasm is an indispensable assist for crop improvement strategies. Multivariate analyses such as cluster and principal component analysis measures the amount of genetic diversity in respect of several charaters and asseses the relative contribution of different traits to the total variation. In the present study, nineteen genotypes were evaluated for presence of genetic diversity through principal component and cluster analyses. The experiment was designed in randomized complete block design with two replications at the experimental area of Vegetable Research Institute, Faisalabad, Pakistan in 2019. In the principal component analysis, first three principal components had eigenvalue >1 and contributed 80.86% of the variation among the genotypes. Traits i.e. plant weight, curd weight, curd yield, leaf length, plant height to extreme, and the number of leaves contributed significant positive component loading to these principal components (PCs). Biplot analysis among the first two PCs found the Casper RZ, AA Cauli-08, and Snow queen as diverse genotypes. Cluster analysis based on Euclidian distance grouped the genotypes into 3 distinct clusters. Some of the genotypes that have narrow genetic base were grouped into a similar cluster. Based on these results, it may be concluded that some of the genotypes are higly diverse while most of the genotypes are similar in nature. Genotypes from the distinct cluster should be used for obtaining diverse recombinants in segregating generations, exploiting heterosis, and broaden the genetic base of the cauliflower germplasm.