Morpho-Physiological Traits and Functional Markers Based Molecular Dissection of Heat-Tolerance in Urdbean.

Urdbean (Vigna mungo L. Hepper) is one of the important pulse crops. Its cultivation is not so popular during summer seasons because this crop is unable to withstand excessive heat stress beside lack of humidity in the atmosphere. Therefore, a panel of 97 urdbean diverse genotypes was assessed for yield under stress and non-stress conditions with an aim to identify heat tolerant genotypes. This study identified 8 highly heat tolerant and 35 highly heat sensitive genotypes based on heat susceptibility index. Further, physiological and biochemical traits-based characterization of a group of six highly heat sensitive and seven highly heat tolerant urdbean genotypes showed genotypic variability for leaf nitrogen balance index (NBI), chlorophyll (SPAD), epidermal flavnols, and anthocyanin contents under 42/25°C max/min temperature. Our results showed higher membrane stability index among heat tolerant genotypes compared to sensitive genotypes. Significant differences among genotypes for ETR at different levels of PAR irradiances and PAR × genotypes interactions indicated high photosynthetic ability of a few genotypes under heat stress. Further, the most highly sensitive genotype PKGU-1 showed a decrease in different fluorescence parameters indicating distortion of PS II. Consequently, reduction in the quantum yield of PS II was observed in a sensitive one as compared to a tolerant genotype. Fluorescence kinetics showed the delayed and fast quenching of Fm in highly heat sensitive (PKGU 1) and tolerant (UPU 85-86) genotypes, respectively. Moreover, tolerant genotype (UPU 85-86) had high antioxidant activities explaining their role for scavenging superoxide radicals (ROS) protecting delicate membranes from oxidative damage. Molecular characterization further pinpointed genetic differences between heat tolerant (UPU 85-86) and heat sensitive genotypes (PKGU 1). These findings will contribute to the breeding toward the development of heat tolerant cultivars in urdbean.

Discerning molecular diversity and association mapping for phenological, physiological and yield traits under high temperature stress in chickpea (Cicer arietinum L.).

High temperature (HT) stress is assuming serious production constraint for chickpea production worldwide. A collection of 182 diverse chickpea genotypes was assessed for genetic variation in 15 traits including phenological, physiological and yield-related traits under both normal sown (NS) and late sown (LS) conditions for two years 2017-2018 and 2018-2019, which revealed significant variation for all the traits. Association mapping of chickpea genotypes was also conducted with 120 simple sequence repeat markers distributed across all the chickpea chromosomes to discern the molecular diversity and to capture the significant marker-trait association (MTA). MTA analysis based on mixed linear model (MLM) revealed a total of 24 and 14 significant associations for various traits evaluated under NS conditions in 2017 and 2018, respectively. Similarly, a total of 17 and 34 significant associations for various traits were also recorded under LS conditions in 2018 and 2019, respectively. Notably, ICCM0297, NCPGR150, TAA160 and NCPGR156 markers showed significant MTA under both NS and LS conditions and GA11 exhibited significant MTA for filled pod% under late sown condition for both years. Thus, these markers could be useful for genomics-assisted breeding for developing heat-tolerant chickpea genotype.

GATA simple sequence repeats function as enhancer blocker boundaries.

Simple sequence repeats (SSRs) account for ~3% of the human genome, but their functional significance still remains unclear. One of the prominent SSRs the GATA tetranucleotide repeat has preferentially accumulated in complex organisms. GATA repeats are particularly enriched on the human Y chromosome, and their non-random distribution and exclusive association with genes expressed during early development indicate their role in coordinated gene regulation. Here we show that GATA repeats have enhancer blocker activity in Drosophila and human cells. This enhancer blocker activity is seen in transgenic as well as native context of the enhancers at various developmental stages. These findings ascribe functional significance to SSRs and offer an explanation as to why SSRs, especially GATA, may have accumulated in complex organisms.