ABSTRACT: Pea (Pisum sativum L.) cultivar Arka Chaitra (AC) is considered heat tolerant variety, whereas cultivar Matar Ageta (MA) the heat sensitive variety. In this study, we initially report the repertoire of morpho-physiological traits namely pod number (PNP), weight of pods (PW), seed number/pod (SNP) and weight of seed/pod (SW) during high temperature environment in AC and MA. Subsequently, we conducted pollen viability assay to further examine the pollen behaviour under heat stress (HS). Morpho-physiological analysis revealed that cultivar AC exhibited greater number of pods and seeds, as well as higher pod and seed weights, compared to MA under HS. Furthermore, pollen viability in cultivar AC was reduced by 23%, whereas in cultivar MA, it was reduced by 41%, indicating that AC possess robust tolerance mechanisms under high temperature conditions. Based on these observations, we delve deeper to investigate the regulatory mechanisms by profiling the transcriptomes of cultivars AC and MA using RNA Sequencing under HS. We identified 1922 DEGs in the ACCON-ACHS cluster, 411 DEGs in the MACON-MAHS cluster, and 11,129 DEGs in the ACHS-MAHS cluster indicating substantial transcriptional reprogramming induced by HS. Further, the identified DEGs were annotated through gene ontology (GO) analysis, revealing a significant GO term associated with pollen and flower development, heat stress proteins, and plastid development in tolerant variety, in contrast, the sensitive variety was enriched with GO terms related to cell morphogenesis, cell growth, and cell wall biogenesis. These findings provide in-depth analysis of genes and pathways involved in imparting thermotolerance across pea cultivars AC and MA.
