Morpho-physiological and metabolites alteration in the susceptible and tolerant genotypes of sesame under waterlogging stress and post-waterlogging recovery

Abstract

Among the oil-seed crops, Sesamum indicum L. is an important nutritionally rich crop, well adapted to grow in semi-arid regions. Waterlogging stress adversely affects the growth of sesame by limiting diffused oxygen availability in soil and generating hypoxic, subsequently anoxic conditions. The present study aimed to screen the 1,006 accessions for waterlogging stress response at the seedling stage to identify the most tolerant and susceptible genotype. The investigation revealed that, 48 h of stress are detrimental and 10 days post-waterlogging impede crop survival. The screened accessions were narrowed down by 8 to detect the morphological alterations, and the morphological characteristics such as shoot height, root length, SPAD, branches per plant and relative water content were found maximum in PB-Til 2 and accession EC377024. PB-Til 2 and accessions EC377024 and IC129289 were identified as positive check, tolerant and susceptible genotypes respectively, which drove the interest to elucidate the physiological and antioxidant behaviour. In addition, the leaf and photosynthetic parameters (net photosynthetic assimilation, intercellular CO2 concentration, stomatal conductance, leaf area, length, width and perimeter) were significantly higher in check and EC377024. Enzymatic (SOD, CAT and APX) and non-enzymatic (TFC, TPC, DPPH, FRAP, TAA, MDA and proline) antioxidant activity was notably higher in check and EC377024 and lower in IC129289. DAB and NBT assay confirmed lower damages from free radicals in EC377024 compared to IC129289. Moreover, contrasting gene expression profiling of free radicals (POD and RBOH-C), carbohydrate metabolism (SuSy2 and StSy1), phosphate group gene (PSRG), and plant hormone (ERF RAP 2-7, ACC) confirmed the tolerance in EC377024 under waterlogging stress conditions. Besides, metabolomics study in EC377024 at control and 48 h of waterlogging stress indicate the significant accumulated metabolites in fatty acid (decanoate), carbohydrate, amino acid, Shikimate, MEP (5-enolpyruvoyl-shikimate-3-phosphate) Krebs cycle and Xanthophyll pathways. This comprehensive combination of morpho-physiological, biochemical, molecular and metabolomic characterizations highlight the stress responsive mechanisms between the tolerant (EC377024) and susceptible (IC129289) genotypes.