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Sesame is predominantly cultivated in rainfed and low fertile lands and is frequently exposed to terminal drought. Sesamum species inhabiting dryland ecosystems adaptively diverge from those inhabiting rainfed habitats, and drought-specific traits have a genetic basis. In sesame, traits associated with drought conditions have not been explored to date, yet studies of these traits are needed given that drought is predicted to become more frequent and severe in many parts of the world because of climate change. Here, 76 accessions from the available Indian core set were used to quantify variation in several traits under irrigated (WW) and terminal drought stress (WS) conditions as well as their association with seed yield over two consecutive years. The range of trait variation among the studied genotypes under WW and WS was significant. Furthermore, the traits associated with seed yield under WW and WS differed. The per se performance of the accessions indicated that the expression of most traits was reduced under WS. The correlation analysis revealed that the number of branches, leaf area (LA), leaves dry weight (LDW), number of capsules plant–1, and harvest index (HI) were positively correlated with seed yield under WW and WS, and total dry matter (TDM), plant stem weight, and canopy temperature (CT) were negatively correlated with seed yield under WW and WS, indicating that smaller and cooler canopy genotypes had higher yields. The genotypes IC-131936, IC-204045, IC-204861, IC-205363, IC-205311, and IC-73576 with the highest seed yields were characterized by low canopy temperature, high relative water content, and high harvest index under WS. Phenotypic and molecular diversity analysis was conducted on genotypes along with checks. Phenotypic diversity was assessed using multivariate analysis, whereas molecular diversity was estimated using simple sequence repeat (SSR) loci to facilitate the use of sesame in breeding and genetic mapping. SSRs showed low allelic variation, as indicated by a low average number of alleles (2.31) per locus, gene diversity (0.25), and polymorphism information content (0.22). Cluster analysis (CA) [neighbor-joining (NJ) tree] revealed three major genotypic groups and structure analysis showed 4 populations. The diverse genotypes identified with promising morpho-physiological traits can be used in breeding programs to develop new varieties.

Background and Aims Submergence tolerance in rice is primarily attributed to SUB1 gene action, but other associated traits such as leaf gas film (LGF) thickness, leaf hydrophobicity, porosity and leaf density have been known to aid submergence tolerance in rice. However, association of these traits with SUB1 QTL is not well worked out. In this study, we aim to investigate (i) whether the presence of SUB1 QTL in the genetic background has any influence on the thickness of the leaf gas film, and (ii) whether removal of it has any impact on stress perception and submergence tolerance in Sub1 and non-Sub1 rice? Methods We examined twelve genotypes (including both Sub1 and non-Sub1 types) for different leaf traits like initial LGF thickness, leaf hydrophobicity tissue porosity and leaf density in order to work out the relation of these traits with SUB1 QTL in rice. Furthermore, we investigated the changes in gene expression profile and different metabolic processes in selected genotypes in the presence and absence of their LGF to study its impact on stress perception and adaptation. Key Results The initial thickness of LGF and hydrophobicity seemed to have a highly positive correlation with the presence of SUB1 QTL in the genetic background of rice; although, other leaf traits like porosity and density seemed to be independent of it. Artificial removal of LGF resulted in partial loss of tolerance showing increased ethylene production and early induction of anoxia related genes (SUB1A-1, ACS5, Ramy3D, ADH1) which manifested symptoms like increased stem elongation, faster chlorophyll and starch breakdown and partial loss of quiescence in SUB1 containing rice genotypes. Stripping of LGF resulted in early and enhanced induction of SUB1A-1 indicating quicker perception of stress. Conclusions The presence of SUB1 in the genetic background positively influences surface hydrophobicity and the concomitant LGF thickness of rice. Furthermore, LGF helps in terms of providing better ethylene ventilation and reduced in planta accumulation, owing to the slowing down of ethylene induced leaf senescence under submergence stress.

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