Context Post-anthesis heat stress is a major concern for wheat. Stay-green (SG) can serve as a crucial marker for plant adaptation to it. Though genetic resources provide an invaluable gene pool for crop breeding, collections are still uncharacterised and their potential is yet to be explored. Aims This study was planned to characterise and evaluate wheat genetic resources, including wild germplasm, for heat stress tolerance using SG traits as selection criteria. Methods Experiment was conducted with thirty wheat genotypes under late and very late sown environments for 2 years. Genotypes were assessed for SG traits like Normalised Difference Vegetation Index (NDVI), Soil Plant Analysis Development Chlorophyll Meter Reading (SCMR), Leaf Senescence Rate (LSR), chlorophyll fluorescence (Fv/Fm), canopy temperature (CT), phenological traits, morphological traits, yield and its attributes; and characterised into three categories viz., slow senescing, intermediate senescing and fast senescing, based on their rate of senescence. Key results Results indicate that slow-senescing genotypes had a significantly higher NDVI, SCMR and yield as compared to fast-senescing genotypes. NDVI, SCMR, Fv/Fm, days to heading, days to anthesis, days to maturity, grain weight per spike, 100-grain weight and biomass were significantly positively correlated whereas LSR and CT were significantly negatively correlated with grain yield. From the principal component analysis studies, it was revealed that genotypes with a high SCMR, a low LSR, and a high grain yield were placed together as SG genotypes. Conclusions This study confirms that genotypes with SG traits performed better under heat stress. Implications From the wild, genotypes HTW 11 (W), HTW 67 (W) and HTW 6 (W) can be utilised for heat tolerance breedings.
