Stay-green trait serves as yield stability attribute under combined heat and drought stress in wheat (Triticum aestivum L.)

The present study was conducted to evaluate the effect of a stay-green trait to stabilize the yield responses under combined heat and drought stress on wheat. Ten Recombinant Inbred Lines (RILs) of wheat along with their parents (HI1500/DBW 43) were evaluated under timely sown with irrigation (control) and without irrigation (drought stress), and late sown with irrigation (heat stress) and without irrigation (combined heat and drought stress). We observed that combined stress of drought and heat stress was more detrimental than the individual stresses for plants. GCP 6 and GCP 33 RILs showed 50.08% and 49.52% while GCP 23 and GCP 30 showed 61.05% and 62.17% decrease in yield under combined stress as compared to the control condition. We found that GCP 6 and GCP 33 RILs stabilized their yield by maintaining stay-green traits such as retaining a higher amount of chlorophyll, photosynthesis rate and leaf area duration at the anthesis stage under combined stress as compared to other RILs. Further, Real-Time gene expression data inferred that GCP 6 and GCP 33 RILs maintained stay-green traits by up-regulating TaCHLD as well as down-regulating TaPaO, TaPPH and TaSGR1 genes at anthesis stage under combined stress, that are known chlorophyll biosynthesis (TaCHLD) and degradation genes respectively. It was also revealed that GCP 6 and GCP 33 RILs maintained higher photosynthesis rate during the anthesis stage under combined stress due to increased carbon fixation resulting from higher TaRbcs, PsbP and TaPsbA genes expression. This study showed that stay-green traits help in stabilizing the yield attributes under combined heat and drought stress in wheat.