QTL mapping for leaf senescence-related traits in common wheat under limited and full irrigation

Leaf senescence is an important trait for yield improvement under stress. In the present study, 207 F-2:4 random inbred lines (RILs) derived from the Jingdong 8/Aikang 58 cross were investigated under limited and full irrigation environments at two locations during the 2011-2012 and 2012-2013 cropping seasons. The RILs were genotyped with 149 SSR markers and QTLs for leaf senescence-related traits and heading dates (HD) were analyzed by inclusive composite interval mapping. The broad sense heritabilities of normalized difference vegetation index at Zadoks47 (NDVIv) and at Zadoks75 (NDVIg), leaf senescence rate (LSR), leaf senescence scored visually (LSS), leaf area index (LAI) and HD were 0.37-0.54, 0.39-0.48, 0.4-0.45, 0.56-0.58, 0.64-0.79 and 0.82-0.86, respectively. There were significant correlations between NDVIg and LSR (r = -0.55 to -0.70), NDVIg and LSS (r = -0.61 to -0.61), and LSS and LSR (r = 0.48-0.68). NDVIv and LAIv explained 18.5 % and 19.4 % of the variation in grain yield under limited irrigation, respectively. Forty five QTLs were distributed on 15 chromosomes. The respective numbers of QTLs for NDVIv, NDVIg, LSR, LSS and HD were 10, 10, 9, 9 and 7 across all eight environments. Previously unreported QTLs were found on chromosomes 1A, 2D, 5B, 7A and 7D for NDVI, on 6D for LSR and 5B for LSS. QNDVIv.caas-4A explained 23.7-56.6 % of the phenotypic variation (PV) for NDVIv and was stably expressed in four environments. In contrast, QNDVIg.caas-4B.2 explained 13.2-16.0 % of PV but was only expressed in full irrigation. Pleiotropic QTLs were detected; QNDVIv.caas-5B, explaining 22.9-35.9 % of PV, had an effect on LSS, and QNDVIg.caas-4D, accounting for 11.5-28.5 % of PV, also influenced NDVIv. QTLs controlling LSR, QLSR.caas-4D and QLSR.caas-3B, also increased thousand kernel weight and grain yield, indicating that rapid senescence increased grain filling rate. Some QTLs such as QNDVIg.caas-1A.1, QLSR.caas-2A, QLSS.caas-2B, QLSS.caas-3B, QLSS.caas-5B and QLSS.caas-2D.1 were detected only under limited irrigation. These drought stress-induced QTLs could be valuable for improving drought resistance in wheat.