Molecular Mapping Of Drought Restistant And Water Saving Related Traits In Wheat(Triticum Aestivum L.)

Wheat is likely subjected to different degrees of drought stress in different growthdevelopment from seedling stage， vegetative stage to filling stage. Seedling vigour andsenescence related traits at filling stage were important to drought tolerance and high yield. Inorder to well understand the drought tolerance，207F2:5recombinant inbred lines (RILs)derived from the Jingdong8/Aikang58cross were used to investigate above-mentioned traitsand yield components under limited and full irrigation environments in Beijing and Gaoyi，Hebei province， during the2011-2012and2012-2013cropping seasons. The RILs weregenotyped with149SSR markers， and QTLs for all traits were analyzed by inclusivecomposite interval mapping (ICIM).1. Four traits-Normalized difference vegetation index (NDVI) and ground cover (GC)before winter and in late spring-were used for describe the seedling vigour. Thirty-sevenQTLs for seedling vigour distributed on14chromosomes for the seedling traits wereidentified；18were on genome A chromosomes，8on genome B chromosomes and11ongenome D chromosomes. QTLs QGCs.caas-3B.1，QGCw-caas-1D and QGCw-caas-5D withover-dominance effects explained more than20%of the GCs variation, andQNDVIw-caas-6D. QGCs-caas-6A and QGCw-caas-5B with stable additive effects explainedmore than10%of the phenotypic variation.2. QTLs for leaf senescence related traits and heading dates (HD) were analyzed byinclusive composite interval mapping (ICIM). Forty-five QTLs distributed on15chromosomes, in which10,10,9,9and7QTLs were found for Normalized differencevegetation index at Zadoks47(NDVIv), NDVIg at Zadoks75, leaf senescence rate (LSR),leaf senescence score by visual (LSS) and HD, respectively, across all eight environments.QHD.caas-5B on5B between Xgwm371and Xgwm499explained15.3-29%of phenotypicvariation (PV) in limited irrigations and9.8-27.3%of PV in full irrigations. Two new QTLswere detected; QNDVIv.caas-5B with22.9-35.9%of PV and QNDVIg.caas-4D with11.5-28.5%of PV. A major QLSR.caas-4D expressed opposite effects in different sites. QNDVIg.caas-1A.1, QLSS.caas-1A, QLSS.caas-2D.1and QLSR.caas-3B were detected onlyin limited irrigation.3. The number of QTLs detected for plant height (PH)，thousand kernel weight (TKW)，kernel number per spike (KNS)，spike number (NS)，and grain yield (GY) were3，10，8，7and9， respectively， across all eight environments. PH QTLs on chromosomes4D and6A， explaining above61.3%of the phenotypic variation， were stably expressed in allenvironments. The allele from Aikang58at QPH.caas-4D reduced PH by11.1-16.6%andTKW by2.6-3.7%, but increased KNS by3.7-3.8%and NS by2.9-4.2%. The allele fromAikang58at QPH.caas-6A locus reduced PH and TKW by8.0-10.4%and6.5-8.2%，respectively， whereas increased KNS by2.4-3.5%and NS by2.0-4.6%. QTKW.caas-4B andQTKW.caas-5B.1were stably detected and significantly associated with either KNS or NS.Major KNS QTLs QKNS.caas-4B and QKNS.caas-5B.1and the GY QTL QGY.caas-3B.2were only detected in water-limited environments and thus could be useful in improving yieldunder drought stress.