Identification Of Drought-tolerant Resources And QTL Analysis For Drought Tolerance In Spring Wheat

Wheat is the grain crop with the second largest growing area in the world.In China,wheat is the most important food,which plays a crucial role in the food safety.Drought is the most significant abiotic stress that restrains the yield improvement of wheat.In this study,local spring wheat cultivars and wheat germplasm introduced from CIMMYT were selected for evaluation of their agronomic traits and physiological traits under water and drought treatment,A recombinant inbred line(RIL)population derived from a cross between Xinjiang local drought-tolerant spring wheat variety "Xinchun 7" and drought sensitive variety "Xinchun 21" was developed and assessed agronomic traits,such as heading stage,plant height,yield,yield compoments,and multiple physiological traits,including canopy temperature,SPAD and NDVI.Illumina iSelect 90K SNP chip was applied to construct a high density genetic linkage map using this spring wheat RIL population,and QTLs conditioning the agronomic and physiological traits were identified.The main results are as follows:1.In the present study,a set of 145 wheat varieties from the germplasm screening nursery of CIMMYT and 7 local spring wheat varieties were selected for physiological and yield traits evaluation for two years under various water conditions.The results indicated that drought stress significantly elevated the canopy temperature,but lowered the grain yield,grain weight per spike,normalized vegetation index,chlorophyll content,plumpness,grain number per spike,1000-grain weight and plant height.Among these,the grain weight per ear,plant height and grain plumpness explained 61.8%of the phenotypic variation of yield traits under sufficient irrigation,so they were the three main factors closely related to the yield.Under drought conditions,the canopy temperature,plant height and plumpness of filling stage were three major factors affecting the yield,accounting for 44.8%of the phenotypic variation of yield traits.Ten genotypes,including 3 local Xinjiang varieties,"Xinchun 11" "Xinchun 23" and "Xinchun 29",were selected as the core parents of the drought resistant breeding for spring wheat in Xinjiang,China.2.A F8 RIL population was developed using a drought tolerant spring wheat variety "Xinchun 7" and a drought sensitive "Xinchun 21" as female and male parents,respectively.The plant height,heading stage,yield,yield related traits,as well as the physiological indictors,such as the canopy temperature,SPAD and NDVI of this RIL population were measured and evaluated for three years under water and drought conditions.The results indicated that plant height,plumpness,1000-grain weight and grain weight per spike were significantly reduced upon drought stress,while the bottom sterile spikes were substantially increased.Under drought condition,the canopy temperature and NDVI were dramatically elevated and decreased,respectively.Particularlly,drought resulted in the elevation of canopy temperature and the reduction of NDVI and SPAD,especially during the grain filling stage.The variations in agronomic traits of the RIL population exhibited a transgressive segregation,suggesting the existence of favorable alleles that control these agronomic traits in both parents.In addition,these variation frequencies showed a continuous distribution,indicating that these traits were conditioned by multiple genes with minor effects.3.After genotyping the RIL population with Illumina iSelect 90K SNP chip,5146 high quality polymorphic SNP markers were selected to construct a high density genetic linkage map.Finally,1047 representice loci were used to construct a genetic linkage map of spring wheat with 2188.35 cM genetic coverage and an average marker interval of 2.09 cM.4.Using the SNP genetic linkage map and DC,DI,DYI,WYI and YHWUEI of three years phenotypic data,a total of 147 QTLs associated with yield and drought tolerance was identified.Of these,26 stable QTLs were identified in three or two years.Among of them,6 QTL controlled the heading stage,1 QTL was related to plant height,1QTL was related to grain weight of spike,1 QTL were related to grain weight of thousand,1 QTL was related to sterile spikelets,5 QTL were involved in NDVI,and 11 QTL controlled the SPAD.These mapped QTLs along with related molecular markers can facilitate the marker assisted selection of spring wheat with increased grain yield and drought tolerance.