QTL Mapping For Flag Leaf And Spike Related Traits In Wheat(Triticum Aestivum L.)

Flag leaf as an important photosynthetic organ of wheat,which is closely related to grain filling and grain yield.There are also important relationships between spike traits and wheat yield.Genetic analysis and related QTL detection is helpful to understand its genetic mechanism and have a significant theoretical and practical meaning in molecular marker assisted breeding.In this study,The genetic linkage map was constructed from the 133F6-F7 recombinant inbred lines(RIL)which were derived from a cross Lankao 906 and Xiaoyan 81.The main results of QTL analysis of flag leaf length,flag leaf width,flag leaf area,spike length,spikelets per spike,kernels per spike and spikelet compactness were as follows:1.A population of 133 F6-F7 RILs created from Lankao 906 and Xiaoyan 81 were used to constructed the genetic linkage map.1237 pairs of SSR primers were used to detect polymorphism among parents.Among them,298 pairs of primers showed polymorphism in two parents,and the polymorphic rate was 24.1%.Then those polymorphic primers were amplified in the RIL population,202 pairs of primers were detected again,and the bands were clear,accounting for 67.8% of the polymorphic primers,which could be used for QTL mapping.2.Construction of wheat linkage map with IciMappingV3.2(http://www.isbreeding.net).The map consisted of 202 SSR markers,covering 21 chromosomes of wheat,with a total length of 1678.93 cM and an average distance between markers of 8.30 c M.The number of markers included in the A,B and D genomes was 80,66 and 56 respectively.The most widely distributed is the 2A chromosomes,and the least is 1D chromosome.3.A total of 45 QTLs related to flag leaf size and spike traits were detected by complete interval mapping method(CIMM),which were located at 1B,2A,3D,4A,4B,4D,5A,5B,5D,6A,6B,6D,7A and 7D chromosomes.The explanatory phenotypic variation was 3.17%~2.14% and the LOD value ranged from 2.54 to 13.8.14 QTLs were detected in 2 or more environments and all could be expressed stably.The phenotypic variation rate of 20 QTLs was more than 10%.And among them,8 QTLs for leaf width could explain the phenotypic variation of 4.94% to 20.77%,including 4 stable QTLs and 4 main QTLs.The phenotypic variation of 8 QTLs of flag leaf area was 3.17%~16.92%,4 QTLs which were detected in multi-environments and 3 QTLs whose contribution rate was more than 10%.10 QTLs is for spike length including 3 stable QTLs and 4 major QTLs.6 QTLs for spikelets per spike,among which only one was detected in two environments.The contribution rate of 3 QTLs was more than 10%,and the maximum phenotypic variation rate was 20.77%.One of 7 QTLs for kernels per spike as well as one of 6 QTLs for spikelet compactness was detected in 2 environment,and among these QTLs above there were 4 major QTLs for kernels per spike with the contribution rate 6.73%~20.71%,and 3 QTLs for spikelet compactness with the contribution rate 13.46%?14.09%?16.60% respectively.The most widely distributed QTL is 2A chromosomes,the least distributed QTL is 5A and 6D chromosomes.No QTLs associated with flag leaf length were detected in this study.4.5 QTL cluster were detected on chromosomes 2A,4A,4B,6B and 7D,respectively.The QTL cluster on 2A chromosome was Xgwm372~Xbarc15,and the flag leaf width and flag leaf area were controlled.A QTL cluster with flag leaf width,flag leaf area,spike length,kernels per spike and spikelet compactness was detected on the interval Xwmc680 ~Xwmc707 of 4A chromosome.A QTL cluster with flag leaf width,spike length and kernels per spike was detected on the interval Xgwm375~Xwmc238 of 4B chromosome.A QTL cluster with flag leaf width,flag leaf area,spikelets per spike and spike compactness was detected on the interval Xbarc101~Xbarc79 of 6B chromosome.A QTL cluster with flag leaf width,spike length,spikelets per spike and spike compactness was detected on the interval Xgpw2327~Xgpw7683 of 7D chromosome.All the above,45 QTLs associated with flag leaf and spike traits were detected in 6 environments.Only 14 QTLs can be detected in 2 or more environments,most of which were detected in a single environment,especially the spikelets per spike and kernels per spike,which were influenced by the environment.Qfls-4A,Qfla-4A,Qsl-4D.2,Qsps-7A and Qker-5D are five major QTLs that can be stably expressed,which can be used for molecular marker-assisted breeding and can be used as a function QTLs for improving flag leaf size and increasing grain number per spike.