Genetic Dissection Of Variations In Chlorophyll Content Of Flag Leaf At Post-anthesis And Yield-related Traits Regulated By Drought Stress

Drought has severely affected the formation of wheat yield in rainfed agricultural areas of northern China.Thus it is of great significance to analyze phenotypic variations and the quatitative genetic basis of grain yield and its related traits regulated by drought stress,and to explore the molecular markers closely linked with these target traits.In this study,an itrogression lines(ILs),deriving from backcross between Jinmai47 as a recurrent parent and Xifeng20 as a donor parent,were used to dissect phenotypic variations and molecular quatitative genetics of chlorophyll content of flag leaf(Chl C),plant height(PH),peduncle internode length(PIL),spike length(SL),grain number per spike(GPS),thousand-grain weight(TGW),effective tiller number(ETN)and plot yield(PY)under drought stress(DS)and well-watered(WW)conditions.It was further to reveal the genetic basis and QTL epression pattern associated with target traits.The results are as follows:1.The phenotypic data of all target traits of wheat ILs and their parents varied widely and were susceptible to water environments and genotypes.The coefficient of variation(5.38-32.19%/DS and 4.46-31.37%/WW)and the diversity index(0.76-0.98/DS and 0.75-0.98/WW)were higher,while the heritability(0.15-0.72/DS and 0.12-0.64/WW)was lower.Chl C had significant or very significant positive correlations(r=0.164*-0.347**)between GPS and TGW.PY had very significant positive correlations GPS(r= 0.427**-0.593**),ETN(r= 0.500**-0.794**),and TGW(r= 0.220**-0.544**),respetively.2.Six hundred pairs of SSR primers were utilized to genotype polymorpheism of wheat ILs and a total of 129 polymorphic SSR markers were screened.The poly morphic rate was up to 21.50%.Depending on early-constructed genetic linkage map,these polymorphic SSR markers was located again.The total length of the new genetic map was 1796.27 cm,of which the average length of each chromosome was 85.54 c M,and the average distance between two markers was 7.53 c M.3.By QTL mapping in wheat ILs,95 additive QTLs were detected to controlling Chl C,PH,PIL,SL,GPS,ETN,TGW,and PY,located 18 chromosomes except for 3B,6A,and 6D.These QTLs explianed phenotypic variations from 0.01% to 5.24%.A total of 122 pairs of epistatic QTLs were detected and mainly mapped on 1B,4A,5B and 7B,which explianed phenotypic variations from 0.10% to 5.37%.All additive and epistatic QTLs interacted with the water environment,which explianed phenotypic variations from 0.01% to 3.72%.4.The genetic basis for these quantitative traits consisted of additive effects,epistasis,additive × water environment interactions,and epistatic × water environment interaction effects.Under different water environments,QTLs controlling these target traits showed different expression patterns.5.There were 21 SSR markers tightly linked with two or more target traits,which mainly distributed on the homologous group I and showed pleiotropic effects.So me key marker intervals on the chromosomes 1B,1D,2A,and 7B,such as Xcnl158-Xgwm273,Xmag976-Xwmc429,Xgwm473-Xwmc766,and Xmag3302-Xgwm400,were invovled in QTLs for three target traits,suggestive of QTL hotspots.This study analyzed the genetic basis of variations in chlorophyll content of flag leaf at post-anthesis and yield-related traits regulated by drought stress.The molecular markers closely linked to the target trait QTLs and the QTL hotspots will provide theoretical basis for the molecular genetic improvement of drought tolerance in wheat yield.