Quantitative Trait Loci For Diurnal Flag Leaf Starch Content At Early Filling Stage In Wheat

Wheat is the main food crop in the world. Improving the yield is the main goal inwheat(Triticum asetivum L.) breeding. Starch metabolism in flag leaf which playsimportant roles for photosynthesis is decisive in the yield of wheat. Studying on themetabolism of flag leaf starch, we can learn more about the circadian rhythm of flagleaf starch metabolism and the time-dependent expression of QTLs. This data areuseful for strengthen the photosynthetic capacity and the transport efficiency. It alsoprovides new insights in promoting grain filling and yield. In this experiment, the mappopulation, which was based on168lines derived from a cross between Huapei3×Yumai57, was constructed a genetic linkage map. The content of flag leaf starch weremeasured at6time stages in6different environments. Unconditional and conditionalquantitative trait locus (QTL) analyses on flag leaf starch metabolism were performed,which will provide reference information for gene cloning and molecularmarker-assisted selection. The results are as follows:1. The metabolism of flag leaf starch have circadian rhythmicity. The flag leafstarch content increases from7:00to19:00, reaches maximum value at19:00, thendecreases from19:00to7:00and in7:00flag starch content is in its minimum value.More often, The flag leaf starch content reaches maximum value at19:30, and itsminimum value at5:30.2. A linkage map is comprised357markers covering a total length of2780.9cM,with an average distance of7.79cM between adjacent markers. All of the linkedmarkers were classified into24linkage groups whose an average loci of14.9.3. By combining unconditional and conditional QTL mapping methods, twelveQTLs locus were mapped with eight unconditional QTLs and nine conditional QTLsdetected (five QTLs were both unconditional and conditional QTLs), which weredistributed on9chromosomes:1A,1B,1D,2D,3A,4A,5A,5B,5D,7B and7D. Ofthese, qFLS-1D-1, qFLS-4A, qFLS-7B, qFLS-7D-1and qFLS-7D-2are bothunconditional QTLs and conditional QTLs. qFLS-7D-1which owns high phenotypicvariance were identified in3times as unconditional QTL and4stages as conditionalQTL.8unconditional QTLs which selectively expressed in other time were all detected in T4. Major genes were mainly distributed in chromosomes1D and7D.Unconditional QTLs (FLS-1D-2, qFLS-7D-2, qFLS-7D-3) with phenotypiccontributions higher than10%regulating the metabolism of flag leaf starch couldexplain10.2%-15.8%of the phenotypic variation. The unconditional QTL qFLS-1D-2with the highest phenotypic variance explain15.8%.4conditional QTLs get highlevel expression during T3|T2when conditional QTLs mainly expressed.6conditionalQTLs with phenotypic contributions higher than10%regulating the metabolism offlag leaf starch could explain10.2%-22.5%of the phenotypic variation. Theconditional QTL qFLS-1A with the highest phenotypic variance explain22.5%.