QTL Mapping For Important Quality Traits In Common Wheat

Improvement of wheat quality is very important for vavious wheat-based end-products,and has become a main objective of wheat breeding in China.QTL mapping for quality-related traits would provide a theoretical basis for molecular marker-assisted selection in wheat breeding program.Although the 1B.1R transloction has positive effects on many agronomic traits,it largely reduces wheat quality.Therefore,it is important to study the genetic bases of quality-related traits and estimate the genetic effects of the 1B.1R translocation on yield traits for developing wheat cultivars with high yield and good quality.In addition,grain hardness,high- and low-molecular-weight glutenin subunits and flour color showed large influences on wheat processing quality.The objectives of this study were to map quantitative trait loci(QTL) for color parameters of flour and Chinese white salted noodle(CWSN),polyphenol oxidase(PPO) acitivity,yellow pigment content(YPC), milling traits,gluten quality,flour pasting properties,and Chinese white salted noodle (CWSN) qualities,and investigate the genetic effects of 1B.1R translocation and grain hardness,using a recombinant inbred line(RIL) population derived from a cross between the Chinese wheat cultivars 'PH82-2'(hard and non-1B.1R translocation) and 'Neixiang 188'(soft and 1B.1R translocation) planted in Anyang,Jiaozuo and Taian in 2004-05 and 2005-06 cropping seasons.The main results are summarized below.1.The color parameters of flour and noodles,PPO and YPC were mainly controlled by three genomic regions or loci,grain hardness loci(Ha) on chromosome 5DS,short arm of chromosome 1B(SA1B) or 1RS(Sec1) and Psy-A1 genes on chromosome 7AL.Ha locus had large influences on flour brightness(FL~*),flour yellowness(Fb~*), flour color index(FCI) and PPO activity,explaining 80.3%,57.9%,73.2%and 55.1% of the phenotypic variance,respectively and additionally on grain hardness,accounted for 75.2%of the phenotypic variance.SA1B(1RS) and Psy-A1 genes showed large effects on YPC,Fb~* and Nb~*, accounting for 31.9%and 33.9%,7.8%and 12.6%,and 13.7%and 22.0%of the phenotypic variance,respectively.They also had large effects on flour color parameter a~*(Fa~*) and Kent-Jones color grade(KJ),explaining 26.1%and 35.9%,and 17.2% and 19.3%of the phenotypic variance,respectively,and on noodle brightness(NL~*), accounting for 4.5%and 4.3%of the phenotypic variance,respectively.However, 1RS had no effect on FCI and noodle color paremeter a~*(Na~*),and Psy-A1 genes indicated a small effects on them.The major QTL for PPO activity was located on chromosome 2A,explaining 22.0%of the phenotypic variance,however,Ha locus accounted for the largest effect on PPO activity(55.1%).Two QTL for FPC were mapped on chromosomes 3A and 3B,accounting for 5.9%and 4.9%of the phenotypic variance.Chromosomes 1A,3B and 4A were also associated with YPC,Fa~* and KJ,among which,the QTL on chromosome 4A was stably detected across all environments.A QTL for FCI was located on chromosome 7B in homoeologous region of Psy-A1 genes locus on chromosome 7A.2.Glutenin loci(Glu-B1,Glu-D1 and Glu-A3),SA1B(or 1RS) and Ha locus were mainly contributed to 16 quality parameters.Nine QTL for TW and TKW were detected on homoeologous groups 4,5 and chromosomes 6D and 7A.Four QTL assocated FPC were mapped on chromosomes 3A,3B and 5D,with the mojor QTL associated with Ha locus explaining 27.1 of the phenotypic variance.Among the six QTL for Zeleny sedimentation value,1RS and Glu-D1 showed large effects,accounting for 19.3%and 17.6%of the phenotypic variance.For mixograph parameters,Glu-D1 locus contributed large effects on peak time (MPT) and weakening slope(WS),followed on peak width(MPW) and 8 min width (MTxW),explaining 41.3%,39.7%,16.2%and 24.2%of the phenotypic variance, respectively;SA1B had largest contribution to MTxW,followed on MPW and WS, accounting for 42.2%,9.8%and 11.1%of the phenotypic variance,respectively; Glu-B1 showed a large effect on MPT and relatively less on MPW,MTxW and WS, explaining 18.0%,10.3%,11.0%and 14.2%of the phenotypic variance,respectively; Glu-A3 locus showed less influence on mixograph parameters,explaining from 5.9% to 10.0%of the phenotypic variance.In addition,Ha locus had large effect on MPW, accounting for 21.8%of the phenotypic variance.Ha showed important effects on flour pasting parameters,RVA peak viscosity (RPV),RVA final viscosity(RFV) and RVA setback(RSb),especially on pasting temperature(RPT),explaining 71.5%of the phenotypic variance.In addition, chromosomes 1A,5B and 7D were also associated with RPV.Five QTL were detected on chromosomes 1B,3B,5B,6D and 7A,with the one on chromosome 1B explaining 21.6%of the phenotypic variance.QTL for RSb were mapped on chromosomes 1B, 3B,4B and 7A with little effects.Moreover,two QTL for RVA breakdown(RBd) were found on SA1B and chromosome 6D.Three QTL for Chinese white salted noodle(CWSN) adhesiveness were detected on chromosomes 1A,1B and 4D,with the one associated with Glu-B1,explaining 8.8%of the phenotypic variance.Two QTL on chromosomes 1B and 5D were detected for CWSN springiness,with the one associated with Ha locus accounting for 8.1%of the phenotypic variance.