| Wheat is a major food crop in China,and the wheat production is important for the food security of our country.Improving yield is the main goal of the wheat breeders.Kernel dimensions and spike length are directly associated with grain yield.Understanding the genetic basis and the molecular mechanism of kernel dimensions and spike length is of great importance to wheat genetic improvement,and will promote the improvement of wheat yield.In this study,to investigate the genetic factors affecting kernel morphology and the association of kernel morphology traits with kernel weight,kernel length(KL),width(KW)and thickness(KT)were evaluated,together with hundred-grain weight(HGW),in a recombinant inbred line population derived from Nanda2419×Wangshuibai.All the traits displayed an approximately normal distribution with obvious transgressive segregation,it suggested that they are controlled by multiple genes.HGW showed significant positive correlations with the three dimension factors,but was more closely correlated with KT and KW than with KL.A whole genome scan revealed four QTLs for KL,one for KW and two for KT,explaining 9.3-41.5%of the phenotypic variations.Of them,QKl.nau-2D,QKt.nau-4B and QKt.nau-5A were newly identified major QTLs.To explore the effects of different QTL combinations on kernel dimensions and HGW,paired QTL analysis was conducted for the five genomic regions associated with kernel dimensions.Increase of KW and KT and reduction of KL/KT and KW/KT ratios always resulted in significant higher grain weight.A strong,negative linear relationship of the KW/KT ratio with grain weight was observed.The QTL controlling kernel dimensions on chromosome 5A was overlapped with QGw.nau-5A in this study.Seven near-isogenic lines(NILs)in different genetic backgrounds were investigated to verify the QTL effect on KL,KW,KT and HGW.The Nanda2419 allele significantly reduced KL and increased KW,KT,HGW of NILs in Wangshuibai and Chuanmai 42 backgrounds,and the Zaoyangmai allele has the same effect in Chuanmai 42 background.The Wangshuibai allele significantly increased KL and reduced KW,KT,HGW of NILs in Zhengmai 9023,Yangmai 17,Mianyang 99-323 and PH691 backgrounds.HL1,controlling spike length,was identified from ND2419 and narrowed down to a 0.9 cM interval flanked by Xcfd53 and DG371 on chromosome 2DS in the previous study.To fine map HL1,based on the HL1 interval collinearity with Brachypodium chromosome 5 and Aegilops tauschii 2D,Chinese Spring sequence,Wangshuibai BAC clone sequence and ND2419,Wangshuibai,Mianyang 99-323 resequencing sequence information,17 polymorphic markers were developed.A high-resolution map of HL1 interval was constructed.According to the genotypes and phenotypes of recombinants,HL1 was finally delimited to 0.35 cM interval flanked by Xwgrc1257 and Xwgrc1205,and co-segregated with Xmag9642 and Xwgrc1808,corresponding to a～100 kb region.WGRC1257,WGRC1808,WGRC1205 and WGRC1366 were used to analyze the allelic variations in mini-core collection(MCC),which includes 267 materials.The correlation coefficients result showed that WGRC1257,WGRC1808,WGRC1205 and WGRC1366 were significantly associated with the spike length.A candidate gene was confirmed based on the HL1 region sequence,and its expression level showed significant difference between the NIL and recurrent parent. |
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