Composition And Selection Of TaGW2-6A Alleles For Wheat Kernel Weight

Wheat is a major food staple in many parts of the world and is produced worldwide on more acres than any other crop.Grain yield components of wheat include the number of spikes per plant, number of kernels per spike, and thousand-kernel weight(TKW).Previous studies showed that TKW has the highest heritability among the three components, varying from 59% to 80%.With the improvement of varieties yield levels, spike number per acreage and spikes per plant did not have a corresponding increase or reduce slightly, spike grain weight to become the dominant factor to further improve the level of wheat yield.Selection for TKW in breeding programs is an effective way to improve wheat yield.TaGW2 has been recognized as a crucial gene governing grain size of wheat(Triticum aestivum L.). A single T-base insertion in the eighth exon and two SNPs(Hap-6A-A, Hap-6A-G) in the promoter region of TaGW2 were detected on chromosome 6A.316 wheat varieties(lines) were detected by High Resolution Melting Curve(HRM) analysis and Hap-6A-P1/P2 molecular marker for TaGW2-6A allelic variations. There were totally 61 wheat lines detected as containing T-base insertion(TT genotype) and 255 wheat lines detected as lacking of T-base insertion(tt genotype). Among the TT genotype, 29 wheat lines were detected as Hap-6A-A haplotype(TA genotype) and 32 wheat lines were detected as Hap-6A-G haplotype(TG genotype). Among the tt genotype materials, 160 wheat lines were detected as Hap-6A-A haplotype(tA genotype) and 95 wheat lines were detected as Hap-6A-G haplotype(tG genotype).The correlation analysis among kernel length, kernel width, thousand kernel weight and TaGW2-6A allelic variations was conducted. Results of correlation analysis showed that kernel length was different between TT and tt genotypes(P < 0.05); thousand kernel weight and kernel width were significantly different between TT and tt genotypes(P < 0.001); kernel width and kernel length were different between Hap-6A-A and Hap-6A-G haplotypes(P < 0.05), and thousand kernel weight was significantly different between Hap-6A-A and Hap-6A-G haplotypes(P < 0.001); kernel length,kernel width and thousand kernel weight were different between TA and tA genotypes; kernel length, kernel width and thousand kernel weight were significantly different between TA and tG genotypes; kernel length, kernel width and thousand kernel weight were different between tA TG and tG genotypes. TA genotype was an excellent combination of TaGW2-6A allelic variations, which increase more kernel width and kernel weight than those of tA, TG and tG genotypes.TaGW2-6A allelic variations were traced in the pedigree of large kernel wheat variety Zhoumai 22.Pedigree analysis of Zhoumai 22 showed that TA genotype tends to be lost in the process of wheat breeding; and TA genotype of Zhoumai 22 was not derived from the popular parental material Zhou 8425 B, but inherited from Henan Huixianhong. The high-throughput molecular detection technology and the wheat lines with TA genotype provided the evidence for molecular marker assisted seletion of wheat.