小麦粒重基因TaGW2-6A等位变异的组成分析及育种选择

位于6A染色体的Ta GW2是控制小麦籽粒大小的关键基因,已发现其第8外显子有一个T碱基插入等位变异,其启动子区存在Hap-6A?A及Hap-6A?G等位变异。利用高分辨率熔解曲线分析技术(high resolution melting curve analysis,HRM)和Hap-6A-P1/P2分子标记检测了316份小麦品种(系)的Ta GW2-6A基因在上述2个位点的等位变异,分析了其不同等位变异与粒长、粒宽和千粒重的相关性,并以大面积推广的大粒品种周麦22为例,解析Ta GW2-6A基因优异等位变异在系谱选育中的遗传传递。共检测到61份T碱基插入等位变异(命名为977T基因型)和255份无T碱基插入的等位变异(977?基因型)材料;在977T基因型中,Hap-6A?A(TA)和Hap-6A?G(TG)单倍型材料分别为29份和32份,在977?基因型中,Hap-6A?A(?A)和Hap-6A?G(?G)单倍型材料分别为160份和95份。关联分析表明,977T基因型与977?基因型的粒长(P0.05)、粒宽(P0.001)和千粒重(P0.001)均有显著差异,Hap-6A?A单倍型与Hap-6A?G单倍型的粒长(P0.05)、粒宽(P0.05)和千粒重(P0.001)也有显著差异。Ta GW2-6A基因编码区和启动子区等位变异之间存在相互作用,共同调控小麦籽粒的大小,其中TA单倍型比TG、?A、?G单倍型更能增加小麦的粒宽和粒重,是优异的等位变异组合。周麦22为TA单倍型,系谱分析表明,该等位变异并非来源于亲本周8425B,而是来源于亲本辉县红,且TA单倍型能够稳定遗传,但是在常规育种选择过程中可能会丢失。本研究筛选出的Ta GW2-6A优异等位变异TA单倍型材料及高通量分子检测方法为分子标记辅助育种提供材料和方法依据。

Composition and Selection of TaGW2-6A Alleles for Wheat Kernel Weight

TaGW2 on chromosome 6A is a key gene governing kernel size of wheat (Triticum aestivum L.). There are a single T-base insertion in the eighth exon of TaGW2 (977 bp) and two SNPs (Hap-6A-A and Hap-6A-G) in the promoter region. In this study, 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 and their correlations with kernel length, kernel width, and thousand-kernel weight were analyzed. Furthermore, the TaGW2-6A allelic variations were traced in the pedigree of the famous large-kernel variety Zhoumai 22. In the 977 bp position, 61 and 255 lines were detected with and without the T-base insertion, which were designated 977T and 977- genotypes, respectively. In the 977T genotypes, 29 lines were Hap-6A-A (TA) haplotype and 32 lines were Hap-6A-G (TG) haplotype. In the 977- genotypes, 160 lines were Hap-6A-A (-A) haplotype and 95 lines were Hap-6A-G (-G) haplotype. Significant difference was found in kernel length (P < 0.05), kernel width (P < 0.001) and thousand-kernel weight (P < 0.001) between 977T and 977- genotypes. Similarly, significant difference was also found in kernel length (P < 0.05), kernel width (P < 0.05) and thousand-kernel weight (P < 0.001) between Hap-6A-A and Hap-6A-G haplotypes. The allelic variation in TaGW2-6A encoding region and the promoter region jointly contributed to kernel size, and the TA haplotype was superior to -A, TG, and -G haplotypes in increasing kernel width and weight. According to pedigree analysis, the Zhoumai 22 inherited the TA haplotype from the parent Huixianhong, not form the popular parent Zhou 8425B. This haplotype is inheritable stably but tends to be lost in the process of wheat breeding. The results of this study provide not only a high-throughput molecular technique to detect wheat TA haplotype but also breeding materials in marker-assisted selection of wheat.