小麦骨干亲本碧蚂4号产量构成因子相关单元型区段解析

Founder parents play an important role for improvement of wheat (Triticum aestivum L.) cultivars in China. Some scientists examined the transmission of gemomic segments from founder parents to their progeny, and found that the derivative cultivars inherited certain gemomic region preferentially from the founder parents, but the reason is not very clear now. Bima 4 is an important founder parent, which was used popularly as a parent in Huang-Huai Rivers Facultative Winter Wheat Region of China. We analized the inheritance of microsatellite alleles of Bima 4 in its derivatives by using 532 SSR primers distributed on the 21 chromosomes of wheat genome. Twenty-seven genomic (haplotypic) regions of Bima 4, which underwent rigorous selection during breeding, were found in our study. Of these haplotypic regions, nine was related to yield component by using a method of association mapping. In the present study, firstly, we will identify the haplotypic regions which are correlated with yield component using a RIL (Recombinant Inbred Line) populatin derived from the cross “Bima 4 × Aikang 58”; secondly, the variation of the haplotypic regions relevant to yield component will be examined in the wheat micro-core collections of China; finally, correlations between the haplotypic regions and yield component will be investigated by the method of association mapping, and excellent haplotypes will be selected through analyzing the genetic effect of different haplotypes in the same haplotypic regions. This study will establish a theoretical and material foundation for making known the genetic mechanism of founder parents and molecular breeding in wheat.

骨干亲本在我国小麦育种中发挥了重要作用。在对骨干亲本及其衍生品种的系谱分析的基础上，研究者发现骨干亲本的许多基因组区段能够被衍生品种优先继承，但原因还不十分清楚。碧蚂4号是我国黄淮冬麦区曾经广泛使用的骨干亲本，申请者利用532个SSR标记分析了碧蚂4号遗传物质在衍生品种的传递特点，发现了27个碧蚂4号高频率传递的基因组（单元型）区段。初步的关联分析发现，9个单元型区段与产量构成因子相关。本项目将以这9个重要单元型区段为切入点，首先以碧蚂4号与矮抗58构建的RIL遗传群体为材料，明确碧蚂4号产量构成因子基因/QTL所在的单元型区段；其次，以小麦微核心种质构成的自然群体为材料，系统评价产量构成因子相关单元型区段在微核心种质中的单元型变异；最后，结合关联分析方法，解析产量构成因子相关单元型区段的遗传效应，筛选出正向效应突出的优异单元型，为揭示骨干亲本形成的遗传本质及分子育种奠定理论和材料基础。

骨干亲本在小麦育种中发挥了重要作用。本项目围绕主要研究内容取得以下进展:（1）利用小麦55K SNP芯片对碧蚂4号及70个衍生品种检测发现，碧蚂4号在1D、2A、2D、4B、4D、5D、6B、6D和7D染色体在育种中受到强烈选择，遗传频率超过0.75。（2）以384份小麦重要品种（系）及其基于5个小麦生态区3年获得的主要农艺性状数据进行关联分析发现，45个在9个或9个以上环境均表现正效应的优异等位变异（涉及31个SNP位点）。4个SNP同时在多个性状表现正效应。例如，AX-111600193-4A的等位变异AA具有提高千粒重、穗粒重和降低株高的作用，AX-110967909-7D的等位变异TT具有提高小穗数和穗粒重的效应；AX-109860828-5B的等位变异AA在千粒重和株高上同时表现正效应。品种具有的优异等位变异数和产量存在极显著正相关（r=0.799，p<0.0001）。碧蚂4号在19个等位变异表现正效应，其中6个在衍生世代的传递频率呈上升趋势，表明碧蚂4号这些基因组区域受到强烈选择。（3）利用碧蚂4号和百农AK58杂交获得的重组自交系群体构建了一张含有2493个bin SNP、总长度4229.67cM的连锁遗传图谱，标记间的平均遗传距离为1.70cM。利用多环境获得的7个主要农艺性状数据定位检测到82个QTL，其中37个增效基因来自碧蚂4号。12个QTL可以在所有环境被检测到，其中6个QTL（QTkw-4D、QKns-4A、QSl-4D、QSl-2D-2、QPh-4D和QFsns-5A）平均贡献率超过10%。碧蚂4号在6个QTL区段（QTkw-4D、QKns-4A、QSl-2D-2、QSl-5A-1、QKns-7D-2和QFsns-5A，这些位点的增效基因均来自碧蚂4号），每个QTL区段中至少在一个SNP位点碧蚂4号等位变异在1~4代衍生品种的遗传频率呈上升趋势，表明这些基因组区域碧蚂4号受到强烈选择。这些表达稳定的QTL区段可能是碧蚂4号骨干亲本形成的重要区段。连锁分析和关联分析比较表明，碧蚂4号等位基因在主要农艺性状表现正效应可能是其能够被衍生品种优先继承的重要原因。研究结果为深入揭示骨干亲本的形成机制奠定了一定的理论基础，同时发现的重要产量相关性状基因组位点为分子标记辅助育种提供了理论依据。