小麦新种质H461寡分蘖基因遗传分析及近等基因系创制

Tillering is one of the most important agronomic traits for grain yield and it is also a key component of ideotype in wheat. A new oligoculm wheat line, H461, was developed in our lab last century. The inheritance analysis was conducted in wheat lines H461 and Chuannong 16 ( a wheat cultivar with more spikes per plant ). It seemed that the few tillers was controlled by two major nucleus genes with several minor genes, one of which was a suppressing gene, and was not affected by maternal plants. One of the two major genes was found on 2DS Chromosome based on linkage analysis method with SSR markers and BSA method with SNP chips. The genetic distance between the gene and the linkage marker is only 0.8 cM. This locus can explain 45% of phenotype variations. Currently, we haven't found any reports about tillering related genes in this chromosome region, thus the locus should contain some new tillering related genes. In this program, we plan to map the tillering related genes using recombinant inbred lines crossed from H461×Chuangnong16 based on SSR markers and SNP chips, and uncover genetic effect among these genes . Furthermore, the gene effect of these tillering related genes in different populations (H461×Chuanmai42、H461×Chuanmai107、H461×Mianmai37、H461×CS) will be validated. Finally, marker assist selection for development tillering near-isogenic lines will be conducted for the followed map-based cloning.

分蘖是影响小麦穗数多少并进而影响单产的重要农艺性状，也是小麦品种理想株型的重要构成因子。课题组上世纪末成功创制大穗型寡分蘖新种质H461，与穗数型多分蘖新品种川农16配组分析表明，H461分蘖特性受2对主效核基因和一些微效基因共同作用。结合SSR标记连锁作图和基于SNP芯片的BSA法，在2DS上发现其中一对基因，可解释45%的表型变异，该区段未见报道过分蘖相关基因，因此推测该基因为新分蘖基因。本项目以小麦大穗型寡分蘖新种质H461为核心材料，（1）利用H461×川农16重组自交系群体，结合SSR标记和SNP芯片连锁作图，深挖分蘖相关基因，并揭示遗传互作网络；（2）利用H461×川麦42、H461×川麦107、H461×绵麦37、H461×中国春这3套重组自交系群体，验证分蘖基因遗传效应；（3）同时跟踪鉴定目的基因，创制寡分蘖与多分蘖近等基因系。为分子标记辅助株型育种和基因图位克隆奠定基础。

分蘖是影响小麦穗数多少并进而影响单产的重要农艺性状，也是小麦品种理想株型的重要构成因子。本研究立足于课题组上世纪末成功创制大穗型寡分蘖新种质H461，与多分蘖品种川农16、川麦107以及绵麦37分别构建的重组自交系。结合基因型和表型对分蘖基因进行了遗传解析和近等基因系创制工作，主要取得如下结果：1）多年点表型调查发现H461在不同种植环境、不同生长阶段的分蘖数变化范围在2.32-2.94，而川农为8.65-16.99个分蘖数，川农16的平均分蘖数相比H461，高出了78.05 %（P < 0.01)），两者在分蘖数上的差异极显著。而在重组自交系群体中，最小分蘖数在1.0-2.0之间，最大分蘖数在8.1-25.3之间，表现出超亲分离的现象；同时，群体在10个时期分蘖数的频率分布图也呈现出超亲分离现象，均符合正态分布；2）采用90K SNP芯片技术对H461×川农16重组自交系群体进行基因型鉴定和遗传图谱构建。发现7808个SNP标记的基因芯片在亲本间具有多态性，用于遗传连锁图谱构建。染色体总长3486.44cM，标记间平均间距0.45 cM，所有SNP标记构建了50个连锁群；3）结合多年多点的不同生长发育时期的表型数据，一共检测到3个关于分蘖性状的QTL，分别位于2DL（Qltn.sicau-2D）、2BL（Qltn.sicau-2B）和5AL（Qltn.sicau-5A）。其中Qltn.sicau-2D在多年多点不同生长时期都能重复检测到，最高可以解释19.1%的变异度。Qltn.sicau-2B在一个环境中检测到，最高可以解释14.6%的变异度。Qltn.sicau-5A在一个环境中检测到，最高可以解释9.6%的变异度。通过与前人研究结果比较，未见与Qltn.sicau-2D QTL位点相似的报道，推测该QTL是新发现控制分蘖的主效QTL；4）利用高分辨熔解曲线技术（HRM）对目标QTL在不同遗传背景的群体中（H461×川麦107、H461×绵麦37）验证遗传效应。发现Qltn.sicau-2D位点在两个群体中均能极显著降低分蘖数，平均解释变异46.35%和49.40%；5）通过杂交自交家族法，在高代群体中筛选出10余对分蘖性状近等基因系NIL，其中A3-NIL与B95-NIL作为后续精细定位研究的重点材料。