小麦分蘖数和单株穗数QTL定位及上位性分析

QTLs Mapping and Epistasis Analysis for the Number of Tillers and Spike Number per Plant in Wheat

为了明确小麦分蘖性状和单株穗数的遗传基础，以中国春（母本）和兰考大粒（父本）杂交获得的F2群体为作图群体，构建了含169个分子标记的遗传连锁图谱。将F2：3家系分别种植于陕西乾县、岐山和杨凌三地，利用完备区间作图方法对小麦冬前分蘖、春季分蘖和单株穗数进行多环境联合QTL分析，共检测到21个相关的加性QTL位点。其中，6个冬前分蘖QTL位于2A、2D、5D和7A染色体上，单个QTL可解释1.38%～6.73%的表型变异；7个春季分蘖QTL位于1A、2D、4B、5D、7A和7D染色体上，单个QTL可解释1.97%～32.60%的表型变异；8个单株穗数QTL位于1A、2B、2D和4B染色体上，单个QTL可解释2.29%～41.21%的表型变异。共检测到30对加性×加性上位性QTL。其中，控制冬前分蘖的为1对，可解释21%的表型变异；控制春季分蘖的为20对，可解释0.59%～48.7%的表型变异；控制单株穗数的为9对，可解释0.08%～22.18%的表型变异。控制冬前分蘖、春季分蘖和单株穗数的加性QTL存在差异，同一QTL在不同性状中的遗传贡献率也不同；基因间上位性效应以春季分蘖最大，单株穗数次之，冬前分蘖最小，且不同性状涉及的QTL位点具有差异。小麦分蘖遗传主要受加性效应控制，本研究初步定位到的一些重要QTL可为进一步精细定位、基因挖掘和高产育种的分子标记辅助选择提供依据。

QTL for wheat tiller traits, including the tillering in pre winter and spring, number of effective tillers and their linked molecular markers are to be identified for wheat yield improvement with marker assisted selection. In the present study, a total of 327 F2 lines from the cross between Chinese Spring （female） and Lankaodali （paternal） were planted in Qianxian, Qishan and Yangling of Shaanxi Province, respectively. A genetic map was constructed based on 167 SSRs and 2 EST markers. QTL analysis was conducted with multi environment model by the software QTL ICIMapping V3.2. 6 QTLs were located on chromosomes 2A, 2D, 5D and 7A, were found for tillering in pre winter, which explaining 1.38%～6.73% of phenotypic variance; 7 QTLs were detected for tillering in spring, which explaining phenotypic variance from 1.97%~32.60%; and 8 QTLs for effective tillering in harvest were mapped on 1A, 2B, 4B and 2D chromosome, accounting for 2.29%～41.21% of phenotypic variance in multi environment model. There were 30 pairs of additive × additive epistasis QTLs in total detected. Among those, one was for tillering in pre winter and explained 21% of the phenotypic variation; 20 pairs were for tillering in spring detected, which explained phenotypic variance from 0.59%～48.7%; and 9 pairs for effective tiller, accounting for 0.08%～22.18%% of phenotypic variance. Additive QTL for pre winter tillering, spring tillers and spike number per plant was different, the expression degree of the same additive QTL also were different at different stage; the epistatic effect of spring tillers had the strongest effect, then the spike number per plant, that of pre winter tillering was the minimum effect. And the chromosome QTL locus at different period may have big differences. Wheat tillering was mainly controlled by additive effects, the identified molecular markers related to the tiller traits in this study will benefit for marker assisted selection in breeding programs.