小麦抗麦红吸浆虫QTL定位与关联分析

Wheat midge (Sitodiplosis mosellana Géhin) is an economically important pest insects for wheat production and quality losses in China and other wheat production area around the world. It is documented that breeding wheat cultivars with midge resistance is an efficient and ecologically safe way for midge control. However, for the cripticity of midge detriment,the risk of midge migrating to adjacent plants in the breeding nursery and difficulties of evaluation for wheat response for midge detriment, breeding efforts for midge resistance is not as efficient as other traits in crop plants. Recently, DNA molecular marker, and marker-based selection with tightly-linked markers for trait of interest, offer crucial opportunities for breeding wheat cultivars with trait of interest, such as midge resistance. In Canada, with tightly linked markers, some midge-resistanct wheat lines with Sm1 locus has been developed, as has not been practiced in China for the lack of critical resistant genes (QTLs) adapted to China climate. Therefore, the objective of present study is, using QTL mapping and linkage disequilibrium (LD) analysis methods, i) to map quantitative trait loci (QTLs) and their linked DNA markers in a midge-resistant wheat cultivar "Henong 215" with an RIL (recombinant inbred line) population, ii) to determine the genetic basis for midge resistance in wheat accessions released in Northern China wheat zone within the latest decade, with midge-resistant linked SSR markers and STS marker available, and iii) to establish trait-marker association with DNA markers based on genome-wide association mapping. Results obtained from the present study should be helpful for the acceleration of marker-assisted selection process in domestic wheat midge-resistant breeding practices, and be meaningful in understanding the genetic basis of midge-resistant accessions in China.

麦红吸浆虫是严重影响小麦产量和品质的重要害虫，选育、利用抗虫小麦品种是降低虫害损失最经济有效、生态安全的途径。由于害虫迁飞等因素的影响，小麦的田间抗虫性鉴定准确性、稳定性差，导致小麦抗虫育种工作进展缓慢。分子标记辅助选择可降低其他因素干扰，显著提高育种效率。加拿大已有借助标记辅助选择培育出抗虫品系的成功报道，国内有关小麦对吸浆虫抗性遗传及分子标记的研究相对较少。本研究针对近年来我国小麦主产区吸浆虫为害日趋严重、抗虫小麦品种缺乏和抗虫育种效率低下的的现状，在对大量小麦种质资源抗虫鉴定的基础上，以所构建的重组近交系群体和我国北方冬麦区小麦品种为材料，应用连锁分析、关联分析和抗虫基因连锁标记等手段，定位和分析我国小麦品种吸浆虫抗性主效QTL及其关联标记，明确抗虫资源的遗传多样性，研究结果可为小麦育种提供抗虫资源及辅助选择标记，对利用抗虫小麦品种长期控制吸浆虫为害具有重要意义。

麦红吸浆虫是我国北方麦区的重要虫害，筛选和挖掘抗虫小麦品种的重要染色体区段及其连锁标记，对于提高抗虫育种效率、降低吸浆虫为害具有重要意义。本研究以北方麦区主栽小麦品种构建的自然群体和由抗/感虫小麦种质构建的重组近交系（RIL）群体为材料，进行了抗虫性相关QTL定位与性状-标记关联分析。主要结果如下：（1）在河农215（抗）/烟优361（感）群体中，共检测到3个来自抗虫亲本河农215的QTL，这些QTL（QSm.hbau-4D、QSm.hbau-2B、QSm.hbau-4A）在两年间均稳定存在，其中以QSm.hbau-4D对抗虫性贡献率最高（PVE=11.38%），该QTL位于标记Xbarc105-Xgpw94042之间，距Xbarc105 5.7cM，Xgpw94042 4.2cM。（2）在6218（感）/冀麦24（抗）群体中，4A染色体上的QTL（Xbarc343-QSm.hbau-4A-Xwmc262，染色体区段2.5 cM）在两年3个环境下均可检测到，平均贡献率为8.98%；利用连锁标记，从RIL群体中检测到16个残余杂合株系，并从中分离到对吸浆虫的抗、感表型区分明显的9对近等基因系。（3）利用分布于小麦21条染色体上的273个SSR标记，对137个小麦品种进行了关联分析。供试品种的抗虫性差异明显，品种间遗传多样性丰富（基因多样性指数为0.53），以4A、4D染色体的多样性水平较高；基于亲缘系数，将137个品种划分为5个类群和1个混合群，在两年间检测到11个与抗虫性显著关联的标记，其中Xgwm169-6A与Xgwm108-3B在两年均被稳定检测到。（4）根据两个RIL群体中均在4A上检测到抗虫性QTL的事实，以及关联分析群体中4A染色体上的遗传变异较为丰富的结果，认为在4A上可能存在有重要的抗虫性QTL位点，这一区域应作为下一步研究的重点区域。（5）建立了以估计损失率和百粒虫数为抗性评价指标，在人工虫圃上进行小麦种质资源抗虫性评价的抗虫鉴定方法。