Dept. of Crop Science, North Carolina State University, Box 7620, Raleigh, NC 27695.
School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA 24061.
G3 (Bethesda). 2019 Sep 4;9(9):2905-2912. doi: 10.1534/g3.119.400195.
Southern Leaf Blight, Northern Leaf Blight, and Gray Leaf Spot, caused by ascomycete fungi, are among the most important foliar diseases of maize worldwide. Previously, disease resistance quantitative trait loci (QTL) for all three diseases were identified in a connected set of chromosome segment substitution line (CSSL) populations designed for the identification of disease resistance QTL. Some QTL for different diseases co-localized, indicating the presence of multiple disease resistance (MDR) QTL. The goal of this study was to perform an independent test of several of the MDR QTL identified to confirm their existence and derive a more precise estimate of allele additive and dominance effects. Twelve F family populations were produced, in which selected QTL were segregating in an otherwise uniform genetic background. The populations were assessed for each of the three diseases in replicated trials and genotyped with markers previously associated with disease resistance. Pairwise phenotypic correlations across all the populations for resistance to the three diseases ranged from 0.2 to 0.3 and were all significant at the alpha level of 0.01. Of the 44 QTL tested, 16 were validated (identified at the same genomic location for the same disease or diseases) and several novel QTL/disease associations were found. Two MDR QTL were associated with resistance to all three diseases. This study identifies several potentially important MDR QTL and demonstrates the importance of independently evaluating QTL effects following their initial identification.
南方叶斑病、北方叶斑病和灰斑病是由子囊菌引起的，是全球玉米最重要的叶部病害之一。此前，在为鉴定抗病数量性状基因座（QTL）而设计的一系列连锁染色体片段代换系（CSSL）群体中，已经鉴定出所有三种病害的抗病 QTL。一些不同疾病的 QTL 共定位，表明存在多个抗病（MDR）QTL。本研究的目的是对已鉴定的几个 MDR QTL 进行独立测试，以确认其存在并得出等位基因加性和显性效应的更精确估计。产生了 12 个 F 家系群体，其中选择的 QTL 在其他均匀遗传背景下分离。在重复试验中对这三个群体进行了三种疾病的评估，并使用先前与抗病性相关的标记进行了基因型分析。所有群体对三种疾病的抗性的成对表型相关性在 0.2 到 0.3 之间，在 alpha 水平为 0.01 时均显著。在所测试的 44 个 QTL 中，有 16 个被验证（在相同的基因组位置被鉴定为相同的疾病或多种疾病），并且发现了一些新的 QTL/疾病关联。有两个 MDR QTL 与三种疾病的抗性有关。本研究鉴定了几个潜在的重要 MDR QTL，并证明了在最初鉴定后独立评估 QTL 效应的重要性。
