In sub-Saharan Africa, maize is the key determinant of food security for smallholder farmers. The sudden outbreak of maize lethal necrosis (MLN) disease is seriously threatening the maize production in the region. Understanding the genetic basis of MLN resistance is crucial. In this study, we used four biparental populations applied linkage mapping and joint linkage mapping approaches to identify and validate the MLN resistance-associated genomic regions. All populations were genotyped with low to high density markers and phenotyped in multiple environments against MLN under artificial inoculation. Phenotypic variation for MLN resistance was significant and heritability was moderate to high in all four populations for both early and late stages of disease infection. Linkage mapping revealed three major quantitative trait loci (QTL) on chromosomes 3, 6, and 9 that were consistently detected in at least two of the four populations. Phenotypic variance explained by a single QTL in each population ranged from 3.9% in population 1 to 43.8% in population 2. Joint linkage association mapping across three populations with three biometric models together revealed 16 and 10 main effect QTL for MLN-early and MLN-late, respectively. The QTL identified on chromosomes 3, 5, 6, and 9 were consistent with the QTL identified by linkage mapping. Ridge regression best linear unbiased prediction with five-fold cross-validation revealed high accuracy for prediction across populations for both MLN-early and MLN-late. Overall, the study discovered and validated the presence of major effect QTL on chromosomes 3, 6, and 9 which can be potential candidates for marker-assisted breeding to improve the MLN resistance.

中文翻译：

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四个双亲群体中与玉米致死性坏死抗性相关的基因组区域的发现和验证。


在撒哈拉以南非洲，玉米是小农粮食安全的关键决定因素。突如其来的玉米致命性坏死病（MLN）严重威胁着该地区的玉米生产。了解 MLN 耐药性的遗传基础至关重要。在本研究中，我们使用四个双亲群体应用连锁作图和联合连锁作图方法来识别和验证 MLN 耐药性相关的基因组区域。所有群体均使用低至高密度标记进行基因分型，并在人工接种下针对 MLN 的多种环境中进行表型分析。在疾病感染的早期和晚期阶段，所有四个群体的 MLN 抗性表型变异显着，遗传力为中等到高。连锁作图揭示了 3、6 和 9 号染色体上的三个主要数量性状基因座 (QTL)，这些基因座在四个群体中的至少两个群体中一致检测到。每个群体中由单个 QTL 解释的表型方差范围为群体 1 中的 3.9% 到群体 2 中的 43.8%。使用三个生物识别模型对三个群体进行联合连锁关联作图，共同揭示了 MLN-early 和 MLN- 的 16 和 10 个主效应 QTL。分别迟到了。 3、5、6、9号染色体上鉴定的QTL与连锁图谱鉴定的QTL一致。岭回归最佳线性无偏预测与五倍交叉验证揭示了 MLN 早期和 MLN 晚期跨群体预测的高精度。总体而言，该研究发现并验证了 3、6 和 9 号染色体上主效应 QTL 的存在，这些 QTL 可能是标记辅助育种以提高 MLN 抗性的潜在候选者。