School of Horticulture and Plant Protection, Yangzhou University, Yangzhou, 225009, Jiangsu, China.
USDA-ARS Vegetable Crops Research Unit, Horticulture Department, University of Wisconsin, Madison, WI, 53706, USA.
Theor Appl Genet. 2016 Mar;129(3):507-16. doi: 10.1007/s00122-015-2644-4. Epub 2015 Dec 11.
A dominantly inherited major-effect QTL for powdery mildew resistance in cucumber was fine mapped. Two tandemly arrayed cysteine-rich receptor-like protein kinase genes were identified as the most possible candidates. Powdery mildew (PM) is one of the most severe fungal diseases of cucumber (Cucumis sativus L.) and other cucurbit crops, but the molecular genetic mechanisms of powdery mildew resistance in cucurbits are still poorly understood. In this study, through marker-assisted backcrossing with an elite cucumber inbred line, D8 (PM susceptible), we developed a single-segment substitution line, SSSL0.7, carrying 95 kb fragment from PM resistance donor, Jin5-508, that was defined by two microsatellite markers, SSR16472 and SSR16881. A segregating population with 3600 F2 plants was developed from the SSSL0.7 × D8 mating; segregation analysis confirmed a dominantly inherited major-effect QTL, Pm1.1 in cucumber chromosome 1 underlying PM resistance in SSSL0.7. New molecular markers were developed through exploring the next generation resequenced genomes of Jin5-508 and D8. Linkage analysis and QTL mapping in a subset of the F2 plants delimited the Pm1.1 locus into a 41.1 kb region, in which eight genes were predicted. Comparative gene expression analysis revealed that two concatenated genes, Csa1M064780 and Csa1M064790 encoding the same function of a cysteine-rich receptor-like protein kinase, were the most likely candidate genes. GFP fusion protein-aided subcellular localization indicated that both candidate genes were located in the plasma membrane, but Csa1M064780 was also found in the nucleus. This is the first report of dominantly inherited PM resistance in cucumber. Results of this study will provide new insights into understanding the phenotypic and genetic mechanisms of PM resistance in cucumber. This work should also facilitate marker-assisted selection in cucumber breeding for PM resistance.
黄瓜抗白粉病的主效 QTL 被精细定位。鉴定出两个串联排列的富含半胱氨酸的受体样蛋白激酶基因是最可能的候选基因。白粉病（PM）是黄瓜（Cucumis sativus L.）和其他葫芦科作物最严重的真菌病害之一，但葫芦科植物抗白粉病的分子遗传机制仍知之甚少。在这项研究中，通过与一个优良的黄瓜自交系 D8（PM 感病）进行标记辅助回交，我们开发了一个单片段替换系 SSSL0.7，该系携带来自 PM 抗性供体 Jin5-508 的 95 kb 片段，该片段由两个微卫星标记 SSR16472 和 SSR16881 定义。从 SSSL0.7 × D8 杂交中开发了一个包含 3600 个 F2 植物的分离群体；分离分析证实了在 SSSL0.7 中，黄瓜 1 号染色体上的 Pm1.1 是一个显性主效 QTL，控制 PM 抗性。通过探索 Jin5-508 和 D8 的下一代重测序基因组，开发了新的分子标记。在 F2 植物的一个亚组中进行的连锁分析和 QTL 作图将 Pm1.1 基因座限定在一个 41.1 kb 的区域内，其中预测了 8 个基因。比较基因表达分析表明，两个串联基因 Csa1M064780 和 Csa1M064790 编码相同的富含半胱氨酸的受体样蛋白激酶功能，是最可能的候选基因。GFP 融合蛋白辅助的亚细胞定位表明，两个候选基因都位于质膜中，但 Csa1M064780 也存在于核中。这是黄瓜中首次报道的显性抗白粉病。本研究的结果将为理解黄瓜抗白粉病的表型和遗传机制提供新的见解。这项工作还将有助于黄瓜抗白粉病的标记辅助选择。
