Fine mapping of an adult-plant resistance gene to powdery mildew in soybean cultivar Zhonghuang 24
Qian Zhou, Bingzhi Jiang, Yanbo Cheng, Qibin Ma, Qiuju Xia, Ze Jiang, Zhandong Cai, Hai Nian
Abstract
Powdery mildew (PM), caused by the fungus Microsphaera diffusa, causes severe yield losses in soybean [Glycine max (L.) Merr.] under suitable environmental conditions. Identifying resistance genes and developing resistant cultivars may prevent soybean PM damage. In this study, analysis of F1, F2, and F8:11 recombinant inbred line (RIL) populations derived from the cross between Zhonghuang 24 (ZH24) and Huaxia 3 (HX3) indicated that adult-plant resistance (APR) to powdery mildew in the soybean cultivar (cv.) ZH24 was controlled by a single dominant locus. A high-density genetic linkage map of the RIL population was used for fine mapping. The APR locus in ZH24 was mapped to a 281-kb genomic region on chromosome 16. Using 283 susceptible plants of another F2 population, the candidate region was fine-mapped to a 32.8-kb genomic interval flanked by the markers InDel14 and Gm16_428. The interval harbored five genes, including four disease resistance (R)-like genes, according to the Williams 82.a2.v1 reference genome. Quantitative real-time PCR assays of candidate genes revealed that the expression levels of Glyma.16g214300 and Glyma.16g214500 were changed by M. diffusa infection and might be involved in disease defense. Rmd_B13 showed all-stage resistance (ASR) to PM in soybean cv. B13. An allelism test in the F2 segregating population from the cross of ZH24 × B13 suggested that the APR locus Rmd_ZH24 and the ASR locus Rmd_B13 may be allelic or tightly linked. These results provide a reference marker-assisted selection in breeding programs.