Fine mapping of a novel QTL DM9.1 conferring downy mildew resistance in melon

Xuejun Zhang; Yueming Ling; Wenli Yang; Minghua Wei; Zhenzhu Wang; Meihua Li; Yong Yang; Bin Liu; Hongping Yi; Yang-Dong Guo; Qiusheng Kong

doi:10.3389/fpls.2023.1202775

Fine mapping of a novel QTL DM9.1 conferring downy mildew resistance in melon

Front Plant Sci. 2023 Jun 12:14:1202775. doi: 10.3389/fpls.2023.1202775. eCollection 2023.

Authors

Xuejun Zhang^{1

2

3}, Yueming Ling², Wenli Yang², Minghua Wei⁴, Zhenzhu Wang⁴, Meihua Li², Yong Yang², Bin Liu^{2

3}, Hongping Yi^{2

3}, Yang-Dong Guo¹, Qiusheng Kong^{2

3

4}

Affiliations

¹ College of Horticulture, China Agricultural University, Beijing, China.
² Hami-melon Research Center, Xinjiang Academy of Agricultural Sciences, Urumqi, China.
³ Hainan Sanya Experimental Center for Crop Breeding, Xinjiang Academy of Agricultural Sciences, Sanya, China.
⁴ College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, China.

Abstract

Downy mildew (DM) is a major foliar disease globally causing great economic loss in melon production. Utilizing disease-resistant cultivars is the most efficient approach for disease control, while discovery of disease-resistant genes is crucial for the success of DM-resistant breeding. To address this problem, two F₂ populations were constructed using the DM-resistant accession PI 442177 in this study, and QTLs conferring DM resistance were mapped using linkage map and QTL-seq analysis, respectively. A high-density genetic map with the length of 1096.7 cM and density of 0.7 cM was generated by using the genotyping-by-sequencing data of a F₂ population. A major QTL DM9.1 with the phenotypic variance explained proportion of 24.3-37.7% was consistently detected at the early, middle, and late growth stages using the genetic map. QTL-seq analyses on the two F₂ populations also validated the presence of DM9.1. Kompetitive Allele-Specific PCR (KASP) assay was further carried out to fine map DM9.1 into 1.0 Mb interval. A KASP marker co-segregating with DM9.1 was successfully developed. These results not only provided valuable information for DM-resistant gene cloning, but also offered useful markers for melon DM-resistant breeding programs.

Keywords: QTL; QTL-seq; downy mildew; linkage map; melon.

Grants and funding

This work was supported by The National Natural Science Foundation of China (32060689), the Natural Science Foundation of Xinjiang Uygur Autonomous Region (2020D01A64), the earmarked fund for CARS (CARS-25), the specific research fund of The Innovation Platform for Academicians of Hainan Province (YSPTZX202141), and the Key R&D project of Hubei Province (2021BBA101).