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

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

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1202775

DOI=10.3389/fpls.2023.1202775

ISSN=1664-462X

ABSTRACT=<p>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 F<sub>2</sub> 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 F<sub>2</sub> population. A major QTL <italic>DM9.1</italic> 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 F<sub>2</sub> populations also validated the presence of <italic>DM9.1</italic>. Kompetitive Allele-Specific PCR (KASP) assay was further carried out to fine map <italic>DM9.1</italic> into 1.0 Mb interval. A KASP marker co-segregating with <italic>DM9.1</italic> 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.</p>