Screening and Functional Analysis of Genes for Resistance to Powdery Mildew in Watermelon

Powdery mildew (PM) is a major fungal disease that causes huge economic losses by impacting thousands of plant species, including Cucurbitaceae crops, such as watermelon ( Citrullus lanatus ). Although powdery mildew is caused by a widespread watermelon pathogen, the molecular mechanism remains unclear. In this study, one watermelon powdery mildew isolate was identified as Podosphaera xanthii . According to the distinct infections of powdery mildew on DuanMan (Middle resistance to PM) and Kexi (Susceptible to PM), fifteen ClaMLO genes expression level were detected, while only ClaMLO1 and ClaMLO2 were significantly regulated at different invasion period.. Bioinformatics analysis further showed that ClaMLO gene family were very conservative and ClaMLO2 , ClaMLO7 and ClaMLO13 were clustered in clade V. Subsequent subcellular localization experiments proved that ClaMLO1 localized in the cell nucleus, and silencing ClaMLO1 in watermelon enhanced resistance to powdery mildew. Generally, our study identified one gene, named ClaMLO1 . It may be responsible for the successful invasion of watermelon powdery mildew, laying a theoretical foundation for molecular breeding of watermelon.