Regulates Pathogenicity and Sexual Development of Plus and Minus Strains in Causing Glomerella Leaf Spot on Apple in China.

is a devastating fungal pathogen of diverse plants. Sexually compatible plus and minus strains occur in the same ascus. However, the differentiation mechanism of plus and minus strains remains poorly understood. Here, we characterized a novel Cys2-His2-containing transcription factor CfCpmd1. The plus deletion mutant (Δ+) resulted in slow hyphal growth and a fluffy cotton-like colony, and the minus deletion mutant (Δ-) exhibited characters similar to the wild type (WT). Δ+ led to defective perithecial formation, whereas Δ- produced more and smaller perithecia. The normal mating line was developed by pairing cultures of Δ- and plus WT, whereas a weak line was observed between Δ+ and minus WT. Conidial production was completely abolished in both plus and minus mutants. When inoculated on non-wounded apple leaves with mycelial plugs, Δ- was nonpathogenic because of failure to develop conidia and appressoria, while Δ+ could infect apple leaves by appressoria differentiated directly from hyphal tips, even though no conidia formed. Collectively, our results demonstrate that of is an important gene related to plus and minus strain differentiation, which also affects hyphal growth, sporulation, appressorium formation, and pathogenicity.