Analysis of the Mating-Type Distribution and Fertility Variation in Magnaporthe oryzae Populations in China

Magnaporthe oryzae exhibits significant genetic polymorphism in paddy fields. This study collected and isolated 832 single-spore isolates from major rice-producing areas of 17 provinces in six geographical regions across China, analyzing their mating-type distribution, fertility variation, and underlying mechanisms. Polymerase chain reaction (PCR) assays revealed a significantly higher proportion of the MAT1-2 mating type (79.21%) than MAT1-1 (20.79%), with severely skewed ratios in some regions. Correlation analysis indicated that mating-type distribution was significantly associated with effective accumulated temperature (≥10 °C). MAT1-1 was predominantly concentrated in regions with 4500–7000 degree-days, whereas MAT1-2 was mainly found in regions with 2500–5000 degree-days. Cross-culture fertility tests yielded an average fertility rate of 36.54% and mean perithecia production of 25.7 per isolate, suggesting generally low fertility, with MAT1-2 isolates showing significantly higher fertility than MAT1-1. This study demonstrates that regional M. oryzae populations in China exhibit both mating-type imbalances and fertility deficiency, suggesting rare genetic recombination in natural populations and evolution primarily driven by asexual reproduction.