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

<i>Magnaporthe oryzae</i> 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 <i>MAT1-2</i> mating type (79.21%) than <i>MAT1-1</i> (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). <i>MAT1-1</i> was predominantly concentrated in regions with 4500-7000 degree-days, whereas <i>MAT1-2</i> 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 <i>MAT1-2</i> isolates showing significantly higher fertility than <i>MAT1-1</i>. This study demonstrates that regional <i>M. oryzae</i> 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.