Chinese Populations of Magnaporthe oryzae Serving as a Source of Human-Mediated Gene Flow to Asian Countries: A Population Genomic Analysis.

Magnaporthe oryzae, a filamentous heterothallic ascomycete fungus that serves as the causative agent of rice blast disease, is globally distributed in rice-growing regions. Populations shaped by environmental factors and human intervention play important roles in the formation of genetic structure. In this study, population structures and spatiotemporal dynamics were investigated based on large-scale whole genomic sequences of rice-infecting M. oryzae around the world. By analyzing these genetic structures, we identified divergent clades that crossed geographic boundaries. While we observed associations between the isolates and their geographic origins, we also found that there were frequent migration events occurring across Asia in main rice cultivation regions. Within Asia, China was the migration origin, facilitating gene flows to Japan and South Korea. Since the 1970s, the genetic diversity of M. oryzae populations in China has also shown a steadily increasing trend, continuing through to the 2020s. Additionally, our analysis of the evolutionary history of Asian M. oryzae populations provided insights into the population expansion that has taken place in recent decades. Overall, our findings indicate that human-mediated gene flows played a pivotal role in shaping the genetic structure of M. oryzae.