P-284 - Genomic diversity of wild-grass infecting M. oryzae in Europe

The blast fungus Magnaporthe oryzae is a rapidly evolving, mostly clonal, plant pathogen causing blast disease in wild grasses and cereal crops. While distinct genetic blast fungus lineages have adapted to predominant hosts, host jumps from wild to cultivated grasses occur, leading to new emerging crop diseases. We have recently discovered that clonal lineages of the blast fungus contain highly variable mini-chromosomes (mChr) that drive horizontal gene transfer between host-adapted lineages, implying that wild pathogen populations can serve as genetic reservoirs that enable gene flow to co-domesticated pathogen lineages. However, pathogen populations infecting wild host species are notoriously understudied, limiting our understanding of how they contribute to adaptive evolution in multi-host pathogen populations. Here, we describe a diverse population of blast fungus lineages in northern Italy, the major rice producing region in Europe. We used nanopore whole genome sequencing of 28 isolates, including wild grass isolates and the Oryza-infecting lineage. We found 5 host adapted lineages, including Lolium-, Setaria-, Echinochloa-, Eleusine- and Oryza-infecting lineages, highlighting that diverse pathogen lineages co-occur. We further analyze their genetic makeup and karyotype variation to improve our understanding of the role of mChr in local population dynamics and adaptive pathogen evolution.