Host adaptation and microbial competition drive Ralstonia solanacearum phylotype I evolution in South Korea

Bacterial wilt caused by the species complex (RSSC) threatens the the cultivation of important crops worldwide. The exceptional diversity of type III secreted effector (T3E) families, high rates of recombination and broad host range of the RSSC hinder sustainable disease management strategies. We sequenced 30 phylotype I RSSC strains isolated from pepper () and tomato () in South Korea. These isolates span the diversity of phylotype I, have extensive effector repertoires and are subject to frequent recombination. Recombination hotspots among South Korean phylotype I isolates include multiple predicted contact-dependent inhibition loci, suggesting microbial competition plays a significant role in evolution. Rapid diversification of secreted effectors present challenges for the development of disease resistant plant varieties. We identified potential targets for disease resistance breeding by testing for allele-specific host recognition of T3Es present among South Korean phyloype I isolates. The integration of pathogen population genomics and molecular plant pathology contributes to the development of location-specific disease control and development of plant cultivars with durable resistance to relevant threats.