ABSTRACT
Many invasive fungal species coexist as multiple lineages on the same host, but the factors underlying the origin and maintenance of population structure remain largely unknown. Here, we analyzed genetic and phenotypic diversity in isolates of the rice blast fungus (Pyricularia oryzae) covering a broad geographical range. We showed that the four lineages of P. oryzae were found in areas with different prevailing environmental conditions and types of rice grown, indicating niche separation. Pathogenicity tests revealed that specialization to rice subspecies contributed to niche separation between lineages, and differences in repertoires of putative virulence effectors were consistent with differences in host range. Experimental crosses revealed that female sterility and early post-mating genetic incompatibilities acted as strong barriers to gene flow between these lineages. Our results demonstrate that the spread of a pathogen across heterogeneous habitats and divergent populations of a crop species can lead to niche separation and reproductive isolation between distinct invasive lineages.
Competing Interest Statement
This work was partially funded by Bayer Crop Science Singapore, whose role in the study was limited to the collection and selection of 211 isolates, and genotyping of all 886 isolates. Bayer Crop Science Singapore had no additional role in the design, collection and analysis of data and decision to publish.
Footnotes
↵* didier.tharreau{at}cirad.fr
Edited main text and Appendix 1. Included a competing interest statement.