Present address: Key Laboratory of Agro-biodiversity and Pest Management of Education Ministry of China, Yunnan Agricultural University, Kunming, 650201, Yunnan, China.
Sex at the origin: an Asian population of the rice blast fungus Magnaporthe oryzae reproduces sexually
Article first published online: 7 FEB 2012
© 2012 Blackwell Publishing Ltd
Volume 21, Issue 6, pages 1330–1344, March 2012
How to Cite
SALEH, D., XU, P., SHEN, Y., LI, C., ADREIT, H., MILAZZO, J., RAVIGNÉ, V., BAZIN, E., NOTTÉGHEM, J.-L., FOURNIER, E. and THARREAU, D. (2012), Sex at the origin: an Asian population of the rice blast fungus Magnaporthe oryzae reproduces sexually. Molecular Ecology, 21: 1330–1344. doi: 10.1111/j.1365-294X.2012.05469.x
- Issue published online: 6 MAR 2012
- Article first published online: 7 FEB 2012
- Received 9 September 2011; revision received 13 December 2011; accepted 17 December 2011
- female fertility;
- Magnaporthe oryzae;
- mating type;
- population genetics;
- sexual reproduction
Sexual reproduction may be cryptic or facultative in fungi and therefore difficult to detect. Magnaporthe oryzae, which causes blast, the most damaging fungal disease of rice, is thought to originate from southeast Asia. It reproduces asexually in all rice-growing regions. Sexual reproduction has been suspected in limited areas of southeast Asia, but has never been demonstrated in contemporary populations. We characterized several M. oryzae populations worldwide both biologically and genetically, to identify candidate populations for sexual reproduction. The sexual cycle of M. oryzae requires two strains of opposite mating types, at least one of which is female-fertile, to come into contact. In one Chinese population, the two mating types were found to be present at similar frequencies and almost all strains were female-fertile. Compatible strains from this population completed the sexual cycle in vitro and produced viable progenies. Genotypic richness and linkage disequilibrium data also supported the existence of sexual reproduction in this population. We resampled this population the following year, and the data obtained confirmed the presence of all the biological and genetic characteristics of sexual reproduction. In particular, a considerable genetic reshuffling of alleles was observed between the 2 years. Computer simulations confirmed that the observed genetic characteristics were unlikely to have arisen in the absence of recombination. We therefore concluded that a contemporary population of M. oryzae, pathogenic on rice, reproduces sexually in natura in southeast Asia. Our findings provide evidence for the loss of sexual reproduction by a fungal plant pathogen outside its centre of origin.