Variation in copy number, expression, and sequence of Avr1a/avr1a among populations of the oomycete plant pathogen, Phytophthora sojae
D. WICKRAMASINGHE (1), S. Stewart (2), A. Robertson (2), A. Dorrance (1)
(1) Department of Plant Pathology, Ohio State University, Wooster, OH, U.S.A.; (2) Department Plant Pathology, Iowa State University, Ames, IA, U.S.A.
Phytopathology 101:S190

Phytophthora sojae has reemerged as a prominent pathogen in some areas of the Midwest due to the pathogen’s ability to adapt to many of the resistant (Rps) genes, deployed in soybean cultivars. Recent research identified several Avr genes namely, Avr1a, Avr3a and Avr3c, and showed they belong to the RXLR family of effectors. Several mechanisms by which these effectors may contribute to changes in virulence in pathogen populations were proposed including the copy number variation of avirulence genes, differential regulation of the transcription of the genes and changes in amino acid composition of the proteins. However, this research only evaluated a few standard isolates. We compared the Avr1a locus across field isolates of P. sojae from Iowa and Ohio to discern which mechanism(s) maybe more critical at the population level. Preliminary data from both Iowa and Ohio suggest that the variation in copy number in the putative Avr1a gene may not be a major contributor to the variation in the avirulence/virulence response towards Rps1a.