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Virulence profiling of Phytophthora sojae based on genomic signature of avirulence genes

Genevieve Arsenault-Labrecque: Université Laval

<div><em>Phytophthora sojae</em>, causing Phytophthora Root Rot (PRR), has been present in Canada since 1950. The expansion of Canadian soybean over the years has given this pathogen a new niche to establish its devastating presence. The best method to control its spread is through the use of soybean varieties carrying resistance genes (<em>Rps</em>) that provide immunity against <em>P. sojae</em> isolates with the corresponding avirulence gene (<em>Avr</em>). Breeders are thus confronted with the need to introgress <em>Rps</em> genes based on the <em>P. sojae </em>pathotypes found in the environment; however, this information is constantly incomplete because of the rapid evolution of the pathogen, and confounded by unwieldy phenotyping methods. This project aims to determine the presence and distribution of virulence profiles (pathotypes) of <em>P. sojae</em> in Canada, based on the seven most important <em>Rps</em>-<em>Avr</em> relationships. For this purpose, a collection of 31 <em>P. sojae</em> isolates, representing the most common pathotypes found in Canadian fields, were targeted for whole-genome sequencing. Different gene mutations directly linked to seven <em>Avr </em>genes from <em>P. sojae</em>, mostly gene suppressions and SNPs, were discovered. These findings corroborate some previous reports, and highlight new findings, while demonstrating specificity linked to the geographical context. Based on these genomic signatures, a multiplex PCR is being developed to help breeders in the selection of specific resistance genes against PRR.</div>