Twenty Years of Population Survey in France Suggests Pyramiding and in Rapeseed Is a Risky Resistance Management Strategy.

Strategies for plant resistance gene deployment aim to preserve their durability to highly adaptable fungal pathogens. While the pyramiding of resistance genes is often proposed as an effective way to increase their durability, molecular mechanisms by which the pathogen can overcome the resistance also are important aspects to take into account. Here, we report a counterexample where pyramiding of two resistance genes of , and , matching the avirulence genes and , respectively, favored the selection of double-virulent isolates. We previously demonstrated that the presence of a functional gene in an isolate masks the recognition. was massively deployed in France since 2004. populations were surveyed on a large scale (>7,600 isolates) over a period of 20 years, and resistance gene deployment at the regional scale was determined. Mutations in isolates overcoming both resistance genes were analyzed. All data indicated that the simultaneous success of , the deployment of varieties pyramiding and , along with the decrease in areas cultivated with only, contributed to the success of virulent isolates toward , and more recently to both and . Experimental field assays proved that resistance gene alternation was a better strategy compared with pyramiding in this context. Our study also illustrated an unusually high sequence diversification of and under such a selection pressure, and identified a few regions of the AvrLm4-7 protein involved in both its recognition by and in its masking ability. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.