Balesdent MH, Laval V, Noah JM, Bagot P, Mousseau A, Rouxel T. Large-scale population survey of Leptosphaeria maculans in France highlights both on-going breakdowns and potentially effective resistance genes in oilseed rape.
Pest Manag Sci 2024;
80:2426-2434. [PMID:
36750403 DOI:
10.1002/ps.7401]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 01/03/2023] [Accepted: 02/08/2023] [Indexed: 06/18/2023]
Abstract
BACKGROUND
Leptosphaeria maculans, the cause of stem canker of oilseed rape, develops gene-for-gene interactions with its host and shows a high evolutionary potential to 'break down' novel resistance genes (R, Rlm) deployed in cultivars over large areas. For optimal management of R genes, updated knowledge of the population structure of the pathogen is needed. In France, large-scale surveys have been done at 10-year intervals since 2000. Here we report the characterization of a large L. maculans population collected in France in 2019-2020.
RESULTS
A total of 844 isolates were collected from 11 sites in ten French departments and were phenotyped for their virulence against nine Brassica napus R genes. All isolates were virulent toward Rlm2 and Rlm9. Very few isolates were avirulent on Rlm1 (1.8%) and Rlm4 (0.6%). Avirulent isolates toward Rlm7 ('AvrLm7') varied from 67% to 11.3%, depending on the site sampled, illustrating the ongoing breakdown of Rlm7. The decrease of AvrLm7 isolates (29.2% at the national level) compared to the 2010 survey (96.5%) was accompanied by an increase of avirulent isolates on Rlm3 (0% in 2010; 54% in 2019-2020). However, virulent isolates on both Rlm3 and Rlm7, previously rarely detected, were found in all sites with a frequency of 17.3%. Finally, most or all isolates were avirulent on Rlm11 (96.1%), LepR2 (RlmS, 99.8%), and Rlm6 (100%), suggesting these three genes still effectively control the disease.
CONCLUSION
These data will help guide strategies for breeding and deploying resistant oilseed rape varieties against L. maculans in France. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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