Evaluation of mechanisms leading to emergence of new clubroot pathotypes

Term: 3 years
Status: Ongoing
Researcher(s): Stephen Strelkov, Sheau-Fang Hwang, Yoann Aigu, Sandra Velasco-Cuervo, U of A
SaskOilseeds Investment: $85,388
Total Project Cost: $341,550
Funding Partners: RDAR, ACPC

Objective

The main aim of the research is to determine the genetic mechanisms behind increased P. brassicae virulence and the emergence of novel pathotypes in order to improve clubroot management. The specific objectives of the proposed research are to:

i. enhance the quality and quantity of the Canadian genome database for P. brassicae;

ii. investigate the importance of mutations, recombination events, and large sequence variations

in the rapid emergence of new pathotypes of P. brassicae;

iii. identify candidate events contributing to pathotype shifts; and

iv. provide knowledge to enhance breeding programs aimed at developing canola with more durable clubroot resistance.

Project Description

Clubroot, caused by Plasmodiophora brassicae, is a major threat to canola production in Canada. The use of clubroot-resistant (CR) cultivars has been a key strategy in managing this disease.

However, the effectiveness of this important tool has been compromised by the rapid emergence of new pathotypes capable of overcoming host resistance. Currently, 43 P. brassicae pathotypes have been identified in Canada, with 25 of these able to overcome resistance in at least some CR canola cultivars. In addition to the most prevalent 'resistance-breaking' pathotypes 3A and 3D, numerous other pathotypes have been discovered, with new ones emerging annually.

Of particular concern is the identification of new pathotype variants, such as pathotype 9D, which can overcome resistance in all second-generation CR cultivars tested to date. The emergence of these new pathotypes threatens sustainable canola production, underscoring the urgency in understanding the mechanisms driving their evolution. This knowledge gap impedes the development of durable clubroot resistance and its effective deployment in regions infested with clubroot.

Various mechanisms, including meiotic and mitotic genetic recombination, structural variants, rearrangements, and large sequence variations, play crucial roles in pathogen evolution. While mutations may contribute to pathogen diversity, studies have shown two P. brassicae population clusters based on samples analyzed from the Canadian Prairies. The objectives of the proposed research are to: (i) enhance the quality and quantity of the Canadian genome database for P. brassicae; (ii) investigate the importance of mutations, recombination events, and large sequence variations in the rapid emergence of new pathotypes of P. brassicae; (iii) identify candidate events contributing to pathotype shifts; and (iv) provide knowledge to enhance breeding programs aimed at developing canola with more durable clubroot resistance. The main aim of the research is to determine the genetic mechanisms behind increased pathogen virulence and the emergence of novel pathotypes in order to improve clubroot management.