Yu: Identification and genetic mapping of Brassica napus for resistance to pathotype 5X of Plasmodiophora brassicae
Date: May 2018
Term: 3 years
Status: Completed
Researcher(s): Fengqun Yu, Gary Peng, Bruce Gossen, Agriculture and Agri-Food Canada, Saskatoon SK, Stephen Strelkov, University of Alberta, and Sheau-Fang Hwang, Alberta Agriculture and Rural Development
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a
Project Summary
Although clubroot resistant (CR) hybrids are available in Canada, the recent emergence of new pathotypes such as 5X and the erosion of CR in the Canadian resistant hybrids is of concern. The most efficient way to develop canola resistant to 5X is to identify resistance in the species and then transfer resistance into elite canola breeding lines by intraspecific crosses. In a three-year project, researchers identified more than ten B. napus lines highly resistant to pathotype 5X, and five to pathotypes 3A, 2B, 3D and 5X through screening 845 B. napus lines collected worldwide. Two new genetic regions of resistance associated with resistance to pathotype 5X were identified through genome-wide association mapping of resistance to clubroot. One of the best resistant lines has been distributed to canola seed companies.
Clubroot disease, caused by Plasmodiophora brassicae, is continuing to spread in the prairies, posing a serious threat to canola production in western Canada. Although clubroot resistant (CR) hybrids are available in Canada, the recent emergence of new pathotypes such as 5X and the erosion of CR in the Canadian resistant hybrids is of concern. Therefore, it is particularly important to identify and use new sources of CR especially in B. napus for developing canola cultivars to manage the disease. The most efficient way to develop canola resistant to 5X is to identify resistance in the species and then transfer resistance into elite canola breeding lines by intraspecific crosses.
Researchers at Agriculture and Agri-Food Canada in Saskatchewan, with collaborators in Alberta, initiated a three-year project in 2015 to identify new sources of B. napus for resistance to pathotype 5X. In addition, researchers planned to map clubroot resistance (CR) genes and develop markers tightly linked to the genes for use in marker-assisted breeding, which would then facilitate the rapid incorporation of multiple CR genes into elite canola breeding lines.
For the project, a total of 845 B. napus lines were tested for resistance to pathotype 5X. Thirty-one lines with a disease severity index (DSI) of less than 20 per cent were obtained. Seed was increased from all of the resistant lines, which could be used for testing for resistance to any new strains of P. brassicae identified in Canada.
A set of 189 lines were sequenced using next generation sequencing technology, and markers were identified and analyzed to understand the population structure and find sections of DNA associated with resistance to clubroot. The genomic locations of clubroot resistance genes were determined as a first step towards genome-wide association mapping of resistance to clubroot.
As well, one hundred and forty-seven significant SNP markers associated with resistance to pathotype 5X were identified through association mapping in a population consisting of 177 lines chosen from more than 800 B. napus lines collected worldwide. These markers were mapped to chromosomes A03, A09 and C06. In addition, a total of 53 B. napus with different levels of resistance to pathotype 5X were screened against three new and virulent pathotypes 3A, 2B, and 3D based on the Canadian Clubroot Differential (CCD) in 2017. Five lines were found resistant to all of the pathotypes, which were confirmed by inoculating the same pathotypes.
Overall, the project resulted in the identification of more than ten B. napus lines highly resistant to pathotype 5X, and five to pathotypes 3A, 2B, 3D and 5X. Resistance to clubroot associated with two new genetic regions (one on chromosome A09 and the other on C06) were also identified. One of the best resistant lines has been distributed to canola seed companies. Several double haploid (DH) segregating populations are under development. These will provide opportunities on further genetic studies for clubroot resistance.
Full Report PDF: n/a