Peng: Characterization and Utilization of Newly Identified Resistance Sources for Sustainable Clubroot Control on Canola
Date: January 2015
Term: n/a
Status: Completed
Researcher(s): Gary Peng, Fengqun Yu and Kevin Falk, Agriculture and Agri-Food Canada, Saskatoon SK
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a
Project Summary
Clubroot, caused by the pathogen Plasmodiophora brassicae (Pb) can be a devastating disease to canola crops. Since 2009, resistant canola cultivars have been available in Canada but all of them are based on a single dominant R gene. The aim of this project was to identify clubroot resistant (CR) genes and develop diversified clubroot resistant canola germplasms to support a long-term host resistance strategy. As a result of the project CR genes Rcr1, Rcr2 and Rcr3 have now been validated, mapped and incorporated into elite AAFC B. napus and B. rapa canola lines, and Rcr6 into B. carinata canola germsplasms. These stable germplasm materials can now be made available to industry through tech transfer agreements.
Clubroot, caused by the pathogen Plasmodiophora brassicae (Pb) can be a devastating disease to canola crops. Since 2009, resistant canola cultivars have been available in Canada but all of them appear to be based on a single dominant R (resistance) gene. There is a lack of genetic characterization of R genes in these canola cultivars and it appears that different cultivars may share similar resistance genes. For effective long-term management of clubroot in western Canada, there is a need to broaden the clubroot resistant (CR) genetic arsenal. Recent reports on the pathotype 5X in Alberta showed that this race is virulent on all resistant commercial cultivars in production; clearly this is a serious concern.
The aim of the project was to identify CR genes and develop resistant canola germplasms to support a long-term host resistance strategy by diversifying CR genetic background. This work includes the characterization of CR genes, development of molecular markers linked to the CR genes for marker-assisted selection (MAS), and efficient introgression of selected CR genes into canola breeding lines using MAS.
Researchers started with a broad range of clubroot resistant materials obtained from an earlier study. Since 2009, over 1,000 Brassica lines, mostly B. rapa, have been screened at AAFC Saskatoon, with 21 candidates from B. rapa, B. nigra, B. napus and B. oleracea found to be highly resistant. Initially, resistant candidates were tested against pathotypes 2, 3, 5, 6 and 8 of P. brassica (races found in Canada prior to 2013) to assess the range of effectiveness, and several candidates showed strong resistance to all the pathotypes. Among the 21 highly resistant lines, ten B. rapa and one B. nigra lines showed complete resistance against the predominant race of Pb (pathotype 3) found in Alberta, and these ten CR lines were selected for the experiment. The resistance/susceptibility for each accession to each pathogen was determined individually.
Simple sequence repeat (SSR) markers were used for rough/fine mapping of CR genes. Over 2,000 SSR markers, distributed on 19 linkage groups of B. napus were developed at AAFC Saskatoon Research Centre. This AAFC microsatellite marker system identified a total of 104 polymorphic markers, which were then used to screen a larger population of 1,587 plants, each of which were also tested for clubroot reaction. As a result, the clubroot resistance genes Rcr1, Rcr2, Rcr3 and Rcr6 have been validated and mapped, with molecular markers developed and used for MAS during introgression of clubroot resistance into canola germplasms.
A genomewide selection tool (6K SNP array) was used to identify the most suitable candidate carrying the CR gene Rcr1 in early stages of resistance introgression (or backcrossing) to speed up the process of CR germplasm development. This technology, with substantial improvements now involving 60K SNP markers, can be a useful selection tool during interspecific hybridization. The CR genes Rcr1, Rcr2 and Rcr3 have now been incorporated into elite AAFC B. napus and B. rapa canola lines, and Rcr6 into B. carinata germsplasm. These stable germplasm materials can now be made available to industry through tech transfer agreements. Preliminary testing also showed that lines carrying Rcr1 might resist the newly-found pathotype 5X, which is very encouraging.
Scientific Publications
Chu M, Yu F, Falk KC, Liu X, Zhang X, Chang A, Peng G. 2013. Identification of the clubroot resistance gene Rpb1 and introgression of the resistance gene into canola breeding lines using a marker-assisted selection approach. Acta Horticulturae 1005: 599-605.
Peng G, Pageau D, Strelkov SE, Lahlali R. Hwang SF, Hynes RK, Anderson K, McDonald MR., Gossen BD, Turkington KT, Falk CK, Yu FQ, Boyetchko SM, McGregor L. 2013. Assessment of crop rotation, cultivar resistance and Bacillus subtilis biofungicide for control of clubroot on canola. Acta Horticulturae 1005: 591-598.
Lahlali R, Peng G, Gossen BD, McGregor L, Yu FQ, Hynes RK, Hwang SF, McDonald MR, and Boyetchko SM. 2013. Evidence that the biofungicide serenade (Bacillus subtilis) suppresses clubroot on canola via antibiosis and induced host resistance. Phytopathology (Impact Factor : 2.75) 103: 245-254 (Editor's Pick)
Rahman H, Peng G, Yu F, Falk KC, Kulkarni M, Selvaraj G. 2014. Genetics and breeding for clubroot resistance in Canadian spring canola (Brassica napus L.). Can. J. Plant Pathol. 36 (Suppl. 1): 122-134.
Lahlali R, Peng G. 2014. Clonostachys rosea confers suppression of clubroot on canola via antibiosis and induced host resistance. Plant Pathology (Impact Factor: 2.969) 63:447-455.
Lahlali R, McGregor L, Song T, Gossen BD, Narisawa1 K, Peng G. 2014. Heteroconium chaetospira induces resistance to clubroot via upregulation of host genes involved in jasmonic acid, ethylene, and auxin biosynthesis. PLoS One (Impact Factor: 3.534) 9:4 e94144.
Peng G, Lahlali R, Hwang SF, Pageau D, Hynes RK, McDonald MR, Gossen BD, Strelkov SE. 2013. Crop rotation, cultivar resistance, and fungicides/biofungicides for managing clubroot (Plasmodiophora brassicae) on canola. Can. J. Plant Pathol. 36 (Suppl. 1): 99-112.
Peng G, Falk KC, Gugel RK, Franke C, Yu FQ, James B, Strelkov SE, Hwang SF and McGregor L. 2014. Sources of resistance to Plasmodiophora brassicae (clubroot) pathotypes virulent on canola. Can. J. Plant Pathol. 36: 89-99.
Chu M, Song T, Falk KC, Zhang X, Liu X, Chang A, Lahlali R, McGregor L, Gossen BD, Yu F, Peng G. 2015. Fine mapping of Rcr1 and analyses of its effect on transcriptome patterns during early infection by Plasmodiophora brassicae. BMC Genomics (Impact Factor: 4.041). 15:1166 (http://www.biomedcentral.com/1471-2164/15/1166).