Lange: Marker-Assisted Breeding for Fusarium Wilt Resistance in Canola

Date: June 2009
Term: 2 years
Status: Completed
Researcher(s): Mr. Ralph Lange, Alberta Research Council, Vegreville, AB, S. Kuzmiez, Agriculture and Agri-Food Canada, Saskatoon, SK, S. Rimmer, Agriculture and Agri-Food Canada, Saskatoon, SK
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a

Project Summary

Fusarium wilt resistance in Brassica napus was found to be conferred by a single dominant gene, the A-genome. This means that B. rapa and B. oleracea may be sources of resistance to fusarium wilt available to B. napus breeders. Combining resistances could be used to increase the longevity of resistance to Fusarium wilt in B. napus.

Fusarium wilt (FW) of canola, caused by the pathogen Fusarium oxysporum, results in severe yield losses of canola. However, yield losses due to FW can be eliminated through the use of resistant cultivars. Genetic resistance is the most cost-effective and probably the only effective method of controlling FW. Plant breeders could theoretically eliminate susceptible genotypes from their current and future simply by screening out susceptibility to FW early in crossing programs.

In comparisons of susceptible and resistant Brassica napus genotypes in field trials at nine locations in western Canada, the mean yield of the least-affected cultivar was 16 % higher than the most severely affected cultivar. Yield improvement due to disease resistance increased to 75% when the least and most severely affected cultivars were compared at the site with the greatest disease pressure. FW-susceptible cultivars or breeding lines can be identified using growth chamber and field screening techniques. Use of these techniques has allowed plant breeders to identify susceptible germplasm in breeding programs.

Genetic markers can be used to differentiate plants that carry a desired trait (such as FW resistance) from those that do not. Resistance to FW has not been associated to molecular markers in B. napus, although this has been done for vascular FW of other crop species. Knowledge of the mode of inheritance would improve the ability of plant breeders to manipulate the FW-resistance trait. Ideally, FW resistance would be linked to DNA-based genetic markers. Marker-assisted selection would allow breeders to directly infer the genotype of very young plants, and avoid time delays caused by phenotype testing, and simultaneously avoid confounding effects of genotype x environment interactions.

The objectives of this project were to identify and characterize the mode of inheritance of the FW-resistant phenotype in B. napus, to determine the number of genes associated with resistance and to identify microsatellite markers that are linked with those genes. Phenotype tests of the parental genotypes confirmed that SP Banner and DH12075 were resistant, and Canterra 1604 was susceptible to FW, confirming that subsequently-derived mapping populations were the progeny of crosses between resistant and susceptible plants.

In comparison, a resistant variety field located immediately adjacent to the affected field near Viking.

Source: AITFSegregation between F3 lines from reciprocal matings fit 3:1 (Resistant:susceptible) segregation ratios individually and when combined, suggesting that resistance in B. napus cv. DH12075 is controlled by a single dominant gene for resistance to FW. Assessment of the A-genome indicated that microsatellite markers sR0404 and sR9448 were associated with the resistant phenotype. On this basis, FW-resistance in B. napus was associated with a single locus mapping to A-3 linkage group. Genetic analysis of FW resistance in B. napus has not been conducted previously, but resistance has been associated with B. rapa, which is ancestral to B. napus. Resistance to F. oxysporum has been characterized in B. oleracea, the other B. napus ancestor, suggesting that additional, as-yet unidentified resistance to FW may be available on the B. napus C-genome. This means that multiple sources of resistance may be available to canola breeders, either within B. napus or via interspecific crosses between B. oleracea and B. rapa. Combining resistances could be used to increase the longevity of resistance to FW.

The results of this study will allow member-organizations of the Microsatellite Marker Consortium to screen accessions for resistance/susceptibility to FW. The consortium includes most of the oilseed Brassica napus breeding organizations active in the North American marketplace. Currently, breeding organizations either screen selections in naturally-infested field nurseries, or test for resistance in controlled environment tests. Use of the markers would allow these organizations to screen large numbers of accessions, and also avoid much of the field or controlled environment screening phenotype testing that is currently necessary.

Scientific Publications

Lange, R.; Rimmer, S. R.; Lydiate, D.; Kuzmicz, S.; Goßmann, M. ; Büttner, C. 2010.

Linkage of Resistance to Fusarium Wilt (Fusarium oxysporum) in Spring Rapeseed (Brassica napus) with Microsatellite Markers. 57. Deutsche Pflanzenschutztagung, Berlin, Germany, September 6 – 9, 2010

Full Report PDF: Marker-Assisted Breeding for Fusarium Wilt Resistance in Canola