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

Marker-Assisted Breeding for Fusarium Wilt Resistance in Canola

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

Project Code: CARP 2005-10

Final Report: June 2009

A fusarium-wilt infected field planted to a susceptible variety

near Viking.

Source: AITF

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.

Segregation 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.

In comparison, a resistant variety field located immediately

adjacent to the affected field near Viking.

Source: AITF

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