The Challenge

Blackleg severity is increasing, again. The recommendation is to change cultivars in the field if the infection is affecting yield in hopes to rotate resistance genes. Unfortunately, this may be ineffective in practice since the similar resistance packages may inadvertently be presented to the pathogen through different cultivars (resistance packages are either unknown or proprietary), as well as avr genes are constantly shifting.

The Project

After inoculation and evaluation, place canola cultivars into resistance groups based on the type of blackleg resistant gene(s) they carry.

The Results

Some varieties responded differently to the same populations when inoculated at seedling stage versus 3-leaf stage, suggesting that major resistant genes are not the only genes determining cultivar resistant to blackleg. Since only about 6% of the commercial cultivars tested could simultaneously resist two of the common L.maculans strains, quantitative resistant genes are thought to be contributing to overall resistance to blackleg. Therefore, labelling individual genes would be more productive for the canola industry than resistance groups/packages.

Grower Benefits

A better understanding of major and quantitative resistance genes in blackleg was developed, but so was the realization that blackleg is not a simple pathogen. Further research will be done to develop a method for gene-specific labelling on commercially available cultivars for improved blackleg management.

Keywords: Blackleg, Quantitative resistance, R genes, Resistance breakdown, Leptosphaeria maculans, L. maculans, Major gene resistance