Blackleg disease is a threat to canola production in Australia with an estimated 15% reduction in total grain yield annually. Control strategies include isolation of crops from disease sources, chemical control as well as varietal resistance. Major gene resistance (MGR) is a gene-for-gene interaction whereby one gene in the plant interacts with one gene in the blackleg pathogen. As the blackleg pathogen is capable of rapid and constant change, major gene resistance can be overcome in as few as three years, rendering the crop completely susceptible. Currently, all commercially available canola cultivars contain major genes but relatively few of these are effective.

Quantitative resistance (QR) comprises multiple genes with minor additive effects, and has proven more durable than MGR. In addition, the presence of QR can enhance the durability of MGR. However, it is difficult to breed for QR as it is comprised of numerous genes and is often masked by the presence of MGR. Consequently, QR is not widely present at effective levels in Australian commercial cultivars.

This program of research will identify how QR functions within the plant to reduce blackleg disease, determine conditions under which QR is reliably expressed, and develop methods to accurately quantify QR. This will form the basis to identify the genes underlying QR which will enable canola breeders to provide growers with canola varieties that have more durable QR and reduce blackleg-related yield loss.