Identifying novel genetic factors contributing to durable disease resistance in canola
Term: 4 years, beginning in 2023
Status: Ongoing
Researcher(s): Isobel Parkin, Agriculture and Agri-Food Canada
SaskCanola Investment: $153,650
Total Project Cost: $454,700
Funding Partners: TBC
Objectives
Determine epialleles contributing to adaptation to Prairie conditions.
Assess the role of DNA methylation (epigenetics) in quantitative resistance to blackleg and clubroot in canola.
Project Description
As with many crops, canola faces increasing challenges due to unpredictable environmental changes, notably last year drought conditions were prevalent, while in 2022 high heat stress during flowering and pod filling is likely to cause yield losses. In addition, there are continuous cycles of varying disease pressure. Developing crops with sustainable resistance to abiotic and biotic stress is imperative to ensure the long-term productivity of agriculture on the Prairies. Canola has a narrow genetic base, thus identifying new sources of heritable positive alleles for traits of interest is important and requires innovative approaches. The proposed project will assess and capture new variation created through manipulating methylation in the crop; it is becoming increasingly apparent that this is an undervalued source of variation, in particular for controlling disease resistance. As such the project will contribute to the continued development of improved canola germplasm for Prairie producers.
Blackleg incidence has resulted in the reduced value of some of the deployed resistance genes (R genes) in canola cultivars; most notably Rlm3 which was found commonly in Canadian canola cultivars. Additionally, the clubroot pathogen population is extremely diverse and appears to be adapting quickly in Western Canada and is already responsible for the breakdown of resistance. Although it is recognized that genetic resistance is the most reliable mechanism of mitigating the impact of plant pathogens, plant breeders and plant pathologists are faced with the problem of how best to construct cultivars with the highest resistance possible and how to deploy resistant cultivars in space and time to maximize durability.
Resistance durability is required to prevent devastating ‘boom and bust’ cycles where pathogen populations respond to selection exerted by resistant plant hosts, carrying single major resistance genes. It has been shown that the introduction of R genes into cultivars with high levels of quantitative resistance increases the long-term durability of the resistance by enhancing disease control through the effective pyramiding of resistance sources; by limiting selection of virulent isolates, since quantitative resistance slows down the rate of epidemic development; and can potentially maintain a level of protection when the R gene is finally overcome. Quantitative resistance to blackleg has been identified in a number of canola cultivars, which could be exploited for long-term yield stability, but significant effort is required to combine this polygenic resistance with an effective major gene resistance in new cultivars. Similarly, although there has been limited research into quantitative resistance for clubroot in B. napus, it would be expected that a pan-genome response to clubroot infection in combination with R gene deployment would lead to a more sustainable and durable long-term resistance. Global methylation repatterning is a mechanism by which plants can generate a heritable quantitative response to pathogen attack. However, the exact role of methylation in the qualitative and quantitative disease response of B. napus is unclear. We are proposing a unique approach to identify genetic factors that potentiate the disease response in canola, an approach that could also prove effective in other Prairie crops. Recursive selection on epigenetic features for energy use efficiency showed higher yield potential and inheritance of acquired methylation patterns and agronomic characteristics. These observations provide strong evidence that induced epigenetic variation can be exploited effectively for selection in crop improvement. We are proposing that global methylation re-patterning, specifically through the application of a unique demethylation mutant developed at AAFC, could be exploited to enhance the basal resistance of B. napus to both blackleg and clubroot. Further, heritable novel epialleles determined to increase the efficacy of known R genes could be identified.