Canola AgriScience Cluster Theme 7: Maintaining Canola Supply and Trade - Blackleg and Verticillium
Term: 5 years, beginning in 2019
Status: Ongoing
SaskCanola Investment: $1,576,280
Total Project Cost: $5,034,246
Funding Partners: ACPC and AAFC Canadian Agricultural Partnership
Administered By: Canola Council of Canada
Project Descriptions
1. Developing a Robust System for Efficient Assessment of Quantitative Resistance (QR) in Commercial Canola Varieties for Blackleg Management
Researchers: Gary Peng and Debra McLaren (AAFC)
Purpose: Blackleg is a serious threat to canola production in Western Canada and is a trade issue with seed exports to China. This disease has been managed primarily through variety resistance, including major-gene and quantitative resistance (QR), as well as extended crop rotations. QR or race-nonspecific resistance is important to sustainable blackleg management in Canada. QR plays an important role in blackleg resistance on the prairies where the industry is moving to blackleg resistance labelling for more effective utilization of genetic resources; this approach is readily applicable for major-gene resistance but not yet possible for QR because the current labeling system (R/MR/MS/S) is unable to identify QR specifically or quantitatively; this rating includes both QR and major-gene resistance. There is also the need for a reliable protocol to improve field QR assessment. The objective of this research is to develop and validate a system for efficient quantification of QR against blackleg under both controlled environment and field conditions.
Grower Benefits:
This study provides strong evidence that the Leptosphaeria maculans (Lm) growth kinetics in canola tissues is closely related to the level of quantitative resistance (QR) to blackleg, and the former can be quantified efficiently with ddPCR.
This technology can be used to identify strong QR in breeding lines for development of canola hybrids with good QR background against blackleg and can potentially be a new tool for blackleg resistance breeding, as well as a new standard for labelling the QR trait of canola cultivars against blackleg.
Several major life-science companies have provided commercial hybrids for further testing of QR using the ddPCR protocol and at this stage, the technology is best suited for breeding industry to identify and select optimal QR background for blackleg resistance breeding.
Other References to this Research Project
2021 Video Presentation by Gary Peng: Using ddPCR as a Novel Screening Tool to Identify Quantitative Resistance to Blackleg of Canola
Video: CAP Wrap-Up Event - Afternoon Session starts at 1:45:00
2. Developing Tools for the Rapid Screening of Canola Germplasm for Quantitative Resistance to Disease
Researchers: Hossein Borhan (AAFC); Ralph Lange (InnoTech Alberta)
Purpose: Fungicides have little effect in controlling blackleg and the best practice is using canola cultivars with genetic resistance. Quantitative resistance (QR), also called adult plant resistance (APR), is the most favourable form of genetic resistance since it is controlled by several genes, therefore more durable. Despite its importance, it is very challenging to identify and introduce APR into canola cultivars using conventional field based assay. The goal of this research is to optimize a protocol for identifying APR to blackleg disease under controlled condition (growth chamber) and validate the result under field conditions. A rapid screening method with genome-wide association mapping approach will provide the canola industry with a valuable tool for developing new varieties.
Grower Benefits:
A protocol for growth chamber and greenhouse-based APR assay using single and mixed isolates applied at the seedling stage (as occurs under natural condition) was developed and can be used for high-throughput screening to identify canola varieties with quantitative resistance to blackleg disease.
A major QTL on chromosome A08 of B. napus was identified for blackleg resistance.
Other References to this Research Project
2021 Video Presentation by Hossein Borhan: Tools for Rapid Identification and Integration of R and QTL Genes Against Blackleg Disease
3. Understanding the Critical Infection Window that Causes Blackleg of Canola in Western Canada
Researcher: Gary Peng (AAFC)
Purpose: This study will help determine the relative importance of cotyledon vs. lower true-leaf infection to stem infection (the critical infection window) and blackleg on canola varieties with different levels of resistance. This information is important to developing inoculation protocols for improved QR assessment/labelling in field trials. Additionally, the results of the critical infection window will determine the optimal timing of fungicide applications, either as seed treatment or as a foliar spray at later stages. This research will improve our understanding of the infection pathway for blackleg and provide valuable information for reducing blackleg in the field.
Grower Benefits:
The fungus Leptosphaeria maculans can cause blackleg more successfully via wounds on cotyledons than on lower true leaves resulting in higher disease incidence and severity at canola maturity. Researchers also found that QR, without the direct involvement of major R genes, can reduce infection spread from inoculated cotyledons/lower true leaves to the stem, with substantially reduced levels of blackleg relative to susceptible canola. This demonstrates the value of using QR for the management of blackleg in western Canada.
The importance of cotyledon infection to blackleg highlights an opportunity for using seed treatment to manage blackleg. Fluopyram and pydiflumetofen (both are succinate dehydrogenase inhibitors- SDHI) have been evaluated as a seed treatment option and results are promising for control of cotyledon infection by L. maculans. Both treatments have been registered in Canada recently and extensive field trials are being carried out on the prairies for efficacy assessment and confirmation before the product launch.
Other References to this Research Project
4. Fine-Tuning of the Blackleg Yield Loss Model in Canola
Researchers: Sheau-Fang Hwang and Stephen Strelkov (University of Alberta); Henry Klein-Gebbinck and Gary Peng (AAFC)
Purpose: Blackleg, caused by the fungus Leptosphaeria maculans, is an important disease of canola. In order to better assess the economic impact of blackleg and to help make appropriate disease management decisions, it is important to be able to relate blackleg severity with corresponding yield losses. A preliminary yield loss model was generated that related blackleg severity to yield loss under field conditions in Alberta. While serving as a solid foundation to understand blackleg associated yield losses in Western Canada, the earlier model was based largely on data obtained with the susceptible canola ‘Westar’. Since this is an old, open pollinated, herbicide non-tolerant cultivar, the results may have been confounded by the presence of weeds, canola volunteers and/or other diseases. The current project aims to build on the earlier work by modeling yield losses from blackleg in modern canola hybrids, making the model more accurate and more relevant to producers and agronomists. An improved model may also provide important information to the canola industry allowing accurate estimates of yield losses on a local or even regional scale.
Grower Benefits:
This project builds on previous work, by modelling yield losses from blackleg in modern canola hybrids, making the model more accurate and more relevant to producers and agronomists. The blackleg yield loss calculator can be found at: Blackleg Loss Calculator | Canola Calculator (canolacouncil.org).
5. Improving Management of Blackleg on Canola via Better Flea Beetle Control and Effective Fungicide Seed Treatment in Western Canada
Researchers: Gary Peng and Debra McLaren (AAFC); Dilantha Fernando (University of Manitoba)
Purpose: From both a sustainable canola production and marketing perspective, it is important to manage blackleg in canola. While variety resistance is the cornerstone for blackleg management, an integrated approach, including crop rotation and chemical control, is important for continued reduction of blackleg in the field. This project will generate new information that can help improve or even revolutionize blackleg control in Western Canada by understanding the relevance of flea beetle feeding to blackleg and validating the efficacy of a novel cost-effective fungicide seed treatment to block the early infection via the feeding wounds. This research will have positive impact on our industry by addressing the risk of blackleg on both production and marketing fronts; lowered blackleg incidence/severity may have reduced inoculum load on seed and dockage.
Grower Benefits:
This study provided strong evidence that wounds on cotyledons or lower leaves allow the infection by the blackleg pathogen Leptosphaeria maculans on canola seedlings without the presence of leaf surface wetness. This seems to support the notion that wounding of canola seedlings would contribute to blackleg in western Canada where weather tends to be cool and dry, and flea beetle feeding is common in spring.
It might be thought that controlling flea beetles with a foliar insecticide may help reduce blackleg infection, but the data from field trials failed to prove that. It appears that when inoculum is abundant, like in continuous canola used in this study, differences in wounding severity would have no significant effect on the success of blackleg infection. Results from this study strongly indicate that applying foliar insecticide targeting flea beetles will unlikely help reduce blackleg infection in western Canada.
Using a resistant cultivar, based only on the quantitative resistance background, provided the most consistent control of blackleg and yield benefit to canola.
Other References to this Research Project
6. Improving Blackleg Resistance Durability Through R-gene Rotation in Commercial Fields on the Canadian Prairies – A Science-Based Stewardship Program
Researchers: Dilantha Fernando (University of Manitoba); Gary Peng (AAFC); Ralph Lange (InnoTech Alberta)
Purpose: The main reason for the increase in blackleg is the breakdown of resistance (R-genes) by new races of the blackleg pathogen on canola varieties grown across the prairies. One of the methods that may mitigate the risk of rapid resistance erosion is to introduce an R-gene rotation regime where the pathogen population will not be able to adapt to any single R gene easily. This has been a successful strategy used in Australia and France. The WCC/RRC has passed a resolution in February 2017 to introduce this strategy in Canada, and the Canola Council of Canada also supports this approach. The effectiveness of this approach needs to be studied in Canada. The information will help fine tune the sequence of R genes to be deployed in rotation for maximum resistance durability. This study will provide growers with the information needed to utilize the major blackleg resistance genes currently available in canola cultivars. The information will aid in developing best management practices for extending the durability of major genes and contribute to decreasing the incidence of blackleg in Canadian canola production and the potential threat to key export markets.
Grower Benefits:
Based on four years’ data, we indicated that the canola varieties rotated with the new R genes showed good performance in reducing the disease incidence and severity. Rlm4 only or Rlm4 in combination with other R-genes showed lower disease severity and incidence.
Rotating canola varieties with different single novel R genes can decrease blackleg severity and incidence. It was also observed that stacked R genes with different combinations can decrease or increase the disease incidence and severity depending on the R genes in investigation.
Other References to this Research Project
7. Genetic Dissection of the Rlm3-4-7-9 Blackleg R Gene Cluster and KASP Marker Improvement
Researchers: Hossein Borhan and Isobel Parkin (AAFC); Nicholas Larkan (Armatus Genetics Inc.); Ralph Lange (InnoTech Alberta)
Purpose: The Rlm3-4-7-9 cluster is very important for the genetic improvement of canola against blackleg. The proposed research will resolve the nature of these genes by conducting fine mapping and cloning. Revealing the structure of the Rlm3-4-7-9 cluster will help with understanding the complex interaction and may allow new R genes to be developed with multiple Avr recognition properties. This pre-commercial work will provide an in-depth understanding of these R-genes, potentially leading to improved major gene resistance and a corresponding decrease in blackleg incidence. In addition, this project will improve the efficiency of molecular makers so that growers can detect the blackleg races in their fields and make informed varietal selections. This will contribute to decreasing the incidence of blackleg in Canadian canola production to address potential threats to our key export markets.
Grower Benefits:
Researchers were able to clone the Rlm3, Rlm4, Rlm7 and Rlm9 genes. Cloning of the Rlm3 genes revealed that the genes are allelic and belong to the recently discovered class of R genes that encode wall associated kinase like (WAKL) proteins.
Cloning and knowledge of the sequence of these genes has facilitated the design of gene-specific allele markers for genotyping and breeding and has advanced the understanding of their function and interaction with the corresponding L. maculans Avr genes.
Other References to this Research Project
8. Verticillium Disease Etiology and Nursery
Researchers: Dilantha Fernando and Mario Tenuta (University of Manitoba); Sheau-Fang Hwang and Stephen Strelkov (University of Alberta); Maria del Mar Jimenez-Gasco (Penn State University)
Purpose: Verticillium stripe, caused by the fungus Verticillium longisporum, was first found in canola in Canada in 2014. Very little is known about this disease in Canada but studies in Europe have shown it to cause significant yield loss in both spring and winter types of Brassica napus. This research is an integrated and collaborative approach to addressing the major research priorities needed to understand and manage the disease in Western Canada. A series of projects will address major questions that need to be answered about this disease, namely: How to improve the identification of this disease? Can the pathogen be rapidly quantified in the soil? How does the pathogen behave in Western Canada? What is the genetic diversity of the pathogen? What is the relationship and interaction between V. longisporum and L. maculans? Fundamental to the success of this activity is the establishment of a test field or nursery. The nursery will provide support for activities including soil and plant materials for method development, longevity of the pathogen, screening of canola lines, disease development and yield effects and outreach to growers and industry. Understanding the biology of the pathogen and how it behaves in Western Canada will provide valuable information for producers, agronomists, and researchers that overall will help reduce potential disease impact.
Grower Benefits:
Researchers were able to identify three different V. longisporum lineages in Saskatchewan. Out of the six samples collected, three were confirmed as A1/D1, A1/D2 and A1/D3 and three as V. dahliae. Verticillium dahliae infects a wide range of mainly non-cruciferous hosts.
Verticillium longisporum lineage A1/D1 is considered the most virulent group across Brassicaceae crops, especially canola, followed by A1/D3 and A1/D2. Knowing the parental lineages can indicate if canola may be severely affected.
Researchers studied the interaction between V. longisporum and L. maculans, looked at symptoms of disease infection and scored them for severity. There was a significant interaction between V. longisporum and L. maculans on blackleg scores but not verticillium stripe scores. When researchers looked at seed yield, the main effect of both pathogens individually reduced seed yield, but they noted no significant interaction between V. longisporum and L. maculans so there was not a significant additive effect on decreased seed yield.
Other References to this Research Project
2022 Video: Verticillium Stripe in Canola - Lifecycle and Disease Severity
Podcast: Ep. 80 - Verticillium stripe - November 30, 2022 by Canola Watch
Video: CAP Wrap-Up Event - Afternoon Session starts at 2:01:55
9. Genetics and Genomics of Brassica-Verticillium Interaction
Researchers: Hossein Borhan, Isobel Parkin and Christina Eynck (AAFC); Nicholas Larkan (Armatus Genetics, Inc.); Ralph Lange (InnoTech Alberta); Stephen Strelkov and Sheau-Fang Hwang (University of Alberta); Rudolph Fredua-Agyeman (Alberta Agriculture and Forestry)
Purpose: Verticillium stripe is an emerging soil-borne disease of canola in Canada requiring a multi-faceted research initiative to mitigate the potential risks posed by this pathogen. Examples of risk to canola production are yield loss, restriction of canola exports and reduction of farmland value when the pathogen becomes established in the soil. Resistant cultivars have proven to be the most cost-effective and environmentally sound approach for managing biotic stress. The two main requirements for genetically-based disease management is knowledge of pathogen virulence and plant resistance genes. The proposed research aims at developing tools for genotyping and monitoring changes in the pathogen, Verticillium longisporum, understanding the genomics of pathogen virulence and the genetics/genomics of canola defense. This research will provide an understanding of Verticillium stripe resistance with output of genetic markers for resistance as well as insight into the infection process. This information is a vital first step in providing tools for managing the disease in the future.
Grower Benefits:
Researchers were able to make valuable advances in understanding the genetics of Verticillium stripe by identifying two B. napus disease resistance QTLs on chromosomes A07 and C02 that are effective against V. longisporum. They also developed three KASP markers that can distinguish V. longisporum from other Verticillium species. There were also B. napus lines identified with resistant, intermediate, and susceptible responses to V. longisporum, and these could serve as checks in the V. longisporum nurseries.
One unexpected finding from this project is that in preliminary tests, the researchers potentially found an endophyte that can protect against V. longisporum.