Advancing blackleg and verticillium stripe management
The following nine summaries are for projects specific to blackleg and verticillium. The Government of Canada provided $3.3 million through the AgriScience Program (Canola Cluster) under the Canadian Agricultural Partnership, and growers contributed $1.8 million through SaskCanola and Alberta Canola. For full final reports for these nine projects, go to the Research section at saskcanola.com and look on the Canola Research Hub at canolaresearch.ca.
Toward a rating system for quantitative resistance to blackleg
Project title and principal investigators:
“Developing a robust system for efficient assessment of quantitative resistance (QR) in commercial canola varieties for blackleg management,” Gary Peng, Agriculture and Agri-Food Canada (AAFC) Saskatoon, and Debra McLaren, AAFC Brandon
Purpose:
To develop and validate a system to rate quantitative resistance (QR) against blackleg under both controlled environment and field conditions. QR or adult plant resistance is important to sustainable blackleg management in Canada. Blackleg resistance labelling is readily applicable for major-gene resistance but not yet possible for QR.
Results:
DNA analysis using droplet digital PCR (ddPCR) can identify strong QR in breeding lines for development of canola hybrids with good QR background against blackleg. It could be a new tool for blackleg resistance breeding, and a new standard for labelling the QR trait of canola cultivars against blackleg.
Project title and principal investigators:
“Developing tools for the rapid screening of canola germplasm for quantitative resistance to disease,” Hossein Borhan, AAFC Saskatoon, and Ralph Lange, InnoTech Alberta
Purpose:
To optimize a protocol for identifying quantitative resistance (QR) to blackleg disease under controlled conditions (growth chamber) and validate the result under field conditions. A rapid screening method using a genome-wide association mapping approach will provide the canola industry with a valuable tool for developing new varieties.
Results:
Researchers developed a protocol for growth chamber and greenhouse-based QR assay. It can be used for high-throughput screening to identify canola varieties with quantitative resistance to blackleg disease.
The critical infection window for blackleg
Project title and principal investigator:
“Understanding the critical infection window that causes blackleg of canola in Western Canada,” Gary Peng, AAFC Saskatoon
Purpose:
To determine the relative importance of cotyledon versus lower true-leaf infection as they relate to blackleg severity on canola varieties with different levels of resistance. 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.
Results:
The fungus Leptosphaeria maculans can cause blackleg more successfully via wounds on cotyledons than on lower true leaves. Cotyledon infection results 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 and 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 suggests an opportunity to use seed treatment to manage blackleg. Fluopyram and pydiflumetofen are promising seed treatments.
Project title and principal investigator:
“Fine-tuning of the blackleg yield loss model in canola,” Sheau-Fang Hwang, University of Alberta
Purpose:
To build on the earlier work on Westar by modeling yield losses from blackleg in modern canola hybrids, making the model more accurate and more relevant to producers and agronomists.
Results:
Researchers developed the blackleg yield loss calculator. Find it at canolacalculator.ca.
Flea beetles and blackleg
Project title and principal investigator:
“Improving management of blackleg on canola via better flea beetle control and effective fungicide seed treatment in Western Canada,” Gary Peng, AAFC Saskatoon
Purpose:
To understand the relevance of flea beetle feeding to blackleg.
Results:
This study provided strong evidence that wounds on cotyledons or lower leaves allow blackleg pathogen infection without the presence of leaf surface wetness. However, data from field trials failed to prove that controlling flea beetles with a foliar insecticide may help reduce blackleg infection. 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 strongly indicate that applying foliar insecticide targeting flea beetles will unlikely help reduce blackleg infection in Western Canada.
Blackleg R-gene rotation
Project title and principal investigator:
“Improving blackleg resistance durability through R-gene rotation in commercial fields on the Canadian Prairies,” Dilantha Fernando, University of Manitoba
Purpose:
To help fine-tune the sequence of blackleg R genes to be deployed in rotation for maximum resistance durability.
Results:
Canola cultivars rotated with 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.
Project title and principal investigators:
“Genetic dissection of the Rlm3-4-7-9 blackleg R-gene cluster and KASP marker improvement,” Hossein Borhan, AAFC Saskatoon
Purpose:
To provide an in-depth understanding of R genes in the Rlm3-4-7-9 cluster, which is very important for the genetic improvement of canola against blackleg. This project will improve the efficiency of molecular markers so that growers can detect the blackleg races in their fields and make informed varietal selections.
Results:
Cloning and knowledge of the23 sequence of these genes has facilitated the design of gene-specific allele markers for genotyping and breeding. It has advanced the understanding of their function and interaction with the corresponding L. maculans Avr genes.
Verticillium and blackleg
Project title and principal investigator:
“Verticillium disease etiology and nursery,” Dilantha Fernando, University of Manitoba
Purpose:
To address the major research priorities needed to understand and manage verticillium stripe in Western Canada. Questions to answer include: 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, the pathogen that causes verticillium stripe, and L. maculans, the pathogen that causes blackleg?
Results:
Researchers identified three different V. longisporum lineages in Saskatchewan, and lineage A1/D1 is considered the most virulent. Researchers found 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.
Project title and principal investigator:
“Genetics and genomics of brassica-verticillium interaction,” Hossein Borhan, AAFC Saskatoon
Purpose:
To develop tools for genotyping and monitoring changes in Verticillium longisporum. 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.
Results:
Researchers identified two B. napus disease resistance QTLs on chromosomes A07 and C02 that are effective against V. longisporum. They developed three markers that can distinguish V. longisporum from other verticillium species. They also identified B. napus lines with resistant, intermediate, and susceptible responses to V. Longisporum. These could serve as checks in V. longisporum nurseries. Researchers potentially found a microorganism that can protect against V. longisporum.