Blight Future - PulseResearch
April 25, 2017
Research takes us one step closer to controlling ascochyta blight in chickpeas
Ascochyta blight in chickpea continues to be a serious problem worldwide for a number of reasons. Not only is there a lack of sources of resistance to the disease, but there is limited genetic variation in chickpea material currently used for plant breeding. That means that only small improvements can be expected in the fight against ascochyta blight.
One Saskatoon researcher expects to improve the odds. Dr. Lone Buchwaldt, a Research Scientist with Agriculture and Agri- Food Canada’s (AAFC) Saskatoon Research Centre, has done extensive research in the area of ascochyta blight in chickpeas and just completed her most recent research project, funded by Saskatchewan Pulse Growers (SPG), on the issue earlier this year. In order to suggest better ways to control the disease, she set out to identify and understand the type of resistance to ascochyta blight through genetic markers in the chickpea genome.
“The first linkage map of molecular markers in chickpeas was developed by a group in Germany in 1999 and was based on simple sequence repeats (SSR), serving as a reference map for many years,” Dr. Buchwaldt says. “More SSR markers were gradually added by other scientists, but the SSR map remained sparse. At AAFC we began development of another marker system based on single nucleotide polymorphisms, or SNPs. Since then, scientists have developed more than a thousand SNP markers and produced a dense linkage map of these markers, many of which were designed in actual genes with known functions including different defense mechanisms against pathogens.”
This breakthrough helped Dr. Buchwaldt and other researchers at AAFC to identify specific genes associated with ascochyta resistance, partly because they were able to exchange both published and unpublished data with other scientists outside Canada, and partly because they had a leaf assay from which they could accurately determine the interaction of specific chickpea lines with different pathotypes of the Ascochyta rabiei pathogen.
“The most significant outcome of this research was the discovery of the presence of receptors in chickpea host cells that are able to recognize different pathotypes of the pathogen, which trigger different defense mechanisms,” Dr. Buchwaldt says. “The classic outcome in most host-pathogen recognition systems is a high level of resistance. However, in the chickpea-ascochyta system, the resistance is often intermediary, and that has confused the interpretation of results in the past.”
In another part of their research, the research team at AAFC chose chickpea germplasm that had not been looked at by other scientists for screening against the ascochyta blight pathogen, Ascochyta rabiei. They were able to identify new sources of resistance in chickpea accessions from 15 countries, information that will help expand the repertoire of resistance available for plant breeding. “We were fortunate to identify several chickpea lines from countries not previously known as sources of ascochyta resistance,” Dr. Buchwaldt says.
Dr. Buchwaldt also built on previous research done by scientists from other chickpea-growing areas of the world such as India, Syria, Spain, Germany, Canada, Australia, and the United States. Her group was able to consolidate information about the location of ascochyta resistance loci in the chickpea genome using 10 of their own chickpea mapping populations in combination with 16 populations from the literature. This approach allowed the group at AAFC to consolidate information into 13 loci, conferring ascochyta resistance found in chickpea lines already known to the research community.
In Buchwaldt’s research over the years, she has come across a few chickpea lines that have low-level resistance against several ascochyta blight pathotypes and other lines with a high level of resistance to some pathotypes, but not all. “I think it would be prudent to combine the general and the specific types of resistance into adapted varieties by traditional crossing and selection,” she says. “In addition, varieties with different sources of resistance should be rotated to reduce the likelihood that resistance is overcome by changes in the pathogen population. This approach could, in the long term, provide growers with more durable disease resistance.”
Additional research will be required to capitalize on the possibilities for new varieties and to extend the scope of this research. For now, these results mean we are one step closer to controlling the disease. They also mean we are one step closer to chickpea breeders having the capability to include the new chickpea lines with ascochyta resistance identified in this project by crossing into adapted varieties. “This would give growers the opportunity to select new varieties with a higher level of ascochyta resistance,” Dr. Buchwaldt says.
SPG Investment: $186,000
Co-Funders: Agriculture and Agri-Food Canada - Canadian Crop Genomic Initiatives - $135,000
Project Lead: Dr. Lone Buchwaldt, Research Scientist, Agriculture and Agri-Food Canada, Saskatoon Research Centre