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United States Department of Agriculture

Agricultural Research Service

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Research Project: Synergistic Enhancement of Resistance to Sclerotinia Sclerotiorum

Location: Sunflower and Plant Biology Research

Project Number: 3060-21220-031-03-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jul 1, 2013
End Date: Sep 30, 2017

The overall goal of this project is to develop effective and durable disease resistance for Sclerotinia stem rot of canola/rapeseed (Brassica napus) through transgenic and/or cisgenic engineering of the host. This goal is being pursued with a three-year strategy that builds on preliminary data where we have identified two genes, one from a host plant and another from the pathogen, that hold the potential to block disease when over-expressed in canola. The first of these is the HSS1 gene that we have mapped in Arabidopsis thaliana as a locus conferring extreme susceptibility to Sclerotinia infection when it is mutated to loss of function. The second is the oxalate decarboxylase gene (ODC2) gene from the pathogen that functions in the enzymatic breakdown of oxalate, a major virulence factor. In the first two years of funding we have successfully finemapped the A. thaliana HSS1 gene that functions in basal resistance against S. sclerotiorum, identified the specific mutation conferring the hss1 phenotype, overexpressed the HSS1 gene in Arabidopsis, and identified a B. napus ortholog of HSS1 (BnHss1). Regarding the ODC2 gene, we have functionally characterized ODC2 and confirmed its oxalate degrading enzymatic activity and overexpressed ODC2 in Arabidopsis.

Our approach to accomplish the overall project goals is being carried out over the course of three years. Thus far in the first two years we have completed the fine-scale genetic mapping of the hss1 mutation, verified the function of the HSS1 gene in Arabidopsis and developed plants that over-express the HSS1 and ODC2 genes. The goals for year three are to assay disease resistance in HSS1/ODC2 Arabidopsis transgenic lines, to test the function of BnHSS1, and to engineer resistance in canola using HSS1 and ODC2. This project has direct relevance to the goals and priority research needs of the Sclerotinia Initiative. The proposed studies will make significant contributions towards understanding the genetics of host resistance and directly improving crop germplasm for Sclerotinia resistance. Although the first and second year objectives have been concerned primarily with the non-crop plant A. thaliana; this has been integral to our success in mapping the HSS1 locus and our overall project goal of producing resistant canola lines. We are beginning now to evaluate HSS1/ODC2-expressing lines for disease resistance phenotypes. In the current funding request for year three, we propose to identify the functional BnHSS1 gene and verify its activity by complementation of the Arabidopsis hss1 mutant. Meanwhile, we will generate B. napus lines overexpressing HSS1 and ODC2. We have chosen to initially focus on canola as it is a crucifer with a close relationship to A. thaliana and also due to our experience with 3 transgenic manipulation of canola. In the long term, we anticipate that the results produced here will be applicable to increasing resistance in other susceptible crops including soybean, dry bean, sunflower and pulse crops.

Last Modified: 10/19/2017
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