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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 Research

Project Number: 3060-21220-028-24
Project Type: Specific Cooperative Agreement

Start Date: Jul 01, 2013
End Date: Sep 30, 2015

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 will be pursued in 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 overexpressed 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 (ODC1) gene from the pathogen that functions in the enzymatic breakdown of oxalate, a major virulence factor. The Specific Objectives outlined in this proposal for the project’s first year are to: (1) Isolate the newly mapped A. thaliana HSS1 gene that functions in resistance to S. sclerotiorum and identify the B. napus homolog; (2) Develop resistant lines of A. thaliana by over-expressing the HSS1 gene; (3) Develop resistant lines of A. thaliana by over-expression of the S. sclerotiorum ODC1 gene.

Our approach to accomplish the project goals will be carried out over the course of three years. In the first year we will complete fine-scale genetic mapping and isolation of the HSS1 gene from A. thaliana. This gene will be cloned in a plant expression vector, over-expressed in A. thaliana, and evaluated for conferring Sclerotinia disease resistance. Simultaneously, we will clone and characterize the oxalate decarboxylase gene from S. sclerotiorum, over-express it in A. thaliana, and evaluate transgenic lines for disease resistance. Additionally, using available genome sequence resources, we will isolate a corresponding HSS1 gene homolog from B. napus to be used in year two and three for engineering resistance in canola. 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 year objectives are concerned primarily with the non-crop plant A. thaliana, this is an integral component of the overall project goals to produce resistant canola lines. The use of the A. thaliana model plant in the first year is required for initial gene isolation and will allow us to make more rapid initial experimental progress than possible using the crop plant. Application to crop plants will however begin in this first year through the identification of a B. napus HSS1 homolog. 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 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: 7/28/2015
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