Location: Sunflower and Plant Biology Research
Project Number: 3060-21220-034-000-D
Project Type: In-House Appropriated
Start Date: Feb 1, 2022
End Date: Jan 31, 2027
Objective 1. Coordinate the development of a Sclerotinia initiative for expanded research to control this devastating disease which affects canola, sunflowers, soybeans, edible dry beans, lentils, peas and other crops. Research should be coordinated with interested ARS, state, and industry cooperators and administered through specific cooperative agreements. Planning workshops and annual meetings involving interested parties will be organized throughout the funding period. (NP 303, C3, PS 3A) Objective 2. Characterize resistance to Sclerotinia diseases in relevant crops, and support development of innovative diagnostic technologies, disease management systems, genomic resources, and crop germplasm exhibiting durable resistance to Sclerotinia sclerotiorum. (NP 303, C3, PS 3A) Subobjective 2A: Identify genetic loci contributing to basal stalk rot resistance by conducting a genome-wide association study (GWAS) of a cultivated sunflower diversity panel. Subobjective 2B: Determine the transcriptional responses to basal stalk rot infection in resistant and susceptible sunflower lines and compare changes in gene expression patterns to those observed in response to Sclerotinia infection for soybean, pea, canola, and sunflower head rot. Subobjective 2C: Evaluate experimental sunflower germplasm lines for resistance to Sclerotinia basal stalk rot and head rot to facilitate germplasm improvement.
Exotic and emerging plant diseases pose severe problems throughout the United States. Their increasing importance may be attributed to the introduction of pathogens into new geographic regions; modification of the environment that favor diseases; change in crop management practices; genetic shifts in the pathogen population; and other processes that may give them a competitive advantage. The fungus Sclerotinia sclerotiorum causes disease and economic loss on many important crop plants. S. sclerotiorum typically causes stem rotting on susceptible crop plants such as soybean, canola, dry edible bean, pea, and chickpea. However, this fungus causes two additional forms of disease on cultivated sunflower. Head rot occurs when fungal spores land on the sunflower head, causing destruction of the head and loss of seeds, while basal stalk rot occurs when fungal mycelia invade sunflower roots, causing root rot and wilting. Though S. sclerotiorum diseases of most crops can be managed by fungicide applications, fungicides are ineffective for control of sunflower head and basal stalk rots, leaving producers few options to combat Sclerotinia diseases. Improvement of host plant resistance to S. sclerotiorum is crucial to provide US sunflower growers with resistant hybrids to minimize economic losses. Resistance to S. sclerotiorum is quantitative, controlled by many genes contributing small effects to the overall level of resistance. This genetic complexity has hampered development of crop varieties with improved resistance. Consequently, this project aims to facilitate improvement of resistance to Sclerotinia diseases. Specific objectives are to: 1) map genetic loci underlying quantitative resistance to sunflower basal stalk rot; 2) understand transcriptional responses associated with basal stalk rot resistance; and 3) evaluate sunflower experimental germplasm for Sclerotinia resistance to facilitate germplasm enhancement. Completion of these objectives will provide new knowledge of genetic loci controlling resistance to Sclerotinia diseases of sunflower, information about transcriptional responses to Sclerotinia infection, and released germplasm resources to support breeding efforts. Additionally, comparative analyses of sunflower transcriptomic data with datasets from soybean, canola, and pea will improve our knowledge of common responses to infection by this pathogen. These resources will enhance the ability of plant breeders to improve resistance to Sclerotinia diseases in commercial crop varieties and hybrids.