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United States Department of Agriculture

Agricultural Research Service

2011 Annual Report

1a.Objectives (from AD-416)
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.

1b.Approach (from AD-416)
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.

3.Progress Report
Milestones listed in question 2 comprise the National Sclerotinia Initiative Strategic Plan. Each milestone was addressed in FY2011 by components of the 32 specific cooperative agreements and ARS projects funded from the Initiative. Research is ongoing in all areas and substantial progress has been made in Epidemiology and Disease Management and Variety Development & Germplasm Enhancement. Pathogen and Host Genomics research resulted in significant progress, but substantial efforts are still needed in genome sequencing of the pathogen and gene profiling of susceptible and resistant crops. Pathogen Biology and Development research is ongoing, but additional efforts are needed to identify disease infection processes and to characterize virulence among disease genotypes.

1. Improving white mold resistance in U.S. crops. The National Sclerotinia Initiative (NSI) employs an integrated and collaborative approach to guide research on the effective development of diagnostic technologies, disease management systems, genomic resources, and crop germplasm exhibiting durable resistance to Sclerotinia sclerotiorum, also known as white mold. To date, the NSI has produced twenty one germplasm releases with improved tolerance to white mold; pinto bean (1), pea (3), sunflower (10), common bean (3), soybean (3), chickpea (1). NSI funded projects have also produced fourteen important variety releases with improved white mold resistance; pinto bean (4), soybean (3), common bean (3), lentil (2), great northern bean (2). The strategic deployment and use of these genetic resources by plant breeders, both public and private, will reduce losses to this devastating disease and help sustain the competitiveness of U.S. canola, pea, lentil, chickpea, common bean, soybean, and sunflower producers in domestic and global markets.

2. A method for assessing regional variation in common bean isolates of Sclerotinia sclerotiorum. National Sclerotinia Initiative collaborators have devised a unique method for determining pathogen variation across U.S bean-production areas that tests the hypothesis that pathogen isolate variation within and between test sites influences identification of white mold resistance. Mycelial compatibility groupings (MCGs), aggressiveness, and microsatellites (SSRs) were used to identify genotype and phenotype differences in the isolates that can influence stability of identified white mold resistance over time and location. NSI collaborators have demonstrated high aggressiveness and genetic variability (measured by MCGs and microsatellites) of pathogen isolates within and between field screening nursery locations,and greenhouse test isolates have been developed. The database of characterized isolates, available through Bean Improvement Cooperative websites, facilitates new isolate characterization and provides plant breeders and pathologists with critical information for choosing isolates in resistance screening for this devastating disease of common bean.

3. Fast-tracking Sclerotinia resistance development in hybrid sunflower. At the inception of the National Sclerotinia Initiative (NSI), commercial breeding for Sclerotinia head rot resistance in hybrid sunflower was uncoordinated, and it was unknown whether commercial hybrids differed in susceptibility to this devastating disease. Over the past several years, NSI collaborators have utilized a standardized regional approach to demonstrate significant, repeatable differences in the susceptibility of sunflower hybrids to Sclerotinia head rot. Key elements to the success of these efforts thus far have been the development of field-scale inoculation procedures and misting systems that reliably produce moderate to high levels of Sclerotinia head rot infection, needed to identify differential resistance of sunflower hybrids to Sclerotinia. Each year, the Sclerotinia head rot resistance of newly released commercial hybrids is assessed at five regional ‘common garden’ nurseries, thereby providing growers with site-specific and overall performance of individual sunflower hybrids. These standardized annual assessments have fostered improvements in the overall resistance to Sclerotinia head rot, increased the number of hybrids with improved levels of resistance, and have earned high praise from the National Sunflower Association and a participating private seed companies.

4. Sclerotinia risk management in canola. At present, about ninety-five percent of the U.S. canola crop is grown in North Dakota each year, and losses from Sclerotinia represent a major challenge to profitability. National Sclerotinia Initiative collaborators from North Dakota State University have developed a grower-oriented forecasting system, consisting of a general risk map and a risk calculator, designed to assist producers with managing Sclerotinia. The general risk map utilizes weather information to estimate risk of disease development throughout the canola-growing areas of the state. This map is updated twice weekly and posted on-line, beginning in mid-June and continuing throughout the canola flowering period each season. The risk calculator combines information on cultural practices, the field-specific past history of Sclerotinia, and current weather information- retrieved from the nearest weather station - to estimate the risk of disease development. This on-line tool is currently being used by producers throughout ND for the selection and timing of cultural and chemical interventions against Sclerotinia.

Last Modified: 9/2/2015
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