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United States Department of Agriculture

Agricultural Research Service

Research Project: EVALUATION OF SUNFLOWER HYBRIDS AND GERMPLASM FOR RESISTANCE TO SCLEROTINIA
2010 Annual Report


1a.Objectives (from AD-416)
The overall objective of this project is to identify and determine resistance to sclerotinia among commercial sunflower hybrids and germplasm used in breeding programs. An additional aspect of this project is to develop and refine misting systems that create the environment conducive for sclerotinia. This aspect of the project will not only generate reproducible and reliable data that identifies genetic resistance, but will better identify the environmental onditions necessary for sclerotinia infection and development.


1b.Approach (from AD-416)
Sunflower hybrids and advanced experimental lines with expected resistance or tolerance to sclerotinia head rot will be solicited from sunflower seed companies and breeding programs. Two sets of screening nurseries will be developed, one to screen new hybrid lines that have not been publicly evaluated and another set of hybrids to confirm the resistance that was previously defined. The new hybrid lines will be compiled into the “Initial Screening” which will include about 75 entries and be planted at Carrington, ND, and Morden, Manitoba. The best lines with resistance from previous evaluations will be compiled into the “Repeat Screening” which will include about 25 entries. The “Repeat” test will be planted at Carrington; Morden; Langdon, ND; and Oakes, ND. Each hybrid will be established in plots 1-row (30-inch) wide by 25 ft long and arranged in a randomized complete block with four replications. At the onset of flowering, 15 to 20 individual heads within each plot will be artificially inoculated with ascospores over a period of time to accommodate the differential development within and among hybrids. Misting systems will be constructed and activated before inoculation and remain operational based on the prevailing environment as necessary to favor disease development. Sunflower disease incidence and severity will be scored at a minimum of two timings. Scientists from the USDA-ARS Sunflower Research Unit will provide the ascospores inoculant to be used throughout the sunflower misting systems projects. A large misting system will be assembled and operated at the Carrington REC for the sole purpose of accommodating germplasm and breeding lines from the USDA-ARS Sunflower Research Unit scientists. Sunflower plots will be established by the USDA-ARS team and the disease assessments will be determined by the USDA-ARS scientists. The Carrington REC staff will assemble and manage the misting system and will make the ascospores inoculations as appropriate within this nursery. A separate nursery will be established at Carrington to evaluate sunflower hybrids and germplasm for resistance to sclerotinia stalk rot.

Misting systems will be established and managed to create contrasting micro-climates that will be assessed to determine their ability to create conditions favorable for sclerotinia head rot infections and thus the evaluation of sunflower resistance. The contrasting micro-climates will be developed by utilizing different misting timings, misting durations, and mist intensities. The misting systems will be equipped with different emitters, spacing, and risers along with timers to achieve the different environments. Climate and plant canopy sensors tied to data loggers will be used to record the micro-climate variables. A series of known sunflowers hybrids will be planted and inoculated with ascospores in accordance with proven procedures. Assessments of head rot infection will be recorded and compared across the different misting system regimes. The different climatic data that is associated with each misting regime will evaluated to identify those conditions that best promote sclerotinia head rot infections.


3.Progress Report

This project was initiated on June 1, 2009, research is ongoing, and the overall objectives of this project are to identify sunflower cultivars which are less susceptible to Sclerotinia head rot and to study chemical and biological control options for managing this disease. ADODR monitoring activities to evaluate research progress included phone calls, meetings with the cooperator, and an annual meeting held each year in January.

Developing rapid screening field techniques for developing Sclerotinia resistance in sunflower: Incidence of Sclerotinia sclerotiorum in commercial sunflower production is a common occurrence that often results in serious loss in crop yield and quality. These disease outbreaks have resulted in frequent economic losses to both the producers and processors. The impact of Sclerotinia on the supply and quality of sunflower seed has on occasion compromised the viability of the sunflower industry. The overall objective of this project is to identify and determine resistance to Sclerotinia among commercial sunflower hybrids and germplasm used in public and private breeding programs. Achieving reliable identification of resistance or good tolerance among commercial sunflower hybrids will result in an effective tool for sunflower producers to lower their risk of infection and the associated yield and quality losses. An additional aspect of this project is to develop and refine misting systems that create the environment conducive for Sclerotinia development. This aspect will generate reproducible and reliable data that identifies genetic resistance. The experiences and data collected will also create a better understanding of the epidemiology of head rot form of Sclerotinia. The specific objectives of this project are: Evaluate commercial sunflower hybrids and experimental lines for improved resistance to Sclerotinia head rot; Implement and manage germplasm screening nurseries for USDA-ARS breeders and geneticists to evaluate sunflower germplasm and breeding lines for improved resistance to Sclerotinia head rot and stalk rot; and Refine management of Sclerotinia misting systems to improve their effectiveness in creating a micro-climate favorable for Sclerotinia infections and thereby the knowledge of Sclerotinia epidemiology. The project objectives are designed to generate new knowledge that will directly benefit sunflower producers, seed companies, and processors. In addition, information will be gained that will be useful to researchers as they work to better understand the biology of this pathogen and the environmental conditions that promote serious infections.


Last Modified: 10/22/2014
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