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United States Department of Agriculture

Agricultural Research Service

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Location: Sunflower and Plant Biology Research

Project Number: 5442-21220-028-06-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jun 1, 2009
End Date: May 31, 2014

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.

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.

Last Modified: 10/19/2017
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