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United States Department of Agriculture

Agricultural Research Service

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Research Project: Facilitating Management of Sclerotinia Head Rot of Sunflowers Through Screening of Hybrids for Resistance & Evaluating Fungicides for Effica

Location: Sunflower Research

Project Number: 3060-21220-028-02
Project Type: Specific Cooperative Agreement

Start Date: Jul 01, 2012
End Date: Sep 30, 2015

Objective:
To facilitate improved management of Sclerotinia head rot, caused by Sclerotinia sclerotiorum, by supporting efforts to breed sunflowers for resistance, by evaluating the potential of fungicides to manage this disease, and by improving the methods used to screen sunflowers for resistance to head rot.

Approach:
Objective 1. Provide an affordable Sclerotinia head rot screening service to private sunflower breeders to ensure continued progress in breeding sunflowers for resistance. Sunflower hybrids and experimental lines will be solicited from sunflower seed companies and breeding programs. Fees will be assessed for each line submitted for testing, but partial grant support is requested to keep the service affordable. Three types of screening nurseries will be established: (1) nurseries at four locations for screening up to 25 advanced breeding lines and commercial hybrids across multiple environments, (2) a nursery for screening up to 80 breeding lines in a single environment, and (3) a “selection nursery” for screening up to 20 lines. In the selection nursery, heads will be bagged, and seed will be collected from all heads that do not develop disease. Resistant and susceptible checks will be included in all nurseries, and the design will be a randomized complete block with four replicates. Disease will be promoted by inoculating with ascospores of S. sclerotiorum at flowering and irrigating with microsprinklers (misting systems). Objective 2. Assess the relative susceptibility of sunflowers to Sclerotinia head rot at R5 (flowering), R6, R7, and R8 growth stages, and whether a hybrid exhibiting resistance or susceptibility to head rot when inoculated at flowering maintains the same disease response when inoculated after flowering. The susceptibility of sunflowers to Sclerotinia head rot at R5, R6, R7, and R8 growth stages will be tested on each of two sunflower hybrids, one that is partially resistant and one that is partially susceptible to head rot when inoculated at R5. Oilseed hybrids sharing nearly identical maturity will be selected. The experiment will be a completely randomized split-split-plot design with four replications; post-inoculation environment (bagged heads or unbagged heads) will be the main factor, sunflower hybrid will be the subplot factor, and inoculation timing will be the sub-subplot factor. The full experiment will be conducted in Carrington and Langdon, ND and a reduced experiment (split-plot design with unbagged heads and no R8 inoculation) will be conducted in Oakes, ND. Sunflower heads will be inoculated with ascospores, and disease development will be facilitated with overhead misting systems. Objective 3. Establish uniform fungicide trials in three environments to identify the potential of fungicides for managing Sclerotinia head rot of sunflower. Fungicides registered or with anticipated registration on sunflower and fungicides with efficacy against Sclerotinia on other crops will be evaluated for their ability to control Sclerotinia head rot of sunflower. Nine fungicides and a non-treated control will be evaluated at Carrington, ND, Langdon, ND, and Scottsbluff, NE. The experiments will be a randomized complete block design with four replicates. Fungicides will be applied at bloom initiation and again approximately 10 days later. Disease will be promoted by inoculating with ascospores of S. sclerotiorum at flowering and irrigating with microsprinklers (misting systems).

Last Modified: 10/21/2014
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