Skip to main content
ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower and Plant Biology Research » Research » Publications at this Location » Publication #181487
Title: AN INOCULATION METHOD FOR SCLEROTINIA STALK ROT

Author
item Gulya Jr, Thomas

Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings
Publication Acceptance Date: 3/15/2004
Publication Date: 3/1/2004
Citation: Gulya Jr, T.J. 2004. An inoculation method for Sclerotinia stalk rot. Sunflower Research Workshop Proceedings. 26th Sunflower Research Workshop, January 14-15, 2004, Fargo, ND. Available: http://www.sunflowernsa.com/research/research-workshop/documents/Gulya_StalkRot_04.PDF

Interpretive Summary: Sclerotinia stalk rot and head rot are the two most devastating diseases of sunflower in North America. Development of resistant germplasm depends upon accurate, consistent evaluations of disease response. In the past, evaluations for Sclerotinia stalk rot were done under conditions of natural infection, which produced variable results, and in some years no usable information was obtained. To overcome this problem, we developed an artificial inoculation method to (1) incite stalk rot, but (2) in a manner that allowed discrimination between sunflower varieties (i.e. without killing everything). The method consists of growing the fungus on cooked grain (millet or oats), drying it, and storing it until needed. A small quantity (1 oz) is placed in a furrow beside the row 4 to 6 weeks after planting (when the plants are still relatively small). Stalk rot symptoms appear 4 to 5 wk later. Differences between sunflower varieties persist from the earliest symptoms until the end of the season. This method can be made more efficient by using a tractor-drawn granular chemical applicator to meter out the inoculum, which we plan to test in 2004.

Technical Abstract: Sclerotinia stalk rot and head rot are the two most devastating diseases of sunflower in North America. Development of resistant germplasm depends upon accurate, consistent evaluations of disease response. In the past, evaluations for Sclerotinia stalk rot were done under conditions of natural infection, which produced variable results, and in some years no usable information was obtained. To overcome this problem, we modified an existing artificial inoculation method to (1) incite stalk rot, but (2) in a manner that allowed discrimination between sunflower varieties (i.e. without killing everything). The method consists of growing the fungus on cooked grain (millet or oats), drying it, and storing it at 4 C until needed. A small quantity (40 g) is placed in a furrow 15-20 cm beside the row 4 to 6 weeks after planting (when the plants are at the V-6 to V-8 stage). Stalk rot symptoms appear 4 to 5 wk later. The method was tested at four environments with four sunflower genotypes. In 2004, the method was verified with 20 commercial hybrids tested at four locations. The rankings of the hybrids did not differ significantly between locations. With this method, we should be able to evaluate both the germplasm in the USDA sunflower breeding program and commercial hybrids. The method may also be applicable to testing wild Helianthus species in field trials. This method can be made more efficient by using a tractor-drawn granular chemical applicator to meter out the inoculum, which we plan to test in 2004.