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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower and Plant Biology Research » Research » Publications at this Location » Publication #121201
Title: METHODS OF INOCULATION AND INCIDENCE OF SCLEROTINIA HEAD ROT IN SUNFLOWER

Author
item VAN BECELAERE, G - NDSU - PLANT SCIENCE DEPT
item Miller, Jerry

Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sclerotinia disease is one of the most important pathogens attacking sunflower. The head rot form caused epidemic proportions in the U.S. in 1999 with severe infections causing losses up to 100% in some fields. Although complete resistance (immunity) in cultivated sunflower has not been reported, significant differences in the level of susceptibility have been identified in diverse germplasm. The objective of this study was to find an effective technique of inoculation of sunflower that could be utilized to test the level of susceptibility and discover differences among germplasm. Treatments included ascospores versus mycelium inoculum, inoculum rate, adding water after inoculation, and brown versus white bags. The experiment was a success with considerable infection occurring among treatments. Conclusion of the experiment indicated that inoculation with ascospores was more effective than mycelia, the recommended rate of inoculum would be 5000 ascospores/ml, brown bags were more favorable than white bags, and application of additional water did not have any effect on the degree of infection. A measurement of infection 35 days after inoculation was the most accurate to determine differences among treatments.

Technical Abstract: Sclerotinia sclerotiorum disease is one of the most important pathogens attacking sunflower (Helianthus annuus L.). The head rot form caused epidemic proportions in the U.S. in 1999 with severe infections causing losses up to 100% in some fields. Although complete resistance (immunity) in cultivated sunflower has not been reported, significant differences in the level of susceptibility have been identified in diverse germplasm. The objective of this study was to find an effective technique of inoculation of sunflower that could be utilized to test the level of susceptibility and discover differences among germplasm. Treatments included inoculum type (ascospores versus a ground mycelium/wheat mixture), inoculum rate, adding water after inoculation, and brown versus white bags. The experiment was a success with considerable infection occurring among treatments. Conclusion of the experiment indicated that inoculation with ascospores was more effective than mycelia, the recommended rate of inoculum would be 5000 ascospores/ml, brown bags were more favorable than white bags, and application of additional water did not have any effect on the degree of infection. A measurement of infection 35 days after inoculation was the most accurate to determine differences among treatments.