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United States Department of Agriculture

Agricultural Research Service

Title: Epidemiology and Resistance to Sclerotinia Head Rot in Wild Sunflower Species

Authors
item Rashid, Khalid - AGRIC & AGRI-FOOD CANADA
item Seiler, Gerald

Submitted to: Proceedings of the International Sclerotinia Workshop
Publication Type: Abstract Only
Publication Acceptance Date: January 10, 2004
Publication Date: January 20, 2004
Citation: Rashid, K.Y., Seiler, G.J. 2004. Epidemiology and resistance to sclerotinia head rot in wild sunflower species. Proceedings of the International Sclerotinia Workshop.

Interpretive Summary: Field trials were conducted in 2002 and 2003 to understand the epidemiology of the Sclerotinia infections on wild sunflower heads and stems, to establish methodology for assessing wild sunflower germplasm, and to identify sources of resistance. Ninety-six accessions of wild sunflower species were evaluated using artificial inoculation with ascospores, fungal mycelia, and ground infected-millet seed. Plants were covered for 14 days after inoculation with light brown paper bags, sunflower pollination bags, and thin plastic bags. These treatments were repeated three times at two week intervals using different wild sunflower accessions every time. A few puffs of water were applied into each covering using a hand-held sprayer at the second and third day after inoculation to maintain high humidity and enhance the infection and disease development processes. Very little infection had occurred in the wild sunflower heads, but the stems were infected and showed typical symptoms of bleaching, shredding, and the formation of tiny cylindrical sclerotia inside the stems. The ground infected-millet inoculum resulted in the highest level of infection followed by ascospores and fungal mycelia. The paper bag covering resulted in the highest infection level followed by sunflower pollination bags. Plastic bags were not very effective covers. The combination of ground infected-millet inoculum and the paper bag cover resulted in 88% infection in 2002 and 55% in 2003. Fifteen accessions remained healthy under the various artificial inoculation methods in both years of this study. Such accessions are believed (suspected) to have genetic resistance to Sclerotinia. Future research will focus on studying the genetics of this resistance and the transfer of the resistance genes to sunflower hybrids.

Technical Abstract: Field trials were conducted in 2002 and 2003 to understand the epidemiology of the Sclerotinia infections on wild sunflower heads and stems, to establish methodology for assessing wild sunflower germplasm, and to identify sources of resistance. Ninety-six accessions of wild sunflower species were evaluated using artificial inoculation with ascospores, fungal mycelia, and ground infected-millet seed. Plants were covered for 14 days after inoculation with light brown paper bags, sunflower pollination bags, and thin plastic bags. These treatments were repeated three times at two week intervals using different wild sunflower accessions every time. A few puffs of water were applied into each covering using a hand-held sprayer at the second and third day after inoculation to maintain high humidity and enhance the infection and disease development processes. Very little infection had occurred in the wild sunflower heads, but the stems were infected and showed typical symptoms of bleaching, shredding, and the formation of tiny cylindrical sclerotia inside the stems. The ground infected-millet inoculum resulted in the highest level of infection followed by ascospores and fungal mycelia. The paper bag covering resulted in the highest infection level followed by sunflower pollination bags. Plastic bags were not very effective covers. The combination of ground infected-millet inoculum and the paper bag cover resulted in 88% infection in 2002 and 55% in 2003. Fifteen accessions remained healthy under the various artificial inoculation methods in both years of this study. Such accessions are believed (suspected) to have genetic resistance to Sclerotinia. Future research will focus on studying the genetics of this resistance and the transfer of the resistance genes to sunflower hybrids.

Last Modified: 10/1/2014
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