Submitted to: Proceedings of the International Sclerotinia Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 2/5/2003
Publication Date: N/A
Technical Abstract: Work was conducted in 2002 to understand the epidemiology of the Sclerotinia infections to wild sunflower heads and stems and to establish methodology for assessing germplasm accessions of wild sunflower species under field conditions. Ninety-two accessions of wild sunflower species were evaluated. Artificial inoculation of the plants was conducted using ascospores, fungal mycelia, ground infected millet seed, and a non-inoculated control. Plants were covered for 14 days after artificial inoculation with light brown paper bags, sunflower pollination bags, thin plastic bags, and uncovered control plots. These processes of artificial inoculation and head covering was repeated three times at 2-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 a high humidity and enhance the infection and disease development processes. The preliminary results for this study indicate that very little infection appears to have occurred on the wild sunflower heads, but the stems were infected and showed typical Sclerotinia symptoms with sclerotia bodies inside the stems. The infected ground millet inoculum resulted in the highest level of stem infection followed by fungal mycelia and ascospores. The covering of heads and stems with paper bags resulted in the highest infection levels followed by sunflower pollination bags. Plastic bags were not very effective as covers. The combination of infected ground millet for artificial inoculation and the paper bag covers after inoculation resulted in 88% infected wild sunflower accessions. A few accessions remained healthy under the various artificial inoculation methods and covering materials, and are suspected to have genetic resistance to Sclerotinia. These results will be confirmed in a repeated trial in 2003.