Resistance of hosta cultivars to petiole rot caused by Sclerotium rolfsii var. delphinii

Abstract

Eighteen cultivars of hosta (Hosta spp.), selected to represent a wide range of size, leaf shape and color, and genetics, were evaluated for reaction to Sclerotium rolfsii var. delphinii in a greenhouse in Ames, Iowa in 2000 and 2001. Bare-root, single-eye plants were planted in 15.2-cm (6-inch) pots in a soil-containing (2000) and soilless (2001) mix and grown in a greenhouse for 3 months. Plants were then inoculated by placing a carrot disk infested with mycelium of S. rolfsii at the base of the plant. Disease severity was assessed weekly for 6 weeks as percent symptomatic petioles. Disease development varied significantly (P < 0.05) among cultivars. Overall, 'Lemon Lime', 'Munchkin', 'Nakaiana', 'Platinum Tiara', and 'Tardiflora' had the most severe symptoms and 'Halcyon' showed the least disease.