Resistance of Hosta Cultivars to Petiole Rot Caused by Sclerotium rolfsii var. delphinii

Abstract

<jats:p>Eighteen cultivars of hosta (<jats:italic>Hosta</jats:italic> spp.), selected to represent a wide range of size, leaf shape and color, and genetics, were evaluated for reaction to <jats:italic>Sclerotium rolfsii</jats:italic> var. <jats:italic>delphinii</jats:italic> 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 <jats:italic>S. rolfsii</jats:italic> at the base of the plant. Disease severity was assessed weekly for 6 weeks as percent symptomatic petioles. Disease development varied significantly (<jats:italic>P</jats:italic> &lt; 0.05) among cultivars. Overall, `Lemon Lime', `Munchkin', `Nakaiana', `Platinum Tiara', and `Tardiflora' had the most severe symptoms and `Halcyon' showed the least disease.</jats:p>

Development of a Rapid Method Using Oxalic Acid to Assess Resistance Among Hosta Cultivars to Petiole Rot Caused by Sclerotium rolfsii var. delphinii

“…In field trials, cultivars Nakaiana, Munchkin, and Lemon Lime were most susceptible to petiole rot, Zounds showed moderate resistance, and Halcyon, Snow Mound, and Honeybells were the most resistant (Table 1). Spearman's coefficients of rank correlation between the greenhouse trial by Edmunds et al (6) and field trials were 0.57 (nonsignificant, P = 0.18) for the 2005 trial and 0.83 (significant, P < 0.05) for the 2006 trial, indicating that results from the field trials were generally consistent with those of greenhouse inoculation trials (6).…”

“…Cultivar selection. Hosta cultivars or species used in the present trials (Nakaiana, Munchkin, Lemon Lime, Tardiflora, Pearl Lake, Zounds, Gold Drop, Halcyon, Snow Mound, Honeybells, and H. kikutii) exhibited a range of resistance to petiole rot in previous greenhouse inoculation trials (6). Halcyon was highly resistant, whereas the other cultivars ranged from very susceptible to moderately resistant.…”

“…Spearman's coefficient of rank correlation between the greenhouse trial by Edmunds et al (6) and the spray-applied oxalic acid trial was 0.77 (significant, P < 0.05). Table 1.…”

“…The Tukey-Kramer test was used to compare means of incidence of leaves with lesions among cultivars. Spearman's coefficient of rank correlation was used to measure the correlation between ranks of cultivars and species response in greenhouse trial by Edmunds et al (6) and the spray-applied oxalic acid trial.…”

“…delphinii among the more than 4,000 named hosta cultivars is scant. In a greenhouse evaluation of 18 hosta cultivars, Edmunds et al (6) inoculated plants by placing a carrot disk infested with mycelium of S. rolfsii var. delphinii at the base of each plant.…”