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Germination and Infection by Basidiospores of Athelia (Sclerotium) rolfsii. Z. K. Punja, Postdoctoral Research Associate, Department of Plant Pathology, University of California, Davis 95616. R. G. Grogan, Professor, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 67:875-878. Accepted for publication 14 January 1983 . Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-875.

Two isolates of Sclerotium rolfsii from golf greens of bentgrass and annual bluegrass in Sacramento, CA, formed the basidial state (Athelia rolfsii) on potato-dextrose agar containing 2% activated charcoal. Basidiospore deposits were obtained by suspending pieces of agar with hymenium over petri dishes containing 1% Noble water agar that was adjusted to various pHs or that contained osmotica. Highest germination (8594%) of the basidiospores was observed at 2430 C, at a solute potential (φs) of 2.5 to 5 bars, and at pH 2.04.0. No basidiospores germinated below 15 C, at φs less than 40 bars, and at pH above 7.0. Bentgrass-annual bluegrass plugs from uninfected golf greens and bentgrass (Penncross) started in the greenhouse from seed were inoculated either with an aqueous suspension of basidiospores or by direct spore deposits from fruiting cultures; disease symptoms developed after incubation for 7 days at 100% relative humidity and 28 C. Extensive hyphae developed from germinating basidiospores and appressoria were formed on the leaf surface. Isolations from diseased leaves and crowns yielded typical colonies of S. rolfsii. This is the first report of infection by basidiospores of S. rolfsii; however, the epidemiological significance of the sexual state has not been established.

Keyword(s): southern blight, turf.