Germination and Infection by Basidiospores ofAthelia(Sclerotium)rolfsii

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Abstract
Two isolates of Sclerotium rolfsii from golf greens of bentgrass [Agrostis tenuis] and annual bluegrass [Poa annua] in Sacramento, California [USA], formed the basidial state (A. 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 pH or that contained osmotica. Highest germination (85-94%) of the basidiospores was observed at 24.degree.-30.degree. C, at a solute potential (.psi.s) of -2.5 to -5 bars, and at pH 2.0-4.0. No basidiospores germinated below 15.degree. C, at .psi.2 < -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.degree. 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 1st report of infection by basidiospores of S. rolfsii; the epidemiological significance of the sexual state has not been established.