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Ecology and Epidemiology

Eruptive Germination of Sclerotia of Sclerotium rolfsii. Z. K. Punja, Graduate research assistant, Department of Plant Pathology, University of California, Davis 95616; R. G. Grogan, professor, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 71:1092-1099. Accepted for publication 9 February 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1092.

Eruptive germination, a previously undescribed from of germination of sclerotia of Sclerotium rolfsii, was characterized by plug(s) of mycelium erupting through the sclerotial rind, utilization of internal stored materials leaving an empty sclerotial rind, and by production of secondary sclerotia. This form of germination was observed on unsterilized field soil, on acid-washed and sterilized quartz sand, and on 1% Noble water agar. On 1% Bacto water agar and on Difco PDA, however, hyphal germination predominated. This form of germination was characterized by growth of individual hyphal strands from the surface of the sclerotium. Sclerotia of four isolates from 2-wk- to 8-mo-old sterile cultures in vitro and from artificially or naturally infested field soil germinated eruptively following drying for 710 hr at 1520% RH or exposure to volatiles from various dried and remoistened plant tissues (hay). Washing sclerotia for 15 hr under running water, treating for 3 min with 0.5% NaOCl, or puncturing the sclerotial rind each promoted eruptive germination to a lesser extent. The rate, but not the percent, of eruptive germination was increased if sclerotia were washed in water before drying or exposure to hay. Sclerotia conditioned to germinate eruptively exuded greater amounts of amino compounds and carbohydrates than nonconditioned sclerotia.