Eruptive Germination of Sclerotia ofSclerotium rolfsii

Abstract

Eruptive germination, a previously undescribed form of germination of sclerotia of S. 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 [potato dextrose agar], hyphal germination predominated. This form of germination was characterized by growth of individual hyphal strands from the surface of the sclerotium. Sclerotia of 4 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 7-10 h at 15-20% RH [relative humidity] or exposure to volatiles from various dried and remoistened plant tissues (hay). Washing sclerotia for 1-5 h under running water, treating for 3 min with 0.5% NaOCl, or puncturing the sclerotial rind each promoted eruptive germination to a lessor 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.