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Ecology and Epidemiology

Relation of Carbon Loss from Sclerotia of Sclerotium rolfsii During Incubation in Soil to Decreased Germinability and Pathogenic Aggressiveness. M. Hyakumachi, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, Present address: 1-1 Yanagido, Gifu University, Faculty of Agriculture, Gifu 501-11, Japan; J. L. Lockwood, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Phytopathology 79:1059-1063. Accepted for publication 5 June 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-1059.

Endogenous carbon from 14C-labeled sclerotia of Sclerotium rolfsii was progressively lost during 50 days of incubation in soil at ? m = 10 mbar. The 14C loss was mainly accounted for as residual 14C in the soil (4.19.3% of the total label) and as 14CO2 evolved from the soil (26.038.4% of the total label). 14CO2 accounted for 45.988.4% of the total 14C loss, and sclerotial respiration was estimated to account for 42.277.2% of the 14C loss during the same incubation time. Sclerotia incubated in soil became dependent on nutrients for germination and lost viability when the 14C loss reached approximately 20 and 40%, respectively. Radish seedlings inoculated with sclerotia that had lost more than 20% of their 14C had significantly longer shoots than seedlings inoculated with nonincubated sclerotia.