Population dynamics of the mycoparasite Verticillium biguttatum and its host, Rhizoctonia solani

Abstract

Evidence is provided for the potential regulation of the phytopathogenic fungus Rhizoctonia solani Kühn by the mycoparasite Verticillium biguttatum Gams in the tritrophic pathosystem with potato ( Solanum tuberosum L.). There was a close relationship between the population dynamics of the mycoparasite and that of its host fungus. Host mycelium development on the below-ground plant appeared to be a prerequisite for V. biguttatum development. An increase in R. solani was followed by an increase in V. biguttatum; the increase depended on the initial soil population densities, temperature and soil type. A positive correlation was observed between host fungus population density and the parasitized fraction suggesting that V. biguttatum may cause population density-dependent mortality. This may explain the decline in Rhizoctonia observed after growing several consecutive potato crops on the same field. In the absence of the host plant, mycoparasitism played a minor role in regulating R. solani as contact between host and mycoparasite could not be established. Verticillium bigultatum was able to survive in plant-free soil for at least 4 yr.