Saprophytic and parasitic activities of some isolates of Corticium solani

Abstract

The biology of a collection of Corticium (Rhizoctonia) solani isolates from contrasting sources was studied in respect of their saprophytic and parasitic activities. The cellulolytic ability of all the isolates was demonstrated under different conditions in pure culture and in unsterile soil on processed and native forms of cellulosic substrates. The reactions of these isolates and others from weed roots to certain crop seedlings ranged from nil through mild parasitism to virulent pathogenicity. The introduction of cellulose film to soil in the presence of a range of C. solani isolates reduced the percentage germination and growth of lettuce. An extensive population of C. solani was found existing in a mild symptomless state of parasitism on many weed roots in a field without a history of C. solani disease, where it increased during the summer months, and the Corticium state was found on two weed hosts. A small amount of C. solani mycelium was detected in the soil away from plant roots. Anomalous morphological characters of the mycelium and of basidia in single basidiospore cultures are described. The potential variation demonstrated within individual isolates of C. solani coupled with their saprophytic and parasitic growth in soil during the summer is discussed in relation to the possible origin of certain outbreaks of C. solani disease in the field. This theory is supported by the incidence of C. solani in an affected field.