Mechanisms of biological control of the damping-off fungus, Pythium ultimum, by binucleate Rhizoctonia / by K. Siwek.

Abstract

This thesis investigates the mechanism(s) involved in the protection of Capsicum seedlings by two isolates of BNR against the damping-off fungus, P.u. sporangiiferum. Emphasis is placed on ecological attributes of the antagonists in relation to the pathogen, in conditions resembling those of the nursery environment for which biological control is intended. It is proposed that competition for resources, such as the host tissues with exudate-rich infection sites and the organic residue in the potting mix, is the principal factor influencing the interactions between P.u. sporangiiferum and BNR. It is also suggested that BNR isolates employ at least three strategies to exert competitive advantage over P.U. sporangiiferum. It is postulated that the ability of BNR to capture and utilise resources, in the presence of a potential competitor, is the principal attribute of these biocontrol agents that brings about a sucessful control of P.u. sporangiiferum in nursery potting mix.