Biocontrol of Rhizoctonia solani causing stem canker disease of potato using rhizosphere mold fungi

Abstract

The aim of the present work is to obtain effective rhizosphere fungal bio-control agents (bio-fungicides) that can antagonize Rhizoctonia solani; the fungal causal agent of stem canker disease of potato (Solanum tuberosum L.) and to improve the growth of the potato plant. A total of eleven different isolates of mold fungi were isolated from the rhizosphere soil of potato plants collected from three different potato cultivation areas in El-Monofia governorate-Egypt. Three isolates belong to the genus of Fusarium and three to Aspergillus, whereas the other five isolates belong to the genera of Penicillium, Absidia, Mucor, Gliocladium and Alternaria. In dual culture technique on Sabouraud dextrose agar media, three species (Gliocladium virens; Penicillium oxalicum and Trichoderma viride), completely surrounded the pathogen colonies and prevented their radial spread. In vivo results of antagonism in greenhouse were very promising as growth of potato plant was highly promoted by the three bio-agents compared with positive and non-infested control plants. Studies on soil population dynamics of selected Gliocladium virens showed a gradual decrease in CFU with increasing periods of incubation. Maize kernels and wheat bran were the best solid substrates for the mass production of Gliocladium virens conidia especially at 30% initial moisture level. The highest percentage of viable conidia of formulated Gliocladium virens was obtained on storage at 4˚C. Gliocladium virens showed promising results of antagonizing R. solani in vitro and improving potato growth under greenhouse conditions, subsequently, could be mass produced and formulated to be used as an effective biofungicide.