Ganoderma lucidum Mycelia as Potential Antimicrobial and Biological Control Agents of Selected Soil-borne Plant Pathogens

Abstract

Ganoderma lucidum mycelia were tested for its potential antimicrobial activities against selected soil-borne plant pathogens. Fusarium oxysporum, Rhizoctonia solani and Sclerotium rolfsii were the fungal pathogens and Ralstonia solanacearum and Staphylococcus aureus were the bacterial pathogens used. In vitro experiment employed antimicrobial assays. Morphological characteristics of the fungal specimens were observed and were compared to commercial fungicide Dithane® and distilled water to determine the antifungal activity of Ganoderma lucidum mycelia. Pathogenic fungal growth was moderately inhibited as shown by the mycelial development and secondary metabolite production of Ganoderma lucidum and sclerotial body formation of the pathogens. This was confirmed using Bell et. al. rating, such that the given isolate was not highly antagonistic to the fungal pathogens tested. The zones of inhibition of bacteria were measured and were compared to an antibacterial Amoxicillin and distilled water using DMRT and ANOVA to determine the antibacterial activity of both mycelial commercial extract and pre-extracted mycelia. Both extracts increased the diameter of inhibition zones. The in vivo experiment was carried out to determine the ability of Ganoderma lucidum in disease suppression. Tomato seedlings were infected by Fusarium oxysporum, Rhizoctonia solani, Sclerotium rolfsii and Ralstonia solanacearum and the effects of Ganoderma lucidum spawn were evaluated and were compared to the untreated infected seedlings. Increased shoot growth rate was observed in treated seedlings though ANOVA revealed that the values obtained were not significantly different to the untreated seedlings. The manifestations of disease were significantly delayed though there was no significant difference in disease incidence between the treated and untreated seedlings within the one month observation period. Ganoderma lucidum spawn offers the possibility of biological control against Rhizoctonia solani and Sclerotium rolfsii.