In vitro evaluation of antagonistic effect of Trichoderma spp. against white root disease of rubber

Abstract

Trichoderma is one of the most studied and applied fungal biocontrol agents. Secondary metabolites play a significant role in antagonistic activities of some biocontrol species of Trichoderma resulting in the suppression of plant pathogens. White root disease, caused by Rigidoporus microporus, is rapidly spreading in Sri Lankan rubber plantations, posing a serious threat. In this study a laboratory experiment was carried out to identify the antagonistic effect of two native Trichoderma spp. and their secondary metabolites on Rigidoporus microporus. Trichoderma spp. (strain 01) with Rigidoporus microporus and Trichoderma spp. (strain 02) with Rigidoporus microporus were inoculated into Potato Dextrose Broth medium and 12 days old culture filtrates were prepared. Five concentrations 15%, 30%, 45%, 60% and 75% (v/v) of the culture filtrates were tested using the Poison Food Technique on Rigidoporus microporus with three replicates. There was a significant interaction between Trichoderma spp. and concentration of the culture filtrates (p < 0.05). It showed the highest mean percentage growth inhibition by both strains at 75% concentration and least mean percentage growth inhibition at 15% concentration. The mean percentage of growth inhibition at 75% concentration of Trichoderma spp. (strain 01) was 71.39% and Trichoderma spp. (strain 02) was 71.45%. The mean percentage of growth inhibition at 15% concentration of Trichoderma spp. (strain 01) was 41.89% and Trichoderma spp. (strain 02) was 13.32%. The results indicated that Trichoderma spp. strain 01 and 02 produce a thermo stable toxic substance to inhibit white root disease causative pathogen Rigidoporus microporus because it has not lost its functionality even after being sterilized. Higher the concentration of the secondary metabolites, greater was the growth inhibition of the pathogen Rigidoporus microporus.