Isolation, Identification and Characterization of Trichoderma Species as a Potential Biocontrol Agent against Ceratocystis paradoxa

Abstract

Ceratocystis paradoxa is a plant pathogen causing diseases in several plants including coconut (Cocos nusifera). Infected coconut plants manifest “Stem bleeding” which is very common in Hambantota district in Sri Lanka. Coir and coir pith obtained from coconut husk provide substrates for the growth of the pathogen. The use of biological control agents (BCAs) has gained more attention in controlling plant pathogens because it minimizes the application of synthetic pesticides. In many researches, various strains of Trichoderma species have been studied to be used as BCAs against many plant pathogens. The present investigation was carried out in an attempt to isolate various strains of Trichoderma spp. from soil, litter and coir samples collected from different locations in Lunuwila area in the North Western Province of Sri Lanka, and to evaluate their potential as BCAs in controlling C. paradoxa. Several Trichoderma spp. were isolated into PDA plates. Colony morphology and morphological features of sporulating structures and spores were compared among the Trichoderma isolates. Genomic variability of isolates was determined by RFLP analysis of the PCR amplified DNA for the ITS region of the isolates using AluI enzyme. Potential ability of Trichoderma isolates in controlling the pathogen was observed using dual culture technique. Accordingly, ten different Trichoderma isolates were identified from soil but none from coir. The isolates were identified as T. viridae, T. polysporum, and T. harzianum. As BCAs, almost all Trichoderma isolates exhibited more than 60% growth inhibition of C. paradoxa on the seventh day of incubation in a dual culture.