ISOLATION AND in vitro SELECTION OF NATIVE STRAINS OF Trichoderma spp. FOR THE BIOCONTROL OF Fusarium sp. IN Euphorbia pulcherrima

Abstract

Plant wilting due to root rot caused by Fusarium sp. is one of the main diseases of poinsettia in Morelos, so that many sprays of chemical fungicides are done to control the disease. This research has as main objective to look for native strains of Trichoderma spp. with potential to be used as biocontrol agents against the pathogen. From regional materials used as organic components of potting mixes to grow poinsettia, a number of Trichoderma spp. strains were isolated and purified; at the same time, from symptomatic poinsettia plants, strains of Fusarium sp. were isolated and purified. Nine strains of Trichoderma spp. and five strains of Fusarium sp. were selected to be evaluated in vitro by the technique of dual culture. Performance of the Trichoderma spp. strains to compete for space and nutrients, micoparasitism and antibiosis was evaluated; regression models with best fit were defined for the radial colony growth variable. All the Trichoderma spp. strains had higher colony growth rate than Fusarium sp. strains; three of the Trichoderma spp. strains had a high micoparasitism activity and one showed a strong capacity to modify the color of the growing media. The biocontrol mechanisms of Trichoderma spp. against pathogens were observed and it was possible to select the most promising strains.