Abstract

A Hypocrea/Trichoderma strain was isolated from cacao (Theobroma cacao L.) pods from a cacao plantation in Huimanguillo, Tabasco, Mexico. The strain was identified as H./T. viridescens ITV43 by its morphological characteristics and DNA sequence analysis of ITS1-5.8s-ITS2 and was tested against Moniliophthora roreri Cif & Par and Phytophthora strains by confrontation experiments. The biocontrol of H./T. viridescens ITV43 measured as biocontrol index (BCI) at seven days against M. roreri(HT-ITV01, HT-ITV20, HT-ITV27), P. megasperma (HT-ITV08, HT-ITV15, HT-ITV37) and P. capsici (HT-ITV14, HT-ITV16, HT-ITV33) strains ranged from 78.28-81.63, 63.04-69.95 and 69.77-76.31%, respectively. After 31 days of incubation, the BCI values increased to 81.52-86.50 for M. roreri and 100% for Phythopthora strains. Samples taken from the interaction zone were observed by optical and scanning electron microscopy. The results show the effect of H./T. viridescens ITV43 strain on morphological deformations and disorganization of the M. roreri and Phytophthora cell wall structures. Highest BCI values obtained suggest that the Hypocrea strains isolated from T. cocoa could have the ability to antagonize more efficiently against fungal pathogens of this crop.

Key words: Antagonism, Hypocrea, mycoparasitism, Moniliophthora, Phytophthora, Theobroma.