Assessing the Various Antagonistic Mechanisms of Trichoderma Strains against the Brown Root Rot Pathogen Pyrrhoderma noxium Infecting Heritage Fig Trees

Abstract

A wide range of phytopathogenic fungi exist causing various plant diseases, which can lead to devastating economic, environmental, and social impacts on a global scale. One such fungus is <i>Pyrrhoderma noxium</i>, causing brown root rot disease in over 200 plant species of a variety of life forms mostly in the tropical and subtropical regions of the globe. The aim of this study was to discover the antagonistic abilities of two <i>Trichoderma</i> strains (#5001 and #5029) found to be closely related to <i>Trichoderma reesei</i> against <i>P. noxium</i>. The mycoparasitic mechanism of these <i>Trichoderma</i> strains against <i>P. noxium</i> involved coiling around the hyphae of the pathogen and producing appressorium like structures. Furthermore, a gene expression study identified an induced expression of the biological control activity associated genes in <i>Trichoderma</i> strains during the interaction with the pathogen. In addition, volatile and diffusible antifungal compounds produced by the <i>Trichoderma</i> strains were also effective in inhibiting the growth of the pathogen. The ability to produce Indole-3-acetic acid (IAA), siderophores and the volatile compounds related to plant growth promotion were also identified as added benefits to the performance of these <i>Trichoderma</i> strains as biological control agents. Overall, these results show promise for the possibility of using the <i>Trichoderma</i> strains as potential biological control agents to protect <i>P. noxium</i> infected trees as well as preventing new infections.