Colonization of Vitis vinifera L. by the Endophyte Trichoderma sp. Strain T154: Biocontrol Activity Against Phaeoacremonium minimum

Trichodermastrains used in biological control products usually exhibit high efficiency in the control of plant diseases. However, their behavior under field conditions is difficult to predict. In addition, the potential of indigenous strains has been poorly assayed as well as their possible behavior as endophytes. Hence, niche colonization is a key feature for an effective protection. In this study, we aimed to: (i) explore the possibility of using a newTrichodermastrain isolated from vine to control pathogens, (ii) study thein plantainteraction with the pathogenPhaeoacremonium minimumW. Gams, Crous, M.J. Wingf. & L. Mugnai (formerlyPhaeoacremonium aleophilum), a pioneer fungus involved in Grapevine Trunk Diseases (GTDs) such as esca. For this purpose, fluorescently taggedTrichodermasp. T154 and aP. minimumstrain were used for scanning electron microscopy and confocal scanning laser microscopy analyses. Data showed that theTrichodermastrain is able to colonize plants up to 12 weeks post inoculation and is located in xylem, fibers, as well as in parenchymatic tissues inside the wood. The beneficial fungus reduced colonization of the esca-related pathogen colonizing the same niches. The main observed mechanism involved in biocontrol ofTrichodermaagainst the esca pathogen was spore adhesion, niche exclusion and only few typical hypha coiling was found betweenTrichodermaand the pathogen. These results suggest that theTrichodermastrain has potential for reducing the colonization ofPhaeoacremonium minimumand thus, an inoculation of this biological control agent can protect the plant by limiting the development of GTD, and the strain can behave as an endophyte.