Trichoderma atroviride promotes tomato development and alters the root exudation of carbohydrates, which stimulates fungal growth and the biocontrol of the phytopathogen Phytophthora cinnamomi in a tripartite interaction system.

Several species of Trichoderma promote plant growth and help in defense against root pathogens. The role of root-exuded carbohydrates as chemo-attractive stimuli for Trichoderma colonization is attracting considerable interest. In this project, we studied the interaction between Trichoderma atroviride and tomato (Lycopersicon esculentum L. cv. Río Grande) plants in two different stages, before and during root colonization. In addition, the biocontrol capacity of T. atroviride against the phytopathogen Phytophthora cinnamomi in a tripartite interaction system was examined. We found that the beneficial effects of T. atroviride on plant growth were fine-tuned depending on the progress of interaction. Interestingly, the composition of the carbohydrate exudate from plants interacting with T. atroviride was different from that produced by other treatments and probably provided a nutritional source for the fungus. Particularly, sucrose was found only during root colonization by the fungus. Our data show that root-derived sugars enabled a higher Trichoderma growth rate, and that, in the tripartite interaction system with P. cinnamomi, the fungus competes for space and available soil nutrients more efficiently than P. cinnamomi, thereby antagonizing the growth of the phytopathogen.