Characterization of novel Trichoderma spp. isolates: phytostimulant and biocontrol properties in the model plant Arabidopsis thaliana

Among microbials, Trichoderma spp. have been the focus of significant research due to their capacity to promote plant growth and suppress a wide range of phytopathogens. A total of 27 native isolates of Trichoderma spp. were obtained from diverse agroecological regions of the province of Tucumán, Argentina, and were characterized by their antagonistic activity and phytostimulant potential. In vitro assays revealed the ability of the isolates to combat fungal phytopathogens that affect various economically important crops, such as Penicillium digitatum, Alternaria alternata, Botrytis cinerea, Phytophthora capsici, and Fusarium oxysporum. Furthermore, it was determined that diffusible compounds secreted by Trichoderma isolates did not induce the elongation of the primary root of Arabidopsis thaliana in vitro; however, volatile compounds released by certain isolates not only induced this process but also increased the area occupied by the lateral roots of the plant. Based on this screening, five isolates were selected for further analyses: T. longibrachiatum (CP-1), T. breve (HM-1), T. scalesiae (L1-03), T. yunnanense (M4Ar-05), and T. atrobrunneum (M5Ar-03). The strains were evaluated for their ability to promote the growth of A. thaliana under greenhouse conditions and modulate the expression of growth and defense-related genes. All treated plants exhibited increased biomass and leaf area, accompanied by isolate-dependent changes in the expression of genes involved in plant development and immune responses. These results suggest that the selected Trichoderma spp. possess multiple beneficial traits, with valuable agricultural properties, and provide a basis for the development of bioformulations adapted to local production systems.