Endophytic and rhizospheric Trichoderma spp. associated with cucumber plants as potential biocontrol agents of Fusarium oxysporum f. sp. cucumerinum

The diverse roles of Trichoderma spp. in the ecosystem make them valuable resources for sustainable development. This study aimed to identify root endophytic and rhizospheric Trichoderma spp. from cucumber plants based on morphology and molecular data. Molecular identification was based on sequencing the internal transcribed spacer and large subunit rRNA genomic regions. The species identities were determined through a phylogenetic analysis conducted using the Maximum Likelihood method. Additionally, the antifungal ability of the identified Trichoderma spp. against the wilt pathogen Fusarium oxysporum f. sp. cucumerinum was investigated by evaluating their antagonistic activity (using the dual culture method) and antifungal ability (through the application of secondary metabolites). Three fungi isolated from the rhizosphere and inner root tissue were identified as T. atroviride, T. virens, and T. harzianum. Phylogenetic analysis grouped rhizospheric and endophytic isolates of each Trichoderma species in a unique subcluster. Furthermore, endophytic and rhizospheric isolates of each Trichoderma species showed the same antagonistic and antifungal potential against the pathogenic fungus. Trichoderma atroviride and T. virens exhibited the highest antagonistic activity, whereas the secondary metabolites of T. harzianum showed the highest antifungal activity. This study demonstrated that rhizospheric Trichoderma spp. of cucumber agroecological fields can shift from soil saprophytes to root endophytes, which is likely and directly related to the presence of cucumber plants in the soil and the root metabolites released in the rhizosphere. Therefore, our findings and further research on the mechanisms underlying these interactions can provide additional tools for enhancing the productivity and sustainability of agroecosystems.