Diversity of <i>Trichoderma</i> in the unexplored Bolivian Amazon region and their potential for coffee diseases control

Trichoderma fungi are colonizers of plant substrates and rhizosphere and are valued for their antagonism against phytopathogens and ability to promote plant health. We investigated Trichoderma diversity in coffee-growing soils in Caranavi region of Yungas-La Paz, Bolivia, where high humidity and fungal diseases threaten yield, and evaluated their potential as biocontrol agents against coffee pathogens. A total of 440 Trichoderma were isolated from coffee rhizosphere, fallow lands, and forest ecosystems across an altitudinal gradient in Caranavi. DNA barcode analyses using ITS, rpb2, and tef1 loci identified only four species. However, 47 taxa comprising 344 isolates were ambiguous, and 41 isolates were previously unrecognised species. The diversity of Trichoderma spp. was significantly affected by ecosystem type and altitude, with more species isolated from coffee rhizosphere than fallow lands and forest ecosystems, and from lower altitudes than higher ones. Evaluation of 100 isolates against a native coffee wilt pathogen Fusarium oxysporum identified 70 potent antagonists, with 30 achieving 90-100% disease control. This is the first comprehensive study of Trichoderma diversity in Yungas, identifying indigenous Trichoderma for biocontrol applications against coffee diseases. It also emphasizes the need to refine the Trichoderma species concept and improve the taxonomic resolution within the genus.