Abstract
A new species of endophytic fungi, Trichoderma polyalthiae, was isolated from stems of Polyalthia debilis in Ubon Ratchatani Province, Thailand. Trichoderma polyalthiae was distinguished from closely related species by its molecular and phenotypic characteristics. Based on multigene phylogenetic analyses of the internal transcribed spacer region, translation elongation factor 1-α, and RNA polymerase subunit II gene sequences, T. polyalthiae formed a distinct clade. Morphologically, T. polyalthiae can be distinguished from closely related taxa by its growth rates, diffusing of pigment into agar, and hyaline conidia and production of chlamydospores.