The Pursuit in Nepal of Native Trichoderma spp. for Plant Disease Biocontrol

Abstract

The characteristics of 41 native Trichoderma isolates collected from diverse microclimatic domains in Nepal and two Ohio isolates and their efficacy in biocontrol of plant diseases were assessed. Species assignment was based on a maximum likelihood phylogenetic analysis constructed on a concatenated dataset using the internal transcribed spacer region ( ITS), translocation elongation factor ( tef1), and RNA polymerase II subunit ( rpb2). Most of the Nepal isolates ( n = 37) were assigned to the Viride clade and identified as T. asperellum or T. asperelloides, whereas a minority ( n = 4) were assigned to the Harzianum clade and identified as T. lixii or T. rugulosum. One of the Ohio isolates belonged to the Hamatum clade and was closely related to the T. hamatum reference strain, whereas the other Ohio strain was closely related to T. ghanense (Longibrachiatum clade). Confrontation assays conducted to evaluate mycelial growth reduction of Rhizoctonia solani indicated that mechanisms of action included competition, mycoparasitism, and antibiosis. Trichoderma asperellum isolates NT22, NT8, NT24, and NT25 and T. asperelloides isolates NT1 and NT30 reduced Rhizoctonia root rot severity in greenhouse assays by more than 50% compared with the nontreated controls. Trichoderma asperellum isolates NT4, NT25, NT28, and NT17 and T. asperelloides NT8 suppressed clubroot severity in greenhouse assays by more than 75% compared with the nontreated controls. A significant negative correlation was observed between the percentage of mycelial growth reduction in vitro (confrontation assay) of R. solani and root rot severity. This study provides a basis for additional investigations of Trichoderma diversity and biocontrol potential in Nepal. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .