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, while 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 while 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, or 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 non- treated 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 non-treated controls. A significant negative correlation was observed between percent 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

Biocontrol Potential of Trichoderma Ghanense and Trichoderma Citrinoviride toward Pythium aphanidermatum

“…Their results showed that the cell wall degrading enzyme, endoglucanase, contributed to the antagonistic activity of T. citrinoviride toward pathogens. Moreover, a study by Khadka et al [75] revealed reduced mycelial growth of Rhizoctonia solani by T. ghanense.…”

Novel Trichoderma Isolates Alleviate Water Deficit Stress in Susceptible Tomato Genotypes

“…Herein, we report the evaluation of novel Trichoderma isolates collected from different agroecological regions of Nepal for their ability to proliferate under osmotic stress and then to mitigate stress responses in tomato genotypes during and after exposure to water deficit conditions. We had a unique opportunity to test isolates from highly diverse ecological niches ranging in mean annual precipitation from <200 to 5,000 mm, in elevation above sea level from 58 to 8,848 m, and temperature extremes from –12°C to 43.3°C ( Karki et al, 2016 ; Khadka et al, 2022 ).…”

“…Forty-one different Trichoderma isolates collected from diverse agroecological regions of Nepal (designated as NT1-NT39, NT42, NT43) and two Trichoderma isolates from Ohio (OT41, OT42) were selected for this study. Molecular and morphological characterization of all isolates used in this study is presented in Khadka et al (2022) . Nepalese Trichoderma isolates were recovered from diverse agricultural soils found at environmentally diverse sites (arid, saline, alpine regions), representing potential reservoirs of microorganisms with traits that may benefit plant hosts when grown under differing environmental conditions ( Supplementary Figure 1 and Supplementary Table 1 ).…”