A hairy discovery: Chaetomiaceae associated with roots of wild Orchidaceae and their potential for the biological control of root diseases

• Ano de defesa: 2024
• Autor(a) principal: Ramos, Danilo Oliveira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa; Fitopatologia
• Palavras-chave em Português: Fungos endofíticos; Biologia - Classificação; Filogenia; Pragas - Controle biológico; Orquídeas; CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA
• Link de acesso: https://locus.ufv.br/handle/123456789/32515; https://doi.org/10.47328/ufvbbt.2024.436

Fungal members of the Chaetomiaceae family can be usually found as endophytes on several plant species, including orchids. Several species of this fungal family have the potential to be used in the biological control of plant diseases. Due to the lack of information about these fungi in association with orchids, this study aimed to isolate and identify the root endophytic Chaetomiaceae that occur in wild Orchidaceae plants, based on morphological and molecular analyses. Furthermore, isolates were tested for their ability to antagonize two soil-borne pathogens, Fusarium sacchari and Rhizoctonia solani. Healthy roots from 12 orchid species were sampled in the cities of Araponga-MG, Conceição do Mato Dentro-Mg, Viçosa-MG, Brasília-DF, Goiânia-GO and Nova Friburgo-RJ. Orchid fungal endophytes were isolated using the indirect isolation and dilution-to-extinction culturing method. Fungal genomic DNA was extracted, and the partial beta-tubulin (tub2) and partial RNA polymerase II second large subunit (rpb2) gene regions were amplified. PCR products were purified and sequenced by Macrogen (South Korea). Maximum Likelihood and Bayesian Inferences were performed for phylogenetic analyses. A total of 45 isolates, from six genera belonging to Chaetomiaceae family were obtained, these being Arcopilus, Chaetomium, Collariella, Dichotomopilus, Humicola and Pseudohumicola. The species Arcopilus amazonicus, A. aureus, and A. cupreus were identified, and four new Arcopilus species were discovered. In the Chaetomium genus five species were identified, C. coarctatum, C. cochliodes, C. globosum, C. pseudocochliodes and C. tenue. A new species of Collariella and Dichotomopilus were identified, and three new species from the genus Humicola were discovered. In addition, Pseudohumicola pulvericola and a new species from this genus were isolated from orchid substrate. A dual culture test was performed to test the ability of 10 endophytic Chaetomiaceae strains to antagonize F. sacchari. Moreover, seven isolates were chosen for the greenhouse experiment with R. solani on common bean (Phaseolus vulgaris). In both biocontrol essays the strain C. tenue (COAD 3736) presented a potential in the control of both pathogens when compared to the other strains tested. This study unraveled the species richness of Chaetomiaceae associated with roots of wild orchids and presented a strain of C. tenue (COAD 3736) with the potential for the biological control of phytopatogenic fungi. Keywords: Taxonomy; phylogeny; biocontrol; endophytes, orchids.