The double life of an insect pathogen: Metarhizium as a plant symbiont and its genetic diversity in coffee agroecosystems

• Ano de defesa: 2016
• Autor(a) principal: Moreira, Camila Costa
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Fungos entomopatogênicos; Metarhizium anisopliae; Biologia molecular; Simbiose; Genética de populações; Café - Raízes; Entomologia Agrícola
• Link de acesso: http://www.locus.ufv.br/handle/123456789/8304

The Metarhizium genus is widely recognized for its entomopathogenic capacity, but more recently was recognized as a plant symbiont, being able to transfer nitrogen from insect cadavers to plants, act as plant pathogen antagonist and plant growth promoter. All those functions could be valuable as ecosystem services provided by these fungi to plants in sustainable agricultural schemes. However, these fungi are poorly considered in an ecological context and data about their diversity and abundance in agricultural soils and in association with plant rhizosphere are very sparse, especially in tropical ecosystems. Also, considering the ability to form mutualistic association with plants, no Metarhizium’s specific molecular method is available to detect and quantify association in plant root systems. Given this, in this thesis we focused in the establishment of a method to detect and quantify Metarhizium in plant roots and investigate its diversity in coffee based agroforestry and full sun systems. In doing so, we aimed to provide a better understanding of Metarhizium ́s association with plants, to get a better insight of how its inter- and intraspecific diversity is distributed in soils of coffee agroforestry and full sun soils and to understand how Metarhizium species are distributed in the rhizosphere of coffee plants and non-crop plants in a coffee agroforestry system. We established a reliable and reproducible real-time polymerase chain reaction (qPCR) method to quantify and detect Metarhizium in plant roots and also detect the association through cultivation methods and confocal microscopy. In the surveys from the diversity of Metarhizium in soils from agroforestry and full sun coffee systems, we found three Metarhizium species, M. robertsii being the most prevalent of these. Comparing the diversity between agroforestry and full-sun systems we found higher diversity in agroforestry systems in two of the three sampled fields, and overall diversity was also higher in agroforestry. The M. robertsii population exhibited presented three clades and no specific distribution pattern and recombination was observed in the clades. Regarding Metarhizium diversity in the rhizosphere, M. robertsii was also the most abundant species and was present in all groups of surveyed plants, M. pemphigi presented the highest levels in the coffee rhizosphere indicating a possible ecological specialization of this species to coffee roots. We provided important findings regarding the association of the insect pathogen Metarhizium when in association with plants, including: (i) a laboratory method to study the Metarhizium-plant association, (ii) the diversity of Metarhizium in soil and its comparison between agricultural systems and (iii) the Metarhizium diversity in the rhizosphere of crop and non-crop plants in a biodiverse agroecosystem.