The double life of an insect pathogen: Metarhizium as a plant symbiont and its genetic diversity in coffee agroecosystems
Data
2016-02-26
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Editor
Universidade Federal de Viçosa
Resumo
O gênero Metarhizium é amplamente conhecido por sua capacidade entomopatogênica. No entanto, recentemente também foi reconhecido como simbionte de planta, capaz de transferir nitrogênio de cadáveres de insetos para plantas, atuar como antagonista de fitopatógenos e promover o crescimento vegetal. Essas funções podem ser consideradas como serviços de ecossistema que podem ser fornecidos por esses fungos para plantas em sistemas de cultivos sustentáveis. Todavia, esses fungos são pouco considerados no contexto ecológico e dados sobre sua diversidade em solos agrícolas e na rizosfera são muito escassos, especialmente em ecossistemas tropicais. Além disso, nenhum método molecular para detectar e quantificar especificamente Metarhizium em associação com sistema radicular está disponível. Dessa forma, nesta tese nós focamos no estabelecimento de um método para detectar e quantificar Metarhizium em raízes de plantas e na investigação de sua diversidade em cultivos de café agroflorestal e pleno sol. Nós estabelecemos um método baseado na reação em cadeia da polimerase em tempo real (qPCR) confiável e reprodutível para detectar e quantificar Metarhizium em raízes de plantas. Tal método foi verificado por meio de detecção via método dependente de cultivo e microscopia confocal. Considerando a diversidade de Metarhizium em solos agroflorestais e pleno sol, nós encontramos três espécies, sendo que M. robertsii foi a espécie mais frequente em ambos sistemas. Ao comparar a diversidade entre os sistemas agroflorestais e pleno sol, duas das três agroflorestas amostradas apresentaram maior diversidade de Metarhizium e a diversidade total, considerando as seis áreas, também foi maior nas agroflorestas. A população de M. robertsii foi dividida em três diferentes clados, porém nenhum padrão de distribuição ou recombinação foi observado em relação aos mesmos. Com a relação à diversidade de Metarhizium na rizosfera, M. robertsii também foi a espécie mais abundante, sendo encontrada em todos os grupos de plantas amostrados. Metarhizium pemphigi foi a mais frequente na rizosfera de plantas de café, indicando a possibilidade de sua especialização ecológica em relação às raízes de café. Nós fornecemos resultados importantes sobre a associação de Metarhizium no solo e em associação com plantas, incluindo: (i) um método de laboratório pra estudar associação Metarhizium-raiz, (ii) a diversidade de Metarhizium no solo em dois sistemas de cultivo e (iii) a diversidade de Metarhizium na rizosfera de plantas presentes em sistema de cultivo diversificado.
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.
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.
Descrição
Tese de Doutorado defendida na Universidade Federal de Viçosa.
Palavras-chave
Fungos entomopatogênicos, Metarhizium anisopliae, Biologia molecular, Simbiose, Genética de populações, Café - Raízes, Café - Raízes
Citação
MOREIRA, C. C. The double life of an insect pathogen: Metarhizium as a plant symbiont and its genetic diversity in coffee agroecosystems. 2016. 118 f. Tese (Doutorado em Entomologia) - Universidade Federal de Viçosa, Viçosa-MG. 2016.