Seleção de fungos endofíticos para o controle biológico de Botrytis cinerea Pers.: Fr em mudas de Eucalyptus benthamii Maiden et Cambage

Abstract

Resumo: Eucalyptus benthamii e uma das principais especies de eucalipto plantadas na regiao sul do Brasil, por sua resistencia a geadas e por seu uso na producao florestal de madeira para fins energeticos. Na producao de mudas, uma das principais doencas ocorrentes em viveiros e o mofo cinzento, causado pelo fungo Botrytis cinerea. Uma das alternativas para o controle dessa doenca e o controle biologico com fungos endofiticos, os quais podem competir com os patogenos na filosfera de mudas de eucalipto. O objetivo deste trabalho foi isolar os fungos endofiticos provenientes de mudas de E. benthamii, identifica-los e, seleciona-los para o controle do B. cinerea. Estes foram isolados do interior de tecidos vegetais desinfectados, provenientes de mudas com three meses de idade coletadas de um viveiro comercial no municipio de Guarapuava-PR e, identificados de acordo com criterios macro e micromorfologicos. Foram isolados 62 fungos endofiticos, sendo 35 de discos foliares e 27 de segmentos de hastes. Nove generos foram identificados: Alternaria sp., Amblyosporium sp., Aspergillus sp., Penicillium sp., Rhizoctonia sp., Trichoderma sp., Pestalotiopsis sp., Phoma sp. e Helminthosporium sp. Para a selecao dos endofiticos com potencial de controle, os testes foram realizados em duas etapas: in vitro e in vivo. Os resultados do primeiro teste, que consistiram no pareamento entre os fungos endofiticos e o patogeno, evidenciaram o potencial antagonista dos fungos Aspergillus sp., Penicillium sp. e Trichoderma sp. Posteriormente, fez-se um teste de eficiencia que consistiu na inoculacao de mudas de E. benthamii com uma suspensao de esporos dos fungos previamente a inoculacao de B. cinerea, comparando sua eficiencia com o fungicida iprodione. As mudas foram incubadas em camara umida a 25 } 1o C, dentro caixas plasticas no interior de uma casa de vegetacao, por 21 dias. Avaliou-se a colonizacao do patogeno na parte aerea da muda com uma escala que variou de 0 (sem sintoma) a 4 (infeccao severa). Houve diferenca significativa entre os tratamentos, sendo que depois do fungicida, o endofito com maior potencial de controle foi o Trichoderma sp., seguido de Aspergillus sp. e Penicillium sp.

Abstract: Eucalyptus benthamii is one of the main species of eucalyptus planted in Southern Brazil, for its resistance to frost and its use in the production of forest wood for energy purposes. During seedling production, a major disease occurring in nurseries is gray mold, caused by the fungus Botrytis cinerea. One of the alternatives to control this disease is biological control with endophytic fungi, which can compete with the pathogens in the phyllosphere of Eucalyptus. The aim of this study was to isolate endophytic fungi from seedlings of E. benthamii, identifying and selecting for control of B. cinerea. These were isolated from the inner tissues of plants disinfected from plants with three months old collected from a commercial nursery in Guarapuava-PR, and identified according to macro and micromorphological criteria. Sixty two endophytic fungi were isolated, 35 from leaf disk and 27 from stem segments. Nine genera were idenified: Alternaria sp., Amblyosporium sp., Aspergillus sp., Penicillium sp., Rhizoctonia sp., Trichoderma sp., Pestalotiopsis sp., Phoma sp. and Helminthosporium sp. For the selection of endophytes with potential control, the tests were performed in two stages: biological control in vitro and in vivo. The results of the first test, which consisted of pairing endophytes and pathogen, showed the potential antagonist of Aspergillus sp., Penicillium sp. and Trichoderma sp. After, a test of efficiency which consisted of inoculation of seedlings of E. benthamii with a spore suspension of fungi prior to inoculation with B. cinerea, was performed to compare their performance with the fungicide iprodione. The seedlings were incubated in a moist chamber at 25 } 1 o C in plastic boxes inside a greenhouse, for 21 days. We evaluated the colonization of the pathogen in the shoots of change with a scale ranging from 0 (no symptoms) to 4 (severe infection). There were significant differences among treatments, and after the fungicide the endophyte with the greatest potential control was Trichoderma sp., followed by Aspergillus sp. and Penicillium sp.t