Avaliação antagônica in vitro e in vivo de Trichoderma spp. a Rhizopus stolonifer em maracujazeiro amarelo

Portuguese. Para estudar a potencialidade antagônica de espécies de Trichoderma spp. in vitro e in vivo a Rhizopus stolonifer, patógeno causador da podridão floral do maracujazeiro, foram estudadas as espécies de Trichoderma viride, T. virens, T. harzianum e T. stromaticum. O crescimento micelial do fitopatógeno foi realizado pelo teste do pareamento de culturas, para crescimento individual foram utilizadas cinco temperaturas. Avaliou-se também o crescimento micelial em 24h e 48h, avaliando a taxa de crescimento dos isolados. Na produção de metabolitos voláteis e não voláteis foram utilizados papel celofane e sobreposição de placas. Em condição de campo os frutos/planta foram tratados com a suspensão na concentração de 2 x 10(8) Conídios/mL sendo avaliado o número médio de frutos aos 15 e 30. No pareamento de cultura todos os isolados de Trichoderma spp. apresentaram crescimento micelial, impedindo o desenvolvimento do fitopatógeno, para todos os isolados as temperaturas ideais de crescimento foram de 25ºC e 30ºC. Nos períodos de incubação de 24 e 48h, foram constatadas diferenças significativas no crescimento micelial entre os isolados os antagonistas apresentaram velocidade de crescimento maior que o fitopatógeno. Houve uma produção de metabólitos voláteis e não voláteis de ação antifúngica ao R. stolonifer. No ensaio em campo houve diferença significativa entre os tratamentos, verificando-se que o melhor resultado entre os antagonistas em estudo cujos percentuais de pegamento foram 74% para os tratamentos Trichoderma harzianum e T. virens, e os tratamentos T. viride e T. stromaticum obtiveram um porcentual de 75% enquanto a testemunha obteve um percentual de 42%.

English. Floral rot of passion fruit is caused by the fungus Rhizopus stolonifer, which attacks newly open flowers and young little fruits. The infection starts in the inner parts of the flower buds where it causes water-soaked lesions, whose floral tissues acquire a dark-brown coloration. The presence of dark mycelium and fungus fructification is often noticed on the lesions. The present work aimed at studying the in vitro and in vivo antagonistic potentiality of species of Trichoderma spp. to Rhizopus stolonifer. In order to assess the antagonistic efficiency of biological control agents in the floral rot of yellow passion fruit, in vitro and in vivo tests were carried out with these species: Trichoderma viride, T. virens, T. harzianum and T. stromaticum, at the Biofactory of the State University of Southwestern Bahia (Universidade Estadual do Sudoeste da Bahia), campus of Vitória da Conquista - BA, and at a farm in the municipality of Eunápolis - BA. In the in vitro tests the mycelial growths of the phytopathogen and antagonists at the temperatures of 10ºC, 15ºC, 20ºC, 25ºC and 30ºC were evaluated as well as the mycelial growth within 24h and 48h, in order to verify the growth rate of the isolates. To inhibit the mycelial growth of the phytopathogen, the pairing of cultures was carried out to assess the potentiality of antagonists and the production of volatile and non-volatile metabolites. Field, the antagonists were assessed according to their capacity. In the of preventing the infection by Rhizopus stolonifer, the average number of effective fruits being evaluated on the 15th and 30th day after the application of antagonists. Through the obtained results, it was noticed that the best temperatures for the growth of antagonists and phytopathogen were at 25ºC and 30ºC for all isolates. During the incubation periods of 24 and 48h, significant differences in the mycelial growth were evidenced among isolates of Trichoderma spp. In relation to R. stolonifer, the antagonists demonstrated growth speed significantly higher than the phytopathogen. In paired culture, all the isolates of Trichoderma spp. showed fast mycelial growth, thus preventing the development of the phytopathogen, demonstrating antagonism in the production of volatile and non volatile metabolites with fungal action against R. stolonifer. In the field test, there was significant effect in the treatments, a higher fruit set of 74% was noted for the treatments T3 - Trichoderma harzianum and T5 - T. virens, and 75% for. The treatments T2 - T. viride and T4 - T. stromaticum the control obtained a lower percentage 42%.