Pochonia chlamydosporia no manejo de rizoctoniose

Abstract

The Rhizoctonia solani fungus is a soil-borne pathogen that causes damping off in pre and post-emergence seedling to numerous hosts. Biological control is an alternative method that could be used to manage this disease. The objectives of this study were to evaluate, in vitro, the antagonistic action and volatile metabolites of Pochonia chlamydosporia isolates and the potential of these P. chlamydosporia isolates in the damping off beet seedlings management caused by R. solani. In this regard, firstly were performed tests, in vitro, using ten isolates of P. chlamydosporia against the fungus R. solani through confrontation test and the evaluation of volatile metabolites effect on pathogen mycelial growth. These studies were conducted in a completely randomized design by 10 and 5 replications per treatment, respectively, repeated twice. In the confrontation test the Pc 1, Pc 5, Pc 7, Pc 8, Pc 9 and Pc 10 P. chlamydosporia isolates reduced significantly the R. solani pathogen mycelial growth comparing with the control treatment. In the volatile metabolites test, only at the firts assay, the isolated Pc 1 and Pc 2 differ from the control treatment reducing 22.67% the pathogen mycelial growth. Also two, in vivo, experiments were conducted in the greenhouse. Initially, to assembly this study was placed separately in black plastic bags 3 kg of soil, 10 g/kg of inoculum pathogen soil, previously grown in rice substrate and moistened until field capacity. Then this mixture was homogenized and stored in a greenhouse at ± 24°C. After 7 days added 30 g/kg of soil each bag the respective isolates inoculum of P. chlamydosporia (30g/kg of soil), it was homogenized and stored for another 7 days in a greenhouse. The antagonist was not added in the control treatment. After this period, the soil in each bag was placed, separately, in 300 g polypropylene pot and sown 10 beet seeds/pot. Each treatment consisted by 10 replications. After the first beet seedlings emergence, the number of emerged and damped off beet seedlings was evaluated for 21 consecutive days. In the fisrt test, none P. chlamydosporia isolates control the seedlings damping off caused by R. solani, comparing with the control treatment. In the second test, until the 14 days, except the Pc 3, Pc 4 and Pc 10 isolates, all other isolates reduce the damping off beet seedlings number compared with the control treatment.