Actinomicetos promotores de crescimento e agentes de biocontrole do nematoide cavernícola da bananeira Radopholus similis

Abstract

The objectives of this study were: to quantify the population of total bacteria and actinomycetes in the rhizosphere and roots of banana plants cv FHIA 18; to characterize the actinomycete for their ability to production extracellular enzymes; to evaluate the potential of these actinomycetes for growth promotion of banana plants cv. William, and to evaluate the effect of secondary metabolites produced by these microorganisms in the mortality of Radopholus similis. The population densities of total bacteria were higher than those of actinomycetes, and did not present significantly differences in rhizosphere soil as compared to their populations in roots of banana plants. The physiological characterization showed that 63.0%, 43.5% and 6.5% presented celulolitic, xylanolytic, and chitinolytic activity, respective. For growth promotion of banana plants, on both experiments, significant increments in plant dry matter production were observed, which depends on the actinomycete isolate tested. In the first experiment,significant increments of as higt as 46.2% were observed for plant height, 65.5% for plant stem diameter, 283.6% for plant aeriel parts dry matter production, and 447.5% root dry matter. In the SECOND EXPERIMENT, with different actinomycetes, increments of up to 109,1% and 81,4% were obtained for plant height and stem diameter, respectively. For root and aerial parts dry mattes production, an increase of up to1823% and161,6%, respectively, was also observed. The in vitro biocontrol of the nematode R. similis, by actinomycetes isolates was demonstrated in this work. . The isolates AC12, Ac30, AC33, AC51, AC52, AC25, AC36 and AC39 caused 50% immobility of R. similis. The most efficient isolates were AC39, AC52, AC30, AC33, AC12, AC51 and AC25 AC36, which caused, respectively, a mortality of 100%, 80%, 72%, 66.7%, 61.3%, 53.35, 52% and 50.7 of R. similes.