Rizobactérias no controle do nematoide cavernícola e na promoção de crescimento de bananeira

Abstract

There are several ways to control Radopholus similis in banana trees, by using nematicides, culture rotations and resistant varieties. Due to economical and environmental obstacles, alternative measures have been studied, such as the usage of rhizobacteria in the biological control. The aim of this study is was to isolate and evaluate rhizobacteria from nematicide plants to control the nematode Radopholus similis and to promote the growth of micropropagated banana plantlets. Seventy-seven bacterial isolates were obtained from rhizospheric soil of Crotalaria juncea e Tagetes patula L., and their metabolites were evaluated, under in vitro conditions, for toxic effect on those nematodes after 24 and 36 hours treatment. Thirty three percent of the rhizobacteria showed nematocidal effect to R. similis, with 56,6% to 100% variation on mortality due to the exposure to rhizobacteria metabolites during the period of time evaluated. Five rhizobactera isolates (3 TSA-CD, 4 TSA-CD, 6 TSA-CD, 7 TSA-CD e 17 KB-CR) were considered the most promising biocontrol agents due to their nematocidal effect in both period of time. And they were selected for in vivo studies. However, despite their in vitro effect, the in vivo biocontrol trails did not show good results. It was observed high infestation of juvenile females of the nematodes in roots of tissue cultured banana plantlets, in comparison with the nematode found in the soil. Regarding to the plantlet growth promoting index, it was observed a significant response in the treatments with rhizobacteria in absence of R. similis.