Biochemical characterization of systemic bacteria in bananas, sensitivity to antibiotics and plant phytotoxicity during shoot proliferation/Caracterizacao bioquimica de bacterias sistemicas em bananeiras, sensibilidade a antibioticos e fitotoxicidade de plantas durante a proliferacao de brotos

The objective of this work was to characterize the biochemically systemic bacterial isolated from banana plants, to evaluate the bacterial sensitivity to antibiotics, and to determine the phytotoxicity of banana shoots during in vitro proliferation. Systemic bacteria belonging to the Klebsiella and Aeromonas genera were isolated from the "Maravilha" (FHIA 01 AAAB), "Preciosa" (PV 4285 AAAB) and "Thap Maeo" (AAB) varieties and were then characterized. Tests of shoot sensitivity to antibiotics were performed, and the minimum inhibitory concentration (MIC) and phytotoxic effects of selected antibiotics to plants were determined. Among the 20 antibiotics evaluated, the strains showed sensitivity to cefaclor, cefalexin, cefalotin, nalidixic acid, chloramphenicol, and vancomycin. However, during MIC determination, the best results were obtained with cefaclor, vancomycin or nalidixic acid alone in concentrations ranging from 512 to 1,024 mg [L.sup.-1]. In culture medium, cefaclor at 1,024 mg [L.sup.-1] was the only antibiotic to affect the multiplication and the shoot survival in culture. Keywords: Musa spp., micropropagation, contamination, endophytic microorganisms, antimicrobial control. O objetivo do trabalho foi caracterizar bioquimicamente bacterias sistemicas isoladas de plantas de bananeiras, avaliar a sensibilidade das bacterias a antibioticos e determinar a fitotoxicidade de brotos de bananeiras durante a proliferacao in vitro. Bacterias sistemicas pertencentes aos generos Klebsiella e Aeromonas foram isoladas a partir das variedades "Maravilha" (FHIA 01 AAAB), "Preciosa" (PV 4285 AAAB) e "Thap Maeo" (AAB), sendo em seguida caracterizadas. Testes de sensibilidade das brotacoes aos antibioticos foram desenvolvidos e a minima concentracao inibitoria (MIC) e os efeitos fitotoxicos dos antibioticos selecionados em relacao aos brotos foram determinados. Entre os 20 antibioticos avaliados, verificou-se que as bacterias mostraram sensibilidade para o cefaclor, cefalexina, cefalotina, acido nalidixico, cloranfenicol e vancomicina. Entretanto, durante a determinacao da MIC os melhores resultados foram obtidos com cefaclor, vancomicina e acido nalidixico em concentracoes entre 512 a 1.024 mg [L.sup.-1]. Em meio de cultura, o cefaclor na concentracao de 1.024 mg [L.sup.-1] foi o unico a afetar a multiplicacao e a sobrevivencia de brotos em cultivo. Palavras-chave: Musa spp., micropropagacao, contaminacao, microrganismos endofiticos, controle microbiano.