Diversidade de bactérias endofíticas em bananeira 'Prata-Anã'

Abstract

Banana (Musa spp.) is one of the most cultivated fruit trees in the country. That culture, as well as other plants, is associated with microorganisms that can benefit them. Among these microorganisms, are the endophytic bacteria, which inhabit the interior of plant tissues and organs without causing damage to their host and without producing external structures emerging from plant tissues. The diversity of endophytes microorganisms has been evaluated in many plants, but in bananas little is known about this relationship. The objectives of this study were to access the genetic diversity and identify at the species level endophytic bacteria present in roots of 'Prata-Ana' banana, through the use of molecular markers. The study was carried out in the laboratory of Plant Pathology and Biotechnology Campus Janaúba Universidade Estadual de Montes Claros. Fragments of roots of 'Prata-Ana' banana from four municipalities in the north of Minas Gerais and Bahia were used. It was accomplished a root desifestation in order to isolate the endophytic bacteria. The bacterial isolates were characterized as for the response of Gram, and pathogenicity was tested by the hypersensitivity reaction in non-host plants, being used red pepper, common beans and tobacco plants. The genetic diversity was verified using the ARDRA and rep-PCR techniques. Isolates were selected by the presence of the nifh gene. The identification at the genus and species levels was performed by partial sequencing of 16S rDNA. They were isolated 201 endophytic bacteria, of these 151 were classified as Gram positive and 50 as Gram negative. None showed hypersensitivity reaction in the tested plants. The rep-PCR technique generated for each primer: REP, ERIC and BOX, separately, different molecular profiles. We obtained a total of 50 readable loci, and all fragments were shown to be polymorphic. The diversity analysis of isolates by ARDRA technique, obtained through cleavage products with four restriction enzymes, produced 45 polymorphic bands and no monomorphic. The Rsal was the enzyme which presented the highest discriminatory power, generating 13 different bands, followed by Mspl with 12, Hinfl with 11 bands and Ndel with 9 bands. Theamplification of the nifl gene by PCR was detected in 40 isolates. After the sequencing of the 16S rDNA region from 201 bacterial isolates, were obtained 143 sequences with good quality. The sequence analysis revealed that the isolates are distributed among 17 bacterial genera: Bacillus, Agrobacterium, Klebsiella, Paenibacillus, Lysinibacillus, Streptomyces, Artrobacter, Micrococus, Rhizobium, Sporolactobacillus, Acetobacter, Aneurinibacillus, Pantoea, Brevibacillus, Stenotrophomonas, Pseudomonas and Enterobacter, which include 16 different species. The genus Bacillus showed the greatest number of isolate species. The bacteria identified in this study have potential for providing growth, phosphate solubilization, biological control and nitrogen fixation.