Diazotrophic bacteria associated to sugarcane varieties cropped at Northeast Region of Brazil

Abstract

The objective of this work was to study the diversity of diazotrophic bacteria associated to 10 varieties of sugarcane cultivated in two states of the Northeast of Brazil and to identify the isolates by morphological and molecular methods. Diversity was studied by the application of traditional growth-depending microbiological methods: Gram-staining, comparison of colony morphology and growth on several culture media. Phylogenetic taxonomy was performed using 16S rRNA gene sequencing data. Almost all isolates obtained in semi-solid nitrogen free media were classified as Gram-negative and seven colony morphological groups were distinguished after growth on Potato medium. Among the 10 varieties evaluated, RB72454 resulted in higher number of isolates and diversity. The great majority of isolates from most of the genotypes tested showed similar characteristic to the genus Gluconacetobacter based on its peculiar colony morphology and growth characteristics in semi-solid media. Comparison of the 16S rRNA sequence of each isolate to the Genbank showed that they are closely related to Gluconacetobacter, Burkholderia, Kosakonia, Klebsiella and Stenotrophomonas.