Abstract

The objective of the study was to characterize culturable diazotrophic endophytic bacteria from ‘Champaka’ pineapple plants during the fruiting period in an organic system. Micropropagated plants were inoculated with the diazotrophic endophytic bacterium, strain AB 219a, during acclimatization phase. In the field, the plants were fertilized with different dosages and sources of organic compost. After 17 months of field cultivation, roots and stems were collected for the isolation of endophytes, DNA extraction, 16S rDNA amplification and molecular analysis. A total of nine bacterial groups were identified, and species Burkholderia silvatlantica, Azorhizobium caulinodans, Pantoea eucrina, Erwinia sp. and unculturable bacterium occurred in inoculated plants. In contrast, non-inoculated plants were associated endophytes related to Burkholderia cenocepacia,Azospirillum brasilense, Enterobacter oryzae, Erwinia sp. and Sphingobium yanoikuyae. Segments of 360 base pair from nifH gene were amplified from representative endophytes within identified species, except from the Pantoea eucrina strain AB 295. 16S rDNA phylogenetic analysis of endophytes isolated from inoculated plants revealed distinct families: Xanthobacteraceae, Burkholderiaceae and Enterobacteriaceae; and from non-inoculated plants, Rodospirillaceae and Sphingomonadaceae families were also identified. The ‘Champaka’ pineapple plants at fruiting stage associate with endophytes related to α, β and γ Proteobacteria, after plantlets inoculation or not with the diazotrophic bacterium Burkholderia silvatlantica (AB 219a). Most of those endophytes present nifH gene, a characteristic for nitrogen-fixing bacteria.

Key words: Biodiversity, nitrogen-fixing bacteria, Ananas comosus, microbial ecology.