Diversidade de bactérias endofíticas de Digitaria eriantha steud e seu potencial de promoção de crescimento in vitro e in vivo

Abstract

Endophytic bacteria may contribute to promote plant growth, reducing production costs and environmental damage. It is thus importante to prospect plant growth promoting bacteria and their biotechnological potential, furthering sustainable production technologies. The goal was to evaluate pangolão endophytic bacteria community diversity in different environments and test their effect on corn growth promotion. Samples were harvested from colm, leaves, root and soil of the grass at the Araripina Experimental Station, at rainy and dry seasons, with or without liming. The samples were superficially disinfested and used for isolation on the JMV, NFB and JNFB semisolid media. These were used for population estimation and isolation, and later morphophysiological characterization, diversity index evaluation and group representatives were selected to evaluate molecular diversity, in vitro growth promotion characteristics and to test their efficiency on corn. Three hundred and sixteen endophytic native bacteria isolates were isolated and characterized, formin 73 groups at 100% similarity. From these 80 representatives were selected for BOX-PCR fingerprinting of which 67 isolates amplified and were distinct at a 70% similarity level. 16S rRNA sequencing identified at phylum (Proteobacteria, Actynobacteria and Firmicutes) and genera Alcalinogenes, Enterobacter, Erwinia, Massilia, Rhizobium, Mycobacterium, Burkholderia, Bacillus, Neocardoides, Stenotrptophomonas, Kocuria, Shinella, Pantoea, Staphylococcus and Pseudomonas. All presented variable production of indol-3-acetic acid (IAA) with L-tryptophan add, ranging from 20 to 215 μg IAA ml-1 and siderophore production. 68% of the isolates were positive for nitrogen fixation, 35% for phosphate solubilization and 13 for HCN. The isolates promoted height and root length corn development. The isolates did not differ from strains currently recommended for corn inoculant production. Pangolão grass had high endophytic bacteria diversity, which is affected by edaphoclimatic conditions and colonization niche, with the rainy season and limed soils being more diverse.