Bioprospecting of endophytic bacteria (Bacillus spp.) from passionfruit (Passiflora edulis Sims f. flavicarpa) for plant growth promotion

Abstract

Endophytic bacteria has been reported as plant growth promoters in various cultivated and uncultivated plants. Thus, the objective onf this study was to evaluate the potential of 21 endophytic bacterial isolated from leaves of passionfruit plants (Passiflora edulis Sims f. flavicarpa). In vitro antagonism, indole-3-acetic acid (IAA) production, gibberellins, cytokines and phosphate solubilization were also tested. In vitro antagonism was investigated using volatile metabolites detection by means of the overlapping dishes technique and direct confrontation. The production of IAA was evaluated by means of the colorimetric method with the absorbance reading of the optical density at O.D. (550nm). The phosphate solubilization was measured in a qualitative method by reading the solubilization halo diameter and the quantitative evaluation in liquid medium and reading of O.D. (450 nm). All bacterial isolates were able to inhibit the growth of Phytophthora sp. in both methods with values ranging from 50% to >90% inhibition (Skott-Knott, p ≤0 0.05). All the tested endophytic bacteria were also able to produce plant hormones. The phosphate solubilization was more than mean of the liquid medium. Thus, the studied endophytic bacterial isolates are suggested as potential plant growth promoters.