Bioproduction of indole acetic acid by endophytic bacteria of Bacillus strains isolated from chili (Capsicum annuum L.) and its potential for supporting the chili seedlings

Abstract

Endophytic bacteria live and colonize the plant interior without causing disease symptoms. Interaction between endophytic bacteria and host plant was commonly assessed in nitrogen fixation, phosphate solubilizing, indole-3-acetic acid (IAA) and siderophore production. The present study collected a total of fifteen endophytic bacteria isolated from fruits, leaves, roots, and stems of Chili (Capsicum annum L.). Aiming to study their potential for IAA production, three isolates Cb 6, Cb 8 and Cb 11 were selected and were identified as Bacillus strain. The highest IAA production (1.37 µg/ml) showed by the isolate Bacillus subtilis Cb 11 in.medium NB supplemented with L-tryptophan. The cultures condition was optimized using various pH and tryptophan concentrations to maximize the IAA production. Among the three isolates, the maximum IAA production was observed at pH 6-7 and L-tryptophan concentration at 2.0-2.5 mM. The capability of the Bacillus strains to support the growth of Chili seedlings were assayed by soaking the seedlings in the Bacillus culture. The Bacillus culture was inoculated to the seedlings 2 weeks after planting. The assay showed that the inoculation of B. subtilis B 11 to Chili seedlings increased the length of the shoot (19.75 cm) and root (15.47 cm), respectively. The present study indicates the potential endophytic bacteria to produce IAA and support Chili seedlings’ growth.