Diversity of Endophytic Actinomycetes Producing Indole-3-Acetic Acid and in vitro Evaluation of Plant Growth-promoting Activity on Brassica oleracea L.

Abstract

The evaluation of endophytic actinomycetes diversity, growth-promoting strain effects on cauliflower seeds germination, and in vitro organogenesis are the objectives in this study. Moreover, 15 strains from 125 isolates were determined to produce indole-3- acetic acid (IAA), where majority was obtained from roots (66.67%), followed by from branches (26.67%) and leaves (6.67%). Specifically, Jatropha sp. is a plant species with the most endophytic actinomycetes content compared to others. In addition, all endophytic Streptomyces strains were screened based on IAA production ability in vitro on yeast extract–malt extract broth (YMG) broth medium. The results showed the tendency for one strain with code Streptomyces sp. KMR-1E to generate a maximum IAA isolate from Cinnamomun sp. plant. Furthermore, the molecular taxonomy and phylogenetic analysis were recreated from 16S rRNA gene sequences, which attributed the KMR- 1E to genus Streptomyces. Meanwhile, plant growth promotion was evaluated under in vitro condition. This exposed the individual ability to enhance the shoot and root length of cauliflowers. The untreated cultures with a strain free agar block was used as control.

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