Investigation of Genetic Diversity and Molecular Identification of IAA Producing Bacteria Using RAPD Marker and 16S rDNA Sequence Analysis

Indole acetic acid is an important hormone that improved the growth of different plant organs such as the root under normal and stress conditions. As various studies have shown, most of rhizobacteria produce indole acetic acid and thereby contribute to the growth of plants. In this study, different rhizobacteria were isolated from different regions of Iran for the assessment of their ability to produce indole acetic acid using the Salkowski method. Then, their genetic diversity was investigated using the RAPD marker. The best indole acetic acid producing Plant Growth Promoting Rhizobacteria (PGPR) was identified using 16S rRNA gene sequencing. The results showed that Ama2 strain was the best rhizobacteria for producing indole acetic acid. Investigation of the genetic diversity indicated that minimum and maximum similarity coefficients between rhizobacteria were zero and 0.53 respectively suggesting the existence of different genera between these rhizobacteria. All rhizobacteria were divided into four groups based on their genetic differences instead of their capability for producing IAA. In other words, strains with different capabilities were placed in the same group because of the existence different genera of rhizobacteria. Based on 16S rRNA gene sequencing, the superior strain belonged to the Pseudomonas genus indicating the importance of this genus for the production of indole acetic acid. The results showed that the RAPD marker and 16S rRNA gene sequencing were capable of studying the genetic diversity and identifying rhizobacteria. Moreover, Ama2 strain can be used as plant growth promoting rhizobacteria with the best capability of IAA production.