Characterization of Plant Growth Promoting Rhizobacteria Isolated from the Rhizosphere of Peruvian Highlands Native Crops

Over the past few decades, research in agricultural microbiology has highlighted the efficacy of plant growth promoting rhizobacteria (PGPR) in inducing seedling emergence, promoting the increase in plant height, weight and overall crop yield. A number of microbial isolates have shown promising antagonistic activity against several soilborne pathogens. In this study, twelve bacterial strains were isolated from root rhizosphere of Peruvian native highlands crops, i.e Goldenberry (Physalis peruviana L.), Potato (Solanum tuberosum L.) and Maca (Lepidum meyenii Walp.). The strains were identified using 16S rRNA gene PCR amplification and sequencing and were characterized for their PGPR activities. Among these isolates, all strains were found to be able to produce indol-acetic acid, two strains were able to solubilize hydroxyapatite, bi- and tri-calcium phosphate and the remaining others were able to solubilize at least one source of inorganic phosphate. Of 12 isolates, 10 strains showed antagonistic activity against Fusarium solani, 5 showed activity against Alternaria alternata and 9 inhibited growth of Curvularia lunata. It was also found that out of 12 isolates, three were able to induce tomato seedling emergence by 75% compared to the control in in-vitro assays. 16S rRNA gene sequence based analysis of these strains confirmed that, of 12 strains, 4 were members of genus Pseudomonas, 3 belong to genus Bacillus, 2 were related to genus Rahnella and 1 each belong to the genus Stenotrophomonas, Serratia and Streptomyces.