EVALUATION OF THE IAA-PRODUCING ABILITY OF SOME ENDOPHYTIC BACTERIA ISOLATED FROM Panax pseudoginseng ROOTS

Abstract

The objective of this research was to evaluate the Indole-3-acetic acid (IAA) producing ability of isolated endophytic bacteria from Panax pseudoginseng roots through in vitro culture conditions. As a result attained, 16 endophytic bacterial strains, including both gram-positive and gram-negative bacteria were isolated from the collected roots of P. pseudoginseng and all of these isolates could produce IAA with different concentrations, which ranged from 4.61 µg/mL to 85.11 μg/mL, respectively. Among the strains, NN1 and NN6 resulted in the most productive IAA by 85.11 μg/mL and 69.29 μg/mL, respectively. Underlay of NA liquid medium combined with L-tryptophan, 6-day dark incubation with pH 6-8 showed a better synthesis of IAA. While, KNO₃ and (NH₄)₂ HPO₄ were considered the optimal nitrogen sources for IAA production of NN1 (56.36 µg/mL and 55.52 μg/mL) and NN6 (54.17 µg/mL and 42.93 μg/mL, respectively) strains, dextrin and saccharose were the best suitable carbon sources for bacterial isolates NN1 (59.17 μg/mL) and NN6 (67.24 µg/mL). The attained results suggest that the diversity of endophytic bacterial species in P. pseudoginseng roots and their IAA-producing potential are largely based on cultural techniques. Besides, the findings of this study can serve as a foundation for developing natural bioactivity products to improve the productivity of ginsengs.