Phosphate and potassium-solubilizing bacteria effect on the growth of rice

The objective of this study was to investigate the ability of three phosphate-solubilizing bacteria (PSB), including Pantoea ananatis (KM977993), Rahnella aquatilis (KM977991) and Enterobacter sp. (KM977992), to release potassium (K) from mica and also to evaluate their effect in promoting the growth of rice (cv. ‘Tarom Hashemi’) plants at an early stage of development. These isolates significantly solubilized K from mica in both solid and liquid medium in vitro. After 25 days of growth in liquid AM medium, K-solubilization (KS) for P. ananatis, Enterobacter sp. and R. aqautillis was 38.9, 33.6 and 15.5 μg ml−1, respectively. KS of the isolates increased as pH of the culture medium declined (r = −0.83, P < 0.0053), as a result of organic acid production. Single KSB inoculations increased plant height (PlHe), stem diameter (SD), root length (RL), leaf area (LA) and biomass dry weight (BDW) by 4.09–10.8%, 4.07–10.4%, 8.0–13.1%, 19.8–21.4% and 7.53–15.7%, respectively, in a pot experiment while PlHe, BDW, SPAD value, K uptake in the leaves, stem, and root of rice seedling also increased by 10.8–15.1%, 27.4–65.3%, 8.64–12.0%, 38.5–76.9%, 17.6–52.9% and 25.0–75.0%, respectively, in a field experiment, when compared to the control. The results of both experiments indicate that the values of all measured parameters were higher when rice seedlings were inoculated with P. ananatis than withEnterobacter sp. and R.aquatilis. Based on our results, these isolates can be used as both PSB and KSB to enhance rice growth and also can be worthy of commercial development.