Abstract
Salinity is one of the most devastating abiotic stresses which hamper the growth and production of rice. Nine indole-3-acetic acid (IAA) producing salt-tolerant-plant growth-promoting rhizobacteria (ST-PGPR) were inoculated into Thai jasmine rice (Oryza sativa L.) variety Khao Dawk Mali 105 (KDML105) seedlings grown under different concentrations of NaCl (0, 50, 100, and 150 mM). ST-PGPR strains significantly promote growth parameters, chlorophyll content, nutrient uptake (N, P, K, Ca, and Mg), antioxidant activity, and proline accumulation in the seedlings under both normal and saline conditions compared to the respective controls. The K + /Na + ratio of the inoculated seedlings was much higher than that of the controls, indicating greater salt tolerance. The highest salt-tolerant and IAA producing strain Sinomonas sp. ORF 15-23, yielded the highest values of all the parameters, particularly at 50 mM NaCl. The percentage increases in these parameters relative to the controls were ranged from > 90% to 306%. Therefore, Sinomonas sp. ORF15-23 was considered a promising ST-PGPR to be developed as bioinoculants for enhancing the growth, salt tolerance, and aroma of the KDML105 rice in salt-affected areas. The environmentally friendly technologies such as ST-PGPR bioinoculants could also support the sustainability of KDML105 geographical indication (GI) products. However, the efficiency of Sinomonas sp. ORF15-23 should be evaluated under field conditions for their effect on rice nutrient uptake and growth, including the 2AP level.