Screening for P- and K-solubilizing, and siderophore producing capacity of rhizobacteria from Khao Dawk Mali 105 Aromatic Rice

Low nutrient status and high salinity have been identified as significant constraints for KDML105 aromatic rice production in the TKR region, Northeastern, Thailand. The use of PGPR can provides green alternatives to synthetic fertilizer in this region. In this study, therefore, rhizobacteria were isolated from KDML105 rice and evaluated for their potential in P and K solubilization, and siderophore production. The results indicated that 52.0, 21.5, 17.9, and 21.1% of 629 tested isolates, were able to solubilize P, K-mica, K-feldspar, and produce siderophore, respectively. At 0% NaCl the highest amount of solubilized P (35.6 mg L^-1), K (49.5 mg L^-1), and hydroxamate-type siderophore (618.3 μg L^-1), were obtained from isolates ORF4-13, ORF15-23, and CRF16-3, respectively. Under salt stress, the amount of solubilized P of almost all the isolates increased with salt concentration up to 0.5% NaCl and declined thereafter, as compared to the control. In contrast, the amount of solubilized K progressively decreased with NaCl concentration. On the average, ORF15-23 exhibited promising ability in P and K solubilization under salt stress. The promising isolates obtained in this study should be evaluated for their effects on rice nutrients uptake and growth before developing them as biofertilizer.