Plant Growth Promoting Properties of Salt Tolerant Bacteria and Their Application as Microbial Inoculant for Seed Germination

A total of 29 bacterial strains were isolated from salt-affected paddy fields in Khon Kaen province, Thailand. These isolated bacterial strains were evaluated for qualitative parameters such as nitrogen fixation on Ashby's agar, phosphorus (P) and potassium (K) solubilization on NBRIP and Aleksandrov media, respectively under sodium chloride concentrations at electrical conductivity (EC) from 0 to 16 dS m(-1). The resulted showed that most of the isolates were nitrogen fixers and positively promoted the plant growth at saline levels EC 2-8 S m(1). The ability of P and K solubilization, in addition to the production of Indole-3-acetic acid (IAA) varied among bacterial strains and saline concentrations. The highest production of IAA (46.30 mu g mL(-1)) was reported by isolate 18 at EC 8 dS m(-1). The potential antagonism of 26 isolates to plant pathogenic fungi was tested according to dual culture assay. Isolate 1 was the most effective; being able to inhibit more than 50% to Sclerotium rolfsii and 18.93% to Fusarium oxysporum Strains 1, 22, and 29 demonstrated multiple traits of plant growth promoting and were used to test corn (Zea mays) seed germination. It was found that they could activate salt tolerance and germination of corn seeds as efficiently as commercial biofertilizer -effective microorganisms (EM) at salinity level 8 dS m(-1); while previous research reported that corn could not grow well at salinity level higher than 4 dS m(-1). Thus, the selected isolates in this study have the potential concerned be utilized as a bio-remedy for improving plant growth in saline soil.