Streptomyces sp. strain PGPA39 alleviates salt stress and promotes growth of 'Micro Tom' tomato plants.

AIMS: To identify an actinobacterial strain that can promote growth and alleviate salinity stress in tomato plants. METHODS AND
RESULTS: Actinobacteria were isolated from agricultural soil and screened for ACC deaminase activity, production of indole acetic acid (IAA), solubilization of tricalcium phosphate and sodium chloride (NaCl) salinity tolerance. Among the several strains tested, one strain designated PGPA39 exhibited higher IAA production, and phosphate solubilization in addition to ACC deaminase activity, and tolerance to 1 mol l(-1) NaCl. Strain PGPA39 was identified as a Streptomyces strain based on 16S rDNA sequence and designated Streptomyces sp. strain PGPA39. It promoted the growth of Arabidopsis seedlings in vitro as evidenced by a significant increase in plant biomass and number of lateral roots. Salinity stress-alleviating activity of PGPA39 was evaluated using 'Micro Tom' tomato plants with 180 mmol l(-1) NaCl stress under gnotobiotic condition. A significant increase in plant biomass and chlorophyll content and a reduction in leaf proline content were observed in PGPA39-inoculated tomato plants under salt stress compared with control and salt-stressed noninoculated plants.
CONCLUSIONS: Streptomyces sp. strain PGPA39 alleviated salt stress and promoted the growth of tomato plants. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows the potential of Streptomyces sp. strain PGPA39 in alleviating salinity stress in tomato plants and could be utilized for stress alleviation in crop plants under field conditions.