Non-pathogenic Staphylococcus strains augmented the maize growth through oxidative stress management and nutrient supply under induced salt stress

The present study was conducted to elucidate the role of phytobeneficial bacteria to control the cellular oxidative damage in maize (Zea mays L.) plants caused by salinity. Bacteria were isolated from the rhizosphere of kallar grass (Leptochloa fusca L.) through serial dilution method and taxonomically identified on the basis of their 16S ribosomal RNA gene sequencing. In vitro phosphate solubilization, indole-3-acetic acid (IAA) synthesis, and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity were evaluated by solubilization index measurement, colorimetric method, and turbidity assay, respectively. In the pot experiment, the impact of single and mixed inoculation of these strains at four levels (0, 50, 100, and 200 mM) of salt stress was evaluated in terms of growth and physiological response of maize plants to salinity. The bacterial strains (STN-1, STN-5, and STN-14) were taxonomically classified as Staphylococcus spp. At 5% NaCl level, the strains demonstrated substantial potential for phosphate solubilization, ACC deaminase activity, and IAA production both with and without tryptophan. The inoculation of strains STN-1, STN-5, and mixed inoculation resulted in substantial growth improvement of maize plants along with increased antioxidant enzyme activity and decreased levels of reactive oxygen species. In addition, single inoculation of STN-1 and STN-5 along with mixed inoculation augmented the uptake of N, P, K, and Ca+2 and reduced Na+ uptake. Current results demonstrated that the strains STN-1 and STN-5 modulated stress-responsive mechanisms and regulated ion balance in induced salinity to promote maize growth.