Plant Growth-Promoting Rhizobacteria Enhance Salt Tolerance in Oat by Upregulating the Antioxidant System and Promoting Root Growth

Oat (Avena sativa L.) is an important crop for animal husbandry, but its planting is restricted due to the lack of salt-tolerant varieties. The present study aimed to examine the effect of the strains Paenibacillus peoriae LrM1, Bacillus sp.LrM2, and Acinetobacter calcoaceticus P19 on oxidative stress and growth parameters in oats under salt-stress conditions. The results showed that NaCl significantly decreased the amount of indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase produced by LrM1, causing LrM2 and P19 to not produce IAA, LrM2 increased the amount of ACC deaminase under salt stress caused by 100 mM NaCl (P < 0.05). Further, all three strains decreased O-2(-) generation. LrM2 inoculation could inhibit the accumulation of H2O2 and Malondialdehyde. The activities of catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase were enhanced, and the levels of the non-enzymatic antioxidants, ascorbate and glutathione, and the ascorbate/dehydroascorbate ratio were increased as well (P < 0.05). LrM2 had a positive effect on shoot growth, root system architecture, and relative water content under 100 mM NaCl stress conditions. Compared with LrM2, the other two strains had no significant growth promotion effect on oat. P19 only exhibited a significant growth promotion effect on oat under no stress, whereas LrM1 showed no significant growth promotion effect on oat under any conditions. In conclusion, the inoculation of strains isolated from saline soils promotes plant growth, which may be a promising strategy to improve salt-resistance in plants. [GRAPHICS] .

Automated summary

This study found that the inoculation of strains isolated from saline soils promotes plant growth and alleviates oxidative stress caused by salt-stress in oats. Among the strains tested, LrM2 showed the best growth-promoting effect under salt stress conditions.