Effects of Bacillus subtilis HS5B5 on Maize Seed Germination and Seedling Growth under NaCl Stress Conditions

Abstract

Salinity is one of the most important factors limiting agricultural productivity. The positive effects of an inoculation with Bacillus subtilis HS5B5 on maize (Zea mays L.) seed germination and seedling growth under saline conditions were elucidated in this study. Maize plants were treated with four NaCl concentrations (0, 100, 200, and 300 mmol·L−1) under hydroponic conditions and the plants inoculated with B. subtilis HS5B5 were compared with the non-inoculated plants in terms of key morphophysiological leaf and root traits. Maize seed germination and seedling growth were inhibited by NaCl stress. The inoculation with B. subtilis HS5B5 significantly increased the germination rate, germination potential, shoot length, and root length under NaCl stress conditions. Moreover, the plant height, biomass, root to shoot weight ratio, above-ground fresh weight, and below-ground fresh weight were higher for the inoculated maize seedlings than for the non-inoculated plants under saline conditions. Additionally, B. subtilis HS5B5 alleviated the salt-induced damage to maize by increasing the chlorophyll content, altering the abundance of osmoregulatory substances, and increasing antioxidant enzyme activities, while decreasing the malondialdehyde content. After the NaCl treatment, the Na+ content in the leaves and roots of maize plants inoculated with B. subtilis HS5B5 decreased significantly, while the K+ content increased. Thus, the inhibitory effect of NaCl stress on maize seed germination and seedling growth was mitigated by B. subtilis HS5B5, suggesting the utility of this microorganism for improving crop cultivation under saline conditions.