Seed Priming with Endophytic Bacillus subtilis Modulates Physiological Responses of Two Different Triticum aestivum L. Cultivars under Drought Stress

Abstract

The protective effects against drought stress of the endophytic bacterium <i>Bacillus subtilis</i> 10-4 were measured by studying the priming response in two wheat (<i>Triticum aestivum</i> L.)-Ekada70 (E70) and Salavat Yulaev (SY)-lines, tolerant and susceptible to drought, respectively. <i>B. subtilis</i> 10-4 improved germination and growth parameters under normal conditions in both cultivars with the most pronounced effect observed in cv. E70. Under drought conditions, <i>B. subtilis</i> 10-4 significantly ameliorated the negative impact of stress on germination and growth of cv. E70, but had no protective effect on cv. SY. <i>B. subtilis</i> 10-4 induced an increase in the levels of photosynthetic chlorophyll (Chl) a, Chl b, and carotenoids (Car) in the leaves of cv. E70, both under normal and drought conditions. In cv. SY plants, bacterial inoculation decreased the contents of Chl a, Chl b, and Car under normal conditions, but pigment content were almost recovered under drought stress. <i>B. subtilis</i> 10-4 increased water holding capacity (WHC) of cv. E70 (but did not affect this parameter in cv. SY) and prevented the stress-induced decline in WHC in both cultivars. Notably, <i>B. subtilis</i> 10-4 increased endogenous salicylic acid (SA) concentration in both cultivars, especially in cv. E70. Moreover, <i>B. subtilis</i> 10-4 reduced drought-induced endogenous SA accumulation, which was correlated with the influence of endophyte on growth, indicating a possible involvement of endogenous SA in the implementation of <i>B. subtilis</i>-mediated effects in both cultivars. Overall, <i>B. subtilis</i> 10-4 inoculation was found to increase drought tolerance in seedlings of both cultivars, as evidenced by decreased lipid peroxidation, proline content, and electrolyte leakage from tissues of wheat seedlings primed with <i>B. subtilis</i> 10-4 under drought conditions.