The endophyte Stenotrophomonas maltophilia EPS modulates endogenous antioxidant defense in safflower (Carthamus tinctorius L.) under cadmium stress

Cadmium (Cd) pollution in agricultural soils induces oxidative stress in plants that in turn is the foremost limiting factor for agricultural productivity. In past few decades, plant–metal–microbe interaction is of great interest as an emerging environmentally friendly technology that can be exploited to alleviate metal stress in plants. Considering these, in the present study an endophytic bacterium strain EPS has been isolated from the roots of common bean. The present strain was identified as Stenotrophomonas maltophilia based on 16S rRNA gene sequence. The strain showed Cd tolerance and Cd-adsorption potentials. The inoculation of strain EPS in safflower seeds significantly enhanced the antioxidant defense of plants under Cd-stress conditions through increasing the levels of antioxidant molecules like phenolics, flavonoids and carotenoids as well as improving the activities of the antioxidative enzymes including guaiacol peroxidase (POX), ascorbate peroxidase (APX) and superoxide dismutase (SOD). The output of this study is that strain EPS inoculation mitigates Cd-induced oxidative stress and consequently it may be beneficial, especially in Cd-contaminated crop fields.