Halotolerant Streptomyces spp. induce salt tolerance in maize through systemic induction of the antioxidant system and accumulation of proline

Abstract

Plant Growth Promoting Rhizobacteria (PGPR) can mitigate the detrimental effects of salinity in plants. We characterized Streptomyces spp. as halotolerant PGPR and evaluated their influence on salt stress-tolerance mechanisms in maize plants. Bacterial halotolerance was evaluated at concentrations up to 900 mM NaCl, analyzing cell growth, viability, and production of secondary metabolites. The mechanisms of systemic tolerance in plants, such as the enzymatic activity of the antioxidant system and the production of osmolytes, were analyzed in bacterized plants under salt stress (100 and 300 mM NaCl). Isolates proved viable and produced indolic compounds and siderophores under NaCl conditions. Synthesis of indolic compounds and phosphate solubilization were induced in CLV179 by salt stress. The activity of the antioxidant enzymes and the synthesis of proline increased in bacterized plants submitted to salt stress, mainly those treated with isolate CLV97 and CLV179. Response of Streptomyces-treated plant to salinity was observed in roots and leaves, suggesting a mechanism of systemic tolerance. Therefore, bacterization with Streptomyces spp. alleviated the deleterious effects of salinity in maize plants by modulating the enzymatic and non-enzymatic antioxidant mechanisms.