ACCD-producing rhizobacteria from an Andean Altiplano native plant (Parastrephia quadrangularis) and their potential to alleviate salt stress in wheat seedlings

1-Aminocyclopropane-1-carboxylate deaminase (ACCD)-producing rhizobacteria are widely studied as plant growth-promoting rhizobacteria (PGPR) to alleviate a variety of stresses in plants. However, the presence of ACCD-producing rhizobacteria in plants that naturally occur in stressful ecosystems as well as the potential PGPR activity in agriculturally relevant plants has been poorly explored thus far. We isolated and characterized ACCD-producing rhizobacteria from Parastrephia quadrangularis, a native plant from the Andean Altiplano in Chile. The effects of selected ACCD-producing rhizobacteria on biomass and superoxide dismutase (SOD) activity of wheat seedlings subjected to salt stress (0.25 M and 0.45 M NaCl) were also evaluated. Ten out of 30 isolates showed ACCD activity (0.83-3.32 mu mol alpha-ketobutyrate mg(-1) h(-1)) and were identified as members of the Enterobacteriales order (mainly Serratia and Klebsiella). The ACCD-producing rhizobacteria also showed salt tolerance (from 2.5 to 7.5% NaCl) and other PGPR traits, such as the production of auxin (from 20.3 to 41 mu g mL(-1)) and siderophores (from 3.35 to 67.7%). Wheat seedlings inoculated with two selected ACCD-producing Klebsiella isolates (8LJA and 27IJA) significantly (P <= 0.05) increased the biomass (45-62%) content and SOD activity in roots (18-35%) with and without salt stress. This study demonstrated that PGPR were associated with native plants in the Andean Altiplano and offers a promising potential source of novel PGPR to alleviate salt stress in plants.