Canola inoculation with Pseudomonas baetica R27N3 under salt stress condition improved antioxidant defense and increased expression of salt resistance elements

Abstract

Inoculation with growth promoting rhizobacteria (PGPR) can lessen salt salinity injury in plants by improving some physiological, biochemical, and molecular aspects. The current study aims to investigate Pseudomonas baetica R27N3 on photosynthetic capacity, and the antioxidant defense system of salt-affected canola plants (0, 100, 200,300 mM NaCl) under greenhouse conditions. Sodium concentration in inoculated canola plants was significantly decreased, whilst potassium increased through improved root architecture and relative expression of ion pump genes, such as SOS1 and KAT1. Moreover, inoculated canola plants showed higher antioxidant capacity which was evident in their higher antioxidant enzyme activity and those enzymes' higher relative gene expression. The study investigated additional physiological parameters related to enhanced antioxidant defense, including the electrolyte leakage index and malondialdehyde concentration as indicators of the stability of the plant cell plasma membrane. The plasma membrane of canola plants treated with PGPR was significantly more stable than those without the PGPR treatment. Furthermore, carotenoids and proline accumulation as non-enzymatic antioxidant solutes and total protein were increased in canola plants treated with R27N3. On the whole, these improvements coincided with increased antioxidant capacity, but all these positive effects of R27N3 were notable under 100 mM of NaCl concentration, whereas under 0 and 300 mM of NaCl concentration physiological and molecular changes between inoculated and non-inoculated canola plants were not statistically notable. Consequently, positive molecular and biochemical changes could be mediated by P.baetica R27N3 ability to clone on canola root and provide it with a decent level of macro-nutrients.