The effect of combined application of B. japonicum and P. putida with mineral and organic fertilization on proline contents in soybean under phosphorus insufficiency and moderate drought

Abstract

The use of plant growth promoting rhizobacteria (PGPR) is considered a strategy to improve plant tolerance in hostile environments. However, its underlying mechanisms are not completly understood under phosphorus (P) insufficiency and water deficit conditions. In the present study, a vegetation vesselsexperiment was conducted to assess the combined effects of Bradyrhizobium japonicum inoculation with Pseudomonas putida in conjunction with P and organic fertilization on proline contents of soybean (Glycine max L.) plants grown in P-deficientsoil and subjected to moderate drought. The experimental results demonstrated that the application of both strains significantly changed proline contents in leaves and roots, especially under moderate drought and P insufficiency compared to the inoculation with the symbiotic B. japonicum strain alone. The rhizobacteria strains application without fertilization or with cattle manure increased proline accumulation in leaves under drought but did not affect significantly this parameter in well-watered plants.By contrast, integrated use of isolates decreased proline concentration in roots of soybean with mineral P and organic fertilization regardless of soil moisture level. In conclusion, the combined use of B. japonicum and P. putida is efficient approach to improve soybean growth and drought tolerance through altering proline contents, especially in soil with P insufficiency as well as under application of organic fertilizer.