Inoculation of Pseudomonas mutant strains can improve growth of soybean and corn plants in soils under salt stress

Abstract

In the last decades, the applications of Plant GrowthPromoting Rhizobacteria (PGPR) as inoculants for enhancing crops yield underdifferent stress conditions have reached enormous interest. Pseudomonas putida KT2440 is awell-known rhizobacteria capable of colonizing roots of agronomically importantcrops. This work aims to evaluate three P.putida KT2440 mutants (mus-20, mus-42, and EU206), which have non-biofilm producingand exopolysaccharide overproducing phenotypes, for their potential as PGPR onsoybean and corn plants under saline stress. Experimental studies showed thatKT2440 and its mutants were effective in three main PGPR properties:solubilization of phosphates and synthesis of indolic compounds and siderophores.Notably, indolic compounds synthesis increased in mus-20 and EU206 strains.Furthermore, all evaluated strains were tolerant to saline stress. Bacterialinoculation of soybean and corn seeds was effective both in vitro and in vivotests, even at high salt concentrations (80 and 120 mM NaCl). Among mutantbacteria, EU206 strain seems to be the most efficient PGPR by significantlyincreasing seed germination, dry and fresh weights, and root and shoot lengths ofplants compared to non-inoculated controls, in in vivo tests under saline condition, mainly in both corn plants.These results suggest that inoculation with the P. putida KT2440 mutant strains is an appropriate strategy to enhancethe growth of soybean and corn plants, so they might be employed for promotingregional crops growth at field scale using natural saline soils.