Agronomist Instituto de Investigaciones Agropecuarias (INIA) Rengo, Libertador General Bernardo O'Higgins, Chile
Body of Abstract: Salt-stress negatively affects plant physiology, both in the whole plant as well as at cellular levels, decreasing yield and the quality of crops. To deal with this kind of constraint, one promising strategy has been recommended: plant growth-promoting rhizobacteria procedure (PGPRs). This study hypothesises that PGPRs increase the tomato tolerance to saline conditions (NaCl) in the presence of Bacillus amyloliquefaciens at the root level (rhizosphere). The purpose is to investigate the effect of rhizobacteria (B. amyloliquefaciens) on growth, physiological parameters and Na+ and K+ content in tomato plants under salt-stress conditions (NaCl) during the vegetative stage. The effect of two strains of B. amyloliquefaciens (BAS10 and INIA-2444) was evaluated in two tomato varieties, a commercial ‘LV7742’ and a local one ‘Poncho Negro’. The B. amyloliquefaciens strain 2444 (INIA) was inoculated at 106 CFU/ g in the soil 10 days before starting the transplanting. Control treatments without bacteria are considered. Salt-stress was imposed seven days after transplant by two concentrations of sodium chloride (0 and 160 mM NaCl) to the nutritive solution for 21 days. The effect of B. amyloliquefaciens and salinity were evaluated on shoots and roots growth, chlorophyll and MDA contents, enzymatic activities (APX, SOD, DHA, GR), including mineral content (Na+ and K+) in roots and leaves. Na+ content in leaves increased in response to salinity but was higher in Poncho Negro than in ‘LV7742’, where this effect was greater with strain BAS10, compared with strain INIA 2444. Na+/K+ ratio in roots and leaves was considerably lower in the LV744 in the presence of both types of rhizobacteria strains compared to ‘Poncho Negro’. In conclusion, these results suggest that salt tolerance is enhanced by the presence of the studied rhizobacteria but the intensity of this effect depends on the interaction of the strains and the tomato plants genotype used.