Phosphate-mobilizing microorganisms as a factor in plant resistance to salt stress

Abstract

The study was conducted for the primary screening of 27 strains of rhizosphere phosphate-mobilizing microorganisms belonging to the genera Enterobacter, Klebsiella, and Bacillus for their ability to resist salt stress and increase plant tolerance to it (using white mustard (Sinapis alba) seeds as an example). Salt tolerance was determined by plating on a solid nutrient medium (NBRIP) (National Botanical Research Institute's Phosphate growth medium) with NaCl concentrations of 0.2; 0.4; and 0.6 %. Across all experimental variants, 17 strains maintained vigorous growth, and 6 strains demonstrated high phosphate-mobilizing activity. In a laboratory experiment, sterilized seeds of white mustard variety Omega were inoculated with aqueous suspensions of 6 bacterial strains that exhibited halotolerant properties (titre 1×106 cells/ml) and germinated on Knop medium with NaCl. Seed germination in the presence of 0.2 and 0.4 % NaCl under the influence of the Bacillus sp.1 strain increased by 25 and 42 %, respectively; in the presence of 0.6 % NaCl under the influence of the Enterobacter sp.2 strain – by 51 %. Stimulation of seedling root length in the presence of 0.2% NaCl was provided by the Enterobacter sp.11 strain (by 104 %); in the presence of 0.4 % NaCl – by the Bacillus sp.1 strain (by 110 %); 0.6 % NaCl – by the Enterobacter sp.2 strain (by 238 %). An increase in hypocotyl length in the presence of 0.2% NaCl was observed with Enterobacter sp.1 (by 68 %) and with Enterobacter sp.2 (by 53%) in the presence of 0.6% NaCl. The following strains contributed to an increase in seedling raw biomass in the presence of 0.2% NaCl: Enterobacter sp.11 and Enterobacter sp.1 (by 20 %); and in the presence of 0.4 and 0.6 % NaCl, Enterobacter sp.2 (by 75 and 133 %, respectively). The studied halotolerant strains effectively alleviate osmotic and ionic stress, allowing them to be recommended for use in agrobiotechnology on saline soils.