Plant Growth-promoting Rhizobacteria Mitigate Deleterious Effects of Salt Stress on Strawberry Plants (Fragaria ×ananassa)

Abstract

The effect of selected plant growth-promoting rhizobacteria (PGPR) on the growth, chlorophyll content, nutrient element content, and yield of strawberry plants under natural field salinity conditions stress was investigated. Field experiments were conducted using a randomized complete block design with five PGPRs (Bacillus subtilis EY2, Bacillus atrophaeus EY6, Bacillus spharicus GC subgroup B EY30, Staphylococcus kloosii EY37, and Kocuria erythromyxa EY43) and a control (no PGPR) in 2009 and 2010. PGPR inoculations significantly increased the growth, chlorophyll content, nutrient element content, and yield of strawberry plants. PGPR treatments lowered electrolyte leakage of plants under saline conditions. The leaf relative water content (LRWC) of plants rose with bacterial inoculation. All nutrient element contents of leaves and roots investigated were significantly increased with PGPR inoculations with the exception of sodium (Na) and chlorine (Cl). The highest efficiency to alleviate salinity stress on the yield and nutrient uptake of strawberry plants was obtained from EY43 (228 g per plant) and EY37 (225 g per plant) treatment and the yield increasing ratio of plants was 48% for EY43 and 46% for EY 37 compared with the control treatment (154 g per plant). The highest nitrogen (N), potassium (K), phosphorus (P), calcium (Ca), magnesium (Mg), sulfur (S), manganese (Mn), copper (Cu), and iron (Fe) concentrations were obtained from EY43 and followed by E6, E37, and E30, and increasing ratio of leaves and root N, P, K, Ca, Mg, S, Mn, Cu, and Fe contents were 22% to 33%, 34% to 8.8%, 89% to 11%, 11.0% to 7.2%, 5.1% to 6.2%, 97% to 65%, 120% to 140%, 300% to 15%, and 111% to 9.0%, respectively. The results of the study suggested that PGPR inoculations could alleviate the deleterious effects of salt stress conditions on the growth and yield of strawberry plants under salinity conditions.