AMF and Bacillus megaterium Neutralize the Harmful Effects of Salt Stress On Bean Plants

Two pot experiments were directed under open field conditions where green bean (Phaseolus vulgaris L.) plants cv. Valentino were irrigated with four levels of salinity (1000, 2000, 3000 and 4000 ppm) combined with two anti-salinity agents (Arbuscular Mycorrhizal fungi [AMF] Glomus irradicans 10% w/w, Bacillus megaterium [10 ml/pot] and non-inoculated plants as control) to counteract the negative effect of salt stress, improve the growth, yield, enzymes activity and chemical composition of green bean plants during 2017and 2018 growing seasons. All salinity amelioration treatments (AMF and Bacillus megaterium) significantly improved vegetative growth, shoots biomass (total fresh and dry weight per plant), chlorophyll and antioxidant enzymatic activity at all verified salinity levels compared with non-inoculated plants (control) which showed severe growth retardation especially under the higher salt concentration (4000 ppm). The lowest values of membrane permeability and maximum leaf relative water content were significantly obtained with AMF and B. megaterium. Plants irrigated with lower concentrated saline water (1000 ppm) significantly accumulated lower Na and Cl and higher K than plants irrigated with higher concentrated salinity irrigation water (4000 ppm). The anti-salinity application increased green bean pod yield under all salinity stress levels particularly with AMF followed by B. megaterium compared with non-inoculated plants.