Genetic engineering of the biosynthesis of glycinebetaine leads to alleviate salt-induced potassium efflux and enhances salt tolerance in tomato plants

•Glycine betaine enhances salt tolerance in tomato plants.•Glycine betaine alleviated K+ efflux in salt stress by regulating ion channels.•Glycine betaine can maintain Na+-K+ homeostasis of tomato plants under salt stress.•Glycine betaine enhances antioxidant capacity of tomato plants under salt stress.