Involved in salt tolerance by producing GG-phosphate from ADP-glucose and glycerol-3-phosphate (G3P), an intermediate in the synthesis of the osmolyte glucosylglycerol (GG). ADP-alpha-D-glucose + sn-glycerol 3-phosphate = 2-O-(alpha-D-glucopyranosyl)-sn-glycerol 3-phosphate + ADP + H(+) Glycan metabolism; glucosylglycerol biosynthesis. By salt shock. Belongs to the glycosyltransferase 20 family.