High-lysine proteins in Hiproly barley breeding: Identification, nutritional significance and new screening methods

Abstract

A 4–7 fold increased content of four major salt-soluble proteins in the barley grain was found to be closely associated with the Hiproly high-lysine character. The proteins were identified by crossed Immunoelectrophoresis as: “free” β-amylase, “free” protein Z and two different chymotrypsin inhibitors, with lysine content of 5.0, 7.1, 9.5, and 11.5 g per 100 g protein, respectively. The two inhibitors seem to be the major high-lysine proteins detected in previous studies of Hiproly. Rocket Immunoelectrophoresis showed that, in total, the four proteins may account for about 7 % of the grain lysine in normal varieties, 17 % in Hiproly lines, and more than 50 % of the increase in grain lysine due to the Hiproly lys gene. Total β-amylase, total protein Z and total chymotrypsin inhibitor seem to contribute equally to this increase. Analyses of Hiproly breeding material showed that screening for the high-lysine character can be based on simple assays for one of the proteins, not depending on determination of total protein in the grain. Especially, the determination of total chymotrypsin inhibitor activity in flour, single-grain or half-grain samples is suggested as a fast and reliable screening test in future breeding with Hiproly.