Characterization of high-lysine barley genotypes

Abstract

The lysine increase caused by single recessive genes is governed by two mechanisms in high-lysine barley mutants: either a decrease of the lysine-poor prolamins is compensated for by increased amounts of free lysine and non-prolamin proteins, or specific lysine-rich proteins are increased. One approach for obtaining an enhanced lysine content in the barley seed has been to combine high-lysine genes from each type. Herewith an increased lysine content has been achieved by an interactive effect of the high-lysine genes. In these combinations the glutelin proteins contribute with the greatest proportion of total seed lysine. Rat nitrogen balance tests show that the nutritional quality is improved to meet the essential amino acid requirement by man as well as monogastric animals. The grain weight and, thus, the grain yield of these high-lysine combinations are, however, reduced compared to standard varieties. An impaired synthesis of storage proteins (prolamins) and of starch can partly explain the lowered grain weight. By selecting for genetic backgrounds that interact harmoniously with the high-lysine genes the lowered grain yield might be overcome. Lysine screening methods are evaluated and divided into two groups, those detecting the lysine increase directly, and those indicating the lysine increase by measuring other properties.