High-lysine mutants of rice, Oryza sativa L.

In order to improve the nutritive value of rice protein, it is necessary to increase the level of lysine and threonine. Ten high-lysine mutants were selected from N-methyl-N-nitrosourea-induced (MNU-induced) mutant lines, using high-performance liquid chromatography for amino acid analysis. The lysine content of these mutants ranged from 5.10% to 6.38% of total amino acids, while that of the original varieties was about 4%. All high-lysine mutants also had a greatly increased histidine content and a floury endosperm. An increase in lysine content of the albumin/globulin fraction was characteristic of the MNU-induced high-lysine mutants. The segregation ratio of normal to floury endosperm in the F2 seeds from a cross between ‘Kinmaze’ and a high-lysine mutant fitted the expected 3:1 ratio. The high level of lysine and the floury endosperm may be controlled by the same gene.