In 1964 Mertz et al. reported that opaque-2 (O
2) gene changed the protein composition and increased the lysine content of maize endosperm. A second high lysine maize mutant floury-2 (fl
2) was identified and reported in 1965. Recently, it was found that several of starch-modifying genes increased the lysine content of maize endosperm substantially above the isogenic normal control, and each gene showed an enhanced effect on lysine when combined with O
2 gene. Mutants with starch-modifying genes were concerned with changes influencing gelatinization temperature, viscosity, gel stability of starch, starch granule digestibility, and the production of amylose, amylopectin, water-soluble polysaccharides, and sugars. In studies of starch-modifying genes and their combination with O
2 or fl
2 gene, it was shown that O
2 or fl
2 dose not change the production of amylose, amylopectin, water-soluble polysaccharides, and sugars of maize kernels with each one of starch-modifying gene, and O
2 gene has no effect on susceptibility of starches with amylases. It seems probable that the interaction of the O
2 gene with many of starch mutants of the maize endosperm provide a variety of maize containing starch with characteristics specific for the starch mutant and protein with high nutritional quality.
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