Some Aspects of High Lysine Maize Breeding Using Opaque-2

Abstract

Several field and sweet corn varieties from several sources were crossed with a variety carrying the opaque-2 gene to determine the phenotypic interactions in the breeding of high lysine maize. The F₂ segregation ratios for normal and opaque-2, 100-kernel weights, percentage seed set, opaque-2 phenotype, disease susceptibility, and the relationship between protein and lysine content of normal and opaque-2 \were investigated. The determinations and observations were made on the F₂, F₃ and BC₁^. Lysine content was determined by the ion exchange resin combined with paper chromatography method. Even though opaque-2 lines showed lower protein content than the corresponding normal varieties, there was no correlation between the protein levels of the two types. Opaque-2 maize contained more Iysine, but no relationship was found between the protein content and the lysine content of either normal or opaque-2 types, suggesting that high lysine corn using the opaque-2 gene may be developed independently from the protein content. Most crosses segregated in a l-opaque-2 : 3-normal ratio as expected. Opaque-2 segregates were lighter than the normal type and smaller in size in certain crosses. A mottled phenotype of opaque-2 was observed in the Philippines yellow endosperm. In some varieties opaque-2 maize was very susceptible to the ear and kernel rot disease.