Different results were shown in reference to the action of fl-a on protein quality (MNL 45:70 and 47:166). These data led to a study in order to clear up those communications. Crosses between a high-quality floury-a line (lysine 3.5 g/16 g Nitrogen, tryptophan 0.8 g/16 g Nitrogen) and normal lines (hard endosperm) with normal level of lysine (1.6) and tryptophan (0.4) were made (these levels are expressed for defatted endosperm). The segregation for quality between F2 kernels with floury phenotype permitted establishing a modification case on fl-a by two genes with accumulative effect and independent segregation without affecting endosperm texture (1/16 of F2 floury kernels have the same high-quality protein as high lysine-tryptophan fl-a line). These two genes, tentatively designated lysine-1 (ly) and lysine-2 (ly2), regulate lysine and tryptophan levels in the endosperm. High lysine level is conditioned by fl-a/fl-a/fl-a ly/ly/ly ly2/ly2/ly2 genotype, and normal level by fl-a/fl-a/fl-a Ly/Ly/Ly Ly2/Ly2/Ly2 genotype. Intermediate lysine-tryptophan levels were found for all possible different genotypes. The hypothesis that two genes have interaction with the fl-a was confirmed by quality segregation between F3 floury ears. Kernels and ears with high lysine-tryptophan levels have also approximately three times more water soluble free amino acids than their normal equivalents. Lysine-1 and lysine-2 genes in combination with fl-a have pleiotropic action for lysine, tryptophan and free amino acids of endosperm, and these features are highly positive correlated. The high-quality genetic system, floury-a lysine-1 lysine-2, modifies protein pattern: the effect was a repression of zein synthesis and a stimulation of albumin, globulin and glutelin synthesis. Floury-a high lysine has the following protein pattern: albumin, globulin 9%, zein 33% and glutelin 58% of total protein, respectively. Its normal equivalent has 4.5%, 50% and 45.5% for the same fractions, respectively. The high-quality genetic system formed by a floury gene (fl-a) and two non-floury genes, suggests the possibility of developing another system without floury genes, and a high-quality protein maize with normal genotype.
Jorge Luis Magoja
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