THE DOSAGE EFFECT OF THE OPAQUE-2 GENE ON THE AMINO ACID COMPOSITION OF PROTEIN FROM TETRAPLOID MAIZE GRAIN

In this paper we aimed at studying the influence of different doses of opaque-2 gene (number of recessive alleles) in endosperm on amino acid composition of grain protein from tetraploid maize in comparison to diploid forms. Biochemical analysis was performed on grains of a comercial hybrid ChiЮiniovschi 307 PL containing the mutant gene, tetraploid forms of this hybrid obtained by colchicine treatment, a commercial hybrid Porumbeni 331Mrf and tetraploid synthetic population B. Protein content was determined by the Kjeldahl method, amino acid composition was assayed by ion exchange chromatography on an automatic amino analyzer T339M. In diploid grains the o2 gene showed a clear dosage effect on the content of lysine. In tetraploid grains, two recessive alleles of o2 gene in the hexaploid endosperm determined an increase in the content of lysine in protein as compared to the dominant genotype, in the four dose endosperm, the lysine content was intermediate between the dominant and two dose genotypes and was significantly higher in six doses. The expression pattern of the o2 gene was similar in replicate experiments carried in different growing season. As a result, it was concluded that the o2 gene has a dosage effect in diploid maize and, partially, in tetraploid maize.