Amino-acid content in grain protein of tetraploid Opaque-2 maize

Abstract

Amino acid composition in grain protein of a diploid (2х=20) single-cross maize hybrid containing opaque-2 (o2) gene and tetraploid (4х=40) derivatives of this hybrid was assayed. This mutant gene is widely used in maize breeding to improve quality of grain protein. Protein content was determined by the Kjeldahl method and analysis of protein amino acids - by ion exchange chromatography. Tetraploids, depending on genotype, showed higher protein content in grains than diploid forms and high variability in amino acid composition. Some derivatives contained higher levels of such amino acids like, lysine, arginine, aspartic acid and lower levels of leucine in protein in comparison with the diploid grains indicating possibilities to select valuable tetraploid forms. Grains with o2 endosperm from duplex-heterozygote self-pollinated ears showed higher content of lysine, arginine, valine, aspartic acid and glycine and reduced content of leucine, glutamic acid, proline and tyrosine than vitreous grains from the same ears, which highlights the specificity of gene effect. The analysis of dosage effect of the o 2 gene revealed that lysine content increases proportionally to the allele number of o 2 in the endosperm of diploid and, partly, in tetraploid grains. A possible maternal influence is indicated to explain the result.