Inheritance of DNA Concentration, and Cellular Contents of Soluble Protein, Chlorophyll, Ribulose Bisphosphate Carboxylase, and Pyruvate,Pi Dikinase Activity in Maize Leaves

The inheritance of deoxyribonucleic acid (DNA) concentration, and soluble protein, chlorophyll, ribulose bisphosphate carboxylase (RuBPCase) activity and quantity, and pyruvate,Pi dikinase (PPDK) activity in maize (Zea mays L.) leaves were characterized. The amounts or enzyme activities of these cellular constituents were expressed on a DNA basis. This mode of data expression corresponds to relative cellular contents as DNA per nucleus is constant. A 6 ✕ 6 diallel revealed highly significant general combining ability effects for all traits. Although specific combining ability effects were significant for a few traits, these effects were of small magnitude, and variance associated with general combining abilities accounted for 77 to 98% of total genetic variance. Reciprocal effects were detected only for RuBPCase specific activity. Mid-parent heterosis was found for soluble protein, chlorophyll, and RuBPCase, and the fraction of soluble protein as RuBPCase. Relative cell volume, as estimated by DNA concentration, showed little or no heterosis. Highest heterosis (up to 40%) was found for RuBPCase protein, an observation which can be accounted for by concurrent increases in the total soluble protein content and in the fraction of protein as RuBPCase in cells of these hybrids. Correlations between the degree of heterosis of paired traits indicated that hybrids heterotic for soluble protein have larger amounts of chloroplastic components per cell. The PPDK activity was determined in F₁, F₂, and backcross populations from a cross between two inbreds with contrasting PPDK activity. The F₁ generation indicated complete dominance of the level of activity found in the high parent. Segregation in F₂ and backcross generations did not fit a single dominant gene hypothesis. Calculations indicated that a minimum of one locus governs this trait, suggesting that few genes or even one gene modulated by modifiers control PPDK activity. DNA concentration (an estimate of relative cell volume) was found to be a polygenic trait (at least three loci). Variance associated with general combining abilities comprised 90% of the total genetic variance for this trait.