Variability in a Silage Maize 'Zea mays, L.' Base Population via Two Types of Families 3. Forage botanical composition and dry matter partitioning

The base population for the recent study which is a yellow seed synthetic variety of maize was provided by Dr. M. Abd El-Sattar Ahmed, professor of crop science, Crop Science Department, faculty of Agriculture, Egypt. Two types of families had formulated, as a step before selection for high yielding ability. Those were half-sib (H.S) families and the first generation of self-pollination (S1) families. Variability in the base population gene pool had estimated depending on vari-ance components of the families. Reduction in mean values associated with S1 families relative to half-sib families reached 0.182, 1.18, 0.98, 3.88, 2.75 and 5.72% for leaves percentage, stem percentage, ear percentage, grain percentage, cob per-centage and husk percentage, respectively. Genotypic variances among S1 families was larger in magnitude than the respec-tive value for half-sib families in each measured botanical composition and dry matter partitioning characters. Meanwhile, within family’s variance, (σ2f), environmental variances (σ2e) had reduced in S1 families relative to half-sib families in each measured character. Genotypic variation among half-sib and S1 families were less than 20% of the studied botanical compo-sition and dry matter partitioning characters mean values, except for cob percentage and husk percentage that had a genotyp-ic variation amount to 24% and 26%, respectively. The estimates of additive variance (δ2A) were positive for all studied botanical composition and dry matter partitioning characters. While, the estimates of dominance variance (δ2D) were nega-tive for all characters, the ratio of δ2A/δ2G indicated that additive genetic variance was more effective in controlling all stud-ied botanical composition and dry matter partitioning characters. Estimates of heritability were higher in magnitude when calculated from first selfing generation (S1) compared to half-sib families, for all studied characters. Stem percentage ex-pressed the least estimate heritability among all studied characters in each family type (0.798 and 0.414 for half-sib and S1 families, respectively). This might indicate the influence of environment in the expression of that character. Meanwhile husk percentage had highest genetic control expressed on heritability estimates from the two studied types of families.