GENETIC EFFECTS OF DIRECT AND RECIPROCAL CROSSES OBTAINED FROM TWO GERMPLASM GROUP LINES IN MAIZE

Abstract

The phenotypic and genotypic expression of 90 single maize (Zea mays L.) crosses (A x B) obtained by crossing 10 lines from the dwarf group (A) with nine QPM normal lines (B), plus the 90 reciprocal crosses (B x A), were analyzed in this work. Crosses were evaluated in three contrasting environments in 2004. The average performance across locations was used to analyze the crosses expression, and to estimate the combining ability of lines and crosses on the A x B and B x A combinations for plant height (cm) and ear yield (t ha^-1). Significant differences (P ≤ 0.01) among crosses were found, as well as in their group components A x B and B x A in lines, testers and the line by tester interaction within each group for the two traits analyzed, including the groups A x B vs. B x A contrast. Results indicated variability within each group, the meaning of their interaction, and the difference between the direct and reciprocal effects of crosses. The crosses expression between lines from the two germplasm groups were determined by additive effects, mainly in the QPM lines with 70.2 and 61.5 % of the explained variation for plant height and ear yield, respectively. In the combination of lines among genetically unrelated germplasm groups, a modification in the participation order of parental lines determines the differences in the phenotypic expression, and in the estimation of lines and crosses genetic effects. The values of the general combining ability estimates were modified by the crossing order in the dwarf group, and the non-additive effects of the lines from the two groups, as correlations of r_s = 0.184 and r_s = 0.252* were obtained for plant height and ear yield.