| Quantitative trait locus (QTL) mapping has detected two linked QTLs in the chromosome arm 8L segment introgressed from Gaspe Flint (a Northern Flint open-pollinated population) into the background of N28 (a Corn Belt Dent inbred line). Homozygous recombinant lines, with a variable length of the introgressed segment, confirmed the presence of the two previously identified, linked QTLs. In the N28 background, Gaspe Flint QTL-alleles at both loci induce a reduction in node number, height and days to pollen shed. Given the determinate growth pattern of maize, the phenotypic effects indicate that the two QTLs are involved in the transition of the apical meristem from vegetative to generative structures. Having separated the two linked QTLs we have laid the foundation for the positional cloning of the QTL with a larger effect. Relative to the effects of the two QTLs in the background of N28, we distinguish two general developmental factors affecting the timing of anthesis (pollen shed). The primary factor is the timing of the transition of the apical meristem. The second, derivative factor is the global extent of internode elongation. The effects of the Gaspe Flint QTL-alleles relative to the N28 QTL-alleles are also detectable in other homogeneous and heterogeneous backgrounds. |
