Characterization of a major maize domestication qtl on the short arm of chromosome 1

Inheritance of the basic morphological differences between primitive maize and teosinte is mainly controlled by genes falling within five or six regions of the maize genome. Herein, we focus on one of these regions, the short arm of chromosome 1, for which we created a nearly-isogenic line (NIL) consisting of a teosinte chromosome segment (T1S) introgressed into maize inbred line (W22). By crossing this NIL with W22 and then selfing for 6 generations, 135 nearly isogenic recombinant inbred lines (NIRILs) were recovered for the TlS chromosomal region. We mapped the cross-overs within the T1S segment for each NIRIL and collected phenotypic data for domestication and other traits on each NIRIL. Using these data, we mapped 15 quantitative trait loci (QTLs) controlling several domestication, developmental, and seed-related traits. The proportion of the phenotypic variance explained by the QTLs for a trait ranged from 7% to 65% and the direction of the effects of most QTLs agreed with the expectation that teosinte alleles should be associated with teosinte-like phenotypes. Most QTL for domestication-related traits co-localized to the same 15 cM region near the center of the introgressed segment. These QTL could represent either a single major gene with pleiotropic effects or several tightly linked genes. Positional cloning studies are now underway to distinguish these two hypotheses.