MOLECULAR-MARKER-MEDIATED CHARACTERIZATION OF FAVORABLE EXOTIC ALLELES AT QUANTITATIVE TRAIT LOCI IN MAIZE

Exotic maize (Zea mays L.) germplasm, shown to be useful for developin g improved temperate cultivars, has remained little used partly becaus e of many inherent shortcomings. Five Fz populations, developed from S outh American and U.S, germplasm, were used to detect favorable factor s of exotic origin at quantitative trait loci (QTL) with isozymes and RFLPs. A number of traits of agronomic importance, including grain yie ld, were measured on Pt individuals and/or F-3 families grown in sever al environments. Many QTLs, mostly with small effects, were identified . Major QTLs for grain yield and number of ears per plant were located on chromosomes 3 and 6. Stability of QTLs across environments was hig h. Favorable alleles of exotic origin were found at QTLs for several t raits including grain yield and number of ears per plant. Most of thes e alleles also showed undesirable effects on other traits, however. Ne vertheless, the superiority of exotic alleles over adapted alleles was demonstrated clearly al a few QTLs, reaffirming the usefulness of exo tic germplasm for temperate maize breeding.