EVALUATION OF EXOTIC AND ADAPTED MAIZE (ZEA-MAYS L) GERMPLASM CROSSES

Exotic germplasm may be used to increase genetic variability in temperate maize (Zea mays L.) breeding programs. The objectives of this study were to determine the performance of seven populations with exotic germplasm and two U.S. Com Belt populations for the proportions of exotic to adapted germplasm that exhibited superior performance, and the heterotic patterns between the exotic populations and the two U.S. Com Belt populations. The genetic materials included two adapted (0% exotic) and seven populations with exotic germplasm (100% exotic), crosses (50% exotic) and backcrosses (75% or 25% exotic germplasm) between them, and 10 check entries. The seven exotic populations had different levels of selection for adaptation to temperate environments. The materials were evaluated in a 13 x 13 simple lattice design at seven Iowa environments. Better yields were obtained for crosses with 50% exotic germplasm. Exceptions were observed in the crosses (50%) of Cateto by BS26 (51.5 q ha-1) and Caribbean Flint by BS26 (56.1 q ha-1), where the greatest yield was observed for BS26 (57.1 q ha-1), and in the cross of Tuxpeno by BS26, where the greatest yield was observed for the backcross with 25% exotic germplasm (58.8 q ha-1). The Suwan-1 and Tuxpeno populations have greater potential for continuing development because both populations had less selection for adaptation to the U.S. Com Belt compared with the other exotic populations. Higher midparent heterosis and coefficient of determination were observed when either Tuxpeno or Suwan-1 was crossed with BS13 and Suwan-1 was crossed with BS26. BS13, a strain of Iowa Stiff Stalk Synthetic, combined better with the exotic populations than did BS26, a strain of Lancaster Sure Crop. The results Suggest that either the exotic heterotic group of Suwan-1 and Tuxpeno be considered for further selection in the U.S. Corn Belt or that Suwan-1 and Tuxpeno be intercrossed with adapted heterotic groups and be included in selection programs that include adapted exotic and native germplasm.