Evaluation of exotic and adapted maize (Zea mays L.) germplasm crosses.

Exotic germplasm may be used to increase the genetic variability in the U.S. maize populations. The objectives of this study were to determine the relative performance of exotic germplasm to two widely used U.S. Corn Belt populations, to determine the proportions of exotic to adapted germplasm that exhibited superior performance, and to determine the heterotic patterns between the exotic populations and the two widely used Corn Belt populations. A 13x13 simple lattice design was used and the study was conducted in seven Iowa environments. The treatments included the adapted (0% exotic) and exotic germplasm (100% exotic), the crosses (50% exotic) and backcrosses (75% or 25% exotic germplasm) between them, and the check varieties. The results for grain yield (q/ha) suggest that the best percentage of exotic germplasm used was 50%. Exceptions were observed in the crosses of Cateto by BS26 (51.5 q/ha), Caribbean Flint by BS26 (56.1 q/ha), where the highest yield was observed for no exotic germplasm, BS26 (57.1 q/ha), and in the cross of Tuxpeno by BS26, where the highest yield was observed for the treatment with 25% exotic germplasm (58.8 q/ha). Suwan 1 and Tuxpeno exotic germplasms have greater potential for continuing development. Both germplasms had mild selection for adaptation in the U.S. Corn Belt compared with the other exotic germplasms. Despite no selection for adaptation and without considering the reciprocal crosses, the crosses Tuxpeno by BS13 (72.0 q/ha) and BS13 by Suwan 1 (69.1 q/ha), ranked fourth and fifth in the treatments per se, where the top ranked treatment was the