Potential Use of Alien Germplasm for Maize Improvement1

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Abstract
Plant breeders have demonstrated the potential ability of exotic and alien germplasm to enhance particular qualitative genetic traits of maize, (Zea mays L.). Results from such programs include the incorporation of genes that condition resistance to pathogens or insect pests. Fewer examples exist which provide information on how alien and exotic germplasm affect quantitative traits, although studies have shown it is possible to increase heterosis or to expand the level of genetic divergence between breeding populations by using such germplasm. However, in either case, most breeders prefer current, elite inbreds with known combining ability as sources for inbred development and for improvement of hybrid performance. Alien germplasm was evaluated for its effects on quantitative traits by crossing seven substitution lines, each containing various segments of germplasm from teosinte (Zea mexicana), with three testers, and measuring the effects on maize hybrids. A performance trial was used for this evaluation from which data were collected for 12 traits on 23 hybrids. Significant differences in grain yield and heterosis were obtained between the means of the three testers and among the various substitution line hybrids. One tester, Havels‐(20 + 2Tr7), contained an extra disomic chromosome from Tripsacum dactyloides. Hybrids with this tester had a combining ability value 8% higher than the isogenic control. The highest yielding hybrids were the teosinte A158‐substitution lines involving the Florida and Durango teosinte types crossed with the Havels testers. The two highest yields occurred from crossing the Havels tester containing the Tripsacum chromosome with the A158‐Florida 4,9 and the A158‐Florida 9 teosinte substitution lines.

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