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Testcross Evaluation of Mexican Maize Populations¹

Maize(Zeo mays L.) breeders in the USA have emphasized selection in less than 5% of the total available maize germplasm. Although genetic gains have been made within races of maize adapted to the USA, there is interest in expanding the germplasm base available to applied breeding programs. Our objective was to evaluate the relative potential of improved Mexican germplasm in testcrosses with two U.S. Corn Belt populations. Field trials were conducted in eight environments in Mexico and four environments in the western U.S. Corn Belt in 1982 and included 24 Mexican populations crossed with U.S. Corn Belt adapted testers, BS13(S)C3 and Lancaster Composite. Few individual crosses yielded significantly better than the testers in the U.S. Corn Belt. Grain moisture at harvest, ear height, and days-to-flower were greater in crosses compared with testers perse. The BS13(S)C3 testcrosses had significantly greater yields than Lancaster testcrosses, but grain moisture at harvest, ear height, and lodging were not significantly different between the two sets of testcrosses. Both sets of testcrosses yielded significantly more than the checks in Mexico, suggesting that elite selections could be obtained for use in Mexico breeding programs. Crosses with BS13(S)C3 seemed to be more promising than crosses with Lancaster Composite in Mexico. Across 7729 and Poza Rica 7822 were the only Mexican populations that had significant estimates of general combining ability in both countries.

Key Words: Zea mays L. • Exotic germplasm • Recurrent selection • Germplasm evaluation

² Former student, Universidad Antonoma Agraria "Antonio Narro"; former Director, North Gulf Region, National Institute of Agricultural Investigations, Rio Bravo (Currently, corn breeder, SEFERSA, Los Mochis, Sin., Mexico); former graduate student, Univ. of Nebraska; Foundation Professor of Agronomy, Univ. of Nebraska; former corn breeder, INIA, Mexico, and graduate student, Iowa State Univ.; and research geneticists, USDA-ARS, Ames, IA, and Columbia, MO, respectively.

Received for publication February 25, 1985.