Breeding Potential in the USA and Argentina of Corn Populations Containing Different Proportions of Flint and Dent Germplasm

Recent yield increases of flint corn (Zea mays L.) hybrids in Argentina are probably due to introgression of elite dent germplasm from the USA into breeding materials being used to develop flint hybrids adapted to the Argentine Corn Belt. The present study was conducted to evaluate the breeding potential of four corn populations with different proportions of flint and dent germplasm for grain yield and other agronomic traits in the USA and Argentina. Each population was crossed to an Argentine flint and a USA dent inbred tester. The population testcrosses were evaluated in 1984 in the USA. In addition, 50 S₂s from each population were crossed to both testers. The testcross families were evaluated under 0 and 280 kg N ha⁻¹ at Champaign, IL and under 20 and 300 kg N ha⁻¹ at Havana, IL during 1985 and under 0 and 200 kg N ha⁻¹ at three locations in Argentina during 1986. In both countries, yields increased significantly as the proportion of dent germplasm in the population increased. The increased yields could be explained by heavier ears, higher ear kernel row number, and heavier and deeper kernels. Conversely, when tested in the USA, kernel protein and oil concentration decreased as proportion of dent germplasm in the population increased. Crosses to the dent tester had lower concentrations of protein and oil than crosses to the flint tester. Within a country, populations did not differ significantly for family variance component or heritability estimates for any trait. Pooled across populations, prolificacy showed the highest positive genetic correlation with grain yield in both countries. The use of prolificacy as a secondary trait could improve the efficiency of index selection of these populations with the flint tester in the USA by approximately 3%. The population with 25% flint germplasm seems to be the most suitable for developing high-yielding hybrids with good standability. Contribution from the of Agronomy Dep., Univ. of Illinois. Supported by funds from the Illinois Agric. Exp. Stn. and a gift from Ciba-Geigy Corp.