Combining Ability of Yellow Lines Derived from CIMMYT Populations for Use in Subtropical and Tropical Midaltitude Maize Production Environments

The introduction and utilization of new maize (Zea mays L.) germplasm from sources, such as the International Maize and Wheat Improvement Center (CIMMYT), can be valuable for broadening the genetic base of breeding populations through the introgression of new alleles. Twenty-five inbred lines, derived from CIMMYT breeding populations, were selected on the basis of grain color, resistance to turcicum leaf blight, and per se line performance in Yunnan. To use the lines effectively, information on their performance in hybrid combinations and on general combining ability (GCA) and specific combining ability (SCA) needed to be obtained. The objectives of this study were (i) to evaluate these lines for grain yield (GY) in hybrid combinations and determine GCA of parental lines and SCA of crosses between the 25 introduced lines and six testers using North Carolina Design II; and (ii) to classify the lines into different maize heterotic groups. The field testing at three locations identified crosses with lines from Cateto and Population 147 (P147) as having significantly higher GY than those from SA3 and other introduced populations, and the high GY was largely attributable to their high positive GCA effects. Lines from the same population were not necessarily classified into same maize heterotic group. Lines selected at S-4 or a later generation would be expected to have more stable GCA effects than lines selected in earlier generations.