Classifying Maize Inbred Lines into Heterotic Groups using a Factorial Mating Design

A novel method of using a heterotic group's specific and general combining ability (HSGCA) to assign maize (Zea mays L.) inbred lines into heterotic groups has been proposed recently. The objectives of this study were to (i) assign maize inbred lines to known heterotic groups using this method and (ii) compare efficiency of this method to traditional and molecular methods relative to the percentage of high-yielding hybrids obtained across the total number of the crosses made between testers and lines. An experiment with 23 maize inbred lines crossed to four testers with known heterotic groups was conducted in 2003 and 2004. This study successfully established a clear procedure to classify maize inbred lines into heterotic groups. The HSGCA method increased maize breeding efficiency by 16.7 to 23.6% compared with simple sequence repeat (SSR) and specific combining ability combined line pedigree and hybrid yield information (SCA_PY) methods, respectively. An analysis of variance showed that crosses classified by HSGCA method could explain more variation in maize hybrid yield and produce more predictable yield than the other two methods. The superiority of HSGCA relative to the other two methods is that HSGCA includes both GCA and SCA effect in assigning an unknown maize line to a known maize heterotic group.