Combining Ability and Heterosis Studies from diallel Cross of Quality Protein Maize (Zea mays L.) Inbred Lines. This book is about studies on Combining Ability and Heterosis from a diallel cross of six quality protein maize inbred lines, in order to identify promising parents with good breeding values for development of high yielding hybrids, synthetics and open pollinating varieties. Diallel mating design was used to inter mate the inbred lines. The generated hybrids and checks were evaluated in three environments. Significant mean squares were observed among the entries for most agronomic traits, indicating wide genetic variability in the germplasm. The GCA variance was higher than SCA variances for all traits except moisture content and grain yield indicating preponderance of additive genes.High level of Heterosis especially for grain yield suggests possibility of developing suitable high yielding hybrids and synthetic varieties. The study revealed tremendous opportunities for development of quality protein maize hybrids and synthetics adapted to Nigerian environment.