Composite Line Method for the Development of Early Generation Hybrids of Maize (Zea mays L.)

Abstract

Six commercial single crosses were used for the improvement of composite and inbred lines. Modified S1-full sib selection was applied to improve the three sister line composite. Lines were visually selected under low-competition environment in honeycomb arrangement with equilateral triangular side of 0.866 m. Testcross as well as diallel cross were applied to identify high combining lines. All yield trials were conducted in randomized completed block design with 4 replications, 1 row plot of 5 m long and 0.75 × 0.25 m plant spacing. Standard cultural practices were regulated and irrigation was applied as needed. Statistically, there was no clear advantage of yield between composite and inbred lines in early generation testcrosses. Besides, the diallel sets of both groups of lines gave similar results. However, the top hybrids of overall trials came from composite crosses even though it was not significant. In addition, composite lines were superior to S3 lines in yield, earliness and plant height. Modified S1-full sib selection is a flexible breeding method but its merit for the construction of early generation hybrids must be thoroughly investigated even though the positive results were observed.