Determination of the Heterotic groups of Maize inbred lines and the Inheritance of their Resistance to the maize Weevil

Maize weevil (Sitophilus zeamais Motschulsky) is a major maize (Zea mays L) storage insect pest in the tropics. Fifty-two inbred lines developed for weevil resistance were crossed to two testers, A and B, to determine their heterotic groups and inheritance of resistance to maize weevil. For 10 testcrosses selected for performance by tester, the correspondent testcrosses onto the opposite tester and all the parents involved in those crosses, were included in the combining study. Of 52 inbred lines, 7 had significantly positive general combining ability (GCA) for yield, with a maximum GCA effect of 1.24 t ha-1. Based on the specific combining ability (SCA) effect, 23 inbred lines were assigned to heterotic Group A, 24 to Group B, and 5 to both A and B. The combining ability test for weevil resistance revealed that only one inbred, WL118-9, was classified as moderately resistant with a susceptibility index (SI=5.4), two lines were moderately susceptible; and the remaining inbreds were susceptible to highly susceptible to the maize weevil. Additive and non-additive gene action were important for yield, but for weevil resistance, additive gene action was more important. Weevil resistance exists and is moderately heritable.