Resistance of maize to the maize weevil: II. Non-preference

Abstract

Although there have been significant advances in improving maize for grain yield, progress in developing varieties resistant to the maize weevil (Sitophilus zeamais Motsch.) has been limited. In this study, fifty-two hybrids were evaluated against the maize weevil for non-preference in free choice experiment to study gene action determining inheritance of this mechanism of resistance. Eighteen inbred lines, six each from southern Africa, Mexico and CIMMYT-Zimbabwe were used to make the hybrids. Lines were mated among sub-groups of three each, according to a North Carolina Design II scheme. F2 grain of the hybrids was evaluated for non-preference resistance under controlled temperature and relative humidity conditions. Maize weevil preferred some hybrids, and caused grain weight losses ranging from 0.85 to 8.45% after 70 days of feeding in a free-choice environment with equal access to all maize genotypes. The maize weevil preferred 'SR52', a local commercial hybrid that we used as the susceptible check (6.62% weight loss), and other local hybrids (6.02 to 6.80% weight loss), to 'Oaxaca 179' (the resistant check), which incurred a weight loss of 3.50%. Four percent of the experimental hybrids incurred less than 2.0% grain loss and were classified as resistant, while a further 29% of hybrids were moderately resistant to weevil attack. General combining ability effects (GCA) of lines used as male and female parents were significant (P