Relationship between seed physical traits and maize weevil (Sitophilus zeamais) damage parameters in selected Quality Protein Maize (QPM) varieties

The vulnerability of Quality Protein Maize (QPM) varieties to Sitophilus zeamais Motschulsky attack causes substantial postharvest loss to farmers. A study was conducted in the Institute of Agricultural Research and Training, Moor Plantation, Ibadan, Nigeria, to evaluate the response of the newly released QPM and High Protein Maize (HPM) varieties of the Institute to Sitophilus zeamais infestation. Five varieties comprising two QPM (ART/98/SW6-OB and ILE 1-OB); one HPM (ART/98/SW1) and two conventional maize varieties (KU1414SR/SR and TZPB) were used for the experiment. Two hundred seeds of each variety were artificially infested with eggs of Sitophilus zeamais and arranged in a completely randomized design with three replicates under two storage conditions (dark room and opened well-ventilated room) for three months. Data were collected on seed traits and weevil damage parameters. Results showed that there were significant differences among the varieties and between the storage conditions for most of the traits. Both QPM varieties significantly harbored Sitophilus zeamais as the number of emerged adult insects at 3 weeks after infestation (WAI), damage rating, total number of insects at termination and grain weight loss were highest in both, though higher in ILE 1-OB. The conventional inbred line (KU1414SR/SR) experienced less damage. Grain weight loss was positively correlated with insect damage rating, while seed coat thickness was negatively correlated with grain weight loss and other damage parameters. The released QPM varieties of the Institute are highly susceptible to Sitophilius zeamais infestation and therefore require genetic improvement. Seed coat thickness and damage ratings are important traits to be considered in improvement programmes for resistance to Sitophilus zeamais in QPM varieties.