Comparison of improved and local maize varieties in the Republic of Benin with emphasis on susceptibility to Sitophilus zeamais Motschulsky

Abstract

Experiments were conducted to verify differences in agronomic traits and susceptibility to the maize weevil, Sitophilus zeamais, in the field and in traditional maize storage systems between two international improved varieties, which have not been readily accepted by farmers in the Republic of Benin, one partially improved local variety and a local variety obtained from farmers. Factors responsible for differences in susceptibility and suitable screening methods for resistance to the maize weevil were also studied. In the first part of this study the varieties were compared in the field, during field drying and when stored using traditional techniques. The international improved varieties had significantly higher grain yield (60%) but had significantly poorer husk cover. The percentage of damaged ears following field drying, and the numbers of storage pests and grain weight loss after one month of storage were significantly higher in the international improved varieties presumably as a result of poorer husk cover. In the second part of this study the varieties were compared in a factorial arrangement of three storage forms (undehusked, dehusked and shelled grain) and two infestation methods (free and no-choice). Due to their superior husk cover quality, Benin varieties were significantly more resistant to weevils when infested in the traditional, undehusked storage form than international improved varieties. The smaller-grain, flinty, Benin varieties showed a significantly smaller number of F 1 generation weevils. A significant lengthening of the median development period (MDP) of weevils was observed when maize was stored as dehusked ears compared to shelled grain, particularly on the international improved varieties. No improved vs Benin variety comparisons interacted with free vs no-choice comparisons except for index of susceptibility in the undehusked storage form. Free choice infestations resulted in increased experimental error for number of F 1 weevils, presumably due to a clumped distribution of female weevils during oviposition. When the target farmer's storage system is undehusked ears, it is suggested to use no-choice infestation of undehusked ears as a screening method for elite candidate varieties. An assessment of husk quality and no-choice infestation of shelled grain and/or dehusked maize ears is suggested as more appropriate for preliminary screening of diverse germplasm.