Screening for new sources of resistance to Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) infestation in stored maize genotypes

New sources of maize resistance to the maize weevil, Sitophilus zeamais infestation are indispensable in successful breeding programs against post harvest grain damage. The study investigated the characters and mechanisms that confer resistance to weevil infestation using twenty elite maize genotypes. Detailed morphological and physical studies were conducted on whole-maize grain. The grain hull was separated from the whole-maize grain with a locally-fabricated machine and subjected to chemical analysis. Resistance was assessed at 33 days post infestation using weevil mortality, weevil survival, percent grain damage, weight of grain powder, percent weight loss and oviposition as indices rated on a scale developed by the present study. The resistant genotypes identified, particularly 2000SYNEE-WSTR and TZBRELD3C5 with very high degree of resistance should be used singly or best in an integrated pest management system for the control of S. zeamais infestation in stored maize. Though increases in the physical properties of grain hardness, weight, length and width increased varietal resistance, it was found that the bases of resistance were increased chemical attributes of phenolic acid, trypsin inhibitor and crude fiber while the bases of susceptibility were increased protein and starch. Characters that conferred resistance on the tested genotypes were found in the grain hull. The study identified antibiosis and antixenosis as the mechanisms of maize post harvest resistance to S. zeamais infestation.