VARIATION IN RESISTANCE OF MEXICAN LANDRACES OF MAIZE TO MAIZE WEEVILSITOPHILUS-ZEAMAIS, IN RELATION TO TAXONOMIC AND BIOCHEMICAL PARAMETERS

Accessions representing twenty eight landraces of maize were assessed for susceptibility to the maize weevil, Sitophilus zeamais in standard ized resistance tests. Susceptibility parameters such as weight loss o f grain, number of insect progeny produced, the Dobie index of suscept ibility, and oviposition on grain were found to vary significantly by genotype, with exceptional resistance found in accessions representing the Naltel, Chapalote and Palomero landraces. As in improved genotype s, susceptibility was negatively correlated to phenolic and protein co ntent of the variety tested but positively correlated to moisture cont ent. A detailed analysis of the phenolics revealed the presence of dif erulate which may contribute to mechanical resistance of the seed by c ross-linking of cell wall hemicelluloses. A canonical discriminant ana lysis of the resistance data suggests that most of the five landrace g roupings are significantly different. The ancient indigenous and prehi storic mestisos groupings are sources of resistant genotypes.