Mapping of QTL associated with maize weevil resistance in tropical maize
The maize weevil (MW), Sitophilus zeamais (Motsch.), is an important pest of stored maize (Zea mays L.) in tropical areas. Quantitative trait loci (QTL) associated with MW resistance were analyzed. A total of 163 F2 progeny derived from the cross CML290 (susceptible) x Muneng-8128 C0 HC1-18-2-1-1 (resistant), were genotyped with 151 molecular markers. Resistance was evaluated using bioassays on replicated F2:3 progenies. Grain damage (GD), grain weight losses (GWL), MW susceptibility index (Dobie index [DI]), and numbers of adult progeny (AP) were evaluated on grain from F2 lines across two environments. Grain hardness and pericarp/grain ratio were evaluated as putative components of resistance. Composite interval mapping was used for QTL analysis. Five QTL dispersed across the genome explained 28% of the phenotypic variance (p2) and 50% of the genotypic variance (g2) for GD. Six QTL were detected with effects on GWL and explained 22% of p2 and 47% of g2. Seven QTL (27% p2 and 78% g2) were identified for DI and three QTL (10% p2 and 23% g2) for AP. Both parents contributed resistance alleles. Genetic effects were mainly dominant (GD, GWL, and DI) and additive (AP). Quantitative trait loci x environment interaction was significant for 50% of the QTL. Since the identified QTL accounted for less than a third of p2, additional mapping populations are required for mapping MW susceptibility.