Mapping of QTL associated with maize weevil resistance in tropical maize
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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 F-2 progeny derived from the cross CML290 (susceptible) x Muneng-8128 CO HC1-18-2-1-1 (resistant), were genotyped with 151 molecular markers. Resistance was evaluated using bioassays or) replicated F-2:3 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 F, 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 (sigma(2) (g)) for GD. Six QTL were detected with effects on GWL and explained 22% of sigma(2) and 47% of sigma(2) (g). Seven QTL (27% sigma(2) (p) and 78% sigma(2) (g)) were identified for DI and three QTL (10% sigma(2) (p) and 23% sigma(2) (g)) for AP. Both parents contributed resistance alleles. Genetic effects were mainly dominant (GD, GWL, and DI) and additive (AP). Quantitative trait loo x environment interaction was significant for 50% of the QTL. Since the identified QTL accounted for less than a third of (TIP, additional mapping populations are required for mapping MW susceptibility.
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