Targeted identification of markers linked to malaria and filarioid nematode parasite resistance genes in the mosquito Aedes aegypti

Quantitative trait loci (QTL) have been identified for competence of the mo squito Aedes aegypti to transmit the avian malaria parasite Plasmodium gall inaceum and the human filarial parasite Brugia malayi. Efforts towards the map-based cloning of the associated genes are limited by the availability o f genetic markers for line-scale mapping of the QTL positions. Two F2 mosqu ito populations were subjected to bulked segregant analysis to identify ran dom amplified polymorphic DNA (RAPD)-PCR fragments linked with the major QT L determining susceptibility to both parasites. Individual mosquitoes for t he bulks were selected on the basis of their genotypes at restriction fragm ent length polymorphism (RFLP) loci tightly linked with the QTL. Pool-posit ive RAPD fragments were cloned and evaluated as RFLP markers. Of the 62 RAP D/RFLP fragments examined, 10 represented low-copy number sequences. Five o f these clones were linked with the major QTL for P. gallinaceum susceptibi lity (pgs1), of which one clone mapped within the flanking markers that def ine the QTL interval. The remaining five clones were linked with the major QTL for B. malayi susceptibility (fsb1), and again one clone mapped within the flanking markers that define the QTL interval. In addition, nine RAPD/R FLP fragments were isolated that seem to be of non-mosquito origin.