Isolation and characterization by direct amplification of length polymorphisms (DALP) of codominant genetic markers with mendelian inheritance in Neoseiulus californicus (Acari : Phytoseiidae)

We report the first application of a new method designed to isolate polymor phic loci in any organism, the direct amplification of length polymorphism. Five polymorphic loci were readily isolated in the predatory mite Neoseiul us californicus (Acari: Phytoseiidae). Two to five alleles were identified among 46 isofemale lines based on fragment size variation due to micro-dele tions/insertions. Genotyping F1 and F2 progenies from controlled heterogame tic crosses and backcrosses allowed to establish the Mendelian inheritance of these alleles, their codominance, and pairwise recombination rates. Nucl eotidic sequence divergence due to single base substitution was also found in the flanking regions of the polymorphism. We discuss the usefulness of t hese markers in studies of reproductive systems as well as population genet ics, in particular, in mite species where the amount of DNA or richness in microsatellites could be limiting factors in the isolation of polymorphic l oci.