Use of DNA arrays for molecular taxonomic and systematic studies of species within the Bactrocera Dorsalis complex

Abstract

Many species are known to be part of groupings of extremely closely related species known as species complexes. The Bactrocera dorsalis species complex contains at least 52 closely related species, many of which are major economic pests. In addition, many of them cannot be accurately identified using traditional approaches and very little is known about their systematic relationships. DNA markers may provide useful characters for both purposes. To develop a set of DNA markers, primers for per were designed from conserved coding regions of an actin gene (BdA1) previously characterized from B. dorsalis. These were used to amplify the intron region of this gene from known Bactrocera specimens including three species found within the complex and two from outside the complex. The amplification products obtained were cloned into plasmid vectors and sequenced. Analysis of these intron sequences revealed polymorphisms within and between species. From these, ten alleles were identified. Oligonucleotides corresponding to these alleles were synthesized and used to construct DNA arrays. The use of these arrays for genotyping and species identification was validated using a series of known specimens. This approach may also be useful for other applications including identification of unknown individuals, resolution of systematic relationships, monitoring routes of dispersal and assessing the origins of new infestations of these pests. The ability to rapidly and accurately identify species causing infestations may be a significant factor in reducing the damage and economic impact of such pests.