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Title: Molecular markers discriminate closely related species, Encarsia diaspidicola and E. berlesei (Hymenoptera: Aphelinidae): Biocontrol candidate agents for white peach scale in Hawaii

Author
item De Leon, Jesus
item NEUMANN, GABOR - Collaborator
item Follett, Peter
item Hollingsworth, Robert

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2010
Publication Date: 6/2/2010
Citation: De Leon, J.H., Neumann, G., Follett, P.A., Hollingsworth, R.G. 2010. Molecular markers discriminate closely related species, Encarsia diaspidicola and E. berlesei (Hymenoptera: Aphelinidae): Biocontrol candidate agents for white peach scale in Hawaii. Journal of Economic Entomology. 103(3):908-916.

Interpretive Summary: We genetically characterized Encarsia diapsidicola Silvestri and E. berlesei Howard (Hymenoptera: Aphelinidae) by two molecular methods: phylogenetic analysis of the cytochrome oxidase subunit I gene (COI) and ISSR-PCR DNA fingerprinting. These two closely related endoparasitoids are candidate biological control agents for the white peach scale, Pseudaulacaspis pentagona Targioni-Tozetti (Hemiptera: Diaspididae), in Hawaii. We developed species-specific COI molecular markers that discriminated the two species and we tested the utility of the E. diaspidicola-specific COI marker to detect parasitism of white peach scale. The COI sequence data uncovered 46 base pair differences between the two Encarsia spp. The level of COI genetic divergence between the two species was 9.7% and the two clustered into their own clade on a parsimonious phylogram. ISSR-PCR readily discriminated the two Encarsia spp. as each was observed with fixed species-specific banding patterns. The COI molecular markers were specific for each species as cross-reactivity was not observed with non-target species. The E. diaspidicola-specific COI markers were successful at detecting parasitism of white peach scale by E. diaspidicola by 24 h. Both molecular marker types successfully discriminated the two Encarsia spp., while the COI markers will be useful as tools to assess levels of parasitism in the field and to study competitive interactions between parasitoids.

Technical Abstract: The white peach scale, Pseudaulacaspis pentagona Targioni-Tozetti (Hemiptera: Diaspididae), is a serious economic pest of papaya in Hawaii. The endoparasitoid Encarsia diaspidicola Silvestri (Hymenoptera: Aphelinidae) was imported from Samoa into quarantine in Hawaii to be evaluated for potential release against this pest. Another potential candidate is closely related E. berlesei Howard. These two species have been considered synonyms by some workers. We genetically characterized E. diapsidicola and E. berlesei by phylogenetic analysis of the cytochrome oxidase subunit I gene (COI) and ISSR-PCR DNA fingerprinting. We developed species-specific COI molecular markers that could distinguish the two species. We tested the utility of the E. diaspidicola-specific COI markers to detect parasitism of white peach scale. The COI sequence data uncovered 46 base pair differences between the two Encarsia spp., and eight of these led to amino acid substitutions. The level of COI genetic divergence between the two species was 9.7%, and the two clustered into their own clade on a parsimonious phylogram. DNA fingerprinting readily discriminated the two Encarsia spp., as each was observed with fixed species-specific banding patterns, making ISSR-PCR an efficient molecular tool. The COI markers were specific for each species as cross-reactivity was not observed with non-target species. The E. diaspidicola-specific COI markers were successful at detecting parasitism of white peach scale by E. diaspidicola by 24 h. These molecular markers will be useful as a tool to assess levels of parasitism in the field and to study competitive interactions between parasitoids.