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Title: MOLECULAR MARKERS FOR IDENTIFICATION OF THE HYPERPARASITOIDS DENDROCERUS CARPENTERI AND ALLOXYSTA XANTHOPIS IN LYSIPHLEBUS TESTACEIPES PARASITIZING CEREAL APHIDS

Author
item CHEN, YI - ALDERSON-BRODDUS COLLEGE
item PIKE, KEITH - WASHINGTON STATE UNIV
item Greenstone, Matthew
item Shufran, Kevin

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2005
Publication Date: 4/1/2006
Citation: Chen, Y., Pike, K.S., Greenstone, M.H., Shufran, K.A. 2006. Molecular markers for identification of the hyperparasitoids Dendrocerus carpenteri and Alloxysta xanthopsis in Lysiphlebus testaceipes parasitizing cereal aphids. Biocontrol. 51(2):183-194.

Interpretive Summary: Several species of aphids are limiting factors in wheat and sorghum production in the Great Plains. An alternative to chemical controls is the reliance on naturally occurring parasitoid wasps that lay their egg inside the aphid. The parasitoid wasp egg hatches into a larva and eats the inside of the aphid which kills it. The larval wasp pupates inside the dead aphid and then will emerge as an adult wasp. This type of parasitoid that attacks the aphid is called a primary parasitoid. Molecular DNA markers have been used to estimate the population level of primary parasitoids attacking the aphids. This is important in managing the pest aphids because detecting a certain level of parasitoids can mean that a chemical pesticide is not needed. However, a complicating factor exists in the aphid-primary parasitoid system. A number of other parasitoid wasp species (called secondary or hyper-parasitoids) attack and kill the primary parasitoid developing inside the aphid. The presence of secondary parasitoids can alter the effectiveness of aphid control by reducing the numbers of primary parasitoids. To better evaluate aphid parasitism and improve molecular probes to detect aphid parasitoids, we developed DNA markers to detect the secondary parasitoids attacking primary parasitoids inside the aphids. Thus, we can get a very accurate population estimate of parasitism and improve the decision making process on whether to use chemical controls or simply rely on the natural biological control by the primary parasitoid wasp.

Technical Abstract: Molecular markers have been developed to detect the presence of primary parasitoids in cereal aphids for use in estimating parasitism rates. However, the presence of secondary parasitoids (hyperparasitoids) may lead to underestimates of primary parasitism rates. Therefore, molecular markers to detect hyperparasitoids were developed. The 16S ribosomal RNA mitochondrial gene was amplified by polymerase chain reaction (PCR) and sequenced from two secondary parasitoid species, Dendrocerus carpenteri (Curtis) and Alloxysta xanthopa (Ashmead), four geographic isolates of the primary parasitoid, Lysiphlebus testaceipes (Cresson), and six cereal aphid species: bird cherry-oat aphid, Rhopalosiphum padi (L.); corn leaf aphid, Rhopalosiphum maidis (Fitch); English grain aphid, Sitobion avenae (F.); greenbug, Schizaphis graminum (Rondani); Russian wheat aphid, Diuraphis noxia (Kurdjumov); and yellow sugarcane aphid, Sipha flava (Forbes). Species-specific PCR primers were designed for each insect on the basis of these 16S rRNA gene sequences. Amplification of template DNA, followed by agarose gel electrophoresis, successfully distinguished D. carpenteri and A. xanthopa from all four isolates of L. testaceipes and all six cereal aphid species.