|Weathersbee iii, Albert|
Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/10/2003
Publication Date: 3/1/2004
Citation: Weathersbee, A.A., Jr., Shufran, K.A., Panchal, T.D., Dang, P.M. Evans, G.A. Detection and differentiation of parasitoids (Hymenoptera: Aphidiidae and Aphelinidae) of the brown citrus aphid (Homoptera: Aphididae): Species-specific PCR amplification of 18S rDNA. Annals of the Entomological Society of America. 97(2):286-292. Interpretive Summary: The brown citrus aphid, Toxoptera citricida (Kirkaldy), is a serious pest of citrus because it damages young growing shoots of citrus and vectors citrus tristeza virus. Control strategies rely on the use of native and imported parasitoids to maintain this pest at low levels. We have selected native Lysiphlebus testaceipes (Cresson) for high levels of parasitism against brown citrus aphid, previously a poor host for this parasitoid in nature. The foreign parasitoids, Aphelinus gossypii Timberlake and Lipolexis scutelaris Mackauer also have been introduced to control brown citrus aphid. Monitoring the levels of parasitism caused by each of several parasitoid species attacking the same host is difficult, time consuming, and often inaccurate because the parasitoids must be reared-out or dissected in the laboratory. We developed a simple and quick molecular approach to detect and identify these parasitoids within single parasitized brown citrus aphids.
Technical Abstract: The brown citrus aphid, Toxoptera citricida (Kirkaldy), is an important pest of Florida citriculture because it causes feeding damage to citrus and vectors citrus tristeza virus. Parasitoids commonly recovered from brown citrus aphid in Florida include Lysiphlebus testaceipes (Cresson), Lipolexis scutellaris Mackauer, and Aphelinus gossypii Timberlake. Monitoring the levels of parasitism caused by each species is difficult because the parasitoids must be reared-out or dissected in the laboratory. A simple and quick molecular approach was developed to detect and distinguish the parasitoids developing within the host aphid. Total genomic DNA was extracted from the brown citrus aphid and each of the three parasitoids and the 18S rRNA gene of each species was amplified by polymerase chain reaction (PCR). The PCR products were sequenced to obtain complete gene sequences for each species. The variable regions V2 of the genes were used to design species-specific primers for detecting and differentiating the three parasitoids. The species-specific PCR amplifications discriminated the parasitoid DNAs from each other and from the host DNA. Detection of L. testaceipes DNA within the host aphid was possible in 8% of samples during the first 2 h after parasitoid oviposition; in 66% of samples after 24 h; in 94% of samples after 48 h; and in 100% of samples after 72 h. The PCR approach described in this experiment provides earlier and more precise detection of parasitism and determination of species than rearing or dissection methods.