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Title: Evaluation of molecular markers for discriminating Gonatocerus morrilli (Hymenoptera: Mymaridae): a biological control agent for Homalodisca vitripennis

Author
item De Leon, Jesus
item MORGAN, DAVID - CDFA

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2007
Publication Date: 9/12/2007
Citation: De Leon, J.H., Morgan, D. 2007. Evaluation of molecular markers for discriminating Gonatocerus morrilli (Hymenoptera: Mymaridae): A biological control agent for Homalodisca vitripennis. Annals of the Entomological Society of America. 100(5):749-757.

Interpretive Summary: In the current study, molecular diagnostic markers developed to distinguish two very closely related natural enemies (Gonatocerus morrilli and G. walkerjonesi) of the glassy-winged sharpshooter were tested to evaluate whether post-release G. morrilli specimens could be discriminated in the field. G. walkerjonesi is native to California and G. morrilli was imported from Texas. A six-year (2002-2006) survey of post-release specimens of G. morrilli in California showed that G. morrilli was not detected in California due to a contamination of the ‘release’ colony by California’s own native species. After realizing that the ‘release’ colony was contaminated, the USDA, ARS, Beneficial Insects Research Unit (Weslaco, TX) provided the California Department of Food and Agriculture (CDFA) natural enemies (G. morrilli) from the origin (Texas) of the glassy-winged sharpshooter to restart the biological control program. Later, G. morrilli was detected at specific locations where the CDFA previously released G. morrilli from Texas, demonstrating the utility of the developed molecular diagnostic markers to monitor the establishment of natural enemies (G. morrilli).

Technical Abstract: We tested the utility of molecular markers for distinguishing between two closely related species, Gonatocerus morrilli (Howard) and G. walkerjonesi, S. Triapitsyn, to evaluate whether post-release G. morrilli specimens could be discriminated in the field. Initially, post-release specimens from California collected in 2002 and 2003 were analyzed. Amplification size of the internal transcribed spacer region (ITS2) demonstrated that all of the specimens were of the G. walkerjonesi ITS2 genotype. ISSR-PCR DNA fingerprinting of specimens from the original G. morrilli ‘release’ colony demonstrated that the DNA banding pattern was superimposable to that of G. walkerjonesi, confirming that the G. morrilli colony was contaminated. A new G. morrilli colony was initiated in the spring of 2005, and we continued to survey random post-release specimens from the 2004-2006 collections. As expected, from 2004 and most of 2005, only the G. walkerjonesi ITS2 genotype was detected. In the fall of 2005 and in the spring and fall of 2006, we detected the G. morrilli ITS2 genotype at sites where the new colony was previously released. Analyses with two newly developed ‘one-step’ species-specific ITS2 diagnostic markers were in accordance with the results of the markers described above, demonstrating the usefulness of the former studies of natural enemy establishment in biological control programs.