|DE Leon, Jesus|
|Morgan, David - CA DEPT. FOOD & AGRIC.|
Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: October 9, 2007
Publication Date: December 12, 2007
Citation: De Leon, J.H., Morgan, D.J. 2007. Evaluation of molecular markers for discriminating Gonaterocerus morrilli: A biological control agent imported from the origin of the glassy-winged sharpshooter. Proc. CDFA Pierce's Disease Research Symposium. pp. 81-85. Interpretive Summary: In the current study we evaluated molecular markers for their utility to detect and discriminate post release Gonatocerus morrilli specimens from a very closely related species, G. walkerjonesi. G. morrilli was imported from Texas and G. walkerjonesi is native to California (CA). Before the markers were developed, it was very difficult to distinguish the two species to monitor the success of the biological control program. A survey of specimens stored in ethanol collected by the California Department of Food and Agriculture (CDFA) from 2002 thru 2006, determined that G. morrilli did not establish. Only the native species G. walkerjonesi was recovered. An analysis of the G. morrilli ‘release’ colony uncovered a colony contamination, that is, the colony was not G. morrilli, but rather, G. walkerjonesi. ARS-Weslaco (J. de León) sent the CDFA G. morrilli from Texas, the origin of the GWSS that invaded CA. After the new G. morrilli colony was released, we were able to detect G. morrilli in the field. G. morrilli is now one of the most recovered imported natural enemies in certain regions of southern CA, confirming the importance of collecting natural enemies from the origin of the pest. These molecular markers were used in 2007 to determine the purity of the release colony. The results confirmed that the colony was pure or it was the correct species, G. morrilli.
Technical Abstract: We examined the utility of molecular markers for discriminating between two very closely related species, Gonatocerus morrilli (Howard) (imported from Texas) and G. walkerjonesi S. Triapitsyn (native to California), to determine whether post-release G. morrilli specimens could be detected and discriminated in the field. We started by analyzing post-release specimens collected in 2002 and 2003. 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 experiments of specimens from the original G. morrilli ‘release’ colony showed that the DNA banding patterns were superimposable to that of the native G. walkerjonesi, confirming a colony contamination. 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 agreement with the results of the markers described above, demonstrating their usefulness in aiding the biological control program. G. morrilli is now one of the most recovered imported natural enemies in certain regions of California.