Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2008
Publication Date: 5/11/2009
Citation: Fukova, I., Neven, L.G., Barcenas, N.M., Gund, N.A., Dalikova, M. 2009. Rapid Assessment of the Sex of Codling Moth, Cydia pomonella. Journal of Applied Entomology 133:249-261.
Interpretive Summary: Codling moth is a major pest of apples in the United States and Europe. This pest is the target of intensive control programs which includes the release of sterile moths to reduce populations. Scientists from the USDA-ARS collaborated with scientists from the Czech Republic and Germany to develop a method to determine the sex of early developmental stages of codling moth. This method used specific sequences on the codling moth female-specific chromosome, the W-chromosome to identify females. The period gene, which is present on the Z-chromosome, a sex chromosome present in both sexes, was used as a positive control to test the quality of the DNA tested. The development of this method will facilitate the identification of embryos to isolate female-specific messages that can be used in the development of genetic sexing lines of codling moth. Genetic sexing lines will reduce the cost and improve the efficacy of the sterile insect technique through the release of only sterile males.
Technical Abstract: Two different methods were tested to identify the sex of the early developmental stages of the codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) with a WZ/ZZ (female/male) sex chromosome system. Firstly, it was shown that the sex of all larval stages can be easily determined by the presence or absence of sex chromatin, which is formed by the female–specific W chromosome in interphase nuclei. This trait can also be used to identify the sex of newly hatched larvae but it does require care and accuracy. Secondly, a new sexing technique was developed based on a molecular marker of the codling moth W chromosome. Flanking regions of an earlier described W-specific sequence (CpW2) were isolated and sequenced and a 2.74 kb sequence (CpW2-EcoRI), specific for the W chromosome, was obtained. Several PCR tests were conducted, which confirmed that the CpW2-EcoRI sequence is a reliable marker for the sex identification in codling moth samples of different geographical origin. In addition, a fragment of a codling moth gene, period (Cpper) was isolated and sequenced. Results of Southern hybridization of the Cpper probe with female and male genomic DNA suggested that the Cpper gene is located on the Z chromosome. Then a multiplex PCR assay was developed, which co-amplified the CpW2-EcoRI sequence to identify the W chromosome and the Z-linked Cpper sequence, which served as a positive control of accurate processing of tested samples. The multiplex PCR provides an easy and rapid identification of the sex of embryos and early larval instars of the codling moth.