Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2007
Publication Date: 4/27/2007
Citation: Gitau, C., Gundersen, D.E., Pedroni, M.J., Dupas, S. 2007. Polydnavirus CrV1 gene expression in larvae of the African maize stem borer Busseola fusca (Fuller) parasitized by virulent and avirulent biotypes of the endoparasitoid Cotesia sesamiae (Cameron). Journal of Insect Physiology. 53(7):676-84 Interpretive Summary: Tiny wasps known as parasitoids have potential to control moth pests, such as caterpillars, of agricultural crops. The survival of many of these wasps is enhanced by a virus, called a polydnavirus, that is injected along with the wasp egg into the host caterpillar pest. In this study we use modern molecular techniques to analyze differences in the virus of two closely related wasps that are found on two different stem borer pests in sub-Saharan Africa. The two pests showed different responses to the wasps’ virus . The information obtained helps explain why one wasp may be effective for stem borer control while another closely related wasp is not. New molecular targets for the development of pest control products that target the pest are needed in order to find lasting solutions to control of cereal stem borers in Africa, and would be applicable to similar pest systems in the U.S. This information will be of interest to university and industry scientists who are interested in developing new virus-based strategies to control pests.
Technical Abstract: The braconid Cotesia sesamiae Cameron is the most common endoparasitoid of the stem borers Busseola fusca Fuller and Sesamia calamistis Hampson in sub-Saharan Africa. In Kenya, the C. sesamiae population from the western highlands completes development in B. fusca whereas the coastal population does not. Eggs laid by the latter population get encapsulated in B. fusca larvae but not S. calamistis. These C. sesamiae populations are hence herein referred to as virulent (CsV) and avirulent (CsAv), respectively. Busseola fusca larvae parasitized by the CsAv had frequently more encapsulated eggs at 24 hours post parasitism (pp) compared to earlierthe 6 and 12 hour time points. Expression of Cotesia rubecula (Marshall) polydnavirus (PDV), the C. sesamiae polydnavirus (PDV) CrV1 gene, associated with haemocyte inactivation in the Cotesia rubecula (Marshall)/Pieris rapae system, was detected in both B. fusca and S. calamistis parasitized by the CsV populations. Amplified CrV1 product was produced in S. calamistis fat body samples parasitized by the virulent CsKitale. There were no or merely faint amplified products on B. fusca fat body and hemolymph samples parasitized by the avirulent CsMombasa and CsKitui. The difference in expression of CrV1 gene in B. fusca and S. calamistis may explain the refractoriness of B. fusca towards C. sesamiae.