Genetic variation and inheritance of diapause induction in two distinct voltine populations of the European Corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Crambidae)

Authors: IKTEN, CENGIZ - Akdeniz University; Skoda, Steven; HUNT, THOMAS - University Of Nebraska; MOLINA-OCHOA, JAMIE - Universidad De Colima; FOSTER, JOHN - University Of Nebraska

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2010
Publication Date: 5/8/2011
Citation: Ikten, C., Skoda, S.R., Hunt, T.E., Molina-Ochoa, J., Foster, J.E. 2011. Genetic variation and inheritance of diapause induction in two distinct voltine populations of the European Corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Crambidae). Annals of the Entomological Society of America. 104(3):567-575.

Interpretive Summary: The European Corn Borer (ECB) is an economically important pest that was introduced to the U.S. in the early 20th century. It has spread through most of the country and is among the most important pests in the Corn Belt states. For a recently introduced insect it is reasonable to expect little genetic variability, but this is not the case in ECB. One trait that ECB expresses is larval diapause, an adaptation where the insect is dormant (it arrests its development) during unfavorable periods; in this case to avoid freezing temperatures. Diapause is triggered by short day length, so one generation is typically active in northern latitudes whereas 3 or 4 generations occur in southern latitudes; these populations of ECB are said to be of different ecotypes. We developed a laboratory colony from geographically distant northern and southern populations, one colony from colder and one from warmer areas. Then, to determine inheritance of the trait, individual pair matings (crosses) were made between these two colonies; some of the resulting progeny were mated (backcrossed) to the parent stock while some were allowed to mate with their siblings. We learned that the male parent had more influence on the trait of the resulting progeny and that the trait of diapause was controlled by multiple, but not many (2 to 6), genes. Overall the results indicated that both ecotypes had adopted unique diapause responses, which ultimately lead to seasonal synchrony in their geographic area. These results help illuminate the genetic diversity of the pest organism and may help guide crop managers in decisions regarding pest control programs.

Technical Abstract: The European Corn Borer (ECB), Ostrinia nubilalis (Hübner), displays a larval diapause in response to short photoperiods, and is adapted to a variety of local conditions throughout North America. Hence, the effective photoperiod inducing larval diapause will differ among geographic populations. This study considers the inheritance of photoperiodic larval diapause induction by hybridization and backcrossing two latitudinally distinct populations of the ECB under a range of photoperiods representative of their respective locations: from 14:10 h L:D to16:8 h L:D. The ecotype adapted to a bivoltine habitat (southeast Nebraska) exhibited a shorter critical photoperiod (14.80 h) than the ecotype (15.33 h), originating from a univoltine habitat (northwestern Minnesota). Reciprocal F1 crosses exhibited intermediate values with indication of sex-linked inheritance. Additionally, the male parent had significantly more influence on diapause incidence of subsequent progenies than the female. The F2 and backcross progenies further supported the supposition that diapause response is a sex-linked inheritance. The minimum number of genes estimates, and the response from backcross progenies, suggest that diapause response of ECB larva may be controlled by only a few loci. The overall results indicated that both ecotypes had adopted unique diapause responses, which ultimately lead to seasonal synchrony in their ecosystems.