Genetic changes within an aphid clone: homogenization of rDNA intergenic spacers after insecticide selection

Authors

Kevin A. Shufran, USDA-ARS
Z. B. Mayo, Univesity of Nebraska - LincolnFollow
Teresa Crease, University of Guelph, Guelph, Ontario N1G 2W1, Canada

Document Type

Article

Date of this Version

April 2003

Comments

Published in Biological Journal of the Linnean Society, 2003, 79, 101–105. With 4 figures.

Abstract

A single asexual maternal lineage (i.e. clone) of the greenbug aphid, Schizaphis graminum (Rondani) was repeatedly selected with the insecticide disulfoton (O,O-diethyl S-[2-(ethylthio)ethyl] phosphorodioate). A parallel colony of the non-selected clone was also maintained. After approximately 200 generations (4 years) of continuous selection, both the selected and non-selected clones were assayed for changes in intergenic spacer (IGS) length variants of the rRNA cistron. No changes in sets of IGS variants were detected in the non-selected clone. However, the selected clone was found to have lost three variants present in the non-selected clone. This probably occurred by unequal cross-over between sister chromatids, whereby the cistron became homogenized by an increase of frequency of two smaller variants. This documents a large-scale genetic change occurring within the rRNA cistron in a parthenogenetically reproducing aphid.