Impact of host plant resistance on the tritrophic interactions between wheat genotypes, Schizaphis graminum (Homoptera: Aphididae), and Coccinella septempunctata (Coleoptera: Coccinellidae) using molecular methods

Abstract

The objective of the current study was to evaluate the impact of wheat resistance on digestibility of Schizaphis graminum (Rondani) in the Coccinella septempunctata L. gut. Four wheat genotypes including an ancient wheat species (Einkorn) and three Iranian wheat genotypes (Azadi, Ommid, and Moghan2) were used. Einkorn was found to be a highly resistant species, while Azadi, Ommid, and Moghan2 were characterized as resistant, semiresistant, and susceptible genotypes, respectively, based on some biological parameters of S. graminum on these plants. Adult C. septempunctata starved for 24 h were fed one S. graminum reared on the selected wheat genotypes. A semiquantitative polymerase chain reaction technique using specific primers for the gene cytochrome oxidase II (COII) of S. graminum showed a significant effect of plant resistance on S. graminum DNA disappearance time. The DNA half-lives of S. graminum fed on Einkorn, Azadi, Ommid, and Moghan2 in C. septempunctata gut was 3.3, 3.6, 4.8, and 6.7 h, respectively. The findings suggest that digestibility of S. graminum fed on resistant plant genotypes is higher than those fed on susceptible plants because of the lighter weights and smaller sizes of the first. This phenomenon could result in faster ingestion of S. graminum by C. septempunctata on these resistant plants. It is also possible that some metabolites found differentially in Einkorn and Azadi genotypes may have affected S. graminum quality as a food for C. septempunctata. © 2013 Entomological Society of America.