Identification of tri-trophic interactions using real-time PCR: Effect of the host plant resistance on detectable quantity of Schizaphis graminum DNA in the Coccinella septempunctata gut

The objective of the present study was to evaluate the interactions between wheat genotypes and C. septempunctata to control greenbug using real- time PCR. Three wheat genotypes including an ancient wheat species (Einkorn) and two Iranian wheat genotypes, Ommid and Moghan2 were used as highly resistant, semi-resistant and susceptible genotypes. Adults of the C. septempunctata, after 24 h starvation, were fed with definite numbers of S. graminum reared on the selected wheat genotypes, and their total genomic DNA was extracted. Real-time PCR technique using the specific primers for the gene cytochrome oxidase II (COII) of S. graminum was used. The results showed that the relative mean numbers of fed aphids were 14.77, 11.09 and 7.14 on Einkorn, Azadi and Moghan2, respectively, while the mean weight of aphids fed by ladybirds on each wheat genotype had no significant differences. Also, predator could significantly reduce the greenbug population fed on Einkorn and Azadi compare to Moghan2. The results of S/R ratios showed that the interactions between semi-resistant and resistant wheat genotypes with C. septempunctata are positive and semi-resistant genotypes with C. septempunctat could be used in IPM program of S. graminum.