Characterisation of tritrophic effects of DAS-59122-7 maizeon the seven-spotted ladybird (Coccinella septempunctata)feeding on the bird cherry-oat aphid (Rhopalosiphum padi)
Abstract: The long-term effects on the fecundity and fertility of Coccinella septempunctatapreying on Rhopalosiphum padi living on maize containing genetic event 59122 (Herculex® RWBt maize, DAS-59122-7), its isogenic counterpart (PR36D79) and three other commercial Pioneerhybrids (37M34, 37N01 and 36V52) were characterised during and following pollen shed. Theconcentration of the Cry34Ab1 and Cry35Ab1 binary toxin was analysed by commercialenzyme-linked immunosorbent assays (ELISAs). Concentrations of Cry34Ab1 and Cry35Ab1 inR1 phenological stage green leaf blades were 81.1 ± 17.7 and 75.1 ± 11.9ng/mg lyophilised dryweight, respectively. Pollen contained 47.4 ± 12.3ng Cry34Ab1/mg fresh weight, whereasconcentrations of Cry35Ab1 were below the limit of detection of the ELISA (< 0.12ng/mg).Maize plants in the V14-R1 phase (8 from each variety) under mesh cages (full plant isolator)were pre-infested with approximately 500 aphids at least one week prior to placing 20 newlyemerged L1 C. septempunctata larvae onto each plant. Larval to adult development wasmonitored every 3-4 days. Remaining within the isolators, the adults were allowed to prey on R.padi feeding on the respective maize variety and to copulate under semi-field conditions for twomore weeks after adult emergence. In mid-September (2010) entire plants with isolators weretransferred into the laboratory, where sexing and weighing of the ladybirds was performed.Additionally, in the laboratory under a long photoperiod (L:D 16:8, 25°C) females were pairedwith two males under a cob isolator. Under each isolator, a cob and adjacent ear leaves fixed in awater flask were infested with R. padi. C. septempunctata mating groups were monitored and thefrequency of egg laying was recorded daily. Results from this study demonstrate that for alltreatment groups, the sex ratio was 45:55 female/male, and the female average weight (45.3 ±6.2mg) was not significantly different across varieties. Additionally, no significant differenceswere observed during the tested period in either fecundity or fertility across varieties (the DAS-59122-7 treatment group averaged 25 eggs/female and 56% fertility; the isogenic or commercialhybrid treatment groups averaged 24-34 egg/female and 58-77% fertility).