Does Bt maize expressing Cry1Ac protein have adverse effects on the parasitoid Macrocentrus cingulum (Hymenoptera: Braconidae)?

Abstract

The potential effects of insect-resistant, genetically engineered (GE) crops on non-target organisms, especially on predators and parasitoids, must be evaluated before their commercial cultivation. The effects of GE maize that produces Cry1Ac toxin on the parasitoid Macrocentrus cingulum were assessed by direct bioassay and indirect bioassay. In the indirect bioassay, parasitism rate, cocoon weight and the number of M. cingulum progeny produced per host were significantly reduced when M. cingulum-parasitized Cry1Ac-susceptible Ostrinia furnacalis were fed a diet containing purified Cry1Ac; however, life-table parameters of M. cingulum were not adversely affected when the same assay was performed with Cry1Ac-resistant O. furnacalis. These results indicated that the detrimental effects detected with a Cry1Ac-susceptible host were mediated by poor host quality. In a direct bioassay, no difference in life-table parameters were detected when M. cingulum adults were directly fed a 20% honey solution with or without Cry1Ac; however, survival and longevity were significantly reduced when M. cingulum adults were fed a honey solution containing potassium arsenate, which was used as a positive control. The stability and bioactivity of Cry1Ac toxin in the food sources and Cry1Ac toxin uptake by the host insect and parasitoid were confirmed by enzyme-linked immunosorbent assay and sensitive-insect bioassays. Our results demonstrate that M. cingulum is not sensitive to Cry1Ac toxin at concentrations exceeding those encountered in Bacillus thuringiensis maize fields. This study also demonstrates the power of using resistant hosts when assessing the risk of genetically modified plants on non-target organisms and will be useful for assessing other non-target impacts.

The Asian corn borer Ostrinia furnacalis feeding increases the direct and indirect defence of mid‐whorl stage commercial maize in the field

“…Ostrinia furnacalis larvae were reared on modified diets (Zhou et al ., ) for 3–4 generations in a controlled incubator with 27 ± 1 °C, 70%–80% relative humidity (RH) and a photoperiod of 16 h. M. cingulum colony was maintained following Wang et al . (2017b).…”

“…Ostrinia furnacalis and the parasitoid wasp M. cingulum were obtained from a laboratory colony from the IPP, CAAS, Beijing. Ostrinia furnacalis larvae were reared on modified diets (Zhou et al, 1980) for 3-4 generations in a controlled incubator with 27 AE 1°C, 70%-80% relative humidity (RH) and a photoperiod of 16 h. M. cingulum colony was maintained following Wang et al (2017b).…”

Impact of transgenic soybean expressing Cry1Ac and Cry1F proteins on the non-target arthropod community associated with soybean in Brazil

“…Problem formulation conducted as part of the ERA for DAS-81419-2 soybean considered the familiarity of the mode of action for Cry proteins [ 30 – 33 ], the narrow spectrum of activity for Cry proteins [ 2 , 34 ], the demonstrated history of safe use for Bt crops [ 35 , 36 ] and the agronomic equivalence of DAS-81419-2 soybean to conventional soybean [ 37 ]. Previous laboratory studies using purified protein, lyophilized plant tissue, and/or leaf feeding bioassay in direct or indirect exposure test systems demonstrated no adverse effects of Cry1Ac or Cry1F on NTA [ 38 – 45 ]. Comprehensive reviews [ 2 , 46 ] and meta-analyses [ 18 , 47 , 48 ] of NTA laboratory and field data have concluded the safety of transgenic Bt proteins across the spectrum of commercialized events and cropping systems, including cotton and maize, in which they have been deployed.…”

Tri-Trophic Impacts of Bt-Transgenic Maize on Parasitoid Size and Fluctuating Asymmetry in Native vs. Novel Host-Parasitoid Interactions in East Africa

“…Insect-resistant transgenic plants may kill immature parasitoids indirectly by killing their host [ 16 ], or by rendering the host nutritionally inferior or unsuitable [ 17 ]. Parasitoids can also be sensitive to changes in nectar composition [ 18 ] or volatile profile [ 19 , 20 ] that occur in transgenic plants.…”