Effects of Transgenic Cry1Ac + CpTI Cotton on Non-Target Mealybug Pest Ferrisia virgata and Its Predator Cryptolaemus montrouzieri

Abstract

Recently, several invasive mealybugs (Hemiptera: Pseudococcidae) have rapidly spread to Asia and have become a serious threat to the production of cotton including transgenic cotton. Thus far, studies have mainly focused on the effects of mealybugs on non-transgenic cotton, without fully considering their effects on transgenic cotton and trophic interactions. Therefore, investigating the potential effects of mealybugs on transgenic cotton and their key natural enemies is vitally important. A first study on the effects of transgenic cotton on a non-target mealybug, Ferrisia virgata (Cockerell) (Hemiptera: Pseudococcidae) was performed by comparing its development, survival and body weight on transgenic cotton leaves expressing Cry1Ac (Bt toxin) + CpTI (Cowpea Trypsin Inhibitor) with those on its near-isogenic non-transgenic line. Furthermore, the development, survival, body weight, fecundity, adult longevity and feeding preference of the mealybug predator Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) was assessed when fed F. virgata maintained on transgenic cotton. In order to investigate potential transfer of Cry1Ac and CpTI proteins via the food chain, protein levels in cotton leaves, mealybugs and ladybirds were quantified. Experimental results showed that F. virgata could infest this bivalent transgenic cotton. No significant differences were observed in the physiological parameters of the predator C. montrouzieri offered F. virgata reared on transgenic cotton or its near-isogenic line. Cry1Ac and CpTI proteins were detected in transgenic cotton leaves, but no detectable levels of both proteins were present in the mealybug or its predator when reared on transgenic cotton leaves. Our bioassays indicated that transgenic cotton poses a negligible risk to the predatory coccinellid C. montrouzieri via its prey, the mealybug F. virgata.

Impact of Bt cotton expressing single (Cry1Ac) and dual toxins (Cry1Ac and Cry2Ab) on the fitness of the predator Chrysoperla zastrowi sillemi (Esben-Petersen): prey-mediated tri-trophic analysis

“…Bt protein concentrations in cotton leaves, insect prey and predator were measured, using sandwich ELISA, using quantiplate kits (Wu et al 2014). The concentration of Cry1Ac protein was measured, using Cry 1Ab/ Cry1Ac kit (AP 003 QT V50) and Cry2Ab using Cry2A kit (AP 005 QT BC V50) of ENVIROLOGIX 500 Riverside Industrial Parkway Portland, ME, USA.…”

“…Simon et al (2006) reported that Cry1Ab or Cry2Ab toxins did not have detrimental effects on C. carnea when ingested either directly or through prey as the larval midgut lacks specific receptors for these proteins. No prey-mediated effects of Cry proteins have also been reported in other predatory species including the coccinellids (Wu et al 2014), the rove beetles (Garcia et al 2010) and the wolf spiders (Niu et al 2017).…”

Dietary and phylogenetic correlates of digestive trypsin activity in insect pests

“…Evolution of resistance to a single trypsin inhibitor in populations of pest insects could be a problem for successful implementation of transgenic plants. It can be overcome by the use of genes for multifunctional inhibitors (Luo et al., ) and fusion proteins (Sainsbury et al., ) or by pyramiding genes (Dunse et al., ; Senthilkumar et al., ; Liu et al., ; Diaz & Santamaria, ; Wu et al., ). Understanding the adaptive responses of pest insects contributes to selection of the appropriate combination of digestive enzyme inhibitors (Dunse et al., ; Spit et al., ).…”

“…Despite concern that transgenic plants may affect non‐target organisms, negative effects of trypsin inhibitors on other herbivores and natural enemies of pest insects have rarely been recorded under field conditions due to low expression of insecticidal proteins and/or adaptive responses of parasitoids and predators (Schlüter et al., ). If there are no negative effects on natural enemies or if a plant is transformed with an inhibitor of proteases not present in their gut (Álvarez‐Alfageme et al., ; Wu et al., ), then application of methods of biological control may provide additional protection of transgenic plants and delay evolution of resistant pests.…”

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

“…'Prey quality-mediated effects' can be avoided in experiments by using a herbivore that is not susceptible to the plantexpressed Cry toxins (i.e., a non-susceptible herbivore) or by using a strain of the target organism that is highly resistant to the particular toxin (i.e., a Bt-resistant herbivore). The use of a non-susceptible herbivore or a Bt-resistant herbivore ensures that the herbivores themselves are not adversely affected by the ingested toxin (Chen et al, 2008;Lawo et al, 2010;Li et al, 2011;Tian et al, 2014;Wu et al, 2014;Su et al, 2015).…”