Different maize varieties have greater impact on Tetranychus urticae (Acari: Tetranychidae) than GE maize expressing Cry3Bb1 insecticidal protein

Modern plant breeding techniques use genetic engineering methods to change certain plant traits that make them more resilient to a variety of biotic and abiotic stresses. Through these methods, the Cry genes have been inserted to crops to ensure insecticidal protection. In addition to genetically engineered (GE) crops expressing Cry proteins, there are numerous research organisations looking for new methods to control pests (Ricroch et al., 2016), such as incorporation of snowdrop lectin or plant protease inhibitors (Johnston et al., 1993, Down et al., 1996, Fitches et al., 1997, Azzouz et al., 2005). However, so far only crops expressing Cry proteins provide protection against pests commercially.

We focused on risk assessment of stacked GE maize MON 88017, in which the Cry3B1 gene from Bacillus thuringiensis subsp. kumamotoensis (six altered amino acids relative to the native protein) and the cp4 epsps gene from Agrobacterium tumefaciens strain CP4 are both expressed. Coleopteran-specific Cry3Bb1 protein ensures resistance to Diabrotica spp. (Coleoptera: Chrysomelidae), the destructive insect pests of maize in the North and South America evolving resistance to most integrated pest management (IPM) tactics (Spencer et al., 2014). Diabrotica virgifera virgifera LeConte has been rapidly expanding in Europe, thankfully without causing widespread economic damage (Bažok et al., 2021). Synthase CP4 EPSPS (5-enolpyruvylshikimate-3-phosphate) enables maize to tolerate herbicides based on glyphosate.

In North and South America, maize MON 88017 and its hybrids with other GE varieties are widely grown commercially. They are imported into the EU, where they are approved for use in food, feed, and other products, with authorization expiration dates ranging from 2023 to 2031, depending on the variety (European Commission, 2022). According to European Commission Regulation No. 1829/2003 (2003), the European Food Safety Authority (EFSA) must conduct a scientific risk assessment, which includes a systematic search and evaluation of the literature to assess potential new hazards, altered exposure, or new scientific uncertainties, and then make a recommendation for renewal or non-renewal of authorization (e.g., EFSA Panel on Genetically Modified Organisms, 2020). It is appropriate to keep introducing new scientific evidence that EFSA could reconsider in ERA and PMEM to ensure that there are no unacceptable adverse effects of imported GE maize on non-target organisms, including Tetranychus urticae Koch (Acari: Tetranychidae).

Tetranychus urticae is a widespread polyphagous herbivore that can feed on more than 1100 plant species in 140 plant families, including maize (Grbić et al., 2011). It can cause damage to maize, especially during drought stress (Bui et al., 2018). It is not considered an economically important maize pest, but is considered as a surrogate species in environmental risk assessment (ERA) and post-market environmental monitoring (PMEM) of GE maize imported into the European Union (EU) (Romeis et al., 2014).

Cry proteins from GE crops were found at high levels in T. urticae, with measured concentrations in the same order of magnitude as maize leaves expressing Cry3Bb1 (Li and Romeis, 2010, Álvarez-Alfageme et al., 2011, Svobodová et al., 2017), as well as Cry1Ab (Álvarez-Alfageme et al., 2008; 2011) or Cry1A.105, Cry1F, and Cry34Ab1 (Svobodová et al., 2017). Tetranychus urticae had 4–17 times more Cry1Ac than leaves in GE cotton (Esteves Filho et al., 2010, Meissle and Romeis, 2018). It can even reduce concentration of Cry1Ab and Cry3Bb1 in maize (Prager et al., 2014).

The high level of Cry proteins in T. urticae is explained by the fact that it sucks mesophyll cells, that have been shown to have high Cry protein concentrations (Dutton et al., 2004). As a result, T. urticae takes up a considerable amount of Cry protein compared to its body size. Thus, T. urticae has the highest recorded Cry protein concentrations among arthropods, which has implications for natural enemies that are also exposed to high levels of biologically active Cry protein (Obrist et al., 2006).

Despite the uptake of Cry proteins by T. urticae, there is no evidence that T. urticae and their predators are negatively affected by Cry proteins (Meissle and Romeis, 2009, Shu et al., 2018). However, there is report that Cry1Ab-expressing GE maize has a beneficial effect on the development and reproduction of the predator Orius majusculus (Reuter) (Hemiptera: Anthocoridae) which feeds on T. urticae (Lumbierres et al., 2012). In addition, females T. urticae preferred and laid significantly more eggs on GE eggplant leaves expressing Cry3Bb, while predatory mites Phytoseiulus persimilis A.-H. (Acari: Phytoseiidae) avoided GE-fed T. urticae (Zemková-Rovenská et al., 2005).

The present laboratory study was the first to evaluate the two-sex life history parameters of T. urticae feeding on GE maize expressing Cry3Bb1 protein, its near isogenic variety with and without insecticide protection, and two unrelated maize varieties. As described below, the insecticide was used as a standard treatment against Diabrotica spp. larvae. It was applied to the soil during sowing, several weeks before leaf harvest for our experiments, so we did not expect dramatic effects on T. urticae life history parameters. Comparing the effects of GE crop with non-GE and non-isogenic varieties of the same crop is important for investigating possible differences caused by differences between varieties of the same crop rather than by the use of modern plant breeding technique. The aim of the present study was to (1) review previous isolated reports on the effect of Cry proteins on T. urticae; (2) provide new scientific knowledge that could be used in reconsideration of authorization for the use of GE crops expressing Cry3Bb1 and their products on the EU market.

留言 (0)

沒有登入
gif