Genetically modified soybean expressing insecticidal protein (Cry1Ac): Management risk and perspectives

Abstract

A Bt soybean has been recently developed, thus, efficiently regulating the populations of major lepidopteran pests. However, in other cases, these benefits have been reduced or lost because of the rapid evolution of pest resistance to the Bt toxins in transgenic crops. When pest populations are exposed to Bt crops and to refuges (non-Bt plants), the evolution of resistance is governed by the fitness of resistant individuals relative to susceptible individuals for both the presence and absence of Bt toxins. One major ecological concern regarding the biosafety of Bt crops on the environment is their potential effects on non-target organisms, especially predators and parasitoids that play an important role in pest control. This information is important for supporting insect resistance management (IRM) programs and for improving agricultural practices in a crop production system with Bt plants. Before the use of Bt plants for insect pest control in Brazil is adopted, IRM programs should be established to ensure the sustainability of this technology for integrated pest management (IPM). This review presents data on Bt soybean and lepidopteran pests as well as on the importance of natural enemies as a form of biological control, and applications for IPM and IRM.

Specific binding of Bacillus thuringiensis Cry1Ea toxin, and Cry1Ac and Cry1Fa competition analyses in Anticarsia gemmatalis and Chrysodeixis includens

“…A. gemmatalis and C. includens are two important soybean pests that at present are controlled with transgenic soybean varieties that express the B. thuringiensis insecticidal protein Cry1Ac 5,12,41,42 . Also, other soybean events expressing the Bt proteins Cry1Ac, Cry1F, Cry2A and the chimera Cry1A105 (that combines the domains I and II of Cry1Ab or Cry1Ac, and domain III of Cry1F) either alone or pyramided, have been approved for cultivation in many countries 11 .…”

Convergence of Bar and Cry1Ac Mutant Genes in Soybean Confers Synergistic Resistance to Herbicide and Lepidopteran Insects

“…Thus, stable inheritance of the bar transgene is important to obtain commercially useful soybean transgenic lines. Several reviews have documented herbicide and insect resistance in transgenic crops that are important agronomic traits (Lutz et al, 2001;Singh et al, 2016;Martins-Salles et al, 2017;Romeis et al, 2019). Useful genes can be introduced to crops without leading to interference with normal plant metabolism (Block et al, 1995;Gao et al, 2016;Gupta et al, 2020).…”

“…Insect pests cause 20–30% biomass losses in soybean ( Glycine max L.) worldwide (Bengyella et al, 2018 ). In the Lepidoptera order, Helicoverpa armigera Hubner ( H. armigera ) is the main insect pest of several crops such as cotton, chickpea, and soybean (Homrich et al, 2012 ; Martins-Salles et al, 2017 ). The application of chemical insecticides is a common measure to control insect pests in soybean fields.…”

“…Evidence from laboratory bioassay (Stewart et al, 1996 ) and field experiments (Walker et al, 2000 ) shows that transgenic soybean lines with high expression levels of the cry1Ac gene significantly increase larval mortality. However, Bt transgenic plants often show variable resistance responses against insect pests because of lower cry genes expression (Martins-Salles et al, 2017 ). Thus, there is a need to develop transgenic lines with elaborated gene stacking to limit the emergence of insect resistance.…”

“…Thus, there is a need to develop transgenic lines with elaborated gene stacking to limit the emergence of insect resistance. Furthermore, recombinant fusion proteins and domain swapping can be leveraged to protection against insects (Nachimuthu and Kumar, 2004 ; Martins-Salles et al, 2017 ). Hence, the challenge is to develop insect-resistant lines by increasing and stabilizing the level of the cry1Ac gene in target tissues or use a fusion protein to confer complete protection against insects.…”