Resistance Risk Assessment ofSpodoptera frugiperda(Lepidoptera: Noctuidae) andDiatraea saccharalis(Lepidoptera: Crambidae) to Vip3Aa20 Insecticidal Protein Expressed in Corn

Abstract

Transgenic Agrisure Viptera 3 corn that expresses Cry1Ab, Vip3Aa20, and EPSPS proteins and Agrisure Viptera expressing Vip3Aa20 are used for control of Spodoptera frugiperda (J.E. Smith) and Diatraea saccharalis (F.) in Brazil. To support a resistance management program, resistance risk assessment studies were conducted to characterize the dose expression of Vip3Aa20 protein and level of control against these species. The Vip3Aa20 expression in Agrisure Viptera 3 and Agrisure Viptera decreased from V6 to V10 stage of growth. However, Vip3Aa20 expression in Agrisure Viptera 3 at V6 and V10 stages was 13- and 16-fold greater than Cry1Ab, respectively. The Vip3Aa20 expression in lyophilized tissue of Agrisure Viptera 3 and Agrisure Viptera diluted 25-fold in an artificial diet caused complete larval mortality of S. frugiperda and D. saccharalis. In contrast, lyophilized tissue of Bt11 at the same dilution does not provide complete mortality of these species. Agrisure Viptera 3 and Agrisure Viptera also caused a high level of mortality against S. frugiperda and D. saccharalis. Moreover, 100% mortality was observed for S. frugiperda larvae (neonates through fifth-instar larvae) when fed in corn with the Vip trait technology. Viptera corn achieves a high level of control against S. frugiperda and D. saccharalis providing a high dose, which is an important determination to support the refuge strategy for an effective resistance management program.

Functional dominance of different aged larvae of Bt-resistant Spodoptera frugiperda (Lepidoptera: Noctuidae) on transgenic maize expressing Vip3Aa20 protein

“…The expression of Cry1Ab and Vip3Aa20 proteins in Bt11 Â MIR162 Â GA21 maize did not increase FAW mortality when compared to MIR162 maize, showing that this Bt maize does not meet the basic assumption of the "gene pyramid" e each protein should present high toxicity against the same target pest (Ives et al, 2011;Carri ere et al, 2015). This can be explained by the lower expression of Cry1Ab than Vip3Aa20 in Bt11 Â MIR162 Â GA21 maize (Lynch et al, 2003;Bernardi et al, 2015a). In addition, Cry1Ab shows a low affinity to the midgut tissue of FAW, resulting in a low susceptibility to this Bt protein (Aranda et al, 1996;Fernandes et al, 2003;Mendes et al, 2009;Okumura et al, 2013;Bernardi et al, 2015a;Omoto et al, 2016).…”

“…This can be explained by the lower expression of Cry1Ab than Vip3Aa20 in Bt11 Â MIR162 Â GA21 maize (Lynch et al, 2003;Bernardi et al, 2015a). In addition, Cry1Ab shows a low affinity to the midgut tissue of FAW, resulting in a low susceptibility to this Bt protein (Aranda et al, 1996;Fernandes et al, 2003;Mendes et al, 2009;Okumura et al, 2013;Bernardi et al, 2015a;Omoto et al, 2016). FAW also shows faster degradation of Cry1Ab than more susceptible species (Miranda et al, 2001).…”

“…Based on this, the high-dose/refuge strategy has been suggested for resistance management of FAW to Vip3Aa20 maize in Brazil (Bernardi et al, 2015a). The success of this strategy is dependent, among other factors, on the high adoption of refuge areas (Gould, 1994;Tabashnik, 2008).…”

“…However, MIR162 and Bt11 Â MIR162 Â GA21 maize were used in less than 10% of the maize-growing area during the 2014e15 cropping season. Maize technologies expressing Bt proteins have been successful in controlling FAW (Okumura et al, 2013;Bernardi et al, 2015a). However, the continuous expression of insecticidal proteins in Bt plants imposes a strong selection pressure on target pest populations, favoring resistance evolution (McGaughey and Whalon, 1992).…”

Field‐evolved resistance by western corn rootworm to Cry34/35Ab1 and other Bacillus thuringiensis traits in transgenic maize

“…In addition to western corn rootworm, there are other examples of pest populations evolving resistance to one or more Bt toxins and subsequently being managed by pyramiding an additional Bt trait with the traits that have been compromised by resistance. Examples include corn earworm, Helicoverpa zea , in the United States and fall armyworm, Spodoptera frugiperda , in Brazil . In both cases, pest resistance to one or more Cry toxins has been countered by cultivation of Bt maize containing a pyramid of Bt toxin VIP3A with the Cry toxins that have been compromised by resistance.…”