Novel Vip3A Bacillus thuringiensis (Bt) maize approaches high-dose efficacy against Helicoverpa zea (Lepidoptera: Noctuidae) under field conditions: Implications for resistance management

Abstract

Sweet corn, Zea mays L., transformed to express a novel vegetative insecticidal protein, Vip3A (event MIR162, Syngenta Seeds, Inc..), produced by the bacterium, Bacillus thuringiensis (Bt), was evaluated over four field seasons in Maryland and two field seasons in Minnesota for efficacy against the corn earworm, Helicoverpa zea (Boddie). Hybrids expressing the Vip3A protein and pyramided in hybrids also expressing the Cry1Ab Bt protein (event Bt11, ATTRIBUTE(®), Syngenta Seeds, Inc.) were compared to hybrids expressing only Cry1Ab or to genetically similar non-Bt hybrids each year. In addition to H. zea efficacy, results for Ostrinia nubilalis (Hübner) and Spodoptera frugiperda (J.E. Smith) are presented. Over all years and locations, the non-Bt hybrids, without insecticide protection, averaged between 43 and 100% ears infested with a range of 0.24 to 1.74 H. zea larvae per ear. By comparison, in the pyramided Vip3A x Cry1Ab hybrids, no larvae were found and only minimal kernel damage (likely due to other insect pests) was recorded. Hybrids expressing only Cry1Ab incurred a moderate level of H. zea feeding damage, with surviving larvae mostly limited to the first or second instar as a result of previously documented growth inhibition from Cry1Ab. These results suggest that the Vip3A protein, pyramided with Cry1Ab, appears to provide the first "high-dose" under field conditions and will be valuable for ongoing resistance management.

Bacterial Vegetative Insecticidal Proteins (Vip) from Entomopathogenic Bacteria

“…p ϭCHEMICALSEARCH:30#p). Both events were pyramided with cry1Ab (VipCot Vip3Aa plus mCry1Ab and Agrisure Viptera Vip3Aa plus Cry1Ab) and later with cry1Fa (VipCot Vip3Aa plus Cry1Ac plus Cry1Fa and Agrisure Viptera Vip3Aa plus Cry1Ab plus Cry1Fa) to confer wider and more robust protection against Lepidoptera (113)(114)(115). Furthermore, corn event MIR162 has been stacked with other cry genes expressing proteins that are active against Coleoptera (Cry3A and eCry3.1Ab) to confer protection against these two insect orders (116).…”

Transgenic cowpeas (Vigna unguiculata L. Walp) expressing Bacillus thuringiensis Vip3Ba protein are protected against the Maruca pod borer (Maruca vitrata)

“…Line 709A is a cowpea line transformed with the cry1Ab gene (positive control) lepidopteran pests compared to cotton expressing a single Cry gene (Cry1Ac) (Bommireddy et al 2011). In maize, a pyramided (Vip3A and Cry1Ab) hybrid was shown to control key lepidopteran pests (Burkness et al 2010). Similarly, the pyramiding of a drought tolerance gene with a Cry2Aa2 gene led to insect resistance and enhanced water efficiency in pepper (Zhu et al 2015).…”

Attack and defense movements involved in the interaction of Spodoptera frugiperda and Helicoverpa zea (Lepidoptera: Noctuidae)

“…This is the case involving the larvae of S. frugiperda and H. zea which occupy the same feeding guild in maize and often explore maize ears simultaneously (Burkness et al 2010;Siebert et al 2012), allowing possible interactions between the species. For H. zea, moths oviposit on maize silks, and larvae, as soon as hatch, they move on to feed on kernels (Burkness et al 2010). Cannibalistic and carnivorous behavior, inclusive in interfamilial predation of H. zea, was reported in late instar larvae occupying the same maize ears (Capinera 2005;Boyd et al 2008).…”