Field performance of MON 94637 and laboratory evidence supporting a Bt pyramiding strategy against key lepidopteran pests in Brazil

BACKGROUND: Pyramided Bt genes in crops have been widely adopted to delay insect resistance evolution worldwide. The genetically modified (GM) soybean (Glycine max [L.] Merril) MON 94637, expressing the Bt proteins Cry1A.2 and Cry1B.2, was designed to improve the level of protection against defoliating caterpillars (Lepidoptera). In this study, we performed laboratory and field studies to assess the efficacy of the Cry1A.2 and Cry1B.2 proteins in MON 94637 expressed together and in a five-Bt protein pyramid in soybean against the main lepidopteran pests attacking this crop. RESULTS: Soybean leaf tissue expressing a combination of Cry1A.2, Cry1B.2 (MON 94637) or, Cry1A.2, Cry1B.2, Cry1A.105, Cry2Ab2, and Cry1Ac (MON 94637 × MON 87751 × MON 87701 × MON 94313 × MON 89788) caused 100% mortality of neonates of Chrysodeixis includens, Anticarsia gemmatalis, and Spodoptera eridania across a range of plant growth stages. This Bt soybean also showed high efficacy in bioassays against Cry1Ac-resistant colonies of Rachiplusia nu and Crocidosema sp. In field tests, MON 96437 soybean (Cry1A.2 and Cry1B.2) was highly effective against lepidopteran pest species as assessed by reductions in defoliation rate and pest incidence in comparison to non-Bt across several locations in Brazil. CONCLUSIONS: Leaf bioassays showed that GM soybean expressing Cry1A.2, Cry1B.2, Cry1A.105, Cry2Ab2, and Cry1Ac will be highly effective against key lepidopteran pests in soybean in Brazil. This is the first pyramid of five-Bt protein biotechnology soybean, representing a unique innovation for tropical agriculture.