Bacillus thuringiensis Cry1Ca expressed in maize protects against feeding damage from susceptible and Cry1F-resistant Spodoptera frugiperda

Bacillus thuringiensis insecticidal protein Cry1Fa is an important component of commercial varieties of insect resistant transgenic corn owing to its ability to protect against feeding damage by several economically important Lepidopteran pests including Ostrinia nubilalis (Hübner), Diatraea grandiosella (Dyar), Spodoptera frugiperda (J.E. Smith), Agrotis ipsilon (Hufnagel), Striacosta albicosta (Smith) and several other stalk borers.  Spodoptera frugiperda (FAW) field resistance to Cry1Fa corn was reported in Puerto Rico in 2006.  Commercial cultivation of Cry1Fa corn in Puerto Rico was suspended in response to the occurrence of Cry1F-resistant FAW.  This report describes the characterization of Cry1Ca as a candidate to prevent or delay development of Cry1Fa resistance in FAW when Cry1Ca and Cry1Fa are deployed as stacked traits in transgenic corn. We report here the biological activity and receptor competitive binding profiles for Cry1Fa and Cry1Ca.  We demonstrate that Cry1Ca controls susceptible and Cry1Fa-resistant populations of FAW. We also show that Cry1Ca and Cry1Fa do not compete for interactions at binding sites in FAW midgut brush-border membrane vesicles. Furthermore, we demonstrate reduced feeding damage of FAW and Cry1Fa-resistant FAW on Cry1Ca corn. These data support the pyramiding of Cry1Ca and Cry1Fa to delay the development of resistance in FAW.