PHTHORIMAEA OPERCULELLA (LEPIDOPTERA, GELECHIIDAE) RESISTANCE IN POTATO BY EXPRESSION OF THE BACILLUS-THURINGIENSIS CRYIA(B) INSECTICIDAL CRYSTAL PROTEIN

The potato tuberworm, Phthorimaea operculella (Zeller), is a primary l epidopteran pest of potato and is susceptible to the CryIA(b) insectic idal crystal protein of Bacillus thuringiensis. We introduced T-DNAs c ontaining the TR2' promoter fused to the native truncated cryIA(b) gen e (bt884) into the potato lines 'Kennebec' and 'Bintje' and T-DNAs con taining the TR2' promoter fused to a modified truncated cryIA(b) gene (cryIAb6) into Kennebec and 'Yesmina'. A first selection of potato tub erworm resistant lines was made on the basis of enzyme-linked immunoas says, Manduca sexta (L.) leaf bioassays, and potato tuberworm leaf and tuber bioassays. In greenhouse trials, the selected potato lines carr ying the bt884 gene showed significantly less potato tuberworm leaf da mage than the control lines. However, the number and size of leaf tunn els increased with time. Similarly, the Yesmina lines expressing the c ryIAb6 gene gave significantly less potato tuberworm leaf damage than the control line, which did not increase with time. In storage bioassa ys in which tubers were infested with neonate larvae and stored for ap proximate to 2 mo, all transgenic lines gave almost 100% potato tuberw orm control. Tubers of cryIAb6 potato lines stored for up to 7 mo at 4 or 25 degrees C also resulted in 100% mortality.