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 lepidopteran pest of potato and is susceptible to the CryIA(b) insecticidal crystal protein of Bacillus thuringiensis. We introduced T-DNAs containing the TR2' promoter fused to the native truncated cryIA(b) gene (bt884) into the potato lines 'Kennebec' and 'Bintje' and T-DNAs containing the TR2' promoter fused to a modified truncated cryIA(b) gene (cryIAb6) into Kennebec and 'Yesmina'. A first selection of potato tuberworm resistant lines was made on the basis of enzyme-linked immunoassays, Manduca sexta (L.) leaf bioassays, and potato tuberworm leaf and tuber bioassays. In greenhouse trials, the selected potato lines carrying the bt884 gene showed significantly less potato tuberworm leaf damage than the control lines. However, the number and size of leaf tunnels increased with time. Similarly, the Yesmina lines expressing the cryIAb6 gene gave significantly less potato tuberworm leaf damage than the control line, which did not increase with time. In storage bioassays in which tubers were infested with neonate larvae and stored for approximate to 2 mo, all transgenic lines gave almost 100% potato tuberworm control. Tubers of cryIAb6 potato lines stored for up to 7 mo at 4 or 25 degrees C also resulted in 100% mortality.