FIELD-EVALUATION OF EUROPEAN CORN-BORER CONTROL IN PROGENY OF 173 TRANSGENIC CORN EVENTS EXPRESSING AN INSECTICIDAL PROTEIN FROM BACILLUS-THURINGIENSIS

The European corn borer [ECB; Ostrinia nubilalis (Hubner)] is an economically significant pest of corn (Zea mays L.). The ability to routinely transform corn has broadened the control options available to include the introduction of resistance genes from sexually incompatible species. In this study, microprojectile bombardment was used to introduce synthetic versions of cryIA insecticidal protein genes from Bacillus thuringiensis subsp. kurstaki (Btk) into embryogenic tissue of the Hi-II (A188/B73 derivative) genotype of corn. Of 715 independent transgenic calli produced, 314 (44%) had insecticidal activity against tobacco hornworm (Manduca sexta L.) larvae. Plants were regenerated, self-pollinated when possible, and crossed to B73. First-generation progeny of 173 independent Btk-protein expressing calli were evaluated under field conditions with artificial ECB infestations in 1992 or 1993. Approximately half (89/173) segregated in a single-gene manner for resistance to first-generation ECB leaf-feeding damage. All of the 89 lines evaluated in 1992 or 1993 for resistance to second-generation ECB exhibited less stalk tunneling damage than the non-transgenic controls. In 1993, 44% (34/77) of the lines tested had less than or equal to 2.5 cm of tunneling, compared to severe damage (mean = 45.7 cm) in the B73 X Hi-II controls. Experiments are in progress to evaluate the effect of the introduced genes on yield and other agronomic properties.