DEVELOPMENT OF INSECT-RESISTANT TRANSGENIC CAULIFLOWER PLANTS EXPRESSING THE TRYPSIN-INHIBITOR GENE ISOLATED FROM LOCAL SWEET-POTATO

Agrobacterium-mediated transformation was used to introduce a trypsin inhibitor gene into Taiwan cauliflower (Brassica oleracea var, botryti s L.) cultivars. The TI gene was isolated from a well-adapted Taiwan s weet potato cultivar and was expected to be especially effective in co mbating local pests. In vitro regeneration studies indicated that 4-da y-old cauliflower seedling hypocotyl segments, pretreated with 2,4-dic hlorophenoxyacetic acid for 3 days and incubated on a silver-ion-conta ining shoot induction medium, gave regeneration rates greater than 95% . Optimum transformation conditions were determined. G418 selection at 15 mg/l was initiated 1 week after cocultivation, and the dose was do ubled 1 week later. Over 100 putative transgenic plants were produced. Transgenic status was confirmed by in vitro TI activity, and Southern and Western hybridization assays. The transgenic plants demonstrated in planta resistance to local insects to which the control plants were vulnerable.