Development of transgenic cabbage (Brassica oleracea var. Capitata) for insect resistance by Agrobacterium tumefaciens-mediated transformation

Transgenic head cabbage (Brassica oleracea var. capitata), resistant to dia mondback moth (Plutella xylostella) larvae, was developed through Agrobacte rium tumefaciens-mediated transformation with Bacillus thuringiensis (Bt) c ry genes using a modified procedure. Factors important for transformation i ncluded cabbage cultivar; preculture: and coculture of explants on a callus initiation medium; use of appropriate amount; and delay in initial applica tion of selective agents. A total of 15 independent transformed lines with over 100 plants were obtained from several transformation experiments, repr esenting an overall transformation efficiency of similar to 1%. Cabbage pla nts transformed with a synthetic Bt gene, cry1Ab3, were all resistant to la rvae of the diamondback moth, whereas all plants transgenic for cry11a3, a wild-type Bt gene, were susceptible. As a first step towards testing the hy pothesis that reduced exposure of Bt to target insects would delay the evol ution of insect resistance to Bt, cry1Ab3 expression was put under the tran scriptional control of the soybean wound-inducible vspB promoter and transg enic cabbage was obtained. Insect bioassay showed that such plants were all resistant to diamondback moth even without induction for the expression of Bt.