Abstract: Somatic embryos of English walnut (Juglans regia L.) were Agrobacterium-mediately transformed with the Trichoderma endochitinase gene ThEn242 under the control of a double 35 S CaMV promoter and Alfalfa Mosaic Virus leader sequence. The selectable marker gene neomycin phospotransferase Ⅱ (npt Ⅱ) driven by the nopaline synthase promoter was also used. A total of 41 putatively transformed somatic embryo lines were evaluated for expression of the npt Ⅱand ThEn-42 genes by PCR and multiplex PCR. All of the 41 somatic embryo selections expressed the npt Ⅱgene, among which 38 somatic embryo selections expressed the ThEn-42 gene. Analysis of chitinase activity by using a fluorometric assay showed dozens to 1 000-fold higher chitinase activity in transformed somatic embryos than that in non-transformed ones. All of the tested chitinase-postive somatic embryo lines analyzed by Southern blotting had an intact copy of the ThEn-42 gene. Chitinase expressing somatic embryos were further germinated and are being propagated for disease resistance assays.

Key words: Walnut (Juglans regia), Chitinase, Genetic transformation, Somatic embryos