Genetic modification of the commercial apple cultivars Gala, Golden Delicious and Elstar via an Agrobacterium tumefaciens-mediated transformation method

Modern biotechnological techniques, including genetic modification, offer important tools to plant breeders for the introduction of resistance genes into a fruit crop such as apple. However, the transformation methods necessary to generate transgenic apple plants from commercial cultivars are often tedious or unavailable. In this article we report on an Agrobacterium tumefaciens-mediated transformation method for the commercial apple cultivars Gala, Golden Delicious and Elstar. Southern blot analysis confirmed the integration of both selection and marker genes, nptII and gus, with one or two copies per genome being present. For transformation, leaf segments were co-cultivated with a supervirulent Aglobacterium strain, containing the nptII and gus genes. GUS-positive shoots were induced on calli which were able to proliferate-on kanamycin-containing medium. The transformation efficiencies, based on the number of GUS-positive shoots, were 0.7-8% per leaf explant for Gala, 0.2-6% for Golden Delicious and 0.4-0.8% for Elstar. The GUS-positive clones tested were able to form roots on kanamycin-containing medium and developed into transgenic plants. The use of this transformation method for the introduction of antimicrobial genes is discussed.