Early antibiotic selection and efficient rooting and acclimatization improve the production of transgenic plum plants (Prunus domestica L.)

We describe here an improved system for routinely developing transgenic plum plants (Prunus domestica L.) through the use of Agrobacterium tumefaciens. The production of non-transformed "escapes" has been virtually eliminated, and rates of plant establishment in the greenhouse have been dramatically improved. The system is based on the regeneration of shoots from hypocotyls extracted from mature seed. The shoot regeneration medium is Murashige and Skoog (MS) salts and vitamins supplemented with 7.5 M thidiazuron and 0.25 M indole-butyric acid. Transferring the explants after co-cultivation to shoot regeneration medium containing 80 mg l^-1 of kanamycin and 300 mg l^-1 of Timentin reduced the total number of regenerated shoots without affecting the transformation rate. Transformation rates using the described system averaged 1.2% of the hypocotyl slices producing transgenic plants, with a range of 0–4.2%. The transgenic shoots rooted at a rate of 90% on half-strength MS salts and vitamins supplemented with 5 M -naphthaleneacetic acid and 0.01 M kinetin. Plantlets were transferred to a greenhouse directly from culture tubes with a 90% average survival.Abbreviations ACO1 Prunus persica 1-aminocyclopropane-1-carboxylate oxidase - CP Coat protein - GUS -Glucuronidase - NPTII Neomycin phosphotransferase II - PCR Polymerase chain reaction - PDV Prune dwarf virus - PNRSV Prunus necrotic ringspot virus - SGM Shoot growth medium - SRM Shoot regeneration medium - TIM Timentin (SmithKline Beecham, Philadelphia) - TomRSV Tomato ringspot virusCommunicated by K.K. Kamo