Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2004
Publication Date: 9/15/2004
Citation: Galassi, E., Negri, P., Paris, R., Pratesi, D., Scorza, R. 2004. Recent advances towards apricot genetic transformation for resistance to plum pox virus. Meeting Proceedings. Interpretive Summary:
Technical Abstract: Engineering commercial cultivars with resistance genes is an especially arduous task for apricot (Prunus armeniaca L.), due to the generally low morphogenic ability of the explants, such as those from micropropagated material. On the other hand, zygotic tissues usually show a higher regeneration competence but their regeneration competence has not been rigorously tested. In previous transformation tests of both mature tissues and zygotic embryos of various apricot cultivars we observed that otherwise efficient methods for plant regeneration could be unsuitable for recovering transgenic plants. This was especially true when morphogenesis (either shoot organogenesis, or somatic embryogenesis) took place directly from the explant tissues and was not preceded by callus growth. In this study, improved regeneration protocols are described that have led to promising results on explants from both micropropagated shoots (cvs Boreale, San Castrese, Sungiant, and Vitillo) and germinated seeds (Boreale, Reale d'Imola, San Castrese, Sungiant, and Portici), inoculated with the A. tumefaciens strain EHA101, carrying the binary vector pGAPPV, with a PPV coat protein construct and transformation marker genes (nptII and GUS). Within the first two months of culture on selective media (kanamycin 100 mgl-1) the proliferation of GUS expressing callus was obtained, either accompanied or followed by the differentiation of shoot primordia. In comparison with the results of our previous experiments, the higher induction frequencies obtained, especially from leaf and stem explants of micropropagated shoots, can be attributed not only to the modified hormone composition of the culture media, but also to the pre-conditioning techniques applied to the source material, as well as to an improved decontamination method. Rather than its induction, the critical step of morphogenesis seems to be its continual expression, up to the recovery of fully developed shoots. This probably requires subsequent changes of the culture conditions. These specific conditions are currently under study.