Plums are considered as the most commonly grown stone-fruits in Europe and other temperate areas in the world. However this species is threatened by plum pox virus (PPV). The development of virus-resistant fruit-trees is considered as a major breakthrough in the successful use of biotechnology. The genetically modified (GM) HoneySweet Prunus domestica plum is a potential model for studying a perennial GM tree. HoneySweet is presently deregulated in the USA and this cultivar present a realistic model with which to address the arrival of a new fruit in European agriculture allowing for the practical evaluation of important questions concerning fruit quality and traceability. The programme action will provide scientists exchange opportunities supported by IRSES. The structuring action of the programme will develop two aspects of the ongoing research, notably the agronomic efficiency and genetic stability of HoneySweet in greenhouse, screenhouse containment and the field both with and without natural occurence of PPV. The proposal will aim to demonstrate the potential of GM fruit-trees for growers, develop the molecular tools and methodologies concerning virus resistance and notably the environmental effects studies in greenhouse compared with field natural conditions. Our objective is to evaluate the potential value of a GM fruit to reduce the threat of a quarentine pest like PPV and the dynamics of the climate change. These joint actions will provide a real consistency to the international cooperation between EU and USA: the exchange of scientist staff will connect the three research teams for three years with a collaborative network to better understand the long-term sustainable resistance displayed by GM fruit-trees through the present context of climate change which will impact the range of hosts and their pathogens and bring new hosts within the range of existing pathogens.