Breaking dormancy of GF305 peach and Real Fino apricot trees during the evaluation of resistance to sharka (plum pox potyvirus)

In countries like Spain or France, where sharka (plum pox potyvirus) is not as widespread as it is in Greece or Central Europe, experiments to evaluat e apricot resistance have to be carried out in controlled conditions using insect-proof greenhouses. One of the most important aspects of such growth conditions is the application of periods of artificially induced dormancy i n cold chambers so that tree species from temperate zones can undergo the n ecessary endodormancy-breaking step. In the experiment described in this pa per, GF305 peach and Real Fine apricot seedlings were exposed to artificial periods of cold (7 degreesC) and darkness lasting 3 to 12 weeks (between 5 04 and 2016 hours of cold) in order to determine the optimum period for sub sequent good vegetative growth. After removal from the cold chamber, the pl ants were placed in a greenhouse and weekly recordings were made of the per centage of leaf buds sprouted and vegetative growth. The optimal periods we re found to be 5 weeks (840 hours of cold) for GF305 and 8 weeks (1344 hour s of cold) for Real Fine.