First report on the generation ofPrunus domestica× P. armeniacainterspecific hybrids with hypersensitivity resistance to thePlum pox virus

Prunus domestica (European plum) and Prunus armeniaca (apricot) are related species which can be hybridized. However, there are only very few reports on true interspecific hybrids between P. domestica and P. armeniaca. These hybrids must not be confused with the so called pluots or plumcots which are hybrids between P. salicina (Japanese plum) and P. armeniaca. In 2005, a program for breeding interspecific hybrids between P. domestica and P. armeniaca was initiated at Technische Universitat Munchen. As female parent, a P. domestica clone with hypersensitivity resistance to Plum pox virus (PPV) was used. As male parent, apricot cultivars with different degrees of susceptibility to PPV were chosen. Several interspecific hybrids were obtained. Leaves, shoots and fruits of the seedlings are intermediate between European plum and apricot. The seedlings were tested for their resistance to PPV. Interspecific hybrids with strong resistance to PPV could be obtained. To the best of our knowledge, this is the first report on the generation of PPV resistant hybrids between European plum and apricot. The hybrids could help to better understand the genes which are involved in hypersensitivity resistance to PPV. Moreover, the interspecific hybrid can be used for transferring the PPV resistance to the apricot genome by repeatedly backcrossing them with apricot. The interspecific hybrids represent a new kind of fruit species as the outer and inner fruit traits are intermediate between the parent species.