Long-term graft compatibility study of peach-almond hybrid and plum based rootstocks budded with European and Japanese plums

The introduction of some new rootstocks requires knowledge of the potential 'translocated' and 'localized' graft incompatibilities before releasing these rootstocks into the market. Trials were established at the Aula Dei Experimental Station (Zaragoza, Spain) to assess graft compatibility between five European plum (Prunus domestica L.) and six Japanese plum (Prunus salicina L.) cultivars with thirty-eight rootstocks belonging to peach × almond hybrids, as well as slow-growing, fast-growing and interspecific hybrid plum groups. Some of these rootstocks are under process of selection and others are commercial rootstocks already introduced into the European market. External visual diagnosis of the scion-rootstock graft combinations was performed by observing symptoms of the 'translocated' incompatibility in the nursery. Visual symptoms of 'translocated' incompatibility were only found on the Japanese plum cv. 'Golden Japan' budded on the plum-apricot hybrid AP-45. The 'localized' graft incompatibility was assessed after internal macroscopically examination of graft unions. In the case of the European plum cvs., 'President' and 'Reine Claude Tardive of Chambourcy' exhibited good graft compatibility with all the tested rootstocks, with the exception of 'President' budded on the pentaploid plum hybrid rootstock Damas GF 1869. 'Reine Claude Verte' cv. showed 'localized' incompatibility with Myrobalan B and Myrobalan GF 3-1 since the second year after budding. 'Stanley' cv. showed 'localized' incompatibility with the six evaluated peach × almond hybrid rootstocks, although it was compatible with all plum based rootstocks. In the case of Japanese plums, four cultivars ('Angeleno', 'Black Amber',' Delbarazur' and 'Songold') did not show any graft incompatibility, but 'Friar' showed 'localized' incompatibility on Myrobalan B. In the case of peach-almond and P. cerasifera based rootstocks (Adarcias, GF 677, Damas GF 1869, Myrobalan B, Myrobalan 29 C, Myrobalan GF 3-1 and Marianna GF 8-1), 'Golden Japan' trees showed similar symptoms to those caused by TomRV in Myrobalan and peach rootstocks and 'localized' incompatibility. Finally, this study confirmed the interest of P. insititia specie as well as several interspecific Prunus hybrids as a good source of rootstocks for the plum industry.