Anatomical graft compatibility study between apricot cultivars and different plum based rootstocks

Abstract

The introduction of some new rootstocks requires knowledge of the extent and nature of (in)-compatibility reactions before releasing these rootstocks on the market, providing both nursery and fruit growers valuable information about the risk of weak unions (‘localized’ incompatibility). Therefore, trials were established at Aula Dei Experimental Station (Zaragoza, Spain) nurseries to assess graft compatibility between four apricot cultivars (‘Búlida’, ‘Canino’, ‘Moniquí’ and ‘Paviot’) and twenty-one plum based rootstocks. In general, ‘Paviot’ cv. exhibited good graft compatibility with all tested rootstocks, although several discontinuities in the bark were observed in the case of Ademir, Myrobalan 713 AD and Miral 3278 AD. ‘Búlida’ cv. was graft compatible with all rootstocks, with the exception of Marianna 2624 and Miral 3278 AD. They showed vascular and wood discontinuities in their graft unions. In the case of the exigent cvs. group (‘Canino’ and ‘Moniquí’) graft incompatibility was observed, in general, with all fast-growing plum rootstocks (mainly Prunus cerasifera) and some interspecific hybrid rootstocks. On the contrary, the hexaploid P. insititia plums showed good graft compatibility with all apricot cvs., with the exception of Montizo and PM 140 AD rootstocks. A positive and significant correlation (r = 0.628, P ≤ 0.01) of graft incompatibility occurrence was found between the first or second year and the fourth year after grafting. Finally, the study of the ratio ‘stem circumference / union circumference’ showed that most of the scion-rootstock graft combinations presenting a ratio inferior to 0.8 showed discontinuities in the bark and/or in the wood at the graft union.