Early detection of graft incompatibility in apricot (Prunus armeniaca) using in vitro techniques.

Graft compatibility has been studied in vitro using callus tissues of apricot (Prunus armeniaca) and different Prunus rootstocks to form scion/rootstock combinations with different degrees of graft compatibility. In these species, incompatibility is manifested by a breakdown of the trees at the union area that can occur some years after grafting. Here, the possibility of obtaining an early detection method to determine graft incompatibility is explored by callus fusion in vitro. The adhesion of the two callus partners, the development of the cells at the contact surface (cell arrangement, intensity of cell-wall staining), and the presence of lipid and phenolic compounds have been studied during the first 3 weeks after grafting in both compatible and incompatible combinations. Differences were observed at the second and the third week of callus co-culture in most of the characters determined, although these differences were present as early as the first week in the case of phenolic compounds. The behaviour of the grafts grown in vitro was correlated to that of the same combinations in the field, suggesting that callus fusion in vitro could be a possible and reliable method for an early detection of graft incompatibility in different Prunus combinations.