Graft establishment between compatible and incompatiblePrunusspp

Graft compatibility has been studied in apricot (prunus armeniaca L.) grafted on Prunus cerasifera Ehrh. Two apricot cultivars, one compatible and one incompatible on this rootstock, were selected for this study. In these species incompatibility is only manifested by tree breakdown at a late phase of the tree's life. The process of graft union formation was observed for the first month following grafting. No differences were found either in the process of healing or in its kinetics. Thus, callus proliferation, callus differentiation and vascular connections are established in the same way and at the same time in both compatible and incompatible grafts. However, clear differences exist in the level of differentiation of the callus produced. While in compatible grafts, callus quickly differentiates into cambium and vascular tissue, in incompatible grafts this differentiation is not complete and a portion of the tissue evolves into a parenchymatous tissue that coexists with the differentiated vascular tissue.