SOME SYMPTOMS OF STOCK-SCION INCOMPATIBILITY OF APRICOT VARIETIES ON PEACH SEEDLING ROOTSTOCK

In connection with apricot breeding, simple methods were sought for detecting stock-scion incompatibility between apricot varieties or seedling selections as scions and peach seedlings as rootstocks. Several incompatibility symptoms were studied, mainly those associated with structural weakness of the graft union. Smoothness of break at the union and discontinuity of wood and/or bark tissues were found to be reliable symptoms of incompatibility between apricot scion and peach rootstock. Highly significant correlations were found to exist between the above three observations. Examination of discontinuity of bark tissue is considered to be the simplest and, since it does not destroy the tree, the most practical method of determining the incompatibility status of apricot seedling selections.