Early detection of graft incompatibility in sweet cherry by internode association and callus fusion techniques

The scion-rootstock incompatibility is one of the most common problems in fruit trees. The study evaluated predicted compatibility or incompatibility by internode association and callus fusion techniques. Two factorial experiments were laid out with an incompletely randomized design with three replications. Treatment includes the first factor, four levels of sweet cherry cultivars (‘Bing’, ‘Takdaneh’, ‘Siyah Mashhad’ and ‘Adli’), and the second factor, four levels of rootstocks (‘Gisela-5’, ‘Gisela-6’, ‘Mahaleb’ (M-168) and ‘GF-305’). Results showed significant differences in total phenolic content, peroxidase and starch content in internode association and callus fusion experiments. ‘GF-305’ rootstock (incompatible) had the lowest success rate of grafts on all cultivars, while ‘Gisela-6’ rootstock showed the highest success rate of grafts on ‘Siyah Mashhad’ and ‘Bing’ cultivars. Both experiments showed that in incompatible grafts, an increase in total phenol content and peroxidase activity and a decrease in grafts’ success rate were observed. The degree of compatibility was significantly and positively correlated with the success rate of grafts while significantly and negatively correlated with total phenol content and peroxidase activity. In both experiments, no clear trend was observed regarding starch content and the success rate of grafts. The regression analysis results showed that phenol compounds in both experiments significantly affected the graft's success rate and the degree of compatibility. Our findings lead to the conclusion that phenolic compounds (mostly) and peroxidase activity can be used to pre-screen for incompatible grafts. Moreover, the callus fusion technique can be a quick way to predict (in)compatibility of graft in sweet cherry.