Experimental approaches on in vitro grafting in Prunus armeniaca and P. spinosa

An in vitro grafting protocol was established with micropropagated shoots of the apricot cultivars ‘Caldesi’ and ‘Alb 3’, (apricot selection from ‘Cricot’ x ‘NAJ 53’ cross) and the P. spinosa seedling ‘PS123’(open pollination from a wild tree). Compatible combinations (homografts) were ascertained by considering vascular continuity between scion and stock, as determined by fast toluidine blue staining procedure, and by restoration of phloem connections as determined by application of 5(6)-carboxyfluorescein (CF) to the scion. 15 days after graft establishment, the differentiation of new xylematic tissue resulting in unification of the vascular elements between stock and scion was observed in all the genotypes which, moreover, showed restoration of active phloem. High correlation between the differentiation of new xylem and the differentiation of new phloem at the graft point was found. Graft-take, however, did not correlate with the scion-stock compatibility, in that heterograft-take was high but did not reflect xylematic continuity or phloematic transport, which were not established in any of the tested scion-stock combination. The use of rooted shoots as rootstock resulted in unsuccessful graft technique.