S05 - Session O2 - Anatomical study of union formation in T-budded Rosa gallica 'Duchesse d'Angoulême' and ground cover rose ‘Mercury’ on selected rootstocks

Authors: Marta Joanna Monder *, Przemyslaw Babelewski

T-budding is a widespread method of propagation of rose cultivars. However, the genus Rosa is characterized by high morphological, phenological and genetic variability, which can be manifested by physiological incompatibility. Rootstocks typically originate from only two species: Eurasian Rosa canina and Asian Rosa multiflora , while the budded cultivars can be taxonomically distant. The aim of this research was to observe the anatomical structure of bud union. The Rosa canina 'Inermis', 'Pfänders', 'Schmid's Ideal'; R. laxa and R. multiflora were T-budded with the buds of two cultivars: Rosa gallica 'Duchesse d'Angouleme' [the scions were prepared from shoots: (i) 14-18 days after petal shedding, and (ii) non-flowering in current vegetative season] and ground cover 'Mercury 2000' [the scions were cut from shoots with opened flowers] in the last week of July. The budded rootstock necks were harvested for anatomical research after three months. The anatomical studies focused on the site of union formation between rootstock and bud in relation to anatomical disturbances in this process. Transverse sections were made in relation to the rootstock root axis in the place of the 'T' cut and bud union. Parenchyma and phloem cells were present at the place of component contact in both cultivars. In contrast to 'Mercury 2000', distinctive anomalies in bud union were observed in 'Duchesse d'Angouleme' regardless of the rootstock used. Cross-sections often showed clusters in the form of cells with an indistinct growth direction, layers of cork, necrosis, and voids in the region of component contact. The numerous necroses visible on the sections indicated anomalies in the union formation of the components. Anomalies in union formation were responsible for the low percentage of living buds on rootstock necks and low percentage of good quality shrubs in rose nursery production.