E. Sacco, M. Savona, M. Antonetti, A. Grassotti, P.L. Pasqualetto, B. Ruffoni
Hydrangea is a genus of about 75 species of flowering plants native to southern and eastern Asia and North and South America. Most are shrubs 1-3 tall, but some are small trees and others lianas. Hydrangea (Hortensia) is a very popular ornamental plant for gardens and recently it was commercialised for the production of cut flowers. A wide selection of 78 genotypes of several species was investigated with the aim of extending cut flower or pot plant production. Among them, 6 genotypes with new characters were chosen to undergo micropropagation in order to increase their propagation potential. Small shoots and buds were cut in October, April and May from vegetative branches and sterilized with a sequence of ethanol, NaOCl, distilled and sterile water. For the establishment of the vitro cultures, MS salt medium with vitamins added with BA (0.5 mg L-1) and sucrose (30 g L-1) was used. Severe fungi contamination appeared in October in 4 out of 6 genotypes so other treatments were added to ensure the asepsis of the explants. It was possible to obtain 4 aseptic clones; among them the genotype Hydrangea quercifolia ‘Snow Queen’ (SQ) showed good propagation potential and gave the best propagation rate, more than 7 shoot per explant, after culture with BA 1 mg L-1. All the experiments were carried out with 35 µmol m-2 s-1 PPFD and a photoperiod of 16 h of light/day. A rate of 100% rooting occurred in vitro using NAA 0.5 mg L-1. 95% rooting was achieved in ‘Direct rooting’ after dipping of the microcuttings in K-IBA 5000 ppm and contemporary transfer in the acclimatization greenhouse; after 21 days, complete and acclimatized plantlets could be used for commercial purposes. Callus induction experiments were done with leaf fragments from in vitro and in vivo plants with the aim to produce cells able to differentiate somatic embryos. At the first observation, callus developed best from 2,4-D 0.5 mg L-1 + Kin 0.5 mg L-1 or 2,4-D 2 mg L-1 alone. The material was then transferred in growth regulator free substrate in order to achieve eventual somatic embryogenesis potential.
Sacco, E., Savona, M., Antonetti, M., Grassotti, A., Pasqualetto, P.L. and Ruffoni, B. (2012). IN VITRO PROPAGATION AND REGENERATION OF SEVERAL HYDRANGEA GENOTYPES. Acta Hortic. 937, 565-572
DOI: 10.17660/ActaHortic.2012.937.68
Hydrangea quercifolia 'Snow Queen', BA, micropropagation, K-IBA, acclimatization

Acta Horticulturae