Roses are generally propagated by budding or grafting a scion cultivar onto a rootstock species, or by rooted cuttings.  More recently, tissue culture or more specifically micropropagation of R. hybrid cultivars and Rosa spp., offers an alternative method of multiplication (Pierik, 1987).

Preparation and disinfections

The initial step is to collect vegetative shoots from the rose(s) to be propagated, remove the leaves and cut the shoot into nodal sections about 0.75 inch (2 centimeters) long, each with an axillary bud.  Generally 2 to 3 buds exist at each node.  The sections must be surface sterilized in a solution of commercial laundry bleach diluted from 6.1% to 2.5% for about 20 minutes.  Little or no contamination will occur if this operation is done under vacuum.  The sections are then rinsed three times in sterile distilled water and then transferred to culture tubes or baby food jars (in a transfer chamber) containing modified Murashige and Skoog (1962) (MS) medium.

Murashige and Skoog medium

The MS medium is adjusted to three-quarter strength macro nutrients with Ammonium nitrate adjusted to 1856 parts per million (ppm) and full strength micro nutrients with zinc sulphate hepta hydrate and manganese sulphate altered to 21.2 and 33.8 (ppm) respectively (Arnold et. al., 1992).  Sucrose (3%), Phytagar (0.6%), benzylaminopurine (1 ppm) and naphthalene acetic acid (0.005 ppm) respectively are also added.  The medium pH is adjusted to 5.7 and autoclaved for 20 minutes at 121 degrees C.

Growth and rooting

After a two to three week period the bud growth from each nodal section is cut 1.5 cm long and transferred to test tubes or jars (containing the same medium as above) where multiplication will take place in about 3 weeks.  The new plantlets can then be further subcultured for multiplication or placed on the modified MS medium without benzylaminopurine but with the addition of an auxin e.g. indoleacetic acid, indolebutyric acid or naphthalene acetic acid for rooting.  The concentration of the auxin and the MS medium may depend on the cultivar of rose to be propagated/rooted (Arnold et al., 1995)

Transplant

Rooting occurs within 3 weeks and the rooted plantlets are then transferred to an inert medium such as vermiculite or comparable substrate and placed in a mist bed under shade for 2 weeks to be hardened-off.  After this time they can be placed in a shaded part of a greenhouse or growth room and fed with a dilute (about ¼ strength) soluble rose fertilizer for an additional 2 to 3 weeks.  The seedlings can then be transplanted to multipots or 2" square pots containing a good soil mixture.  The strength of the soluble fertilizer can be increased with time.

References