Propagating ash for cash
The European Ash, Fraxinus excelsior, is a fast growing and resilient tree which enjoys a wide natural distribution and produces valuable timber. Ash is tough and hard-wearing, doesn't split and has traditionally been employed to make spears and the handles of weapons and tools. In more recent times the wood has been used to produce furniture, flooring, snooker cues and tennis racquets. The aim of the RAP project has been to genetically improve ash, while at the same time ensuring the conservation of genetic diversity in future generations of trees. Propagation of clones by cuttings was investigated as a means of producing high quality plants on a large scale, benefiting nurseries, foresters, landowners, sawmills and furniture makers. The main task for RAP scientists was to scale up the in vitro production of carefully selected ash material. This was provided by research institutes and used to produce clones for testing in the field. Five selected lines of ash were used to establish shoot producing cultures. High concentrations of Thidiazuron (TDZ), a plant growth regulator, gave better rooting on media without cytokinins, plant hormones that promote cell division. However, by employing an elongation medium that did not contain cytokines, the best rooting was achieved through the use of both cytokinin and auxin, also a plant hormone. Plants grown from two of the selected clones grew successfully when placed in soil and transferred to research institutes for field tests. From an economic perspective it was better to use cuttings from ex vitro plants, therefore cuttings were field tested in a commercial nursery. Cuttings were about 10cm long and taken from the tip of the shoot or from the point where the leaf is attached to the stem. Cuttings from the tip were 80-90% successful in rooting, while those from the stem nodes were only 40-68% successful. The work by the RAP project has demonstrated that it was possible to rejuvenate adult clones and furthermore, subsequent propagation through the use of cuttings.
