Common Ash (Fraxinus excelsior), is a broad-leaved tree species which is present in almost all western Europe. In France it grows naturally in plain on rich soils with good available water content. In the mountains it is very frequent between 800 m and 1200 m elevation. It produces a highly valuable wood, which is used for furniture. For about 15 years it is more and more planted for afforestation of rich alluvial soils where it may be an alternative to poplar culture. It is also used for reforestation of abandoned farmland. In 2003, French forest nurseries have sold 700000 plants of Common Ash for plantations. In France, Ash is regulated only since 1997 and seed stands have been selected by CEMAGREF.
In fact, few is known about Ash genetic structure and about adaptability of the different seed sources to local conditions in France. Furthermore, in France, hybridisation between Common Ash and another species, Narrow leaved Ash (Fraxinus angustifolia), may occur. During the last 10 years, many disputes happened, due to the commercialisation of plants, which were not pure Common Ash (mixture of hybrids between the two species or, worst, narrow leaved Ash plants)
So, under the RAP project, an international provenance trial was established in spring 2005 with a "core collection" of 33 provenances common to all partners involved in that task. During nursery phase, flushing date has been recorded in 2003 and 2004. Data analysis shows very important differences between provenances, and as a first result, it is possible to rank precisely the different provenances in test for that important character.
Observations and measurements during nursery growth allow us to say with a quasi certainty, that the 33 different provenances in test are pure Common Ash. Indeed, during nursery growing phase, two narrow leaved Ash provenances were compared with Common Ash provenances as a control of specific purity. Three sites have been planted in the field in France: A complete one with 33 provenances in Normandy and two incomplete ones (22 and 25 provenances) in the central and southeastern part of France.
Data analysis of a 7 years old provenance-progeny test (two sites) provided with two important results:
- Variability between progenies within provenances is very important in comparison with variability between provenances for all the characters,
- Heritabilities of growth characters, straightness and flushing have been assessed.
Data of a 10 years old commercial provenance test have been analysed with two main results:
- Bad to very bad performances of the hybrid provenance,
- 5 registered provenances are now characterised for growth characters, stem straightness, flushing, number of forks and steep branches.