Please Click Here to download a PDF version of the Spanish Clones presentation:
The link above is to a presentation made by Juan Martin of the Spanish elm breeding programme at the 3rd Elm Conference held in Florence in October 2013. Many in attendance were startled by what it announced.
The Spanish programme, initiated in 1986, began by investigating elms native to the Iberian peninsula in order to hybridise the best of the survivors with the usual Asian species known for their resistance. At a certain point, the researchers became aware that they were encountering sufficient disease resistance in certain native Spanish trees to be able to dispense with the process of European x Asian hybridisation. A very few Spanish strains of U. minor (field elm) outperformed the benchmark resistant Sapporo Autumn Gold in inoculation trials.
U. minor is the species which includes the narrow-leaved elms of eastern England, and English elm itself. However, all surviving Spanish trees shown to be the “English elm” clone of U. minor were screened out of the study. This is the same programme which showed English elm to be a single clone, and its extreme lack of disease resistance suggested that the few surviving exampls in Spain were enjoying pure luck rather than useful genes. In fact, on the basis of earlier French studies, it had been thought unlikely that any native European elm could show anything more than moderate disease resistance. The Spanish research now strongly indicates otherwise, at least in the case of field elms from the Iberian peninsula.
A detail: Sapporo Autumn Gold is often used as a resistant control clone in inoculation trials, typically scoring very low percentages for wilting and dieback. The presentation by the Spanish team shows that its symptoms on inoculation can be much higher than previously believed. This is almost certainly because the Spanish inoculation is applied to the base of the trunk rather than the top third of the plant. It is open to debate whether this method may be so aggressive as to be far removed from the levels of disease challenge to be expected in the field. At all events, there is no crisis of confidence in Sapporo’s resistance, but the ability of any U. minor clones to withstand this variety of testing is quite remarkable.
ResistantElms.co.uk broadly agrees with the scores for aesthetic quality given by the Spanish researchers to these trees.
Availability: nil at present, since the commercial release of the clones is mired in red tape and politics, but everything possible is being done to find a way forward.