Breeding against Dutch elm disease adapted to the Mediterranean climate.

Breeding for resistance was considered one of the possible ways to limit the damages caused by the epidemics of Dutch elm disease (DED) during the last century. The elm breeding program developed by CNR in Italy was based on the idea that the Mediterranean environment would need its own specific selections. A base broadening of the genetic resources was operated. A base of native elms with a set of good characters to act as parents was bred with different Asian elm species that showed the ability of acclimatization to the different climates in which elms have to be planted. For this aim a large collection of elm species was constituted, followed by hybridisation studies. Progenies were tested for DED resistance. The more resistant clones were planted in trial fields characterised by contrasting Mediterranean climates in order to select the best potential genotypes adapted either to coastal or to mountain environmental conditions. More than 60 clones resistant, fast-growing and showing remarkable aesthetic ornamental characters were obtained.