 Dutch hybridizations invariably included the Himalayan elm "(Ulmus wallichiana)" as a source of anti-fungal genes and have proven more tolerant of wet ground; they should also ultimately reach a greater size.However, the susceptibility of the cultivar 'Lobel', used as a control in Italian trials, to elm yellows has now (2014) raised a question mark over all the Dutch clones.A number of highly resistant "Ulmus" cultivars has been released since 2000 by the Institute of Plant Protection in Florence, most commonly featuring crosses of the Dutch cultivar 'Plantijn' with the Siberian Elm to produce resistant trees better adapted to the Mediterranean climate.