Elms are deciduous and semi-deciduous trees comprising the genus Ulmus in the family Ulmaceae. They are distributed over most of the Northern Hemisphere, inhabiting the temperate and tropical-montane regions of North America and Eurasia, presently ranging southward in the Middle East to Lebanon and Israel, and across the Equator in the Far East into Indonesia.
Dutch elm disease (DED) is caused by a member of the sac fungi (Ascomycota) affecting elm trees, and is spread by elm bark beetles. Believed to be originally native to Asia, the disease was accidentally introduced into America, Europe, and New Zealand. In these regions it has devastated native populations of elms that did not have resistance to the disease. The name "Dutch elm disease" refers to its identification in 1921 and later in the Netherlands by Dutch phytopathologists Bea Schwarz and Christine Buisman, who both worked with professor Johanna Westerdijk. The disease affects species in the genera Ulmus and Zelkova, therefore it is not specific to the Dutch elm hybrid.
Ulmus glabraHudson, the wych elm or Scots elm, has the widest range of the European elm species, from Ireland eastwards to the Ural Mountains, and from the Arctic Circle south to the mountains of the Peloponnese and Sicily, where the species reaches its southern limit in Europe; it is also found in Iran. A large deciduous tree, it is essentially a montane species, growing at elevations up to 1,500 m (4,900 ft), preferring sites with moist soils and high humidity. The tree can form pure forests in Scandinavia and occurs as far north as latitude 67°N at Beiarn in Norway. It has been successfully introduced as far north as Tromsø and Alta in northern Norway (70°N). It has also been successfully introduced to Narsarsuaq, near the southern tip of Greenland (61°N).
Ulmus minor subsp. minor, the narrow-leaved elm, was the name used by R. H. Richens (1983) for English field elms that were not English elm, Cornish elm, Lock elm or Guernsey elm. Many publications, however, continue to use plain Ulmus minor for Richens's subspecies, a name Richens reserved for the undifferentiated continental field elms. Dr Max Coleman of Royal Botanic Garden Edinburgh argued in his 2002 paper 'British Elms' that there was no clear distinction between species and subspecies.
Ulmus wallichianaPlanch., the Himalayan elm, also known as the Kashmir elm and Bhutan elm, is a mountain tree ranging from central Nuristan in Afghanistan, through northern Pakistan and northern India to western Nepal at elevations of 800–3000 m. Although dissimilar in appearance, its common name is occasionally used in error for the cherry bark elm Ulmus villosa, which is also endemic to the Kashmir, but inhabits the valleys, not the mountain slopes. The species is closely related to the wych elm U. glabra.
Ulmus 'Nanguen' is a complex fourth generation Dutch hybrid cultivar raised at the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen. Lutèce was derived from the cross 'Plantyn' ×, an ancestry comprising four field elms, a wych elm, the curious Exeter Elm ('Exoniensis'), and a frost-resistant selection of the Himalayan elm.
Ulmus × hollandica 'Commelin' is a Dutch hybrid cultivar released for sale in 1960. The tree was raised at Baarn as clone 274 by the Foundation Willie Commelin Scholten Phytopathological Laboratory in 1940, from a crossing of Ulmus × hollandica 'Vegeta' and clone 1, an Ulmus minor selected from a 1929 elm seedlings lot obtained from the Barbier nursery, Orléans.
The Dutch hybrid cultivar Ulmus 'Dodoens' was derived from a selfed seedling of a crossing of the Exeter Elm Ulmus 'Exoniensis' with the Himalayan Elm Ulmus wallichiana at the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen. The tree was one of several cultivars prepared for release in 1970, but delayed by the outbreak of the second, far more aggressive strain of Dutch elm disease.
Ulmus 'Lobel' is a Dutch hybrid cultivar raised at the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen, from a crossing of clone '202' with '336'. 'Lobel' was cloned in 1962 and released for sale in 1973.
Ulmus 'Columella' is a Dutch elm cultivar raised by the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen. Originally thought to have been derived from a selfed or openly pollinated seedling of the hybrid clone 'Plantyn', DNA analysis later determined it arose from a cross of 'Plantyn' and Ulmus minor. Sown in 1967, it was released for sale in 1989 after proving extremely resistant to Dutch elm disease following injection with unnaturally high doses of the pathogen, Ophiostoma novo-ulmi. However, propagated by grafting onto wych elm rootstocks, graft failure owing to incompatibility has become a common occurrence in the Netherlands.
The Field Elm cultivar Ulmus minor 'Christine Buisman' was the first cultivar released by the Dutch elm breeding programme, initiated in response to the less virulent form of Dutch elm disease (DED), Ophiostoma ulmi, which afflicted Europe's elms after the First World War. 'Christine Buisman' was selected from a batch of 390 seedlings grown from seed collected in the Parque de la Quinta de la Fuente del Berro, Madrid, by Mrs Van Eeghen, a friend of elm researcher Johanna Westerdijk, in 1929 and named for the elm disease researcher Christine Buisman. Originally identified as Ulmus foliacea, it was later treated as Ulmus × hollandica by Melville. However, more recent research in Belgium using DNA markers has reaffirmed 'Christine Buisman' as a clone of U. minor.
The elm cultivar Ulmus minor 'Bea Schwarz' was cloned at Wageningen in the Netherlands, by the elm disease committee, from a selection of Ulmus minor found in France in 1939. However, specimens of the tree grown in the UK and the United States are falsely treated as Ulmus × hollandica.
Ophiostoma ulmi is a species of fungus in the family Ophiostomataceae. It is one of the causative agents of Dutch elm disease. It was first described under the name Graphium ulmi, and later transferred to the genus Ophiostoma.
Ophiostoma novo-ulmi is a species of fungus in the family Ophiostomataceae. It is one of the key causative agents associated with Dutch Elm Disease (DED), along with Ophiostoma ulmi and Ophiostoma himal-ulmi.
The elm Ulmus wallichiana subsp. xanthoderma was identified by Melville and Heybroek after the latter's expedition to the Himalaya in 1960. The tree is of more western distribution than subsp. wallichiana, ranging from Afghanistan to Kashmir.
Ulmus wallichiana subsp. wallichiana was identified by Melville and Heybroek after the latter's expedition to the Himalaya in 1960.
Ulmus wallichiana var. tomentosa was identified by Melville & Heybroek after the latter's expedition to the Himalaya in 1960.
In molecular biology, the cerato-platanin family of proteins includes the phytotoxin cerato-platanin (CP) produced by the Ascomycete Ceratocystis platani. CP homologs are also found in both the Ascomycota and the Basidiomycota branches of Dikarya. This toxin causes the severe plant disease: canker stain. This protein occurs in the cell wall of the fungus and is involved in the host-pathogen interaction and induces both cell necrosis and phytoalexin synthesis which is one of the first plant defense-related events. CP, like other fungal surface proteins, is able to self-assemble in vitro. CP is a 120 amino acid protein, containing 40% hydrophobic residues. It is one of the rare examples of protein in which contains a Hopf link. The link is formed by covalent loops - the pieces of protein backbone closed by two disulphide bonds. The N-terminal region of CP is very similar to cerato-ulmin, a phytotoxic protein produced by the Ophiostoma species belonging to the hydrophobin family, which also self-assembles.
The cultivar Ulmus 'Fuente Umbria' was raised from seed collected in 1995 from an elm resembling Ulmus minor growing in a field at Fuente Umbria west of Valencia, by researchers at the Escuela Técnica Superior de Ingenieros de Montes, Universidad Politėcnica de Madrid. 'Fuente Umbria' is one of seven cultivars found to have a very high resistance to Dutch Elm Disease, on a par with, if not greater than, the hybrid cultivar 'Sapporo Autumn Gold'. However, retrospective DNA analysis has revealed that the clone has Ulmus pumila DNA, the species introduced to Spain at the end of the 16th century, and has consequently been dropped from the programme.
The elm cultivar Ulmus 'Toledo' was raised from seed collected in 1999 from a tree believed to be Ulmus minor growing in the eponymous city, by researchers at the Escuela Técnica Superior de Ingenieros de Montes, Universidad Politėcnica de Madrid. However, retrospective DNA analysis revealed that the clone also had Ulmus pumila DNA, the species introduced to Spain at the end of the 16th century, and has consequently been dropped from the research programme.
