Studies on Ulmus: VII. Essex Elms

This biometrical study is based on a collection of nearly 500leaf samples from every ancient parish in the county. Most ofthe elms could be assigned to one of nineteen groups, 9 of U.carpinifolia, 1 of U. glabra, 2 of U. procera, 3 of putativeF₁ U. carpinifolia x U. glabra, 3 of U. carpinifolia with suspectedintrogression from U. glabra, and 1 of U. carpinifolia x U.procera. U. glabra is indigenous. Most of the U. carpinifolia appearto have spread out from six centres of origin, mostly near thecoast. These elms are very similar to forms now occurring innorth-west France, and it is thought probable that they wereintroduced from there, possibly by the settlers responsiblefor the Red Hills salt workings shortly before the Roman occupation.One group of U. carpinifolia came from Cambridgeshire via theEssex branch of the river Cam. Of the two main populations ofU. procera, that characteristic of south-east Essex is believedto have come from northern Kent, probably from the Hoo peninsula,while the group found in south-west Essex is probably a laterintroduction from further west. Hybridization between introduced U. carpinifolia and nativeU. glabra has occurred on a very large scale and putative F₁hybrids extend in a broad band across the county from the Hertfordshireborder to Suffolk. This hybridization most likely occurred duringthe clearing of the heavily forested part of northern Essexin pre-Conquest times. Subsequently, back crossing occurredbetween these hybrids and U. carpinifolia. Occasional hybridizationalso seems to have occurred between U. procera and the othertwo species. An outline of the probable history of the elm in eastern Englandas a whole concludes the paper.     

STUDIES ON ULMUS: III. The Village Elms of Hertfordshire

A biometrical study of the elms of southern Cambridgeshire waspublished in Forestry, xxxi. 132. The present paper is a parallelstudy of the village elms of Hertfordshire. The number of samplescollected was 143. For each of these, 8 quantitative and 1 qualitativefoliar character were determined. The majority of the samplesfall into 9 biometrically defined groups, 7 pertaining to U.carpinifolia and 2 to U. procera. U. glabra was also encounteredand one putative hybrid between U. glabra and U. carpinifolia. The U. carpinifolia elms occur in the east of the county andappear to be of Roman introduction in at least one case. Ofthe two groups of U. procera, one with short petioles and lowbasal asymmetry is centred around St. Albans. The other group,with longer petioles and conspicuous basal asymmetry, appearsto have entered the county both from the Icknield zone in thenorth and from Middlesex in the south. Both groups of U. procerawere established by the end of the Middle Ages, but their introductioninto the county has not yet been closely dated.     

The elms of Wales

Two methods of biometrical analysis were used to characterizea collection of 178 leaf samples assembled in the course ofan all-Wales survey of elms made in 1977–78. All sampleswere referable to either U. glabra, U. minor var. minor, U.minor var. vulgaris (= U. procera)orU. x hollandica. The variationwithin each taxon is described. Elm regions are demarcated tosupplement those already described for England. U. glabra isthe only elm believed to-be native. It is thought most likelythat the main Welsh population of U. minor var. vulgaris, inGlamorgan, was introduced from Somerset some time before theNorman Conquest. U. minor var. minor is rare throughout Walesand could be of 18th century origin; its possible spread alongdrovers' routes is considered. Some notomorphs of U. x hollandicamust have been introduced as such. Others probably arose inWales from hybridization involving U. glabra, U. minor var.vulgaris and U.x hollandica var. hollandica.     

Die mogliche Verbreitung des »UImensterbens« durch Wurzel-verwachsungen bei Ulmus carpinifolia Gled.

Possible spread of »elm disease« in Ulmus carpinifolia Gled. through root grafts . In a stand of elms (Ulmus carpinifolia Gled.), nearly all the trees were joined in groups of various sizes by “connecting roots”.     

Effects of Ophiostoma ulmi and Ophiostoma novo-ulmi culture filtrates on elm cultures from genotypes with different susceptibility to Dutch elm disease

Cell cultures of callus tissue cultures obtained from four elm genotypes (Ulmus minor; Ulmus minor×Ulmus pumila; [Ulmus carpinifolia×Ulmus glabra] × [Ulmus wallichiana×Ulmus glabra]; and Ulmus pumila), either susceptible or resistant to Dutch elm disease (DED) were exposed to culture filtrates of Ophiostoma ulmi and Ophiostoma novo-ulmi. Elm cells were largely affected by crude culture filtrate incorporated into the media. However, the correlation between ‘in vivo’ cell resistance and growth in the presence of culture filtrate was poor: the effects of fungal media components were greater than that exerted by fungal exotoxins. Therefore, it is concluded that these ‘in vitro’ assays cannot be used to evaluate resistance sources to DED in elms, or to assess specific pathogenicity of fungal isolates.     

Dutch elm disease pathogen transmission by the banded elm bark beetle Scolytus schevyrewi

Dutch Elm Disease (DED) is a vascular wilt disease of Ulmus species (elms) incited in North America primarily by the exotic fungus Ophiostoma novo‐ulmi. The pathogen is transmitted via root grafts and elm bark beetle vectors, including the native North American elm bark beetle, Hylurgopinus rufipes and the exotic smaller European elm bark beetle, Scolytus multistriatus. The banded elm bark beetle, Scolytus schevyrewi, is an exotic Asian bark beetle that is now apparently the dominant elm bark beetle in the Rocky Mountain region of the USA. It is not known if S. schevyrewi will have an equivalent vector competence or if management recommendations need to be updated. Thus the study objectives were to: (i) determine the type and size of wounds made by adult S. schevyrewi on branches of Ulmus americana and (ii) determine if adult S. schevyrewi can transfer the pathogen to American elms during maturation feeding. To determine the DED vectoring capability of S. schevyrewi, newly emerged adults were infested with spores of Ophiostoma novo‐ulmi and then placed with either in‐vivo or in‐vitro branches of American elm trees. The inoculation of trees via feeding wounds was successful 30% of the time for in‐vivo trials and 33% for in‐vitro trials. Although the infection rate of DED has declined in Colorado over the past 10 years, the disease is still present in urban elms. While it appears that S. schevyrewi is another vector of the DED pathogens, it appears that S. schevyrewi is no more efficient than S. multistriatus. Thus, management programs that remove elm bark beetle breeding sites, rapidly remove DED‐infected elms and include the planting of DED‐resistant elms should continue to be effective management tactics.     

Some Consequences of the 1975-1976 Drought for Dutch Elm Disease in Southern England

During the exceptionally hot, dry summer of 1976 the large elmbark beetle, Scolytus scolytus, was able to invade and successfullybreed in apparently healthy, undiseased elms. A conspicuousfeature was the clustering of wasps, bees and ladybirds on thestems, attracted by sap exudation. The trees were probably sufferingfrom drought, although many showed no symptoms. The phenomenonoccurred mainly on shallow soils over limestone; trees on chalkwere not generally affected. In 1976, and to some extent in 1975, the downward developmentof Ceratocystis ulmi through the tree was less than in previousyears, and only a low proportion of the numerous maturationfeeding wounds became infected. However the drought does notappear to have significantly influenced the course of the epidemic. The attacks by S. scolytus on undiseased trees are discussedin respect of 19th Century reports of attacks on elms, and itis concluded that the ability of S. scolytus to assume a moreprimary role may have been underestimated.     

Testing Dosage Rates of Methoxychlor Applied by Helicopter for Control of Dutch Elm Disease

During April 1973 various doses and concentrations of methoxychlorwere applied to healthy elms by helicopter on farmland nearWarwick. Bioassays showed that only the highest rate, five gallonsof 6 per cent methoxychlor per tree achieved good control ofmaturation feeding by Scolytus scolytus (Fab.) for six weeksafter spraying. The bioassays indicated that the efficacy ofthis treatment declined markedly between six and ten weeks afterspraying. None of the treatments prevented beetle-borne infectionofthe treated test elms, though trees sprayed with five gallonsof 6 per cent methoxychlor showed the least amount of Dutchelm disease at the end of the summer Separate tests of aerial spray deposits using a standard quantityof methoxychlor at varying dilutions in water showed that treecoverage was generally good, though none of these treatmentssatisfactorily controlled elm beetle maturation feeding. Residueanalyses of methoxychlor deposits indicate that the originalresidues declined by about 50 per cent thirteen weeks afterspraying     

五种榆树在榆阳区的生长适应性研究

为了丰富榆阳区榆树种类,给当地植树造林、改善生态环境以及城乡绿化提供更多优良榆树种类,从新疆和河南引进了裂叶榆、圆冠榆、大叶垂榆和金叶榆,与榆阳区乡土树种白榆对照进行生长适应研究,结果表明:4种引进榆树均可以成活生长,除白榆之外,裂叶榆和金叶榆能够完成生长、开花、结果及果实成熟等整个生命周期。生长量由大到小依次为裂叶榆、圆冠榆、大叶垂榆和金叶榆。新引进的4种榆树分别作为风沙治理、改善生态环境以及市内观赏景观树种可在榆阳区引种推广应用。     

浑善达克沙地桑根达来古榆树调查研究

榆树疏林草原是浑善达克沙地上的一种原始自然景观,被认为是最稳定的植被类型.我们把胸径＞50 cm的榆树定义为古榆树.2009年5～8月在浑善达克沙地正蓝旗桑根达来镇境内用样方法对宝绍代苏木安夏日嘎查、额木格德苏木白音胡舒嘎查等8个区域胸径＞ 50 cm的古榆树进行实地调查,结果表明:(1)该区共有古榆树308株,分布最...     

Xylem vessel diameter as a factor in resistance of Ulmus minor to Ophiostoma novo‐ulmi

An investigation has been carried out to study the relationship between the susceptibility of Ulmus minor to Ophiostoma novo‐ulmi and the diameter of its xylem vessels. Vessel diameters have been analysed in seven Spanish elms of known susceptibility, taking measurements from second and third year rings in 3‐year‐old branches. In the second year rings no relationship could be observed between the vessel diameters and the susceptibility of the trees. In the third year rings the mean diameter and the percentage of vessels larger than 100 μm were found to be significantly greater for the group of elms of high susceptibility. In the third year rings the vessel transectional area (VTA) and the theoretical hydraulic conductance (THC) were calculated. The decrease in VTA and THC became increasingly noticeable in the group of high susceptibility elms as vessels of larger diameter were excluded from the calculation. Xylem vessel diameters and the proportion of large vessels were correlated with the susceptibility of U. minor to Dutch elm disease. How these properties influence the dispersal of the fungus, the sap flow and the tree's ability to compartmentalize the disease is discussed.     

Oviposition preference and larval performance of Aeolesthes sarta (Coleoptera: Cerambycidae) in six hardwood tree species

Sarta longhorned beetle (SLB), Aeolesthes sarta Solsky, is an economically important pest of fruit and shade trees in central and east Asia. Choice, no-choice, and larval insertion experiments were conducted to determine SLB oviposition preference and larval host suitability on six hardwood tree species including Ulmus carpinifolia Borkh., Ulmus carpinifolia var. umbraculifera Rehd., Platanus orientalis L., Populus alba L., Salix alba L., and Fraxinus rotundifolia Miller subsp. persica (Boiss.), under laboratory conditions. In the choice and no-choice experiments, significantly greater numbers of eggs and living larvae, and greater mass of living larvae were found on U. carpinifolia and U. carpinifolia var. umbraculifera compared to those on the other tree species. In the choice experiment, oviposition did not occur on F. rotundifolia subsp. persica. There were a few eggs on P. alba but no living larvae. The mean mass of living larvae was lowest on P. orientalis. In addition, in the no-choice experiment significantly fewer numbers and mass of living larvae were found in P. alba and F. rotundifolia subsp. persica. In the larval insertion experiment, more larvae survived on U. carpinifolia and U. carpinifolia var. umbraculifera compared to the other trees. Larvae recovered from U. carpinifolia and U. carpinifolia var. umbraculifera weighed significantly more than larvae from the other trees. These results suggest that U. carpinifolia and U. carpinifolia var. umbraculifera are the most preferred and suitable hosts for SLB adults and larvae. Salix alba is an acceptable host for adult oviposition and a potentially suitable host for larval development. Platanus orientalis and P. alba are less suitable, and F. rotundifolia subsp. persica appeared to be unsuitable as a host for SLB.     

Field observations on the biocontrol of Dutch elm disease with Trichoderma virie pellets

Fifteen elm trees ranging in DBH from 25 to 40 cm were inoculated with ca. 8 mm diameter pellets containing propagules of Trichoderma viride IMI 206039 and IMI 2006040 besides nutrients. These pellets were inserted in the trunks every 10 cm around the circumference. Dead elms present upwind and downwind from the 15 treated elms remained standing during the four year duration of the experiment. No progress in the disease occurred during three growing seasons after the original treatment. During the fourth growing season (1982) 4 elms died and 11 survived, though one was severely damaged. These 11 surviving trees were retreated in September 1982.     

Variation among Italian and French elm clones in their response to Ophiostoma novo‐ulmi inoculation

In 1995 a clone bank of elms from across Italy was created at Antella (Florence, I) under a European Union project. In 1998 an experimental planting of some clones from this source was established in Antella together with material from a similar clone bank in France and two reference clones: Commelin (relatively susceptible) and Lobel (relatively resistant). In May 2001, the elms were inoculated with Ophiostoma novo‐ulmi and disease development was assessed throughout that summer and the next. Significant differences in susceptibility were found between taxonomic groups, with putative natural hybrids between Ulmus minor and Ulmus pumila being the most resistant and Ulmus glabra the most susceptible. Significant differences were also found within U. minor, some clones being as resistant as Lobel. For U. minor, a statistically significant relation was found with latitude, southerly clones showing less disease than more northerly ones. Relationships were also found between disease severity and times to bud burst, these relationships applying both to the different taxonomic groups and within U. minor. Relationships between growth increment and disease severity were inconsistent. These results are discussed in relation to the intrinsic genetically‐controlled differences that exist between elms and to differences in susceptibility that occur as the growing season proceeds and as a consequence of environmental influences.     

Dutch elm disease on the island of Gotland: monitoring disease vector and combat measures

The island of Gotland (Sweden) possesses the largest (more than one million trees) wild population of elms in northern Europe, which until recently was not affected by Dutch elm disease (DED). In 2005, DED was observed for the first time in the northeastern part of Gotland, and in the following years, it rapidly spread in all directions, generally following the major distribution of elms. Implementation of intensive control measures including ground surveys and geographic information system mapping of DED-diseased trees, their felling and destruction, and stump treatment with the herbicide glyphosate allowed reduction of the source of infection and probably suppression of an otherwise very rapid spread of the disease. Monitoring the flying periods of Scolytus multistriatus vector beetles between the years 2007 and 2011 showed that the abundance of trapped beetles in most cases differed significantly among individual years. Over the entire monitoring period, 55.2% of the beetles were trapped in June, 31.2% in July and 13.5% in August (difference among individual months significant at p?S. multistriatus, suggesting that the removal of trees attacked in the previous vegetation period as a combat measure should be completed before the beginning of the flying season of S. multistriatus, and that the application of the integrated DED management has the potential to arrest the development of the disease in a geographically isolated area such as Gotland.     

‘Morfeo’ Elm: a new variety resistant to Dutch elm disease

Dutch elm disease (DED) has spread through Europe and North America since the beginning of the twentieth century. In response, several independent genetic improvement programmes for breeding DED‐resistant elms have been established on both sides of the Atlantic. Assimilating a wide range of resistant clones of different parentage should help ensure survival of the elm in the event of mutation of the pathogen. The Italian elm breeding programme began in the late 1970s and has recently raised a new variety by crossing a specimen of U. chenmoui with the Dutch hybrid clone ‘405’. This new release, named ‘Morfeo’, is extremely resistant to DED and has an attractive form and foliage. It is also fast‐growing, tolerant of drought and soils waterlogged in winter, therefore proving well adapted to the climates of both north‐western Europe and the Mediterranean. Following trials in England, ‘Morfeo’ is considered of potential importance in the conservation of several invertebrates endangered by the consequences of DED.     

Woodland Elms in Wessex

A study undertaken by the Wessex Silvicultural Group on thegrowth of elm in woodland disclosed the occurrence of potentiallyvaluable elm stands in many parts of south-west England. Thepaper discusses some aspects of cultivating elm in woodland,and provisional estimates of volume production are made. Muchof the information relates to English elm (Ulmus procera Salisbury),but other species and hybrids are briefly reviewed. Commentson some current elm problems are included.     

Regeneration of phenotypically normal English elm (Ulmus procera) plantlets following transformation with an Agrobacterium tumefaciens binary vector

A transformation system was developed for English elm (Ulmus procera Salisbury) using Agrobacterium tumefaciens C58 pMP90 p35SGUS/INTRON, allowing for the transfer of foreign genes and regeneration of phenotypically normal elm plantlets. The PCR analysis indicated that both nptII and uidA genes were stably inserted in the plant genome. beta-Glucuronidase histochemical and fluorimetric assays revealed expression of the uidA gene in the shoots, leaves, stems and roots of regenerated transgenic plants. The DNA-DNA hybridizations confirmed the presence of the uidA gene in regenerant plants. Factors influencing successful transformation and regeneration of elms included: identifying gene-transfer-proficient Agrobacterium strains for use with elms; developing an infection protocol allowing T-DNA transfer while retaining the ability to remove inciting bacteria; and identifying selection conditions to eliminate non-transformed material and choice of regeneration medium to allow shoot production. The potential utility of an effective elm transformation and regeneration system in the control of Dutch elm disease is discussed.     

Diversity and pathogenicity of Botryosphaeriaceae on declining Ostrya carpinifolia in Slovenia and Italy following extreme weather conditions

Unusual and extensive dieback of European hop hornbeam (Ostrya carpinifolia) has been observed in western Slovenia and northern Italy in recent years, when extreme drought and higher temperatures were recorded. A preliminary study identified Botryosphaeria dothidea as a potential causative agent of the dieback. Further characterization of intra- and interspecies diversity of Botryosphaeriaceae collected from O. carpinifolia and other tree species in the affected area was achieved based on anamorph morphology, sequence data from the ITS rDNA and EF1-??, PCR?CRFLP analysis and AFLP profiles. The majority of the isolates analyzed were identified as B. dothidea, and in vitro pathogenicity tests re-confirmed the fungus to be an important cause of the disease. Insight into the B. dothidea population, diversity based on AFLP markers indicates that the dieback observed in O. carpinifolia is probably associated with a heterogenous population of B. dothidea, which emerged from a latent state in response to changed climate conditions. Isolates with Dothiorella-like conidia were also identified during the survey, but these were collected more rarely and appear to represent undescribed species. Isolates from Dothiorella genus expressed low pathogenicity in pathogenicity tests and proved no impact on the pathogenic ability of B. dothidea.     

Metabolic fingerprinting allows discrimination between Ulmus pumila and U. minor,and between U. minor clones of different susceptibility to Dutch elm disease

Experiments were conducted to test whether Fourier transform‐infrared (FT‐IR) spectroscopy, coupled with chemometric methods, can distinguish healthy xylem tissues collected from elms known to differ significantly in their susceptibility to Ophiostoma novo‐ulmi Brasier. Twig samples from resistant Ulmus pumila L., susceptible U. minor Mill. and resistant U. minor clones were harvested on 1 May, 15 May, 1 June, 1 July and 1 September 2004, and subjected to FT‐IR analysis. The application of principal component analysis to the spectral data, followed by discriminant function analysis, discriminated between the three groups of samples in all harvesting dates. The examination of the DF‐loading plots allowed the identification of key regions within the spectra for the separation between clusters. The chemical assignments of these key regions allowed the following interpretations to be made: (i) U. pumila tissues contained enhanced levels of starch, cellulose and lignin with respect to U. minor tissues and (ii) resistant U. minor tissues contained enhanced levels of starch, cellulose and pectic polysaccharides with respect to susceptible U. minor tissues. The possible roles of the compositional differences in disease resistance, as well as the potential use of FT‐IR spectroscopy and chemometrics as a tool for screening resistant elms are discussed.