Elm Cultivars Research Articles

Comparative Transcriptome Analysis Reveals Candidate Genes and Pathways for Potential Branch Growth in Elm (Ulmus pumila) Cultivars.

Simple SummaryElm (Ulmus pumila) is a strong essential wood, and it is widely used in cabinets, sculptures, and ship making. In the present study, phenotypic and comparative transcriptomic analyses were performed in elm fast- (UGu17 and UZuantian) and slow-growing cultivars (U81-07 and U82-39). Phenotypic observation showed that the thickness of secondary xylem of 2-year-old fast-growing branches was greater compared with slow-growing cultivars. Comparative transcriptome analysis predicted that many pathways were involved in vascular development and transcriptional regulation in elm, such as “plant-type secondary cell wall biogenesis”, “cell wall thickening”, and “phenylpropanoid biosynthesis”. NAC domain transcriptional factors (TFs) and their master regulators, cellulose synthase catalytic subunits (CESAs), xylan synthesis, and secondary wall thickness were presumed to function in the thickening mechanism of elm branches. Our results indicated that the general phenylpropanoid pathway and lignin metabolism had vital functions in the growth of elm branches.Wood plays a vital role in human life. It is important to study the thickening mechanism of tree branches and explore the mechanism of wood formation. Elm (Ulmus pumila) is a strong essential wood, and it is widely used in cabinets, sculptures, and ship making. In the present study, phenotypic and comparative transcriptomic analyses were performed in U. pumila fast- (UGu17 and UZuantian) and slow-growing cultivars (U81-07 and U82-39). Phenotypic observation showed that the thickness of secondary xylem of 2-year-old fast-growing branches was greater compared with slow-growing cultivars. A total of 9367 (up = 4363, down = 5004), 7159 (3413/3746), 7436 (3566/3870), and 5707 (2719/2988) differentially expressed genes (DEGs) were identified between fast- and slow-growing cultivars. Moreover, GO and KEGG enrichment analyses predicted that many pathways were involved in vascular development and transcriptional regulation in elm, such as “plant-type secondary cell wall biogenesis”, “cell wall thickening”, and “phenylpropanoid biosynthesis”. NAC domain transcriptional factors (TFs) and their master regulators (VND1/MYB26), cellulose synthase catalytic subunits (CESAs) (such as IRX5/IRX3/IRX1), xylan synthesis, and secondary wall thickness (such as IRX9/IRX10/IRX8) were supposed to function in the thickening mechanism of elm branches. Our results indicated that the general phenylpropanoid pathway (such as PAL/C4H/4CL) and lignin metabolism (such as HCL/CSE/CCoAOMT/CCR/F5H) had vital functions in the growth of elm branches. Our transcriptome data were consistent with molecular results for branch thickening in elm cultivars.

The extensive damage to elms by Dutch elm disease agents and their hybrids in northwestern Russia

Elms are important amenity trees in the European part of Russia, incl. the St. Petersburg and Leningrad Region. The native species Ulmus glabra and U. laevis mainly grow there, on the northern border of their natural range. Hybrid elm cultivars have been planted since the early 2000s. Thousands of elms suffer from Dutch elm disease in the Leningrad Region. We found that in the north-western part of Russia Ophiostoma novo-ulmi subsp. novo-ulmi and O. novo-ulmi subsp. americana as well as hybrids of these subspecies are aggressive agents of DED on elms. According to in vitro experiments of hybrids in pure cultures, O. novo-ulmi subsp. americana x novo-ulmi had the highest growth rate, and O. novo-ulmi subsp. novo-ulmi the lowest growth rate.Ulmus glabra (>40 years old) was affected the most, with ca. 20 % of assessed trees found to already be dead and only 56 % found to be in good condition. The documented health among young elm cultivars (<25 years old) revealed that only 4% were dead, and 91 % were healthy or only experiencing some branch loss. Ulmus laevis (with 74 % of individuals healthy or with some branch loss, and 5% dead) was significantly healthier compared to U. glabra. In the city, the health of all assessed elm species was significantly better in greenspaces than next to highways.As the potential vectors of DED, Scolytus scolytus, S. multistriatus and S. pygmaeus are registered in the assessed region.

Ten-year performance of elms in the National Elm Trial

Ulmus americana (American elm) was an important urban tree in North America prior to the introduction of the Dutch elm disease (Ophiostoma ulmi and O. novo-ulmi) pathogen in 1930. Subsequently, urban and community forests were devastated by the loss of the large canopies. Disease tolerant elms (Ulmus spp.) of various species were later developed; however, consumer acceptance of these trees was slow. The goal of the National Elm Trial was to evaluate newer cultivars of elm across the United States. Trees were monitored for survival and growth for 7 to 10 years at 16 different locations. 'Morton' elm had >90% survival, while 13 cultivars averaged 70 to 90%, and five cultivars ranged from 25 to 69% survival. Trunk diameter growth by location ranged from 0.5 cm year-1 at Colorado to more than 2.0 cm year-1 at Iowa. By taxa, trunk diameter growth ranged from a low of 'JFS Bieberich' elm (0.7 cm year-1) to a high of 'New Horizon' elm (1.7 cm year-1). The fastest height growth was found with the American elm cultivars 'New Harmony' and 'Princeton' (0.63 and 0.61 m year-1, respectively).

American elm cultivars: Variation in compartmentalization of infection by Ophiostoma novo‐ulmi and its effects on hydraulic conductivity

SummaryFive cultivars and two populations of wild‐type seedlings of American elm (Ulmus americana), 3 and 4 years old, were examined for differences in their abilities to compartmentalize and resist infection by artificially inoculating with Ophiostoma novo‐ulmi. Morphological characteristics of tree defence, often referred to as the compartmentalization of decay in trees model, were used as a conceptual framework, with particular emphasis on the limiting of tangential spread of infection within the xylem and barriers that limit spread outwards to cells formed after infection. To investigate the change in functional xylem over time, 3‐year‐old trees were assessed at multiple time points following inoculation for hydraulic conductivity. Three and four‐year‐old cut trees were placed in 0.1% w/v safranin O for 18 to 24 hr to indicate functional xylem. Transverse sections of the stained stems were used to calculate per cent of sap‐conducting xylem area and the per cent of circumference conducting of first formed cells and later formed cells. At each collection time, trees were assessed for disease severity on a 1–12 scale, based on the percentage of permanent wilt in the crown. There was considerable variation between cultivars in disease severity and their capacity to localize and resist infection. “Prairie Expedition,” which had the lowest disease severity rating in 2015 and the second lowest in 2016, consistently limited the spread of infection into newly formed xylem and had functional xylem around the entire circumference of the stem at 90 days post‐inoculation. “Valley Forge” in 2016 had the lowest overall disease severity rating and was the only cultivar to consistently limit the tangential spread of infection within extant xylem. This research identifies key characteristics that some cultivars have to resist and limit infection and provides new information that can be used in disease screening programmes to evaluate other cultivars and older plant material.

Ten-Year Performance of the United States National Elm Trial

Ulmus americana (American elm) was an important urban tree in North America prior to the introduction of the Dutch elm disease pathogen in 1930. Subsequently, urban and community forests were devastated by the loss of large canopies. Tree improvement programs produced disease tolerant American and Eurasian elm cultivars and introduced them into the nursery industry. However, consumer acceptance was slow. The National Elm Trial was established to evaluate commercially available taxa of elm across the United States. Established at 16 locations, these plantings monitored survival and growth, as well as disease and insect pressure for 7 to 10 years. ‘Morton’ elm had &gt;90% survival, while 13 cultivars averaged 70% to 90%, and five cultivars ranged from 25% to 69% survival. Trunk diameter growth by location ranged from 0.5 cm/year (Colorado, U.S.) to more than 2.0 cm/year (Iowa, U.S.). By taxa, trunk diameter growth ranged from a low, by ‘JFS Bieberich’ elm (0.7 cm/year), to a high by ‘New Horizon’ elm (1.7 cm/year). Scale insects were minor issues at most trial locations, except Colorado, where scales contributed to the death of several cultivars. Performance ratings (scale 1 to 5) ranged from 2.7 for ‘JFS Bieberich’ elm to 4.5 for ‘New Horizon’ elm. Based on the ratings, the preferred cultivars of American elm were ‘New Harmony’ and ‘Princeton’, and the preferred cultivars of Asian elm were The Morton Arboretum introductions and ‘New Horizon’. These findings will help green-industry professionals determine what elm cultivars will perform the best in different regions.

Comparison of commercial elm cultivars and promising unreleased Dutch clones for resistance to Ophiostoma novo-ulmi

Elms, and especially Ulmus × hollandica have been dominant and very much appreciated trees in cities and rural landscape for centuries in the Netherlands. As a result of two Dutch Elm Disease (DED) epidemics in the 20th century these trees largely disappeared from the landscape. Despite the introduction of new cultivars with increased levels of DED-resistance, by the end of the 20th century the elm had disappeared from the top 20 list of trees produced by Dutch nurseries. New cultivars with increased resistance to DED are used to a limited extent only. Apparently the lasting problems with DED in old cultivars has led to a lack of confidence in the resistance of these latest released cultivars among urban foresters and landscape managers. This paper reports on a study that aims at restoring the position of the elm as a street tree in the Netherlands by providing information on resistance to O. novo-ulmi causing DED of the currently available cultivars. All elm cultivars currently on the Dutch market were compared in an inoculation test. In 2007 a field experiment of 18 cultivars, one species and 10 non-released clones from the Dutch elm breeding program was established. Two cultivars were used as reference clones: “Commelin” (relatively susceptible) and “Lobel” (relatively resistant). In 2008 and 2009 the elms were stem-inoculated with Ophiostoma novo-ulmi and disease development was assessed throughout the summer and the following year. Clear differences in resistance to O. novo-ulmi were found between the cultivars, with “Columella”, “Sapporo Autumn Gold”’ and “Rebella” being highly resistant and significantly different from “Lobel” and “Regal”, “Urban”, “Belgica”, “Den Haag” and the U. laevis seedlings being the most susceptible and comparable to “Commelin”. The non-released clones performed comparable to “Lobel’”or even better. The ranking of the cultivars based on their level of resistance to O. novo-ulmi in this field test corresponds well with experience in urban green practice. Our conclusion is that there is a wide range of cultivars available with a good to excellent level of resistance. The available cultivars have a broad genetic base due to different parentage and use of exotic germplasm in the crossings. This broad genetic background may contribute to the stability of resistance in case new forms of the disease appear. The non-released clones performed well compared to the released cultivars and give good opportunities to further broaden the current range of cultivars on the Dutch and European market.

Stegophora ulmea

<i>Stegophora ulmea</i>

Variation in Leafhopper Species Abundance and Diversity among Elm Seedlings and Cultivars

A survey was conducted in the 2001 growing season to determine the leafhopper species composition, abundance, richness, diversity, and evenness among trees of three elm (Ulmus sp.) cultivars, two U.S. National Arboretum (USNA) seedling selections of U. szechuanica Fang, and two USNA seedling selections of U. bergmanniana Schneid. in a mixed stand. Yellow sticky traps were used to qualify and quantify the number of aerial leafhoppers from 1 May 2001 until 4 September 2001. A total of 4,523 individuals, belonging to 39 species within seven leafhopper subfamilies, were trapped. The weekly mean number of leafhoppers collected was significantly higher on traps from `Patriot', followed by `Frontier' and `Prospector', than on traps from the USNA seedling selections. Although the weekly mean species richness for `Prospector' was lower than the other two cultivars, the three cultivars had higher mean species richness than the USNA seedling selections of U. szechuanica and U. bergmanniana. Diversity among cultivars was higher than among the USNA seedling selections. Ulmus bergmanniana 68983 and U. szechuanica 68986 shared the highest percentage of species similarity, while `Frontier' and U. szechuanica 68991 were the most dissimilar. Of the species collected, Agallia quadripunctata, Empoasca fabae and Graphocephala versuta were the most abundant. The other species were mostly rare based on their low abundance. Scaphoideus luteolus, the only confirmed vector of elm yellows in North America, was found among the elm cultivars only. Yet, the Cicadellinae leafhoppers that are vectors of Xylella fastidiosa, the causal agent of bacterial leaf scorch, were found among both the cultivars and USNA seedling selections. Such data could allow for the screening and selection of elms resistant to economically important leafhoppers.

A 10-Year Evaluation of the Performance of Four Elm Cultivars in California, U.S.

In 1992, three elm (Ulmus spp.) cultivars reported to have tolerance to Dutch elm disease (DED) were planted in a field plot in Atherton, California, U.S. Cultivars included 'Prospector', 'Frontier', and 'American Liberty'. A fourth cultivar, 'Valley Forge', was added to the plot in 1999. American elms grown from seed were planted as controls. In the 10-year period from 1992 to 2002, tree height and trunk diameter were measured annually, and inspections for DED infections, elm leaf beetle activity, and other pests were conducted. In August 2003, one 'American Liberty' was found to be infected with DED. This is the only tree that has shown infection symptoms since the beginning of the study. Elm leaf beetle activity was highest in 1993 and 1994, causing substantial injury to 'American Liberty', 'Frontier', and controls. 'Prospector' sustained little injury. Other pest activity has been slight in most years. In 2002, 'Frontier', 'American Liberty', and controls were found to have equivalent trunk diameter growth, and all were significantly larger than 'Prospector'. After 10 years, 'Frontier' was tallest [11.3 m (37 ft)], 'Prospector' was shortest [6.9 m (23 ft)], and 'American Liberty' and controls were in between [9.6 and 10.3 m (32 and 34 ft), respectively]. 'Valley Forge' was monitored for 3 years and then removed from the study because of poor structure.

Suitability and Feeding Preference of Selected North American, European, and Asian Elm (Ulmus spp.) Biotypes to Elm Leaf Beetle (Coleoptera: Chrysomelidae)

Abstract Recently introduced North American elm cultivars, simple and complex elm hybrids of European and Asian parentage, and simple Asian hybrids of U. pumila and U. japonica parentage growing at The Morton Arboretum, Lisle, IL, were evaluated in laboratory bioassays for ovipositional response, and feeding preference and suitability for larvae and adults of the elm leaf beetle, Xanthogaleruca luteola (Muller). Larval and adult no-choice and adult multiple-choice feeding studies revealed that the North American cultivars of U. americana ‘Jefferson’ and U. americana ‘Valley Forge’, U. americana (diploid form), and U. americana were the least preferred for feeding and reproduction by the elm leaf beetle. Among simple and complex European hybrids, ‘Homestead’, ‘Patriot’, and ‘Prospector’ were least preferred and least suitable for larval development, feeding, and reproduction by adult elm leaf beetles. Hybrids of ‘Frontier’, ‘Pioneer’, and ‘Regal’; the simple Asian hybrids of ‘Cathedral’ and ‘New Horizon’; and U. pumila were more highly preferred for feeding and suitable for reproduction. The least preferred and least suitable North American biotypes of U. x americana ‘Jefferson’, U. americana ‘Valley Forge’, and U. americana (diploid form), simple and complex European hybrids of ‘Homestead’, ‘Patriot’, and ‘Prospector’, show promise for use in areas where the elm leaf beetle is persistent and for future elm breeding programs.

Variation among American Elm Clones in Long-term Dieback, Growth, and Survival following Ophiostoma Inoculation

Abstract Rooted stem cuttings of eight American elm (Ulmus americana L.) cultivars or selections, in addition to rooted stem cuttings of two non-American elm cultivars, ‘Prospector’ (U. wilsoniana Schneid.) and ‘Frontier’ (U. carpinifolia Gleditsch x U. parvifolia Jacq.), all planted in a randomized block, split-plot design, were inoculated on either one of two dates in May 1992 with a mixed spore suspension of Ophiostoma ulmi (Buisman) C. Nannf. and Ophiostoma novo-ulmi Brasier, the causal fungi for Dutch elm disease (DED). Crown dieback and survival were recorded once yearly for 7 years following inoculations, and height growth was measured after the sixth growing season. Analyses of variance and regression showed significant differences in disease severity among all clones tested. Among the American elms, crown dieback and mortality over time were least for ‘Valley Forge,’ ‘Princeton,’ and ‘New Harmony; ’ intermediate for ‘Delaware’ and selection R18-2; and greatest for selections 57845 and 11 and the cultivar American Liberty. Dieback and survival of ‘Prospector’ and ‘Frontier,’ the non-American elms, were comparable to that of the more disease-tolerant American elm clones. Height growth on surviving American elms for six years after inoculation was greatest for ‘Valley Forge’ and ‘Princeton’ and least for 57845, 11, and ‘American Liberty.’ Results demonstrate the ability of certain American elm cultivars and selections to respond and then recover from heavy doses of the two fungi which cause DED.

Leaf Element Content and Utilization of Maple and Elm as Hosts by the Potato Leafhopper (Homoptera: Cicadellidae)

Abstract Feeding injury and performance of the potato leafhopper, Empoasca fabae (Harris), was measured on two red maple clones (Acer rubrum L.), a Freeman maple cultivar (A. × freemanii E. Murray), two elm cultivars (Ulmus spp.), and an American elm clonal selection (U. americana L.), and was related to the leaf content of important nutritional elements. Significantly more eggs were laid and more nymphs became adults on American and Patriot elms than on the other clones. Although the mean number of eggs laid was not significantly different among the maple clones, nymphal survivorship was significantly higher on red maple 56026 than on the other maple clones. Although the number of eggs laid was linearly related to foliar nitrogen and phosphorus, survival of nymphs to adulthood was linearly related to foliar nitrogen. Significantly more leafhoppers from the wild population were collected from American elm, followed by Patriot elm and red maple 56026. Although none of the elms showed any evidence of feedin...

Elm Yellows Phytoplasma Lethal to Dutch Elm Disease-Resistant Ulmus americana Cultivars.

Ulmus americana (American elm) clonal cultivars Independence, New Harmony, and Valley Forge, together with the triploid putative hybrid cultivar Jefferson, were tested for reaction to the elm yellows (EY) phytoplasma. These cultivars all possess resistance to the fungal pathogen Ophiostoma novo-ulmi (1,4) but had not been screened for EY resistance or tolerance. Procedures and conditions of the test were similar to those used previously for assessing EY tolerance of Eurasian elm cultivars (3). In brief, 9 to 15 saplings of each cultivar and of U. americana raised from seed (susceptible controls), growing in a field plot at Ithaca, NY, were challenged by grafting their mainstems with bark patches from U. americana naturally affected by EY. Six to nine additional trees of each clone and of the seedling group were left untreated as controls. Inoculations were performed in July 1999, and trees were evaluated for symptoms in early September 2000. Multiple individuals in every inoculated group developed the syndrome typical of EY in U. americana: epinasty, foliar yellowing, yellow discoloration and necrosis of root and stem phloem, odor of methyl salicylate from moist discolored phloem on first exposure to air, defoliation or sudden permanent wilting, and death (2). The numbers of trees with these symptoms, of those inoculated, were: 9 of 9 Independence, 7 of 11 New Harmony, 10 of 14 Valley Forge, 3 of 13 Jefferson, and 12 of 15 trees grown from seed. Untreated controls remained asymptomatic, except for one tree of Valley Forge and two trees grown from seed that became infected naturally and had symptoms like those in the grafted trees. Based on these results, the elm cultivars named above are typical of U. americana in susceptibility to, and intolerance of, EY phytoplasmal infection. Effective EY resistance or tolerance in this species, although once thought to occur in rare individuals (2), remains undocumented.

Updated Checklist of Elm (Ulmus) Cultivars for use in North America

This checklist, with more than 175 entries, covers all elm cultivars introduced since 1964 and complete listings for Ulmus americana, U. japonica, U. parvifolia, U. pumila, U. wilsoniana, and all cultivars of putative hybrids in which at least one parent species was native to North America. Information on potential resistance to Dutch elm disease (DED), elm yellows, and other diseases and pests is included.

Breeding Elms for Resistance to Dutch Elm Disease

The use of elms (genus Ulmus) by mankind parallels the settlement and urbanization of Europe and North America (58, 97, 147), and Asia (3, 20, 22, 37, 92, 96, 108, 154). Richens (97) describes in detail the history and significance of elms in Europe and the origins of the numerous ancient elm cultivars, including the Roman introduction of the English elm into Great Britain from northern Portugal, and its later transport to Australia and New Zealand . In neolithic times the elm was used for many purposes; including food and fodder, medicinal preparations, timber for house and bam construc­ tion, bows, wheel hubs , water pipes, and other products . In modem times their graceful habit, valuable wood, adaptability, and tolerance of air pollutants have made them an important component of landscapes throughout the world. Beginning shortly after World War I, a new vascular wilt disease incited by Ophiostoma ulmi (Buism .) Nannf . (sensu lata) syn Ceratocystis ulmi (Buis . ) Moreau (Dutch elm disease) (DED) spread through the elm populations of Eurasia and North America leading to enormous economic and esthetic losses (12, 13, 40, 59). The massive loss of elms on several continents fostered numerous research programs ranging from basic investigations on host-patho­ gen-vector interactions to the use of systemic fungicides in chemotherapy (49, 63, 1 14, 1 52, 1 60). Genetic resistance to this pathogen was recognized from early research in both selected individuals and species (2, 49, 55-57, 72-75,

‘Aross Central Park’ Chinese Elm

Abstract Chinese elm (Ulmus parvifolia Jacq.) is an attractive, medium-sized ornamental tree with excellent urban-hardiness and pest resistance. Introduced into cultivation in the late 1700s, this species is commonly grown in parks, lawns, and streetside locations in the southern United States and California. There have been only three Chinese elm cultivars selected in this country (1, 2). Nurserymen have expressed their desire to find a Chinese elm with an increased level of cold hardiness so that the species could be used in cities in the northern United States. The ‘Aross Central Park’ Chinese elm is cold hardy to zone 6 (Arnold Arboretum hardiness zones) and will grow in protected areas in zone 5. Thus, it is the most cold hardy Chinese elm available.

Effects of Atmospheric Deposition on Efficacy Of Pesticides for Elm Leaf Beetle Control, Delaware, Co., Oh., 1985

Abstract One-year-old potted elm, Ulmus spp., cuttings were sprayed with insecticides and subjected to a combination of atmospheric pollutants and acid rain treatments to determine if insecticidal efficacies against elm leaf beetle adults were affected. The experiment was a factorial design. The factors were 3 insecticides (Dursban, Mavrik Aquaflow, Sevin XLR) applied at recommended rates; 2 simulated acid rain (SAR) treatments (4.0 pH, ambient); 2 elm cultivars ('Homestead,' 'Pioneer'); 3 atmospheric pollutant treatments (0.1 ppm 03, 0.2 ppm S02 plus 0.1 ppm 03, ambient); and 3 to 6 replicates each. Fumigations were in 4 open-top chambers ca. 3 m in diam and 2.5 m in height. SAR solutions were made by adjusting the pH of deionized water with 2 parts H2S04 and 1 part HN03. SAR was applied through beta fog nozzles at 69 kPa in chambers equipped with platforms, 1.2 m in diam, revolving at 4 rpm. Weekly SAR and fumigation treatments began 13 Jun. These treatments were 45 min (1.27 cm) SAR followed by fumigation for 5 days at 7 h/day. Elms that were ttt treated with insecticides, fumigants or SAR served as controls. Cuttings were sprayed to runoff on 8 Jul (32°C, 62% RH, winds calm) using a 11.4-liter c impressed C02 driven R&amp;D Model TS backpack sprayer equipped with a no. 5500 adjustable cone tip nozzle opened Vi turn from full closed at 206.8 kPa pressure. At 10 days postspray (Trial l)and at 37 Days postspray (Trial 2), insecticide efficacy was assessed by placing 5 or 10 elm leaf beetle adults in petri dishes with foliage from the different treatments. In Trial 1, foliage from 4 to 6 trees was used per treatment combination. In Trial 2, foliage from 6 trees was used per treatment combination (3 'Homestead' plus 3 'Pioneer'). Percent beetle mortality was determined in each petri dish after 48 h. Data were 3 lbjected to an angular transformation and analyzed by a 3 factor ANOVA at the 5% level. Where significant differences occurred, ANOVA was followed by an SNK multiple comparison test at the 5% level.

THE ELM AND ITS FUTURE. A Review of cultivatators more resistant to Dutch Elm Disease, methods for propagation and the distribution of Ulmus species in the British Isles

Although Dutch Elm Disease (DED) has destroyed many of the country's elms, the existence of known tolerant and more resistant strains of Ulmus species provides hope that the landscape of Britain will still be enhanced by the characteristic outline of this tree. Many species of elm, their varieties and cultivars are not only attractive, but are useful and interesting : for example, U. procera Salis. 'Suberosa'-the Cork-barked Elm-collected in France by Captain Collingwood Ingram. To what extent tolerance and resistance to DED exists among the elm species and their cultivars is under investigation, but preliminary screening trials carried out by the Forestry Commission indicates that some elm cultivars and selections are less susceptible to DED and that tolerance of, or resistance to, the disease can be expected.