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.     

First report on the Dutch elm disease pathogen Ophiostoma novo‐ulmi from Latvia

During 2017, Dutch elm disease was investigated on 67 Ulmus glabra and 29 Ulmus laevis samples from 28 sites in Latvia. The presence of Ophiostoma novo‐ulmi was detected in 61.2% of the samples from U. glabra and in 34.5% of the samples from U. laevis. In 11% of cases, hybrids between subsp. novo‐ulmi and subsp. americana were identified, particularly in the sites in the southern part of Latvia. This study presents the first verified record of Ophiostoma novo‐ulmi and its subspecies in Latvia.     

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.     

Detection of differential changes in lignin composition of elm xylem tissues inoculated with Ophiostoma novo‐ulmi using Fourier transform‐infrared spectroscopy

Differences in elm susceptibility against Ophiostoma novo‐ulmi have been related with differences in timing and degree of the tree defence responses. In this study, we used Fourier transform‐infrared spectroscopy, coupled with chemometric methods, to detect progressive changes in the metabolic profile of Ulmus minor and U. minor × U. pumila xylem tissues after inoculation with O. novo‐ulmi. Differences between control and inoculated trees were detected at 30 and 60 days post‐inoculation (dpi) in U. minor, and at 15, 30 and 60 dpi in U. minor × U. pumila. These differences were related with increased levels of lignin in the xylem tissues, suggesting an earlier defence response to the infection in the hybrids.     

A scanning electron microscope study of cell wall degradation in elm wood by aggressive and non-aggressive isolates of Ophiostoma ulmi

Degradation of cell walls in elm wood tissue (Ulmus americand) by aggressive and non-aggressive isolates of Ophiostoma ulmi was studied by scanning electron microscopy. Xylem vessel walls were much more affected after infection with the aggressive isolate than after infection with the non-aggressive one.     

Further studies on pathogenicity in Ceratocystis ulmi1

Inoculation experiments on Ulmus procera, U. glabra and U. pumila with isolates of Ceratocystis ulmi from Canada, the United States, England, France, the Netherlands and Iran confirmed earlier work on the correlation between cultural characters and pathogenicity. Inocula-     

不同品种榆树抗榆蓝叶甲危害能力的研究

通过野外调查、套笼试验及室内测定的办法,分析和测定了7种榆树对食叶害虫榆蓝叶甲的抗危害能力,得出黑龙江省榆树的抗危害能力从强至弱顺序依次为剌榆、裂叶榆、黑榆、黄榆、垂榆、椿榆、家榆。     

Cellulolytic activity and virulence of Ophiostoma ulmi and O. novo‐ulmi isolates

The cellulolytic activity (exoglucanase, endoglucanase and β‐glucosidase) of Ophiostoma ulmi (four isolates), O. novo‐ulmi (19 isolates) and ‘fast‐waxy’ (five isolates) was determined in growth media containing carboxymethylcellulose (CMC) and cellulose powder. Differences in enzyme activities were observed among isolates, irrespective of the species and substrate used. Inoculation experiments on Ulmus minor with randomly selected isolates of O. ulmi (two isolates), O. novo‐ulmi (five isolates) and ‘fast‐waxy’ (two isolates) were also performed. Disease was assessed as the percentage of leaves showing yellowing and browning. Ophiostoma novo‐ulmi and ‘fast‐waxy’ isolates exhibited a great variability in their capacities to cause the disease. In the presence of CMC, a significant correlation between the activity of exoglucanase and β‐glucosidase in vitro and virulence was found.     

Effects of soil compaction on growth variables in Cappadocian maple (<Emphasis Type="Italic">Acer cappadocicum</Emphasis>) seedlings

This study investigates the effects of increasing soil penetration resistance (SPR) on seedling morphology and seedling architecture. When seedlings of deciduous Cappadocian maple (Acer cappadocicum Gled.) were grown in a greenhouse in a loamy soil under a wide range of soil compactions, all morphological variables studied changed significantly with increasing SPR. The relationships between increasing SPR and all morphological responses except lateral root length followed a negative quadratic curve. All biomass variables except lateral root biomass showed a bell-shaped response with respect to SPR, with a maximum biomass variable between 0.6 and 1.2 MPa, decreasing at higher soil compaction values. All allocation ratios were significantly affected by soil penetration resistance. Biomass allocation to roots was also affected by soil compaction. There was not a significant relationship between the specific stem length and increasing soil penetration resistance. The specific root length showed two trends to increasing SPR; it first decreased in response to the moderate compaction treatment (up to about 1.2 MPa), then increased significantly. We concluded that increasing soil compaction caused morphological changes to root and shoot sections of A. cappadocicum seedlings.     

The occurrence of microbes among buds of deciduous trees

Populations of fungi and bacteria dominated by white yeasts and resembling those associated with leaves, were isolated from outer sheathing scales of dormant buds of 7 genera of deciduous trees (Fagus, Aesculus, Acer, Ulmus, Betula, Populus and Quercus) but the internal parts of Tilia and Fraxinus buds were also consistently contaminated. The importance of using samples of homogenized tissue and the temperature of the agar media are discussed.     

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.     

First report of Erysiphe kenjiana causing powdery mildew of elm in Romania

Erysiphe kenjiana is an Asian fungus causing powdery mildew of Ulmus spp. In 2017, 10 years after its introduction in Europe, it was detected in Romania on Ulmus pumila, the Siberian elm, which is cultivated in urban environments as an ornamental and shade tree. The identification of the fungus was based on morphological characteristics and molecular data (rDNA internal transcribed spacer region). This is the first report of E. kenjiana in Romania, and only the third from a European country.     

Inhibition of Ceratocystis ulmi by mansonones A,C, D,E, F,and G isolated from Ulmus americana

Six mansonoes, previously isolated from Ulmus americana L. infected by Ceratocystis ulmi (Buis.) C. Moreau, were assayed for their inhibitory activity against several strains of the fungus. Mansonone A was most effective in inhibiting the linear growth of six strains of C. ulmi tested. A mixture of the pure mansonones, recombined at their original concentrations, was less inhibitory to the three aggressive strains of C. ulmi than the non-aggressive ones. The total mansonone fraction accounted for all the inhibition of the three non-aggressive strains.     

辽西半干旱地区矸石废弃地造林树种筛选

对辽西半干旱地区矸石废弃地以排矸年龄为界限,划分为4个类型,在不同类型上进行人工造林试验,通过对比试验筛选适生造林树种。结果表明:Ⅰ类矸石废弃地适宜的造林树种排序为紫穗槐>锦鸡儿>白榆>沙棘>沙枣;在Ⅱ类矸石废弃地上适宜造林树种排序为紫穗槐>锦鸡儿>火炬树>臭椿>白榆>刺槐;Ⅲ类矸石废弃地适宜的造林树种排序为火炬树>臭椿>刺槐>白榆>杨树>侧柏>樟子松;Ⅳ类地区矸石废弃地适宜的造林树种排序为火炬树>臭椿>刺槐>杨树>旱柳>白榆>侧柏>樟子松。     

2种土壤质地和覆膜措施对金叶榆嫩枝扦插效果的影响

在国营桓仁满族自治县黑沟林场山地,通过2种土壤质地和覆膜措施进行了金叶榆嫩枝扦插试验,结果表明:砂质壤土比黏质壤土,覆膜比不覆膜均能提高金叶榆嫩枝扦插的生长量和成活率。     

长序榆天然更新调查研究

对福建省南平市来舟镇东山村残存的珍稀濒危树种长序榆的天然更新状况进行研究,结果表明:长序榆大树虽然生长旺盛,但林下天然更新不良。长序榆果实风播有效距离仅为30m,且由于它是阳性树种,不耐蔽荫,在阳光不足的林下种子难于成苗,幼苗难以成树,天然更新能力弱,这些是它种群数量少,处于濒危状态的主要原因。     

白榆幼苗水分生理特征的研究

对乌兰察布市察右后旗当郎忽洞苏木人工造林地土壤含水量及白榆幼苗水分生理特征进行研究,结果表明：由于长期干旱,样地土壤含水量降到7．24％以下,白榆自然含水量为64．13％,束缚水与自由水比值为1．33,其自然饱和亏缺为10．06％。持水力测定表明：白榆的持水力曲线斜率相对小。PV曲线分析表明,白榆的ψπ100和ψπ0值为7．97MPa。蒸腾速率日进程变化分析表明：白榆的“午休”现象明显。     

Inonotus dryadeus in North America: new records,hosts, distribution and incidence

Inonotus dryadeus is newly reported in eastern Canada (Ontario) on Acer platanoides and Acer saccharinum, both new hosts, and Ulmus americana. The host range, incidence, and available distributional data in continental North America are summarized in a table. The fungus occurs primarily on Quercus, Abies, and Tsuga. Occasionally, it is found on Picea and Pinus as well as many other hardwood trees. Colder climates and host differences in the boreal forests may be limiting distributional factors. Inonotus dryadeus appears to favour very old trees. The maximum known width of the fruiting body is revised upward to 74.9 cm.     

Evaluation of the inorganic compound leakage and carbohydrates as indicator of physiological potential of <Emphasis Type="Italic">Ulmus parvifolia</Emphasis> seeds

Inorganic compound leakage and change of carbohydrate were measured in Ulmus parvifolia seeds throughout accelerated aging under 35°C and 75% relative humidity (RH) to investigate whether these indicators can be used as a rapid vigor test for efficient seed bank management. Accelerated aging seeds treated for 0–14 days exhibited loss of germinability in the longest aging treated seeds (11%, 14 days) compared to a good performance of 52% for control (0 day) seeds. Leachate electrical conductivity (EC) increase had strong negative correlation with seed vigor (−0.9). Magnesium ion concentration in electrolyte leakage from artificial aged seeds showed positive correlation (r = 0.94, P < 0.01). The ratios of inorganic ions showed that K⁺/Mg²⁺, Ca²⁺/Mg²⁺, and Na⁺/Mg²⁺ were inversely correlated with germination (−0.93, −0.82, and −0.91, respectively). Increases in starch and total soluble sugar content in aged seeds were associated with a decrease in seed vigor. In conclusion, EC, magnesium ion concentration, K⁺/Mg²⁺, Ca²⁺/Mg²⁺, and Na⁺/Mg²⁺ ratios and starch and total soluble sugar content could provide a sensitive and accurate index for the assessment of U. parvifolia seed vigor.     

人工幼林蒸腾规律的研究

对刺槐、紫穗槐、河北杨、白榆、侧柏等新造人工幼林生长期蒸腾的研究表明:蒸强日间均值12～14时最大,0～2时最小,凌晨5～6时渐升。昼间均值顺序是:紫穗槐>刺槐>河北杨>白榆>侧柏。回归建立的五种树种蒸强与环境因子关系的非线性回归方程,相关系数大于0.77,差异极显著。五个方程偏相关系数顺序是:光照强度>气温>风速>相对湿度。蒸腾耗水量月均值顺序是:刺槐>紫穗槐>河北杨>白榆>侧柏。