Low-density Ceratocystis polonica inoculation of Norway spruce (Picea abies) triggers accumulation of monoterpenes with antifungal properties

Among the most devastating pests of Norway spruce (Picea abies) are the European spruce bark beetle (Ips typographus) and the associated pathogenic blue-stain fungus Ceratocystis polonica. Following attack and colonization, the beetle and the fungus must cope with induced host chemical defenses, such as monoterpenes that are generally thought to be toxic to both symbionts. The goal of this study was to better understand the response of Norway spruce following C. polonica inoculation at low density that does not overwhelm the tree and to identify monoterpenes mobilized toward the fungus. We inoculated healthy mature trees and monitored monoterpene profiles 2, 3, and 5 months post-inoculation. We also exposed three different C. polonica strains to the most abundant or significantly up-regulated monoterpenes to determine differences in monoterpene toxicity and resistance among strains. Total monoterpene levels, including limonene, were increased at 2 and 3 months after inoculation and had dropped after 5 months. In in vitro assays, all monoterpenes were inhibitory to C. polonica. Limonene and β-pinene were the most potent inhibitors of fungal growth. The extent of inhibition varied between the three strains tested. These results showed a defense response of Norway spruce to C. polonica, in which limonene may play a critical role in inhibiting the spread of the fungus. We also showed that differences between strains of C. polonica must be taken into account when assessing the role of the fungus in this bark beetle–symbiont system.     

蓝变真菌引起的欧洲云杉木质部解剖学特征及纤维素酶活性的变化

选择奥地利境内阿尔卑斯山健康欧洲云杉为对象,研究室内接种蓝变真菌(Ceratocystis polonica)引起的寄主树木韧皮部和木质部解剖学特征的变化,揭示蓝变真菌引起欧洲云杉枯萎的机制.结果表明:接种1周后的4株欧洲云杉的木质部组织内,蓝变区域显著增加,4～6周后蓝变区域不再增加;而在接种无菌琼脂的2株对照欧洲云杉的木质部组织内,没有检测到蓝变区域.采用生物化学分析和组织定位技术,确定接种真菌和无菌琼脂的欧洲云杉木质部区域纤维素酶的分布和活性变化.接种2周后剥皮取样检测,接种真菌的4株欧洲云杉的木质部组织内纤维素酶含量大幅度增加,其等电聚焦电泳显示明显的纤维素酶酶带;而在接种无菌琼脂的欧洲云杉木质部区域,纤维素酶含量分布较少,其等电聚焦电泳显示微弱的纤维素酶酶带.进一步证明蓝变真菌分泌的纤维素酶能利用寄主欧洲云杉木质部的纤维素,蓝变真菌是致死阿尔卑斯山境内欧洲云杉的重要病原菌.     

Spatiotemporal evidence of tree-growth resilience to climate variations for Yezo spruce(Picea jezoensis var. komarovii) on Changbai Mountain,Northeast China

Global warming-induced changes in tree-growth resilience to climate variations have been widely reported for mid-and high-latitude regions around the world. Most studies have focused on the spatial variability of trees in radial growth-climate relationships on Changbai Mountain in Northeast China, but little is known about temporal changes in tree growth in response to climate. We explored the stability of effect of climate variables on radial growth of Yezo spruce [Picea jezoensis Carr. var. komarovii(V.Vassil.) Cheng et L.K.Fu] at 1200, 1400, and 1600 m above sea level, representing low, middle, and upper ranges of the spruce-fir mixed forest on Changbai Mountain. The results showed that the relation between tree growth and climate did not vary with altitude, but the stability of the tree-growth-climate relationship did vary with altitude as the climate changed. Radial growth of Yezo spruce at allthree elevations was influenced primarily by maximum temperature during May(Tmax5) and mean minimum temperature from January to March(Tmin1-3). More specifically, the relationship strengthened significantly at lower elevations, but weakened significantly at higher elevation, and fluctuated at mid elevations since 1980.Increase in Tmin1-3 and decrease in Tmax5 were the main reasons for the decrease in the radial growth at three altitudes. The findings of this study clarified that the decrease in radial growth on Changbai Mountain is not a “divergence problem” of an unexpected decrease in tree growth in response to an increase in mean temperature and provides a reference for using tree-ring data to reconstruct climate patterns and/or predict the growth of trees under various climate change scenarios.     

Methyl jasmonate treatment of mature Norway spruce (Picea abies) trees increases the accumulation of terpenoid resin components and protects against infection by Ceratocystis polonica, a bark beetle-associated fungus

When conifers such as Picea abies Karst. (Norway spruce) are attacked by insects or pathogens, they often respond by producing increased quantities of terpenoid oleoresin. This response can be mimicked in young P. abies seedlings by treatment with methyl jasmonate (MJ). In this study, we determined the effects of MJ on terpenoids and other chemical defenses of mature P. abies, and investigated whether this treatment protected trees against attack by the blue-stain fungus Ceratocystis polonica (Siem.) C. Moreau, the most important fungal associate of the spruce bark beetle Ips typographus L. Methyl jasmonate treatment induced the formation of traumatic resin ducts in the developing xylem, enhanced resin flow and stimulated increased accumulation of monoterpenes, sesquiterpenes and diterpene resin acids. However, only minor changes were detected in terpene composition in response to MJ treatment and no changes in soluble phenolic concentration were measured. There was much variability in the timing and degree of response to MJ among clones. The observed chemical and anatomical changes in response to MJ treatment were correlated with increased resistance to C. polonica, suggesting that terpenoid oleoresin may function in defense against this pathogen.     

Effect of seed source elevation on bud opening of Yezo spruce (<Emphasis Type="Italic">Picea jezoensis</Emphasis>)

Spring frost damage is one of the obstacles to be overcome in establishing a Yezo spruce (Picea jezoensis Carr.) plantation. The timing of bud opening of Yezo spruce seedlings cultured from seeds collected at three different elevations (420, 700, and 1200m) in the Tokyo University Forest in Hokkaido was observed at two planting site elevations (610 and 750m) to investigate whether seed source elevation or planting site elevation affects the bud opening date. At both planting sites the bud opening dates were not significantly different among the seedling groups from different seed source elevations. On the other hand, bud opening dates of seedlings planted at the lower elevation site were significantly earlier than those planted in the higher elevation site. It could be deduced from this study that the environment of the planting site rather than seed source elevation affects the bud opening date of Yezo spruce.     

Lignin distribution in spruce (Picea abies) determined by mercurization with SEM-EDXA technique

Summary The lignin distribution between the middle lamella and the cell wall of spruce fibers has been determined by a new technique based on a mercurization of the lignin and a concomitant determination of mercury by the SEM-EDXA technique. The ratio of lignin in the middle lamella at the cell corners to the lignin in the secondary wall was 2.5±0.6 for latewood and 2.4±0.6 for earlywood. This gives a lignin content of 55–58% in the true middle lamella in the cell corners. The reactivity to mercuric acetate of different wood elements was determined in separate experiments. Fractions enriched in ray cells, middle lamella, and compression wood all reacted at the same rate as the whole wood; about one mole of mercury was incorporated per mole of lignin (C₉-unit).     

Mountain pine beetle‐associated blue‐stain fungi in lodgepole × jack pine hybrids near Grande Prairie,Alberta (Canada)

The mountain pine beetle (MPB), the most serious pest of lodgepole pine in mountainous western Canada, spread northeastward into lodgepole × jack pine hybrids in the boreal forest of Alberta in 2006. The MPB vectors three species of blue‐stain fungi, which contribute to the success of the beetles. These fungi were isolated from MPB larvae and galleries in several lodgepole × jack pine stands in the Grande Prairie region of northwestern Alberta in autumn 2006 and winter and spring 2007. Fungi were recovered from more than 95% of gallery systems. The three fungi were similarly prevalent but Ophiostoma montium was the most frequently isolated fungus at each sampling point, isolated from 72% to 90% of gallery systems compared with 63% to 78% for Grosmannia clavigera, and 61% to 86% for Leptographium longiclavatum. Ophiostoma montium and G. clavigera were isolated from more larvae than gallery samples, with the opposite true for L. longiclavatum. Most gallery systems contained multiple fungi with three fungi per gallery system being more common in autumn and winter and two fungi more common in the spring. The combination of G. clavigera and L. longiclavatum was less common among gallery systems with two fungi than either of the pairwise combinations containing O. montium. Fungal prevalence was the same above and below snow level. The prevalence of the three fungi did not differ significantly among stands sampled in the spring but stands with more G. clavigera tended to have less L. longiclavatum. The winter of 2006–2007 was colder than average throughout Alberta with temperatures below ?30°C in November, January and February, and all three fungi were present after the cold winter while most larvae had died, suggesting that overwintering mortality of the fungi will not limit persistence and spread of MPB in the boreal forest.     

Resistance to the green spruce aphid (Elatobium abietinum Walker) in progenies of Sitka spruce (Picea sitchensis (Bong) Carr.)

Damage caused by Elatobium abietinum was estimated as needle loss in a progeny trial of Sitka spruce in Denmark in 1990 and 1992. The parents of the progeny had been selected for putative aphid resistance during a massive attack of aphids in 1957. Needle loss was significantly less in the progeny than in a standard provenance. Family heritability was estimated as 0.72 (P>0.0001). Aphid damage had an impact on growth and vigour of trees following warm winters in 1989 and since, but no correlation could be found between growth parameters and damage of different families. Due to high heritability and large variation, high gains are expected by breeding. Practical and theoretical consequences of including aphid resistance in breeding programmes of Sitka spruce are discussed.     

Variation in black spruce (<Emphasis Type="Italic">Picea mariana</Emphasis> (Mill.) BSP) wood quality after thinning

• Introduction   

Commercial thinning (CT) could contribute to increase short-term tree growth and be beneficial in a cold climate, as in boreal regions. Thus, growth rate, ring density and flexural modulus of elasticity (MOE) of trees may change after CT. Moreover, mechanical wood properties vary with position in the tree, and there is a need to develop optimal log allocation strategies in order to allocate logs to their best use.     

The occurrence of p-hydroxyphenylpropane units in the middle-lamella lignin of spruce (Picea abies)

Summary A sieving technique has been developed for the separation of middle-lamella fragments. The middle-lamella fraction as well as the whole wood and compression wood from Picea abies have been analysed by nitrobenzene oxidation and acidolysis in order to determine the content of p-hydroxyphenylpropane units in the middle-lamella lignin. These analyses revealed only traces of p-hydroxyphenylpropane units in the whole wood and in the middle-lamella fraction but considerable amounts were found in compression-wood lignin. This points to the fact that middle-lamella lignin is of guaiacyl nature and that earlier results reporting high proportions of p-hydroxyphenylpropane units in the middle lamella-lignin may be due to the inclusion of compression wood in the fraction studied. The acidolysis experiments further indicate that the middle-lamella lignin has fewer uncondensed -0-4 aryl ether structures than the whole wood lignin.The skilful technical assistance of Mrs. Britta Samuelsson and Mr. Johan Lindberg is highly appreciated. The author also thanks Dr. Knut Lundquist for supplying some of the reference compounds, and Dr. Hanne-Lise Hardell for help with the microscopic pictures     

Vertical and horizontal water redistribution in Norway spruce (Picea abies) roots in the Moravian Upland

Hydraulic redistribution (HR) by roots of large Norway spruce (Picea abies (L.) Karst.) trees was investigated by means of sap flow measurements made with the heat field deformation method. Irrigation was applied to a limited portion of the root system to steepen gradients of water potential in the soil and thus enhance rates of HR. On completion of the sap flow measurements, and to aid in their interpretation, the structure of the root system of seven of the investigated trees was exposed to a depth of 30 cm with a supersonic air-stream (air-spade). Before irrigation, vertical redistribution of water was observed in large coarse roots and some adjacent small lateral roots. Immediately after localized irrigation, horizontal redistribution of water from watered roots to dry roots via the stem base was demonstrated. The amount of horizontal distribution depended on the position of the receiving roots relative to the watered roots and the absorbing area of the watered root. No redistribution from watered roots via dry soil to roots of neighboring trees was detected. Responses of sap flow to localized irrigation were more pronounced in small lateral roots than in large branching roots where release and uptake of water are integrated. Sap flow measurements with multi-point sensors along radii in large lateral roots demonstrated water extraction from different soil horizons. We conclude that synchronous measurements of sap flow in both small and large lateral roots are needed to study water absorption and transport in tree root systems.     

Effects of benomyl and captan on growth and mycorrhizal colonization of Sitka‐spruce (Picea sitchensis) and ash (Fraxinus excelsior) in Irish nursery soil

The effects of two fungicides (benomyl and captan ‐ at recommended doses and up to three soil drenches) on root development and mycorrhizal colonization of Sitka‐spruce (Picea sitchensis) and ash (Fraxinus excelsior) were examined after 20 weeks growth, under environmentally controlled conditions, in soil from an Irish tree nursery. Although four mycorrhizal types have been found on Sitka‐spruce at the nursery, only one ectomycorrhizal type (Piceirhiza horti‐inflata) was identified on the short roots in this study. An inoculant (Vaminoc: MicroBio Ltd, Hemel Hempstead, UK) was used to inoculate ash and 20‐week‐old seedlings had a higher arbuscular mycorrhizal (AM) colonization in comparison with uninoculated controls. Multiple applications (2–3) of benomyl reduced the length of root and shoot and shoot dry mass of Sitka‐spruce, whereas in ash, it only depressed root length. Benomyl decreased the numbers of ectomycorrhizas of Sitka‐spruce and arbuscular mycorrhizal colonization of Vaminoc‐inoculated ash. A single application of captan stimulated root length and ectomycorrhizal colonization of Sitka‐spruce and root dry mass in ash compared with uninoculated controls. Applications of captan reduced arbuscular mycorrhizal colonization of Vaminoc‐inoculated ash to levels near to those of uninoculated controls. Of the two fungicides used, benomyl had the most deleterious effect on root length and mycorrhizal colonization of Sitka‐spruce and ash.     

Uncertainty in detecting climate change impact on the projected yield of black spruce (Picea mariana)

The empirical growth and yield (G&Y) curves used in most timber supply models assume that growth conditions are invariable over time, which may not be correct given the projected future climate. However, errors in G&Y models can be quite large, and we therefore wanted to know the probability of detecting climate change-induced growth anomalies as a departure from current G&Y predictions. The work was carried out in a boreal forest study area in Eastern Canada, where Picea mariana Mill. BSP (black spruce) is the dominant species. Climate change effects were incorporated into G&Y predictions as correction factors obtained from process-based simulations of growth using current or projected climate. Uncertainty in G&Y projections was quantified through the inclusion of sampling and model errors in a bootstrap re-sampling scheme that yielded a percentile distribution of possible differences between G&Y curves that included or did not include climate change effects. Results yielded an average projected increase in productivity of 29% under future climate conditions for the black spruce strata in the study area. The probability of the climate change-modified G&Y predictions being significantly different from the current G&Y projections is 75% when considering the sampling error alone, and of 67% when both the sampling and modelling errors are included. Although incomplete in terms of what sources of error have been included, this study demonstrates the type of information that can be generated on the propagation of uncertainty in G&Y projections and, ultimately, on timber supply.     

Altitudinal differences in the leaf fitness of juvenile and mature alpine spruce trees (Picea crassifolia)

In many plant species, leaf morphology varies with altitude, an effect that has been attributed to temperature. It remains uncertain whether such a trend applies equally to juvenile and mature trees across altitudinal gradients in semi-arid mountain regions. We examined altitude-related differences in a variety of needle characteristics of juvenile (2-m tall) and mature (5-m tall) alpine spruce (Picea crassifolia Kom.) trees growing at altitudes between 2501 and 3450 m in the Qilian Mountains of northwest China. We found that stable carbon isotope composition (delta(13)C), area- and mass-based leaf nitrogen concentration (N(a), N(m)), number of stomata per gram of nitrogen (St/N), number of stomata per unit leaf mass (St/LM), projected leaf area per 100 needles (LA) and leaf mass per unit area (LMA) varied nonlinearly with altitude for both juvenile and mature trees, with a relationship reversal point at about 3100 m. Stomatal density (SD) of juvenile trees remained unchanged with altitude, whereas SD and stomatal number per unit length (SNL) of mature spruce initially increased with altitude, but subsequently decreased. Although several measured indices were generally found to be higher in mature trees than in juvenile trees, N(m), leaf carbon concentration (C(m)), leaf water concentration (LWC), St/N, LA and St/LM showed inconsistent differences between trees of different ages along the altitudinal gradient. In both juvenile and mature trees, delta(13)C correlated significantly with LMA, N(m), N(a), SNL, St/LM and St/N. Stomatal density, LWC and LA were only significantly correlated with delta(13)C in mature trees. These findings suggest that there are distinct ecophysiological differences between the needles of juvenile and mature trees that determine their response to changes in altitude in semi-arid mountainous regions. Variations in the fitness of forests of different ages may have important implications for modeling forest responses to changes in environmental conditions, such as predicted future temperature increases in high altitude areas associated with climate change.     

Antagonists of Fomes annosus in the rhizosphere of grey alder (Alnus incana) and Norway spruce (Picea abies)

A comparison was made of the fungistatic effects of the root microflora of grey alder and Norway spruce with Fomes annosus as test fungus. The significantly higher frequency of actinomycetes in the alder rhizosphere probably constituted the main difference in this respect. The importance of fungi seemed to be about equal in the rhizosphere of the two tree species. Methods for studies of antagonism are tested and discussed.     

Co‐occurrence of the ascomycete Lophodermium piceae and the rust fungus Chrysomyxa abietis in Norway spruce needles

The frequency of needles and the proportion of needle segments infected by Lophodermium piceae were compared in symptomless and Chrysomyxa abietis‐infected, 1‐year‐old needles of Picea abies. In late spring, symptomless needles from both rust‐infected and healthy saplings were sampled. In addition, rust‐infected, totally chlorotic needles and needles with chlorosis along about half their length from the diseased trees were examined. In all three stands, the proportion of segments infected by L. piceae was larger in the rust‐infected half of the needle than in the symptomless half; but the difference was statistically significant in only one of the stands. The proportion of L. piceae‐infected segments among the nonrust‐infected needles was the same as that found for the uninfected half of rust‐infected needles (after correction for size differences). No differences in the proportion of L. piceae‐infected segments were found between the totally chlorotic, rust‐infected needles and the green needles of diseased or healthy trees.     

Effects of photoperiod and temperature on the timing of bud burst in Norway spruce (Picea abies)

We examined the effects of several photoperiod and temperature regimes imposed during the winter-spring period on the timing of bud burst in rooted cuttings of Norway spruce (Picea abies (L.) Karst.) grown in a greenhouse in Finland. The treatments were initiated in November and December after the cuttings had been exposed to natural chilling and freezing events. Irrespective of the treatments applied, time to bud burst decreased with increased duration of previous exposure to natural chilling and freezing events. Fluctuating day/night temperatures and continuous lengthening of the photoperiod hastened bud burst. Shortening the photoperiod delayed bud burst, suggesting that little or no ontogenetic development toward bud burst takes place during mild periods before the winter solstice. In the case of climatic warming, this phenomenon may prevent the premature onset of growth that has been predicted by computer simulations with models that only consider temperature regulation of bud burst.     

The effects of Arceuthobium sichuanense infection on needles and current‐year shoots of mature and young Qinghai spruce (Picea crassifolia) trees

Arceuthobium sichuanense is a hemiparasitic angiosperm that infects Qinghai spruce (Picea crassifolia Kom.) in Qinghai province, China, and causes severe damage to spruce forests in Qinghai‐Tibet Plateau. In this study, the impact of A. sichuanense infection on mature and young trees of Qinghai spruce was evaluated by examining needle and current‐year shoot morphology, needle water and nitrogen‐use efficiency (NUE) and needle nitrogen concentration. The most apparent effect of A. sichuanense infection was a significant reduction in both needle size distal to infection and current‐year shoot length in the infected branches (p < 0.001). Per cent reductions in needle and current‐year shoot length were similar between mature and young trees (58.9 vs. 56.3%; 59.7 vs. 62.9%). There was a high degree of correlation in foliar δ¹⁵N values between the dwarf mistletoe and its host trees (R² = 0.9017, p < 0.001), while the foliar δ¹³C values of A. sichuanense were similar to those of infected mature and young spruce trees. The dwarf mistletoe infection also resulted in a significant decrease in host needle N concentration and δ¹³C values (p < 0.001). The per cent reduction in needle N concentration in young trees was nearly twice as much as that in mature trees (20.49 vs. 11.54%), while the per cent reduction in needle δ¹³C values was similar between young and mature trees (?0.98 vs.?1.1‰). The NUE in mature trees was not affected by A. sichuanense infection, but the NUE in young trees was increased by the infection.     

Changes in soluble-phenol content of Norway-spruce (Picea abies) phloem in response to wounding and inoculation with Ophiostoma polonicum

The aim of this study was to investigate the temporal changes in Norway-spruce (Picea abies) phloem phenolics during wound-induced response. Two Norway spruces were inoculated with Ophiostoma polonicum and sterile agar; unwounded phloem was simultaneously tested as control. Both unwounded and inoculated phloem were then sampled 6, 11, 21, 30, and 60 days later. Monophenols were analysed by HPLC, and the tanning capacity of the phloem extracts was estimated from their ability to precipitate proteins. The response to inoculation was characterized by radical changes in the phloem phenolic composition. Initially, an increase in (+)-catechin concentration was observed, concomitant with a slow decrease in both glycoside concentrations and tanning capacity. After day 6, this decrease was accelerated in the event of fungus inoculation. The appearance of aglycones did not take place during the decrease in glycosides, but was delayed. The phenolic response of Norway-spruce phloem to inoculation is modulated by the presence of the fungus and is focused on the formation of insoluble compounds.