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.     

Water content and bark thickness of Norway spruce (Picea abies) stems: phloem water capacitance and xylem sap flow

To determine the relationship between phloem transport and changes in phloem water content, we measured temporal and spatial variations in water content and sucrose, glucose and fructose concentrations in phloem samples and phloem exudates of 70- and 30-year-old Norway spruce trees (Picea abies (L.) Karst.). Large temporal and spatial variations in phloem water content (1.4-2.6 mg mg(dw)(-1)) and phloem total sugar concentration (31-70 mg g(dw)(-1)) paralleled each other (r(2) = 0.83, P < 0.0001 for the temporal profile and r(2) = 0.96, P < 0.008 for the spatial profile), indicating that phloem water content depends on the total amount of sugar to be transferred. Changes in phloem water content were unrelated to changes in bark thickness. Maximum changes in phloem water content calculated from dendrometer readings were only 8-11% of the maximum measured changes in phloem water content, indicating that reversible changes in bark thickness did not reflect changes in internal water relations. We also studied the relationship between xylem sap velocity and changes in bark thickness in 70-year-old trees during summer 1999 and winter 1999-2000. Sap flow occurred sporadically throughout the winter, but there was no relationship between bark shrinkage or swelling and sap velocity. In winter, mean daily xylem sap velocity was significantly correlated with mean daily vapor pressure deficit and air temperature (P < 0.0001, in both cases). Changes in bark thickness corresponded with both short- and long-term changes in relative humidity, in both winter and summer. Under controlled conditions at > 0 degrees C, changes in relative humidity alone caused changes in thickness of boiled bark samples. Because living bark of Norway spruce trees contains large areas with crushed and dead sieve cell zones-up to 24% of the bark is air-filled space-we suggest that this space can compensate for volume changes in living phloem cells independently of total tissue water content. We conclude that changes in bark thickness are not indicative of changes in either phloem water capacitance or xylem sap flow.     

Fungi in bark peeling wounds of Picea abies in central Sweden

A total of 210 Norway spruce trees with stem wounds resulting from bark peeling by moose (Alces alces) were examined in three 45–50-year-old stands that contained 20-30% of damaged trees. Injured stems were between 8 and 40 cm diameter at breast height (d.b.h.) and showed 1 to 23-year-old wounds. Wounds varied in size from 2 to 4815 cm². The size of injury correlated negatively with the age of the injury (r=-0.24; p=0.004), and positive correlation was established between the age of the injury and d.b.h. of the wounded tree (r=0.50; p=0.0001). Each wound was sampled once using an increment borer and fungi were isolated. Among basidiomycetes, Stereum sanguinolentum was the most common (isolated from 26.7% of the damaged stems). Other common species were Cylindrobasidium evolvens (23.8%), Amylostereum areolatum (5.2%), A. chailletii (0.5%), Heterobasidion annosum (5.2%), Peni-ophorapithya (1.4%), Sistotrema brinkmannii (1.0%). The ascomycete Nectria fuckeliana was the most common among all fungi (present in 35.7% of bark peeling wounds). The frequency of S. sanguinolentum infection correlated positively with the age of the injury (r=0.27; p=0.001) and the opposite relationship was revealed for C. evolvens (r=?0.30; p=0.0001). Furthermore, C. evolvens infection correlated positively with the wound size (r=0.30; p=0.0001) and negatively with the tree d.b.h. (r=?0.20; p=0.004). A positive correlation was found between tree d. b. h. and the occurrence in stems of H. annosum (r=0.23; p=0.001 and N. fuckeliana (r=0.23; p=0.0006). The spruce bark beetle Dendroctonus micans attacked 14.8% of wounded trees. Presence in stems of N. fuckeliana was associated significantly with the D. micans attack (r=0.190; p =0.006; χ² test: p=0.01). Except for a negative correlation between infections of S. sanguinolentum and H. annosum (r=-0.140; p=0.04), no significant relationship between fungal species was found.     

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.     

Chrysomyxa ledi,a new rust fungus sporulating in cone scales of Picea abies in Finland

Abstract

Seasonal fruiting and sporulation of cone rusts were investigated in Norway spruce cones during the growing season of 2007, a year after an excellent cone crop and a severe outbreak of rust. Current-year and 1-year-old cones were collected bimonthly to monthly from case-stands in southern and northern Finland and checked for rust fruitbodies. A previously unreported species of rust formed spermogonia and aecia, and sporulated on the cone scales of Norway spruce in two study areas. Morphologically, the rust was distinct from other spruce cone rusts and, based on ultrastructure of aecia and aeciospores, most closely resembled Chrysomyxa ledi. Molecular analysis of the aeciospores confirmed that the rust belonged to the C. ledi/C. rhododendri complex. The rust fruited frequently but only colonized a few scales per cone and presumably had a minor effect on cone development and seed crop.     

Stilbenes and resin acids in relation to the penetration of Heterobasidion annosum through the bark of Picea abies

Concentrations of the stilbene glucosides astringin and isorhapontin, which ranged from 5 to 50 mg/g fresh weight in Picea abies bark, decreased in response to in vivo infection with the root-rot fungus Heterobasidion annosum. The initial concentration of the stilbene astringin was negatively correlated with the depth of hyphal penetration. Resin acid contents increased following infec-tion, but were not correlated with the depth of hyphal penetration. The spatial distribution of stilbene glucosides in spruce stem, root collar and root bark, and the seasonal variations in con-centration, were estimated.     

Ectomycorrhiza formation and growth of Picea abies seedlings inoculated with alginate-bead fungal inoculum in peat and bark compost substrates

Sphagnum peat (peat), spruce bark compost (compost), peat +perlite (1 : 1, v : v) and compost + perlite (1 : 1, v : v)substrates were inoculated with vegetative alginate-bead inoculumof Hebeloma crustuliniforme, Hygrophorus agathosmus or Paxillusinvolutus or left uninoculated prior to the addition of Norwayspruce seed. Growth and percentage of mycorrhization of barerootseedlings cultivated in a greenhouse were evaluated after thefirst growing season. Seedlings grown in peat-based substrateshad significantly larger aboveground and total dry weight, butsignificantly lower mycorrhization percentage than those grownin compost-based substrates. There were no significant differencesbetween fungal treatments (including control) for both the percentageof mycorrhization and growth of seedlings. The artificiallyintroduced fungi were not efficient in mycorrhizal formation– naturally occurring fungi were common in all treatments.However, a significant interaction between substrate and fungustreatments in root dry weight was detected. Hebeloma-inoculatedseedlings grown in peat showed the highest value of root dryweight. This fact indicates other possible effects of the fungion root growth independent of mycorrhization. Growth parameterswere negatively correlated with the extent of mycorrhization,indicating allocation of host photosynthates to the fungi. Tothe best of our knowledge, operational inoculation of Norwayspruce seedlings with the test fungi has not been reported previously.     

Transfer of the P-type of Heterobasidion annosum from old-growth stumps of Picea abies to Picea abies and Larix×eurolepis

The infection of Picea abies and Larix x eurolepis by Heterobasidion annosum was studied in felled trees in Sweden. Thinnings were carried out in two stands of L. x eurolepis, 15 and 20 years old, and in a 25-year-old stand of P. abies, established on a site heavily infected by H. annosum. The 15- and 20-year-old L. x eurolepis stands exhibited the greatest incidence of butt rot with infections amounting to 38 and 57%, respectively, of removed trees. The incidence of butt rot in the P. abies stand was only 5%. Heterobasidion annosum was the main butt rot causing fungus. All isolates of H. annosum were of the P-intersterility group. Transfer of H. annosum from old-growth P. abies stumps to trees felled in the thinning of the next generation was demonstrated by somatic incompatibility tests. However, the majority of infections could not be connected with decay already established in the previous generation. In L. c eurolepis, rot columns were frequent, including also several genotypes in the same stem, and typically positioned in the inner sapwood. The few infections of P. abies were situated in the heartwood.     

Allozyme Variation of Picea abies in Poland

The aim of this study was to determine the levels and patterns of allozyme variation among 29 populations of Norway spruce [ Picea abies (L.) Karst.] from Poland. Thirteen investigated isoenzyme systems were encoded by 27 gene loci and, on average, 71% of the loci per population were polymorphic. The average and effective numbers of alleles per locus were 2.17 and 1.26, respectively, while the expected heterozygosity was 0.156. A relatively low allozyme differentiation among populations from north-eastern and southern Poland was observed ( F ST = 0.028, mean genetic distance D = 0.005). The results suggest that historical events and extensive gene flow played an important role in the distribution of the observed allozyme differentiation of Norway spruce in Poland.     

Wound occlusion and decay in Picea abies stems

In forest stands, Picea abies is commonly subjected to logging and bark stripping injuries. Most mechanical wounds do not exceed 300 cm², but their pathological consequences are unclear. The aim of the study was to estimate the rate of wound occlusion and the probability of decay in P. abies stems in relation to initial wound size and wounding season. The study included forty-five stems with 1-, 2-, 3-, 4- and 5-cm-wide by 15-cm-long wounds (15–75 cm²), and eighty-three stems with 15-cm-wide by 20-cm-long wounds (300 cm²), made either in January or in August. After 19–21 years, each wound was assessed for occlusion rate and the presence of decay. All 1- to 2-cm-wide wounds were occluded, compared to 58–70% of the 3- to 4-cm-wide wounds, 25% of the 5-cm-wide wounds, and 0% of the 15-cm-wide wounds. On average, it took 3.6, 5.5, 10.4, 12.7 and 14.7 years to occlude wounds ranging in size from 1- to 5-cm-wide, respectively. After 21 years, the observed size of wounds comprising an initial area of 300 cm² ranged between 14 and 481 cm². Wounding season and stem DBH had no impact on wound healing. Wound decay incidence correlated positively with the initial width of injury (r = 0.925; P < 0.05). All 1- to 2-cm-wide wounds lacked any decay, while the proportions of decay among 3-, 4-, 5- and 15-cm-wide wounds were 58.3, 50.0, 83.3 and 100%, respectively. Length of decay comprised 35–225 cm. Consequently, wounds on P. abies stems greater than 5 cm width are unlikely to be occluded and more prone to decay development.     

Classification of Picea abies Pulpwood According to Wood and Stand Properties

Different classification systems for Norway spruce (Picea abies (L.) Karst.) pulpwood were compared. The classification systems were applied on truckloads or single logs in southern Sweden. Truckload classification according to mean annual growth ring width gave better separation of the wood properties basic density, juvenile wood and dry matter content, than classification according to harvest type (first thinning, later thinning or final felling). The assortments did not have significantly different wood brightness. Sorting at log level according to diameter, mean annual growth ring width or number of annual growth rings, which could be done at harvesting, did not drastically improve differentiation of the mean values of the wood properties or reduce variance compared to truckload classification. The variation in wood properties within assortments remained large owing to the large variation in wood properties between and within logs. Substantial reduction in dry matter variation could be achieved by truckload classification during the summer.     

Microflora of sound-looking wood in Picea abies stems

Ascocoryne spp. (A. cylichnium and A. cf. sarcoides) were found in 48 % of 262 60-year-old Picea abies stems. They were isolated with increasing frequency towards the pith from the lower 2-3 m, more often from thicker than from thinner stems. Neobulgaria premnophila was present in 10 % of the stems, more evenly distributed, and with no difference in occurrence between thicker and thinner stems. Nectria fuckeliana was situated at random in 8 % of the trees.     

Variation in Tree Size and Resistance to Ceratocystis polonica in a Monoclonal Stand of Picea abies

Tree resistance to the pathogenic blue-stain fungus Ceratocystis polonica was studied in a monoclonal stand of Norway spruce [ Picea abies (L.) Karst.] in relation to tree social status and diameter at breast height (DBH). The DBH distribution of the 33-yr-old stand ranged from 5 to 35 cm. There were clear differences in tree height between the suppressed (DBH 7.4-10.3 cm), codominant (DBH 11.8-17.4 cm) and dominant (DBH 18.6-23.9 cm) tree classes. The resistance was tested by mass inoculating trees with a low (400 inoculations m -2 , 60 cm inoculation belt) or high (400 inoculations m -2 , 120 cm inoculation belt) dosage. The small, suppressed trees were more susceptible to inoculation than the codominant and dominant trees, based on the amount of blue-stained and occluded sapwood, lesion length and dead cambium/phloem. A threshold in tree social status or tree size may be important in the overall resistance to fungal infection.     

挪威云杉和柔毛桦引进技术的探讨

该文从引种地区自然条件、引种实施方法两方面对芬兰树种挪威云杉和柔毛桦在鹤北林业局引进技术进行了全面论述。     

Models to predict time since death of Picea abies Snags

Number of years since death was estimated by dendrochronological cross-dating of 107 standing dead trees (snags) of Norway spruce [Picea abies (L.) Karst.] in a submountainous old-growth forest in south–central Norway. Snag characteristics (size, bark cover, branch order present and variables derived from tree-ring analyses) were used in stepwise linear regression procedures to identify variables that explained time since death. Number of branch orders present (where branches growing directly on the stem were branch order 1, branches growing on order 1 branches were order 2, and so on) explained two-thirds of the variation in time since death. Adding other significant variables, such as diameter, relative height of snags, percentage bark cover and average tree-ring width in the final years before death, increased model precision only moderately. The models were validated by the PRESS statistic, which showed that new observations were predicted fairly well with 65–69% of the variation explained.     

Annual Variation in Pollen Contamination and Outcrossing in a Picea abies Seed Orchard

A mature Norway spruce [Picea abies (L.) Karst.] seed orchard, established in southern Finland with 67 clones from northern Finland, was analysed in three different years in order to estimate the pollen contamination ratios. Allozyme-based paternity analysis revealed that the contamination rate was high, 69-71%, and did not differ between the years studied. It appears that, in areas where spruce is the dominant tree species, the contamination rate will be very high even in mature seed orchards. However, the contamination rate in the thinned parts of the orchard was significantly lower than that in the unthinned parts in two of the three years studied. The outcrossing rate was also high, 96-100% in all years, even though the ramets of each clone were planted using a clonal-row design, and there were no significant differences in the outcrossing rates between the different parts of the orchard.     

Susceptibility to Heterobasidion parviporum in Picea abies clones grown in different environments

Thirty-five Norway spruce, Picea abies, clones from Sweden were tested for resistance to Heterobasidion parviporum. Rooted cuttings of the clones were planted in Italy and Greece and cultivated for two growing seasons before inoculation with H. parviporum. Extent of infection was determined 6 weeks later. The results were compared to those of earlier inoculations in Sweden. Plant growth traits were under strong genetic control in all locations with broad sense heritability estimates between 0.14 and 0.54. Lesion and fungal extension heritabilities were moderate, H² ranged from 0.09 to 0.20, and exhibited rather large genetic variation. There was significant genotypic correlation between Italy and Greece with respect to both lesions and fungal extension. No such correlations were found between Sweden and the two other countries. The lack of repeatability in testing susceptibility is unsatisfactory. It could be explained by C-effects associated with propagation of the host plants. Height growth correlated significantly and positively among all countries.     

挪威云杉种源及家系苗期生长适应性的聚类分析

通过对引进的挪威云杉种源和窄冠垂枝型挪威云杉家系进行不同地点苗期试验,选取生长期、当年高和存活率等3个指标进行苗期生长适应性评价,研究结果表明,部分窄冠垂枝型挪威云杉家系具有良好的生长适应性,大部分存活率相对比较低,挪威云杉种源苗期生长普遍不能适应。     

Yield capacity of planted Picea abies in northern Sweden

Norway spruce (Picea abies (L.) Karst.) is the dominant species in the older forests of central northern Sweden. However, spruce has seldom been planted in the area, partly because existing tools for site classification have indicated a low yield capacity for the species. The aim of this study was to examine the yield capacity of spruce on the basis of existing plantations. In total, 91 operational and experimental plantations in the age interval 27–46 yrs were sampled. Stands were located between 62° and 65° N at altitudes 130–620 m a.s.l. Site index was estimated by height growth and site‐factor equations previously developed from old‐growth stand data. Height developments in the plantations indicate that site index for these stands is on average 4.6 m higher than predicted by site‐factor equations. The differences between the two methods are larger on poor sites than on rich sites. No systematic deviations of top height development from the site index curves could be detected on remeasured sample plots. Existing growth models were applied on measured stand data to predict future growth. Calculated mean annual increments were on average 20% lower when site index was predicted by site factors instead of height and age. The bias means that the yield capacity of planted spruce in northern Sweden has been underestimated by about 35%.     

Pathogenicity of ophiostomatoid fungi on Picea abies in Slovenia

Pathogenic fungi can survive and develop in living plants, often causing diseases in the host. Some theories speculate that pathogenic ophiostomatoid fungi provide benefits to its vectors – bark beetles – by overcoming the tree's defence mechanisms. This study reports the results of an experiment in south‐eastern Europe in which mature and seedling Norway spruce trees were artificially inoculated with various ophiostomatoid fungi. The aim of the experiment was to determine the relative virulence of ophiostomatoid fungi by assessing the ability of the fungi to stimulate host tree defence mechanisms through inoculation experiments. Experiments were performed by inoculation of Picea abies in seedling and mature trees. The following fungi were used in low‐density and seedling inoculations: Ophiostoma ainoae, O. brunneo‐ciliatum, Grosmannia cucullata and an unidentified Leptographium sp., O. bicolor, O. fuscum, O. piceae, G. penicillata and G. piceiperda. Endoconidiophora polonica was used in mass and seedling inoculations. Various characteristics such as host vitality, blue stain, lesion and resin outflow were measured before and after the trees were felled. E. polonica caused blue stain, induced large lesions and killed some of the mature trees and seedlings, confirming earlier reports that it is a strong wound pathogen. Only E. polonica, Leptographium sp. and O. ainoae caused blue stains in the sapwood of inoculated seedlings. In low‐density inoculations, G. piceiperda induced intense necrosis and had higher values for all the characteristics monitored. Some of the other ophiostomatoid fungi showed a moderate level of pathogenicity. Fungi with the capacity to stimulate a host defence mechanism could play a role in the establishment of bark beetle populations.