Signs and symptoms associated with Heterobasidion annosum and Armillaria ostoyae infection in dead and dying mountain pine (Pinus mugo ssp. uncinata)

Symptoms and signs associated with root rot caused by Heterobasidion annosum or Armillaria ostoyae in mountain pines (Pinus mugo ssp. uncinata) were investigated in the Swiss Alps. A sample of dying or recently dead mountain pine trees (≥12 cm d.b.h.) and saplings (<1.3 m height) was assessed for root pathogen infection by taking root samples followed by isolations in the laboratory. From a subsample, an additional core was taken from the butt of each tree and evaluated in the same fashion. A total of 157 dying or recently dead mountain pine trees and 184 saplings with roots infected by either of the two pathogens or which lacked infection were analyzed using logistic regression models. The main objectives were to determine the most prominent symptoms induced by the fungi (resinosis), signs of the fungi (mycelia, fruiting bodies and rhizomorphs), and tree characteristics (d.b.h./height and evidence of wounds) that would allow an easy and reliable determination of H. annosum and/or A. ostoyae infection of mountain pines in the field. Heterobasidion annosum caused both root and butt rot on mountain pine, whereas A. ostoyae was mostly restricted to the root systems of the trees sampled. The most discriminating sign for the presence of A. ostoyae infection was the presence of characteristic mycelial fans, and for H. annosum root rot the presence of H. annosum mycelia (sheets of paper‐thin mycelium and mycelial pustules). In addition, resinosis was a powerful predictor for A. ostoyae in trees. Symptoms and signs indicating A. ostoyae or H. annosum infections were more reliable for saplings than for mature trees. Armillaria rhizomorphs were not useful in detecting A. ostoyae infection and, if present, were often formed by saprophytic Armillaria species. Heterobasidion annosum fruiting bodies were rarely observed and poorly reflected the widespread occurrence of this pathogen in the mountain pine forests.     

Growth of axenic cultures of Cronartium flaccidum on callus tissue from Pinus nigra var. laricio and Pinus sylvestris

The callus-fungal method was employed to test the response to C. flaccidum of the highly susceptible P. nigra var. laricio and the resistant P. sylvestris, and to ascertain whether results obtained with this method matched in planta observations. Calli were inoculated with axenie cultures of C. flaccidum obtained by incubating basidiospores on modified Schenk and Hildebrandt medium. Several parameters were evaluated. Colony growth was more rapid on P. nigra var. laricio. Colonies were dense on P. nigra var. laricio, but sparse on P. sylvestris. Aerial hyphae growth was abundant on P. nigra var. laricio, but less frequent on P. sylvestris. Hyphal branching began after 18 h on P. nigra var. laricio and after 45 h on P. sylvestris. Necrosis of the host cells set in after 24 h on P. nigra var. laricio, and after 70 h on P. sylvestris. The number of cells with plasmolysis was much larger in P. nigra var. laricio than in P. sylvestris. These results were consistent with the known resistance of the two species on whole plants.     

Systemic effects of Heterobasidion annosum s.s. infection on severity of Diplodia pinea tip blight and terpenoid metabolism in Italian stone pine (Pinus pinea)

Three-year-old seedlings of Pinus pinea L. were inoculated near the stem base with one of two Heterobasidion annosum (Fr.) Bref. sensu stricto (s.s.) strains belonging to two populations: the North American P-group (NAm-P) and the European P-group (Eur-P). The NAm-P strain caused smaller H. annosum stem lesions than the Eur-P strain. Three weeks after the stem inoculations with H. annosum, apical shoots were inoculated with Diplodia pinea (Desmaz.) J. Kick. Basal stem infection with H. annosum resulted in D. pinea causing longer necrotic lesions in the shoots, indicating systemic induced susceptibility (SIS) to this shoot blight pathogen. Furthermore, stem induction with the NAm-P strain resulted in higher susceptibility to D. pinea than stem induction with the Eur-P strain. Total terpene accumulation was suppressed by about 50% in the shoots under attack by D. pinea when seedlings were induced with H. annosum. Total terpene concentration in shoots inoculated with D. pinea was negatively correlated with lesion size, both overall and by stem treatment. Stem base inoculation with H. annosum induced whole-plant changes in ter-pe-noid profiles, but these were not associated with the SIS phenotype. We discuss our findings on modulation of systemic response of P. pinea to fungal attack in the context of tripartite ecological interactions.     

Dieback Disease of Pines with Special Reference to Corsican Pine Pinus nigra var. Calabrica Schn.: II. The Relationship between Frost Resistance, Microclimate, and.Disease

The winter frost hardiness level of Corsican Pine buds in northernEngland is found to range from –16° C to –20C (+3° F to –4° F). Buds in the lower parts ofthe tree are more susceptible to frost damage than those nearerthe leader, and buds at a given position in the canopy on anorth-facing slope are less hardy than those in a correspondingposition on a tree in a south aspect. The symptoms produced by artificial freezing are distinct fromthose found in dieback disease, and temperature measurementsin diseased and healthy stands suggest that frosts are not severeenough to account for the disease. The lower hardiness levelsin disease susceptible areas are therefore considered to beof secondary importance and are probably a result of a weakenedphysiological condition in the tree. Diseased slopes are chiefly characterized by high humidities,low light intensities, and only slightly reduced air and soiltemperatures when compared with nearby healthy areas.     

Relationships between climate and radial growth in black pine (Pinus nigra Arnold ssp. salzmannii (Dunal) Franco) from the south of France

? Context

The Salzmann pine (Pinus nigra ssp. salzmannii) is an endemic subspecies of black pine native to the Western Mediterranean basin. In Spain, Salzmann pine covers extensive areas (approx. 350 000?ha), while in France where few scattered populations subsist, its distribution area is estimated at approx. 3 000?ha.

? Method

We used a dendroecological approach to understand the impact of climate fluctuations on Salzmann pine from France. Spatial and temporal variability of radial growth response was compared in three ecologically different populations (Conflent, Gorges du Tarn, Saint-Guilhem-le-D??sert).

? Results

The Conflent population showed a strong sensitivity to spring precipitation deficits (March to June), while at Gorges du Tarn and Saint-Guilhem sites, autumn (October) of the previous year and winter (February) temperatures explained more variance than precipitations and were, respectively, negatively and positively correlated to radial growth.

? Conclusion

Although covering a limited distribution range in France, Salzmann pine demonstrated large differences in radial growth response to climate and soil variations.     

Real‐time PCR assays for the detection of Heterobasidion irregulare,H. occidentale,H. annosum sensu stricto and the Heterobasidion annosum complex

A set of quantitative hierarchical real‐time PCR assays was developed for the detection of Heterobasidion irregulare, H. occidentale, H. annosum sensu stricto and of the entire Heterobasidion annosum complex. These assays enable specific and accurate detection and quantification of the target species from DNA extracted on airborne collected spores. Heterobasidion‐specific TaqMan? real‐time PCR detection assays were designed to function under homogeneous conditions so that they may be used in 96‐ or 384‐well plate format arrays for high‐throughput testing of large numbers of samples against multiple targets. Assays were validated for (i) specificity, (ii) sensitivity and (iii) repeatability. All assays were highly specific when evaluated against a panel of pure cultures of target and phylogenetically closely related species. Sensitivity, evaluated by assessing the limit of detection (with a threshold of 95% of positive samples), was found to be between one and a hundred ITS gene region copies or one conidia count equivalent. Precision or repeatability of each assay revealed a mean coefficient of variation of 5.9%. These molecular tools are now available for rapid and reliable monitoring of one of the most significant pathogen species complex of temperate northern coniferous forest around the world.     

Relationship between vigour and susceptibility of Austrian pine (Pinus nigra) to blister rust (Cronartium flaccidum)

In a 13-year-old plantation of Austrian pine no apparent relationship between vegetative vigour expressed as height and as stem circumference, and susceptibility to blister rust due to Cronartium flaccidum was found. Under conditions which favour the development of the disease, it is possible to select vigorous and blister rust resistant Austrian pines.     

Evaluation of the biological control agent Rotstop in controlling the infection of spruce and pine stumps by Heterobasidion in Latvia

The biological control agent Rotstop^® composed of a suspension of spores of Phlebiopsis gigantea (Fr.) Jül. is widely used for protecting conifer stumps from aerial infection by Heterobasidion species. The efficacy of Rotstop application on Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) stumps was determined in several locations and at different seasons in Latvia. Mean efficacy in controlling natural infection by Heterobasidion spp. in spruce stumps was 64%, calculated on the basis of number of infected stumps, and 89%, calculated on the basis of area of infected wood on sample discs cut from the stumps. Corresponding proportions for pine were 82% and 95%. The results show that Rotstop can be successfully used for stump treatment in Latvia, although improved efficacy is desirable, particularly in spruce. A Latvian isolate of P. gigantea, selected from numerous isolates in preliminary tests, was included in one experiment and was shown to be as effective as the Rotstop isolate. In untreated spruce stumps Heterobasidion spp. and P. gigantea were present in the same stump three times more frequently than in untreated pine stumps. Heterobasidion spp. infection in untreated spruce stumps was low when P. gigantea covered more than 10% of stump dissection.     

异担子菌及其病害防治的研究现状

北半球针叶林最严重的森林病害是由广义的多年异担子菌(Heterobasidion annosum sensu lato)引起的干基白色腐朽病,但近年的研究表明多年异担子菌并不是单一的物种,目前在欧洲已分出3个独立的种,即原始多年异担子菌(Heterobasidion annosum sensu stricto)、小孔异担子菌(Heterobasidion parviporum)和冷杉异担子菌(Heterobasidi-on abietinum),它们生物学习性、形态结构,生态学,寄主范围和发生区域均有差异。应用大伏革菌Phlebiopsisgigantea对该类病害进行生物防治是较好的方法。将中国东北和西南(云南)的异担子菌单孢菌株与欧洲的三种异担子菌进行交配,结果表明中国东北和西南地区的异担子菌与原始多年异担子菌无性亲和反应,而与小孔异担子菌有性融合反应,因此中国东北和西南地区的异担子菌是小孔异担子菌,目前中国并不存在原始多年异担子菌。由于原始多年异担子菌和冷杉异担子菌均为严重的森林病原菌,应将其作为对外检疫对象。     

奥地利黑松苗木根系与地上部分生长关系研究

对引进树种奥地利黑松1年生容器苗根系与地上部分生长关系进行了调查研究。结果表明,奥地利黑松苗高和地径生长量与根系生物量极显著相关。苗高生长量与侧根鲜重关系最密切,地径生长量受根系鲜重影响最大。应用逐步回归法建立了苗高、地径生长量与根系生长关系的最优回归方程。     

Modelling the diameter distribution of Pinus sylvestris, Pinus nigra and Pinus halepensis forest stands in Catalonia using the truncated Weibull function

Parameter prediction models for the diameter distribution ofPinus sylvestris L., Pinus nigra Arn. and Pinus halepensis Mill.in Catalonia were developed using the truncated Weibull functionas the theoretical distribution. The parameter models allowone to use individual-tree models in the simulation of standdevelopment when only stand-level data are collected in forestinventories. Parameter models for the diameter distributionof stand basal area were developed. The data consisted of permanentsample plots from the Spanish National Forest Inventory in Catalonia.A total of 1780 empirical distributions of P. sylvestris, 1204distributions of P. nigra and 1535 distributions of P. halepensiswere used as modelling data. The empirical data represent left-truncateddistributions, as the smallest diameter measured in the fieldwas 7.5 cm. Two different approaches, namely, regression (two-stepmethod) and optimization approach (one-step method), were usedto find the coefficients of the parameter models. In the two-stepmodelling method, the Weibull parameters were first estimatedseparately for every empirical distribution by maximizing thelog-likelihood function of the Weibull density function. Inthe second-step, regression analysis was used to find the relationshipbetween Weibull parameters and stand basal area, number of treesper hectare and elevation of the site. The one-step method usedoptimization to find such coefficients for the parameter models,which minimized the mean of the squared differences betweenempirical and predicted cumulative tree frequencies in the wholemodelling data. The one-step optimization method performed betterthan the two-step regression method for all tree species. Theparameter prediction models developed in this study enable theprediction of the diameter distribution of P. sylvestris, P.nigra and P. halepensis in Catalonia from limited stand information.     

Investigations on Heterobasidion annosum s.lat. in central and eastern Asia with the aid of mating tests and DNA fingerprinting

To investigate the taxonomy of Heterobasidion in Eurasia, 49 specimens belonging to H. annosum sensu lato from Asia were identified with the aid of mating tests. Most of the specimens originated from north‐eastern and south‐western China and from the Altai region in southern Siberia, but a few isolates from Kirghizia, Japan and India were also tested. In addition to mating tests, the material from China was investigated with DNA fingerprinting. Heterobasidion annosum sensu stricto was identified only from the Altai region. Homokaryotic isolates from other specimens, except the Indian ones, were sexually compatible with H. parviporum, but they also showed a high degree of compatibility with H. abietinum and with the North American S group. The isolates from SW China (eastern Himalayas) mated with about equal frequency with the European strains of H. parviporum and H. abietinum. However, the DNA fingerprinting showed that these isolates were more closely related to H. parviporum, and hence they were tentatively included in this species. The North American S group was more distant from these Eurasian taxa. Four old isolates from India mated only weakly with the members of the H. annosum s.lat. According to the species concept presented, the distribution of H. parviporum extends from western Europe through southern Siberia to northern China, Japan and the eastern Himalayas. H. annosum s.str. is so far identified only from the Altai region outside Europe, and H. abietinum only from Europe.     

Influence of moisture stress and induced resistance in ponderosa pine,Pinus ponderosa Dougl. ex. Laws,on the pine sawfly,Neodiprion autumnalis Smith

Plant moisture stress is artificially maintained for ponderosa pine, Pinus ponderosa Dougl. ex Laws, seedlings using polyethylene glycol. Stressed seedlings produce significantly lower amounts of needle nitrogen, phenols, and tannins than non-stressed seedlings. Field tests reveal that previously damaged foliage is a significantly poorer food source for the pine sawfly, Neodiprion autumnalis Smith (Hymenoptera: Diprionidae), than non-damaged foliage. Field studies further indicate that the effect of induction by defoliation is more important than the effect of stress level. These results are discussed in terms of their potential impact on future studies on preferential selection by herbivores of stressed host plants.     

Differential effects of nutrient availability on the secondary metabolism of Austrian pine (Pinus nigra) phloem and resistance to Diplodia pinea

Nutrient availability can modulate the incidence and severity of plant diseases. We examined the effects of fertility on (i) host resistance and (ii) secondary metabolite production in the Pinus nigra Arnold –Diplodia pinea (Desm.) Kickx pathosystem. Following preconditioning of trees to one of three fertility levels for one growing season, phloem tissue of one branch was harvested for chemical analyses while another branch on the same whorl was inoculated with the fungus to assess resistance. Nutrient availability had concave and convex quadratic effects on concentrations of total monoterpenes and total phenolics respectively, but had no effect on fungal lesion lengths. Lesion lengths were negatively correlated with lignin, suggesting that this compound is an important factor in resistance. Counteracting effects of nutrient availability on phenolic and terpenoid pathways may explain why fertility had no effect on expression of disease resistance.     

Interrelationships among light,photosynthesis and nitrogen in the crown of mature Pinus contorta ssp. latifolia

Scaling leaf-level measurements to estimate carbon gain of entire leaf crowns or canopies requires an understanding of the distribution of photosynthetic capacity and corresponding light microenvironments within a crown. We have compared changes in the photosynthetic light response and nitrogen (N) content (per unit leaf area) of Pinus contorta Dougl. ssp. latifolia Engelm. (lodgepole pine) leaves in relation to their age and light microenvironment. The vertical gradient in integrated daily photosynthetic photon flux density (PPFD) from the upper to the lower crown of lodgepole pine was similar in magnitude to the horizontal gradient in daily PPFD along shoots from young to old leaves. The relationship between light-saturated net photosynthesis (A(max)) and daily PPFD was significant for both young and old leaves. However, old leaves had a lower A(max) than young leaves in a similar daily irradiance regime. For leaves of all ages from throughout the crown, A(max) was linearly related to the estimated daily net carbon gain that leaves could achieve in their natural PPFD environment (estimated A(day)) (r(2) = 0.84, P < 0.001, n = 39), indicating that estimated A(day) may be dominated by carbon fixed when leaves are light-saturated and operating at A(max). Comparison of the PPFD required to achieve A(max) and the PPFD available to the leaves showed that all of the measured leaves (n = 39), regardless of their position in the crown or age, were in light environments that could light-saturate photosynthesis for a similar proportion of the day. For all data pooled, foliar N was weakly correlated with daily PPFD. Analyzing each leaf age class separately showed that foliar N was significantly related to daily PPFD, A(max), and estimated A(day) for the youngest leaves but not for middle-aged or old leaves. Therefore, the general theory that foliar N is allocated within a crown according to total daily light availability was supported only for young (1-4 years old) leaves in this study.     

桥山林区油松奥地利黑松生长量调查

本文对桥山林区引进奥地利黑松进行生长量对比试验研究分析,奥地利黑松适应桥山林区气候条件,具有生长迅速、生长稳定等特点,可以作为渭北黄土高原今后荒山绿化和营造防护林主要树种之一,也为今后引进新树种提供技术依据.     

Influence of tree size, reduced competition, and climate on the growth response of Pinus nigra Arn. salzmannii after fire

Context

After wildfire, surviving trees are of major ecological importance as they can help in the post-fire regeneration process. Although these trees may be damaged, they may also benefit from reduced fuel hazard and competition. However, little is known about the long-term growth response of surviving trees.

Aims

This study aims to explain short- to long-term variations in the postfire growth of surviving black pines in an area burnt in 1994, focusing on levels of fire severity and tree sizes.

Methods

Relative basal area increments were used to detect time-course variations in postfire radial tree growth depending on fire severity. Linear mixed-effects models were used to describe the factors affecting postfire ring growth.

Results

In the short term, fire caused stronger reduction in growth in small trees with increasing bole char height. However, as time since fire increased, a positive effect of fire on growth due to reduced competition counteracted the short-term fire impacts. Indeed, small surviving trees demonstrated a surge in growth 15 years after the fire.

Conclusion

It was concluded that reduced competition might offset the short-term negative effects of fire in surviving black pines.     

Effects of impregnation and heat treatment on the physical and mechanical properties of Scots pine (Pinus sylvestris) wood

Wood modification, of which thermal modification is one of the best-known methods, offers possible improvement in wood properties without imposing undue strain on the environment. This study investigates improvement of the properties of heat-treated solid wood. Scots pine (Pinus sylvestris) was modified in two stages: impregnation with modifiers followed by heat treatment at different temperatures. The impregnation was done with water glass, melamine, silicone, and tall oil. The heat treatment was performed at the temperatures of 180°C and 212°C for three hours. The modified samples were analyzed using performance indicators and scanning electron microscope micrographs. The mechanical and physical properties were determined with water absorption, swelling, bending strength, and impact strength tests. All the modifiers penetrated better into sapwood than hardwood; however, there were significant differences in the impregnation behavior of the modifiers. As regards the effect of heat treatment, generally the moisture properties were improved and mechanical strengths impaired with increasing treatment temperature. In contrast to previous studies, the bending strength increased after melamine impregnation and mild heat treatment. It is concluded that the properties of impregnated wood can be enhanced by moderate heat treatment.