Fungi dangerous at Pinus contorta with special reference to pathogens from North Europe

Examples are given of North American fungi potentially dangerous to Pinus contorta plantations in northern Europe. The pathogenicity of North European fungi is discussed. P. contorta was found to be immune or nearly immune to all European rust fungi, more resistant than P. sylvestris to Phacidium infestans and Lophodermium pinastri, but less resistant to Crumenulopsis sororia and Discella strobilina. For other fungi no such clearcut conclusions could be drawn.     

Variation in pitch canker resistance among provenances of <Emphasis Type="Italic">Pinus patula</Emphasis> and <Emphasis Type="Italic">Pinus tecunumanii</Emphasis> from Mexico and Central America

Pinus patula and high-elevation (HE) sources of P. tecunumanii exhibit intermediate levels of resistance to pitch canker (Fusarium circinatum), compared to extremely resistant species such as P. oocarpa, and extremely susceptible species such as P. radiata. Seedlings from 20 P. patula provenances and 15 HE P. tecunumanii provenances were artificially inoculated with the pitch canker fungus at 21 and 12 weeks of age, respectively, and assessed for resistance 12–20 weeks later. There was important provenance variation in pitch canker resistance for both species. The 20-week LiveStem percentage ranged from 70.3% to 43.6% among the P. patula provenances and 59.6% to 11.7% among HE P. tecunumanii provenances. There was a geographic pattern to the provenance variation, and in both species, low altitude sources demonstrated more resistance than those from high elevation. Provenance variation in pitch canker resistance could be useful when making selection and breeding decisions with these species.     

Pathogens observed on lodgepole pine grown in Finland

Literature on pathogens observed on lodgepole pine (Pinus contorta var. latifolia S. Wats.) grown in Finland is briefly reviewed. Heterobasidion annosum (Fr.) Bref. and Scleroderris lagerbergii Gremmen appear to cause the most serious damage. Lachnellula subtilissima (Cke.) Dennis, Crumenulopsis sororia (Karst.) Groves and Sclerophoma pityophila (Corda) v. Höhn. cause damage less frequently. The majority of over 300 stands have reached an age of 40–60 years and their health is described as satisfactory to good.     

Susceptibility of different provenances of Pinus sylvestris,Pinus Contorta and Picea abies to Gremmeniella abietina

In a randomized block factorial experiment, 1200 seedlings from four provenances, each of Pinus sylvestris, Pinus contorta and Picea abies were inoculated with conidia (2 × 10⁴ and 1 × 10⁶ conidia/seedling) of Gremmeniella abietina (Brunchorstia pinea), isolated from P. contorta plantations in northern Sweden. A further 600 seedlings were left as controls. The occurrence of symptoms and the extension of dead tissues on the annual shoots were recorded 13 months after inoculation. Only the higher spore dose resulted in significant infection. P. sylvestris and P. contorta seedlings were equally susceptible (53% infected), and significantly more infected than P. abies seedlings (39%). The annual shoots of P. sylvestris and P. abies were affected to 43% and 37% of their length, which was significantly more than 15% of the length of P. Contorta shoots. The frequency of affected seedlings differed between the most southern and northern provenances of P. sylvestris and P. abies, and between the northwestern and the south-eastern provenance of P. contorta Twenty-six months after inoculation, a higher proportion of P. contorta seedlings than P. sylvestris and P. abies seedlings had recovered, and a lower proportion of P. contorta than P. sylvestris and P. abies seedlings had died. This paper discusses why P. sylvestris was found to be more susceptible to G. abietina than P. contorta in this experiment, while the reverse is found in plantations in northern Sweden.     

Gremmeniella abietina,Phacidium infestans,and other causes of damage in alpine,young pine plantations in Norway

Field studies of damage and mortality were carried out through 16 years in six young plantations, mostly of Pinus contorta, but also P. sylvestris and P. sibirica. Differences between pine species, P. contorta provenances, sites, and soil treatments are reported and discussed, as are influences of environment, climatic conditions, snow cover, and nutrient deficiency. Gremmeniella abietina was by far the most important cause of mortality; there were great differences between the sites as to development and seriousness. Other important causes of mortality and damage were Phacidium infestans, elk (Alces alces L.), voles, and snow pressure.     

Growth rate and shoot: Root allometry in Pseudotsuga menziesii (Mirb.) Franco and Pinus contorta Dougl. Seedlings raised under two photoperiodic regimes

Six provenances of both Pseudotsuga menziesii (Mirb.) Franco and Pinus contorta Dougl. from a range of locations in the interior of British Columbia between latitudes 49° and 58° were grown for 80 days in controlled environment chambers programmed to provide daylengths comparable with those at either latitude 48°, or latitude 58°, during the period from mid‐June to early September. Neither shoot : root ratio nor whole plant dry weight of P. menziesii were affected by photoperiod. However, P. contorta seedlings, which unlike P. menziesii set bud during the experiment, had a greater dry weight and a higher shoot:root ratio (p<0.05) under longer daylengths. The results appear relevant to the interpretation of effects of cross‐latitudinal provenance transfer on plantation productivity.     

Disease incidence in Eucalyptus microtheca provenances

A provenance trial of Eucalyptus microtheca F. Muell. was studied in order to select resistant provenances against Cytospara eucalypti twig blight, Pestalotiopsis versicolor stem canker and Botryodiplodia theobromae root collar canker. Out of 21 provenances tried, 4 provenances were screened as resistant against diseases and showed best performance.     

Seedling shoot,needle and bud development in three provenances of Pinus sylvestris and Pinus contorta cultivated in northern Sweden

The patterns of current‐year shoot, needle and terminal bud elongation in seedlings of three Scots pine (Pinus sylvestris L.) and three lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) provenances were compared during the third and fourth growing seasons after planting. Lodgepole pine produced longer shoots and buds than did Scots pine, mainly because lodgepole pine formed more stem units and elongated at a faster rate. Stem unit length and the duration of shoot and bud elongation differed relatively little between species and provenances. Lammas or polycyclic growth occurred in some lodgepole pine provenances, but not in any Scots pine provenance, and was associated with enhanced shoot elongation. Needle elongation commenced earlier, proceeded at a faster rate, and was greater in lodgepole pine than in Scots pine, but ceased about the same time in all species and provenances. The heat sum required to attain 50% of final length was lower for shoots and needles in lodgepole pine than in Scots pine, and for shoots in northern provenances than in southern ones. Mitotic activity in the apical meristem of the terminal bud, which occurred less than one week after the seedlings were free from snow, started and ceased about the same time in each species, but was higher in lodgepole pine than in Scots pine early in the shoot elongation period.     

Site index variation with latitude and altitude in IUFRO Pinus contorta provenance experiments in western Canada and northern Sweden

Site index was calculated for 66 experimental plantations in western Canada and northern Sweden, containing a wide range of Pinus contorta provenances drawn from seed lots belonging to the IUFRO international provenance testing program. Growth data from recommended provenances were used to calculate the site index. Site index was defined as predicted average height of the 100 largest trees by diameter ha^‐1 at age 50.

Latitude and altitude explained 56% of site index variation by fitting the function:

Site Index (m) = 99.8 ‐ 1.226 ? Latitude (°N) ‐ 0.01205 ? Altitude (m).

The site index pattern indicated that forest productivity of the sites investigated decreased approximately by 0.8 m³ ha^‐1 yr^‐1 per one‐degree latitude northwards and per 100 m increase in altitude.     

Volume growth and wood density of plus tree progenies of Pinus contorta in two Swedish field trials

Seventy‐four half‐sib families of lodgepole pine (Pinus contorta ssp. latifolia Engelm.) plus trees were measured for vigour, height growth, stem diameter, wood density and ring width in two Swedish field trials at age 9. Height growth, wood density and ring width differed between families within provenances with variance components of 3–8 %. Coefficients of variation were highest for height growth and lowest for ring width. Heritabilities were similar for height growth and wood density but lower for ring width. These genetic parameters seemed to be equal for all provenances. Indirect selection for high dry stem biomass was more effective using height growth than wood density, and a correlated response in wood density of 2.1 % of mean by selecting the 15 highest parent trees was indicated. Juvenile wood density looks uncertain as a selection criterion for mature wood density.     

Differences between provenances of pinus contort a var. latifolia in resistance to attack by gremmeniella abietina

A provenance trial of lodgepole pine (Pinus contorta var. latifolia) planted in 1969 at Matrand, Eidskog, Norway was apparently attacked by Gremmeniella abietina in 1984/85. In late autumn the damage was recorded separately on the lower and upper halves of the trees. The material ranged in latitude from 40.25°N to 56.28°N, and in altitude from 2 850 to 450 m a.s.l., highest in interior western United States and lowest in western Canada. The most heavily attacked sources were those from southern latitudes and from high elevations. The attack frequency changed gradually from south to north. In order to avoid attack by G. abietina, only well‐adapted provenances should be used.     

Comparison of Gremmeniella abietina isolates from Pinus sylvestris and Pinus contorta in terms of conidial morphology and host colonization

Gremmeniella abietina isolates from Pinus contorta in northern Sweden produced, in vitro, shorter conidia with fewer septa compared with isolates from Pinus sylvestris in the southern part of the country. After mycelial inoculation of shoots with G. abietina isolates from both host species, the resulting necroses were longer in P. sylvestris than in P. contorta. Keeping seedlings in artificial mild winter climate or detaching shoots from the seedling before inoculation caused longer necroses. No host specificity in colonization was found. Isolates from P. sylvestris caused longer necroses than did isolates from P. contorta, and both types of isolates caused longer necroses in P. sylvestris than in P. contorta. The differences found between the two G. abietina populations probably reflect regional variation in the fungus.     

Tree and stand structure of the non-native Pinus contorta in relation to native Pinus sylvestris and Picea abies in young managed forests in boreal Sweden

Managed forest stands are typically younger and structurally less diverse than natural forests. Introduction of non-native tree species might increase the structural changes to managed forest stands, but detailed analyses of tree- and stand-structures of native and non-native managed forests are often lacking. Improved knowledge of non-native forest structure could help clarify their multiple values (e.g. habitat for native biodiversity, bioenergy opportunities). We studied the structural differences between the introduced, non-native Pinus contorta and the native Pinus sylvestris and Picea abies over young forest stand ages (13–34 years old) in managed forests in northern Sweden. We found that P. contorta stands had greater mean basal areas, tree heights, diameters at breast height, and surface area of living branches than the two native species in young stands. The surface area of dead attached branches was also greater in P. contorta than P. abies. Although this indicates greater habitat availability for branch-living organisms, it also contributes to the overall more shaded conditions in stands of P. contorta. Only one older 87 years old P. contorta stand was available, and future studies will tell how structural differences between P. contorta and native tree species develop over the full forestry cycle.     

Endothia gyrosa associated with severe stem cankers on plantation grown Eucalyptus nitens in Tasmania,Australia

Severe stem cankers in Eucalyptus nitens, from a 14-year-old mixed provenance plantation, were associated with infection by Endothia gyrosa, present in its teleomorph state. Surveys of incidence among canker severity classes were carried out in a thinned and pruned stand and an adjacent unthinned and unpruned stand within the affected plantation. No differences in incidence among the canker severity classes were found between the thinned/pruned and unthinned/unpruned stands or between different crown dominance classes within the unthinned/unpruned stand. However, the incidence among canker severity classes was strongly associated with bark roughness with 97% of rough-barked trees developing either annual cankers or cankers causing cambial damage. Stem cankers were found on only 11% of trees with smooth bark. Bark roughness in E. nitens was shown to differ significantly between provenances. Deployment of provenances prone to rough bark in routine plantation establishment may pose a risk of damaging stem canker outbreaks.     

Resistance of Pinus contorta to the European race of Gremmeniella abietina

Pinus contorta seedlings, together with Pinus resinosa and Pinus banksiana seedlings, were planted adjacent to 25‐year‐old red pine trees infected by the European (EU) race of Gremmeniella abietina. Resistance to this race was assessed over 5 years. All P. resinosa seedlings were dead after that period while 65% of P. contorta and 86% of P. banksiana seedlings appeared resistant to the disease. The tip blight that occurred on P. contorta was slightly longer than that observed on P. banksiana. In microscopy, one, two, or even more suberized boundaries were seen to be initiated near the surface of the shoot at the base of healthy needles where they extended downward in the direction of the vascular cambium. Suberized boundaries occasionally crossed the xylem and joined together in the pith region to form continuous barriers around necrotic tissues. However, in most cases, these suberized barriers were not continuous across the shoot and compartmentalization was then completed by other barriers mainly constituted of parenchyma cells and xylem tracheids that accumulated phenolic compounds. Meristematic‐like cells were observed adjacent to the necrophylactic periderm. Tissue regeneration, restoration of cambial activities and formation of traumatic resin canals also seemed to be associated with the defence system of P. contorta against the EU race of G. abietina.     

Formation and growth of stem cankers caused by Gremmeniella abietina on young Pinus contorta

From 1990 to 1995, the formation and growth of stem cankers caused by Gremmeniella abietina on Pinus contorta var. latifolia was studied in three stands in northern Sweden. The stands were planted in 1976–80. The total number of cankers on 756 trees that were individually followed increased from 233 to 477 during the 5‐year period. With 42.0% of the cankers, the pathogen entered through or from the base of diseased branches, and 33.6% through visually undamaged bark. Most of the cankers were within 100 cm of the ground. In one of the three areas, the cankers were evenly distributed within 180 cm of the ground. The frequency of cankers facing north exceeded those facing south. The average vertical length of cankers had increased, 55.6% of cankers had increased their percentage coverage of the stem girth; 13.8% had fully girdled the stem. At two of the sites, there was a negative correlation between canker coverage of the stem circumference and tree height increment.     

Incidence and importance of Crumenula sororia on Lodgepole pine

In stands of Lodgepole pine over 6 years old, 68% of stems in Climatic Zones A and B, characterised by a relatively short growing season, and 63 % of stems in Climatic Zone C were infected by Crumenula sororia. On individual trees, the number of stem whorls showing C. sororia infection increased significantly with increasing stand elevation and with decreasing exposure in crops on Alberta and Shuswap Lake provenances over 30 years old, whereas in Shuswap, Long Beach and Vancouver Island stands less than 30 years old, increasing elevation and decreasing exposure had little effect on numbers of infected whorls. The numbers of infected whorls were not related to compartment aspect in crops of Alberta provenance, whereas in stands of Shuswap Lake, Long Beach and Vancouver Island provenances, W, SW and S-facing compartments showed fewer infections. In contrast the numbers of active cankers showed a positive correlation with increasing compartment elevation and exposure. In Zones B and C, cankers were concentrated on Northerly and Westerly aspects of individual stems. The evidence suggests that particular climatic regimes in different zones of the tree and in different ages of crop may be critical in determining the success of failure of infection by C. sororia.     

Histological and histochemical detection of defence responses in pine embryos challenged in vitro with Heterobasidion annosum

Embryos of Pinus sylvestris, Pinus nigra var. maritima and Pinus contorta were inoculated in vitro with Heterobasidion annosum and the histology and histochemistry of the host response determined. Three days after challenge, intercellular penetration of hyphae through the epidermis and into the cortex of the host species had occurred. In cells close to the invading hyphae, cell walls became thickened in all three pine species. Lignification and suberization of cell walls in the cortex was detectable in P. nigra var. maritima and P. contorta, but not in P. sylvestris. Moreover, cells in the cortex of P. nigra var. maritima and P. contorta became occluded with dense deposits staining positively for phenolic and lipidic materials. Starch grains had accumulated in host cells close to sites of penetration by day 3, and levels appeared to increase by day 6, except for tissues where heavy invasion by H. annosum had occurred. Host responses intensified between 3 and 6 days after challenge. By day 6, however, the pathogen had penetrated as far as the stele and into the developing xylem vessels. Nine days after challenge, host tissues contained abundant intra- and inter-cellular hyphae, causing severe disruption and disintegration of all tissues. The utility of such in vitro systems in studies on the resistance responses of conifers to challenge with fungal pathogens is discussed.     

Variation in susceptibility of six pine species and hybrids to pitch canker caused by Fusarium circinatum

Six pine species or hybrids were tested for susceptibility to pitch canker caused by Fusarium  circinatum. Pinus  densiflora, Pinus  thunbergii, Pinus  x rigitaeda (Pinus  rigida × Pinus  taeda), P. rigida × P. x rigitaeda, Pinus  echinata and Pinus  virginiana were inoculated with three spore loads (50, 500 and 5000 per tree) of F. circinatum. External symptoms, lesion length, and the frequency of reisolation of the fungus were investigated. External symptoms were greatest in P. echinata, followed by P. virginiana, however, P. densiflora was not susceptible to F. circinatum. Based on mean lesion lengths, the six pine species or hybrids differed significantly (p < 0.01) in susceptibility to pitch canker. Pinus  echinata sustained the longest lesions, whereas P. densiflora sustained the shortest lesions. The effect of inoculum density was not significant among three spore treatments within species (p = 0.17), although lesion length was slightly greater at higher spore loads over all pine species. The fungus was reisolated from inoculated stems of all pine species tested, even on trees showing little or no damage from the disease. Additional studies are needed to further explore the basis for resistance to pitch canker.     

Über das Auftreten von Leucocytospora kunzei bei Pinus griffithii in Parkanlagen der Stadt Basel

Occurrence of Leucocytospora kunzei on Pinus griffithii in parks of the City of Basel. Leucocytospora kunzeii (Sacc.) Urban, the causal agent of a canker disease mainly known in North America, was found on Pinus griffitbii in several public parks of Basel.