Pathogenicity testing of four Bursaphelenchus species on conifer seedlings under greenhouse conditions

The pinewood nematode, Bursaphelenchus xylophilus (Steiner and Buhrer, J. Agric Res. 48, 1934, 949), Nickle (J. Nematol. 2, 1970, 375), is the causative agent of the pine wilt disease and causes serious damage to pine forests around the world. During a survey for the pinewood nematode, four other Bursaphelenchus species (Bursaphelenchus mucronatus, B. sexdentati, B. anamurius and B. vallesianus) were isolated from wilted pine trees in Turkey. To understand the effects of these Bursaphelenchus species on wilting of pine trees, a study was conducted under greenhouse conditions. Two‐year‐old seedlings of three pine species (Pinus nigra, P. brutia and P. pinea) and one cedar species (Cedrus libani) were used. Fifteen seedlings of each species were inoculated with nematodes and 10 seedlings of each species served as controls. The inoculum densities used for each seedling contained approximately 1000 (±100) nematodes of all life stages in 0.25 ml of distilled water. The first wilting symptoms were observed in the fifth week in all pine species but not in the cedar seedlings. All seeding mortality occurred between the 5th and 13th weeks of the study; no mortality was observed outside of this period. The most pathogenic nematode species was B. mucronatus, closely followed by the other species. The most susceptible seedling species was P. nigra, and C. libani was the most resistant species.     

Wildlife species associated with non-coniferous vegetation in Pacific Northwest conifer forests: A review

Non-coniferous vegetation, including herbs, shrubs, and broad-leaved trees, makes a vital contribution to ecosystem function and diversity in Pacific Northwest conifer forests. However, forest management has largely been indifferent or detrimental to shrubs and trees that have low commercial value, in spite of a paradigm shift towards more holistic management in recent decades. Forest management practices that are detrimental to broad-leaved trees and shrubs are likely to decrease habitat diversity for wildlife, but the number of species that may be affected has not previously been enumerated. I reviewed life history accounts for forest-dwelling vertebrate wildlife species and derived a list of 78 species in Oregon and Washington that are associated with non-coniferous vegetation. The diversity of direct and indirect food resources provided was the primary functional basis for associations of most species with non-coniferous vegetation. Thus, a diversity of herbs and broad-leaved trees and shrubs provides the foundation for food webs that contribute to diversity at multiple trophic levels in Pacific Northwest conifer forests. Given the number of species associated with non-coniferous vegetation in conifer-dominated forests, maintaining habitats that support diverse plant communities, particularly broad-leaved trees and shrubs, will be an important component of management strategies intended to foster biodiversity. Silvicultural practices such as modified planting densities, and pre-commercial and commercial thinning, can be used to control stand density in order to favor the development of understory herbs, shrubs, and a diversity of tree species within managed stands. Allowing shrubs and hardwood trees to develop and persist in early seral stands by curtailing vegetation control also would benefit many species associated with non-coniferous vegetation.     

Bursaphelenchus tusciae in Tunisia associated with Hylurgus ligniperda

Bursaphelenchus tusciae is reported for the first time in Tunisia and North Africa, associated with the insect Hylurgus ligniperda Fabricius (Coleoptera: Curculionidae: Scolytinae). Nematode identification was based on restriction fragment length polymorphism analysis and sequencing of the internal transcribed spacer (ITS) regions of ribosomal DNA. Phylogenetic analysis revealed that Tunisian B. tusciae clusters together with two other B. tusciae isolates forming a separate group close to B. hildegardae and B. eggersi. As H. ligniperda is among maritime pine scolytids pests in Tunisia and is widely distributed in North Africa, this study is an important contribution to the knowledge of Bursaphelenchus species associated with bark beetles of pine forests in Tunisia and North Africa.     

Suppression of ectomycorrhizal development in young Pinus thunbergii trees inoculated with Bursaphelenchus xylophilus

In order to study the changes in ectomycorrhizal development during symptom expression of pine wilt disease, root window observations were conducted concurrent with measurements of leaf water potential as well as photosynthetic and transpiration rates of 5‐year‐old Pinus thunbergii trees that were inoculated with the pinewood nematode (PWN) Bursaphelenchus xylophilus. Infected trees were compared with girdled and uninfected control trees. Ectomycorrhizas developed constantly during the experimental period in control trees but did not develop in the girdled trees. Ectomycorrhizal development ceased within 2 weeks in those trees that finally died after PWN infection. In the trees that survived PWN infection, ectomycorrhizal development ceased within 1–4 weeks of inoculation but was resumed thereafter within 3–6 weeks. Ectomycorrhizal development ceased prior to a decrease in both photosynthetic rate and leaf water potential in the inoculated trees.     

Scale insects of the conifer trees in Turkey and their zoogeographical distribution

In Turkey, 25 species of Coccoidea (Homoptera) are recorded on Conifera tree species. The family Diaspididae has 15, Coccidae 6, Pseudococcidae 3, and Margarodidae 1 species. Specifically, Dynaspidiotus spp. are recorded on Abies, Cedrus, Picea, and Pinus; Leucaspis spp. on Pinus spp.; Carulaspis spp. on Biota, Cupressus, Juniperus, and Thuja; Lepidosaphes spp. on Abies, Biota, Juniperus, and Picea; Coccus spp. on Abies, Cedrus, and Pinus; and Planococcus spp. on Cupressus, Juniperus, and Pinus species. Acanthomytilus cedricola is recorded only on Cedrus spp.; Physokermes piceae on Abies and Picea species; and Marchalina hellenica only on Pinus species. Two species are Native, five are Cosmopolitan, 15 are Palaearctic, and 3 are of Mediterranean origin.     

Deciduous trees affect small-scale floristic diversity and tree regeneration in conifer forests

Abstract

There is a growing interest in the effects of deciduous trees on biodiversity, soil processes and long-term productivity in boreal, conifer-dominated forests. This study investigated whether individual birch trees allowed to grow to maturity in the coniferous forest can have a local effect on floristic richness and regeneration of tree saplings. The ground vegetation was compared in 2?m radius plots around the stem under the canopies of matched conifer–deciduous trees in a mature, conifer-dominated forest, and included in the analysis variables that could potentially mediate the tree effect (soil pH, cover of lichens, bryophytes, leaf and needle litter). The field layer vegetation was more species rich under birch (Betula pendula and B. pubescens) than under conifers (Picea abies and Pinus sylvestris), and several vascular plant species (including saplings of tree species) occurred more often under birch than under conifers. However, when the effect of the number of subordinate trees was taken into account the difference between birch and pine was not significant. The number of tree regenerations (saplings) was lowest under pines, but did not differ between spruce and birch. There were no effects of the canopy species on soil pH or on cover of lichens and bryophytes. The difference in diversity may be caused by the different effects of leaf and needle litter, and it is also likely that canopy structure has an influence via interception and throughfall and by affecting the light and microclimate.     

Population structure of Bursaphelenchus xylophilus within single Pinus thunbergii trees inoculated with two nematode isolates

A study was performed to clarify the population structure of the pinewood nematode, Bursaphelenchus xylophilus, within single Pinus thunbergii trees after double infection of nematode populations using the polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) method. Two nematode isolates, which had different levels or the same level of virulence, were inoculated into 6‐year‐old trees at the same or different times and then the propagated nematodes were collected from the trees after 1, 6 and 9 months. When a virulent and an avirulent isolate were inoculated into a single tree, an overwhelming propagation of the virulent isolate was observed there irrespective of the inoculation order of isolates or collection time of nematodes. However, when two virulent isolates were inoculated, propagation through the interbreeding between the two isolates was observed. In the case of the staggered inoculations with two virulent isolates, the frequency of nematodes with a PCR‐RFLP pattern of the primarily inoculated isolate increased with the time after nematode inoculations. This suggested that the population structure of B. xylophilus within a single tree varied by the virulence level of nematode populations transmitted and their transmission order.     

Inoculation of several Bursaphelenchus xylophilus group nematodes into adult trees of Pinus thunbergii and their survival in the trees

To clarify the pathogenicity of Bursaphelenchus nematodes to adult pine trees, inoculation experiments using six species of B. xylophilus group nematodes and ca. 10‐year‐old trees of Pinus thunbergii were conducted. Trees inoculated with an avirulent isolate (C14‐5) of B. xylophilus did not die during the survey, but showed a decline in oleoresin exudation compared with the controls. Fifteen months after the inoculation, a small number of B. xylophilus survived in a tree inoculated with B. xylophilus C14‐5. Trees inoculated with B. mucronatus, B. doui, B. luxuriosae, B. conicaudatus and Bursaphelenchus sp. NK224 (undescribed) showed no decline in oleoresin exudation and no external symptoms of wilt. However, 9 months after the inoculation, a small number of B. luxuriosae survived in a tree inoculated with the nematodes, although four other nematode species were not isolated from trees inoculated with them. These results were approximately consistent with our previous results (Kanzaki, N.; Aikawa, T.; Maehara, N.; Ichihara, Y., 2010, J. For. Res.; in press), in which an avirulent isolate (OKD‐1) of B. xylophilus and B. luxuriosae caused water flow inhibition without external symptoms in 3‐year‐old seedlings. Therefore, to examine the pathogenicity of the nematodes to pines, it is useful to use 3‐year‐old seedlings in inoculation experiments when adult trees cannot be used.     

Susceptibility of four conifer species to Gremmeniella abietina

G. abietina causes severe dieback in pole-stage stands of Scots pine in Britain. The susceptibility of ll provenances of Scots pine and of three other conifer species was tested by inoculations. Significant differences in susceptibility were found amongst Scots pine provenances, with those originating from a native Scottish pinewood at Loch Maree showing the highest levels of disease. Corsican pine was shown to be the most susceptible species tested although sporulation was greatest on Scots pine. Norway spruce was also shown to be susceptible when inoculated late in the growing season. Infection in lodgepole pine was negligible. High levels of β-phellandrene were tentatively linked with resistance among trees in a single stand of Scots pine.     

Comparative performance of four multi-purpose trees associated with four grass species in the humid regions of Southern India

The results of a field trial conducted at the Livestock Research Station, Thiruvazhamkunnu, Kerala to study the compatibility of different components in a silvo-pastoral system revealed that growth and yield of fodder species were significantly influenced by the tree components only after tree canopy formation. The fodder species such as Pennisetum purpureum Schum., Panicum maximum Jacq., Brachiaria ruziziensis Griseb. and Euchlaena mexicana Schrad. grown in association with Casuarina equisetifolia J. R. & G. Forst. and Ailanthus malabarica DC recorded comparatively higher forage yield even after canopy formation. However, forage crops grown in combination with Acacia auriculiformis A. Cunn. ex Benth. and Leucaena leucocephala (Lam.) de Wit. registered relatively lower values for growth and yield. Increased light infiltration into the understorey due to the cladophyllous canopy can be attributed as reason for the higher fodder productivity under Casuarina. Due to the combination of crown size and shape, tree height and spacing the amount of light intercepted by Ailanthus also was very low. Among the four multi-purpose trees used, Acacia recorded the maximum growth rate followed by Casuarina, Ailanthus and Leucaena. Forage productivity of the four species was in the order: Pennisetum purpureum > Panicum maximum > Brachiaria ruziziensis > Euchlaena mexicana. Casuarina with Pennisetum/ Panicm were found to be optimal tree — forage combinations for silvo-pastoral systems.     

Virulence of Bursaphelenchus mucronatus to pine seedlings and trees under field cownditions

Bursaphelenchus mucronatus is a parasitic nematode of pine that is widely distributed in the natural pine forests of Asia and Europe. It has a very similar morphology and biology to that of Bursaphelenchus xylophilus, the causal agent of pine wilt disease, but has generally been considered to be non‐pathogenic to pine. However, in some provinces of China, B. mucronatus has been isolated from dead pine trees rather than B. xylophilus. Previous studies have shown that B. mucronatus can induce the death of pine seedlings under glasshouse conditions. To investigate the virulence of B. mucronatus, 2‐year‐old seedlings of Pinus massoniana and Pinus elliottii were inoculated with one of six isolates of B. mucronatus under field conditions in April 2014 and their condition was monitored over a year. The virulence of the six B. mucronatus isolates differed on the three host species: P. elliottii seedling mortality ranged from zero to six of the 18 inoculated seedlings, whereas P. massoniana seedling mortality ranged from four to 12 of the 18 inoculated seedlings. Three B. mucronatus isolates that appeared to cause different levels of mortality among the seedlings were used to inoculate 12‐year‐old Pinus thunbergii trees in August 2014. The trees were monitored for a year, during which time between 4 and 12 of the 18 inoculated trees in each treatment wilted and died. The average monthly temperature during the test period appeared to be similar to that of the historical average in the test areas; however, both study sites experienced above‐average rainfall. This study demonstrated that B. mucronatus has potential virulence on pine trees and provided experimental evidence that high temperatures or drought stress is not essential for the virulence of B. mucronatus.     

松材线虫病致死松树上的松褐天牛季节性分布规律

连续两年定期监测、调查采样和鉴定证明：每年６～１０月出现的松材线虫病Ｂｕｒｓａｐｈｅｌｅｎｃｈｕｓｘｙｌｏｐｈｉｌｕｓ致死松树上，松褐天牛Ｍｏｎｏｃｈａｍｕｓａｌｔｅｒｎａｔｕｓ虫株率为１００％，而１１月至次年５月间出现的病死株上，虫株率为零。对前者应集中砍除，并加以严格的除害处理；后者可经剥皮处理后在疫情发生区内加工利用，部分可留在林间作为天牛产卵的饵木     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

On the genus Bursaphelenchus Fuchs, 1937 (Nematoda: Parasitaphelenchinae) associated with wood and insects from declining forest trees in the Czech Republic

An overview of the genus Bursaphelenchus in the Czech Republic is presented, based on a recent survey for monitoring the presence of the pinewood nematode, Bursaphelenchus xylophilus, as well as on previous reports of this genus in the country. In addition, we provide a morphological and molecular characterization of four Bursaphelenchus species (B. eremus, B. pinophilus, B. vallesianus and B. borealis) found during the monitoring programme for forest pests, conducted during 2006–2010, within the Moravian and Bohemian regions. Nematodes were extracted from over 1917 insects and 1493 wood samples collected from deciduous and coniferous trees exhibiting wilting and declining symptoms. Bursaphelenchus species were found only in 0.73% of insects and 0.47% of the total number of wood samples. Bursaphelenchus borealis and B. pinophilus dauer juveniles were found associated with the insect vectors Dryocetes autographus and Pityogenes bidentatus, respectively. While a total of seven Bursaphelenchus species are now reported from the Czech Republic, the status of B. xylophilus remains as absent.     

Decline‐associated Phaeoacremonium species occurring on forest trees in the north of Iran

Between 2013 and 2015, several surveys were conducted throughout forest areas in the north of Iran with the aim of isolating and identifying fungi present on trees showing decline symptoms. Fungal species, isolated from symptomatic wood tissues of various tree genera, including Zelkova, Acer, Parrotia, Quercus, Diospyros, Fagus, Fraxinus, Populus, Pinus, Pterocarya, Gleditsia, Carpinus, Ulmus, Crataegus, Alnus, Mespilus, Punica, Cydonia, Cupressus and Prunus, were morphologically identified and characterized. A molecular identification based on comparisons of DNA sequences of the β‐tubulin gene allowed us to identify seven species belonging to Phaeoacremonium; namely, Phaeoacremonium parasiticum, Pm. alvesii, Pm. minimum, Pm. iranianum, Pm. scolyti, Pm. fraxinopennsylvanicum and Pm. croatiense were isolated and identified. Phaeoacremonium minimum was the most common species and isolated from Gleditsia caspica, Parrotia persica, Cydonia oblonga and Alnus glutinosa. Pathogenicity on selected plants using a mycelium plug inoculation method revealed that most of these species are pathogenic to all the tested trees, with Pm. parasiticum and Pm. minimum being the most pathogenic species. According to host plant species and geographical distribution, the majority of Phaeoacremonium species found represent new records. This is also the first report of Pm. croatiense in Iran and outside Croatia.     

Comparing needle and shoot phenology with xylem development on three conifer species in Italy

? Since the 1960s biologists have been trying to assess factors affecting cambial activity and latewood formation. A comparison of the phenology of the apical and lateral meristems could add new clues in order to understand mechanisms of the growth dynamic in conifers.

? This study compared needle and shoot growth with xylogenesis in Larix decidua, Pinus cembra and Picea abies during 2001 to verify if cambial resumption occurred after shoot and needle growth had begun, and if latewood initiation occurred when shoot lengthening was complete.

? In pine and spruce, needle and shoot lengthening was synchronous between mid-June and August while larches showed an early development of the needles at the end of May with a later shoot lengthening. Cell production lasted from mid-May to the beginning of August, with the first differentiating cells observed at the end of May, which indicated a earlier reactivation of the cambium with respect to needle and shoot growth.The first latewood cells began wall thickening between July and August, during the termination of needle and shoot lengthening.

? The hypothesis that cambial resumption occurs after shoot and needle elongation was rejected. The separation in time between apical growth and secondary wall thickening of latewood suggested the presence of an internal competition in resource allocation.

     

松树抗松材线虫病机理的研究进展

松材线虫病 [Bursaphelenchusxylophilus(Steiner&Buhrer)Nickle]是一种毁灭性的森林病害。不同松种和同一松种不同种源的抗病性存在明显差异 ;松树通过固有或诱导的防卫系统抵抗松材线虫的扩散和繁殖。本文就国内外关于松树抗松材线虫病机理方面的研究进行综述     

Light-related competitive effects of overstory trees on the understory conifer saplings in a subalpine forest

To clarify the mechanism by which overstory trees shade understory saplings, we investigated the relationships among light conditions of the saplings (measured as indirect site factor; ISF and direct site factor; DSF), the calculated competition effects of overstory trees on the saplings (W), and relative height growth rate of the saplings (RHGR). We calculated several W values in order to find a W value which can express the light conditions as appropriately as possible, and the results indicated that W explained only 21.9%–24.7% of the total variance of light conditions in the cases where W gave the best fit. In this study, W was calculated based on the basal areas of overstory trees. However, it is known that canopy structure also affects the light regimes in the forest understory, and this might yield the possible errors even within W representing the shading effects most adequately. Therefore, although W significantly represents the shading effect from overstory trees, a great proportion of the variance remained without being explained by W. RHGR was negatively correlated with W, and the W value which had the most adequate explanation of the shading effect also showed the best negative correlation with RHGR. This provides the evidence that the competitive effect of overstory trees on sapling growth is mediated by the shading effect, indicating that competition for light clearly exists within this forest. Such competition for light may closely relate to the well-known phenomenon of gap regeneration in subalpine forests in central Japan.