松树脂溃疡病菌的风险分析及应对策略

松树脂溃疡病菌是严重为害松树的一种林木病原真菌,文章从该病菌的国内分布状况、潜在经济危害性、寄主植物经济重要性、传播扩散可能性和危险性管理难度等方面进行了定性和定量分析,结果表明:松树脂溃疡病菌在我国属于高度危险性的有害生物,需加强对该病菌的检疫封锁及监测,防止其入侵与危害。文章最后提出了防止其入侵及发生为害的应对策略。     

松树脂溃疡病菌及其近缘种AFLP分析

利用AFLP分子标记技术对松树脂溃疡病菌及其近缘种进行DNA指纹分析,筛选出10对多态性较高的引物.上述引物在供试的9种17个菌株中共扩增出298条带,其中有多态性带283条,多态性位点百分率为94.97%.每对引物产生的多态性位点百分率在89.29%-100%之间,表明松树脂溃疡病菌及其近缘种间在DNA水平上存在广泛变异.根据AFLP标记结果计算松树脂溃疡病菌及其近缘种间的相似系数,对它们的亲缘关系进行定量描述.聚类分析结果表明,菌株间的聚类与生物学种分类的结果一致.分析引物E-AT/M-CAA绘制的镰刀菌AFLP指纹图谱遗传多样性,确定李瑟组镰刀菌各交配群的特异带、差异带,区分供试的7个交配群.     

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.     

AFLP analysis of Fusarium circinatum and relative species

AFLP fingerprinting analysis of Fusarium circinatum, Nirenberg and O’Donnell and relative species was carried out. Ten primer-pairs that could generate abundant polymorphism fragments were screened. A total of 298 nucleotide acid fragments were amplified with the primers from the template of the 17 strains of Fusarium spp., among which 283 fragments were polymorphic. Percentage of polymorphic loci produced by each pair of AFLP primer-pair was 94.97% in average and varied from 89.29% to 100%. All these data indicated that considerable genetic variation existed among F. circinatum and relative species at DNA level. Molecular genetic distances among Fusarium spp. were calculated, and the relationship among them was described quantitatively. Compared with biological species, the result of cluster analysis was basically similar to the phenotypic classification of species. Genetic diversity of E-AT/M-CAA AFLP fingerprinting of Fusarium spp. was analyzed, and specific and difference bands for each species and all Fusarium section Liseola tested were identified based on the E-AT/M-CAA AFLP fingerprinting.     

Pitch canker ratings of longleaf pine clones correlate with Fusarium circinatum infestation of seeds and seedling mortality in containers

The incidence and severity of pitch canker was rated among 16 clones of mature longleaf pine (Pinus palustris) in a seed orchard and cones were collected from five of those clones across the range of pitch canker disease ratings. Seed were extracted and commercially processed by clone and the percentages contaminated with Fusarium circinatum determined. Seed from each clone were sown either without treatment or with one of three fungicide treatments in a soil‐less mix at a commercial container nursery to evaluate the effects of F. circinatum (syn. F. subglutinans) on seed and seedling survival. The percent of seed with F. circinatum correlated with the pitch canker ratings in the orchard for the year of collection (r = 0.88, p = 0.05) and, when sown without fungicide treatment, with the number of seedlings produced (r = ?0.94, p = 0.01) and with seedling mortality after germination (r = 0.92, p = 0.02). The same orchard clones were more symptomatic of pitch canker through three annual surveys. Fusarium circinatum was isolated from a higher percent of seed from more symptomatic clones and a lower percent of their seed produced plantable seedlings. We propose that removing such clones from seed collections should reduce seedling mortality at the nursery.     

Assessment of molecular detection of Fusarium circinatum in insects and passive spore traps in Pinus radiata plantations

Fusarium circinatum is the causal agent of pitch canker, a destructive disease that threatens natural and planted pine forests around the world. Although pitch canker has caused problems in Spain and Portugal, concerning Europe as a whole, the fungus is not established across the pine distribution area. Its dispersion by wind and/or insect vectors could nevertheless play a role in the colonization of currently uninfected stands. It is therefore crucial to develop monitoring tools for its detection. To this end, we assessed the molecular detection of the pathogen in environmental samples of bark beetles and passive spore traps, collected in two infected Pinus radiata plantations in Basque country, Spain. The spread pattern of F. circinatum was assessed by an experimental design that included insect and spore traps installed at the centre, at the edge and outside the plots. Our results showed that F. circinatum was detected in both types of samples, at almost all collection dates. In both type of samples, positive detections were mainly found at the centre of the plots, a lower proportion at the edge, and very few outside. This suggests that long‐distance dispersion of Fusarium circinatum does not rely on wind spore dispersal neither on insect flight. Our study also shows that molecular methods are a powerful tool to monitor the pathogen in environmental samples.     

Resistance levels of Spanish conifers against Fusarium circinatum and Diplodia pinea

Pitch canker, caused by Fusarium circinatum, and Diplodia shoot blight, caused by Diplodia pinea, are both damaging to pines (Pinus spp.) grown in plantations throughout the world, including Spain. To assess the potential for interspecific differences in susceptibility to contribute to the management of pitch canker and Diplodia shoot blight in the Atlantic region of Spain, the present study was undertaken to characterize the susceptibility of six pine species (P. sylvestris, P. nigra, P. pinaster, P. radiata, P. halepensis and P. pinea) and Douglas‐fir (Pseudotsuga menziesii) to F. circinatum and D. pinea. Based on inoculations of 2‐year‐old trees, Ps. menziesii, P. pinea and P. nigra were the most resistant to F. circinatum, with lesion lengths ranging from 3.7 to 21.5 mm, 2.2 to 12.6 mm and 2.8 to 30.9 mm, respectively. At the other extreme, Pinus radiata was the most susceptible, sustaining lesions that ranged from 8.5 to 74.8 mm in length. Pinus sylvestris, P. pinaster and P. halepensis showed an intermediate response to F. circinatum. Broadly similar results were observed in inoculations with D. pinea, with Ps. menziesii being relatively resistant and P. radiata being highly susceptible. Consistent with these results, field surveys revealed no pitch canker in stands of Ps. menziesii and low severity of Diplodia shoot blight, whereas P. radiata was severely affected by both diseases. Our findings suggest that selection of appropriate species can greatly reduce the risk of damage from two important canker diseases affecting pine plantations in the Atlantic region of Spain. Furthermore, intraspecific variation in susceptibility implies that selection may allow for the enhancement of resistance in otherwise susceptible species.     

In silico annotation of five candidate genes associated with pathogenicity in Fusarium circinatum

The Pine Pitch Canker disease caused by the pathogenic fungus Fusarium circinatum is one of the most devastating diseases in pine forests, afforestation and nurseries around the world. Despite the importance of this phytopathogen, only a little is known about the genes that drive the infection traits and the virulence factors. In this work, five candidate genes (i.e. Fcfga1, Fcfgb1, Fcac, Fcrho1 and FcpacC) were in silico annotated using the whole genome of F. circinatum as reference. The similarity of these proposed genes at nucleotide and protein levels with genes previously described in other Fusarium species was > 90% of identity and > 90% query coverage in all cases. In addition, the gene ontology of each candidate gene was also investigated.     

四川地区云南松切梢小蠹监测技术研究

在四川云南松切梢小蠹发生有代表性的云南松林中采用漏斗状诱捕器和饵木堆在切梢小蠹梢转干高峰期 ,在目测踏查无切梢小蠹发生危害和切梢小蠹发生危害轻两种不同发生程度的云南松林分中使用漏斗状诱捕器和饵木堆两种方法对切梢小蠹是否发生、发生危害程度能进行有效的监测 ,两种方式的监测有效率均达 10 0 %。在无切梢小蠹发生危害和切梢小蠹发生危害轻的两种云南松林分中诱捕器监测准确率分别达 70 %和 6 0 %以上 ,监测有效半径为 30m ,安置方式为每 35m× 35m置漏斗状诱捕器 3套 ;饵木监测准确率分别达 80 %和 70 %以上 ,监测有效半径为 2 0m ,安置方式为每 30m× 30m置饵木堆 3堆 ,每堆 12根饵木按 #字型排立。两种方式的监测效果均高于人工目测踏查法     

Tolerance of Pinus patula full-sib families to Fusarium circinatum in a greenhouse study

The pitch canker fungus, Fusarium circinatum, has caused large-scale mortality of young Pinus patula Schiede and Deppe ex Schltdl. and Cham. seedlings in nurseries in South Africa since 1990. Diseased seedlings have been inadvertently carried to the field, which in turn have died and has reduced stocking below an acceptable level. Tree breeders have suggested that the only long-term solution to limit infection by this pathogen is to identify and deploy tolerant P. patula families. A commonly used technique to identify tolerant clones is to artificially inoculate open-pollinated progeny from orchard clones with F. circinatum under greenhouse conditions. In these trials, large variation in tolerance to the pathogen among seedlings within open-pollinated families was observed and this could be influenced by the pollen parent. Therefore, identifying individual full-sib families, where both parents are known, should improve the identification of tolerant families, which can then be repeated. In this study, cuttings from control-pollinated P. patula seedling hedges were inoculated with F. circinatum in a greenhouse. The results showed large family variation where some of the full-sib families were similar in tolerance to P. elliottii Engelm. var. elliottii seedlings. Therefore, it is recommended that breeders focus on identifying specific family combinations that are more tolerant to F. circinatum.     

松树脂溃疡病菌的分子检测

松树脂溃疡病(Fusarium circinatum)为美国、南非等国外针叶树上发生的一种危险性林木病害(Storer et al.,1994;Viljoen et al.,1994).该病害常引起寄主树干流脂溃疡、雌花和球果坏死、种子变质以及苗木枯死.其病原菌可随种子、苗木、病木木材、媒介生物以及黏附土壤进行远距离传播.日本1989年(Kobayashi et al.,1989)、墨西哥1991年(Guerra et al.,1991)、南非1994年(Viljoen et al.,1994)、智利2001年(Wingfield et al.,2001)等地相继发现有松树脂溃疡病为害,该病害在世界各地呈现出迅速蔓延之势.     

Antioxidant activity of Pinus pinaster infected with Fusarium circinatum is influenced by maternal effects

The antioxidant activity of Pinus pinaster seedlings originating from two contrasting maternal environments and inoculated with the fungal pathogen Fusarium circinatum was examined. The antioxidant activity related positively to the stem necrosis caused by the pathogen (p = 0.005), but this relationship differed significantly between maternal environments (p ≤ 0.002). Seedlings from mother trees grown under a favourable environment expressed a more variable antioxidant activity to F. circinatum than seedlings from mother trees grown in a less favourable environment. Antioxidant activity ranging from 80 to 100% resulted in shorter necrosis in seedlings from the favourable maternal environment than in seedlings from the unfavourable environment. Maternal effects caused shifts in the relationship between antioxidant activity and necrosis in offspring, and significantly modified the individual plant capacity for antioxidant response on pathogen penetration.     

Evaluation of Pinus radiata seed treatments to control Fusarium circinatum: effects on seed emergence and disease incidence

In this study, the effects of hot water (HWT), hydrogen peroxide and fungicides on the incidence of Fusarium circinatum on artificially inoculated Pinus radiata seeds were evaluated. Fifteen commercial fungicide formulations were screened in vitro for inhibitory activity on mycelial growth and conidial germination of F. circinatum. With half‐maximal effective concentration (EC₅₀) lower than 0.5 ppm, fluazinam, imazalil and tebuconazole were the most effective fungicides on mycelial growth, while captan, mancozeb or pyraclostrobin were the most effective (EC₅₀ < 0.3 ppm) on conidial germination. Based on the results obtained, imazalil, fluazinam, mancozeb and pyraclostrobin were selected for further testing. The effects of HWT, hydrogen peroxide and fungicide treatments on seed emergence and the incidence of F. circinatum were assessed. Seed treatments with fungicides prior to sowing were less effective and inconsistent in reducing the incidence of F. circinatum on seedlings. In contrast, hot water and hydrogen peroxide treatments significantly reduced F. circinatum contamination on P. radiata seeds with an overall disease incidence lower than 0.8% on seedlings. Furthermore, subsequent application of fungicides on seedlings did not improve the effectiveness of HWT. These results, therefore, suggest that hot water is a better alternative to hydrogen peroxide and fungicides as Pinus seed treatment against F. circinatum and could easily be implemented as standard in commercial nurseries to control the spread of the pitch canker disease.     

High genetic diversity of Fusarium circinatum associated with the first outbreak of pitch canker on Pinus patula in South Africa

The disease known as pitch canker results from infection of Pinus species by the fungus Fusarium circinatum. This fungus also causes a serious root disease of Pinus seedlings and cuttings in forestry nurseries. Pinus radiata and P. patula are especially susceptible to the pathogen, but there are no records of pitch canker on P. patula in established plantations. To date, only planting material of this tree species in nurseries or in plantations at the time of establishment have been infected by F. circinatum. Symptoms of pitch canker have recently emerged in an established P. patula plantation in South Africa and this study sought to determine whether the symptoms were caused by F. circinatum. Isolates from cankers were identified as F. circinatum using morphology and DNA-based diagnostic markers. Microsatellite markers were then used to determine the genetic diversity of a collection of 52 isolates. The entire population included 17 genotypes representing 30 alleles, with a greater number of genotypes collected from younger (three- to six-year-old) than older (12- to 19-year-old) trees. Both mating types of F. circinatum were present, but no evidence of sexual recombination was inferred from population genetic analyses. This is the first record globally of pitch canker on P. patula trees in managed plantations. It is of significant concern to South Africa, where P. patula is the most important Pinus species utilised for plantation forestry.     

Multi-scale nest-site selection by black-backed woodpeckers in outbreaks of mountain pine beetles

Areas of mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreaks in the Black Hills can provide habitat for black-backed woodpeckers (Picoides arcticus), a U.S. Forest Service, Region 2 Sensitive Species. These outbreaks are managed through removal of trees infested with mountain pine beetles to control mountain pine beetle populations and salvage timber resources. To minimize impacts to black-backed woodpeckers while meeting management objectives, there is a need to identify characteristics of these areas that support black-backed woodpeckers. We examined the habitat associations of this species nesting in areas of beetle outbreaks in the Black Hills, South Dakota in 2004 and 2005. We used an information theoretic approach and discrete choice models to evaluate nest-site selection of 42 woodpecker nests at 3 spatial scales—territory, nest area, and nest tree. At the territory scale (250 m around nest), availability and distribution of food best explained black-backed woodpecker selection of beetle outbreaks versus the surrounding forest. Selection at the territory scale was positively associated with densities of trees currently infested by mountain pine beetles and indices of wood borer (Cerambycidae and Buprestidae) abundance, and was greatest at distances of 50–100 m from the nearest patch of infestation. At the nest-area scale (12.5 m radius around the nest), densities of snags positively influenced nest-area selection. Finally, at the nest-tree scale, aspen (Populus tremuloides) and 3–5-year-old ponderosa pine (Pinus ponderosa) snags were important resources. The association between abundant wood-boring insects and black-backed woodpeckers creates a difficult challenge for forest managers. In the absence of fire, areas of beetle outbreak might serve as the only substantial source of habitat in the Black Hills. Regulating insect populations via salvage logging will reduce key food resources to black-backed woodpeckers during nesting. Therefore, given the relatively infrequent occurrence of large-scale fire in the Black Hills, management should recognize the importance of beetle-killed forests to the long-term viability of the black-backed woodpecker population in the Black Hills.     

Ophiostomatoid fungi associated with root‐feeding bark beetles on Scots pine in Poland

Ophiostomatoid fungi are known to be associated with various species of bark beetles. However, information about fungal associates of root‐feeding bark beetles in Europe is still fragmentary. For this reason, the fungal associates of Hylastes ater, H. opacus and Hylurgus ligniperda on Pinus sylvestris were isolated and identified. A total of 743 fungal isolates were collected and separated into 10 morphological groups. Analyses of ITS rDNA and partial β‐tubulin gene sequences confirmed that these groups represented distinct species. The 10 species included a total of 13 associations between fungi and bark beetles that had not been recorded previously. All of the bark beetles examined were frequently associated with ophiostomatoid fungi. The fungal diversity and relative abundance of species were very similar in the three species of root‐feeding bark beetles. The most commonly encountered associates of these beetles were Grosmannia radiaticola, Leptographium lundbergii, L. procerum and L. truncatum. Insect infestation data furthermore suggest that Hylastes spp. and Hg. ligniperda are also important vectors of the fungal pathogen Sphaeropsis sapinea.     

Bark beetles on pine logs: forecasting winter colonisation dynamics based on trap catches and temperature records

Journal of Pest Science - Seasonality influences the abundance and activity of forest insects. Harvesting during periods of reduced activity could minimise colonisation risk on logs and reduce the...     

Future outlook for Pinus patula in South Africa in the presence of the pitch canker fungus (Fusarium circinatum)

Approximately 50% of the area planted to softwood trees in South Africa has been established with Pinus patula, making it the most important pine species in the country. More effort has gone into developing this species for improved growth, tree form and wood properties than with any other species. This substantial investment has been threatened in the last 10 years by the pitch canker fungus, Fusarium circinatum. The fungus infects and contaminates nursery plants and, once transferred to the field, causes severe mortality of young trees in the first year after establishment. Although nurserymen have some control of the disease, it is recognised that the best long-term solution to mitigate damage because of F. circinatum infection is to identify tolerant species, clones and hybrids for deployment in plantations in the future. Research has shown that alternative species such as P. tecunumanii, P. maximinoi and P. elliottii are suitable for warm sites. Pine hybrids, particularly between P. patula and the high-elevation sources of P. tecunumanii, appear to be a suitable replacement on subtemperate and temperate sites. Although these alternative species and hybrids are more sensitive to subfreezing temperatures than P. patula, their planting range can be increased by including cold tolerance as a selection criterion. Future breeding efforts will most certainly focus on improving the tolerance of pure P. patula to F. circinatum, which can be achieved by identifying specific family crosses and tolerant clones. The commercial deployment of disease-tolerant control-pollinated P. patula and hybrid families will most likely be established as rooted cuttings, which requires more advanced propagation technology. In the long term, new seed orchards comprised of P. patula clones tolerant to F. circinatum could be used to produce seed for seedling production.