To assess the role of bacteria in pine wilt disease (PWD), aseptic M form (with a mucronated tail) and R form (with a round tail) of Bursaphelenchus xylophilus and B. mucronatus were obtained and compared, in terms of reproduction and pathogenicity, with non-aseptic nematode. In addition, bacteria isolated from non-aseptic nematodes and pine trees inoculated with non-aseptic nematodes were identified. The results indicated that the bacteria associated with nematodes significantly lowered the reproduction of R form of B. xylophilus and B. mucronatus. Both the non-aseptic and aseptic R forms of B. xylophilus induced death in all infected 7- to 8-year-old pine trees, while the non-aseptic and aseptic M forms of B. xylophilus and B. mucronatus caused almost no plant mortality. High numbers of the non-aseptic and aseptic R forms of B. xylophilus were distributed throughout the inoculated trees, while B. mucronatus and M form of B. xylophilus nematodes were lower in number and their distribution in stems limited within the inoculation site. Bacteria isolated from non-aseptic nematodes were not recovered from the pine trees inoculated with these same kinds of nematodes. Two species of bacteria were both isolated from non-aseptic B. mucronatus and from R form of B. xylophilus. Microbacterium trichotecenolyticum was common to both the control and inoculated pine trees. These results suggest that R form of B. xylophilus is the causal agent of PWD and that bacteria cannot increase the virulence of B. xylophilus and B. mucronatus.

This is the first report and characterization of Bursaphelenchus pinophilus in Portugal. This species was isolated from a young dying Pinus pinaster tree located in Valverde, in the Alentejo region. Nematodes were identified using several morphological diagnostic characters for this species (male spicule structure, number of lateral incisures, number and distribution of the male papillae, presence of female vulval flap and female tail shape) and confirmed using RFLP analysis of the internal transcribed spacer (ITS) regions of ribosomal DNA.

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.

Fomitiporia hartigii s.l. is an important trunk rot pathogen of conifers throughout the Northern Hemisphere. In North America, this pathogen primarily attacks Tsuga, but is also found on Abies, Picea and Pseudotsuga. Previous research showed that isolates of F. hartigii from North America represent a distinct phylogenetic species, known as F. tsugina. However, that conclusion is based on limited data. To better understand the phylogenetic relationships of F. tsugina in North America, a phylogenetic analysis was performed using three loci (internal transcribed spacer, nuclear large subunit and tef1) with 23 isolates originating from the northern United States, Canada and central Europe. North American isolates formed a monophyletic group with significant statistical support, confirming previous reports that F. tsugina represents a unique phylogenetic species, distinct from European F. hartigii s.s. Population subdivision between isolates of F. tsugina from eastern (Massachusetts, Michigan, New Hampshire, New York and Wisconsin) and western (British Columbia, Colorado, Oregon and Washington) North America was investigated. Tests of gene flow and genetic differentiation based on region of origin detected significant variation (F_ST = 0.761; K_ST = 0.625, p < 0.01), suggesting gene flow between the two populations may be limited. Neutrality tests revealed significant, negative departures from the standard neutral model, which could indicate that a purifying or stabilizing selection has maintained low levels of polymorphisms in the population, perhaps favouring an advantageous phenotype. Further studies are required to better understand the occurrence of F. tsugina on Abies and Picea in boreal forests outside the natural range of Tsuga.

A phytoplasma infecting Sophora Root (Sophora alopecuroides) was detected and identified in Alar, Xinjiang Uygur Autonomous Region of China. Typical phytoplasma bodies were observed in sieve tubes of the diseased plants by transmission electron microscopy. A partial 16S rRNA gene and ribosomal protein (rp) genes containing rpl22 (rplV) and rps3 (rpsC) were amplified by direct and nested PCR. Based on the sequence similarity of the 16S rRNA and rp genes with accompanying phylogenetic analyses, the phytoplasma associated with Sophora Root yellows belongs to the 16SrI group (aster yellows group). Virtual RFLP analysis of these 16S rRNA and rp gene sequences showed distinct differences from those of reference phytoplasma strains representing previously described subgroups of the 16SrI group. Moreover, the similarity coefficient (0.92) of the RFLP profile of this phytoplasma was less than the threshold similarity coefficient (0.97) required for subgroup classification. Thus, the phytoplasma isolate of Sophora Root plants, designated as ‘SoRY’, represents a new subgroup. Furthermore, this is the first report of phytoplasma disease associated with Sophora Root plants.

A survey was conducted in forest sites of the Muğla Regional Forest Directorates for the presence of the pinewood nematode, Bursaphelenchus xylophilus. Wood samples were collected from declining pine and cedar trees. A total of 207 samples were taken, and nematodes were extracted, observed and identified. The pinewood nematode was not detected, but another Bursaphelenchus species was recovered from the wood of a Pinus brutia tree in Eşen-Karadere location in Fethiye, which strongly resembled the original description of B. hellenicus. It was identified as this species by morphology and ITS-RFLP. Measurements and diagnostic features are presented. This is the first report of B. hellenicus from Turkey.

European mountain ash ringspot-associated virus (EMARaV) is a plant virus inducing characteristic ringspots and mottling in Sorbus aucuparia L. For the first time, EMARaV was detected in mountain ash in Sweden. All four genomic segments of the virus were detectable by RT-PCR after total RNA extraction from leaves showing chlorotic ringspots, mottling or necrotic lesions. The samples originated from southern and northern Sweden. Sequence analyses of amplified fragments revealed low genetic variability of the virus at nucleotide as well as protein level. All investigated coding regions of EMARaV were under strong purifying selection pressure.

Kauri Agathis australis, an iconic tree of New Zealand, is under threat from an introduced disease-causing pathogen provisionally named Phytophthora ‘taxon Agathis’ (referred to as PTA). This soilborne, Pythiaceous species belongs to the Chromista and causes a collar rot resulting in yellowing of the foliage and thinning of the canopy, which eventually causes death of the infected tree. The management and containment of this pathogen requires rapid and reliable detection in the soil. The current method for soil detection utilizes a soil bioassay involving lupin baits and soil flooding in a process that takes between ten and twenty days. We describe a real-time PCR assay based on TaqMan chemistry for the specific detection of PTA, which targets the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA. This TaqMan real-time PCR assay could be used with DNA extracted directly from bulk soil samples to enable rapid quantification of PTA within soil. The detection limit was 2 fg of PTA DNA from pure culture, or 20 fg in the presence of DNA extracted from soil. The assay was validated using soil samples taken from a PTA-infested site and soil spiked with a known concentration of oospores. We conclude that the TaqMan real-time PCR assay offers a more time-efficient method for detection of PTA in soil than existing methods.

Incidence of peach [Prunus persica (L.) Batsch] tree mortality attributed to Armillaria root disease was assessed from 2009 to 2011 in 15 orchards in the State of Mexico, Mexico. Incidence increased gradually every year of assessment, reaching average values of 9.7, 15.3 and 20.3% tree mortality and 23.2, 24.7 and 28.3% disease-impacted area of the orchards during 2009, 2010 and 2011, respectively. The cultivars ‘Nemaguard’ and ‘Criollo of La Goleta’, a local rootstock used in the region, were both susceptible to the disease. To identify species of Armillaria isolated from infected peach trees, two nuclear rDNA regions (partial 5.8S-ITS2-LSU D-domains and partial 3′ LSU-IGS1) and the translation elongation factor-1α (tef-1α) gene were sequenced and compared with sequences of known Armillaria species. DNA sequence analysis from 49 Armillaria isolates revealed that five isolates (10.2%) were Armillaria mellea and eight isolates (16.3%) were Armillaria gallica. DNA sequences from the remaining 36 isolates (73.5%) showed no close similarity to Armillaria sequences in GenBank, and apparently represent an undescribed Armillaria species. This undescribed species was the most widely distributed in the region of study. Separate phylogenetic analyses of the LSU region (D1–D3 domains concatenated with the partial 3′ end) and the tef-1α region show that the undescribed species is quite distinct from other Armillaria spp. reported in North America.

Examination of isolates of Hymenoscyphus albidus from France revealed that this fungus does not form an anamorphic stage in culture. The lack of an asexual stage in this fungus is a conspicuous morphological difference to the ash dieback pathogen Hymenoscyphus pseudoalbidus, which is associated with its Chalara fraxinea anamorphic state. In growth studies on malt extract agar (MEA) and MEA amended with ash leaflets (ash leaf malt extract agar, AMEA) at 20°C, isolates of H. albidus grew slower than those of H. pseudoalbidus. On AMEA, the growth of cultures of both species was greatly enhanced.

Since 2001, the incidence of bleeding canker of horse chestnut (Aesculus hippocastanum) has increased markedly in western Europe. The causal agent, the bacterium Pseudomonas syringae pv. aesculi, originally isolated from foliar lesions on Indian horse chestnut (Aesculus indica) in India, is a bark killing pathogen on A. hippocastanum. In this study, P. syringae pv. aesculi was found as a foliar epiphyte on both A. hippocastanum and A. indica trees growing in the UK. When Aesculus leaves were challenged with cell suspensions (10⁹ CFU ml⁻¹) of Pseudomonas syringae pv. aesculi, a high level of asymptomatic infection occurred in all the species tested. The degree of re-isolation of the bacterium after surface sterilization of leaves ranged from 33% (A. pavia) to 84 and 97% for A. hippocastanum and A. chinensis, respectively. The studies suggest both epiphytic and intrafoliar populations of P. syringae pv. aesculi could play a role in the incidence and spread of bleeding canker of horse chestnut. Growth–temperature responses of P. syringae pv. aesculi indicated a minimum of approximately −4°C and a maximum of approximately 35°C, with an optimum of approximately 25°C. These findings show that P. syringae pv. aesculi is not restricted to bark lesions but is likely to be widespread in the environment. It is also capable of causing foliar infection of several Aesculus species and could persist under extremes of weather in the UK.

An increasing decline and mortality of cork oak trees have been recently observed in central Italy and Sardinia Island. Following surveys conducted in three declining cork oak forests, a Phytophthora species was consistently isolated from soil samples collected from trees displaying different level of decline. Based on morphological features, growth rates at different temperatures and analysis of DNA sequences of the ITS region, all isolates were identified as Phytophthora cinnamomi Rands. This pathogen caused large brownish lesions on inoculated freshly cut branches of cork oak. It was re-isolated from all infected tissues. These findings represent the first report of P. cinnamomi on cork oak trees in Italy.

The genus Metrosideros includes several tree, shrub and vine species, native to the Pacific Islands. Seedlings from 25 seed lots of Metrosideros polymorpha and two seed lots of M. tremuloides with symptoms of root rot, stem girdling, wilting and round, purple leaf spots were observed in the Forestry Nursery at the Universidade Federal de Viçosa, Brazil. In the original disease site, seedling mortality reached up to 71% in M. polymorpha and 34% in M. tremuloides. Single conidial cultures obtained from infected leaf, root and stem samples of M. polymorpha were used to identify the fungal species. Morphological characters and DNA sequences of four loci, containing partial sequences of β-tubulin (TUB2), histone H3 (HIS3), calmodulin (CAL) and the elongation factor (tef-1α) genes of three isolates, indicated that they belong to a new species, described here as Calonectria metrosideri sp. nov. Potting medium infestation and inoculation of seedlings of M. polymorpha with an inoculum suspension at 1 × 10⁴ conidia ml⁻¹ induced typical symptoms of the disease (leaf spots, root rot and wilt), similar to those observed under natural conditions. Calonectria metrosideri was re-isolated, which fulfilled Koch's postulates, and confirmed its status as a pathogen.

Ash dieback is an emerging disease caused by the fungus Chalara fraxinea that severely affects Fraxinus excelsior and F. angustifolia stands in Europe. Previous studies have shown that this pathogen prefers temperatures around 20°C, while its growth in pure cultures at 30°C proved to be very limited. The purpose of this study was to determine the effects of temperature on the development and growth of C. fraxinea in pure cultures and in plant tissues, as well as to test the heat tolerance of F. excelsior saplings. The sensitivity of fungus to heat in ash tissues was higher than in pure cultures. Low isolation success rate from diseased ash tissue after a five-hour hot water treatment at 36°C and the relatively high survival rate of ash saplings after hot water treatments at 36°C and 40°C indicate possibilities for the development of a C. fraxinea eradication method in ash saplings. Field monitoring showed that in hot weather periods, thermal conditions inside the ash tissues can be extreme enough to markedly decrease the viability of C. fraxinea in infected plant tissues.

In this article, we report observations made during thirteen years on foliar fungal pathogens attacking European and Eurasian woody broadleaved species in Siberian arboreta and cities and discuss the possibility of using such data for detecting exotic pathogens that may represent a danger for European tree and shrub species, should these pathogens be introduced into Europe. A total of 102 cases of symptomatic infections (fungus-host plant associations) involving 67 fungal species were recorded on 50 of the 52 European and Eurasian woody plant species. All but four of the fungi found during the surveys were previously reported in Europe. However, 29 fungus–host plant associations are apparently new to science, suggesting that complexes of cryptic species differing in their host range and geographic range may occur. Seventeen percentage of associations were given a high damage score, that is, more than 50% of plant area was attacked, for at least some localities. In nearly half of the cases, fungus–host plant associations were found to be very frequent, that is, occurring every year and at all locations where the plant was inspected. A list of pathogen–host associations in Siberia deserving further investigation is provided, either because the pathogen is not yet recorded in Europe or because the pathogen–host association has not yet been reported, and the damage is high or, finally, because the damage and infestation level is unusually high in known associations. Further studies should involve molecular characterization of these foliar pathogens and their host range testing.

Oak decline has been a serious problem in Europe since the beginning of the twentieth century. In south-west Spain, Quercus ilex and Q. suber are the main affected species, and their decline has been associated with Phytophthora cinnamomi. During the last 10 years, a severe decline of Q. ilex and Q. faginea accompanied by a significant decrease in the production of acorns affecting natural regeneration was observed in the eastern part of the Iberian Peninsula. Therefore, the aim of this study was to investigate the possible involvement of Phytophthora spp. in the decline. A forest in the Natural Park ‘Carrascar de la Font Roja’ in Comunidad Valenciana (eastern Spain), which is dominated by Q. ilex and Q. faginea, was surveyed during 2010–2011. Symptomatic trees showed thinning and dieback of the crown, withering of leaves and death. An extensive loss of both lateral small woody roots and fine roots and callusing or open cankers on suberized roots were observed. Soil samples containing fine roots were baited using both Q. robur leaves and apple fruits. Six Phytophthora species were isolated: P. cryptogea, P. gonapodyides, P. megasperma, P. quercina, P. psychrophila and P. syringae. These are the first records of P. quercina and P. psychrophila on Q. faginea, of P. quercina in Spain and of P. psychrophila in mainland Spain. A soil infestation trial was conducted for 6 months under controlled conditions with 1-year-old seedlings of Q. ilex and Q. faginea. Phytophthora cinnamomi was included in the pathogenicity test for comparison. The results showed that Q. ilex seedlings were generally more susceptible to infection than Q. faginea with P. cinnamomi being the most aggressive pathogen to both oak species. The two most commonly isolated Phytophthora species, P. quercina and P. psychrophila, also proved their pathogenicity towards both Q. ilex and Q. faginea.

Heterobasidion annosum (Fr.) Bref. sensu lato is an important fungal parasite of coniferous trees throughout the temperate regions of the world. Approximately 15% of Heterobasidion isolates are infected by dsRNA viruses, which are considered as obligately intracellular and transmit vertically into both basidiospores and asexual conidia. Insects such as H. abietis and its larvae feeding on wood colonized by Heterobasidion fungi may carry Heterobasidion conidia and hyphae. In this study, we used H. abietis as a model species to reveal whether Heterobasidion viruses resist in their fungal host passing through the digestive tract of insects that may potentially serve as disseminators of fungal propagules. Pinus sylvestris branches were inoculated by three different strains of Heterobasidion parviporum, hosting taxonomically diverse virus species: Heterobasidion RNA virus 2, HetRV4 and HetRV6. Then, the inoculated branches were fed to H. abietis insects, and beetle excrements were investigated for Heterobasidion infections. All the inoculated fungal strains survived passage through the alimentary tract of the insects (survival rate 25–80%). The passage rates of the viruses inside their hosts varied considerably, ranging from 0 to 67%. Two different mycoviruses, HetRV2 and HetRV6, survived the intestinal passage of their fungal host, while the virus species HetRV4 was detected among none of the five H. parviporum isolates retrieved from insect faeces. The relative stability of fungi harbouring viruses suggests that if viruses are to be used for biological control against Heterobasidion species, it is likely that insect feeding does not considerably decrease the virus effect, but might instead enhance short-range dispersal of the viral biocontrol agent.

We surveyed the polypore species associated with living hosts in Argentina. We reviewed the literature on polypores found in Argentina and, in addition with the study of unpublished herbarium material, present a list of 87 species decaying living trees in native forests and introduced plantations. The rot type, host(s), distribution and remarks are presented for each species. Among 87 species found, 71 produce a white rot and 16 a brown rot in wood; 61 species were exclusively found on native hosts and 7 on exotic, cultivated hosts, while 18 were found on both types of substrates; one species, Amylosporus campbellii, was exclusively found associated with grasses. For most cases, there are no pathological studies based on rot measurement and culture isolation to determine incidence and severity of the decay.

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.

The aim of this study was to evaluate the effectiveness of a plant extract obtained from the leaves of coffee plants infected by Hemileia vastatrix (NEFID), different formulations of phosphites and the combination of the extract and phosphites in controlling powdery mildew in eucalyptus mini-stumps, as well as to study the effects on the production of mini-cuttings and their rooting percentage. The experiments were conducted on two eucalyptus hybrids (‘urocam’ and ‘urograndis’) in a clonal garden and greenhouse. First, the NEFID plant extract and phosphites of copper, zinc, potassium and potassium/manganese were evaluated to determine their effectiveness in controlling powdery mildew and their toxic effect on the fungus' morphology. Subsequently, we analysed the direct fungitoxicity, curative efficiency and anti-sporulating action of the NEFID extract and various combinations of phosphites with or without the extract, and we also evaluated their effects on shoot production and rooting in eucalyptus mini-cuttings. The NEFID plant extract and phosphites of Cu, Zn and K/Mn were more effective than the fungicide pyraclostrobin + epoxiconazole in the control of powdery mildew. Potassium phosphite was not effective in controlling the pathogen. Among the tested mixtures, the combination of 50% NEFID plant extract and 50% copper phosphite was the most effective because it exhibited direct toxicity on powdery mildew, a high curative efficiency, anti-sporulating action and no adverse effects on the production of shoots or rooting in eucalyptus mini-cuttings.

Phytophthora cinnamomi is a necrotrophic pathogen of woody perennials and devastates many biomes worldwide. A controlled perlite–hydroponic system with no other hyphae-producing organisms as contaminants present allowed rapid assessment of ten annual and herbaceous perennial plant species most of which have a wide distribution within the jarrah (Eucalyptus marginata) forest in Western Australia where this pathogen has been introduced. As some annuals and herbaceous perennials have recently been reported as symptomatic and asymptomatic hosts, laboratory screening of some of the field-tested annuals and herbaceous perennials and additional species was used to further evaluate their role in the pathogen's disease cycle. Nine of the species challenged with the pathogen were asymptomatic, with none developing root lesions; however, Trachymene pilosa died. The pathogen produced thick-walled chlamydospores and stromata in the asymptomatic roots. Furthermore, haustoria were observed in the roots, indicating that the pathogen was growing as a biotroph in these hosts.

Japanese black pine (Pinus thunbergii) seedlings resistant to pine wood nematode (PWN; Bursaphelenchus xylophilus) are routinely selected in Japanese field inoculation trials. Correlations between morphological factors (such as height, stem diameter at ground level and number of branches on seedlings) and disease resistance were examined to improve the production efficiency of 1-year-old black pine seedlings for inoculation. Family relatedness and environmental conditions strongly affected seedling resistance; accordingly, logistic regression analysis was used to separate effects of these two variables. Height and stem diameter at ground level significantly correlated with disease resistance in seedlings inoculated with PWN. Because (a) interactions between stem diameter at ground level and environmental condition were significant and (b) height did not interact with any other factor, it was concluded that height of 1-year-old Japanese black pine seedlings independently correlated with PWN resistance. Thus, field inoculation tests should use tall seedlings to achieve enhanced survival rates.

Severe dieback symptoms were observed in a 490-ha moist ash (Fraxinus angustifolia) lowland forest stand, comprising trees over 100 years old and in 100 ha of newly planted F. angustifolia near Sinop, in Turkey. Five of the 10 soil samples collected around stem bases of the diseased trees were baited using ash leaves and yielded a Phytophthora sp. This heterothallic species produced non-caducous, non-papillate sporangia in non-sterile soil extract, and fluffy, even growth on corn meal and potato dextrose agars, and suppressed, even growth on grated carrot agar. Isolates were identified as Phytophthora taxon salixsoil based on internal transcribed spacer DNA sequences. This species has been recently redesignated as P. lacustris. Three isolates were found to be pathogenic when inoculated on the stem bases of three-year-old F. angustifolia saplings.

Dutch Elm Disease (DED) is a vascular wilt disease of Ulmus species (elms) incited in North America primarily by the exotic fungus Ophiostoma novo-ulmi. The pathogen is transmitted via root grafts and elm bark beetle vectors, including the native North American elm bark beetle, Hylurgopinus rufipes and the exotic smaller European elm bark beetle, Scolytus multistriatus. The banded elm bark beetle, Scolytus schevyrewi, is an exotic Asian bark beetle that is now apparently the dominant elm bark beetle in the Rocky Mountain region of the USA. It is not known if S. schevyrewi will have an equivalent vector competence or if management recommendations need to be updated. Thus the study objectives were to: (i) determine the type and size of wounds made by adult S. schevyrewi on branches of Ulmus americana and (ii) determine if adult S. schevyrewi can transfer the pathogen to American elms during maturation feeding. To determine the DED vectoring capability of S. schevyrewi, newly emerged adults were infested with spores of Ophiostoma novo-ulmi and then placed with either in-vivo or in-vitro branches of American elm trees. The inoculation of trees via feeding wounds was successful 30% of the time for in-vivo trials and 33% for in-vitro trials. Although the infection rate of DED has declined in Colorado over the past 10 years, the disease is still present in urban elms. While it appears that S. schevyrewi is another vector of the DED pathogens, it appears that S. schevyrewi is no more efficient than S. multistriatus. Thus, management programs that remove elm bark beetle breeding sites, rapidly remove DED-infected elms and include the planting of DED-resistant elms should continue to be effective management tactics.

Despite its importance as one of the most notorious, globally distributed, multihost plant pathogens, knowledge on the survival strategy of Phytophthora cinnamomi in seasonally dry climates is limited. Soil and fine roots were collected from the rhizosphere of severely declining or recently dead specimens of 13 woody species at 11 dieback sites and two dieback spots and from healthy specimens of five woody species at four dieback-free sites in native forests, woodlands and heathlands of the south-west of Western Australia (WA). Phytophthora cinnamomi was recovered from 80.4, 78.1 and 100% of tested soil, fine root and soil–debris slurry samples at the 11 dieback sites, in some cases even after 18-month storage under air-dry conditions, but not from the small dieback spots and the healthy sites. Direct isolations from soil–debris slurry showed that P. cinnamomi colonies exclusively originated from fine roots and root fragments not from free propagules in the soil. Microscopic investigation of P. cinnamomi-infected fine and small woody roots and root fragments demonstrated in 68.8, 81.3 and 93.8% of samples from nine woody species the presence of thick-walled oospores, stromata-like hyphal aggregations and intracellular hyphae encased by lignitubers, respectively, while thin-walled putative chlamydospores were found in only 21.2% of samples from five woody species. These findings were confirmed by microscopic examination of fine roots from artificially inoculated young trees of 10 woody species. It is suggested that (i) the main function of chlamydospores is the survival in moderately dry conditions between consecutive rain events and (ii) selfed oospores, hyphal aggregations, and encased hyphae and vesicles in infected root tissue of both host and non-host species are the major long-term survival propagules of P. cinnamomi during the extremely dry summer conditions in WA.

In managed forests dominated by true fir (Abies) species, stands are often restocked using understory trees retained during timber harvest, making the effects of dwarf mistletoe (Arceuthobium spp.) infestation on small true fir a concern. This study examined the response of small red (A. magnifica) and white (A. concolor) fir and their dwarf mistletoes (A. abietinum f.sp. magnificae and A. abietinum f.sp. concoloris, respectively) to precommercial thinning treatments in fir-dominated stands in the Sierra Nevada Mountains of California. Tree diameters and dwarf mistletoe ratings were monitored from 1981 to 2001, and mortality was observed from 1981 to 2006. Red and white fir survival and radial growth decreased significantly with greater mistletoe ratings and increased with larger diameters and live crown ratios. Thinning significantly increased survival and growth of white, but not red fir. Over the course of the study, mistletoe ratings for both fir species did not change significantly in unthinned stands, but increased in thinned stands. However, while statistically significant, increases in mistletoe ratings in thinned stands were gradual and mistletoe ratings did not statistically differ between treatments 20 years post-thinning. Additionally, thinning did not significantly influence mistletoe spread to uninfected trees, indicating that precommercial thinning in lightly infested red and white fir stands will not likely result in substantial increases in dwarf mistletoe abundance over typical harvesting intervals. Overall, while severe dwarf mistletoe infection ratings reduced tree survival and growth, because ratings remained low, actual losses resulting from mistletoes during this study were minor and will not likely result in substantial economic losses over normal harvesting intervals. This finding indicates that precommercial thinning treatments designed specifically to compensate for mistletoe-associated losses may not be necessary when managing red and white fir for timber production.

Seiridium cardinale is regarded as the most important agent responsible for the disease of cupressaceous hosts referred to as Cypress canker. The fungus was first described in California and is currently reported in all continents. A recent study based on seven SSR loci has suggested that California populations may represent the source of the epidemic in the Mediterranean. In this study, 185 AFLP markers were used on an expanded sample size of 125 isolates to determine whether the Mediterranean population may indeed be derived from the California one and to compare the reproductive modes of populations in the two regions of the world. Additionally, amova, NJ, STRUCTURE, principal component analysis and β-tubulin sequence analyses were employed to infer the presence of genetic structure within and between populations. The distribution of pairwise AFLP similarity coefficients suggests Mediterranean populations are reproducing only clonally, while California populations are reproducing both clonally and sexually. amova indicates Mediterranean and California populations are currently genetically isolated, but NJ and STRUCTURE analyses both suggest ancestral Mediterranean genotypes belong to the California population. No alleles were private to either population, and the presence of identical or quasi-identical genotypes at large distances supports the notion that movement of infected cypress plants is responsible for the global spread of the disease. Surprisingly, STRUCTURE identified a second cluster of Mediterranean genotypes distinct from the basal mixed California–Mediterranean cluster. This second cluster either may have originated from the first one under the selection pressure imposed on the pathogen in the new Mediterranean environments or may be the result of a further introduction from California or elsewhere. Cumulatively, the evidence presented here suggests that S. cardinale may be native or long naturalized in California and that two genetically distinct groups are present in the Mediterranean, with obvious implications for further studies on this disease.

In the Mediterranean area, common cypress (Cupressus sempervirens) has traditionally been used as a multipurpose tree, for its symbolic and ornamental role, for its valuable timber, as well as for windbreaks and soil protection. The epidemic spread of the Seiridium cardinale canker has limited the use of this tree since the 1970s, inducing researchers to develop a breeding programme of cypress aimed at selecting canker-resistant lines for different uses and to support a flourishing trade of cypress plants. ‘Le Crete 1’ and ‘Le Crete 2’ described here are two new canker-resistant C. sempervirens varieties patented in 2010, selected through a 13-year assessment of their response to artificial inoculations and growth traits. Both are characterized by a rapid growth and by a columnar and fastigiated habit that confers them a notable ornamental effect. Preliminary observations showed also that both tend to produce yearly few microsporophylls and little pollen. ‘Le Crete 2’ was also selected for the high growth rate it maintained on heavy, clayey soils.

Cytoskeletal dynamics play a crucial role in pathogen recognition and cell defence during the initial interactions between an invader and plant host. The aim of the work reported here was to characterize how Heterobasidion annosum s.s., Heterobasidion parviporum, and Heterobasidion abietinum affect the microtubules and microfilaments of Pinus sylvestris root cells 12-, 24-, 48-, and 96-h post-inoculation. Inoculation of P. sylvestris with H. parviporum or H. abietinum, which have a lower specificity for P. sylvestris than H. annosum s.s, resulted in greater reorganization of host microtubules during the early stages of interaction than inoculation with the more specific H. annosum s.s. In some infected cells, spots of actin aggregates were observed. Disruption of cytoskeletal components by the application of specific cytoskeletal inhibitors facilitated the entry of the H. parviporum and H. abietinum into roots. These results suggest that the P. sylvestris cytoskeleton plays a role in the host response in the initial stages of the host–pathogen interaction.

Eleven mixed populations of Juniperus oxycedrus L. and Juniperus communis L. were inventoried for the presence of parasitic woody species Arceuthobium oxycedri (DC.) M. Bieb. infections. Both J. oxycedrus and A. oxycedri are rare and distributed in marginal populations in Slovenia. To our knowledge, this is the first detailed research on the host species as well as on the infection and spreading patterns of A. oxycedri in Europe. Assessment of the infection rate was based on the Hawksworth six-class dwarf mistletoe rating system (DMR). The dimensions of A. oxycedri specimens were surprisingly large and often exceeded 25 cm in diameter, the largest even measuring up to 40 cm. Six juniper populations of 11 were infected, and the proportion of infected host individuals in these ranged between 29.17 and 82.93%. The proportion of infected J. oxycedrus specimens in infected populations was 76.56%, while this percentage for J. communis was 54.90%, which is surprisingly high for this species. A different pattern of infection was observed for the two hosts. A typical infection on J. communis was more localized. Usually, only a single infection was present and was most common on the trunk in the middle third of the crown and much less common on the branches. In J. oxycedrus, infections were also most common in the middle third, but also frequent in other areas of the trunk as well as on the branches. Mostly, we observed a dotted pattern of infection with uninfected areas in between. We assume that A. oxycedri will continue to slowly spread in Slovenia, primarily in areas where it is already present. However, its control is probably not yet necessary.

Phytophthora species were surveyed by collecting soil samples and placing bait leaves in selected streams during June–October in the years 2005, 2006 and 2010 at three sites in oak forests in Diqing Tibetan Autonomous Prefecture of NW Yunnan province, China. Seventy-three isolates of Phytophthora spp. were recovered from 135 baited leaf samples and 81 soil samples. Eight Phytophthora species were identified by observation of morphological features and ITS1-5.8S-ITS2 rDNA sequence analysis. The eight taxa included two well-known species P. gonapodyides and P. cryptogea, two recently described species P. gregata and P. plurivora, two named but as yet undescribed taxa, P. taxon PgChlamydo and P. taxon Salixsoil, and two previously unrecognized species, Phytophthora sp.1 and P. sp.2. The most numerous species, P. taxon PgChlamydo, and the second most abundant species, P. taxon Salixsoil, were recovered at all three sites. Phytophthora cryptogea was detected only once at site Nixi. Phytophthora gregata and P. sp.2 were isolated from a stream only at site Bitahai, while the other three species were each found at two sites. Phylogenetic analysis revealed that the isolates belonged to three ITS clades, one species including six isolates in clade 2, six species including 66 isolates in clade 6 and one species in clade 8. There was a relatively rich species and genetic diversity of Phytophthora detected in the investigated regions where the forest biotic and abiotic factors affecting the growth and evolution of Phytophthora populations were diverse.

Pinewood nematode, Bursaphelenchus xylophilus, is an inhabitant of native pine species of North America, where its presence in trees is non-pathogenic. By contrast, the introduction of this nematode to forests overseas has devastated some pine stands and is recognized as a pest of phytosanitary concern by some countries' National Plant Protection Organizations. The ability to detect B. xylophilus in internationally traded wood products is crucial to reduce the spread of this organism. Current molecular techniques for the detection of B. xylophilus rely on the presence of genomic DNA and thus will detect both living and dead nematodes without differentiation. The detection of dead nematodes could lead to unnecessary trade disruption. Therefore, accurate techniques for the detection of and differentiation between live and dead B. xylophilus are critical. We have developed an endpoint RT-PCR assay and a SYBR Green 1 real-time RT-PCR assay, both of which selectively identify living pinewood nematode by detecting the presence of Hsp70 mRNA as a viability marker. Both of these assays may help overcome or resolve disputes involving the detection of pinewood nematode at the port of entry and can also be used to evaluate the efficiency of wood treatment procedures.

A rain shelter experiment was conducted in a 90-year-old Norway spruce stand, in the Kysucké Beskydy Mts (Slovakia). Three rain shelters were constructed in the stand to prevent the rainfall from reaching the soil and to reduce water availability in the rhizosphere. Fine root biomass and necromass were repeatedly measured throughout a growing season by soil coring. We established the quantities of fine root biomass (live) and necromass (dead) at soil depths of 0–5, 5–15, 15–25 and 25–35 cm. Significant differences in soil moisture contents between control and drought plots were found in the top 15 cm of soil after 20 weeks of rainfall manipulation (lasting from early June to late October). Our observations show that even relatively light drought decreased total fine root biomass from 272.0 to 242.8 g m⁻² and increased the amount of necromass from 79.2 to 101.2 g m⁻² in the top 35 cm of soil. Very fine roots (VFR), that is, those with diameter up to 1 mm, were more affected than total fine roots defined as 0–2 mm. The effect of reduced water availability was depth-specific; as a result, we observed a modification of vertical distribution of fine roots. More roots in drought treatment were produced in the wetter soil horizons at 25–35 cm depth than at the surface. We conclude that fine and VFR systems of Norway spruce have the capacity to re-allocate resources to roots at different depths in response to environmental signals, resulting in changes in necromass to biomass ratio.

Chrysoporthe austroafricana is one of the most damaging pathogens of Eucalyptus trees in southern Africa. It also occurs on non-native Tibouchina granulosa trees and native Syzygium species. Additional isolates of the pathogen from previously unstudied countries in the region have become available from survey studies. The aim of this study was to use VCGs to consider the diversity in populations of isolates collected in various countries in southern Africa (Malawi, Mozambique, Namibia, South Africa and Zambia) and from different hosts. We also wanted to determine whether there are shared VCGs among these countries and hosts in southern Africa and establish a VCG tester strain database. Results showed a high diversity amongst isolates from different countries and hosts, but suggested little movement of VCGs among countries or hosts based on the available isolates. A total of 108 VCG tester strains were identified for southern Africa.

Phellinus sensu lato (s.l.) is a complex of segregate genera that act as aggressive pathogens of woody plants. Nearly all of the genera in this complex have unresolved taxonomies, including Porodaedalea, which is one of the most important trunk rot pathogens of coniferous trees throughout the northern hemisphere. In an attempt to elucidate the species within Porodaedalea, a multilocus phylogenetic analysis was performed with partial sequences from four loci (internal transcribed spacer, nuclear large subunit, tef1 and rpb2) using 41 isolates that originated from North America and Europe. For reference, we analysed the neotype isolates of Porodaedalea pini and P. chrysoloma. Our results confirmed that Porodaedalea pini s.s. and P. chrysoloma s.s. are unique phylogenetic species that do not occur in North America. We detected two discrete clades of Porodaedalea originating from the southwestern and southeastern United States. Isolates from these regions grouped with significant statistical support and represent undescribed taxa. With the exception of P. cancriformans, our analyses revealed monophyly among 28 isolates originating from the northern United States, Canada and Fennoscandia, a group we have labelled the ‘Holarctic group’. Holarctic group isolates were collected from Larix, Picea, Pinus, Pseudotsuga and Tsuga and were presumed to represent at least four morphological species (P. gilbertsonii, P. laricis, P. pini s.l. and P. piceina). Tests of gene flow and genetic differentiation detected significant differences among Holarctic group isolates by region of origin, and three subgroups were designated: (i) Atlantic-Boreal; (ii) Interior; and (iii) Pacific. Neutrality tests using the Holarctic group demonstrated significant departures from the standard neutral model of evolution and could indicate that a diversifying selection has maintained rare phenotypes in the population, which has fostered taxonomic confusion in Porodaedalea.

Dauer formation is a mechanism by which nematodes cope with difficult environmental circumstances. DAF-encoding genes are known to control the formation of dauer larvae in several nematode species. In this article, two important daf genes were isolated from the invasive plant parasitic nematode, Bursaphelenchus xylophilus, which has two dauer larval stages for overwintering and transmitting by vector beetles in its life cycle. A 1915-bp full-length cDNA of Bx-daf-9 was obtained, containing a 1533-bp open reading frame (ORF), encoding a polypeptide of 510 amino acids. A 3966-bp full-length cDNA of Bx-daf-12 was obtained, containing a 2712-bp ORF, which encoded a polypeptide of 903 amino acids. The structures of both genes in nematodes were compared. A 2758-bp promoter region of Bx-daf-9 and a 2459-bp promoter region of Bx-daf-12 were obtained, with eight putative response elements binding transcription factors in each promoter region. The quantitative real-time reverse transcription-polymerase chain reaction (RT-qPCR) was performed to detect the mRNA expression levels of the two genes in different stages of the nematode. The result showed that expression levels of the two genes were low in egg stage and up-regulated five to seven times in larval and adult stages. However, Bx-daf-9 expression in the third dispersal stage was relatively low. Expression of daf-12 in the fourth dispersal stage was extraordinarily high. The results imply that daf-9 and daf-12 perhaps have special roles in the dispersal stages of B. xylophilus.

Ceratocystis wilt, caused by Ceratocystis fimbriata, has become the most important disease in eucalyptus (Eucalyptus spp. and hybrids) plantations in Brazil. To further our understanding of the epidemiology of this disease, we surveyed eucalyptus plantations in the states of Minas Gerais and Bahia that were known to have Ceratocystis wilt or were thought to have been planted with infected rooted cuttings. There was generally higher disease incidence in the Minas Gerais plantations, which were on former Cerrado forest sites and likely had soilborne inoculum prior to planting eucalyptus. In such plantations, disease incidence was not evident before 20 months after planting but slowly increased up to 50% at 74 months. The symptomatic and killed trees were aggregated, perhaps from uneven distribution of inoculum in the soil. Also, the progression of cumulative disease incidence best fit a monomolecular model, which is typical of soilborne diseases (fixed level of initial inoculum with little or no secondary inoculum during the crop rotation). However, plots where some trees had been harvested during the rotation showed very high levels of disease incidence in the sprouts that arose from stumps, suggesting secondary spread of the pathogen on harvesting tools or machinery. Most of the Bahia plantations were on pastureland prior to eucalyptus cultivation, and the pathogen was likely introduced with infected nursery stock. In such plots, symptoms were evident as soon as 7 months after planting, and most of the mortality occurred within 12 months. The diseased trees on former pastureland sites were sometimes aggregated within planting rows, suggesting that bunches of infected nursery stock were planted together within the rows. Care should be taken in planting disease-free planting material and spreading the pathogen on tools, but on sites with soilborne inoculum, use of resistant clones may be the only management option.

Between 2008 and 2010, horse chestnut (Aesculus hippocastanum) trees growing at 216 locations in the Czech Republic were surveyed for bleeding canker disease. Typical symptoms of bleeding canker were found at 16 locations, and samples were collected from five of these locations. The bacterium Pseudomonas syringae was isolated from five locations, and Pseudomonas syringae pathovar aesculi, which is the causal agent of bleeding canker disease, was isolated at one location. This is the first report of P. syringae pv. aesculi in the Czech Republic.

Air-dried pseudosclerotia produced by the ash dieback pathogen Hymenoscyphus pseudoalbidus (anamorph: Chalara fraxinea) can survive up to 3 months. Under field conditions, they are capable of postponing fructification for 1 year. The implications of this observation for epidemiology and control of ash dieback are discussed.