SummaryAn analysis of incidence of Phytophthora spp. in 732 European nurseries producing forest transplants, larger specimen trees, landscape plants and ornamentals, plus 2525 areas in which trees and shrubs were planted, is presented based on work conducted by 38 research groups in 23 European countries between 1972 and 2013. Forty-nine Phytophthora taxa were recorded in 670 nurseries (91.5%); within these nurseries, 1614 of 1992 nursery stands (81.0%) were infested, although most affected plants appeared healthy. In forest and landscape plantings, 56 Phytophthora taxa were recovered from 1667 of 2525 tested sites (66.0%). Affected plants frequently showed symptoms such as crown thinning, chlorosis and dieback caused by extensive fine root losses and/or collar rot. Many well-known highly damaging host-Phytophthora combinations were frequently detected but 297 and 407 new Phytophthora-host associations were also observed in nurseries and plantings, respectively. On average, 1.3 Phytophthora species/taxa per infested nursery stand and planting site were isolated. At least 47 of the 68 Phytophthora species/taxa detected in nurseries and plantings were exotic species several of which are considered well established in both nurseries and plantings in Europe. Seven known Phytophthora species/taxa were found for the first For. Path. 46 (2016) 134-163 doi: 10.1111/efp.12239 © 2015 http://wileyonlinelibrary.com/ time in Europe, while 10 taxa had not been previously recorded from nurseries or plantings; in addition, 5 taxa were first detections on woody plant species. Seven Phytophthora taxa were previously unknown to science. The reasons for these failures of plant biosecurity in Europe, implications for forest and semi-natural ecosystems and possible ways to improve biosecurity are discussed.

Most members of the oomycete genus Phytophthora are primary plant pathogens. Both soil- and airborne Phytophthora species are able to survive adverse environmental conditions with enduring resting structures, mainly sexual oospores, vegetative chlamydospores and hyphal aggregations. Soilborne Phytophthora species infect fine roots and the bark of suberized roots and the collar region with motile biflagellate zoospores released from sporangia during wet soil conditions. Airborne Phytophthora species infect leaves, shoots, fruits and bark of branches and stems with caducous sporangia produced during humid conditions on infected plant tissues and dispersed by rain and wind splash. During the past six decades, the number of previously unknown Phytophthora declines and diebacks of natural and semi-natural forests and woodlands has increased exponentially, and the vast majority of them are driven by introduced invasive Phytophthora species. Nurseries in Europe, North America and Australia show high infestation rates with a wide range of mostly exotic Phytophthora species. Planting of infested nursery stock has proven to be the main pathway of Phytophthora species between and within continents. This review provides insights into the history, distribution, aetiology, symptomatology, dynamics and impact of the most important canker, decline and dieback diseases caused by soil- and airborne Phytophthora species in forests and natural ecosystems of Europe, Australia and the Americas.

Severe decline of almond trees has recently been observed in several orchards on the island of Mallorca (Balearic Islands, western Mediterranean Sea). However, the identity of the causal agents has not yet been investigated. Between August 2008 and June 2010, wood samples from branches of almond trees showing internal necroses and brown to black vascular streaking were collected in the Llevant region on the island of Mallorca. Several fungal species were subsequently isolated from the margin between healthy and symptomatic tissue. Five species of Botryosphaeriaceae (namely Botryosphaeria dothidea, Diplodia olivarum, D. seriata, Neofusicoccum australe and N. parvum), Eutypa lata, Phaeoacremonium iranianum and Phomopsis amygdali were identified based on morphology, culture characteristics and DNA sequence comparisons. Neofusicoccum parvum was the dominant species, followed by E. lata, D. olivarum and N. australe. First reports from almond include D. olivarum and Pm. iranianum. Two species are newly described, namely Collophora hispanica sp. nov. and Phaeoacremonium amygdalinum sp. nov.

In 2013 a survey of Phytophthora diversity was performed in 25 natural and semi-natural forest stands and 25 rivers in temperate montane and subtropical lowland regions of Taiwan. Using baiting assays, ten described species and 17 previously unknown taxa of Phytophthora were isolated from 71.5% of the 144 rhizosphere soil samples from 33 of 40 tree species sampled in 24 forest stands ,and from 19 rivers: P. capensis, P. citrophthora, P. plurivora, P. tropicalis, P.citricola VII, P. sp. x botryosa-like, P. sp. x meadii-like and P. sp. occultans-like from Clade 2; P. palmivora from Clade 4; P. castaneae and P. heveae from Clade 5; P. chlamydospora and P. sp.forestsoil-like from Clade 6; P. cinnamomi (Pc), P. parvispora, P. attenuata nom. prov., P. flexuosa nom. prov., P. formosa nom. prov., P. intricata nom. prov., P. x incrassata nom. prov. and P. x heterohybrida nom. prov. from Clade 7; P. sp. palustris and five new hybrid species from Clade 9.The A1 mating type of Pc was widespread in both montane and lowland forests and rarely associated with disease, whereas the A2 mating type was limited to lowland forests and in some cases causing severe dieback. Most other Phytophthora species were not associated with obvious disease symptoms. It is concluded that (1) Taiwan is within the center of origin of most Phytophthora taxa found, (2) PcA2 is an introduced invasive pathogen, and (3) interspecific hybridisations play a major role in speciation and species radiations in diverse natural ecosystems.

During a survey of Phytophthora diversity in natural ecosystems in Taiwan six new species were detected. Multigene phylogeny based on the nuclear ITS, ß-tubulin and HSP90 and the mitochondrial cox1 and NADH1 gene sequences demonstrated that they belong to ITS Clade 7a with P. europaea, P. uniformis, P. rubi and P. cambivora being their closest relatives. All six new species differed from each other and from related species by a unique combination of morphological characters, the breeding system, cardinal temperatures and growth rates. Four homothallic species, P. attenuata, P. flexuosa, P. formosa and P. intricata, were isolated from rhizosphere soil of healthy forests of Fagus hayatae, Quercus glandulifera, Q. tarokoensis, Castanopsis carlesii, Chamaecyparis formosensis and Araucaria cunninghamii. Two heterothallic species, P. xheterohybrida and P. xincrassata, were exclusively detected in three forest streams. All P. xincrassata isolates belonged to the A2 mating type while isolates of P. xheterohybrida represented both mating types with oospore abortion rates according to Mendelian ratios (4–33 %). Multiple heterozygous positions in their ITS, ß-tubulin and HSP90 gene sequences indicate that P. xheterohybrida, P. xincrassata and P. cambivora are interspecific hybrids. Consequently, P. cambivora is re-described as P. xcambivora without nomenclatural act. Pathogenicity trials on seedlings of Castanea sativa, Fagus sylvatica and Q. suber indicate that all six new species might pose a potential threat to European forests.

Fusarium circinatum is thought to have been moved around the world with pine planting stock consisting, most probably, of infected seed. In this effort, we investigate the genetic structure of F. circinatum in Spain and globally. In total, 223 isolates were studied from five regions in northern Spain and eight countries. Eight microsatellite markers revealed 66 multilocus genotypes (MLGs). Minimum spanning network analysis of MLGs by region within Spain as well as globally, discriminant analysis of principal components, and analysis of molecular variance revealed that Spanish populations are significantly differentiated and structured into two distinct groups, each one including one of the dominant genotypes observed. This result suggests that two independent introductions occurred into Spain that subsequently underwent clonal divergence and admixture. This result is further supported by the linkage disequilibrium and clonality observed for F. circinatum populations in northern Spain. The maintenance of differentiation between the clusters could result from the lack of or rare sexual reproduction in Spain. Possible introduction pathways from other countries and subsequent routes of dispersion of F. circinatum in Spain are discussed.

During the winter of 2003-2004, dieback symptoms were observed on Pinus radiata and P. pinaster in pine nurseries in Asturias (northern Spain). Small groups of affected seedlings appeared randomly distributed throughout the nurseries. The seedlings died rapidly, showing basal needle dieback, stem lesions, resin exudations, and wilting. Isolations from infected material onto potato dextrose agar (PDA) supplemented with 0.5 mg/ml of streptomycin sulfate and Komada's medium consistently yielded Fusarium sp. cultures. The isolates were transferred to PDA and Spezieller Nährstoffarmer agar and incubated at 25°C for 10 days with a 12-h photoperiod. The cultures were identified as Fusarium circinatum Nirenberg & O'Donnell (= Fusarium subglutinans Wollenweb. & Reinking), causal agent of pitch canker disease, on basis of the presence of polyphialides and characteristic sterile, coiled, hyphae (2). To further confirm their identity, a polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) based on histone H3 gene sequences (4) and a test based on the F. circinatum-specific primers, CIRC1A-CIRC4A, which amplifies a 360-bp DNA fragment of the intergenic spacer region of the nuclear ribosomal operon (3), were used. Results obtained with both techniques confirmed the morphological identification of the cultures. A representative culture has been placed in the Centraalbureau voor Schimmelcultures (CBS 117843). The pathogen was isolated only from seedlings of P. radiata and P. pinaster. Other species such as P. nigra, P. sylvestris, and Pseudotsuga menziesii, which were also grown in these nurseries, did not show symptoms. Pathogenicity was confirmed by inoculating 6- to 9-month-old P. radiata and P. pinaster seedlings. Small strips of bark (10 × 1 mm) were cut from the stems and similar sized pieces of PDA colonized by F. circinatum were placed in contact with the open wounds and covered with parafilm. Basal needle dieback was observed 10 days after inoculation that resulted in wilting of the seedlings. F. circinatum was reisolated from the affected stems fulfilling Koch's postulates. Later in the year, symptoms of pitch canker were also observed on 20-year-old P. radiata in one forest plantation in Cantabria (northern Spain). Infected branches and shoots of the trees exudated abundant resin, resulting in resinous cankers. The needles, distal to branch tip infections, wilt, fade to yellow then red, and fall from the tree. Affected trees showed noticeable crown dieback. The isolations from the cankers also yielded F. circinatum cultures that were identified as described above. Although a nonrefereed report appeared in 1998 (1), to our knowledge, this is the first report of F. circinatum on P. radiata and P. pinaster in Spain and in Europe. References: (1) L. D. Dwinell et al. Int. Congr. Plant Pathol. 7th. 3:9, 1998. (2) H. I. Nirenberg and K. O'Donnell. Mycologia 90:434, 1998. (3) W. Schweigkofler et al. Appl. Environ. Microbiol. 70:3512, 2004. (4) E. T. Steenkamp et al. Appl. Environ. Microbiol. 65:3401, 1999.

Phytophthora is one of the most important and aggressive plant pathogenic genera in agriculture and forestry. Early detection and identification of its pathways of infection and spread are of high importance to minimize the threat they pose to natural ecosystems. eDNA was extracted from soil and water from forests and plantations in the north of Spain. Phytophthora-specific primers were adapted for use in high-throughput Sequencing (HTS). Primers were tested in a control reaction containing eight Phytophthora species and applied to water and soil eDNA samples from northern Spain. Different score coverage threshold values were tested for optimal Phytophthora species separation in a custom-curated database and in the control reaction. Clustering at 99% was the optimal criteria to separate most of the Phytophthora species. Multiple Molecular Operational Taxonomic Units (MOTUs) corresponding to 36 distinct Phytophthora species were amplified in the environmental samples. Pyrosequencing of amplicons from soil samples revealed low Phytophthora diversity (13 species) in comparison with the 35 species detected in water samples. Thirteen of the MOTUs detected in rivers and streams showed no close match to sequences in international sequence databases, revealing that eDNA pyrosequencing is a useful strategy to assess Phytophthora species diversity in natural ecosystems.