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Colony morphology of Phytophthora virginiana isolates 44G6 (top) and 46A2 (bottom) after 10-days growth at 20°C on (left to right) carrot agar, clarified V8 juice agar, malt extract agar and potato dextrose agar.
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Isolates belonging to a previously unknown species of Phytophthora were recovered from irrigation reservoirs at several ornamental plant nurseries in Virginia. Morphological features of this species include abundant lateral chlamydospores in clarified V8 juice agar and carrot agar and terminal, ovoid to obpyriform, nonpapillate and noncaducous spor...
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... growing in the dark at 20°C for 10 days, the colonies of the two P. virginiana isolates were photographed (Fig. 3). The growth patterns of both isolates were similar on each tested medium. On CA, they grew fast and formed radiate colonies with relatively smooth edges, producing abundant aerial mycelia at the center and scattered at the colony intermediate and edge. On CV8A, they formed similar chrysanthemum colony patterns with cotton-like aerial ...
Citations
... Phytophthora virginiana was involved in hybridisation processes resulting in several hybrids with P. virginiana as one parent (Jung et al., 2017a. This species is classified as tolerant to high temperatures (Yang & Hong, 2013) which may provide an advantage for the summer temperatures in Czech Republic. Phytophthora sansomeana was reported previously from Europe in Croatia and Germany (Jung et al., 2016). ...
Phytophthora diversity was examined in eight forest and ornamental nurseries in the Czech Republic. A leaf baiting isolation technique and, in two nurseries, also Illumina DNA metabarcoding were used to reveal the diversity of Phytophthora in soil and irrigation water and compare the efficacy of both approaches. In total, baiting revealed the occurrence of 12 Phytophthora taxa in 59.4% of soil samples
from seven (87.5%) nurseries. Additional baiting of compost was carried out in two nurseries and two Phytophthora species were recovered. Irrigation water was examined in three nurseries by baiting or by direct isolation from partially decomposed floating
leaves collected from the water source, and two Phytophthora
species were obtained. Illumina sequencing of soil and water samples was done in two and one nurseries, respectively. Phytophthora reads were identified as 45 Phytophthora taxa, 15 of them previously unknown taxa from Clades 6, 7, 8 and 9.
Another 11 taxa belonged to known or undescribed species of the oomycete genera Globisporangium, Hyaloperonospora, Nothophytophthora, Peronospora and Plasmopara. Overall, with both techniques 50 Phytophthora taxa were detected with five taxa (P. taxon organica, P. plurivora, P. rosacearum, P. syringae and P. transitoria) being exclusively detected by baiting and 38 only by DNA metabarcoding. Particularly common records in DNA barcoding were P. cinnamomi and P. lateralis which were not isolated by baiting. Only seven species were detected by both techniques. It is recommended to use the combination of both techniques to determine true diversity of Phytophthora in managed or natural ecosystems and reveal the presence of rare or unknown Phytophthora taxa.
... Phytophthora virginiana was involved in hybridisation processes resulting in several hybrids with P. virginiana as one parent (Jung et al., 2017a. This species is classified as tolerant to high temperatures (Yang & Hong, 2013) which may provide an advantage for the summer temperatures in Czech Republic. Phytophthora sansomeana was reported previously from Europe in Croatia and Germany (Jung et al., 2016). ...
Phytophthora diversity was examined in eight forest and ornamental nurseries in the Czech Republic. A leaf baiting isolation technique and, in two nurseries, also Illumina DNA metabarcoding were used to reveal the diversity of Phytophthora in soil and irrigation water and compare the efficacy of both approaches. In total, baiting revealed the occurrence of 12 Phytophthora taxa in 59.4% of soil samples from seven (87.5%) nurseries. Additional baiting of compost was carried out in two nurseries and two Phytophthora species were recovered. Irrigation water was examined in three nurseries by baiting or by direct isolation from partially decomposed floating leaves collected from the water source, and two Phytophthora species were obtained. Illumina sequencing of soil and water samples was done in two and one nurseries, respectively. Phytophthora reads were identified as 45 Phytophthora taxa, 15 of them previously unknown taxa from Clades 6, 7, 8 and 9. Another 11 taxa belonged to known or undescribed species of the oomycete genera Globisporangium , Hyaloperonospora , Nothophytophthora , Peronospora and Plasmopara . Overall, with both techniques 50 Phytophthora taxa were detected with five taxa ( P. taxon organica, P. plurivora, P. rosacearum, P. syringae and P. transitoria ) being exclusively detected by baiting and 38 only by DNA metabarcoding. Particularly common records in DNA barcoding were P. cinnamomi and P. lateralis which were not isolated by baiting. Only seven species were detected by both techniques. It is recommended to use the combination of both techniques to determine true diversity of Phytophthora in managed or natural ecosystems and reveal the presence of rare or unknown Phytophthora taxa.
... Clade 9 is among the most rapidly expanding and dynamic phylogenetic groups of the genus Phytophthora. In addition to previously reported species from the clade such as P. insolita [6], P. macrochlamydospora [7], P. captiosa, P. fallax [8], P. polonica [9], P. irrigate [10] and P. parsiana [11], several new species were described in the last years, including P. hydropathica [12], P. arenaria, P. constricta [13], P. virginiana [14], P. stricta, P. macilentosa [15], P. hydrogena [16] and P. pseudopolonica [17]. The members of clade 9 are characterized by diversity in terms of their origins, and some of them are associated with the decline of host plants, whereas the others have been derived from aquatic ecosystems. ...
... Most of the species in this cluster tolerate temperatures of about 35 °C and demonstrate maximum growth at 40 °C. This group includes P. insolita [6], P. polonica [9], P. irrigata [10], P. hydropathica [12], P. aquimorbida [18], P. virginiana [14], P. macilentosa [15] and P. hydrogena [16]. A relatively small part of the members from the clade 9 have a maximum growth rate of about 30 °C, like P. macrochlamydospora [7], P. constricta [13] and P. captiosa [8]. ...
A number of Phytophthora species have been identified as destructive plant pathogens and invasive species. They have the potential to affect a wide range of host plants and cause diseases in agricultural and forest ecosystems. Two Phytophthora species from rhizosphere soil samples collected from declining Alnus glutinosa in Bulgaria were isolated in the autumn of 2022. They were identified as Phytophthora polonica and Phytophthora hydropathica according to the DNA sequence analysis of the ITS region, as well as their morphological and physiological characteristics. The pathogenicity of both species to common and gray alder was evaluated by the inoculation of detached leaves and cuttings. Experimental data proved that P. polonica and P. hydropathica are able to cause leaf necrosis not only on A. glutinosa from which they were derived, but also on A. incana. No significant deference in the aggressiveness of the studied isolates from both Phytophthora species against the two tested plants was observed. Therefore, P. polonica and P. hydropathica were determined as potential threats for alder ecosystems in the country. This is the first report for the isolation of P. polonica in Bulgaria and represents the most southeastern point of the species distribution in Europe.
... Initially, the classification of Phytophthora species was based on morphological characters (e.g., sporangia, homothallism, and configuration of antheridia), showing the presence of six groups [5]. However, homology and homoplasty among different Phytophthora species showed a high plasticity of the morphological features and their often inseparability [6][7][8][9]. Since the 2000s, the number of described Phytophthora species increased by over 180 species, which was primarily due to the use of novel molecular techniques, reaching a total of 326 species distributed in 12 phylogenetic clades [10]. ...
The genus Phytophthora, with 326 species in 12 phylogenetic clades currently known, includes many economically important pathogens of woody plants. Different Phytophthora species often possess a hemibiotrophic or necrotrophic lifestyle, have either a broad or narrow host range, can cause a variety of disease symptoms (root rot, damping-off, bleeding stem cankers, or blight of foliage), and occur in different growing environments (nurseries, urban and agricultural areas, or forests). Here, we summarize the available knowledge on the occurrence, host range, symptoms of damage, and aggressiveness of different Phytophthora species associated with woody plants in Nordic countries with a special emphasis on Sweden. We evaluate the potential risks of Phytophthora species to different woody plants in this geographical area and emphasize the increasing threats associated with continued introduction of invasive Phytophthora species.
... Many species in Phytophthora major Clades 6 and 9 have largely abandoned sexual reproduction and become functionally sterile, probably during their adaptation to a lifestyle as litter decomposers and opportunistic pathogens in a mainly aquatic environment (Brasier et al. 2003, Jung et al. 2011, Hansen et al. 2012b, Nechwatal et al. 2013, Yang & Hong 2013, Yang et al. 2014). In Clade 10, a parallel development of sterility has probably occurred in the previously described P. gallica and P. intercalaris (Jung & Nechwatal 2008, Yang et al. 2016; and in five of the seven new aquatic Clade 10 species described here, viz. ...
During extensive surveys of global Phytophthora diversity 14 new species detected in natural ecosystems in Chile, Indonesia, USA (Louisiana), Sweden, Ukraine and Vietnam were assigned to Phytophthora major Clade 10 based on a multigene phylogeny of nine nuclear and three mitochondrial gene regions. Clade 10 now comprises three subclades. Subclades 10a and 10b contain species with nonpapillate sporangia, a range of breeding systems and a
mainly soil- and waterborne lifestyle. These include the previously described P. afrocarpa, P. gallica and P. intercalaris and eight of the new species: P. ludoviciana, P. procera, P. pseudogallica, P. scandinavica, P. subarctica, P. tenuimura, P. tonkinensis and P. ukrainensis. In contrast, all species in Subclade 10c have papillate sporangia and are self-fertile (or homothallic) with an aerial lifestyle including the known P. boehmeriae, P. gondwanensis, P. kernoviae and P. morindae and the new species P. celebensis, P. chilensis, P. javanensis, P. multiglobulosa, P. pseudochilensis and P. pseudokernoviae. All new Phytophthora species differed from each other and from related species by their unique combinations of morphological characters, breeding systems, cardinal temperatures and growth rates. The
biogeography and evolutionary history of Clade 10 are discussed. We propose that the three subclades originated via the early divergence of pre-Gondwanan ancestors > 175 Mya into water- and soilborne and aerially dispersed lineages and subsequently underwent multiple allopatric and sympatric radiations during their global spread.
... In other studies in Vietnam and Taiwan, P. virginiana and virginiana-like species were also only detected in rivers and streams (Jung et al., 2020). This species was first recovered from runoff from ornamental plant nurseries in Virginia and is considered nonpathogenic as there no host species are recorded (Yang & Hong, 2014). ...
A study was conducted to determine the pathogens causing root rot, wilt, and dieback disease of Cinnamomum cassia (Chinese cinnamon or cassia) in Vietnam, in nurseries and plantations in the Yen Bai, Quang Ninh, Thanh Hoa and Quang Nam provinces, and streams in the Yen Bai province. Pathogens were identified using morphology and ITS sequence analysis. The 204 isolates obtained included 125 Phytophthora isolates and 79 from other oomycete genera. There were 112 isolates of P. cinnamomi, four P. heveae, two P. virginiana, three P. multibullata and four P. x vanyenensis. The pathogenicity and virulence of 16 P. cinnamomi, two P. heveae, two P. multibullata, and four P. x vanyenensis isolates were assessed using lesion size after under‐bark inoculation of C. cassia stems, and root damage following inoculation of 4‐month‐old C. cassia seedlings. The most virulent isolate from both assessments was a P. cinnamomi from the Quang Nam plantation. Isolates of P. cinnamomi showed a wide range of virulence, with isolates from healthy trees or seedlings showing the lowest virulence. Isolates of P. x vanyenensis, P. multibullata, and P. heveae showed moderate or low pathogenicity. This study showed that although P. cinnamomi is the most common pathogen associated with dieback disease in Vietnamese C. cassia plantations, other Phytophthora species may also cause this disease. Knowledge of the presence of these soil and water borne pathogens will encourage improved soil and water hygiene in nurseries and implement measures to prevent the spread of the pathogens in plantations.
... Grenada 3 (KC479208) by having five instead of one heterozygous position. All isolates of P. sp. ×Grenada 3-like, P. sp. ×kunnunara-like, P. sp. ×Peru 4-like and P. sp. ×virginiana-like were in culture fast-growing, self-sterile and produced intercalary or laterally globose, club-shaped to irregular hyphal swellings, mostly globose thin-walled chlamydospores and nonpapillate sporangia with internal nested and extended proliferation, typical features of aquatic Clade 9 species [56]. ...
In 2016 and 2017, surveys of Phytophthora diversity were performed in 25 natural and semi-natural forest stands and 16 rivers in temperate and subtropical montane and tropical lowland regions of Vietnam. Using baiting assays from soil samples and rivers and direct isolations from naturally fallen leaves, 13 described species, five informally designated taxa and 21 previously unknown taxa of Phytophthora were isolated from 58 of the 91 soil samples (63.7%) taken from the rhizosphere of 52 of the 64 woody plant species sampled (81.3%) in 20 forest stands (83.7%), and from all rivers: P. capensis, P. citricola VII, VIII, IX, X and XI, P. sp. botryosa-like 2, P. sp. meadii-like 1 and 2, P. sp. tropicalis-like 2 and P. sp. multivesiculata-like 1 from Phytophthora major phylogenetic Clade 2; P. castaneae and P. heveae from Clade 5; P. chlamydospora, P. gregata, P. sp. bitahaiensis-like and P. sp. sylvatica-like 1, 2 and 3 from Clade 6; P. cinnamomi (Pc), P. parvispora, P. attenuata, P. sp. attenuata-like 1, 2 and 3 and P. ×heterohybrida from Clade 7; P. drechsleri, P. pseudocryptogea, P. ramorum (Pr) and P. sp. kelmania from Clade 8, P. macrochlamydospora, P. sp. ×insolita-like, P. sp. ×kunnunara-like, P. sp. ×virginiana-like s.l. and three new taxa, P. sp. quininea-like, P. sp. ×Grenada 3-like and P. sp. ×Peru 4-like, from Clade 9; and P. sp. gallica-like 1 and 2 from Clade 10. The A1 and A2 mating types of both Pc and Pr co-occurred. The A2 mating type of Pc was associated with severe dieback of montane forests in northern Vietnam. Most other Phytophthora species, including Pr, were not associated with obvious disease symptoms. It is concluded that (1) Vietnam is within the center of origin of most Phytophthora taxa found including Pc and Pr, and (2) Phytophthora clades 2, 5, 6, 7, 8, 9, and 10 are native to Indochina.
... In clade 9, P. virginiana was obtained at BL by stream baiting in July. It was first isolated from irrigation water at several ornamental nurseries in 2013 in Virginia [60]. No pathogenicity of this species has yet been detected. ...
Phytophthora species are well-known destructive forest pathogens, especially in natural ecosystems. The wild apple (Malus sieversii (Ledeb.) Roem.) is the primary ancestor of M. domestica (Borkh.) and important germplasm resource for apple breeding and improvement. During the period from 2016 to 2018, a survey of Phytophthora diversity was performed at four wild apple forest plots (Xin Yuan (XY), Ba Lian (BL), Ku Erdening (KE), and Jin Qikesai (JQ)) on the northern slopes of Tianshan Mountain in Xinjiang, China. Phytophthora species were isolated from baiting leaves from stream, canopy drip, and soil samples and were identified based on morphological observations and the rDNA internal transcribed spacer (ITS) sequence analysis. This is the first comprehensive study from Xinjiang to examine the Phytophthora communities in wild apple forests The 621 resulting Phytophthora isolates were found to reside in 10 different Phytophthora species: eight known species (P. lacustris being the most frequent, followed by P. gonapodyides, P. plurivora, P. gregata, P. chlamydospora, P. inundata, P. virginiana, and P. cactorum) and two previously unrecognized species (P. sp. CYP74 and P. sp. forestsoil-like). The highest species richness of Phytophthora occurred at BL, followed by XY. P. lacustris was the dominant species at BL, XY, and JQ, while P. gonapodyides was the most common at KE. In the present paper, the possible reasons for their distribution, associated implications, and associated diseases are discussed.
... Three isolates were identified as Phytophthora taxon personii, a species that has yet to be formally described (Burgess et al., 2018). Six isolates with identical DNA sequences (designated as Phytophthora Clade 9 hybrid) were identified as putative hybrids with ITS sequences that had double peaks and sequences of the maternal mitochondrial genes cox1 and cox2 matching several species in Phytophthora Clade 9: P. virginiana, Phytophthora hydropathica, and Phytophthora parsiana (Martin et al., 2014;Yang and Hong, 2013;Yang et al., 2017). Three isolates (designated Phytophthora sp.) were confirmed to be species of Phytophthora by morphology, but these isolates were lost in long-term storage so could not be identified to species. ...
... Of the species of Phytophthora isolated in this study, only P. citrophthora, P. cryptogea, P. drechsleri, and P. nicotianae are well-known pathogens of woody ornamental plants (Erwin and Ribeiro, 1996), and these species accounted for only 8 (36%) of the 22 isolates recovered. The other two species, P. inundata and P. virginiana, and P. taxon personii are relatively young species (i.e., identified for the first time in the past 25 years), typically are found in natural ecosystems or water habits, and are not known to be pathogenic to ornamental plants (Burgess et al., 2018;Yang and Hong, 2013). Likewise, Phytophthora Clade 9 hybrids appear to be related to species typically found in natural ecosystems and not to ones pathogenic to ornamental crops. ...
Constructed wetlands have been used for decades in agricultural settings to remediate nutrients and other agrichemicals from irrigation runoff and drainage; however, little is known about the presence and distribution of Phytophthora species within irrigation runoff water being treated in constructed wetlands. Therefore, we collected plant samples from within vegetated runoff collection channels and treatment stages of two constructed wetland systems receiving irrigation runoff at a commercial plant nursery in Cairo, GA, to determine if roots of wetland plants were infested by species of Phytophthora . Samples were collected 12 times, at 1- to 2-month intervals, over a 19-month period, from Mar. 2011 through Sept. 2012. The sample period covered all four seasons of the year, so we could determine if the association of Phytophthora species with roots of specific plant species varied with season. Approximately 340 samples from 14 wetland plant species were collected, and 22 isolates of Phytophthora species were recovered. Phytophthora species were typically isolated from plants in channels receiving runoff water directly from plant production areas; Phytophthora species were not detected on plants where water leaves the nursery. No seasonal patterns were observed in plant infestation or presence of species of Phytophthora . In fact, Phytophthora species were rarely found to be associated with the roots of the wetland plants collected; species of Phytophthora were found infesting roots of only 6.5% of the 336 plants sampled. Species of Phytophthora were not found to be associated with the roots of golden canna ( Canna flaccida ), lamp rush ( Juncus effusus var. solutus ), duckweed ( Lemna valdiviana ), or sedges ( Carex sp.) during the study period. The exotic invasive plant species marsh dayflower [ Murdannia keisak (33% of samples infested)] and alligatorweed [ Alternanthera philoxeroides (15% of samples infested)] were found to have the first and third highest, respectively, incidences of infestation, with smooth beggartick ( Bidens laevis ) having the second highest incidence of samples infested (22%). Management of invasive species in drainage canals and constructed wetland systems may be critical because of their potential propensity toward infestation by Phytophthora species. Plant species recommended for further investigation for use in constructed wetlands to remediate irrigation runoff include golden canna, marsh pennywort ( Hydrocotyle umbellata ), pickerelweed ( Pontederia cordata ), and broadleaf cattail ( Typha latifolia ). The results from this study provide an important first look at the associations between species of Phytophthora and wetland plants in constructed wetland systems treating irrigation runoff and will serve to further optimize the design of constructed wetlands and other vegetation-based treatment technologies for the removal of plant pathogens from irrigation runoff.
... Some species found in aquatic habitats, especially Phytophthora Clade 6 species, appear to be facultative pathogens or aquatic opportunists that have not been associated with plant disease (Hansen et al. 2012;Jung et al. 2011;Marano et al. 2016;van der Plaats-Niterink 1981). Phytopathogens appear to constitute only a small portion of the total species recovered from streams, rivers, and irrigation water reservoirs (Brazee et al. 2017;Choudhary et al. 2016;Copes et al. 2015;Hong et al. 2012Hong et al. , 2008Loyd et al. 2014;MacDonald et al. 1994;Parke et al. 2014;Yang 2013;Yang and Hong 2013;Yang et al. 2012Yang et al. , 2014Yang et al. , 2016. Genus-level identification of Phytophthora, Pythium, and Phytopythium is therefore insufficient to assess the risks posed to plants. ...
Recycling of irrigation water increases disease risks due to spread of waterborne oomycete plant pathogens such as Phytophthora, Pythium and Phytopythium. A comprehensive metabarcoding study was conducted to determine spatial and temporal dynamics of oomycete communities present in irrigation water collected from a creek (main water source), a pond, retention reservoirs, a chlorinated water reservoir, and runoff channels within a commercial container nursery in Oregon over the course of one year. Two methods, filtration and leaf baiting, were compared for the detection of oomycete communities. Oomycete communities in recycled irrigation water were less diverse but highly enriched with biologically active plant pathogens as compared to the creek water. The filtration method captured a larger portion of oomycete diversity, while leaf baiting was more selective for plant-associated oomycete species of Phytophthora and a few Pythium and Phytopythium species. Seasonality strongly influenced oomycete diversity in irrigation water and detection with leaf baiting. Phytophthora was the major colonizer of leaf baits in winter, while all three genera were equally abundant on leaf baits in summer. The metabarcoding approach was highly effective in studying oomycete ecology, however, it failed to distinguish some closely related species. We developed a custom oomycete ITS1 reference database containing shorter sequences flanked by ITS6 and ITS7 primers used in metabarcoding and used it to assemble a list of indistinguishable species complexes and clusters to improve identification. The predominant bait-colonizing species detected in recycled irrigation water were the Phytophthora citricola-complex, P. syringae, P. parsiana-cluster, P. chlamydospora, P. gonapodyides, P. irrigata, P. taxon Oaksoil-cluster, P. citrophthora-cluster, P. megasperma-cluster, Pythium chondricola-complex, Py. dissotocum-cluster, and Phytopythium litorale.
