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Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions
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Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions

A special issue of Journal of Fungi (ISSN 2309-608X). This special issue belongs to the section "Fungal Evolution, Biodiversity and Systematics".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 51277

Special Issue Editors

Dr. Thomas Jung

E-Mail Website
Guest Editor
Phytophthora Research Centre, Mendel University, 613 00 Brno, Czech Republic
Interests: diversity, biogeography, ecology, pathology and evolution of Phytophthora species; their impacts on natural and semi-natural ecosystems; their pathways and possible management and control options for Phytophthora diseases
Special Issues, Collections and Topics in MDPI journals
Dr. Bruno Scanu

E-Mail Website
Guest Editor
Dipartimento di Agraria, Sezione di Patologia Vegetale ed Entomologia, Università degli Studi di Sassari, 07100 Sassari, Italy
Interests: forest pathology; diversity, biology and taxonomy of fungal pathogens and oomycetes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fungal-like oomycetes from the kingdom Stramenipila are diverse saprotrophs, necrotrophic, hemibiotrophic, or obligate biotrophic pathogens of a wide range of plant species or, in rare cases, parasites of animals in both aquatic and terrestrial environments. They have water-, soil-, or airborne lifestyles and homothallic, heterothallic, or sterile breeding strategies. Due to the continuously increasing emergence of new pathogens in both managed and natural ecosystems and the advances in molecular methods, the systematic and our understanding of oomycetes has considerably changed during the past decade. It is estimated that only 10% of oomycete species are known to date, and their true diversity and roles in natural and, in particular, in marine environments are still a conundrum. This Special Issue aims to bring together a collection of papers focusing on the diversity, taxonomy, evolution, ecology, epidemiology, host–pathogen interactions, new detection methods and control strategies of oomycetes, with special emphasis on Phytophthora species and related genera in the Peronosporaceae family, such as Halophytophthora (sensu latu), Nothophytophthora, Phytopythium, and downy mildews. Review articles are also welcome, but please contact the Guest Editors before submission.

Dr. Thomas Jung
Dr. Bruno Scanu
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Journal of Fungi is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Phytophthora
  • Halophytophthora
  • downy mildews
  • epidemic
  • invasive pathogens

Published Papers (16 papers)

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Research

28 pages, 16180 KiB  
Article
Natural Populations from the Phytophthora palustris Complex Show a High Diversity and Abundance of ssRNA and dsRNA Viruses
by Leticia Botella, Marília Horta Jung, Michael Rost and Thomas Jung
J. Fungi 2022, 8(11), 1118; https://0-doi-org.brum.beds.ac.uk/10.3390/jof8111118 - 24 Oct 2022
Cited by 5 | Viewed by 3403
Abstract
We explored the virome of the “Phytophthora palustris complex”, a group of aquatic specialists geographically limited to Southeast and East Asia, the native origin of many destructive invasive forest Phytophthora spp. Based on high-throughput sequencing (RNAseq) of 112 isolates of “P. [...] Read more.
We explored the virome of the “Phytophthora palustris complex”, a group of aquatic specialists geographically limited to Southeast and East Asia, the native origin of many destructive invasive forest Phytophthora spp. Based on high-throughput sequencing (RNAseq) of 112 isolates of “P. palustris” collected from rivers, mangroves, and ponds, and natural forests in subtropical and tropical areas in Indonesia, Taiwan, and Japan, 52 putative viruses were identified, which, to varying degrees, were phylogenetically related to the families Botybirnaviridae, Narnaviridae, Tombusviridae, and Totiviridae, and the order Bunyavirales. The prevalence of all viruses in their hosts was investigated and confirmed by RT-PCR. The rich virus composition, high abundance, and distribution discovered in our study indicate that viruses are naturally infecting taxa from the “P. palustris complex” in their natural niche, and that they are predominant members of the host cellular environment. Certain Indonesian localities are the viruses’ hotspots and particular “P. palustris” isolates show complex multiviral infections. This study defines the first bi-segmented bunya-like virus together with the first tombus-like and botybirna-like viruses in the genus Phytophthora and provides insights into the spread and evolution of RNA viruses in the natural populations of an oomycete species. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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17 pages, 1768 KiB  
Article
Spatial Genetic Structure and Pathogenic Race Composition at the Field Scale in the Sunflower Downy Mildew Pathogen, Plasmopara halstedii
by Abdelhameed Elameen, Denis Tourvieille de Labrouhe, Emmanuelle Bret-Mestries and Francois Delmotte
J. Fungi 2022, 8(10), 1084; https://0-doi-org.brum.beds.ac.uk/10.3390/jof8101084 - 14 Oct 2022
Cited by 1 | Viewed by 1382
Abstract
Yield losses in sunflower crops caused by Plasmopara halstedii can be up to 100%, depending on the cultivar susceptibility, environmental conditions, and virulence of the pathogen population. The aim of this study was to investigate the genetic and phenotypic structure of a sunflower [...] Read more.
Yield losses in sunflower crops caused by Plasmopara halstedii can be up to 100%, depending on the cultivar susceptibility, environmental conditions, and virulence of the pathogen population. The aim of this study was to investigate the genetic and phenotypic structure of a sunflower downy mildew agent at the field scale. The genetic diversity of 250 P. halstedii isolates collected from one field in southern France was assessed using single-nucleotide polymorphisms (SNPs) and single sequence repeats (SSR). A total of 109 multilocus genotypes (MLG) were identified among the 250 isolates collected in the field. Four genotypes were repeated more than 20 times and spatially spread over the field. Estimates of genetic relationships among P. halstedii isolates using principal component analysis and a Bayesian clustering approach demonstrated that the isolates are grouped into two main genetic clusters. A high level of genetic differentiation among clusters was detected (FST = 0.35), indicating overall limited exchange between them, but our results also suggest that recombination between individuals of these groups is not rare. Genetic clusters were highly related to pathotypes, as previously described for this pathogen species. Eight different races were identified (100, 300, 304, 307, 703, 704, 707, and 714), with race 304 being predominant and present at most of the sites. The co-existence of multiple races at the field level is a new finding that could have important implications for the management of sunflower downy mildew. These data provide the first population-wide picture of the genetic structure of P. halstedii at a fine spatial scale. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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17 pages, 1925 KiB  
Article
Elevating Air Temperature May Enhance Future Epidemic Risk of the Plant Pathogen Phytophthora infestans
by E-Jiao Wu, Yan-Ping Wang, Li-Na Yang, Mi-Zhen Zhao and Jiasui Zhan
J. Fungi 2022, 8(8), 808; https://0-doi-org.brum.beds.ac.uk/10.3390/jof8080808 - 30 Jul 2022
Cited by 6 | Viewed by 1773
Abstract
Knowledge of pathogen adaptation to global warming is important for predicting future disease epidemics and food production in agricultural ecosystems; however, the patterns and mechanisms of such adaptation in many plant pathogens are poorly understood. Here, population genetics combined with physiological assays and [...] Read more.
Knowledge of pathogen adaptation to global warming is important for predicting future disease epidemics and food production in agricultural ecosystems; however, the patterns and mechanisms of such adaptation in many plant pathogens are poorly understood. Here, population genetics combined with physiological assays and common garden experiments were used to analyze the genetics, physiology, and thermal preference of pathogen aggressiveness in an evolutionary context using 140 Phytophthora infestans genotypes under five temperature regimes. Pathogens originating from warmer regions were more thermophilic and had a broader thermal niche than those from cooler regions. Phenotypic plasticity contributed ~10-fold more than heritability measured by genetic variance. Further, experimental temperatures altered the expression of genetic variation and the association of pathogen aggressiveness with the local temperature. Increasing experimental temperature enhanced the variation in aggressiveness. At low experimental temperatures, pathogens from warmer places produced less disease than those from cooler places; however, this pattern was reversed at higher experimental temperatures. These results suggest that geographic variation in the thermal preferences of pathogens should be included in modeling future disease epidemics in agricultural ecosystems in response to global warming, and greater attention should be paid to preventing the movement of pathogens from warmer to cooler places. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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9 pages, 519 KiB  
Article
Sexual Compatibility Types in F1 Progenies of Sclerospora graminicola, the Causal Agent of Pearl Millet Downy Mildew
by Chandramani Raj and Rajan Sharma
J. Fungi 2022, 8(6), 629; https://0-doi-org.brum.beds.ac.uk/10.3390/jof8060629 - 13 Jun 2022
Viewed by 1505
Abstract
Sclerospora graminicola is primarily heterothallic in nature with two distinct mating types (G1 and G2); however, homothallism does exist in the pathogen populations. In this study, a cross was made between two self-sterile isolates (Sg 019, Mat-2, G2 [...] Read more.
Sclerospora graminicola is primarily heterothallic in nature with two distinct mating types (G1 and G2); however, homothallism does exist in the pathogen populations. In this study, a cross was made between two self-sterile isolates (Sg 019, Mat-2, G2 × Sg 445-1, Mat-1, G1) of S. graminicola and a total of 39 F1 progenies were established. The study on sexual compatibility types in F1 progenies was conducted by crossing each F1 progeny with both the parents (Sg 445-1, Mat-1, G1; and Sg 019, Mat-2, G2). The results revealed the presence of four sexual compatibility types, viz. G1, G2, G1G2 and G0 (neuter) in the progenies. The G1G2 progenies that produced oospores with both the parents were found as self-fertile (homothallic) and self-sterile (heterothallic) types. Similarly, self-fertile parental type G1 and G2 progenies were designated as secondary homothallic, whereas self-sterile parental type G1 and G2 progenies were of heterothallic type. The result of the present study revealed Mendelian segregation of mating type locus in S. graminicola which indicates that sexual reproduction plays an important role in the evolution of new genetic recombinants in the pathogen. The study also helps in understanding the genetic structure of S. graminicola populations and potential for possible evolution of new virulences in the pathogen. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
18 pages, 4502 KiB  
Article
A Barcode-Based Phylogenetic Characterization of Phytophthora cactorum Identifies Two Cosmopolitan Lineages with Distinct Host Affinities and the First Report of Phytophthora pseudotsugae in California
by Tyler B. Bourret, Sebastian N. Fajardo, Cole P. Engert and David M. Rizzo
J. Fungi 2022, 8(3), 303; https://0-doi-org.brum.beds.ac.uk/10.3390/jof8030303 - 16 Mar 2022
Cited by 7 | Viewed by 2466
Abstract
A collection of 30 Phytophthora cactorum and 12 P. pseudotsugae (subclade 1a) strains isolated from several recent surveys across California was phylogenetically compared to a worldwide collection of 112 conspecific strains using sequences from three barcoding loci. The surveys baited P. cactorum from [...] Read more.
A collection of 30 Phytophthora cactorum and 12 P. pseudotsugae (subclade 1a) strains isolated from several recent surveys across California was phylogenetically compared to a worldwide collection of 112 conspecific strains using sequences from three barcoding loci. The surveys baited P. cactorum from soil and water across a wide variety of forested ecosystems with a geographic range of more than 1000 km. Two cosmopolitan lineages were identified within the widespread P. cactorum, one being mainly associated with strawberry production and the other more closely associated with apple orchards, oaks and ornamental trees. Two other well-sampled P. cactorum lineages, including one that dominated Californian restoration outplantings, were only found in the western United States, while a third was only found in Japan. Coastal California forest isolates of both Phytophthora species exhibited considerable diversity, suggesting both may be indigenous to the state. Many isolates with sequence accessions deposited as P. cactorum were determined to be P. hedraiandra and P. ×serendipita, with one hybrid lineage appearing relatively common across Europe and Asia. This study contains the first report of P. pseudotsugae from the state of California and one of the only reports of that species since its original description. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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24 pages, 9296 KiB  
Article
Metabolomic and Physiological Changes in Fagus sylvatica Seedlings Infected with Phytophthora plurivora and the A1 and A2 Mating Types of P. ×cambivora
by Tamara Corcobado, Ivan Milenković, Iñigo Saiz-Fernández, Tomáš Kudláček, Roman Plichta, Tomáš Májek, Aneta Bačová, Henrieta Ďatková, László Benedek Dálya, Miloš Trifković, Davide Mureddu, Vladimír Račko, Monika Kardošová, Jaroslav Ďurkovič, Roman Rattunde and Thomas Jung
J. Fungi 2022, 8(3), 298; https://0-doi-org.brum.beds.ac.uk/10.3390/jof8030298 - 14 Mar 2022
Cited by 3 | Viewed by 2993
Abstract
Phytophthora infections are followed by histological alterations, physiological and metabolomic adjustments in the host but very few studies contemplate these changes simultaneously. Fagus sylvatica seedlings were inoculated with A1 and A2 mating types of the heterothallic P. ×cambivora and with the homothallic P. [...] Read more.
Phytophthora infections are followed by histological alterations, physiological and metabolomic adjustments in the host but very few studies contemplate these changes simultaneously. Fagus sylvatica seedlings were inoculated with A1 and A2 mating types of the heterothallic P. ×cambivora and with the homothallic P. plurivora to identify plant physiological and metabolomic changes accompanying microscope observations of the colonization process one, two and three weeks after inoculation. Phytophthora plurivora-infected plants died at a faster pace than those inoculated with P. ×cambivora and showed higher mortality than P. ×cambivora A1-infected plants. Phytophthora ×cambivora A1 and A2 caused similar progression and total rate of mortality. Most differences in the physiological parameters between inoculated and non-inoculated plants were detected two weeks after inoculation. Alterations in primary and secondary metabolites in roots and leaves were demonstrated for all the inoculated plants two and three weeks after inoculation. The results indicate that P. plurivora is more aggressive to Fagus sylvatica seedlings than both mating types of P. ×cambivora while P. ×cambivora A1 showed a slower infection mode than P. ×cambivora A2 and led to minor plant metabolomic adjustments. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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17 pages, 4881 KiB  
Article
Effects of Phytophthora Inoculations on Photosynthetic Behaviour and Induced Defence Responses of Plant Volatiles in Field-Grown Hybrid Poplar Tolerant to Bark Canker Disease
by Jaroslav Ďurkovič, Tatiana Bubeníková, Adriána Gužmerová, Peter Fleischer, Daniel Kurjak, Ingrid Čaňová, Ivan Lukáčik, Miloň Dvořák and Ivan Milenković
J. Fungi 2021, 7(11), 969; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7110969 - 15 Nov 2021
Cited by 3 | Viewed by 2010
Abstract
Bark cankers accompanied by symptoms of decline and dieback are the result of a destructive disease caused by Phytophthora infections in woody plants. Pathogenicity, gas exchange, chlorophyll a fluorescence, and volatile responses to P. cactorum and P. plurivora inoculations were studied in field-grown [...] Read more.
Bark cankers accompanied by symptoms of decline and dieback are the result of a destructive disease caused by Phytophthora infections in woody plants. Pathogenicity, gas exchange, chlorophyll a fluorescence, and volatile responses to P. cactorum and P. plurivora inoculations were studied in field-grown 10-year-old hybrid poplar plants. The most stressful effects of P. cactorum on photosynthetic behaviour were found at days 30 and 38 post-inoculation (p.-i.), whereas major disturbances induced by P. plurivora were identified at day 30 p.-i. and also belatedly at day 52 p.-i. The spectrum of volatile organic compounds emitted at day 98 p.-i. was richer than that at day 9 p.-i, and the emissions of both sesquiterpenes α-cubebene and germacrene D were induced solely by the Phytophthora inoculations. Significant positive relationships were found between both the axial and the tangential development of bark cankers and the emissions of α-cubebene and β-caryophyllene, respectively. These results show that both α-cubebene and germacrene D are signal molecules for the suppression of Phytophthora hyphae spread from necrotic sites of the bark to healthy living tissues. Four years following inoculations, for the majority of the inoculated plants, the callus tissue had already closed over the bark cankers. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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22 pages, 5289 KiB  
Article
Phylogenetic and Functional Diversity of Saprolegniales and Fungi Isolated from Temperate Lakes in Northeast Germany
by Hossein Masigol, Jason Nicholas Woodhouse, Pieter van West, Reza Mostowfizadeh-Ghalamfarsa, Keilor Rojas-Jimenez, Tobias Goldhammer, Seyed Akbar Khodaparast and Hans-Peter Grossart
J. Fungi 2021, 7(11), 968; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7110968 - 13 Nov 2021
Cited by 5 | Viewed by 2670
Abstract
The contribution of fungi to the degradation of plant litter and transformation of dissolved organic matter (humic substances, in particular) in freshwater ecosystems has received increasing attention recently. However, the role of Saprolegniales as one of the most common eukaryotic organisms is rarely [...] Read more.
The contribution of fungi to the degradation of plant litter and transformation of dissolved organic matter (humic substances, in particular) in freshwater ecosystems has received increasing attention recently. However, the role of Saprolegniales as one of the most common eukaryotic organisms is rarely studied. In this study, we isolated and phylogenetically placed 51 fungal and 62 Saprolegniales strains from 12 German lakes. We studied the cellulo-, lignino-, and chitinolytic activity of the strains using plate assays. Furthermore, we determined the capacity of 10 selected strains to utilize 95 different labile compounds, using Biolog FF MicroPlates™. Finally, the ability of three selected strains to utilize maltose and degrade/produce humic substances was measured. Cladosporium and Penicillium were amongst the most prevalent fungal strains, while Saprolegnia, Achlya, and Leptolegnia were the most frequent Saprolegniales strains. Although the isolated strains assigned to genera were phylogenetically similar, their enzymatic activity and physiological profiling were quite diverse. Our results indicate that Saprolegniales, in contrast to fungi, lack ligninolytic activity and are not involved in the production/transformation of humic substances. We hypothesize that Saprolegniales and fungi might have complementary roles in interacting with dissolved organic matter, which has ecological implications for carbon cycling in freshwater ecosystems. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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20 pages, 9102 KiB  
Article
Phytophthora heterospora sp. nov., a New Pseudoconidia-Producing Sister Species of P. palmivora
by Bruno Scanu, Thomas Jung, Hossein Masigol, Benedetto Teodoro Linaldeddu, Marília Horta Jung, Andrea Brandano, Reza Mostowfizadeh-Ghalamfarsa, Josef Janoušek, Mario Riolo and Santa Olga Cacciola
J. Fungi 2021, 7(10), 870; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7100870 - 16 Oct 2021
Cited by 16 | Viewed by 5778
Abstract
Since 1999, an unusual Phytophthora species has repeatedly been found associated with stem lesions and root and collar rot on young olive trees in Southern Italy. In all cases, this species was obtained from recently established commercial plantations or from nursery plants. Morphologically, [...] Read more.
Since 1999, an unusual Phytophthora species has repeatedly been found associated with stem lesions and root and collar rot on young olive trees in Southern Italy. In all cases, this species was obtained from recently established commercial plantations or from nursery plants. Morphologically, the Phytophthora isolates were characterized by the abundant production of caducous non-papillate conidia-like sporangia (pseudoconidia) and caducous papillate sporangia with a short pedicel, resembling P. palmivora var. heterocystica. Additional isolates with similar features were obtained from nursery plants of Ziziphus spina-christi in Iran, Juniperus oxycedrus and Capparis spinosa in Italy, and mature trees in commercial farms of Durio zibethinus in Vietnam. In this study, morphology, breeding system and growth characteristics of these Phytophthora isolates with peculiar features were examined, and combined mitochondrial and nuclear multigene phylogenetic analyses were performed. The proportion between pseudoconidia and sporangia varied amongst isolates and depended on the availability of free water. Oogonia with amphigynous antheridia and aplerotic oospores were produced in dual cultures with an A2 mating type strain of P. palmivora, indicating all isolates were A1 mating type. Phylogenetically, these isolates grouped in a distinct well-supported clade sister to P. palmivora; thus, they constitute a separate taxon. The new species, described here as Phytophthora heterospora sp. nov., proved to be highly pathogenic to both olive and durian plants in stem inoculation tests. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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19 pages, 4485 KiB  
Article
Assessment of the Spatial Distribution and Risk Associated with Fruit Rot Disease in Areca catechu L.
by Patil Balanagouda, Shankarappa Sridhara, Sandip Shil, Vinayaka Hegde, Manjunatha K. Naik, Hanumappa Narayanaswamy and Siva K. Balasundram
J. Fungi 2021, 7(10), 797; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7100797 - 24 Sep 2021
Cited by 12 | Viewed by 2399
Abstract
Phytophthora meadii (McRae) is a hemibiotrophic oomycete fungus that infects tender nuts, growing buds, and crown regions, resulting in fruit, bud, and crown rot diseases in arecanut (Areca catechu L.), respectively. Among them, fruit rot disease (FRD) causes serious economic losses that [...] Read more.
Phytophthora meadii (McRae) is a hemibiotrophic oomycete fungus that infects tender nuts, growing buds, and crown regions, resulting in fruit, bud, and crown rot diseases in arecanut (Areca catechu L.), respectively. Among them, fruit rot disease (FRD) causes serious economic losses that are borne by the growers, making it the greatest yield-limiting factor in arecanut crops. FRD has been known to occur in traditional growing areas since 1910, particularly in Malnad and coastal tracts of Karnataka. Systemic surveys were conducted on the disease several decades ago. The design of appropriate management approaches to curtail the impacts of the disease requires information on the spatial distribution of the risks posed by the disease. In this study, we used exploratory survey data to determine areas that are most at risk. Point pattern (spatial autocorrelation and Ripley’s K function) analyses confirmed the existence of moderate clustering across sampling points and optimized hotspots of FRD were determined. Geospatial techniques such as inverse distance weighting (IDW), ordinary kriging (OK), and indicator kriging (IK) were performed to predict the percent severity rates at unsampled sites. IDW and OK generated identical maps, whereby the FRD severity rates were higher in areas adjacent to the Western Ghats and the seashore. Additionally, IK was used to identify both disease-prone and disease-free areas in Karnataka. After fitting the semivariograms with different models, the exponential model showed the best fit with the semivariogram. Using this model information, OK and IK maps were generated. The identified FRD risk areas in our study, which showed higher disease probability rates (>20%) exceeding the threshold level, need to be monitored with the utmost care to contain and reduce the further spread of the disease in Karnataka. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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13 pages, 1514 KiB  
Article
Multiple Mechanisms Drive the Evolutionary Adaptation of Phytophthora infestans Effector Avr1 to Host Resistance
by Lin-Lin Shen, Abdul Waheed, Yan-Ping Wang, Oswald Nkurikiyimfura, Zong-Hua Wang, Li-Na Yang and Jiasui Zhan
J. Fungi 2021, 7(10), 789; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7100789 - 23 Sep 2021
Cited by 4 | Viewed by 2156
Abstract
Effectors, a group of small proteins secreted by pathogens, play a central role in antagonistic interactions between plant hosts and pathogens. The evolution of effector genes threatens plant disease management and sustainable food production, but population genetic analyses to understand evolutionary mechanisms of [...] Read more.
Effectors, a group of small proteins secreted by pathogens, play a central role in antagonistic interactions between plant hosts and pathogens. The evolution of effector genes threatens plant disease management and sustainable food production, but population genetic analyses to understand evolutionary mechanisms of effector genes are limited compared to molecular and functional studies. Here we investigated the evolution of the Avr1 effector gene from 111 Phytophthora infestans isolates collected from six areas covering three potato cropping regions in China using a population genetic approach. High genetic variation of the effector gene resulted from diverse mechanisms including base substitution, pre-termination, intragenic recombination and diversifying selection. Nearly 80% of the 111 sequences had a point mutation in the 512th nucleotide (T512G), which generated a pre-termination stop codon truncating 38 amino acids in the C-terminal, suggesting that the C-terminal may not be essential to ecological and biological functions of P. infestans. A significant correlation between the frequency of Avr1 sequences with the pre-termination and annual mean temperature in the collection sites suggests that thermal heterogeneity might be one of contributors to the diversifying selection, although biological and biochemical mechanisms of the likely thermal adaptation are not known currently. Our results highlight the risk of rapid adaptation of P. infestans and possibly other pathogens as well to host resistance, and the application of eco-evolutionary principles is necessary for sustainable disease management in agricultural ecosystems. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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20 pages, 5553 KiB  
Article
Type 2 Nep1-Like Proteins from the Biocontrol Oomycete Pythium oligandrum Suppress Phytophthora capsici Infection in Solanaceous Plants
by Kun Yang, Xiaohua Dong, Jialu Li, Yi Wang, Yang Cheng, Ying Zhai, Xiaobo Li, Lihui Wei, Maofeng Jing and Daolong Dou
J. Fungi 2021, 7(7), 496; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7070496 - 22 Jun 2021
Cited by 22 | Viewed by 3446
Abstract
As a non-pathogenic oomycete, the biocontrol agent Pythium oligandrum is able to control plant diseases through direct mycoparasite activity and boosting plant immune responses. Several P. oligandrum elicitors have been found to activate plant immunity as microbe-associated molecular patterns (MAMPs). Necrosis- and ethylene-inducing [...] Read more.
As a non-pathogenic oomycete, the biocontrol agent Pythium oligandrum is able to control plant diseases through direct mycoparasite activity and boosting plant immune responses. Several P. oligandrum elicitors have been found to activate plant immunity as microbe-associated molecular patterns (MAMPs). Necrosis- and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) are a group of MAMPs widely distributed in eukaryotic and prokaryotic plant pathogens. However, little is known about their distribution and functions in P. oligandrum and its sister species Pythium periplocum. Here, we identified a total of 25 NLPs from P. oligandrum (PyolNLPs) and P. periplocum (PypeNLPs). Meanwhile, we found that PyolNLPs/PypeNLPs genes cluster in two chromosomal segments, and our analysis suggests that they expand by duplication and share a common origin totally different from that of pathogenic oomycetes. Nine PyolNLPs/PypeNLPs induced necrosis in Nicotiana benthamiana by agroinfiltration. Eight partially purified PyolNLPs/PypeNLPs were tested for their potential biocontrol activity. PyolNLP5 and PyolNLP7 showed necrosis-inducing activity in N. benthamiana via direct protein infiltration. At sufficient concentrations, they both significantly reduced disease severity and suppressed the in planta growth of Phytophthora capsici in solanaceous plants including N. benthamiana (tobacco), Solanum lycopersicum (tomato) and Capsicum annuum (pepper). Our assays suggest that the Phytophthora suppression effect of PyolNLP5 and PyolNLP7 is irrelevant to reactive oxygen species (ROS) accumulation. Instead, they induce the expression of antimicrobial plant defensin genes, and the induction depends on their conserved nlp24-like peptide pattern. This work demonstrates the biocontrol role of two P. oligandrum NLPs for solanaceous plants, which uncovers a novel approach of utilizing NLPs to develop bioactive formulae for oomycete pathogen control with no ROS-caused injury to plants. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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16 pages, 2744 KiB  
Article
Pathogenicity and Host Range of Pythium kashmirense—A Soil-Borne Oomycete Recently Discovered in the UK
by Clara Benavent-Celma, Alexandra Puertolas, Debbie McLaggan, Pieter van West and Steve Woodward
J. Fungi 2021, 7(6), 479; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7060479 - 12 Jun 2021
Cited by 5 | Viewed by 3398
Abstract
During a survey of oomycetes in ornamental plants carried out at the University of Aberdeen in 2014–2015, Pythium kashmirense was isolated from a specimen of Viburnum plicatum ‘Lanarth’, the first report of this oomycete in the UK (and in Europe). Pathogenicity of a [...] Read more.
During a survey of oomycetes in ornamental plants carried out at the University of Aberdeen in 2014–2015, Pythium kashmirense was isolated from a specimen of Viburnum plicatum ‘Lanarth’, the first report of this oomycete in the UK (and in Europe). Pathogenicity of a Py. kashmirense isolate was examined using a range of plant species. Inoculations were carried out under controlled conditions in the absence of other Pythium and Phytophthora species, on Glycine max (soya bean), Phaseolus vulgaris (common bean), Lupinus angustifolius (blue lupin), Cucumis sativa (cucumber) and Viburnum opulus. The majority of inoculations caused pre-emergence damping-off, as well as seed rot and root rot. In the in vitro assays, germination rates (%) of soya bean and blue lupin seeds were less than 50%; in the in vivo inoculations on plants, over 50% of soya bean, blue lupin and common bean plants died; in contrast, cucumber plants showed lower susceptibility in pathogenicity tests, with an approximately 80% germination rate in in vitro tests, and 25% dead plants in the in planta inoculations. Inoculations carried out on root systems of Viburnum opulus caused severe necrosis and root rot. Little research was previously conducted on pathogenicity of Py. kashmirense and its relationship with losses in crop yield and quality. The present study showed varying virulence on the different plant species tested after inoculation with Py. kashmirense. Despite the lack of clear host specialization, infection by Py. kashmirense decreased seedling survival and health of plants in a range of important agricultural and ornamental plant species. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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32 pages, 5419 KiB  
Article
The Destructive Tree Pathogen Phytophthora ramorum Originates from the Laurosilva Forests of East Asia
by Thomas Jung, Marília Horta Jung, Joan F. Webber, Koji Kageyama, Ayaka Hieno, Hayato Masuya, Seiji Uematsu, Ana Pérez-Sierra, Anna R. Harris, Jack Forster, Helen Rees, Bruno Scanu, Sneha Patra, Tomáš Kudláček, Josef Janoušek, Tamara Corcobado, Ivan Milenković, Zoltán Nagy, Ildikó Csorba, József Bakonyi and Clive M. Brasieradd Show full author list remove Hide full author list
J. Fungi 2021, 7(3), 226; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7030226 - 18 Mar 2021
Cited by 42 | Viewed by 7953
Abstract
As global plant trade expands, tree disease epidemics caused by pathogen introductions are increasing. Since ca 2000, the introduced oomycete Phytophthora ramorum has caused devastating epidemics in Europe and North America, spreading as four ancient clonal lineages, each of a single mating type, [...] Read more.
As global plant trade expands, tree disease epidemics caused by pathogen introductions are increasing. Since ca 2000, the introduced oomycete Phytophthora ramorum has caused devastating epidemics in Europe and North America, spreading as four ancient clonal lineages, each of a single mating type, suggesting different geographical origins. We surveyed laurosilva forests for P. ramorum around Fansipan mountain on the Vietnam-China border and on Shikoku and Kyushu islands, southwest Japan. The surveys yielded 71 P. ramorum isolates which we assigned to eight new lineages, IC1 to IC5 from Vietnam and NP1 to NP3 from Japan, based on differences in colony characteristics, gene x environment responses and multigene phylogeny. Molecular phylogenetic trees and networks revealed the eight Asian lineages were dispersed across the topology of the introduced European and North American lineages. The deepest node within P. ramorum, the divergence of lineages NP1 and NP2, was estimated at 0.5 to 1.6 Myr. The Asian lineages were each of a single mating type, and at some locations, lineages of “opposite” mating type were present, suggesting opportunities for inter-lineage recombination. Based on the high level of phenotypic and phylogenetic diversity in the sample populations, the coalescence results and the absence of overt host symptoms, we conclude that P. ramorum comprises many anciently divergent lineages native to the laurosilva forests between eastern Indochina and Japan. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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9 pages, 2495 KiB  
Article
Halophytophthora fluviatilis Pathogenicity and Distribution along a Mediterranean-Subalpine Gradient
by Maria Caballol, Dora Štraus, Héctor Macia, Xavier Ramis, Miguel Á. Redondo and Jonàs Oliva
J. Fungi 2021, 7(2), 112; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7020112 - 03 Feb 2021
Cited by 6 | Viewed by 2000
Abstract
Halophytophthora species have been traditionally regarded as brackish water oomycetes; however, recent reports in inland freshwater call for a better understanding of their ecology and possible pathogenicity. We studied the distribution of Halophytophthora fluviatilis in 117 forest streams by metabarcoding river filtrates taken [...] Read more.
Halophytophthora species have been traditionally regarded as brackish water oomycetes; however, recent reports in inland freshwater call for a better understanding of their ecology and possible pathogenicity. We studied the distribution of Halophytophthora fluviatilis in 117 forest streams by metabarcoding river filtrates taken in spring and autumn and by direct isolation from floating leaves. Pathogenicity on six Fagaceae species and Alnus glutinosa was assessed by stem inoculations. The distribution of H. fluviatilis was correlated with high mean annual temperatures (>93.5% of reports in Ta > 12.2 °C) and low precipitation records. H. fluviatilis was therefore widely distributed in forest streams in a warm–dry climate, but it was mostly absent in subalpine streams. H. fluviatilis was primarily detected in autumn with few findings in spring (28.4% vs. 2.7% of streams). H. fluviatilis was able to cause small lesions on some tree species such as Quercus pubescens, Q. suber and A. glutinosa. Our findings suggest that H. fluviatilis may be adapted to warm and dry conditions, and that it does not pose a significant threat to the most common Mediterranean broadleaved trees. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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18 pages, 1846 KiB  
Article
Application of Real-Time PCR for the Detection and Quantification of Oomycetes in Ornamental Nursery Stock
by Alexandra Puertolas, Peter J. M. Bonants, Eric Boa and Steve Woodward
J. Fungi 2021, 7(2), 87; https://0-doi-org.brum.beds.ac.uk/10.3390/jof7020087 - 27 Jan 2021
Cited by 12 | Viewed by 2635
Abstract
Numerous Phytophthora and Pythium disease outbreaks have occurred in Europe following inadvertent introduction of contaminated ornamental plants. Detection and identification of pathogens are crucial to reduce risks and improve plant biosecurity in Europe and globally. Oomycete diversity present in roots and compost was [...] Read more.
Numerous Phytophthora and Pythium disease outbreaks have occurred in Europe following inadvertent introduction of contaminated ornamental plants. Detection and identification of pathogens are crucial to reduce risks and improve plant biosecurity in Europe and globally. Oomycete diversity present in roots and compost was determined in 99 hardy woody plants bought from nurseries, retailers and internet sellers, using both isolations and molecular analyses. Oomycete DNA was quantified using real-time PCR of environmental DNA from the plants using three loci: ITS, trnM-trnP-trnM and atp9-nad9. At least one oomycete species was isolated from 89.9% of plants using classical techniques. In total, 10 Phytophthora spp., 17 Pythium spp. and 5 Phytopythium spp. were isolated. Oomycetes were isolated from 86% of asymptomatic plants, but real-time PCR demonstrated that oomycetes were associated with all plants tested. More oomycete DNA occurred in composts in comparison with roots and filters from baiting water (a mean of 7.91 ng g−1, 6.55 × 10−1 ng g−1 and 5.62 × 10−1 ng g−1 of oomycete DNA detected in compost with ITS, trnM and atp9 probes, respectively); the ITS probe detected the highest quantities of oomycete DNA. No significant differences were found in quantities of oomycete DNA detected using real-time PCR in plants purchased online or from traditional retailers. Full article
(This article belongs to the Special Issue Oomycetes – Diversity, Taxonomy, Evolution, Ecology and Host-Pathogen Interactions)
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