Pythium Intermedium Research Articles

Pythium intermedium (damping-off)

This datasheet on Pythium intermedium covers Identity, Distribution, Hosts/Species Affected, Further Information.

Oomycetes associated with Prunus serotina persist in soil after tree harvest

Soil-borne pathogens can shape forest communities by lowering seedling survivorship. Many soil pathogens can persist long-term as survival spores, but how long pathogens outlive tree hosts in gap soils and whether they continue to affect seedling survival is uncertain. We studied the presence of oomycetes and evaluated seedling performance in soils near live Prunus serotina trees, and 0.5 and 1.5-y-old stumps. We isolated five species of oomycetes from soils, two of which were pathogenic (Pythium intermedium and Pythium irregulare) to Prunus serotina. There was a non-significant ~10.5% increase in conspecific seedling survival in stumps versus live trees, and pathogens were present in soils of all stump ages. The continued presence of pathogens of Prunus serotina in gap soils demonstrates the potential for impacts on conspecific regeneration after tree death, though the slight improvement in survival suggests that these effects may weaken with time.

Electronic Nose Differentiation between Quercus robur Acorns Infected by Pathogenic Oomycetes Phytophthora plurivora and Pythium intermedium.

Identification of the presence of pathogenic oomycetes in infected plant material proved possible using an electronic nose, giving hope for a tool to assist nurseries and quarantine services. Previously, species of Phytophthora plurivora and Pythium intermedium have been successfully distinguished in germinated acorns of English oak Quercus robur L. Chemical compound analyses performed by HS-SPME/GC-MS (Headspace Solid-Phase Microextraction/Gas Chromatography–Mass Spectrometry) revealed the presence of volatile antifungal molecules produced by oak seedlings belonging to terpenes and alkanes. Compounds characteristic only of Phytophthora plurivora or Pythium intermedium were also found. Methylcarveol occurred when germinated acorns were infected with Pythium, while neophytadiene (isomer 2 and 3) occurred only when infected with Phytophthora. Moreover, isopentanol was found in acorns infected with Phytophthora, while in control, isopentyl vinyl ether was not observed anywhere else. Among the numerous volatile compounds, isopentanol only occurred in acorns infected with Phytophthora and methylcarveol in acorns infected with Pythium.

Pythium intermedium, a species complex consisting of three phylogenetic species found in cool-temperate forest ecosystems

Pythium intermedium plays a vital role in the carbon cycle of cool-temperate forests and is widely distributed in Japan's forest soils. In this study, we performed a phylogenetic analysis of the P. intermedium species complex using DNA sequences from multiple loci. The study included 35 isolates from cool-temperate forest soils, seven known P. intermedium isolates, and six known Pythium attrantheridium isolates. We also performed morphological observations and mating tests. Our results showed that all the isolates formed one large clade but were divided into three subclades. Furthermore, we observed many mating reactions between isolates from different subclades, including between P. attrantheridium and P. intermedium. Therefore, we suggest that P. intermedium, P. attrantheridium, and another phylogenetic species belong to one species complex. This is the first report of a species complex within P. intermedium and will be helpful in understanding the evolution of Pythium species in natural ecosystems.

First report on the occurrence of Phytophthoraobscura on Acerpseudoplatanus in Slovakia

AbstractSycamore maple is a valuable admixture species in many European countries, including Slovakia. As most species belonging to the genus Acer, it is susceptible to several pathogenic organisms including species of Oomycetes. To determine whether the decline of Acer pseudoplatanus in Slovakia is caused by pathogenic Oomycetes, soil samples were taken from the rhizosphere in three sycamore maple stands. Isolation from leaf baits and subsequent identification based on sequencing of the ITS showed the presence of three species: Pythium intermedium, Phytophthora plurivora and Phytophthora obscura. This is the first report on the occurrence of P. plurivora and P. obscura in the rhizosphere of declining sycamore maple stands in Slovakia.

Application of a Low-Cost Electronic Nose for Differentiation between Pathogenic Oomycetes Pythium intermedium and Phytophthora plurivora.

Compared with traditional gas chromatography–mass spectrometry techniques, electronic noses are non-invasive and can be a rapid, cost-effective option for several applications. This paper presents comparative studies of differentiation between odors emitted by two forest pathogens: Pythium and Phytophthora, measured by a low-cost electronic nose. The electronic nose applies six non-specific Figaro Inc. metal oxide sensors. Various features describing shapes of the measurement curves of sensors’ response to the odors’ exposure were extracted and used for building the classification models. As a machine learning algorithm for classification, we use the Support Vector Machine (SVM) method and various measures to assess classification models’ performance. Differentiation between Phytophthora and Pythium species has an important practical aspect allowing forest practitioners to take appropriate plant protection. We demonstrate the possibility to recognize and differentiate between the two mentioned species with acceptable accuracy by our low-cost electronic nose.

Efficiency of bio-evaporation of Arugula leaves to control root rot disease on cucumber caused by Pythium intermedium in Greenhouse

The efficiency of the Arugula (Eruca vesicaria) leaves extracts against the fungus Pythium intermedium, the root rot disease agent, was evaluated with three concentrations of 2.5, 5, 10 g / kg soil as biofumigation. The fungi around infected root of cucumber plants were isolated and diagnosed from different locations in Baghdad such as Rashidiya, Madaen, Yousifiya and Mahmudiya. The extract of arugula plants significantly reduced the incidence and severity of root rot disease on cucumber plant after 45 days of cultivation compared with control. The highest reduction in incidence and severity of the disease was about 4% and 5% respectively with arugula extract 10 g / kg soil. The study was the first record to evaluate the incidence of P. intermedium on root of cucumber plants in Iraq. Further, all concentrations of arugula extract showed increase on the growth parameters compared with control. In arugula extract 10 g/kg soil the growth parameter such as plant length, leaf length, leaf width, wet weight and dry weight were 35 cm, 5.5 cm, 6 cm, 4 g and 0.28 g respectively. Furthermore, Significant differences in the value of the biological index of arugula plant extract treatments ranging from 2627 to 3433 compared to the treatment of P. intermedium, which was about 1910, while did not differ significantly from the treatment of control with a vital index of 3830.

Isolation and pathogenicity of Phytophthora species from sessile oak (Quercus petraea (Matt.) Liebl.) stands in Slovakia

AbstractDuring the monitoring of oak decline phenomenon in Slovakia, symptoms indicative of Phytophthora diseases were observed in sessile oak stands in western Slovakia. The study aimed to test the presence and diversity of Phytophthora species associated with declining oak stands. From rhizosphere soil samples, Phytophthora plurivora, P. quercina and Pythium intermedium were detected. Soil inoculation tests with P. plurivora and P. quercina on 1‐year‐old oak plants inflicted damage to the root system, and significant differences in measured root parameters between the inoculated and control treatments after 5 months. Although more wilting symptoms were observed in P. plurivora—infected seedlings (7 out of 12 inoculated seedlings), P. quercina caused the highest amount of damage to root systems, and for example, fine root length was 1.6 times shorter compared to the control. To our knowledge, this is the first report of P. plurivora and P. quercina in sessile oak stands in Slovakia.

Phytopythium and Pythium Species (Oomycota) Isolated from Freshwater Environments of Korea

Oomycetes are widely distributed in various environments, including desert and polar regions. Depending upon different habits and hosts, they have evolved with both saprophytic and pathogenic nutritional modes. Freshwater ecosystem is one of the most important habitats for members of oomycetes. Most studies on oomycete diversity, however, have been biased mostly towards terrestrial phytopathogenic species, rather than aquatic species, although their roles as saprophytes and parasites are essential for freshwater ecosystems. In this study, we isolated oomycete strains from soil sediment, algae, and decaying plant debris in freshwater streams of Korea. The strains were identified based on cultural and morphological characteristics, as well as molecular phylogenetic analyses of ITS rDNA, cox1, and cox2 mtDNA sequences. As a result, we discovered eight oomycete species previously unknown in Korea, namely Phytopythium chamaehyphon, Phytopythium litorale, Phytopythium vexans, Pythium diclinum, Pythium heterothallicum, Pythium inflatum, Pythium intermedium, and Pythium oopapillum. Diversity and ecology of freshwater oomycetes in Korea are poorly understood. This study could contribute to understand their distribution and ecological function in freshwater ecosystem.

Interactions between dark septate endophytes, ectomycorrhizal fungi and root pathogens in vitro.

Dark septate endophytes (DSEs) are widely distributed worldwide and can promote plant growth. Therefore, they are considered potentially important plant allies, especially in stressful environments. Previous studies have reported that DSEs cohabit roots with other microorganisms such as ectomycorrhizal (ECM), endophytic and pathogenic fungi/oomycetes. However, interactions between different DSE species have not yet been reported, and studies on the interactions between DSEs and other fungi are scarce. Using a simple and reproducible pairwise growth assay in vitro, we studied the synergistic/antagonistic interactions between eight DSEs, two ECM fungi and three root pathogens. Most of the DSE/DSE outcomes were neutral. Interestingly, we identified several DSE strains acting in synergy with other strains, as well as strains that could potentially act as biocontrol agents. Notably, three metal-tolerant DSE strains, namely, Cadophora sp., Leptodontidium sp. and Phialophora mustea, could decrease the growth of the root phytopathogens Pythium intermedium, Phytophthora citricola and Heterobasidion annosum. The present data are discussed in the general context of the use of fungal consortia as inocula in the tree-based phytomanagement of marginal lands.

Cropping history shapes fungal, oomycete and nematode communities in arable soils and affects cavity spot in carrot

Fungal, nematode and oomycete communities in arable soil serve diverse ecological functions. However, little is known about the dynamics among these three taxonomic groups. In order to identify the driving factors and networks shaping these communities, and the influence of communities on the development of carrot cavity spot, we collected soil samples from more than sixty fields in which carrot was planned as the next crop, and analyzed the microbial communities using metabarcoding. Crop grown before sampling was best in explaining variation in community composition, but also soil type was shaping fungal and nematode communities, but not oomycete communities. Network analysis revealed that correlations between taxa within taxonomic groups were mostly positive whereas negative correlations dominated between taxa across the different taxonomic groups. Pythium intermedium and P. irregulare from soil samples were found to be associated with cavity spot disease in carrot, and were also found in the lesions of cavity spot. Our study demonstrate that previous crop and soil type significantly affect microbial communities and the development of symptoms of cavity spot in carrot. We also found that differences in co-occurrences within and between taxonomic groups exist.

Candidate Causal Organisms for Apple Replant Disease in the United Kingdom

Continuous planting of apple in the same area leads to reduced growth vigor and subsequent crop losses, i.e., apple replant disease (ARD) syndrome. Several soilborne plant pathogens including Pythium, Fusarium, and Cylindrocarpon spp. are often proposed as candidate causal organisms for ARD. In addition, the presence of root lesion nematodes and the lack of beneficial groups of bacteria are believed to exacerbate or ameliorate the effects of the plant pathogens. The importance of these proposed causal and auxiliary agents seems to vary with site. Using a spatially explicit sampling strategy to minimize spatial variability we collected rhizosphere soil samples from neighboring pairs of healthy and putative ARD trees to identify candidate causal organisms of ARD. Amplicon-based metabarcoding was used to obtain community-level profiles of the bacteria, fungi, oomycetes and nematodes in the soil samples. Total bacterial and fungal biomass in each sample was estimated using qPCR to adjust the raw sequence reads data. The results suggested that ARD is not ameliorated by enhanced rhizosphere biodiversity per se. We identified 25 bacterial operational taxonomic units (OTUs), 16 fungal OTUs, 18 oomycetes OTUs, and one nematode OTU group with differential abundance between healthy and putative ARD trees. All 25 bacterial OTUs had lower abundance in samples from ARD symptomatic trees than from healthy trees. One AMF OTU had lower abundance in samples from ARD symptomatic trees. None of 13 fungal OTUs that had higher abundance in samples from ARD symptomatic trees is a known plant pathogen; but at least one Pythium OTU (probably Pythium intermedium) is a candidate for causing ARD. The abundance of one nematode OTU was much higher in samples from ARD symptomatic trees than in healthy trees. The results suggest that, apart from the use of broad spectrum fumigants, the complexity of ARD may necessitate the combined use of multiple management strategies with the success of these measures expected to vary considerably between sites because of the varying importance of ARD causal agents among sites.

Volatile-mediated suppression of plant pathogens is related to soil properties and microbial community composition

There is increasing evidence that the soil microbial community produces a suite of volatile organic compounds that suppress plant pathogens. However, it remains unknown which soil properties and management practices influence volatile-mediated pathogen suppression. The aim of this study was to relate soil properties to growth suppression of three plant pathogens by soil volatiles. We measured the effect of volatiles emitted from a broad range of agricultural soils on the in vitro growth of the plant pathogenic fungi Rhizoctonia solani and Fusarium oxysporum, and the oomycete Pythium intermedium. Growth suppression of pathogens by soil volatiles could be linked to various soil properties, and some aspects of microbial community composition and field history, using multiple linear regression. Volatile-mediated suppression of mycelial development occurred for each pathogen type, but the magnitude of inhibition differed among soils as well as pathogens. On average R. solani and P. ultimum appeared more sensitive to volatile suppression than F. oxysporum. Suppression of R. solani by volatiles was positively correlated with organic matter content, microbial biomass and proportion of litter saprotrophs in the microbial community, but negatively correlated with pH, microbial diversity (Shannon), and the proportion of Acidobacteria in the community. R. solani, F. oxysporum, and P. intermedium suppression by volatiles was affected by various management practices occurring in the soil's field history, such as reduced tillage, the presence of certain crops in the crop rotation, and the application of solid manure. P. intermedium suppression was also negatively correlated with soil sulphur content. This study identifies pathogen-specific drivers of growth-suppressive volatiles, a critical step in integrating soil volatiles into prediction and management of soil-borne plant diseases.

Pythium species associated with root rot complex in winter-grown parsnip and parsley crops in south eastern Australia

Root rot of parsnip (Pastinaca sativa) and parsley (Petroselinum crispum) crops in south-eastern Australia is a disease complex, causing up to 80 % and 100 % yield losses, respectively. It is attributed to a range of fungi and oomycetes. We report on isolation and identification of eleven Pythium spp. from naturally infected roots of parsnip and parsley collected during systematic monthly surveys of commercial, winter-grown crops with prevailing root rots at Devon Meadows and Clyde, Victoria, Australia in 2009 to 2011. Pythium intermedium, P. ultimum var. ultimum, P. rostratifingens and species from the P. dissotocum complex were common to both hosts. Pythium irregulare, P. sylvaticum, P. camurandrum, P. vanterpoolii and P. tracheiphilum were isolated only from parsnip; and P. mastophorum and P. sulcatum only from parsley. This is the first report of P. camurandrum and P. rostratifingens in Australia and the first report of P. tracheiphilum and P. vanterpoolii from parsnip in Australia. Selected Pythium spp. tested for their pathogenicity in glasshouse conditions were pathogenic to both hosts. Pythium sulcatum, P. mastophorum and P. tracheiphilum caused severe root in 35 %, 53 % and 25 % of parsley seedlings, respectively. Pythium sulcatum and P. intermedium caused severe root in 50 % and 15 % of parsnip seedlings, respectively. In growth chamber studies, P. sulcatum was pathogenic to parsley seedlings at 10 °C, 18 °C and 24 °C.

Compost Teas and Reused Nutrient Solution Suppress Plant Pathogens In Vitro

In vitro testing was conducted to evaluate the inhibition potential of three compost teas (pine bark, manure, and vermicasting), Root Rescue Landscape Powder® (a mix of mycorrhizae and other beneficial microbes), waste diatomaceous earth (DE; from beer brewing), and a greenhouse nutrient solution, which had been reused for 20 years on six plant pathogens: Fusarium foetens, Rhizoctonia solani, Sclerotinia sclerotiorum, Phytophthora cryptogea, Pythium intermedium, and P. ultimum. The test materials showed in vitro inhibition on most of the test pathogens. Pine bark tea suppressed growth of all six pathogens, and inhibition exceeded 50% after 10 days of coincubation. Vermicasting tea showed over 40% inhibition against S. sclerotiorum and F. foetens; manure tea showed 42% inhibition against F. foetens; DE showed 40% inhibition against F. foetens, S. sclerotiorum, and R. solani; whereas reused greenhouse nutrient solution showed 56.7% inhibition against R. solani and 43.4% inhibition against F. foetens; Root Rescue showed 66% inhibition against P. intermedium. The results suggest that the six test materials have potential in the control of these soil- and water-borne pathogens in plant production system.

Development of real-time PCR technique for the estimation of population density of Pythium intermedium in forest soils

Pythium intermedium is known to play an important role in the carbon cycling of cool-temperate forest soils. In this study, a fast, precise and effective real-time PCR technique for estimating the population densities of P. intermedium from soils was developed using species-specific primers. Specificity was confirmed both with conventional PCR and real-time PCR. The detection limit (sensitivity) was determined and amplification standard curves were generated using SYBR Green II fluorescent dye. A rapid and accurate assay for quantification of P. intermedium in Takayama forest soils of Japan was developed using a combination of a new DNA extraction method and PCR primers were developed for real-time PCR. And the distribution of P. intermedium in forest soil was investigated with both soil plating method and the developed real-time PCR technique. This new technique will be a useful tool and can be applied to practical use for studying the role of Pythium species in forest and agricultural ecosystems.

First Report of Pythium intermedium Causing Root Rot on Rosa canina Rootstock in France.

Old cultivars of roses (Rosa spp.) established on Rosa canina as rootstock are grown in field collections in the repository at Gaillard in eastern France, close to the Swiss border. During June 2005 and July 2006, several rose plants in full vegetation were severely wilted, leading ultimately to plant death. Necrotic lesions were present on the roots, and marginal tissue was excised and incubated in the dark at 20°C on PARP V8 agar plates (1). Similar isolates were obtained in both years, which were inoculated within 4 days on V8 agar medium and incubated at 25°C. The pathogen colonies grew approximately 30 mm daily on V8 agar. Colonies on corn meal agar (CMA) (1) were submerged, with or without a vague radiate pattern on potato carrot agar. Main hyphae were as much as 7 μm wide. Sporangia and zoospores were not produced. Hyphal swellings as much as 25 μm in diameter were abundant, terminal, and sometimes intercalary, often forming regular, dense chains in basipetal succession at hyphal tips and readily liberated. The morphological characters matched those described for Pythium intermedium (2). DNA sequencing of the ITS rDNA (ITS1, ITS2, and 5.8S rDNA) was generated using primers ITS5 and ITS4 in primary PCR (35 cycles: 96°C for 1 min, 55°C for 1 min, and 72°C for 2 min) and sequencing reactions (1). All isolates yielded identical ITS sequences, which were identical to the ex-type strain of P. intermedium, CBS 266.38 (GenBank Accession No. AY598647). The ITS sequence was deposited as GenBank Accession No. EF078693 (National Center for Biotechnology Information, NCBI, Bethesda, MD). Pathogenicity testing was performed on 3-year-old Rosa canina rootstocks from clonal propagation in 25 cm in diameter and 40 cm deep pots of compost 297 (Ricoter, Aarberg, Switzerland). Five-day-old mycelial plugs of our isolates grown on CMA (1) were inoculated in two pots, and roots were mechanically wounded. Sterile plugs were used on two control plants set aside. All plants were kept for 2 weeks at 20°C in a glasshouse with sufficient watering. Extensive necrotic lesions developed on inoculated roots, and severe wilting and leaves drying out were also observed. The controls showed no symptoms. P. intermedium was reisolated from margins of root lesions, thus fulfilling the postulates of Koch. P. intermedium was originally isolated from dead plant material (2) but is known as a typical soil inhabitant. It also has been isolated from water and living material from numerous plant species, but never from the genus Rosa until now. To our knowledge, this is the first record of P. intermedium on Rosa spp. grafted on Rosa canina in France.

Root infection of wasabi (Wasabia japonica) by Pythium species

Wasabi (Wasabia japonica) is cultivated under cool, humid conditions in many regions of the world for its rhizome, which is used as a culinary ingredient. In British Columbia, there is some wasabi production under semihydroponic conditions in polyethylene greenhouses. In January 2004, wasabi plants with browning and root loss, with no apparent foliar symptoms, were obtained. Pythium dissotocum and Pythium intermedium were consistently isolated from the affected roots. Wasabi plants produced from meristem-tip tissue culture were grown hydroponically in Gamborg's B5 nutrient solution at 18 °C for 6 months, inoculated with mycelial plugs of each Pythium sp., and incubated at 20 °C. After 2 months, the inoculated plants had significant root browning and loss, and the root dry mass of inoculated plants was reduced to 16% of that in the noninoculated controls. Both Pythium spp. were observed colonizing the roots and were recovered from inoculated plants. Pythium dissotocum and P. intermedium appear to be prevalent root pathogens of W. japonica without inducing apparent foliar symptoms. However, root loss can predispose the affected plants to other biotic and abiotic stresses, leading to plant mortality.

Isozyme variation in heterothallic species and related asexual isolates of Pythium

A collection of 63 heterothallic and asexual (sexually sterile) isolates were compared by isozyme analysis, vegetative characters, and their ability to produce oospores in paired cultures. The collection included isolates identified as Pythium heterothallicum, Pythium intermedium, Pythium macrosporum, Pythium splendens, Pythium sylvaticum, and Pythium tracheiphilum, and several unidentified isolates. Isolates were separated into 41 multilocus genotypes as defined by 11 isozyme loci. The data were analyzed with previously published data for Pythium ultimum, and dendrograms were obtained from unweighted pair-group method, arithmetic average cluster analysis. Forty-six genotypes (including nine of P. ultimum) grouped into seven clusters and three solitary genotypes. Six clusters contained known isolates of the aforementioned species and the seventh contained P. ultimum. Isolates within both the P. heterothallicum and P. sylvaticum clusters produced oospores when grown in paired cultures. Two of three isolates in the P. splendens cluster produced oospores, but none of the isolates in the P. intermedium and P. macrosporum clusters produced oospores when grown in pairs. Genotypes belonging to the P. intermedium cluster separated into two sister groups that had morphologically different vegetative bodies. There were no consistent vegetative characteristics to distinguish the species P. macrosporum, P. heterothallicum, and P. sylvaticum. Isozyme analysis provides an effective means of identifying Pythium species that do not readily produce oospores in culture. Key words: Pythium heterothallicum, Pythium intermedium, Pythium macrosporum, Pythium sylvaticum, Pythium splendens, Pythium tracheiphilum.

Wilt and Root Diseases of Asclepias tuberosa L.

Chlorosis and wilting, followed by weak flowering or death, have been occurring in Asclepias tuberosa plants grown in Israel. Roots have been rotted and tuberous roots have shown dark lesions, sometimes with sclerotia. A binucleate Rhizoctonia sp. was detected on 39% and Pythium intermedium on 23% of diseased samples. Other organisms were less prevalent. Wilting began 7 days after seedlings were inoculated with P. intermedium or the binucleate Rhizoctonia sp. or both, with disease incidence ranging from 25 to 65% and disease severity index ranging from 0.30 to 0.85 (scale of 0 to 3). Healthy tuberous roots inoculated with the binucleate Rhizoctonia sp. exhibited dry rot within 4 to 7 days, and irregular black sclerotia of the pathogen were present 2 weeks later. This is the first report of either a binucleate Rhizoctonia sp. or P. intermedium occurring in A. tuberosa.