Pythium ultimum

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Pythium ultimum
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Stramenopiles
Phylum: Oomycota
Order: Peronosporales
Family: Pythiaceae
Genus: Pythium
Species:
P. ultimum
Binomial name
Pythium ultimum
Trow, (1901)
Varieties

Pythium ultimum is a plant pathogen. It causes damping off and root rot diseases of hundreds of diverse plant hosts including maize, soybean, potato, wheat, fir, and many ornamental species. [1] [2] P. ultimum belongs to the peronosporalean lineage of oomycetes, [3] along with other important plant pathogens such as Phytophthora spp. and many genera of downy mildews. P. ultimum is a frequent inhabitant of fields, freshwater ponds, and decomposing vegetation in most areas of the world. Contributing to the widespread distribution and persistence of P. ultimum is its ability to grow saprotrophically in soil and plant residue. This trait is also exhibited by most Pythium spp. but not by the related Phytophthora spp., which can only colonize living plant hosts.

Contents

Pathology and disease management

P. ultimum is a species complex that includes P. u. var. ultimum and P. u. var. sporangiiferum. [4] One major distinguishing feature between these two genetically distinct organisms is the production of zoospores (swimming spores) -- which are produced only rarely by P. u. var. ultimum. Asexual reproduction of both P. u. var. sporangiiferum and P. u. var. ultimum results in the formation of sporangia that develop at the tips of hyphae. [5] Wind, water or other disruptions to the soil can disperse the pathogen by causing the sporangia to detach. In the case of P. u. var. sporangiiferum , the free sporangia release zoospores in response to outside stimuli. These zoospores can then "swim" to susceptible root tissues. This infection process is referred to as "indirect germination". Contrary to P. u. var. sporangiiferum , the free sporangia of P. u. var. ultimum do not release zoospores, instead, they undergo a process called "direct germination", during which the sporangia themselves form invasive hyphae that serve as the primary inoculum source. Generation of these infectious hyphae is initiated once the free sporangia have made contact with susceptible plant tissues. Once attached, they form appressoria; specialized infection structures that can generate enough turgor pressure to punch through the plant cuticle. [6] From there, both variants engage in necrotrophy, a process by which pathogenic organisms kill host cells in order to access and incorporate their contents to meet their nutritional needs. [7] P. u. var. ultimum in particular, is known to release a cascade of unique effector proteins to break down and degrade various cellular components of plant tissues. [8] Both species make oospores, which are thick-walled structures produced by sexual recombination that can serve as survival structures during times of stress. [9] Both varieties are self-fertile (homothallic), which means that a single strain can mate with itself. [10] One important ecological difference between the different types of spores produced by these organisms, is that sporangia and zoospores are short-lived, while the thick-walled oospores can persist for years within soil, surviving even winter freezes. [11] Common signs of a Pythium infection include stunting of the plants, brown coloration of root-tips, and wilting of the plant during the warm part of the day. [12] Management of disease is challenging but focuses on sanitation, fungicides, and biological control. Fungicides include mefenoxam, thiadiazole, etridiazole, propamocarb, dimethomorph, and phosphonates. Biological control agents include the bacteria Bacillus subtilis , Enterobacter cloacae , Streptomyces griseoviridis , and the fungi Candida oleophila , Gliocladium catenulatum , Trichoderma harzianum , and T. virens . [13] [14]

Effective resistance in the plant host is generally not available. Sanitation is very important since the pathogen can be easily introduced into pasteurized soil or even soil-free potting mixes on dirty tools or pots. Especially in greenhouses, fungus gnats may also help move the pathogen from place to place. A recent study of greenhouses in Michigan revealed that the same pathogen populations were responsible for the root rot of all greenhouse ornamental plants over a two-year period. These results stress the importance of sanitation and encourage greenhouse growers to improve their scouting of all incoming plant material to prevent additional root rot. [15]

Genetics

Pythium ultimum is divided into varieties ultimum and sporangiiferum, the genomes of both of which have been sequenced. [16] [17] Analysis of the genomes suggest that the two species encode 15,290 and 14,086 proteins, respectively.

Samples of Pythium sp. isolates from soils in Japan were analyzed phylogenetically; the phylogenetic trees were divided into five monophyletic clades, proposed as new genera (Pythium, Elongisporangium , Ovatisporangium , Globisporangium , and Pilasporangium ). Under this new phylogeny, P. ultimum would be renamed to Globisporangium ultimum . [18]

Liang et al., 2020 finds GH55 – common in some other Pythium spp. – is absent from this species. [19]

Microbiome impacts on P. ultimum disease incidence and severity

While fungicides and proper sanitation measures remain important means of Pythium control and management, natural means of suppression via the formation of disease suppressive environments, is becoming better understood, and could pave the way for more sustainable practices in commercial production of crops susceptible to P. ultimum.

Disease suppressive environments are defined as environments in which environmental conditions are favorable, a susceptible host is present along with a virulent pathogen, but disease levels remain low. [20] The soil microbiome of plants is known to influence soil-borne diseases incidence and severity by either indirectly combatting disease by fortifying plant defenses or through direct microbe-microbe interactions, thus helping to create a disease suppressive environment. [21] [22] [23] Both P. u. var. sporangiiferum and P. u. var. ultimum are not immune to the impacts of microbiome-based disease suppression. Many studies have correlated increased suppression of P. ultimum with an increase in total abundance of microorganisms present in growth media microbiomes. [24] [25] For example, increased microbial activity and biomass has been correlated with a decrease in P. ultimum induced damping-off of cucumber. [26] [27] The method of microbe-mediated suppression of Pythium remains uncertain, however, these and other studies suggest that competition in the rhizosphere for carbon and nitrogen resources could play a role. [28] Another theory suggests that at high enough concentrations, bacteria can quickly coat and protect susceptible plant tissues, leaving no room for Pythium adherence and subsequent infection. [29]

Related Research Articles

<i>Phytophthora infestans</i> Species of single-celled organism

Phytophthora infestans is an oomycete or water mold, a fungus-like microorganism that causes the serious potato and tomato disease known as late blight or potato blight. Early blight, caused by Alternaria solani, is also often called "potato blight". Late blight was a major culprit in the 1840s European, the 1845–1852 Irish, and the 1846 Highland potato famines. The organism can also infect some other members of the Solanaceae. The pathogen is favored by moist, cool environments: sporulation is optimal at 12–18 °C (54–64 °F) in water-saturated or nearly saturated environments, and zoospore production is favored at temperatures below 15 °C (59 °F). Lesion growth rates are typically optimal at a slightly warmer temperature range of 20 to 24 °C.

<span class="mw-page-title-main">Oomycete</span> Fungus-like eukaryotic microorganism

The Oomycetes, or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the result of contact between hyphae of male antheridia and female oogonia; these spores can overwinter and are known as resting spores. Asexual reproduction involves the formation of chlamydospores and sporangia, producing motile zoospores. Oomycetes occupy both saprophytic and pathogenic lifestyles, and include some of the most notorious pathogens of plants, causing devastating diseases such as late blight of potato and sudden oak death. One oomycete, the mycoparasite Pythium oligandrum, is used for biocontrol, attacking plant pathogenic fungi. The oomycetes are also often referred to as water molds, although the water-preferring nature which led to that name is not true of most species, which are terrestrial pathogens.

<i>Pythium</i> Genus of single-celled organisms

Pythium is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but Pythium insidiosum is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequently a vector for their transmission.

<i>Phytophthora palmivora</i> Species of single-celled organism

Phytophthora palmivora is an oomycete that causes bud-rot of palms, fruit-rot or kole-roga of coconut and areca nut. These are among the most serious diseases caused by fungi and moulds in South India. It occurs almost every year in Malnad, Mysore, North & South Kanara, Malabar and other areas. Similar diseases of palms are also known to occur in Sri Lanka, Mauritius, and Sumatra. The causative organism was first identified as P. palmivora by Edwin John Butler in 1917.

Pythium irregulare is a soil borne oomycete plant pathogen. Oomycetes, also known as "water molds", are fungal-like protists. They are fungal-like because of their similar life cycles, but differ in that the resting stage is diploid, they have coenocytic hyphae, a larger genome, cellulose in their cell walls instead of chitin, and contain zoospores and oospores.

<i>Phytophthora erythroseptica</i> Species of single-celled organism

Phytophthora erythroseptica—also known as pink rot along with several other species of Phytophthora—is a plant pathogen. It infects potatoes causing their tubers to turn pink and damages leaves. It also infects tulips (Tulipa) damaging their leaves and shoots.

Pythium aphanidermatum is a soil borne plant pathogen. Pythium is a genus in the class Oomycetes, which are also known as water molds. Oomycetes are not true fungi, as their cell walls are made of cellulose instead of chitin, they are diploid in their vegetative state, and they form coenocytic hyphae. Also, they reproduce asexually with motile biflagelette zoospores that require water to move towards and infect a host. Sexually, they reproduce with structures called antheridia, oogonia, and oospores.

Pythium graminicola is a plant pathogen infecting cereals.

<i>Pythium myriotylum</i> Species of single-celled organism

Pythium myriotylum is a soil-borne oomycete necrotroph that has a broad host range, this means that it can infect a wide range of plants.

Pythium volutum is a plant pathogen infecting wheat, barley, and turfgrass. It is known to be sensitive to some of the compounds typically present in selective media commonly used for isolating Pythium spp., so isolation may require alternative methods.

<i>Plasmopara viticola</i> Species of single-celled organism

Plasmopara viticola, the causal agent of grapevine downy mildew, is a heterothallic oomycete that overwinters as oospores in leaf litter and soil. In the spring, oospores germinate to produce macrosporangia, which under wet condition release zoospores. Zoospores are splashed by rain into the canopy, where they swim to and infect through stomata. After 7–10 days, yellow lesions appear on foliage. During favorable weather the lesions sporulate and new secondary infections occur.

<i>Pseudoperonospora humuli</i> Species of single-celled organism

Pseudoperonospora humuli is a plant pathogen that causes downy mildew on hops.

Phytophthora fragariae is a fungus-like (oomycete) plant pathogen that causes red stele, otherwise known as Lanarkshire disease, in strawberries. Symptoms of red stele can include a red core in the roots, wilting of leaves, reduced flowering, stunting, and bitter fruit. The pathogen is spread via zoospores swimming through water present in the soil, released from sporangia.

Phytophthora megakarya is an oomycete plant pathogen that causes black pod disease in cocoa trees in west and central Africa. This pathogen can cause detrimental loss of yield in the economically important cocoa industry, worth approximately $70 billion annually. It can damage any part of the tree, causing total yield losses which can easily reach 20-25%. A mixture of chemical and cultural controls, as well as choosing resistant plant varieties, are often necessary to control this pathogen.

Pythium dissotocum is a plant pathogen infecting strawberry and rice.

<i>Pythium sulcatum</i> Species of single-celled organism

Pythium sulcatum is a chromalveolate plant pathogen infecting carrots. Because this organism was once thought to be a type of fungus, it is still often treated as such.

<i>Phytophthora alni</i> Species of single-celled organism

Phytophthora alni is an oomycete plant pathogen that causes lethal root and collar rot in alders. It is widespread across Europe and has recently been found in North America. This species is believed to have originated relatively recently.

Phytophthora hydropathica is an oomycete plant pathogen that is found in aquatic environments such as irrigation and river water. The pathogen was previously classified as P. drechsleri Dre II before being categorized as its own distinct species. P. hydropathica has been primarily found in association with ornamental plant nurseries. The pathogen has been isolated throughout the Southern United States, as well as internationally in Mexico, Italy, and Spain.

<span class="mw-page-title-main">Pyoluteorin</span> Chemical compound

Pyoluteorin is a natural antibiotic that is biosynthesized from a hybrid nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) pathway. Pyoluteorin was first isolated in the 1950s from Pseudomonas aeruginosa strains T359 and IFO 3455 and was found to be toxic against oomycetes, bacteria, fungi, and against certain plants. Pyoluteorin is most notable for its toxicity against the oomycete Pythium ultimum, which is a plant pathogen that causes a global loss in agriculture. Currently, pyoluteorin derivatives are being studied as an Mcl-1 antagonist in order to target cancers that have elevated Mcl-1 levels.

Black rot on orchids is caused by Pythium and Phytophthora species. Black rot targets a variety of orchids but Cattleya orchids are especially susceptible. Pythium ultimum and Phytophthora cactorum are known to cause black rot in orchids.

References

  1. ↑ Del Castillo Munera, Johanna; Hausbeck, Mary K. (March 2016). "Characterization of Pythium Species Associated With Greenhouse Floriculture Crops in Michigan". Plant Disease. 100 (3): 569–576. doi:10.1094/PDIS-03-15-0296-RE. PMID   30688597.
  2. ↑ Farr, D. F. and Rossman, A. Y. (2014) Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. "Fungal Databases, Systematic Botany and Mycology Laboratory". Archived from the original on 2007-01-30. Retrieved 2007-01-30.
  3. ↑ Dick, M. W. (2001) Straminipilous Fungi. Dordrecht: Kluwer Academic Publishers.
  4. ↑ Schroeder, Kurtis L.; Martin, Frank N.; De Cock, Arthur W. A. M.; Lévesque, C. André; Spies, Christoffel F. J.; Okubara, Patricia A.; Paulitz, Timothy C. (2013). "Molecular Detection and Quantification of Pythium Species: Evolving Taxonomy, New Tools, and Challenges". Plant Disease . 97 (1): 4–20. doi:10.1094/PDIS-03-12-0243-FE. PMID   30722255.
  5. ↑ Fawke, Stuart; Doumane, Mehdi (2015-06-03). "Oomycete Interactions with Plants: Infection Strategies and Resistance Principles". Microbiology and Molecular Biology Reviews. 79 (3): 263–280. doi:10.1128/MMBR.00010-15. PMC   4468149 . PMID   26041933.
  6. ↑ Chethana, K. W. Thilini; et al. (12 June 2021). "Diversity and Function of Appressoria". Pathogens. 10 (6): 746. doi: 10.3390/pathogens10060746 . PMC   8231555 . PMID   34204815.
  7. ↑ De Cal, Antonieta; et al. (2022-02-11). "Editorial: Necrotrophic Fungal Plant Pathogens". Frontiers in Plant Science. 13. doi: 10.3389/fpls.2022.839674 . PMC   8873514 . PMID   35222494.
  8. ↑ Lévesque, C André; et al. (2010). "Genome sequence of the necrotrophic plant pathogen Pythium ultimum reveals original pathogenicity mechanisms and effector repertoire". Genome Biology. 11 (7): R73. doi: 10.1186/gb-2010-11-7-r73 . PMID   20626842.
  9. ↑ van West, Pieter (2003-02-01). "Advances in research on oomycete root pathogens". Physiological and Molecular Plant Pathology. 62 (2): 99–113. doi:10.1016/S0885-5765(03)00044-4.
  10. ↑ "What is Pythium?". plantpath.psu.edu. Department of Plant Pathology and Environmental Microbiology at Penn State University.
  11. ↑ Gams, Walter (2004). "Fungicolous Fungi". Biodiversity of Fungi. pp. 343–392. doi:10.1016/B978-012509551-8/50020-9.
  12. ↑ "Pythium root and stem rot: Pathogen: Pythium spp. (P. aphanidermatum, P. debaryanum, P. ultimum etc.)". Plant and Pest Diagnostics. Michigan State University.
  13. ↑ Moorman, G. Pythium. http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/pythium
  14. ↑ Costa & Loper, 1994. https://www.apsnet.org/publications/mpmi/BackIssues/Documents/1994Articles/Microbe07-440.pdf
  15. ↑ Del Castillo Múnera, Johanna; Quesada-Ocampo, Lina M.; Rojas, Alejandro; Chilvers, Martin I.; Hausbeck, Mary K. (2019). "Population Structure of Pythium ultimum from Greenhouse Floral Crops in Michigan". Plant Disease . 103 (5): 859–867. doi: 10.1094/PDIS-03-18-0394-RE . PMID   30908944.
  16. ↑
    This review...
    Kamoun, Sophien; et al. (2015). "The Top 10 oomycete pathogens in molecular plant pathology". Molecular Plant Pathology . 16 (4): 413–434. doi:10.1111/mpp.12190. PMC   6638381 . PMID   25178392.
    ...cites this research:
    Adhikari, Bishwo N.; Hamilton, John P.; Zerillo, Marcelo M.; Tisserat, Ned; Lévesque, C. André; Buell, C. Robin (2013). "Comparative Genomics Reveals Insight into Virulence Strategies of Plant Pathogenic Oomycetes". PLOS ONE . 8 (10): e75072. Bibcode:2013PLoSO...875072A. doi: 10.1371/journal.pone.0075072 . PMC   3790786 . PMID   24124466.
  17. ↑ Lévesque, C. André; et al. (2010). "Genome sequence of the necrotrophic plant pathogen Pythium ultimum reveals original pathogenicity mechanisms and effector repertoire". Genome Biology . 11 (7): R73. doi: 10.1186/gb-2010-11-7-r73 . PMC   2926784 . PMID   20626842.
  18. ↑ Uzuhashi, Shihomi; Kakishima, Makoto; Tojo, Motoaki (2010). "Phylogeny of the genus Pythium and description of new genera". Mycoscience . 51 (5): 337–365. doi:10.1007/s10267-010-0046-7. S2CID   83622477.
  19. ↑
    This review...
    Hashemi, Maryam; Tabet, Dania; Sandroni, Murilo; Benavent-Celma, Clara; Seematti, Jenifer; Andersen, Christian B.; Grenville-Briggs, Laura J. (2022). "The hunt for sustainable biocontrol of oomycete plant pathogens, a case study of Phytophthora infestans". Fungal Biology Reviews . 40: 53–69. Bibcode:2022FunBR..40...53H. doi: 10.1016/j.fbr.2021.11.003 . S2CID   244889249.
    ...cites this study:
    Liang, Dong; Andersen, Christian Benjamin; Vetukuri, Ramesh R.; Dou, Daolong; Grenville-Briggs, Laura J. (2020). "Horizontal Gene Transfer and Tandem Duplication Shape the Unique CAZyme Complement of the Mycoparasitic Oomycetes Pythium oligandrum and Pythium periplocum". Frontiers in Microbiology . 11: 581698. doi: 10.3389/fmicb.2020.581698 . PMC   7720654 . PMID   33329445.
  20. ↑ Schlatter, Daniel; et al. (November 2017). "Disease Suppressive Soils: New Insights from the Soil Microbiome". Phytopathology. 107 (11): 1284–1297. doi:10.1094/PHYTO-03-17-0111-RVW. PMID   28650266.
  21. ↑ De Corato, Ugo (2020-09-11). "Soil microbiota manipulation and its role in suppressing soil-borne plant pathogens in organic farming systems under the light of microbiome-assisted strategies". Chemical and Biological Technologies in Agriculture. 7: 17. doi: 10.1186/s40538-020-00183-7 .
  22. ↑ Suman, Jarupula; et al. (2022-04-11). "Microbiome as a Key Player in Sustainable Agriculture and Human Health". Frontiers in Soil Science. 2. doi: 10.3389/fsoil.2022.821589 .
  23. ↑ Lutz, Stefanie (2020). "Harnessing the Microbiomes of Suppressive Composts for Plant Protection: From Metagenomes to Beneficial Microorganisms and Reliable Diagnostics". Frontiers in Microbiology. 11: 1810. doi: 10.3389/fmicb.2020.01810 . PMC   7406687 . PMID   32849417.
  24. ↑ Erhart, E.; et al. (1999). "Suppression of Pythium ultimum by Biowaste Composts in Relation to Compost Microbial Biomass, Activity and Content of Phenolic Compounds". Journal of Phytopathology. 147 (5): 299–305. doi:10.1046/j.1439-0434.1999.147005299.x.
  25. ↑ Elad, Yigal (1987). "Possible Role of Competition for Nutrients in Biocontrol of Pythium Damping-Off by Bacteria". Phytopathology. 77 (2): 190. doi:10.1094/Phyto-77-190.
  26. ↑ Chen, Mei-Hsing (June 2012). "Microbial-Induced Carbon Competition in the Spermosphere Leads to Pathogen and Disease Suppression in a Municipal Biosolids Compost". Phytopathology. 102 (6): 588–596. doi:10.1094/PHYTO-08-11-0241. PMID   22352306.
  27. ↑ Inbar, Yoseph (1991-01-01). "Hydrolysis of fluorescein diacetate in sphagnum peat container media for predicting suppressiveness to damping-off caused by Pythium ultimum". Soil Biology and Biochemistry. 23 (5): 479–483. doi:10.1016/0038-0717(91)90013-A.
  28. ↑ Chen, Mei-Hsing (June 2012). "Microbial-Induced Carbon Competition in the Spermosphere Leads to Pathogen and Disease Suppression in a Municipal Biosolids Compost". Phytopathology. 102 (6): 588–596. doi:10.1094/PHYTO-08-11-0241. PMID   22352306.
  29. ↑ Elad, Y (1987). "Possible Role of Competition for Nutrients in Biocontrol of Pythium Damping-Off by Bacteria". Phytopathology. 77 (2): 190. doi:10.1094/Phyto-77-190.
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