Plasmopara halstedii

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Plasmopara halstedii
Plasmopara halstedii R.H. 10.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Stramenopiles
Phylum: Oomycota
Order: Peronosporales
Family: Peronosporaceae
Genus: Plasmopara
Species:
P. halstedii
Binomial name
Plasmopara halstedii
(Farl.) Berl. & De Toni, (1888)
Synonyms

Peronospora halstediiFarl., (1882)

Plasmopara halstedii is a plant pathogen infecting sunflowers. The species is one of many pathogens commonly referred to as downy mildew. [1] P. halstedii originated in North America.

Contents

Plasmopara halstedii oospores produce a thin wall which are resistant structures, sexually produced that are essential for its continuation. After entering an area, the eradication of the pathogen is difficult due to the formation of oospores, which can remain viable in soil for many years. [2]

Hosts and symptoms

Plasmopara halstedii is an obligate biotroph that attacks the flowering plants of the family Asteraceae, found to infect the genus’ Helianthus, Bidens, Artemisia, and Xanthium. The pathogen has the strongest impact on Helianthus, degrading flower yields in the species H. argophyllus, H. debilis, H. petiolaris and H. annuus . [3] H. annuus, the common sunflower, is also the most common host of P. halstedii. Xanthium strumarium , [4] the common cocklebur, and Ambrosia artemisiifolia , [5] or ragweed, have been shown to act as significant wild hosts.

Plasmopara halstedii causes significant yield losses due to the production of infertile sunflowers. Infertility due to P. halstedii is a result of sporulation on the flowering bodies as well as seed damping off due to root infection. [3] [6] Other symptoms include plant stunting, chlorosis, root browning and alteration of secondary metabolism of infected plants. [7]

As an oomycete, P. halstedii releases motile zoospores as secondary inoculum. In these cases, secondary infection symptoms are much less severe than primary symptoms. [8] A sign of the disease is the “typical downy appearance” resulting from sporulation on the bottom surface of the leaves. [8] [9]

Detection

Systemically infected sunflower plants may have some degree of stunting and the leaves show pale green or chlorotic mottling which spreads along the main veins and over the lamella.

Disease cycle

Plasmopara halstedii is a plant pathogenic oomycete, capable of overwintering in soil due to survival structures called oospores. For this reason, P. halstedii is a soil borne pathogen infecting the roots of the host plant. [10] Oospores have the potential to live in soil up to 10 years, [9] while oospore germination takes 10–30 days. [11] Germination length depends on environmental condition and typically occurs in the spring. [11] The germinating oospores form zoosporangia that release motile zoospores that germinate upon contact with root exudates. [12]

After primary infection, zoospores serve as a main source of inoculum throughout the rest of the season. [13] Zoospores germinate in about two hours and have two means of infection: direct penetration of the root through the use of an appresorium or infection due to an already present wound. Hyphae extend throughout the intercellular space, forming parasitic haustoria. The pathogen breaks through the surface of leaves and flowering structures through stomata. Asexual reproduction structures, called zoosporangiaphores, form at these sites. These structures release zoosporangia containing zoospores to other plants, the primary means of dissemination. [3]

Sexual reproduction be either homothallic or heterothallic. Homothallic reproduction is characterized by the fusion of the asexual oogonium and antheridium. This fusion leads to the formation and release of sexual oospores, the primary inoculum for the next season. Heterothallic sexual reproduction is the fusion of sexual cells from two separate organisms, leading to "outcrossing". [11] [14]

Management and control

Once the pathogen has been detected in an area, management is essential, as P. halstedii is nearly impossible to eradicate. Between long-surviving resting spores and high levels of secondary inoculum, P. halstedii can infect from 50% to 95% of sunflower yields in a single season. [6]

Resistant sunflower strains are available, as two types of dominant major resistance genes have been identified, denoted as Pl. [3] Type 1 resistance lacks infection above the base of the hypocotyl. Type 2 is characterized by a weak infection, with sporulation never reaching the upper region of the host. [3] Resistant genes have been overcome in the past as the pathogen evolves and mutates, suggesting that resistance may not give the best results. [15] However, due to the constant search for resistant sources from wild Helianthus, the gene pool of cultivars is frequently being used to produce new, commercially resistant strains. [16] [17]

Seed treatment has been shown to be effective in controlling the disease, as the establishment of P. halstedii in an area of soil is nearly irreversible. The compounds metalaxyl and oxadixyl have been shown to protect seeds in the case of infection, and treatments containing these compounds are commercially available. [18] Fungicides seed dressings of this nature have also been shown to give significant control over the pathogen. [19] However, some strains of P. halstedii have begun to show resistance to metalaxyl-based fungicides, reported in multiple countries. [15] [20] Alternate forms of resistance are being developed for the future, including the use of biological antagonists [16] and defense-related proteins. [21]

Australia is the leader in pest control of P. halstedii. In Australia, any imported seed is subject to hot-water treatment, fungicide dusting and monitoring for up to 3 years. [22]

Related Research Articles

<span class="mw-page-title-main">Downy mildew</span> Name for several species of oomycete

Downy mildew refers to any of several types of oomycete microbes that are obligate parasites of plants. Downy mildews exclusively belong to the Peronosporaceae family. In commercial agriculture, they are a particular problem for growers of crucifers, grapes and vegetables that grow on vines. The prime example is Peronospora farinosa featured in NCBI-Taxonomy and HYP3. This pathogen does not produce survival structures in the northern states of the United States, and overwinters as live mildew colonies in Gulf Coast states. It progresses northward with cucurbit production each spring. Yield loss associated with downy mildew is most likely related to soft rots that occur after plant canopies collapse and sunburn occurs on fruit. Cucurbit downy mildew only affects leaves of cucurbit plants.

<span class="mw-page-title-main">Peronosporaceae</span> Family of water moulds

Peronosporaceae are a family of water moulds that contains 21 genera, comprising more than 600 species. Most of them are called downy mildews.

Aphanomyces euteiches is a water mould, or oomycete, plant pathogen responsible for the disease Aphanomyces root rot. The species Aphanomyces euteiches can infect a variety of legumes. Symptoms of the disease can differ among hosts but generally include reduced root volume and function, leading to stunting and chlorotic foliage. Aphanomyces root rot is an important agricultural disease in the United States, Europe, Australia, New Zealand, and Japan. Management includes using resistant crop varieties and having good soil drainage, as well as testing soil for the pathogen to avoid infected fields.

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

Phytophthora medicaginis is an oomycete plant pathogen that causes root rot in alfalfa and chickpea. It is a major disease of these plants and is found wherever they are grown. P. medicaginis causes failure of stand establishment because of seedling death. Phytophthora medicaginis is part of a species complex with Phytophthora megasperma.

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.

Pythium ultimum is a plant pathogen. It causes damping off and root rot diseases of hundreds of diverse plant hosts including corn, soybean, potato, wheat, fir, and many ornamental species. P. ultimum belongs to the peronosporalean lineage of oomycetes, 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.

<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.

Sclerophthora macrospora is a protist plant pathogen of the class Oomycota. It causes downy mildew on a vast number of cereal crops including oats, rice, maize, and wheat as well as varieties of turf grass. The common names of the diseases associated with Sclerophthora macrospora include "crazy top disease" on maize and yellow tuft disease on turf grass. The disease is present all over the world, but it is especially persistent in Europe.

<i>Diaporthe helianthi</i> Species of fungus

Diaporthe helianthi is a fungal pathogen that causes Phomopsis stem canker of sunflowers. In sunflowers, Phomopsis helianthi is the causative agent behind stem canker. Its primary symptom is the production of large canker lesions on the stems of sunflower plants. These lesions can eventually lead to lodging and plant death. This disease has been shown to be particularly devastating in southern and eastern regions of Europe, although it can also be found in the United States and Australia. While cultural control practices are the primary method of controlling for Stem Canker, there have been a few resistant cultivars developed in regions of Europe where the disease is most severe.

Aphanomyces cochlioides is a plant pathogen that can affect commodity crops like spinach, Swiss chard, beets and related species. In spinach the pathogen is responsible for the black root "rot" that can damage plants.

<i>Bremia lactucae</i> Species of single-celled organism

Bremia lactucae is a plant pathogen. This microorganism causes a disease of lettuce denominated as downy mildew. Some other strains can be found on 36 genera of Asteraceae including Senecio and Sonchus. Experiments using sporangia from hosts do not infect lettuce and it is concluded that the fungus exists as a quantity of host-specific strains. Wild species, such as Lactuca serriola, or varieties of Lactuca can hold strains that infect lettuce, but these pathogens are not sufficiently common to seriously infect the plant.

<i>Peronospora manshurica</i> Species of single-celled organism

Peronospora manshurica is a plant pathogen. It is a widespread disease on the leaves of soybeans and other crop plants. The fungi is commonly referred to as downy mildew, "leafspot", or "leaf-spot".

<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 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.

Peronosclerospora sorghi is a plant pathogen. It is the causal agent of sorghum downy mildew. The pathogen is a fungal-like protist in the oomycota, or water mold, class. Peronosclerospora sorghi infects susceptible plants though sexual oospores, which survive in the soil, and asexual sporangia which are disseminated by wind. Symptoms of sorghum downy mildew include chlorosis, shredding of leaves, and death. Peronosclerospora sorghi infects maize and sorghum around the world, but causes the most severe yield reductions in Africa. The disease is controlled mainly through genetic resistance, chemical control, crop rotation, and strategic timing of planting.

Alternaria helianthi is a fungal plant pathogen causing a disease in sunflowers known as Alternaria blight of sunflower.

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

Pseudoperonospora cubensis is a species of water mould known for causing downy mildew on cucurbits such as cantaloupe, cucumber, pumpkin, squash and watermelon. This water mould is an important pathogen of all these crops, especially in areas with high humidity and rainfall, such as the eastern United States. In most years the disease is an annual, late-season problem on squash and pumpkin in the eastern and central United States, however, since 2004 it has become one of the most important diseases in cucumber production. Considered a highly destructive foliar disease of cucurbits, successful breeding in the mid-twentieth century provided adequate control of downy mildew in cucumber without the use of fungicides. The resurgence in virulence has caused growers great concern and substantial economic losses, while downy mildew in other cucurbit crops continues to be a yearly hindrance.

<i>Peronospora destructor</i> Species of single-celled organism

Peronospora destructor is a plant pathogen. It causes downy mildew on leaves of cultivated and wild Allium. Allium cepa is most often affected, while Allium schoenoprasum (chives) and Allium porrum (leek) are only occasionally affected.

References

  1. ↑ Friskop, Andrew; Markell, Sam; Gulya, Tom (2009). "Downy Mildew of Sunflower" (PDF). Sunflower Publications. Fargo, North Dakota: North Dakota State University Extension Service. Retrieved 4 March 2016.{{cite book}}: |website= ignored (help)
  2. ↑ Maria Villas Bôas de Campos Leite, Regina; Assis Henning, Ademir; Rosa Rodrigues, Silvia; Fernandes de Oliveira, Marcelo (December 2007). "Detecção e variabilidade de Plasmopara halstedii no Brasil e avaliação da resistência de genótipos de girassol ao míldio" [Detection and variability of Plasmopara halstedii in Brazil and resistance of sunflower genotypes to downy mildew]. Summa Phytopathologica. ISSN   0100-5405.
  3. 1 2 3 4 5 Gascuel, Quentin; Martinez, Yves; Boniface, Marie-Claude; Vear, Felicity; Pichon, Magalie; Godiard, Laurence (2015). "The sunflower downy mildew pathogen Plasmopara halstedii". Molecular Plant Pathology. 16 (2): 109–122. doi:10.1111/mpp.12164. PMC   6638465 . PMID   25476405.
  4. ↑ Komjáti H, Walcz I, Virányi F, Zipper R, Thines M, Spring O, 2007. Characteristics of a Plasmopara angustiterminalis isolate from Xanthium strumarium. European Journal of Plant Pathology, 119(4):421-428. http://springerlink.metapress.com/link.asp?id=100265
  5. ↑ Walcz I, Bogßr K, Virßnyi F, 2000. Study on an Ambrosia isolate of Plasmopara halstedii. Helia, 23(33):19-24; 8 ref.
  6. 1 2 Sackston, W.E. (1981) Downy mildew of sunflower. In: The Downy Mildews (Spencer, D.M., ed.), pp. 545–575.London: Academic Press.
  7. ↑ Mouzeyar, S., Tourvieille de Labrouhe, D. and Vear, F. (1993) Histopathological studies of resistance of sunflower (Helianthus annuus L.) to downy mildew (Plasmopara halstedii). J. Phytopathol. 139, 289–297.
  8. 1 2 Gulya, T.J., Tourvieille de Labrouhe, D., Masirevic, S., Penaud, A., Rashid, K. and Viranyi, F. (1998) Proposal for the standardized nomenclature and identification of races of Plasmopara halstedii (sunflower downy mildew). In: Sunflower Downy Mildew Symposium, Proceedings of Sunflower Downy Mildew Symposium, International Sunflower Association Symposium III, Fargo, ND, USA, pp. 130–136.
  9. 1 2 Harveson, R. M. (May 2011). "Downy Mildew of Sunflower in Nebraska" (PDF).
  10. ↑ Ioos, R., Laugustin, L., Rose, S., Tourvieille, J. and de Labrouhe, D.T. (2007) Development of a PCR test to detect the downy mildew causal agent Plasmopara halstedii in sunflower seeds. Plant Pathol.56, 209–218.
  11. 1 2 3 Spring, O. and Zipper, R. (2000) Isolation of oospores of sunflower downy mildew, Plasmopara halstedii, and microscopical studies on oospore germination. J. Phytopathol. 148, 227–231.
  12. ↑ Harveson, R. M; Markell, S. G; Block, C. C; Gulya, T. J, eds. (2016). Compendium of Sunflower Diseases and Pests. pp. 18–20. doi:10.1094/9780890545096. ISBN   978-0-89054-509-6.
  13. ↑ Grenville-Briggs, L.J. and Van West, P. (2005) The biotrophic stages of oomycete–plant interactions. Adv. Appl. Microbiol.57, 217–243.
  14. ↑ Spring, O. (2000) Homothallic sexual reproduction in Plasmopara halstedii, the downy mildew of sunflower.Helia, 23, 19–26.
  15. 1 2 Gulya, T.J.; Sackston, W.E.; Virányi, F.; Masirevic, S.; Rashid, K.Y. (1991) New races of the sunflower downy mildew pathogen (Plasmopara halstedii) in Europe and North and South America. Journal of Phytopathology 132, 303-311.
  16. 1 2 Sackston WE, 1992. On a treadmill: breeding sunflowers for resistance to disease. Annual Review of Phytopathology, 30:529-551; 123 ref.
  17. ↑ Skoric D, 1994. Sunflower breeding for resistance to dominant diseases. In: Proceedings of the EUCARPIA Oil and Protein Crops Section, Symposium on Breeding of Oil and Protein Crops, Albena, Bulgaria, 30-48.
  18. ↑ Achbani EH, Lamrhari A, Serrhini MN, Douira A, Tourvieille de Labrouche D, 1999. Evaluation of the efficacy of seed treatments against Plasmopara halstedii. Bulletin OEPP, 29(4):443-449; 15 ref.
  19. ↑ Oros G, Viranyi F, 1987. Glasshouse evaluation of fungicides for the control of sunflower downy mildew (Plasmopara halstedii). Annals of Applied Biology, 110(1): 53-63.
  20. ↑ Lafon S, Penaud A, Walser P, De Guenin M-Ch, Molinero V, Mestres R, Tourvieille D, 1996. Le mildiou du tournesol toujour sou surveillance. Phytoma, 484:35-36.
  21. ↑ Nandeeshkumar P, Ramachandra K, Prakash HS, Niranjana SR, Shetty H, 2008. Induction of resistance against downy mildew on sunflower by rhizobacteria, 3(4):255-262.
  22. ↑ Anon. (1981) Sunflower downy mildew. Plant Quarantine Leaflet No. 13. Commonwealth Department of Health, Canberra, Australia.

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