Phytophthora infestans
Phytophthora infestans | |
---|---|
Symptom of late blight on the underside of a potato leaf | |
Scientific classification | |
Domain: | Eukaryota |
Clade: | Diaphoretickes |
Clade: | SAR |
Clade: | Stramenopiles |
Phylum: | Oomycota |
Order: | Peronosporales |
Family: | Peronosporaceae |
Genus: | Phytophthora |
Species: | P. infestans
|
Binomial name | |
Phytophthora infestans (
Mont.) de Bary |
Phytophthora infestans is an
Etymology
The genus name Phytophthora comes from the Greek φυτό (phyto), meaning "plant" – plus the Greek φθορά (phthora), meaning "decay, ruin, perish". The species name infestans is the present participle of the Latin verb infestare, meaning "attacking, destroying", from which the word "to infest" is derived. The name Phytophthora infestans was coined in 1876 by the German mycologist Heinrich Anton de Bary (1831–1888).[5][6]
Life cycle, signs and symptoms
The asexual life cycle of Phytophthora infestans is characterized by alternating phases of
People can observe P. infestans produce dark green, then brown then black spots on the surface of potato leaves and stems, often near the tips or edges, where water or dew collects.[9] The sporangia and sporangiophores appear white on the lower surface of the foliage. As for tuber blight, the white mycelium often shows on the tubers' surface.[10]
Under ideal conditions, P. infestans completes its life cycle on potato or tomato foliage in about five days.[7] Sporangia develop on the leaves, spreading through the crop when temperatures are above 10 °C (50 °F) and humidity is over 75–80% for 2 days or more. Rain can wash spores into the soil where they infect young tubers, and the spores can also travel long distances on the wind. The early stages of blight are easily missed. Symptoms include the appearance of dark blotches on leaf tips and plant stems. White mold will appear under the leaves in humid conditions and the whole plant may quickly collapse. Infected tubers develop grey or dark patches that are reddish brown beneath the skin, and quickly decay to a foul-smelling mush caused by the infestation of secondary soft bacterial rots. Seemingly healthy tubers may rot later when in store.
P. infestans survives poorly in nature apart from on its plant hosts. Under most conditions, the hyphae and asexual sporangia can survive for only brief periods in plant debris or soil, and are generally killed off during frosts or very warm weather. The exceptions involve oospores, and hyphae present within tubers. The persistence of viable pathogen within tubers, such as those that are left in the ground after the previous year's harvest or left in cull piles is a major problem in disease management. In particular,
Mating types
The mating types are broadly divided into A1 and A2.[12][13] Until the 1980s populations could only be distinguished by virulence assays and mating types, but since then more detailed analysis has shown that mating type and genotype are substantially decoupled.[14] These types each produce a mating hormone of their own.[13][12] Pathogen populations are grouped into clonal lineages of these mating types and includes:
A1
A1 produces a mating hormone, a diterpene[13] α1.[12] Clonal lineages of A1 include:
- CN-1CN-1, -2, -4, -5, -6, -7, -8 – mtDNA haplotype Ia, China in 1996–97[15]
- CN-3 – Ia, China, 1996–97[15]
- CN-10 – Ia, China, 2004[15]
- CN-11 – IIb, China, 2000 & 2002[15]
- CN01 – IIa, China, 2004–09[15]
- CN03 – Ia/IIb, China, 2004–09[15]
- FAM-1 – (only presumed to be A1), mtDNA haplo Ia subtype HERB-1, Japan, Philippines, India, China, Malaysia, Nepal, present some time before 1950[15]
- IN-1 – Ia, India, Nepal, 1993[15]
- IN-2 – Ia, India, 1993[15]
- JP-2JP-2/SIB-1/RF006 – mtDNA haplo IIa, distinguishable by metalaxyl resistance, Japan, China, Korea, Thailand, 1996–present[15]
- JP-3 – IIa, distinguishable by metalaxyl resistance, Japan, 1996–present[15]
- JP-4 – IIa, distinguishable by metalaxyl resistance, Japan, 1996–present[15]
- KR-1 Zhang sensu Zhang (not to be confused with #KR-1 sensu Gotoh below) – IIa, Korea, 2002–04[15]
- KR_1_A1KR_1_A1 – mtDNA haplo unknown, Korea, 2009–16[15]
- MO-6 – Ia, China, 2004[15]
- NP-1 – Ia, India, Nepal, 1993, 1996–97[15]
- NP-2 – Ia, Nepal, 1997[15]
- NP1 – Ia, Nepal, 1999–2000[15]
- NP2 A1 – (Also A2, see #the A2 type of NP2 below) Ia, Nepal, 1999–2000[15]
- NP3 (not to be confused with #US-1 below) – Ib, Nepal, 1999–2000[15]
- US-1 (not to be confused with #NP3/US-1 above) – Ib,[13][15] China, India, Nepal, Japan, Taiwan, Thailand, Vietnam, 1940–2000[15]
- NP4, 5, 7, and 9 – Ia, Nepal, 1999–2000[15]
- NP6 – mtDNA haplo unknown, Nepal, 1999–2000[15]
- US-11 – IIb, Taiwan, Korea, Vietnam, 1998–2016[15]
- US-16 – IIb, China, 2002 & 2004[15]
- US-17[13] – IIa, Korea, 2003–04[15]
- US-23[14]
- US-24[14]
- 2_A1 – Ia, Indonesia, 2016–19[15]
- T30-4[14]
A2
Discovered by John Niederhauser in the 1950s, in the Toluca Valley in Central Mexico, while working for the Rockefeller Foundation's Mexican Agriculture Program. Published in Niederhauser 1956.[13][15] A2 produces a mating hormone α2.[12] Clonal lineages of A2 include:
- CN02 – See #13_A2/CN02 below
- US-22 – with
- JP-1 – IIa, Japan, Korea, Indonesia, late 1980s–present[15]
- KR-1 Gotoh sensu Gotoh (not to be confused with #KR-1 sensu Zhang above) – IIa, differs from JP-1 by one RG57 band, Korea, 1992[15]
- KR_2_A2 – mtDNA haplo unknown, Korea, 2009–16[15]
- CN-9 – Ia, China, 2001[15]
- NP2 A2 – (Also A1, see #the A1 type of NP2 above) Ia, Nepal, 1999–2000[15]
- NP8 – Ib, Nepal, 1999–2000[15]
- NP10 & 11 – Ia, Nepal, 1999–2000[15]
- TH-1 – Ia, Thailand, China, Nepal, 1994 & 1997[15]
- Unknown – Ib, India, 1996–2003[15]
- BR-1 – Brazil[13]
- US-7[13]
- US-8[13]
- US-14 – IIa, Korea, 2002–03[15]
- 13_A2[16][14][15]/CN02 – Ia, China, India, Bangladesh, Nepal, Pakistan, Myanmar, 2005–19[15]
Self-fertile
A self-fertile type was present in China between 2009 and 2013.[15]
Physiology
Genetics
P. infestans is
The pathogen shows high
Research
Origin and diversity
The highlands of central
Migrations from Mexico to North America or Europe have occurred several times throughout history, probably linked to the movement of tubers.[32][33] Until the 1970s, the A2 mating type was restricted to Mexico, but now in many regions of the world both A1 and A2 isolates can be found in the same region.[13] The co-occurrence of the two mating types is significant due to the possibility of sexual recombination and formation of oospores, which can survive the winter. Only in Mexico and Scandinavia, however, is oospore formation thought to play a role in overwintering.[22][34] In other parts of Europe, increasing genetic diversity has been observed as a consequence of sexual reproduction.[35] This is notable since different forms of P. infestans vary in their aggressiveness on potato or tomato, in sporulation rate, and sensitivity to fungicides.[36] Variation in such traits also occurs in North America, however importation of new genotypes from Mexico appears to be the predominant cause of genetic diversity, as opposed to sexual recombination within potato or tomato fields.[13] In 1976 – due to a summer drought in Europe – there was a potato production shortfall and so eating potatoes were imported to fill the shortfall. It is thought that this was the vehicle for mating type A2 to reach the rest of the world. In any case, there had been little diversity, consisting of the US-1 strain, and of that only one type of: mating type, mtDNA, restriction fragment length polymorphism, and di-locus[clarification needed] isozyme. Then in 1980 suddenly greater diversity and A2 appeared in Europe. In 1981 it was found in the Netherlands, United Kingdom, 1985 in Sweden, the early 1990s in Norway and Finland, 1996 in Denmark, and 1999 in Iceland. In the UK new A1 lineages only replaced the old lineage by end of the '80s, and A2 spread even more slowly, with Britain having low levels and Ireland (north and Republic) having none-to-trace detections through the '90s.[37] Many of the strains that appeared outside of Mexico since the 1980s have been more aggressive, leading to increased crop losses.[13] In Europe since 2013 the populations have been tracked by the EuroBlight network (see links below). Some of the differences between strains may be related to variation in the RXLR effectors that are present.
Disease management
P. infestans is still a difficult disease to control.
If adequate field scouting occurs and late blight is found soon after disease development, localized patches of potato plants can be killed with a desiccant (e.g. paraquat) through the use of a backpack sprayer. This management technique can be thought of as a field-scale hypersensitive response similar to what occurs in some plant-viral interactions whereby cells surrounding the initial point of infection are killed in order to prevent proliferation of the pathogen.
If infected tubers make it into a storage bin, there is a very high risk to the storage life of the entire bin. Once in storage, there isn't much that can be done besides emptying the parts of the bin that contain tubers infected with Phytophthora infestans. To increase the probability of successfully storing potatoes from a field where late blight was known to occur during the growing season, some products can be applied just prior to entering storage (e.g. Phostrol).[42]
Around the world the disease causes around $6 billion of damage to crops each year.[1][2]
Resistant plants
Breeding for resistance, particularly in potato plants, has had limited success in part due to difficulties in crossing cultivated potato to its wild relatives,[38][39][40] which are the source of potential resistance genes.[38][39][40] In addition, most resistance genes only work against a subset of P. infestans isolates, since effective plant disease resistance only results when the pathogen expresses a RXLR effector gene that matches the corresponding plant resistance (R) gene; effector-R gene interactions trigger a range of plant defenses, such as the production of compounds toxic to the pathogen.
Potato and tomato varieties vary in their susceptibility to blight.[35][38][39][40] Most early varieties are very vulnerable; they should be planted early so that the crop matures before blight starts (usually in July in the Northern Hemisphere). Many old crop varieties, such as King Edward potato are also very susceptible but are grown because they are wanted commercially. Maincrop varieties which are very slow to develop blight include Cara, Stirling, Teena, Torridon, Remarka, and Romano. Some so-called resistant varieties can resist some strains of blight and not others, so their performance may vary depending on which are around.[35][38][39][40] These crops have had polygenic resistance bred into them, and are known as "field resistant". New varieties[38][39][40] such as Sarpo Mira and Sarpo Axona show great resistance to blight even in areas of heavy infestation. Defender is an American cultivar whose parentage includes Ranger Russet and Polish potatoes resistant to late blight. It is a long white-skinned cultivar with both foliar and tuber resistance to late blight. Defender was released in 2004.[43]
Genetic engineering may also provide options for generating resistance cultivars. A resistance gene effective against most known strains of blight has been identified from a wild relative of the potato, Solanum bulbocastanum, and introduced by genetic engineering into cultivated varieties of potato.[44] This is an example of cisgenic genetic engineering.[45]
Melatonin in the plant/P. infestans co-environment reduces the stress tolerance of the parasite.[46]
Reducing inoculum
Blight can be controlled by limiting the source of
Compost, soil or potting medium can be heat-treated to kill oomycetes such as Phytophthora infestans. The recommended sterilisation temperature for oomycetes is 120 °F (49 °C) for 30 minutes.[48][49]
Environmental conditions
There are several environmental conditions that are conducive to P. infestans. An example of such took place in the United States during the 2009 growing season. As colder than average for the season and with greater than average rainfall, there was a major infestation of tomato plants, specifically in the eastern states.[50] By using weather forecasting systems, such as BLITECAST, if the following conditions occur as the canopy of the crop closes, then the use of fungicides is recommended to prevent an epidemic.[51]
- A Beaumont Period is a period of 48 consecutive hours, in at least 46 of which the hourly readings of
- A Smith Period is at least two consecutive days where min temperature is 10 °C (50 °F) or above and on each day at least 11 hours when the relative humidity is greater than 90%.
The Beaumont and Smith periods have traditionally been used by growers in the United Kingdom, with different criteria developed by growers in other regions.[53] The Smith period has been the preferred system used in the UK since its introduction in the 1970s.[54]
Based on these conditions and other factors, several tools have been developed to help growers manage the disease and plan fungicide applications. Often these are deployed as part of Decision support systems accessible through web sites or smart phones.
Several studies have attempted to develop systems for real-time detection via flow cytometry or microscopy of airborne sporangia collected in air samplers.[55][56][57] Whilst these methods show potential to allow detection of sporangia in advance of occurrence of detectable disease symptoms on plants, and would thus be useful in enhancing existing Decision support systems, none have been commercially deployed to date.
Use of fungicides
In organic production
In the past,
Control of tuber blight
Ridging is often used to reduce tuber contamination by blight. This normally involves piling soil or mulch around the stems of the potato blight meaning the pathogen has farther to travel to get to the tuber.[63] Another approach is to destroy the canopy around five weeks before harvest, using a contact herbicide or sulfuric acid to burn off the foliage. Eliminating infected foliage reduces the likelihood of tuber infection.
Historical impact
The effect of Phytophthora infestans in Ireland in 1845–52 was one of the factors which caused over one million to starve to death[64] and forced another two million to emigrate from affected countries. Most commonly referenced is the Great Irish Famine, during the late 1840s, from which the Irish population has still not fully recouped. The first recorded instances of the disease were in the United States, in Philadelphia and New York City in early 1843. Winds then spread the spores, and in 1845 it was found from Illinois to Nova Scotia, and from Virginia to Ontario. It crossed the Atlantic Ocean with a shipment of seed potatoes for Belgian farmers in 1845.[65][66] All of the potato-growing countries in Europe were affected, but the potato blight hit Ireland the hardest. Implicated in Ireland's fate was the island's disproportionate dependency on a single variety of potato, the Irish Lumper. The lack of genetic variability created a susceptible host population for the organism[67] after the blight strains originating in Chiloé Archipelago replaced earlier potatoes of Peruvian origin in Europe.[68]
During the First World War, all of the copper in Germany was used for
Since 1941, Eastern Africa has been suffering potato production losses because of strains of P. infestans from Europe.[71]
Late blight (A2 type) has not yet been detected in Australia and strict biosecurity measures are in place. The disease has been seen in China, India and south-east Asian countries.
A large outbreak of P. infestans occurred on tomato plants in the Northeast United States in 2009.[74]
In light of the periodic epidemics of P. infestans ever since its first emergence, it may be regarded as a periodically
References
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- ^ "Taxonomy browser (Phytophthora infestans)". www.ncbi.nlm.nih.gov.
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- ^ Judelson HS, Blanco FA (2005) The spores of Phytophthora: weapons of the plant destroyer. Nature Microbiology Reviews 3: 47–58.
- ^ "Late Blight in Potato". North Dakota State University Agriculture Department. May 2017. Retrieved 2021-11-30.
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Further reading
- Haverkort, A. J; Struik, P. C; Visser, R. G. F; Jacobsen, E (2009), "Applied Biotechnology to Combat Late Blight in Potato Caused by Phytophthora Infestans", S2CID 2850128
- Erwin, Donald C.; Ribeiro, Olaf K. (1996), Phytophthora Diseases Worldwide, ISBN 978-0-89054-212-5
- Lucas, J. A.; Shattock, R. C.; Shaw, D. S.; et al., eds. (1991), Phytophthora, ISBN 978-0-521-40080-0
- Haverkort, A. J.; Boonekamp, P. M; Hutten, R.; Jacobsen, E; Lotz, L.; Kessel, G.; Van der Vossen, E.; et al. (2008), "Societal costs of late blight in potato and prospects of durable resistance through cisgenic modification", S2CID 19487540
- Grünwald, N. J.; Flier, W. G. (2005). "The Biology of Phytophthora infestans at Its Center of Origin". PMID 16078881.
- Govers, Francine; Gijzens, Mark (2006), "Phytophthora Genomics: The Plant-Destroyer's Genome Decoded", PMID 17153913
- Nowicki, Marcin; et al. (17 August 2011), "Potato and tomato late blight caused by Phytophthora infestans: An overview of pathology and resistance breeding", PMID 30731850
- Bruhn, J. A.; Fry, W. E. (17 November 1980), "Analysis of potato late blight epidemiology by simulation modeling" (PDF), Phytopathology, 71 (6): 612–616,
- Yoshida, Kentaro; et al. (2013). "Rise and fall of the Phytophthora infestans lineage that triggered the Irish potato famine". eLife. 2 (in press): e00731. PMID 23741619.
- Goss, E. M.; Tabima, J. F.; Cooke, D. E. L.; Restrepo, S.; Fry, W. E.; Forbes, G. A.; Fieland, V. J.; Cardenas, M.; Grünwald, N. J. (2014). "The Irish potato famine pathogen Phytophthora infestans originated in central Mexico rather than the Andes". Proceedings of the National Academy of Sciences. 111 (24): 8791–96. PMID 24889615.
- Martin, Michael D.; et al. (2013). "Reconstructing genome evolution in historic samples of the Irish potato famine pathogen". Nature Communications. 4: 2172. PMID 23863894.
- Martin, Michael D.; et al. (2016). "Genomic characterization of a South American Phytophthora hybrid mandates reassessment of the geographic origins of Phytophthora infestans". PMID 26576850.
- Omid, Shir Ahmad; . Retrieved 2021-11-15.
External links
- USAblight A National Web Portal on Late Blight
- International Potato Center
- Online Phytophtora bibliography
- EuroBlight a potato blight network in Europe
- USDA-BARC Phytophthora infestans page
- Organic Alternatives for Late Blight Control in Potatoes, from ATTRA Archived 2020-09-25 at the Wayback Machine
- Google Map of Tomato Potato Blight Daily Risk across NE USA
- Species Profile – Late Blight (Phytophthora infestans), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Late Blight.
- Continuing education lesson created by The American Phytopathological Society
- entry on Late Blight by PlantVillage