Zebra chip, also known as papa manchada and papa rayada, is a disease in potatoes putatively caused by an alphaproteobacterium " Candidatus Liberibacter solanacearum", which is vectored by the potato psyllid. [2] [3] When fried, potato tubers from infected plants develop unsightly black lines resembling the stripes of zebras that render the chips unsellable. [4] Additionally, striped sections of chips frequently burn and caramelize, resulting in a bitter flavor. No health risks have been connected with consumption of infected potato chips. [4]
Zebra chip was first identified in 1994 near Saltillo, Mexico, and was originally named papa manchada (stained potato). [5] In the early 1990s, Texas potato farms reported afflictions, though the disease was not identified in the state until 2000. [3] [6] Since then, zebra chip has been reported in the U.S. states of Arizona, California, Colorado, Idaho, Oregon, Kansas, Nebraska, and New Mexico. Since 2000, Guatemala reported a disease known as papa rayada (striped potato), which has been identified as zebra chip. [5] [7] New Zealand's first suspected case of zebra chip occurred in May 2008, when an Auckland greenhouse reported similar symptoms. In October 2012, the Australian government reviewed the importation of potatoes from New Zealand [8] because of the presence of the disease in the country. [4] Eastern Europe and southern Russia may also be currently experiencing the disease. [5]
An experiment carried out by scientists from the USDA Agricultural Research Service's Vegetable and Forage Crops Research Unit indicates that creating chips from infected raw potatoes increases the visibility of zebra chip. [4] The researchers correlated the presence of the tomato potato psyllid Bactericera cockerelli , which infests both potatoes and tomatoes, to the presence of zebra chip. [1] One of the scientists also reported that targeting the suspected hosts, psyllids, with insect control measures proved effective at stopping the disease. Though early reports suggested the cause might be a bacterium, namely Candidatus Liberibacter, studies have not been able to consistently associate any phytoplasmas with the disease. [7] [9]
It is currently postulated that the potato psyllid [10] acts as a vector for the disease's unknown pathogen, as it is the only organism consistently associated with zebra chip. [7] In 2008, New Zealand researchers investigating a B. cockerelli infestation in tomato and pepper greenhouses discovered a new bacterial species Candidatus Liberibacter solanacearum [11] whose genetic markers were found to be identical to those found at two potato farms in Texas. This bacterium is related to Candidatus Liberibacter spp., which cause citrus greening disease in citrus plants. [4]
There are currently three haplotypes of the bacterium ‘Candidatus Liberibacter solanacearum’ that infect potato: haplotypes A, B, and F. Haplotype F was the latest to be discovered in Oregon's Klamath Basin. [12]
Scientists suggest that zebra chip's namesake sign is caused by the conversion of potato starch to water-soluble sugar, causing the stripes to appear upon cooking. [6] Another study suggests that discoloration is due to enzymatic browning involving a polyphenol oxidase. [13]
Many zebra chip symptoms are evident before the potato is even harvested; foliar signs include chlorosis, leaf scorching, swollen nodes, vascular tissue browning, and curled leaves. Subterranean signs include collapsed stolons, enlarged lenticels, vascular tissue browning, medullary ray discoloration, and necrotic flecking of tuber tissue. The University of Nebraska cites the subterranean signs as the unique identification of zebra chip from all other known potato diseases. Zebra chip has been noted among potato disease experts as being unusually complex, and possibly the product of two separate pathogens, as has been discovered before for basses richesses (SBR) and spraing. [5] [14]
Partners of the CABI-led programme, Plantwise, including the Secretaría de Agricultura y Ganadería (SAG) in Honduras provide several recommendations for managing Zebra chip in potato. These include; reducing soil acidity before sowing, using certified seeds and removing any diseased plants. They also recommend practicing crop rotation to prepare the soil and not to sow any other hosts for 3 years so that bacteria on the soil will die. [15]
Much of the economic impact of zebra chip stems not from edibility issues, but cosmetic ones; while not deemed hazardous to one's health, infected potatoes are visually unappealing and will not be purchased by processing companies. From this refusal stems most of the other costs, including lost wages from processing fewer potatoes. [4] [16]
After the initial June 2008 discovery of the new species of Candidatus Liberibacter solanacearum, 14 countries implemented bans on various New Zealand crops and New Zealand withdrew export certification for tomatoes and capsicums as a precautionary measure. New Zealand's export certification has since been reinstated and some countries have indicated they will accept fruit again. Fiji stopped imports from New Zealand of potatoes, tomatoes, and capsicum, but ended the bans in July 2008. While French Polynesia did not ban any crops immediately, its restrictions were deemed unreasonable by New Zealand and all potato and capsicum exports to French Polynesia were halted. Having previously blocked imports of potatoes, Australia expanded that ban to include capsicum, tomatoes, cape gooseberries, tomatillos, and five other crops. [17]
Though it may be too early to estimate the economic impact of these bans, New Zealand's tomato and capsicum exports combined earn the nation over NZ$41 million (about US$30 million, August 2008) annually. [2]
Some farms in Texas have reported losses exceeding US$2 million in both 2005 and 2006, with about 35-40% of Texas potato farm acreage affected. Using IMPLAN, a macroeconomic impact model based upon average annual potato production in the state from 2003 to 2005, the total estimated lost product amounted to 38% of all potato production totaling $25.86 million. The economic impact reached beyond just the crop, however, resulting in estimates of total business losses of $125 million and total job losses of 970. [3] The Center for North American Studies' report also predicted that if the disease is not stopped soon, South Texas could lose all of its potato crop and abandon farming of potatoes. [3]
In the Pacific Northwest, where over 50% of the U.S. potatoes are grown, it was estimated to cost 11 million U.S. dollars to control the psyllid in a year. [18]
European Union
According to European Commission Delegated Regulation of 1 August 2019 Candidatus Liberibacter spp. is officially listed as a quarantine pest in European Union. [19] According to a study of 2012, the annual losses due to the pathogen were calculated at more than €220 million. [20]
This article incorporates text from a free content work. Licensed under CC-BY-SA( license statement/permission ). Text taken from Plantwise Factsheets for Farmers: The bacteria in potato , Mariela Lilibeth Lara, CABI.
Citrus production encompasses the production of citrus fruit, which are the highest-value fruit crop in terms of international trade. There are two main markets for citrus fruit:
Psyllidae, the jumping plant lice or psyllids, are a family of small plant-feeding insects that tend to be very host-specific, i.e. each plant-louse species only feeds on one plant species (monophagous) or feeds on a few closely related plants (oligophagous). Together with aphids, phylloxerans, scale insects and whiteflies, they form the group called Sternorrhyncha, which is considered to be the most "primitive" group within the true bugs (Hemiptera). They have traditionally been considered a single family, Psyllidae, but recent classifications divide the group into a total of seven families; the present restricted definition still includes more than 70 genera in the Psyllidae. Psyllid fossils have been found from the Early Permian before the flowering plants evolved. The explosive diversification of the flowering plants in the Cretaceous was paralleled by a massive diversification of associated insects, and many of the morphological and metabolic characters that the flowering plants exhibit may have evolved as defenses against herbivorous insects.
Physalis peruviana is a species of plant in the nightshade family (Solanaceae) native to Chile and Peru. Within that region, it is called aguaymanto, uvilla or uchuva, in addition to numerous indigenous and regional names. In English, its common names include Cape gooseberry, goldenberry and Peruvian groundcherry.
Citrus greening disease or yellow dragon disease is a disease of citrus caused by a vector-transmitted pathogen. The causative agents are motile bacteria, Liberibacter spp. The disease is transmitted by the Asian citrus psyllid, Diaphorina citri, and the African citrus psyllid, Trioza erytreae, also known as the two-spotted citrus psyllid. It has no known cure. It has also been shown to be graft-transmissible.
Xylella fastidiosa is an aerobic, Gram-negative bacterium of the genus Xylella. It is a plant pathogen, that grows in the water transport tissues of plants and is transmitted exclusively by xylem sap-feeding insects such as sharpshooters and spittlebugs. Many plant diseases are due to infections of X. fastidiosa, including bacterial leaf scorch, oleander leaf scorch, coffee leaf scorch (CLS), alfalfa dwarf, phony peach disease, and the economically important Pierce's disease of grapes (PD), olive quick decline syndrome (OQDS), and citrus variegated chlorosis (CVC). While the largest outbreaks of X. fastidiosa–related diseases have occurred in the Americas and Europe, this pathogen has also been found in Taiwan, Israel, and a few other countries worldwide.
Pseudomonas cichorii is a Gram-negative soil bacterium that is pathogenic to plants. It has a wide host range, and can have an important economical impact on lettuce, celery and chrysanthemum crops. P. cichorii was first isolated on endives, from which it derives its name. It produces 6-aminopenicillanic acid. Based on 16S rRNA analysis, P. cichorii has been placed in the P. syringae group.
Ralstonia solanacearum is an aerobic non-spore-forming, Gram-negative, plant pathogenic bacterium. R. solanacearum is soil-borne and motile with a polar flagellar tuft. It colonises the xylem, causing bacterial wilt in a very wide range of potential host plants. It is known as Granville wilt when it occurs in tobacco. Bacterial wilts of tomato, pepper, eggplant, and Irish potato caused by R. solanacearum were among the first diseases that Erwin Frink Smith proved to be caused by a bacterial pathogen. Because of its devastating lethality, R. solanacearum is now one of the more intensively studied phytopathogenic bacteria, and bacterial wilt of tomato is a model system for investigating mechanisms of pathogenesis. Ralstonia was until recently classified as Pseudomonas, with similarity in most aspects, except that it does not produce fluorescent pigment like Pseudomonas. The genomes from different strains vary from 5.5 Mb up to 6 Mb, roughly being 3.5 Mb of a chromosome and 2 Mb of a megaplasmid. While the strain GMI1000 was one of the first phytopathogenic bacteria to have its genome completed, the strain UY031 was the first R. solanacearum to have its methylome reported. Within the R. solanacearum species complex, the four major monophyletic clusters of strains are termed phylotypes, that are geographically distinct: phylotypes I-IV are found in Asia, the Americas, Africa, and Oceania, respectively.
Alternaria solani is a fungal pathogen that produces a disease in tomato and potato plants called early blight. The pathogen produces distinctive "bullseye" patterned leaf spots and can also cause stem lesions and fruit rot on tomato and tuber blight on potato. Despite the name "early," foliar symptoms usually occur on older leaves. If uncontrolled, early blight can cause significant yield reductions. Primary methods of controlling this disease include preventing long periods of wetness on leaf surfaces and applying fungicides. Early blight can also be caused by Alternaria tomatophila, which is more virulent on stems and leaves of tomato plants than Alternaria solani.
Tobacco necrosis virus A (TNV) is a plant pathogenic virus of the family Tombusviridae.
Bacterial wilt is a complex of diseases that occur in plants such as Cucurbitaceae and Solanaceae and are caused by the pathogens Erwinia tracheiphila, a gram-negative bacterium, or Curtobacterium flaccumfaciens pv. flaccumfaciens, a gram-positive bacterium. Cucumber and melon plants are most susceptible, but squash, pumpkins, and gourds may also become infected.
Bactericera cockerelli, also known as the potato psyllid, is a species of psyllid native to southern North America. Its range extends from Central America north to the American Pacific Northwest and parts of Manitoba, in Canada. It is restricted to the western part of the continent. As its name suggests, it is commonly found on potato and tomato crops, but has a species range that encompasses over 40 species of solanaceous plants and as many as 20 genera. Breeding hosts are generally recognised as being restricted primarily to Solanaceae, including important crop and common weed species, and a few species of Convolvulaceae, including bindweed and sweet potato. On some plants, especially potato, feeding of the nymphs causes a condition called psyllid yellows, presumed to be the result of a toxin. Both nymphs and adults can transmit the bacterium Candidatus Liberibacter.
Psyllid yellows is a disease of potatoes infested by the potato/tomato psyllid, Bactericera cockerelli. The symptoms are a marked yellowing of the leaves, an upright appearance to the leaves, with severe cases resulting in early death of the plant. Tuber initiation and growth is affected. Many small tubers are formed, frequently misshaped. In some cases, the tubers seem to have lost sprouting inhibition and have begun sprouting before harvest. At later stages, the tubers sprout weakly, if at all.
Diaphorina citri, the Asian citrus psyllid, is a sap-sucking, hemipteran bug in the family Psyllidae. It is one of two confirmed vectors of citrus greening disease. It has a wide distribution in southern Asia and has spread to other citrus growing regions.
Trioza erytreae, the African citrus psyllid, is a sap-sucking insect, a hemipteran bug in the family Triozidae. It is an important pest of citrus, being one of only two known vectors of the serious citrus disease, huanglongbing or citrus greening disease. It is widely distributed in Africa. The other vector is the Asian citrus psyllid, Diaphorina citri.
Liberibacter is a genus of Gram-negative bacteria in the Rhizobiaceae family. Detection of the liberibacteria is based on PCR amplification of their 16S rRNA gene with specific primers. Members of the genus are plant pathogens mostly transmitted by psyllids. The genus was originally spelled Liberobacter.
Melanostoma fasciatum is a species of hoverfly found in New Zealand, where it is common in agricultural fields and gardens. Locally dense populations of this hoverfly species might effectively reduce pest infestation. Hence, they are perhaps an effective natural and non-toxic bioagent that may control and reduce aphid and small caterpillar populations.
Beet vascular necrosis and rot is a soft rot disease caused by the bacterium Pectobacterium carotovorum subsp. betavasculorum, which has also been known as Pectobacterium betavasculorum and Erwinia carotovora subsp. betavasculorum. It was classified in the genus Erwinia until genetic evidence suggested that it belongs to its own group; however, the name Erwinia is still in use. As such, the disease is sometimes called Erwinia rot today. It is a very destructive disease that has been reported across the United States as well as in Egypt. Symptoms include wilting and black streaks on the leaves and petioles. It is usually not fatal to the plant, but in severe cases the beets will become hollowed and unmarketable. The bacteria is a generalist species which rots beets and other plants by secreting digestive enzymes that break down the cell wall and parenchyma tissues. The bacteria thrive in warm and wet conditions, but cannot survive long in fallow soil. However, it is able to persist for long periods of time in the rhizosphere of weeds and non-host crops. While it is difficult to eradicate, there are cultural practices that can be used to control the spread of the disease, such as avoiding injury to the plants and reducing or eliminating application of nitrogen fertilizer.
Māori potatoes or taewa are varieties of potato cultivated by Māori people, especially those grown before New Zealand was colonised by the British.
Ralstonia pseudosolanacearum is a soil-borne bacterium. It is a vascular phytopathogen that infects host plants through the root system causing wilting disease that causes loss in a wide range of crops. R. pseudosolanacearum is Gram negative and was originally identified as Ralstonia solanacearum, however, in 2014 Safni et al. proposed a taxonomic revision of the Ralstonia solanacearum species complex to reclassify phylotype strains, including R. pseudosolanacearum.
Viral diseases of potato are a group of diseases caused by different types of Viruses that affect potato crops worldwide and, although they do not affect human or animal health since they are viruses that only infect vegetables, they are a source of great economic losses annually. About 28 viruses have been reported infecting potato crops. However, potato virus X (PVX), potato virus Y (PVY), and potato leafroll virus (PLRV) are the most important viruses worldwide. Some others are of economic importance only in some regions. Such is the case of potato virus M (PVM) in some Asian and European countries.
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