|Golden nematode, Potato cyst nematode||Classification||Hosts|
|Morphology and Anatomy||Life Cycle|
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|Return to Heteroderidae Menu||Feeding||References|
Until Stone (1973a) described a second cyst-nematode species (G. pallida) that attacked potatoes, G. rostochiensis included both species. G. pallida is very similar to G. rostochiensis, but differs from it in several important morphological characters. Also, G. pallida appears to be more aggressive than G. rostochiensis and is more responsive to host root diffusate. When both species are present, G. pallida reproduces to a greater extent and predominates population levels (Devine and Jones, 2003). The problem is exacerbated when potatoes resistant only to G. rostochiensis are grown. Available cultivars have only partial resistance to G. pallida and do not prevent its increase. Globodera pallida is progressively replacing G. rostochiensis in Britain (Trudgill et al., 2003). The genus Globodera was established for the round cyst nematodes by Behrens (1975).
Females: Globodera rostochiensis females form cysts, which are the bodies of dead female nematodes, which protect the eggs. Body globose, spheroid, with a short neck and no terminal cone.
New cysts are glossy-brown, rounded, and have a projecting neck (Stone, 1973b).
The stylet is straight to slightly curved and stylet knobs are rounded and sloped posteriorly.
Ovaries are paired and large.
Vulval area circumfenestrate; superficial tubercles near vulva. No anal fenestration, but anus and vulva lying both in a "vulval basin." Underbridge and bullae rarely present. All eggs retained in body (no egg-mass).
Note: Globodera rostochiensis passes through a yellow stage before rupturing root cortex. Globodera pallida remains creamy white until dying and becoming a brown cyst. Mature adult females on potato roots are golden-yellow in color.
There are some morphological differences between G. pallida and G. rostochiensis; e.g., in larval lip region, etc.
Several pathotypes of G. rostochiensis exist: British A, Dutch A,B,C.
For G. pallida: British B and E, Dutch D.
Pathotype classifications are based on ability of nematode to reproduce on resistant cultivars.
Globodera rostochiensis is widely distributed in potato-growing regions; genus probably originated in Peru with Solanum tuberosum and other Solanum spp.
The potato cyst nematodes were originally discovered in Germany in 1913. By that time, the potato cyst nematodes had spread throughout Europe (Wallace, 1964). During the 1960's and 1970's, Canada was found to have several areas of potato cyst nematode infestation (Mai, 1977). Being 450 miles away, the Vancouver Island location is the area closest to California where one of the potato cyst nematodes is known to be established.
In the early 1970's, scientists in Mexico discovered an infestation of G. rostochiensis in the state of Guanajuato (approximately 1,000 miles from the California border), which is one of the major potato-producing regions in Mexico (Alvarez, 1972).
Reported in South Africa in 1971 from an irrigated farm near Pretoria and then from small farms around Johannesburg and Bon Accord. In Aprill 1999, it was reported from the Ceres area in the western Cape Province of South Africa (Knoetze et al., 2006).
In North America, G. rostochiensis was first discovered on Long Island, New York (Nassau County) in 1941 after a potato grower noticed isolated areas of poor plant growth (Mai and Lear, 1953). The nematode may have come in on equipment returned from Europe after WWI - the field was an old military camp which became a potato field. The discovery led to establishment of a Federal Quarantine based on the Golden Nematode Act.
Growers moved to Western New York following urbanization, and subsequent outbreaks appeared; required 8-10 years to reach a detectable level.
Golden Nematode Distribution in New York State, 1999
|Based on information obtained at the International Potato
Center and literature review, the presence of Potato Cyst Nematode (PCN),
Globodera rostochiensis, has been reported in Austria, Australia,
Algeria, Belgium, Bolivia, Canada, Costa Rica, Chile, Czechoslovakia,
Denmark, Estonia, Finland, Germany, Greece, Holland, Hungary, India,
Iceland, Israel, Italy, Japan, Mexico, Morocco, New Zealand, Pakistan,
Panama, Peru, Philippines, Poland, Portugal, Sri Lanka, Spain, ex-Soviet
Union, South Africa, Sweden, United Kingdom, USA, Vancouver Island,
Venezuela and Yugoslavia.
In 16 of these countries there is also information about the races of the nematode.
In 63% of the countries infested with PCN there are no data about races.
The International Potato Center in Lima, Peru maintains a worldwide collection of races and offers a free service for species and race identification.
(Matos and Canto-Saenz, 1990)
A-rated pests in California.
In general, those environments which favor potatoes and tomatoes also favor the potato cyst nematodes. There are many ways in which the potato cyst nematodes could be spread into potato- and tomato-producing regions in California. Important among these is the spread of seed potatoes, plants, root and soil material, either commercially or privately. Tools, implements, automobiles and other equipment imported from overseas or from contaminated areas in North America are all potential sources of infestation. A minute cyst adhering to the underparts of a vehicle in mud would be very difficult to detect. Although difficult to quantify, the probability of the potato cyst nematodes being introduced into California is substantial. The probability of them becoming established, once introduced, may be considerably less, but nonetheless serious.
Feeding site establishment and development typical of genus.
Nurse cell system is a multinucleate syncytium.
Very narrow range: potato, tomato, and some weeds.
Approximately 90 species of the genus Solanum are known to be hosts.
Three commercial crops are hosts of potato cyst nematodes: potatoes, tomatoes and eggplants (Mai and Lear, 1953).
In addition, numerous weeds are known to be hosts of these nematodes (Goodey and Franklin, 1958; 1959). For example, bitter nightshade (S. dulcamara), silverleaf nightshade (S. elaeagnifollum), hairy nightshade (S. sarracholdes), black nightshade (S. nigrum), and jimsonweed (Datura stramonium), which are all present in California, are hosts of the potato cyst nematodes.
Several pathotypes of G. rostochiensis exist: British A, Dutch A,B,C. Pathotype classifications are based on ability of nematode to reproduce on resistant cultivars.
Within a host species, there are distinct cultivars that differ in their susceptibility to various races of nematodes (Kort et al., 1977). This differential susceptibility of cultivated varieties is the basis for one of the primary means of controlling the potato cyst nematodes, that is, host plant resistance.
For an extensive list of host plant species and their susceptibility, copy the name
select Nemabase and paste the name in the Genus and species box
Survival, reproduction, and population dynamics of the potato cyst nematodes can be greatly influenced by temperature, moisture, daylength, and edaphic factors. In general, the potato cyst nematodes will survive in any environment where potatoes can be grown. A period of 38-48 days (depending on soil temperature) is required for a complete life cycle of the potato cyst nematodes (Chitwood and Buhrer, 1945).
Eggs remain dormant within the dead female's body (the cyst) until the proper stimulus to hatch is received (i.e. chemical stimuli released by host plant roots). Potato cyst nematode eggs can remain dormant and viable within the cyst for 30 years (Winslow and Willis, 1972). While in the dormant stage, the nematodes are more resistant to nematicides (Spears, 1968).
When soil temperatures are warm enough (above 100C) (Ferris, 1957), and the proper hatching signals are received (Clark and Hennessy, 1984), the second-stage juveniles hatch from the eggs, escape from the cyst and migrate towards host plant roots. Egg hatch is stimulated by host root diffusate (60-80%) - only about 5% hatch in water. Some eggs do not hatch until subsequent years.
Juveniles penetrate the roots and begin to feed within the root. Host plant cells within the root cortex are stimulated to form specialized cells (syncytia) which transfer nutrients to the nematodes. After feeding commences, the juvenile grows and undergoes 3 more molts to become an adult.
Females grow and become round, breaking through the roots and exposing the posterior portion of their body to the external environment.
Male juveniles remain active, feeding on the host plant until maturity, at which time they stop feeding, become vermiform and seek females (Green, et al., 1970).
Adult males do not feed. Sex is determined by food supply - more juveniles develop into males under adverse conditions and heavy infestations.
Nematodes reproduce sexually; males are attracted to females by a pheromone sex attractant. Nematodes may mate several times.
After mating, each female produces approximately 500 eggs (Stone, 1973b), dies, and the cuticle of the dead female forms the cyst.
|Life cycle diagram by Charles S. Papp, CDFA|
Annual population decline in the absence of a host varies from 18% in cold soils (Scotland) to 50% in warm soils, with an average decline rate about 30% - so population decline follows this pattern: 100-70-50-35-23-etc.
Globodera rostochiensis effect on potato growth (plant on right).
Photograph by Ulrich Zunke, University of Hamburg.
Roots of infected plants exhibit minute, white bodies, which are the immature females that have erupted through the root epidermis. At extremely high nematode densities, tubers may become infected, resulting in the appearance of cysts on their surface.
|In Scotland, 1 ton/acre is lost for every 20 eggs/g soil.
Supply of water and nutrients to upper plant is diminished.
The potato cyst nematodes are semi-endoparasites feeding on the roots of plants.
No distinct host symptoms are associated with low populations, but as populations increase symptoms appear. The plant will show poor growth in small areas that enlarge with the continuous growing of potatoes. Plants in these areas exhibit symptoms of water and/or mineral deficiency stress with yellow leaves and wilting.
In countries that are free of the potato cyst nematodes, quarantines can help prevent their introduction. In countries where their occurrence is localized, quarantines can help prevent further spread. For example, quarantines imposed after the initial discovery of G. rostochiensis on Long Island delayed the spread of the nematode to the mainland (Evans and Stone, 1977). Once the potato cyst nematodes have spread over a large area, quarantines are no longer effective.
In the US, the Golden Nematode Act of 1948 created a quarantine on this nematode. The Animal and Plant Health Inspection Service (APHIS) of the USDA continues to enforce a quarantine on the interstate movement of restricted articles from the New York State. Quarantine items include: soil, compost, peat, manure, live plants, grass sod, plant crowns, roots for propagation, bulbs, corms, rhizomes, root crops, small grain and soybeans (unless in approved containers), hay and straw (unless in approved containers), plant litter, ear corn (except shucked ear corn), used farm product containers, burlap bags, used farm tools (unless free of soil), used cultivating or harvesting equipment (unless free of soil), and seed potatoes. Potatoes for consumption grown in fields certified free of potato cyst nematodes (or receiving applications of required soil fumigants) may be transported if free of soil and moved in approved containers. Those areas within New York which are known to be infested with G. rostochiensis are regulated with respect to the intrastate transport of restricted items.
The discovery of G. rostochiensis in the US, and the consequent Golden Nematode Act, had enormous impact on the development of Nematology. Many scientists received their early training in Nematology through that program. B.G. Chitwood was one of the early directors of the Golden Nematode Lab.
In South Africa, strict quarantine measures were imposed to prevent the
spread of this nematode to other potato-producing areas. In both the South
African Plant Improvement Act (Act No. 53 of 1976) and Agricultural Pest Act
(Act No. 36 of 1983), G. rostochiensis is listed as a prohibited
pest. Distribution by means of seed potatoes is restricted by the
South African Seed Potato Certification Scheme of 15 May 1998, which
provides zero tolerance for infection.
tolerance for infection is permissible (Knoetze et al., 2006).
Eradication of the potato cyst nematodes once they are established in an area seems unlikely. The extremely long survival period of cysts found in the soil limits management options.Management
Of all the crop pests worldwide, the potato cyst nematodes are among the most difficult pests to control (Chitwood, 1951). Once established, they are difficult to eradicate because the potato cyst nematodes have one of the highest survival values for any organism, and can survive for over 30 years as eggs protected by the durable cyst wall (Chitwood, 1951; Winslow and Willis, 1972). Moreover, the build-up of nematode populations is slow, and their presence is not easily detected; once the nematode populations increase to high levels, drastic crop losses occur. One of the best methods of limiting spread once the potato cyst nematodes are introduced into an area is to integrate control measures. In particular, the use of pesticides, resistant varieties, and crop rotation are necessary to prevent further spread in the United States (Evans and Brodie, 1980).
Chemical Control - Chemicals used to control nematodes can be classified according to their volatility as either fumigant nematicides or nonfumigant nematicides. Depending on the concentration used, many fumigant nematicides are general biocides that kill all living organisms in the soil, including nematodes, fungi, bacteria, plants and insects. In contrast, many nonfumigant nematicides are more specific and may not be phytotoxic at field concentrations.
In 1966, plant breeders at Cornell University developed a new potato variety, Peconic. Peconic is similar to Katahdin, a common cultivar in New York, and is resistant to the race of G. rostochiensis that occurs in Newfoundland (Spears, 1968). More recently, resistant cultivars have been developed from S. tuberosum ssp andigena and S. vernei germplasm that have resistance to both G. rostochiensis and G. pallida (Brodie et al, 2000).
In Europe, many cultivars are available which are resistant to the potato cyst nematodes.
For a list of plant species or cultivars (if any) reported to be immune or to have some level of resistance to this nematode species, copy the name
select Nemabase Resistance Search and paste the name in the Genus and species box
Crop Rotation and Cultural Control - When a non-host crop is grown, population levels of the potato cyst nematodes are reduced, since each year a certain proportion of the eggs within the cysts either die or hatch. After a period of five to nine years, the population is reduced to a low level and a successful host crop can be grown. Warmer climates permit greater rates of annual decrease, thus reducing the interval between susceptible crops (Winslow and Willis, 1972).
Soil Solarization - Soil solarization is essentially a mulching process that involves the use of clear plastic film laid over moist soil. After several months during periods of high air temperature, physical and biological changes occur in the soil which can be beneficial to crops (Stapleton and DeVay, 1986). Soil solarization has been used to control G. rostochiensis under New York field conditions (LaMondia and Brodie, 1984). Populations were reduced by 96-99% within the top 10 cm of soil, and encysted juveniles were eradicated to a depth of 5 cm. Since the central valley of California has higher air temperatures and more solar radiation during the summer months than New York, control of the potato cyst nematodes by soil solarization may be more effective under California conditions (Pullman et. al., 1984).
Biological Antagonists - Nematodes, like other organisms, have natural enemies which can reduce their ability to survive and reproduce. Fungi and rickettsia-like micro-organisms have been investigated for their potential to control the potato cyst nematodes (Jatala et al., 1979).