The potato cyst nematodes (PCNs), Globodera rostochiensis (Golden nematode) and G. pallida (Pale cyst nematode), are two very closely related species known to be major pests of potatoes across the world.
In light of this, PCNs are the subject of strict quarantine regulations in many countries, including Canada and United States. These nematode species are capable of causing severe losses in potato fields up to levels in excess of 80 per cent and have remarkable ability to survive unsuitable conditions. Cysts containing viable eggs can survive in the soil for up to 20 years until a host such as potatoes is planted. The life cycle of PCNs starts when second-stage juvenile hatches after stimulation by potato root diffusates. These juveniles have the capacity to detect the potato roots and to penetrate inside them. Afterward, the development of cysts on roots is observed. Cysts mature outside the potato roots and then fall into the soil. Consequently, PCN cysts can be carried in soil adhering to seed tubers, farm machinery and equipments, boots etc. and can also be transported by wind and flood water. The host range of PCNs is limited to potatoes, tomatoes, eggplants and some solanaceous weeds.
Distribution of PCNs in North America
In Canada, G. rostochiensis was first identi-fied in 1962 near Botwood in Newfoundland. This finding was attributed to the importation of potatoes and other vege-tables from the United Kingdom because prior to becoming a province in 1949, Newfoundland was free of any import regulations. A few years later in 1968, G. pallida was also identified in this province. In 1965, G. rostochiensis was reported in British Columbia on the Saanich Peninsula, near Victoria. Infestation was associated to the importation of bulbs from Europe followed by several years of monoculture of potatoes. A fumigation program was initiated to control the infestation and all host crop production has been prohibited in the infested zone since 1982. Recently, the recovery of G. rostochiensis in the provinces of Quebec (2006) and Alberta (2007) prompted the Canadian potato industry to set up a national research program aimed at the integrated management of PCNs.
In the United States, both species of PCN were identified. In New York state, G. rostochiensis was first isolated on Long Island (1941) and further in western New York state (1967). In 1994, the pathotype Ro2 of G. rostochiensis was first reported in North America (New York state). Moreover, G. rostochiensis was found in Delaware in 1968 but no cyst was recovered since the first report in despite of several surveys. In 2006, G. pallida was discovered on eight potato fields in Idaho.
Research in Canada
The discovery of PCNs in Quebec and subsequently in Alberta had a significant impact on the Canadian potato production industry and international trade, and led to an intensive survey to define the infested area. This situation also revealed the urgent need for research on PCNs in Canada to help potato growers to face this challenge.
One critical objective of the national research program on integrated management of PCNs is to study the biology and population dynamic of G. rostochiensis under our climatic conditions. Particularly, researchers are currently working to determine the seasonal development and survival rate of G.rostochiensis and evaluate the potential of emergence of new pathotypes of G. rostochiensis and the species G. pallida. Researchers are also trying to develop alternative control strategies for PCNs in Canada. The screening of potato varieties and clones for G.rostochiensis and G.pallida resistance adapted to Canadian market and climatic conditions is certainly the most promising tool. Currently, the five major potato varieties, grown in Canada for more than 50 per cent of the cultivated area (~400, 000 hectares), have no resistance against G. rostochiensis. Consequently, potato breeders have now included PCN resistance in their program and the screening of potato clones and varieties against both species of PCN is currently underway. Research efforts have been oriented towards three fields of activities:
In 2008, 370 clones and varieties were tested and several white flesh clones and/or varieties have shown high resistance to G. rostochiensis and also good agronomic traits for the Canadian market. Furthermore, researchers aim to evaluate the potential of crop rotation and non-host plant strategies to reduce G. rostochiensis populations; to determine the potential of trap cropping and tuber-forming sticky nightshade (Solanum sisymbriifolium) for suppression of G. rostochiensis and to assess the potential of various soil amendments and treatments to reduce G. rostochiensis populations.
G. rostochiensis infested fields in regulated area in Quebec are available for the research team to conduct experiments related to the development of an integrated management program against PCNs. The area of more than 10 hectares represents the most important research facilities in North America. In 2008, more than 400 microplots were installed to conduct research activities on G. rostochiensis and soil PCN extraction facilities were set up in the infested research area. In 2009, clones and varieties from the potato breeding programs in Quebec and Fredericton (New Brunswick) will be screened against G. pallida in Agriculture and Agri-Food Canada, St. John’s, N.L.
Quebec PCN Research committee members are: Georges Laplante and Nancy Shallow (CFIA), Guy Bélair and Dr. Louis Simard (AAFC), Dr. Pierre Turcotte (MAPAQ), and André Gagnon (ProgesT 2001 Inc.).
Research on PCNs in Canada is currently supported by: Conseil pour le développement de l’agriculture du Québec, Canadian Food Inspection Agency, Agriculture and Agri-Food Canada, ProgesT 2001 Inc., Centre de recherche Les Buissons Inc., Fédération des producteurs de pommes de terre du Québec, New Brunswick Agri-cultural Council Inc., Agriculture and Food Council of Alberta, Adaptation Development Agricultural Production Technology Council (PE), Manitoba Rural Adaptation Council, Agricultural Adaptation Council Ontario, Groupe Gosselin FG Inc., Les Semences élites du Québec, Distribution Proplant Inc., Propur Inc, Patate Lac St-Jean, Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec, Institut de recherche et de développement en agroenvironnement, Agriculture Council of Saskatchewan Inc., Patates Dolbec, Investment Agriculture Foundation of Bristish Columbia, Agri-Futures Nova Scotia, Fondation Banville et Michaud, Agri-Adapt Council Inc. de Terre-Neuve et du Labrador (N.L.).
Guy Bélair, M.Sc., is a researcher and nematologist and Dr. Louis Simard, PhD, is also a nematologist. Both are with the Horticulture Research and Development Centre, Agriculture and Agri-Food Canada, located in St-Jean-sur-Richelieu, Que.
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