Detection of a New Globodera Species During Surveys of Oregon Seed Potato Fields for Potato Cyst Nematodes
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Detection of a new Globodera species during surveys of Oregon seed potato fields for potato cyst nematodes The 2nd NPDN National Meeting Cindy L. Fraley, Shawn X. Meng, and Nancy K. Osterbauer Oregon Department of Agriculture, Salem, OR 97301. Miami, Florida, Dec 6-10, 2009 ABSTRACT The potato cyst nematodes, Globodera pallida and G. rostochiensis, are recognized worldwide as serious pests on Solanum tuberosum. In the United States, both are considered quarantine pests. Recent detections of G. pallida in Idaho and G. rostochiensis in Alberta and Quebec, Canada, led to a national survey for these pests in states producing seed potatoes. Since 2006, the USDA APHIS PPQ has required all states that produce seed potatoes to survey fields for potato cyst nematodes. Soil samples were collected from seed potato fields using the most current national survey protocol at the time of collection. The soil samples were dried and then processed using a USDA Soil Cyst Washer; the resulting flotsam was examined microscopically for cysts. A total of 3,830 soil samples were collected from seed potato fields planted in 2006 and in 2007. No potato cyst nematodes were detected. However, suspicious cysts were found in soil samples collected from a field in Crook County that had been planted in 2007 with true potato seeds. Initial examination showed the cysts most closely resembled a Globodera. Per USDA APHIS PPQ protocol, the suspicious cysts were forwarded to the National Identifier for official confirmation. Morphologically, the cysts most closely resembled G. pallida. However, molecular analyses showed RESULTS AND DISCUSSION the cysts were genetically distinct from all three known Globodera species, indicating a new species had been detected. From 2006 to 2009, a total of 138 fields (7,594 acres) in ten counties for potato seed and commercial production were surveyed for PCN. Neither G. pallida nor G. rostochiensis was found in any of those potato fields (Table 1 and Fig. 3). Globodera-like cysts (brown to dark-brown, globose, spheroidal, with a short neck and no terminal cone) were discovered in a true seed potato field in Crook County (Table 1 and Figs. 3 and 4). More Globodera-like cysts were found from re-sampled soil samples from the field. Morphologically, the cysts most closely resembled G. pallida. Based on the USDA-APHIS-PPQ Specimen Forwarding Protocol, these Globodera-like cysts were forwarded to INTRODUCTION the National Identifier. Molecular analyses showed these cysts were genetically distinct from all three known Globodera species, and were confirmed to be a new Globodera species. Further identification of the new species is under way. ODA is assisting Oregon State University and others in determining Potato cyst nematodes (PCN), Globodera pallida (the white or pale the host range and developing a species description for this new Globodera. All of the survey results were entered into ISIS and NAPIS databases as PCN) and G. rostochiensis (the yellow or golden PCN), are the most required by the USDA. devastating and widely distributed nematode pests of potatoes. Known hosts include potatoes (Solanum spp.), tomatoes (Lycopersicum Canada is one of the most important international markets for Oregon potatoes. In 2006, G. pallida was first detected in several fields in Idaho and esculentum), eggplant (S. melogena), and some solanaceous weeds (e.g. in 2007, G. rostochiensis was discovered in seed fields in Alberta, Canada. These two findings prompted a quick response from the USDA-APHIS and nightshade). PCN originated in the Andes Mountains of South America (1). their Canadian counterparts. APHIS worked with the Canadian Food Inspection Agency to adopt a bilateral agreement for surveys for the two nematode In the US, Globodera rostochiensis was first found in New York in 1941 and pests (Guidelines on Surveillance and Phytosanitary Actions for the Potato Cyst Nematodes: Globodera rostochiensis and Globodera pallida, Version 13, G. pallida was found in Idaho in 2006 (www.aphis.usda.gov). Crop losses May 4, 2008, USDA and CFIA, 21 pp.). USDA-APHIS also adopted the Rationale and Methodology for Full Field Survey of Alberta Trace Forward Seed caused by the G. rostochiensis infestation can be as high as 70% under Potato Fields. Seed potato growers that received Alberta seed from 2005 to 2007 and commercial growers that received seed in 2007 were surveyed as poor PCN management conditions (2). Occurrence and spread of PCN required in the trace forward protocol. One hundred percent of each field was surveyed with soil samples collected at the recommended rate. All other caused serious problems for potato exports due to strict international seed and commercial potato fields were surveyed for PCN according to the bilateral survey guidelines. No PCN was found from any of our soil samples, restrictions against PCN. including the trace forward samples from the Alberta find. Oregon is one of the nation’s leading producers of potatoes The PCN survey will be continued in 2010, which is critical for maintaining Oregon potato exports and opening new markets. growing more than $157 million on 36,500 acres in 2007. In terms of revenue, potato is the 7th most important agricultural commodity in Oregon (3). A federal domestic quarantine order for pale potato cyst nematode (G. pallida) was enacted in 2006. Seed potato-growing areas must be surveyed and found free of PCN for potato export. We have conducted PCN surveys in Oregon since 2006. The objective of this survey is to determine if Oregon’s commercial and seed potato production areas remain free of PCN and thus can be exported. This survey provides critical information on the status of PCN in Oregon, helps maintain export markets, and helps potato growers meet new USDA standards for management of PCN. Materials and Methods Soil samples were hand-collected from Oregon seed potato and commercial potato production fields according to the most current national PCN survey plan (USDA Pale Potato Cyst Nematode National Survey and Diagnostics Cyst Sample Forwarding Protocols) at the time of collection. Briefly, one 5-lb composite soil sample (comprised of 100 sub- samples) was collected per acre of field surveyed, and processed in its entirety using the USDA Soil Cyst Washer (Fig. 1). The USDA procedures were followed for nematode cyst extraction, sorting, and disposal. The extracted cysts were examined morphologically under the microscope (Fig. 2), and suspect samples were to forwarded to the USDA Nematology Laboratory for confirmation. REFERENCES ACKNOWLEDGEMENT 1. Compendium of potato diseases, 2nd edition, 2001, edited by W. R. Stevenson et al. APS Press, the American Phytopathological This survey was partially funded by USDA APHIS PPQ. We thank ODA CID staff for Society, St. Paul, Minnesota, USA. collecting soil samples. We also thank Oregon’s potato industry and growers for their kind 2. Greco, N. 1988. Potato cyst nematodes: Globodera rostochiensis and G. pallida. Nematology Circular No. 149. Florida Department participation in this survey. We appreciate technical support provided by Oregon State of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, Florida, USA. University and USDA APHIS PPQ. 3. Oregon Agripedia, 2008 edition, Oregon Department of Agriculture, Salem, Oregon, USA..