THE VIRUS-FREE SEED POTATO PROGRAM
ACTIVITY PROGRESS REPORT I - July 1, 2003-February, 2004
Major activities conducted in support of the Virus Free Seed Program from July 1, 2003 through February, 2004 were as follows:
Field Sampling, Disease Surveys and Lab Testing
Since July, Dr. McBeath and her six assistants at the Plant Pathology and Biotechnology lab, University of Alaska Fairbanks, have performed the annual field sampling, disease surveys and lab testing activities. The intensively surveyed area included nine (11) potato farms in Delta, Eielson, Nenana, Palmer and Pt. MacKenzie, the Alaska Correction Center farm at Pt. Mackenzie and the UAF Demonstration Garden in Fairbanks. The lists of the pathogens and pests tested this year were expanded considerably. A total of 10 diseases were surveyed and tested. In addition to the six potato viruses (X, Y, A, M, S and leaf roll), bacterial ring rot, and late blight disease, alfalfa mosaic virus and potato mop top virus (PMTV), a quarantined disease, also was included. Furthermore, potato root and soil samples were collected from seed lots on participating farms and processed for root knot and other plant pathogenic nematode extraction and identification.
A total of 268,161 data points were generated from 124 seed lots. Of them four (4) out of eleven (11) farms (seed and tablestock) were found completely free of these diseases.
We have found clear evidence that diseased seed potatoes are the source of contamination. Virus diseases were found on a farm which previously had achieved disease free status but had now become contaminated through a diseased seed lot. The purchased seed potatoes had not been tested.
Until its detection in Maine in June 2002, PMTV was a quarantine disease in the U.S. and Canada. This disease elicited great concern in the potato industry because: 1) it renders the diseased potatoes unfit for processing, 2) it is extremely difficult to detect, and could spread undetected for many years, and 3) it can also be disseminated by a fungus, Spongospora subterranean, commonly found in many regions in the U.S. Once the fungus acquires PMTV, the disease is virtually impossible to eradicate. The most common and effective means of controlling this disease is by exclusion—quarantine. After the discovery of PMTV in Maine, Canada reported to have also found PMTV on potatoes originating from California, Oregon, Idaho, Washington, South Caroline, Florida, Maryland and Delaware. Canadian officials believed that PMTV was widely spread in the US and proposed to quarantine US potatoes. USDA disputed the report from Canada and protested the proposed restriction. In the later part of 2002, PMTV was also found in Canada, which alleviated the tension between the two countries. Understanding the ramification of PMTV to the potato industry and reputations of Alaska seed potatoes, Dr. McBeath took the initiative to include PMTV in the list of diseases to be tested in 2002.
During the 10th US/China Bilateral Talks, held in Chengdu in May 2002, the Chinese insisted that another on-site inspection in Alaska would be required before a final decision on phytosanitary clearance is made. The plant pathogenic nematode, especially root knot nematode (Meloidogyne spp.), golden nematode (Globodera spp.) and stubby root nematode (Trichodorus spp.), are of great concern to the Chinese officials. The plant nematode survey was in conducted 2002 for the purposes of: 1) anticipating additional questions the Chinese officials might have, and 2) giving the inspectors a chance to participate in our survey and detection activities during their visit.
Prior to field activities, Dr. McBeath conducted a workshop to train lab assistants and technicians in potato diseases and pathogenic nematodes, diagnostics, field sampling methods and lab tests protocols. Samples were collected from 89 seed lots and lab tested for nine diseases—the usual list of seven potato viruses (X, Y, A, M, S, leaf roll and mop top), bacterial ring rot, and late blight disease. Immediately after the lab tests were completed (it usually takes two and one half days to process materials), the test results were given to the producers for incorporating in their management plans.
In 2002, the Program produced more than 350,000 data points. We are happy to report that mop top virus was not detected in any of the farms surveyed. Late blight disease was also absent. No plant pathogenic nematodes were detected in any of the samples processed. The number of nematodes found in the samples was extremely low, and all samples them were nonpathogenic, free-living nematodes. Mr. Ge Jianjun, head of the Chinese inspection team and a nematologist, examined the samples and was very impressed with the results. The results verified previous nematode survey data in the phytosanitary clearance application packet submitted by Dr. McBeath to the Chinese via the USDA.
All of the seed potato and most of the tablestock potato farms were found free of bacterial ring rot infestation. It was found only on a few seed lots of one tablestock farm in the Palmer area. The level of infestation this year was very low.
Virus diseases continued to pose a problem to potato farmers. This year, three (3) farms out of a total of eleven (11) farms (seed and tablestock), were found completely free of any diseases. A low level of virus infestation was found in a small number of seed lots of four (4) farms that were able to achieve disease free status previously. The re-surfacing of virus diseases on farms that were found disease free in the previous year illustrates again the importance of yearly sampling and lab testing in the continued improvement of the health of potatoes in Alaska.
The viruses found in 2002 were PVX and PVS. Both viruses can be introduced to a farm through diseased seed potatoes or via contaminated seed cutters, hands, cultivation equipment, etc. These diseases are very difficult to observe visually because they produce mild or no symptoms under Alaska environmental conditions. A lab test is the most reliable means of detection. Once the hot spot are located, these viruses can be eradicated from the farm by observing strict sanitation practices and flushing out diseased potatoes through the limited generation program instituted by the State by planting virus free test- tube plantlets.
Chinese officials gave Dr. McBeath a copy of the preliminary PRA report during one of the meetings in 2001. However, repeated requests from Dr. McBeath and USDA for the formal PRA were met with inaction. Chinese officials withheld the PRA final report on Alaska potatoes in retaliation to inaction of the U.S. on clearing Chinese Pengjing (bonsai) for export to America.
The 10th Bilateral Agricultural Talks between China (AQSIQ) and the U.S. (USDA-APHIS) was held in Chengdu, China in May 2002. At the meeting, Mr. Ge Jianjun, on behalf of the Chinese delegation, presented Dr. McBeath with a copy of the Pest Risk Assessment of Alaska potatoes. It was the only ‘deliverable’ obtained by the US delegation in an otherwise very contentious meeting. During the Bilateral Talks, the Chinese delegation insisted that another on-site inspection was needed. This request was highly irregular and clearly a delaying tactic, but Alaska has very little choice but to comply. The USDA was unhappy about this request However it demonstrated strong support for Alaska by defraying all travel expenses for the two Chinese inspectors.
On August 9, after many delays, Mr. Ge Jianjun and Ms. Li Guaifen arrived in Fairbanks. Mr. Martin Patterson (USDA-FAS) and Mr. Robert Bailey (USDA-IT) arrived on August 8. The purpose of their visit was to witness the inspection.
The Chinese government had stipulated that the inspection trip should include: 1) field inspection of potato crops, 2) evaluation of the disease sampling and lab test process, 3) evaluation of potato farm operations and facilities, and 4) evaluation of Alaska environmental conditions.
On August 10 (Saturday), Mr. Ge, Ms. Li, Mr. Patterson, and Mr. Bailey went with Dr. McBeath and her crew to two seed farms in Delta. This was the last field disease survey and sample collection activity of the season. On the farms, Chinese inspectors and USDA visitors observed Dr. McBeath and her crew performing their routine activities. Mr. Ge and Ms. Li inspected and sampled potato plants and roots for presence of disease symptoms, nematode damages and any anomalies.
On August 11 (Sunday), lab tests began on samples collected by Dr. McBeath’s group and the Chinese inspectors. To accommodate the visitors’ tight schedule, the protocol of the lab test was modified and the process was compressed from two and one half days to one and one half. Thousands of leaves and stems were processed and tested. Test results indicated that samples collected by Ms. Li and Mr. Ge were tested free of any diseases. As is frequently the case of compressed protocol, high background were found in some of the samples tested show a higher than normal background reading and ambiguous results. It is the usual practice of the program to retest samples in question. To honor our visitors from China and also to show our openness, we asked Ms. Li to mark any samples she wished to retest. Retest was completed on August 14 and results showed that the all samples were free of diseases. To verify our tests, one half of the samples in question were also sent to AgDia Diagnostic in Indiana. Test results from AgDia confirmed our findings. A copy of the report stating results of the lab test and retest was given to Mr. Li and Mr. Ge on August 14.
On August 10, on the two farms in Delta, potato plants and roots were examined for signs and symptoms of nematode infestation. Potato roots and soils were also collected and processed for nematode extraction. On August 11, the nematodes extracted were examined under a stereomicroscope. Results from the nematode survey indicated that 1) potato plants and roots are healthy and free from any damages, 2) the nematodes population in soils is extremely low, 3) none were plant pathogenic nematodes, and 4) all of the nematodes found were free-living nematode. Mr. Ge, an expert in nematology, was most impressed by the result.
Major Trips Conducted since July 1,2002
Trips to Delta, Eielson, Nenana, Pt. Mackenzie & Palmer (to conduct the disease survey and
sampling on potato and carrot farms), July through August 2002, by Drs. McBeath, Peter
Gay and six assistants.
Trip to Milwaukee, WI, July 2002, by Dr. McBeath to present research results at the American
Phytopathological Society annual meeting.
Trips to Delta, Fairbanks, Palmer, Pt. Mackinzie, Anchorage by Dr. McBeath accompanying two
Chinese inspectors (Mr. Ge Jianjun and Ms. Li Guafen), and USDA representatives (Mr.
Martin Patterson and Mr. Robert Bailey. The USDA defrayed the travel expenses of the
Chinese inspectors and USDA representatives.
Trips to Taiwan and China, September and October 2002, by Dr. McBeath to discuss with
government officials and scientists on potato diseases and phytosanitary clearance related
issues and give an invited talk at the National Chungshing University..
Trip to Portland, ME, in early December 2002, by Drs. McBeath and Peter Gay, to attend the
National Seed Potato Seminar.
Trip to Riverside, CA, mid December 2002, by Drs. McBeath and Peter Gay to present research
results at the USDA Western Regional Research Project W-147.