Minutes
2004 WCC 20 Annual Meeting
Davis, CA
May 17-19, 2004
I. Opening Remarks and Business Meeting:
The meeting was held in the conference room at the Hallmark Inn in Davis, CA. Adib Rowhani, chair for
the meeting, gave a welcome and opening remarks. Sincere appreciation is extended to Adib, Deborah,
Jerry and their staff for hosting a fantastic meeting this year.
Ralph Cavalieri, administrative advisor for the committee, also extended his welcome. He reminded us
that the project plan for the WCC 20 expires in September 2005 and that a new project rewrite will need
to be in place by January 2006. On the budget side, Ralph reported that budget cuts were absorbed at the
federal level by some popular agricultural research programs. Efforts are underway to restore some of
these funds, although delays in completing the federal budget are becoming increasingly common each
year. The FY ‘05 budget proposed by the President calls for an increase in NRI funding, as well as
increases for issues related to Homeland Security. A National Institute of Agricultural Security has been
established by the land grant university system. This organization is funded by voluntary contributions
from the universities and has a full time staff member in Washington, DC. The purpose of the
organization is to promote agricultural biosecurity.
Zvesdana Pesic-Vanesbroeck volunteered to host the meeting next year at NC State in Raleigh, NC
sometime between mid-May and early June. This offer was accepted by acclimation.
II. State Reports: This does not necessarily correspond with the order in which oral presentations were
made.
1. Canada
Ray Johnson explained the grapevine diagnostics program at CFIA’s Centre for Plant Health. Their
program maintains a virus tested repository, and performs therapy, for grape varieties and rootstocks.
This program also tests strawberry and blueberry material. Ray discussed some of the efforts to improve
diagnostic tests that are underway including studies to compare bioassays to PCR for the detection of
GVA, GVB, and GLRV 2 (red globe strain). He also reported that their program provides import audit
testing of nursery stock from the US, France, and Germany. The North American Plant Protection
Organization (NAPPO) guidelines for virus and virus-like diseases of grapevines was signed in
November 2002 and the pest list was updated in 2003. Development of standards for nematode and
arthropod pests is underway.
Dan Thompson reported that 48 new accessions (stone, pome, and small fruits) were submitted for
indexing in his program. The national PPV survey processed about 73,000 samples in 2003 and new
positives were identified in Ontario and Nova Scotia. Both were PPV-D strain. The Canadian
government approved funding for a seven year PPV eradication program. Dan reported results of work to
examine the ELISA detection and distribution of PPV in dormant scions. Buds taken from field grown
trees, along with bark tissue from the basal end of the sticks, appeared to have highest levels of virus. He
is also attempting to improve on their motorized pencil sharpener for grinding woody samples by using a
Dremmel tool modified to shave off only the buds and outer bark and exclude the woody core tissue.
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However, ELISA values for PDV, PNRSV, and PPV were similar irrespective of the type of grinder used.
Dan also reported on virus-like symptoms that were observed on the Amos Black and Baldwin indicators
that were inoculated with a black currant accession from Russia. The agent is currently unknown as
ELISA and PCR results for viruses reported in currant were negative.
Roberto Michelutti reported that the survey of stone fruits for PPV and several other viruses/viroids has
been completed at the clonal genebank at Harrow. No PPV infections were found, but the total incidence
of infection in the collection was 38.4%. PNRSV and PDV were the most common infections, with a
lower incidence of PLMVd and HSVd. Distributions are still being made from infected items, but its
infection status is clearly communicated to the recipient.
2. California
Jerry Uyemoto reported on a grapevine location where Merlot on 110R was showing extensive
reddening of leaves. The affected vines also had undesirably later ripening fruit. Preliminary tests
revealed the presence of at least grapevine rupestris vein feathering Marifivirus. This would be the first
report of this virus in the US. He also reported on the results of various Prunus tests in 2003 and showed
slides of the symptoms. These included a Bing cherry tree that tested positive for PDV and CVA, as well
as cherries that were infected with little cherry virus-1 and CNRMV. Jerry also noted he believes that
ACLSV appears to be occurring more frequently (or at least we are looking for it more) in Prunus.
Cristina Rosa (graduate student working with Adib) discussed progress on her work with the rugose
wood complex of grapevines. One of her objectives is to clarify the etiology of this disease. Grapevines
(3 different hosts) have been inoculated with combinations of GVA, GVB, GVD, and GRSPaV. These
vines will be planted in the field and monitored for symptom expression. GVD is the least characterized
of these viruses, so a project has also been initiated to sequence this virus. Work is also underway to
sequence a marifivirus isolated from Cabernet Sauvignon. Finally, work is being performed to optimize
extraction procedures and primer design for the PCR detection of CTV is California citrus.
Mirtes Lima (graduate student working with Adib) described her work on GRSPaV isolates from Syrah
and Pinot Noir. This virus appears to be correlated with poor overall performance of some vines on
certain rootstocks. The Syrah isolate has been sequenced and the isolate from Pinot, as well as an isolate
obtained from France, has been partially sequenced. The Syrah isolate has 8,725 nucelotides organized
into six open reading frames. The overall nucleotide identity to the sequence deposited in GenBank is
77%. Specific PCR primers in the replicase region have been designed to distinguish the Syrah and Pinot
isolates and these are being used to examine field spread of the viruses.
Fatima Osman (Post Graduate Researcher working with Adib) is developing real time RT-PCR detection
systems for GLRaV 1,2,3. Virus-specific TaqMan probes and primers are being designed based on
conserved sequence data for a larger number of GLRaVs. Sequence in the HSP 70 regions, for example,
has been selected as the target region for GLRaV1. Work is also being performed to determine the most
effective and reliable methods for sample extract preparation. Procedures that are being tested include
crude extracts, nylon spotted membranes, kit based reagents, and the ABI 6700 automated workstation.
Adib Rowhani discussed his work with GLRaV 9. A cDNA library was constructed from dsRNA
extracted from vines that had been identified as infected with this new virus. The isolate did not react with
ELISA or RT-PCR for previously described GLRaVs. Overlapping clones were sequenced and gaps
were completed using specific RT-PCR primers. The sequence data to date demonstrates that this is a
distinct virus. GLRaV 9 shares the greatest nucleotide identity to GLRaV 5 (87% identity in the CP).
Furthermore, another potentially new leafroll virus is being sequenced. This isolate was from the cv.
Carnelian. The virus caused symptoms on the Cabernet Franc indicator, but has not reacted in ELISA
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and/or RT-PCR to the other leafroll viruses. Data currently available reveals HSP 70 and CP identities in
the 70s% versus other GLRaVs.
Deborah Golino gave a presentation about the mission and organization of the Foundation Plant Services
program. The facility opened in 1994 with funds provided by CSREES and land by UC-Davis. The
program has evolved into a multifaceted program providing services to numerous agricultural crops
including grapes, stone fruits, strawberries, sweet potatoes, pistachios, chestnuts, and walnuts. Services
vary with the crop and include foreign importation, diagnostic testing, therapy, certification, and clean
stock programs. Depending on the crop the customers/clients for the program ranges from nursery
professionals to sales directly to growers. The program operates on a fee for service basis. The extent of
the testing varies with the crop and can include the use of woody and herbaceous indicator plants,
serological assays and, increasingly, molecular tests.
Bruce Kirkpatrick reported briefly that his work continues with the host movement study of almond leaf
scorch (xyllela) among popular commercial cultivars. He also has an interesting project going to examine
whether endophytic bacteria may be involved in helping certain grapevines escape infection with Pierce’s
Disease.
3. Hawaii
John Hu has on-going research projects with mealybug wilt disease of pineapple. This disease is
associated with at least 2 closterovirues (PMWaV 1, 2), but only when mealybugs and ants are also
present on trees. The role of the ants appears to be as caretakers of the mealybugs by discouraging
predators and mealybug vectors. The disease appears to occur only when PMWaV 2, mealybugs, and
ants are present. Diagnostic tests including tissue blots and, more recently, RT-PCR have been
developed. The complete nucleotide sequence of PMWaV 1 (10 ORFs with typical monopartite
closterovirus arrangement) has been determined, and about 10K nucleotides have been sequenced from
PMWaV 2. The nucleotide identity between the two viruses appears to be about 50% based on data to
date. Furthermore, screening accessions from the ARS pineapple repository collection in Hilo led to the
discovery of two more potentially wilt associated viruses, PMWaV 3,4. Work has been performed to
determine the species and life stages of mealybugs that transmit the wilt viruses. Work is underway to
develop transgenic control strategies for this disease. Some screening with CP constructs is underway.
4. Maryland
Gary Kinard provided an update from the Plant Germplasm Quarantine Office (PGQO) on activities
related to pome, stone and small fruits at the USDA quarantine center. There is a scientist vacancy in the
position in charge of the tissue culture, therapy and rice programs. PGQO has conveyed to the USDA
administration the importance of this position and is awaiting approval to fill this vacancy. After lengthy
delays, occupancy of the office and screenhouse portions of the building addition occurred in early 2004.
However, the new laboratory and greenhouse space has not yet been made available for use. Statistical
data were presented about the number of receipts, releases, distributions, therapy activities and pathogen
interceptions for the fruit programs over the last year. Notable was the interception of PPV-D in several
plum accessions from Russia. Several research projects aimed at improving the quarantine programs are
underway. These include: RT-PCR detection of CGRMV and CNRMV in stone fruits, RT-PCR
protocols to detect GVBaV in currants, and constructing a dig-labeled probed to detect AFCVd in pome
fruits.
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5. North Carolina
Zvezdana Pesic-Vaneesbroeck described her certification and micropagation program at NC State that
handles blueberries, blackberries, strawberries, and sweet potatoes. In the small fruits, grower concerns
about decline in commercial plantings 2-3 years after establishment led to the examination of virus
problems in the region. Virus surveys were preformed in 2001-2002 at 5 sites in NC, 4 in SC, and 1 in
VA. The most common viruses present were TRSV, ToRSV, and INSV. There were plants that
displayed virus-like symptoms that tested negative for these viruses, as well as RBDV and TSWV. Bob
Martin investigated these and described a new criniviruses they have named blackberry yellow vein virus
(BYVV). In July 2003, six plantings in NC and SC were surveyed specifically for BYVV; the results
suggest the virus is widespread.
6. South Carolina
Simon Scott reviewed the status of the certification program for the southeastern peach industry. The
program, which began in 1985, lost favor with the industry by the late 1990’s. After the PPV outbreak,
support re-emerged and common stock testing blocks of varieties and rootstocks have been reestablished.
Nurserymen are also supporting the program by assessing a nursery stock fee on sales. The industry is
assuming responsibility for agreeing on trueness to type. Simon is continuing to unravel the relationship
between the use of Ta Tao interstems to delay bloom in peaches and the presence of viruses and sub-viral
agents. Ta Tao is infected with at least PLMVd, ACLSV, and a foveavirus.
7. Washington
Bill Howell provided an update on various projects and the NRSP-5 program. A long-term study to
investigate possible cross protection of sweet cherries to rugose mosaic by inoculation with a mild strain
of PNRSV continues. Some protection appears to be afforded by this approach. A study also continues
to examine the effect of PLMVd infection on 5 peach and nectarine varieties. To date, the only obvious
effect may be a slight difference in blooming time between infected uninoculated trees. Bill also noted
that they are encouraging growers to use a systemic herbicide to indirectly track potential movement of
pathogens that could be transmitted by root grafts. When the stump of a rouged tree is treated, systemic
spread and herbicide injury symptoms to adjacent trees the following year could indicate spread of the
pathogen. The NRSP-5 program had another active year receiving 45 new pome and stone fruit
accessions from foreign sources and 66 proprietary and non-proprietary clones from domestic sources for
testing. Most of the infected accessions were stone fruits from China and were infected with PNRSV or
PDV.
Ken Eastwell reported on the eradication program for CLRV conducted in partnership with the
Washington Tree Fruit Research Commission and Cooperative Extension Service. Early results suggest
that the program is working. Lauri Guerra also commented on the effectiveness of this program. The
genome of cherry rasp leaf virus has been sequenced and coat proteins have been expressed in a bacterial
system in order to inject sheep for antibody production. Work is also continuing to elucidate the cause of
the problem of graft incompatibility symptoms that have been observed with some cherry varieties on
Gisela 6 rootstock after several years in the orchard. Early results suggest that ACLSV and/or a
foveavirus may be associated with the problem. Molecular characterization of 7 foveavirus isolates from
cherry is continuing with the collection of sequence data and the development of RT-PCR detection
systems.
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8. New Zealand
Mary Horner from HortResearch in New Zealand was visiting WSU-Prosser and participated in the
meeting. She stated that after a decade of inactivity the New Zealand government has decided to resurrect
importation and quarantine of foreign germplasm into the country. The new program will operate under a
fee for service arrangement. A new quarantine facility has recently been completed and the diagnostic lab
will operate at ISO 9000 standards. The risk assessment group is currently performing comprehensive
studies to determine the testing requirements.
III. Other activities
After the oral reports were completed in the afternoon of May 18, the group was given a guided tour of
research and germplasm plots at UC-Davis and of the Foundation Plant Services facility. Afterwards, the
FPS staff generously hosted a reception for their guests. On May 19 the group toured several orchard and
vineyard sites in the San Joaquin valley areas south of Davis, focusing on virus and virus-like production
problems in cherries, almonds, walnuts, and grapes. The tour also included a stop at a large cherry
packinghouse. The tour concluded with wine tasting at the Lodi wine and visitors center.
IMPACTS: Much of the research of participant at WCC20 is facilitated by their interaction in these
meetings. In general, the research work of the participant is involved in identifying and characterizing
new viruses, developing molecular detection methods for different viruses in horticultural crops, sharing
problems that they have encountered in their research and/or disease diagnosis and seek assistance from
other experts in the group to resolve the problem, and developing resistant plants to some of the more
important viruses. This interaction at WCC20 meetings has an immediate and direct application on
improvement of clean stock program by developing and improving new disease detection methodologies
or to justify for establishment of new clean stock programs. The economic impacts of clean stock
program on propagators and fruit growers may reach hundreds of millions of dollars (the most recent
number shows estimated over $200 million annually1). In addition, other aspects of the efforts of this
group are to improve disease detection and elimination procedure for exotic viruses and virus-like agents
entering the country through importation of plant materials. Advanced detection of these agents in plant
materials before propagation and planting in the field will save millions of dollars for federal agencies and
growers (for example, the spread of plum pox virus in Pennsylvania and the related cost for its
eradication). The impact of transgenic plants resistant to viruses could be seen in transgenic papaya
resistant to papaya ringspot virus. This new resistant plant practically saved the papaya industry in
Hawaii and some other parts of the papaya growing areas of the world.
1. Cembali, T., R.J. Folwell, P. Wandschneider, K.C. Eastwell, and W.E. Howell. 2003. Economic
implications of a virus prevention program in deciduous tree fruit in the US. Crop Protection 22: 11491156.
IV. Attendees and affiliation
Emilie Carrouche
Ralph Cavalieri
Mike Cunningham
Ken Eastwell
Deborah Golino
Lauri Guerra
Mary Horner
FPS/UC-Davis, Davis, CA
Washington State University, Pullman, WA
FPS/UC-Davis, Davis, CA
Washington State University, Prosser, WA
FPS/UC-Davis, Davis, CA
Washington Department of Agriculture, Prosser, WA
HortResearch, New Zealand
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Bill Howell
John Hu
Ray Johnson
Gary Kinard
Bruce Kirkpatrick
Mirtes Lima
Roberto Michelutti
Fatima Osman
Christina Rosa
Adib Rowhani
Sue Sim
Simon Scott
Scott Sioddard
Dan Thompson
Mike Tiffany
Jerry Uyemoto
Zvezdana Pesic-Vanesbroeck
Washington State University, Prosser, WA
University of Hawaii, Oahu, HI
CFIA, Sidney, British Columbia
USD-ARS, Beltsville, MD
UC-Davis, Davis, CA
UC-Davis, Davis, CA
Ag-Canada, Harrow, Ontario
UC-Davis, Davis, CA
UC-Davis, Davis, CA
FPS/UC-Davis, Davis, CA
FPS/UC-Davis, Davis, CA
Clemson University, Clemson, SC
UC Cooperative Extension
CFIA, Sidney, British Columbia
Agdia, Inc., Elkhart, IN
USDA-ARS, Davis, CA
NC State University, Raleigh, NC
Submitted by Gary Kinard
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