Brief Summary of Minutes of Annual Meeting

Minutes Summary: WERA-89 Annual Meeting

DoubleTree Suites by Hilton Tucson Airport

Tucson, AZ on March 2-3, 2016

Chair: Carrie Wohleb; Vice Chair: Andrew Houser; Secretary: Ken Frost

The meeting started at 8:00 am March 2, 2016. The minutes of the WERA-89 Annual Meeting of March 4-5, 2015 were corrected and then unanimously approved.

Administrative Advisor Report:  Alex Karasev reported for the new WERA-89 Administrative Advisor, Mark McGuire, who was unable to attend.  The WERA-89 group was praised for being very active and submitting documents on time.

State Certification Reports: 

CA - Pablo Guzman noted some issues that came up while inspecting potato seed crops in California in 2015. He said two seed lots with mop top virus were found in an ‘Atlantic’ seed crop.  He noted that the symptoms were very difficult to see pre-bloom.  The symptoms resembled those of frost injury or potato calico (alfalfa mosaic virus), but there was no alfalfa grown in the area.  Guzman shared several images with the group.  The foliar lesions are usually less splotchy than calico symptoms, are often in a “V” shape, and tend to bleach out.  He noted that a nearby commercial potato field with powdery scab and mop top virus is probably the source of the problem in the seed field.  The commercial potato field has been under continuous potato production.  Guzman said the grower uses separate equipment to work the potato seed fields.  California does not reject seed lots for mop top virus per se, but there is the 0.5% tolerance under the Canada/US-Management Plan for Potato Viruses that Cause Tuber Necrosis.  It was noted that many varieties do not show significant necrotic tuber symptoms, including ‘Atlantic’.  There was a discussion about the prevalence of mop top in seed potato crops.  Alan Westra said spraing symptoms are found occasionally in the Idaho seed program, and when tested, usually turn out to be mop top or alfalfa mosaic virus, rather than tobacco rattle virus.  Idaho is getting rid of their zero tolerance for tobacco rattle virus.  He noted finding mop top in seed fields belonging to 4-5 growers in the past few years.  Rob Davidson said that mop top has been found on two farms in three seed lots over the past three years in Colorado.  He noted that tobacco rattle virus used to be more common.    

Guzman talked about a potato seed field with several varieties that had alfalfa mosaic virus.  He saw more symptoms in ‘White Rose’ than in ‘Granola’, ‘Red Lasoda’ or ‘Atlantic’.  There was a discussion about why this might be. 

Guzman was asked to do a late inspection of a seed crop in Arizona destined for Central America.  He noted that it was difficult to inspect the crop because it was senescing.  Later, he heard that zebra chip was found in the shipment and the potatoes were destroyed.  He learned about this by chance from the grower and did not hear anything from USDA-APHIS.  He does not know who did the testing.  The WERA group discussed the spread of zebra chip through infected tubers.  It was noted that transmission from infected seed tubers is rare, but can occur occasionally.  There were concerns by the group that APHIS does not always contact the state agency when potato seed issues arise.  Instead, they notify the U.S. Potato Board and state agencies are left out of the information loop.  Nina Zidack will be serving on the Seed Taskforce Committee and will bring this issue up at their next meeting.  Zidack suggested that all of the state potato seed agencies write case histories to demonstrate times when they found they were kept out of the information loop.    

CO  - Rob Davidson used a PowerPoint presentation provided by Andrew Houser, who could not attend the meeting this year, to present the seed report for Colorado.  He reported that Kent Sather is moving to North Dakota and will work with the seed program there.  Andrew Houser is now the Manager of the Colorado Potato Certification Service.  Greg Hess is now the disease testing Lab Supervisor.  Davidson reviewed the history of rejections for mosaic in Colorado.  He noted that there has been a drop in rejected acres since they adopted the Colorado Seed Potato Act, which lowered tolerance for mosaic viruses to 5% maximum in the post-harvest test.  They are seeing fewer lots with very high infection rates and think the new rules have helped significantly.  They are also seeing a cultivar shift to those with less susceptibility for PVY.  He noted excellent resistance to all PVY strains for ‘Fortress Russet’, ‘Masquerade’, and ‘Midnight Moon’. 

Davidson talked about the winter testing of Colorado seed lots in Hawaii.  He noted that any lots with over 1% mosaic in the second field inspection were ELISA tested in Hawaii, along with plants visually expressing mosaic in the winter grow-out.  Plants were tested individually.  There were 80 lots of 670 in 2015 with mosaic exceeding the 5% maximum tolerance.  Davidson noted that the Colorado Seed Potato Act has a maximum tolerance of no more than 1% PVY-N serotype strains.  There were two seed lots of 670 in 2015 with PVY-N/NTN over 1%.

ID -  Alan Westra reported that no PLRV was seen in the Idaho seed lots in 2015.  There were three lots with PLRV in the previous year sourced out of Canada.  The Canadian grower said he eased up on aphid controls.  Westra noted that PVY continues to be a significant problem.  The number of clean seed lots decreased 2013-2015, but is still an improvement over the years 2007-2009.  Leaf testing for all seed lots in the winter grow-out was implemented in 2008.  There was significant improvement in the number of clean seed lots after that, but more needs to be done.  Most of the planting stock is coming in with some PVY, but current-season spread is a problem, especially outside of the designated seed management areas in Idaho.  Westra suggested that growers need to focus on the fundamentals for managing current-season spread of PVY.     

Westra noted some concerns about the accuracy of leaf testing for PVY during the winter grow-out.  He said the timing of leaf picking is critical to get a good result.  Leaves picked too early, when the plants are less than 10 inches tall, can have low titer.  Leaves picked late can be problematic because plants tend to grow quickly in Hawaii and then it is difficult to differentiate individual plants.  In both cases, this can result in a tendency to underestimate PVY incidence.  Westra has found that the best results occur when they start picking at a plant height of 10-12 inches and then get it done within ten days.  Westra also studied the importance of composite sample sizes when testing PVY in the winter grow-outs.  He found that composite samples of 5-10 leaves for 400 plants can be good for up to 5% incidence, but can overestimate when incidence is higher than that.

Westra also reported on Idaho’s bacterial ring rot sampling program. 

MT -  Nina Zidack reported that Montana has implemented a garden potato seed program to provide Montana certified seed to gardeners.  There are concerns that potato seed used in home gardens can be a source for virus.  Zidack said the need is for small volumes of seed of many different varieties.

Zidack said that Ian MacRae, University of Minnesota, monitored aphids in the winter grow-out fields in Hawaii using suction traps.  There were very low numbers of aphids collected in Dec-Jan, suggesting that the current-season spread was not a big concern.

Zidack reported an increase in the incidence of PVY in Montana seed lots in 2015, which was not surprising given the significant aphid pressure noted during the 2015 growing season.  The winter grow-out results showed that 30% of seed lots had PVY incidence above the 0.5% tolerance.  She said they like to begin leaf picking for PVY testing at about 40 days after planting.  Zidack reported that G1, G2, or G3 seed lots with more than 0.1% PVY during the summer inspection have almost no chance of making the 0.5% tolerance at the winter grow-out.  It is too difficult to rogue anything over 0.1% in the summer. 

NE – Steve Marquardt reported that the Nebraska potato seed program rejected about 1% of the seed lots for PVY after the winter grow-out in Hawaii.  He noted that volunteer potatoes were a problem in Hawaii.  Cultivars with long tuber dormancy, like Canela Russet, can cause big problems for the winter grow-outs. 

WA -  Mark Pavek talked about the Commercial Seed Lot Trial that has been conducted in Washington every year since 1978.  In 2015, there were 310 seed lots entered in the trial and 52 different cultivars.  He noted an increase in the number of European cultivars.  Most of the seed in the trial was grown in Montana and Idaho.  He said approximately 50% of the seed lots had at least one plant with PVY.

 Project Reports: 

Darren Hall:  Use of Molecular Markers in Potato Breeding.  Hall summarized the objectives of the USDA-ARS Potato Breeding and Pathology Research Program in Aberdeen, ID and noted that much of their efforts have focused on resistance to PVY.  He talked about seed increases and some of the challenges with maintaining virus-free seed for trials and supplying that seed to cooperators.  They have increased rogueing and ELISA testing in second generation material, and are now culling out about 20%.  Neogen kits are being used in the summer for rogueing.  Hall talked about PVY resistance genes, hypersensitive response (Ny) and extreme resistance (Ry), and said they are most interested in extreme resistance against all strains.  They have been looking for molecular markers in second generation clones using a high throughput extraction procedure.  They are using S. andigena (Ry-adg) primers: RYSC# and ADG2/Bbv1; S. stoloniferum (Ry-sto) primers: Yes3-3A; and S. chacoense (Ry-chc) primers: Ry186 and Ry364.    

Ana Cristina Fulladolsa:  Progress in fine mapping the PVY resistance gene Rychc in a diploid potato population.  Fulladolsa discussed two different “pre-breeding” programs to identify molecular markers for virus resistance breeding.  The Wisconsin program identified several PVY resistant clones using markers for Rysto (YES3-3B marker) and Ryadg (RYSC3 marker).   They also confirmed that no major negative traits were associated with PVY resistance and those R genes.  Two PVY resistant S. chacoense clones were found in the core collection from the potato germplasm bank, but published markers linked to Rychc were not efficient in populations derived from the clones.  Shelley Jansky crossed the two resistant clones with US-W4 and other breeding clones with good agronomic traits. SNP genotyping of a population segregating for resistance revealed five SNPs with good correlations with resistance and all were on the end of chromosome IX. They developed PCR-based markers in the region close to the SNPs to use for further genotyping and mapping. They genotyped an XD3 (resistant S. chacoense x US-W4) selfed population and found some recombination (< 5 %) between the markers and the resistance gene, suggesting that the gene is further towards the end of the chromosome. They also found few susceptible individuals and think susceptibility may be associated with a lethal factor. They are continuing to cross XD3 with other clones to develop PVY resistant breeding clones with better agronomic traits.

Sudeep Bag: Coordinating the Vector and Disease Diversity of PVY.  Bag talked about projects that were conducted in Oregon to study population dynamics of aphids and their relationship with virus incidence, the role of weeds as alternate hosts for viruses, and the diversity of PVY strains.  Their trapping protocol for aphids included nine fields with four trap stations per field.  Each trap station included a bucket trap, a yellow sticky card, and a tile trap.  More aphids were collected in bucket traps than with other methods.  They sampled potato leaves at each trap station and tested them for PVY using ELISA and RT-PCR.  PVY incidence was positively correlated with aphid abundance.  The PVY positive leaves were tested for strains and they found PVY-NO (56%), PVY-O (10.3%), PVY-NTN (5.8%), and PVY-NO/NTN (1.1%).  They tested 66 weed samples (14 different types) for PVY and found it in only 1.5% of the samples. 

Alexander Karasev: PVY Survey Update.  Karasev reviewed PVY strain analysis of Idaho seed lots produced in 2014 and 2015 during the winter grow-out in Hawaii.  Seed lots from 2014 included 710 PVY positive samples of 754 mosaic samples tested.  These were typed as PVY-O (13%), PVY-NO/Wi (64%), PVY-NTN (16%), PVY-NE-11 (4%), and mixed or unclassified (3%).  They are working on the seed lots from 2015 now.  Of the 929 samples collected in the 2015 seed lots, 94% were PVY positive.  Karasev also reviewed the strain composition of commercial seed lots tested 2011-2015 in Othello, WA.  The seed lots are obtained from commercial producers in Washington.  The seed is sourced from several seed producing areas in the U.S. and Canada.  He noted dramatic changes in PVY strain composition in the field.  Incidence of PVY-O is decreasing, but recombinant strains are spreading including some that induce tuber necrotic ringspot disorder.  Karasev talked about a screen house study to compare seed-borne PVY symptom expression in four cultivars with three strains (O, NTN, and N-Wi).  He noted that ‘Russet Burbank’ has no strain-specific resistance to PVY, but weak non-specific resistance whereas ‘Alturas’, ‘Umatilla’ and ‘Ranger’ all have significant strain specific resistance against PVY-O.  ‘Alturas’, ‘Umatilla’ and ‘Ranger’ have increased susceptibility to PVY-NTN and PVY-N-Wi relative to ‘Burbank’.  Karasev noted that we are changing strain composition without intending to, because many new cultivars carry the Ny gene against PVY-O and some have the Nz gene against PVY-NTN, but almost no cultivars carry N genes selecting against N-Wi, NE-11, or other recombinants.   

Jonathan Whitworth: SCRI Necrotic Virus Grant – PMTV and TRV.  Whitworth discussed work being done by Whitworth, Gudmestad and Brown to study cultivar reactions to Potato Mop Top Virus (PMTV) and Tobacco Rattle Virus (TRV), and to identify markers for PMTV and TRV resistance breeding.  They compared more than 60 varieties and found a range in symptom expression for varieties planted in a plot with high TRV pressure.  Symptom expression ranged from a low of 0% incidence of corky ringspot in ‘AO03123-2’ to a high of over 90% incidence in ‘AO06191-1’.  They did the same with PMTV and found no internal symptoms in ‘A06021-1T’, ‘CO03202-1RU’, and ‘CO97087-2RU’.  ‘Umatilla’, ‘Pomerelle’, ‘Russet Burbank’, and ‘Russet Norkotah’ also had few internal symptoms.  The highest incidence of internal symptoms (25%) was in ‘Payette’ and ‘A03921-2’.  ‘POR06V12-3’ had low incidence of both TRV and PMTV symptoms.  This clone is being used in a cross with ‘A06084-1TE’ to develop a segregating population for marker development.

Carrie Wohleb: Extension Efforts to Help Washington’s Potato Industry Monitor and Manage Important Insect Pests.  Wohleb talked about the insect monitoring network she coordinates in the Columbia Basin of Washington.  She gave an overview of the program, reviewed seasonal insect pest population patterns, and talked about the pest density population maps that were developed to provide a visual indication of pest population distribution.  Wohleb said they are working on using monitoring data and phenology models to develop maps that forecast pest population densities one or two weeks out.

Election:  Andrew Houser will move from Vice Chair to Chair. Ken Frost will move from Secretary to Vice Chair.  Matthew Blua was unanimously elected to serve as the Secretary.

WERA-89 Meeting in 2017:  Most of the people in attendance agree that the second week of March will be the best time to hold the 2017 WERA89 meeting, but we were reluctant to set a date.  It was suggested that the Chair, Andrew Houser, poll the WERA89 group to decide which week in March 2017 will be the best for all WERA89 participants.  The consensus was that San Diego or San Antonio would be the best locations for the meeting.  The 2015-16 Chair, Carrie Wohleb, suggested that Andrew Houser should start the meeting planning process in the late summer or fall of 2016 since there are usually challenges with finding a good venue and signing contracts.  Also, participants need lead time to get approval to attend the meeting and make flight reservations.      

The meeting adjourned at 10:00 am March 3, 2016.

PVY Assessment during Winter Grow-out of Seed Potatoes in Hawaii

Personnel from several states who conduct PVY assessments during winter grow-out of seed potatoes in Hawaii shared observations and compared methods.  The information they shared will lead to improved results for all programs.  It is clear that the timing of leaf picking is critical for getting accurate results for PVY testing.  Alan Westra from the Idaho Crop Improvement Program reported that the best results occur when they start collecting leaves at a plant height of 10-12 inches and then get it done within 10 days.  He noted that leaves picked too early, when the plants are smaller than 10 inches tall, can have low virus titer.  Leaves picked late can be problematic because plants tend to grow quickly in Hawaii and it is difficult to differentiate individual plants when they are large.  In both cases, there is a tendency to underestimate PVY incidence.  Westra also studied the importance of composite sample sizes when testing PVY in the winter grow-outs.  He found that composite samples of 5-10 leaves for 400 plants can be good for up to 5% incidence, but can overestimate when incidence is higher than that.

Ian MacRae, University of Minnesota, monitored aphids in the winter grow-out fields in Hawaii using suction traps in 2015-16.  There were very low numbers of aphids collected in Dec-Jan, suggesting that the current-season spread of virus was not a big concern.  

Personnel from several state programs noted concerns about including cultivars with long tuber dormancy, like Canela Russet, in the winter grow-outs.  These cultivars are difficult to assess for virus because of poor emergence, and they have also led to some problems as volunteer potatoes in the following year.

PVY Strain Diversity in Potato Cultivars and Practical Consequences of Strain-specific Resistance

Strain composition studies since 2011 have shown that incidence of PVY-O is decreasing in the U.S., but recombinant strains are spreading including some that induce tuber necrotic ringspot disorder.  What is driving this change in strains? Alexander Karasev suggested that we are changing strain composition without intending to, because many new cultivars carry the Ny gene against PVY-O and some have the Nz gene against PVY-NTN, but almost no cultivars carry N genes selecting against N-Wi, NE-11, or other recombinants.  Hypersensitivity resistance (HR) to PVY conferred by N genes is strain specific. 

Developing Molecular Markers to Assist in Breeding Potato Cultivars Resistant to PVY

Potato breeding programs in the Pacific Northwest and Midwest have focused a lot of effort on developing new cultivars with resistance to PVY.  Since multiple PVY strains are occurring in potato production areas, breeders are  most interested in breeding for extreme resistance to PVY using R genes that are non-strain specific. The Ry-adg, Ry-sto, and Ry-chc genes provide durable resistance against all strains of PVY.  Molecular markers associated with these genes are being identified and used to identify early selections from crosses with these genes. The breeders at the USDA-ARS Potato Breeding Program in Idaho have been looking for molecular markers in second generation clones using a high throughput extraction procedure.  They are using S. andigena (Ry-adg) primers: RYSC# and ADG2/Bbv1; S. stoloniferum (Ry-sto) primers: Yes3-3A; and S. chacoense (Ry-chc) primers: Ry186 and Ry364. The Wisconsin breeding program identified several resistant clones using markers for Rysto (YES3-3B marker) and Ryadg (RYSC3 marker).  They also confirmed that no major negative traits were associated with those R genes.  Two PVY resistant S. chacoense clones were found in the core collection from the potato germplasm bank, but published markers linked to Rychc were not efficient in populations derived from the clones.  Shelley Jansky crossed the resistant clones with US-W4 and other breeding clones with good agronomic traits. SNP genotyping of a population segregating for resistance revealed five SNPs with good correlations with resistance and all were on the end of chromosome IX. They developed PCR-based markers to use for rapid genotyping and mapping. Their results suggest that the Rychc gene is further towards the end of the long arm of chromosome IX and that PVY susceptibility in their population may be linked to a lethal factor. The breeders continue to cross the resistant materials with clones that have good agronomic traits and evaluating them for resistance, fertility, yield, and quality.

Screening Clones and Cultivars for Potato Mop Top Virus and Tobacco Rattle Virus Resistance

Potato breeding programs are focusing more on developing cultivars resistant to PMTV and TRV.  Whitworth discussed work being done by Whitworth, Gudmestad and Brown to study cultivar reactions to PMTV and TRV, and to identify markers for PMTV and TRV resistance breeding.  They compared more than 60 clones and cultivars and found a range in symptom expression for varieties planted in a plot with high TRV pressure.  Symptom expression ranged from a low of 0% incidence of corky ringspot in ‘AO03123-2’ to a high of over 90% incidence in ‘AO06191-1’.  They did the same with PMTV and found no internal tuber symptoms in ‘A06021-1T’, ‘CO03202-1RU’, and ‘CO97087-2RU’.  ‘Umatilla’, ‘Pomerelle’, ‘Russet Burbank’, and ‘Russet Norkotah’ also had few internal symptoms.  The highest incidence of internal symptoms (25%) was in ‘Payette’ and ‘A03921-2’.  ‘POR06V12-3’ had low incidence of both TRV and PMTV tuber symptoms.  This clone is being used in a cross with ‘A06084-1TE’ to develop a segregating population for marker development.  This is an important step toward developing more cultivars with resistance to potato tuber necrotic diseases.

Potato Virus Detection Training

WERA 89 participants from the USDA, University of Idaho, Montana State University, Washington State University, and the University of Wisconsin have been developing a potato virus detection training for growers, inspectors, regulators, and anyone interested in learning more about detection of PVY, PMTV and TRV in field applications.  The training will take place at the WSU Othello Agricultural Research & Extension Center on June 20, 2016.  They will be demonstrating 40 popular cultivars infected with three PVY strains (O, N-Wi, and NTN).  They plan to show tuber symptoms of PVY, PMTV and TRV.  They will also update attendees on the latest diagnostic assays for viruses and their vectors.

Benedict, C., McMoran, D., Inglis, D., and Karasev, A.V. (2015) Tuber symptoms associated with recombinant strains of Potato virus Y in specialty potatoes under northwestern Washington growing conditions. American Journal of Potato Research 92: 593-602. Fig. 1 of this paper has been selected for the cover of the October issue of American Journal of Potato Research.

Cating, R.A., Funke, C.N., Kaur, N., Hamm, P.B., and K.E. Frost. (2015) A multiplex reverse transcription (RT) high-fidelity PCR protocol for the detection of six viruses that cause potato tuber necrosis. The American Journal of Potato Research 92 :850-864.

Chikh-Ali, M., Bosque-Perez, N., **Vander Pol, D., Sembel, D., and Karasev, A.V. (2016) Occurrence and molecular characterization of recombinant Potato virus YNTN (PVYNTN) isolates from Sulawesi, Indonesia. Plant Disease 100: 269-275.

Chikh-Ali, M., *Alruwaili, H., **Vander Pol, D., and Karasev, A.V. (2016) Molecular characterization of recombinant strains of Potato virus Y from Saudi Arabia. Plant Disease 100: 292-297.

DeBlasio, S.L., Johnson, R., Mahoney, J., Karasev, A.V., Gray, S.M., MacCoss, M.J., and Cilia, M. (2015) Insights into the polerovirus-plant interactome revealed by co-immunoprecipitation and mass spectrometry. Molecular Plant-Microbe Interactions 28: 467-481.

DeBlasio, S.L., Johnson, R., Sweeney, M.M., Karasev, A.V., Gray, S.M., MacCoss, M.J., and Cilia, M. (2015) The Potato leafroll virus structural proteins manipulate overlapping, yet distinct protein interaction networks during infection. Proteomics 15: 2098-2112.

Fulladolsa, A.C., F.M. Navarro, R. Kota, K. Severson, J.P. Palta, and A.O. Charkowski. (2015) Application of marker assisted selection for Potato virus Y resistance in the University of Wisconsin Potato Breeding Program. Am. J. Pot. Res. 92:444-450.

Mondal, S.; E. J. Wenninger; P. J. S. Hutchinson; J. L. Whitworth; D. Shrestha; S. D. Eigenbrode, and N. A. Bosque-Perez. (2016) Comparison of transmission efficiency of various isolates of Potato virus Y among three aphid vectors. Entomologia Experimentalis et Applicata 158: 258-268.

Rowley, J.S., Gray, S.M., and Karasev, A.V. (2015) Screening potato cultivars for new sources of resistance to Potato virus Y. American Journal of Potato Research 92: 38-48. – Fig. 8 of this paper has been selected for the cover of the February issue of American Journal of Potato Research.

Wohleb, C.H., T.D. Waters, E.M. D’Auria, and D.W. Crowder. (2015) WSU Potato Pest Alerts – Providing Regional Pest Information and IPM-based Recommendations to Aid Management Decisions. Abstracts of the Papers Presented at the 99^th Annual Meeting of the Potato Association of America. Am. J. of Potato Res., 93(2).

Wohleb, C.H. (2015) Development and impact of a pest alert system for potato growers in the Columbia Basin of Washington. 8^th International IPM Symposium.