Source: CORNELL UNIVERSITY submitted to NRP
DEVELOPMENT OF POTATO SCAB RESISTANCE THROUGH MOLECULAR GENETIC ANALYSIS OF HOST-PATHOGEN INTERACTIONS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0152460
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 2000
Project End Date
Sep 30, 2005
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853
Performing Department
PLANT PATHOLOGY
Non Technical Summary
Two strategies will be used in this summary. This will be done through heterologous expression and disruption of putative pathogenicity genes. DNA sequence and Southern analysis will be utilized to determine which of these pathogencity genes is conserved across all four pathogenic species. The second strategy will be to identify the targets for each of the pathogenicity determinants in host cells. This will be done through genetic analysis of model plant species such as Arabidopsis and tomato.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
21213101160100%
Knowledge Area
212 - Pathogens and Nematodes Affecting Plants;

Subject Of Investigation
1310 - Potato;

Field Of Science
1160 - Pathology;
Goals / Objectives
1. Identify the mechanisms by which Streptomyces species cause potato scab. 2. Characterize the plant cell targets for these pathogenicity determinants in order to develop strategies for breeding of scab-resistant potato varieties.
Project Methods
Two strategies will be used in this research. Genetic analysis of pathogenicity determinants in Streptomyces spp. will identify the mechanisms by which these pathogens cause disease. This will be done through heterologous expression and disruption of putative pathogenicity genes. The second strategy will be to identify the targets for each of the pathogenicity determinants in host cells. This will be done through genetic analysis of model plant species such as Arabidopsis and tomato.

Progress 10/01/00 to 09/30/05

Outputs
Among the multitude of soil-inhabiting, saprophytic Streptomyces species, there are a growing number of plant pathogens that cause economically important diseases, including potato scab. Streptomyces scabies is the dominant pathogenic species world-wide, but is only one of many that cause very similar disease symptoms on plants. A remarkably diverse group of streptomyces have been reported as pathogens of plants. Molecular genetic analysis is beginning to identify the mechanisms used by plant pathogenic species to manipulate their hosts. Based on our knowledge of the mechanism of action and symptomology of thaxtomin, it is safe to say that all Streptomyces species that can produce these scab symptoms are thaxtomin producers. This toxin and other members of the thaxtomin family induces necrosis on excised potato tuber tissue and produces scab-like symptoms on immature potato tubers. These biological activities suggest that thaxtomin plays a critical role in the pathogencity of producing strains. The commonality of thaxtomin production across multiple scab-causing species isolated from many geographic locations supports the hypothesis that this toxin is a pathogenicity determinant on potato tubers. Inhibition of seedling growth by thaxtomin implicated the toxin in seedling infection. Eventually, disruption and complementation of the thaxtomin genes demonstrated that this molecule was required for pathogenicity. Clearly, acquisition of the thaxtomin biosynthetic pathway was a watershed event in the evolution of pathogenicity in Streptomyces. Inhibition of seedling growth by thaxtomin suggested that thaxtomin might be interfering with cell division. Studies with onion root tip cells supported a role for thaxtomin in inhibition of cytokinesis. Abnormalities at cytokinesis, including the occurrence of cell plate deformities is consistent with a thaxtomin interaction with a cell wall target. Cell hypertrophy in onion and tobacco cells exposed to thaxtomin suggests that thaxtomin is affecting the integrity of the cell wall in expanding cells. Taken together, these data indicated that thaxtomin is a cellulose biosynthesis inhibitor. The nec1 gene was discovered in a genetic screen designed to identify thaxtomin biosynthetic genes. Deletion analysis identified a 666 bp gene, nec1, which allows the nonpathogen S. lividans to necrotize and colonize potato tuber slices. The Nec1 protein has an N-terminal secretion signal and is secreted into culture media in the early log phase, suggesting that Nec1 directly interacts with the host plant. The thaxtomin biosynthetic genes and nec1 lie on a large mobilizable PAI, along with other putative virulence genes including a cytokinin biosynthetic pathway and a saponinase homolog. The PAI is mobilized during conjugation and site specifically inserts in the linear chromosome of recipient species. The efficient transfer of the S. turgidiscabies PAI to saprophytic Streptomyces sp. in vitro suggests that mobilization of pathogenicity determinants among Streptomyces species occurs frequently in nature, accounting for the emergence of new pathogens in agricultural systems

Impacts
This research has provided the knowledge necessary to improve strategies for controlling potato scab. Our new knowledge about the molecular genetics of pathogenicity demonstrated that thaxtomin and the secreted protein Nec1 have plant cell targets that are conserved across plant families. Identifying resistance genes to a pathogen that targets highly conserved plant cell components and avoids host surveillance is a difficult task. Therefore this work suggests that new strategies should be used in developing scab resistant crops.

Publications

  • No publications reported this period


Progress 01/01/04 to 12/31/04

Outputs
Potato scab disease is a globally important disease caused by polyphyletic plant pathogenic Streptomyces spp. Streptomyces acidiscabies, S. scabies, and S. turgidiscabies possess a conserved biosynthetic pathway for the nitrated dipeptide phytotoxin thaxtomin. These pathogens also possess the nec1 gene which encodes a necrogenic protein that is an independent virulence factor. IWe have discovered a large (325-660 kb) pathogenicity island (PAI) conserved among these three plant pathogenic Streptomyces species. A partial DNA sequence of this PAI revealed the thaxtomin biosynthetic pathway, nec1, a putative tomatinase gene, and many mobile genetic elements. In addition, the PAI from S. turgidiscabies contains a plant fasciation (fas) operon homologous to and collinear with the six-gene fas operon in the plant pathogen Rhodococcus fascians. The PAI was mobilized during mating from S. turgidiscabies to the nonpathogens S. coelicolor and S. diastatochromogenes on a 660 kb DNA element and integrated site-specifically into a putative integral membrane lipid kinase. Acquisition of the PAI conferred a pathogenic phenotype on S. diastatochromogenes but not on S. coelicolor. This is the first PAI is the first to be described in a Gram-positive plant pathogenic bacterium, the largest PAI described to date, and provides a model is responsible for the emergence of new plant pathogenic Streptomyces species in agricultural systems.

Impacts
These results demonstrate the key role that thaxtomin plays in pathogenicity and the role of the pathogenicity island in the evolution of new potato scab causing Streptomyces species. Thaxtomin appears to facilitate disease by compromising the structure of the primary plant cell wall, allowing penetration of the pathogen directly into plant cells. This information should be useful in the development of scab-resistant potato varieties.

Publications

  • Kers, J.A.; K.D. Cameron, M.V. Joshi, R.A. Bukhalid, J.E. Morello, M.J. Wach, D.M. Gibson, and R. Loria. 2005. A large, mobile pathogenicity island confers plant pathogenicity on Streptomyces species. Molecular Microbiology 55(4): 1025-1033.


Progress 01/01/03 to 12/31/03

Outputs
Thaxtomin A is a phytotoxin produced by the gram-positive filamentous bacterium Streptomyces scabies and other Streptomyces species which cause the common scab disease in potato. At nanomolar concentrations, thaxtomin causes dramatic cell swelling and reduced growth of seedlings. We identified a mutant of Arabidopsis, designated txr1, which exhibited resistance to thaxtomin due to a difference in the rate of uptake of the toxin. The TXR1 gene was identified by map-based cloning and found to encode a novel, small protein with no apparent motifs or organelle targeting signals. The protein, which has homologs in all fully sequenced eukaryotic genomes, is expressed in all tissues of the plant. Microarray analysis of the effect of the mutation on the expression of 14,300 genes identified two stomatin-like genes that exhibited altered expression. We propose that TXR1 is a component of, or regulator of, a dispensable transport mechanism.

Impacts
These results demonstrate the key role that thaxtomin plays in pathogenicity and implicate cellulose synthase as a direct or indirect target for this phytotoxin. Thaxtomin appears to facilitate disease by compromising the structure of the primary plant cell wall, allowing penetration of the pathogen directly into plant cells. Intracellular growth is a novel attribute of the potato scab pathogens relative to other bacterial plant pathogens. This information should be useful in the development of scab-resistant potato varieties.

Publications

  • Scheible, W.-R., B. Fry, A. Kochevenko, D. Schindelasch, L. Zimmerli, S. Somerville, R. Loria, and C.R. Somerville. 2003. An arabidopsis mutant resistant to thastomin A, a celluylose synthesis inhibitor from Streptomyces species. The Plant Cell 15:1781-1794.


Progress 01/01/02 to 12/31/02

Outputs
Potato scab is an economically important disease that afflicts most potato producers . Loses to individual growers are often exceed $100,000 in one year. Control strategies provide only incremental decreases in disease, at best. High levels of disease resistance has been a goal for potato breeding programs, but relatively few varieties with passable levels of scab resistance are grown in the United States. New strategies need to be based on detailed knowledge of the host-pathogen interactions at the molecular level. We are dissecting the genes involved in pathogenicity in scab-causing streptomycetes, and at the same time, conducting a molecular analysis of host plant response. Our studies have determined that thaxtomin, a phytotoxin produced by scab causing pathogens, is required for pathogenicity and is a cellulose biosynthesis inhibitor. These data have important implications for the development of scabs resistant potato varieties.

Impacts
The results of this study are consistent with the experience of potato breeders interested in developing scab resistant potato varieties. Since the toxin has an important role in pathogenicity and has a conserved and vital target in the plant cell, it is not surprising that scab resistance is hard to achieve.

Publications

  • Fry, B.A. and Loria, R. 2002. Thaxtomin A: evidence for a plant cell wall target. Physiol. Molec. Plant Path. 60:1-8.


Progress 01/01/01 to 12/31/01

Outputs
Potato scab is an economically important disease that afflicts most potato producers . Losses to individual growers are often exceed $100,000 in one year. Control strategies provide only incremental decreases in disease, at best. High levels of disease resistance has been a goal for potato breeding programs, but relatively few varieties with passable levels of scab resistance are grown in the United States. New strategies need to be based on detailed knowledge of the host-pathogen interactions at the molecular level. We are dissecting the genes involved in pathogenicity in scab-causing streptomycetes, and at the same time, conducting a molecular analysis of host plant response. Our studies have determined that thaxtomin, a phytotoxin produced by scab causing pathogens, is required for pathogenicity and is interacting with a conserved plant cell target. We are mapping plant genes that confer resistance to the toxin and identifying the conserved molecular target within plant cells that the toxin interacts with. Our data support a model for thaxtomin as a cellulose biosynthesis inhibitor.

Impacts
Impact: Understanding of the role of horizontal gene transfer among soil borne microbes will lead to more stable disease control strategies

Publications

  • Stevenson, W. R., R. Loria, G. Granc, W. P. Weingartner (eds). 2001. Potato disease compendium. Am. Phytopathol. Soc., St. Paul, MN.
  • Loria, R. 2001. Potato scab. In: Potato disease compendium. Stevenson, W. R., R. Loria, G. Franc, W. P. Weingartner eds. Am. Phytopathol. Soc., St. Paul, MN.
  • Loria, R. 2001. Potato scab. Pages 241-242. In: Encyclopedia of Plant Pathology. O. C. Maloy and T. D. Murray, eds., John Wiley & Sons, Inc.
  • Loria, R., Bukhalid, R. A., Fry, B. A., Clark, C. A. Streptomyces spp. 2001. In: Laboratory guide for identification of plant pathogenic bacteria. N. W. Schaad, ed., Am. Phytopathol. Soc., St. Paul, MN.


Progress 01/01/00 to 12/31/00

Outputs
Helminthosporium solani causes silver scurf, a disease of the potato tuber periderm. Infected tubers develop tan to gray lesions that are often clustered at the stolon end of the tuber; lesions have a distinct silvery sheen. At present, no effective disease control strategies are available for silver scurf, and economic losses are significant. Two PCR primer pairs specific for Helminthosporium solani, were designed from nucleotide sequences of the nuclear ribosomal internal transcribed spacer regions of H. solani. Both primer pairs amplified a single product with DNA from 40 North American isolates of H. solani, but not with DNA from 42 other fungi. Primers also amplified a single product with DNA extracted from silver scurf lesions on potato tubers and other plant tissue inoculated with spores of H. solani. Detection of the fungus in soil infested with spores was only possible after processing infested soil with a bead beater. Specific amplification of H. solani DNA can be used to study the saprophytic and pathogenic activity of this fungus in soil and plant tissue .

Impacts
DNA based detection of plant pathogens is more sensitive and efficient than conventional detection methods. We developed species specific PCR primers for the silver scurf pathogen which can be used to detect the fungus in infected plant tissue and soil. This technique will allow development of improved pathogen monitoring.

Publications

  • Olivier, C., Berbee, M.L., Shoemaker, R. A. and Loria, R. 2000.Molecular phylogenetic support from ribosomal DNA sequences for origin of Helminthosorium from Leptosphaeria-like loculoascomycete ancestors. Mycologia 92:736-746.


Progress 01/01/99 to 12/31/99

Outputs
The objective of this project is to develop technologies for pathogen detection and disease management. Helminthosporium solani, the golden nematode and Potato virus Y (PVY) are important pathogens of potato. PVY resistant transgenic potatoes (cultivars Atlantic and Pito) that use promoters other than the 35S promoter (Ubiquitin 3 from tomato, Ubiquitin 10 from potato, and the Cassava Vein Mosaic Promoter) to express the PVY replicase gene and PVY nontranslateable coat protein gene were generated. PVY resistance appeared to be comparable to similar transgenic potatoes which used the 35S promoter. Organic salt applications were demonstrated to suppress the sporulation of H. solani and the development of silver scurf on field-grown, naturally infected potato tubers. The advanced potato clone NY121 was developed with resistance to race Ro1 and Ro2 of the golden nematode that occurs in New York. After two years of growing NY121 in plots infested with both races, the golden nematode population density declined 96%. These experimental results will lead to improvements in the control of plant disease without an increase in pesticide usage.

Impacts
(N/A)

Publications

  • Chacon, M. G., Plaisted, R. L., & Brodie, B. B. 1999. Inheritance of the resistance to Globodera rostochiensis pathotype Ro2 in potato. Amer. J. of Potato Res. 76:345-349.
  • Olivier, C., C.R. MacNeil, & R. Loria. 1999. Application of organic and inorganic salts to field-grown potato tubers can suppress silver scurf damage. Plant Disease 83:814-818.
  • Souza-Dias, J.A.C., Russo, P., Miller, L. & Slack S. 1999. Comparison of nucleotide sequences from three Potato Leafroll Virus (PLRV) isolates collected in Brazil. American Journal of Potato Research 76:17-24.
  • Souza-Dias, J.A.C., Russo, P., Betti, J.A., Miller, L., & Slack, S. 1999. Simplified extraction method for ELISA and PCR detection of potato leafroll luteovirus primary infection in dormant potato tubers. American Journal of Potato Research 76:209-213.
  • Russo, P., Miller, L., Singh, R. P., & Slack, S. 1999. Comparison of PLRV & PVY detection in potato seed samples tested by Florida winter test field inspection & RT-PCR. American Journal of Potato Research 76:313-316.


Progress 01/01/98 to 12/31/98

Outputs
The objective of this project is to develop approaches by which pathogen-free seed potato stocks can be developed and maintained, and by which management approaches to minimize disease can be implemented through enhanced epidemiologic knowledge. DNA-based technology has been utilized to assess seed potato health and detect and monitor the silver scurf of potato caused by Helminothosporium solani. The usefulness of nontoxic organic and inorganic salts for postharvest control of silver scurf has also been demonstrated. Disease resistant cultivars have been obtained via traditional breeding methods and bioengineering approaches, including immunity to golden nematode (Race Ro1) and outstanding resistance to potato scab. Transgenic virus resistance has been demonstrated under laboratory and field conditions with current efforts stressing efficient transformation and disease-resistance screening methods. These studies will impact the potato industry by decreasing losses due to disease and by improving seed and commercial potato quality for consumers.

Impacts
(N/A)

Publications

  • Olivier, C., and Loria, R. 1998. Detection of Helminthosporium solani from soil and plant tissue from species-specific PCR primers FEMS microbiology letters 168:235-241.
  • Olivier, C., MacNeil, C. R., and Loria, R. 1998. Application of organic and inorganic salts to field-grown potato tubers can suppress silver scurf damage. Plant Disease 82:213-217.
  • Plaisted, R. L., Halseth, D. E., Brodie, B. B., Slack, S. A., Sieczka, J. B., Christ, B. J., Paddock, K. M., and Peck, M. W. 1998. Andover: An early to midseason golden nematode resistant variety for use as chipstock or tablestock. Amer. J. Potato Res. 75:113-116.
  • Plaisted, R. L., Halseth, D. E., Brodie, B. B., Slack, S. A., Sieczka, J. B., Christ, B. J., Paddock, K. M. and Peck, M. W. 1998. Pike: A full season scab and golden nematode resistant chipstock. Amer. J. Potato Res. 75:117-120.
  • Russo, P., and Slack, S. A. 1998. Tissue culture methods for the screening and analysis of putative virus resistant transgenic potato plants. Phytopathology 88:437-441.
  • Celebi, F., Russo, P., Watanabe, K. Valkonen, J. P. T., and Slack, S. A. 1998. Resistance of potato to cucumber mosaic virus appears related to localization in inoculated leaves. Amer. J. Potato Res. 75:195-199.
  • Slack, S. A. and German, T. L. 1998. Impact of transgenic viral resistance on seed potato certification. Amer. J. Potato Res. 75:265-268.
  • Slack, S. A., and Westra, A.A.G. 1998. Evaluation of flusulfamide for the control of bacterial ring rot of potato. Amer. J. Potato Res. 75:225-230.
  • Slack, S. A. 1998. New technology aids quality assessment of potato seed stocks: Nucleic acid-based testing as the next paradigm for assessing seed potato health. The Badger Common' Tater 50:22-23.


Progress 01/01/97 to 12/31/97

Outputs
The objective of this project is to develop methods by which the production of pathogen-free stocks can be developed. We have been developing DNA-based assays to detect pathogens which will likely enhance abilities to specify reactivity and sensitivity of assays on basic stocks in the future. We have also been utilizing DNA technology to alter susceptibility of potato cultivars to infection by viral pathogens. We are trying to understand the mechanisms of resistance to viruses in order to map the genetic bases for resistances within species and among related plant species, an effort that will impact future approaches to genetically modifying potatoes to enhance pathogen resistance in the future. We have also been performing field tests to see how pathogen-free stocks perform following generational field increases where reinfection by primary pathogens is not a variable. Current data suggest that yields do decrease with increased years of propagation. These studies will be influential in quality control approaches taken by the seed potato industry in the future.

Impacts
(N/A)

Publications

  • Suzuki, T., Watanabe, K. N., Zaitlin, M., Nakamura, C., and Slack, S. A. 1997. Comparison of transformation methods in potato using a fluorometric GUS transient assay. Me. Grad School Sci. & Tech., Kobe
  • Suzuki, T., Watanabe, K. N., Zaitlin, M., Nakamura, C., and Slack, S. A. 1997. Comparison of transformation methods in potato using a fluorometric Hamalainen, J. H., Watanabe, K. N., Valkonen, J.P.T.,
  • Celebi, F., Russo, P., Watanabe, K., Valkonen, J.P.T., and Slack, S. A. 1997. Resistance of potato to cucumber mosaic virus appears related to localization in inoculated leaves. Phytopathology 87:S16.
  • Souza-Dias, J.A.C., de, Russo, P., Miller, L., and Slack, S. A. 1997. Nucleotide sequence comparison of three potato leafroll virus (PLRV) isolates from Brazil suggest a common origin. Phytopathology 87:S24.
  • Russo, P., and Slack, S. A. 1997. Tissue culture methods for the screening and analysis of putative potato virus Y (PVY) resistant transgenic potato plants. Phytopathology 87:S84.
  • Souza-Dias, J.A.C. de, Russo, P., Betti, J. A., Miller, L., & Slack, S. A. 1997. A simplified extraction method for ELISA & PCR detection of primary potato leafroll virus (PLRV) infection in dormant potato tubers. Amer. Potato J. 74:368


Progress 01/01/96 to 12/30/96

Outputs
The objective of this project is to develop methods by which the production of pathogen-free potato stocks can be enhanced. A book chapter detailed the significance and role of indexing procedures in potato certification in North America and Europe. Other studies demonstrated the impact of virus-specific and strain-specific resistance responses to delimiting potyviruses and cucumber mosaic virus in potatoes. A study comparing PCR, ELISA, and DNA hybridization techniques showed that PCR was specific and sensitive for detection of Clavibacter michiganensis subsp. sepedonicus in growing plants but that test stringency needed to be adjusted for detection in plants and tubers compared to bacterial cultures. A CD-Rom with 149 images and a 20 page booklet as well as a 2 page picture set were released on the bacterial ring rot disease caused by C.m. subsp. sepedonicus. These studies and materials will help the seed potato industry produce basic seed stocks which are disease-free.

Impacts
(N/A)

Publications

  • DeBoer,S.H., Slack, S.A, et al.A role for pathogen indexing procedures in potato certification. In Advances in bot res incorporating advances in plant path, eds. DeBoer, Andrews, Tommerup, & Callow,pp.217-242. Acad Press, London. 1996
  • Slack, S. A., Drennan, J. L., Westra, A. A. G., Gudmestad, N. C. & Oleson, A. E.Comparison of PCR, ELISA,& DNA hybridization for the detection of Clavibacter mighiganensis subsp. sepedonicus in field grown potatoes. Plt Dis 80:519-24. 1996
  • Slack, S. A., Melching, J. B., & Lawrence, D. Yield enhancement of nuclear generation seed stocks. 2 pp. Proceedings, New York State Vegetable Conference, 6-8 Feb, Syracuse, NY. 1996.
  • Slack, S. A., & Westra, A. A. G. BRR on CD-Rom. vl.o. 149 imaes + 20 page booklet. 1996.
  • Slack, S. A. & Westra, A.A.G. Foliar symptoms of bacterial ring rot of potato. 6 pictures + table on cultivar responses. 2pp. 1996.
  • Valkonen, J.P.T., Kyle, M. & Slack, S. 1996. Comparison of resistance to potyviruses within Solanaceae:infection of potatoes with tobacco etch potyvirus & peppers with potato A & Y potyviruses. Ann. Appl. Biol. 129:25-38.
  • Valkonen, J.P.T., Watanabe, K. N., Tufford, L., & Slack, S. A. 1996. Resistance to cucumber mosaic virus (cmv) in potato germplasm. Amer. Potato J. 73:389-390.


Progress 01/01/95 to 12/30/95

Outputs
Efforts to consolidate seed certification efforts were recorded in publications which indicate a regulation summary by state (Slack, Common' Tater 47:27) and how therapy of tissue culture plantlets can provide pathogen-tested Solanum spp. suitable for germplasm exchange where phytosanitary concerns exist (Slack and Tufford, in Plant Cell, Tissue & Organ Culture pp 117-128). Resistance studies included an evaluation of cucumber mosaic virus resistance in potato. Resistance varied with CMV isolate and potato genotype. (Valkonen et al., Ann. Appl Biol 126:143), and transgenic modification of potato with somatic variation due to methodology noted for Solanum brevidens (Valkonen et. al., Plant Science 106:71) Agrobacterium transformation was better than biolistic transformation as measured by fluorometry (Suzuki et al., Amer Pot J. 72:658). Studies on potato A potyvirus demonstrated the existence of at least three viral strain groups and variability in the hypersensitive response of potato cultivars to PVA infection according to the PVA strain group used for inoculations (Valkonen, et. al., Plant Disease 79:748).

Impacts
(N/A)

Publications

  • SLACK, S. A. & WESTRA, A. A. G. 1995. Foliar symptoms of bacterial ring rot of potato. Pictorial Fact Sheet (dist. through certification section, Potato Assoc. America). 2pp.
  • SLACK, S. A. 1995. Seed potato certification regulations. The Badger Common `Tater 47:27-31.
  • SUZUKI, T., WATANABE, K. N., ZAITLIN, M., & SLACK, S. A. 1995. Comparison of transformation methods in potato using a transient gus fluorometric assay. Plant Pathology Department, Cornell University, Ithaca, NY 14853.
  • VALKONEN, J. P. T., KOIVU, K., SLACK, S. A. & PEHU, E. 1995. Modified resistance of Solanum brevidens to potato Y potyvirus & tobacco mosaic tobamovirus following genetic transformation & explant regeneration. Plant Sci 106:71-79.
  • VALKONEN, J. P. T., SLACK, S. A., & WATANABE, K. N. 1995. Resistance to cucumber mosaic virus in potato. Ann. Appl. Biol. 126:143-51.
  • SLACK, S. A., & TUFFORD, L. A. 1995. Meristem culture for virus elimination. In "Plant Cell, Tissue and Organ Culture:Fundamental Methods". O. L. Gamborg & G. S. Phillips, eds. Springer-Verlag, Berlin Heidelberg, NY. pp. 117-128.
  • VALKONEN, J. P. T., PUURAND, U., SLACK, S. A., MAKINEN, K., & SAARMA, M. 1995. Three strain groups of potato A potyvirus based on hypersensitive response in potato, serological properties, and coat protein sequences. Plant Disease 79:748-75


Progress 01/01/94 to 12/30/94

Outputs
Transgenic replicase-mediated (NIb gene) resistance to PVY was demonstrated in tobacco. Resistance appeared to be specific to the PVY-O strain and not the PVY-N strain. Traditional crosses were used to separate extreme and hypersensitive resistance genes to PVY in potato. Evidence suggests that extreme resistance is epistatic to hypersensitive resistance. The strain groups used for PVX, PVY and PVA were established with PVX strain group 3 and evidence for two PVA strain groups being documented. Since cultivar resistance response varies by strain group, these data are significant in determining cultivar resistance in a geographic location and in comparing resistances with other countries. A russeted sport of the Bake-King potato cultivar was released. Since New York does not have a russet cultivar adapted for its cultural conditions, this sport provides a fresh market niche for New York producers. Bacterial ring rot detection by PCR and a comparison of diagnostic techniques were reported, the PCR technique offers greater sensitivity than existing tests but needs to be adapted to mass testing protocols. Quantitative differences in the development of ring rot foliar symptoms and the magnitude of symptom expression were demonstrated across several geographic locations. Inoculum dose was positively correlated with expression of foliar and external tuber symptoms and negatively correlated with total yield and vine length. Response magnitude was modulated by cultivar x location interaction.

Impacts
(N/A)

Publications

  • AUDY, P., PALUKAITIS, P., SLACK, S. A., AND ZAITLIN, M. 1994. Replicase-mediated resistance to PVY in transgenic tobacco plants. MPMI 7:15-22.
  • LAWRENCE, D. F., SLACK. S. A., AND PLAISTED, R. L. 1994. Russet Bake-King, a uniform russeted sport of Bake-King. Amer. Potato J. 71:127-129.
  • VALKONEN, J. P. T., SLACK, S. A., AND PLAISTED, R. L. 1994. Use of the virus strain group concept to characterize the resistance to PVX and PVYO in the potato cv. Allegany. Amer. Potato J. 71:507-516.
  • VALKONEN, J. P. T., SLACK, S. A., PLAISTED, R. L., AND WATANABE, K. N. 1994. Extreme resistance is epistatic to hypersensitive resistance to potato virus Yo in a Solanum tuberosum subsp. andigena-derived potato genotype. Plant Disease 78:11
  • WESTRA, A. A. G., AND SLACK, S. A. 1994. Effect of interaction of inoculum dose, cultivar, and geographic location on the magnitude of bacterial ring rot symptom expression in potato. Phytopathology 84:228-235.
  • WESTRA, A. A. G., ARNESON, C. P., AND SLACK, S. A. 1994. Effect of interaction of inoculum dose, cultivar, and geographic location on the development of foliar symptoms of bacterial ring rot of potato.
  • WESTRA, A. A. G., SLACK, S. A., AND DRENNAN, J. L. 1994. Comparison of some diagnostic assays for bacterial ring rot of potato. A case study. Amer. Potato J. 71:557-565.


Progress 01/01/93 to 12/30/93

Outputs
Bacterial ring rot studies concentrated on detection of the bacterium Clavibacter michiganensis subsp. sepedonicus, factors affecting symptom development and evaluation of relative cultivar susceptibility. Evaluation of RNA vs. DNA probes led to a standard DNA probe protocol used to evaluate test specificity and sensitivity on field-grown plants. Acetone was shown to be an effective aphid anesthetic for studies on aphidborne viruses. New cultivar releases included Genesee, golden nematode resistant for fresh market, and Russet Bake-King, uniform russeted sport of Bake-King for fresh market. Seed production of minitubers of new cultivars was shown to be enhanced by encapsulation in peat-lite mix, increasing yields an average of 44%. Results indicated that encapsulation of small minitubers was effective in expanding nuclear seedstock production. An overview of seed certification and seed improvement programs provides a comprehensive perspective of these studies in relation to the seed potato industry.

Impacts
(N/A)

Publications


    Progress 01/01/92 to 12/30/92

    Outputs
    Heat and chemical therapy yielded 74% and 91% virus-free (VF) plants after propagation as nodal cuttings and meristem-tips, respectively. System efficiency wasenhanced by propagating plantlets which tested less than 0.05 OD by ELISA with 92%, 93%, 71%, and 100% VF from viruses S, X, Y and leafroll (PLRV), respectively. Therapy cycling, developed to eliminate recalcitrant viruses, reduced titers 17-90%, and produced 95% 'Purple Fingers' and 64% 'All Red' plantlets VF with 100% and 69% freedom from PLRV, respectively. PLRV resistance, evaluated with uniform inoculum pressure in field tests, yielded disease incidence from 0-93% in genotypes. Significant groups were (most susceptible to most resistant): Russet Burbank, Sebago, B 9922-11 > Katahdin, Red Pontiac, F 100-1, Irish Cobbler, Norland > Abnaki, BelRus. Agreement between visual assessment and ELISA on plants from harvested tubers was about 90%. Inoculation with Clavibacter michiganensis subsp. sepedonicus influenced plant growth by geographic location. Disease ranged from 1.5% (CO), (1986) to 90.0% (ME, 1988). Regions were grouped into three categories: Low (CO), Medium (ND, WI) and High (ME, OR, WA), indicating that environmental conditions influence symptom expression. Relative foliar and tuber symptom expression in cultivars generally remained constant (Russet Burbank > Norchip > Norland) irrespective of location.

    Impacts
    (N/A)

    Publications

    • AUDY, P., ZIMNOCH-GUZOWSKA, E., TUFFORD, L., SLACK, S. A., PALUKAITIS, P. F. and ZAITLIN, M. 1992. Study of Virus Resistance in Transgenic Potato Plants Expressing Replicase Gene Sequences of Potato Virus Y and Potato Leafroll Virus. Amer.
    • BISHOP, A. L., and SLACK, S. A. 1992. Effect of infection with Clavibacter michiganensis subsp. sepedonicus Davis et al. on water relations in potato. Potato Res. 35:59-63.
    • DRENNAN, J., WESTRA, A., DELSERONE, L., GUDMESTAD, N., OLESON, A., COLLMER, A., and SLACK, S. 1992. Detection of Clavibacter michiganensis subsp. sepedonicus in field samples via DNA/DNA hybridization. Phytopathology 82:1067.
    • GREENSPAN-GALLO, L., SLACK, S. A., and LORIA, R. 1992. Therapy cycling to eliminate high-titered, multiple virus infections from potatoes. Phytopathology 82:247.
    • MELCHING, J. B., JONES, E. D. and SLACK, S. A. 1992. Field production of nuclear seed stocks using in vitro plantlets. American Potato J. 69:596.


    Progress 01/01/91 to 12/30/91

    Outputs
    Heat and chemical therapy yielded 74% and 91% virus-free (VF) plants after propagation as nodal cuttings and meristem-tips, respectively. System efficiency wasenhanced by propagating plantlets which tested less than 0.05 OD by ELISA with 92%, 93%, 71%, and 100% VF from viruses S, X, Y and leafroll (PLRV), respectively. Therapy cycling, developed to eliminate recalcitrant viruses, reduced titers 17-90%, and produced 95% 'Purple Fingers' and 64% 'All Red' plantlets VF with 100% and 69% freedom from PLRV, respectively. PLRV resistance, evaluated with uniform inoculum pressure in field tests, yielded disease incidence from 0-93% in genotypes. Significant groups were (most susceptible to most resistant): Russet Burbank, Sebago, B 9922-11 > Katahdin, Red Pontiac, F 100-1, Irish Cobbler, Norland > Abnaki, BelRus. Agreement between visual assessment and ELISA on plants from harvested tubers was about 90%. Inoculation with Clavibacter michiganensis subsp. sepedonicus influenced plant growth by geographic location. Disease ranged from 1.5% (CO), (1986) to 90.0% (ME, 1988). Regions were grouped into three categories: Low (CO), Medium (ND, WI) and High (ME, OR, WA), indicating that environmental conditions influence symptom expression. Relative foliar and tuber symptom expression in cultivars generally remained constant (Russet Burbank > Norchip > Norland) irrespective of location.

    Impacts
    (N/A)

    Publications


      Progress 01/01/90 to 12/30/90

      Outputs
      The effectiveness of obtaining virus-free (VF) potato plants by heat therapy (35C) and/or antiviral treatment with ribavirin (20 mg/l) was evaluated on 34 in vitro wild potato genotypes infected with single or multiple viruses. Significant reductions in virus concentration in treated plantlets were detected by ELISA in 96%, 60%,60%, & 54% of genotypes infected with viruses, S, X,Y and leaf roll, respectively. After treatment, meristem-tips (MT) & nodal cuttings (NC) were excised with 43% & 91% regenerating into plantlets, respectively. Treatments did not affect plantlet regeneration. The most effective treatment was heat + ribavirin followed by MT excision which yielded 70% & 47% VF plantlets for single & multiple infections, respectively; NC excision yielded 22% & 14% VF plantlets for single & multiple infections, respectively. In comparison, other treatments for all varieties tested generated 7% to 42% VF plantlets. Data indicated that differences in genotype:virus interactions existed & that monitoring virus concentration following plantlet treatment & following propagation by MT or NC was essential to identify VF plantlets. The first field season to evaluate cvs. for leafroll resistance was completed (10 cvs. x 4 reps x 2 trts.) Harvested tubers have been dormancy-treated & greenhouse planted. Three cvs. were inoculated with 10 o,10 2, 10 6, & 10 9 cfu/seed piece (3 reps x 4 trts) in a field to evaluate bacterial ring rot cultivar-pathogen & cultivar-pathogen-environ. interactions.

      Impacts
      (N/A)

      Publications

      • GRIFFITHS, H. M., and SLACK, S. A. 1990. Elimination of sweet potato feathery mottle virus from sweet potatoes using in vitro culture or propagation of apical buds under greenhouse conditions. Phytopathology 80:1061.
      • SANCHEZ, G. E., SLACK, S. A. and DODDS, J. H. 1990. Response of Solanum tuberosum subsp. andigena and selected potato species to in vitro antiviral therapy. Amer. Potato J. 67:575.
      • SLACK, S. A., GRIFFITHS, H. M., SANCHEZ, G. E., TUFFORD, L. A., EL-KEWEY, S. A.,AND DODDS, J. H. 1990. Virus elimination in in vitro potato plantlets by combining chemical & heat therapies. EAPR 11th Triennial Conf.pp.343-344.
      • DODDS, J. H., LIZARRAGA, R.,GRIFFITHS, H., and SLACK. S. A. 1990. Methods of virus eradication. III. CIP Planning Conference on the Control of Virus and Virus-like Diseases of Potato and Sweet Potato. Nov. 20-22, 1989.
      • GRIFFITHS, H.M., SLACK, S. A., and DODDS, J. H. 1990. Effect of chemical and heat therapy on virus concentrations in in vitro potato plantlets. Canadian Journal of Botany 68:1515-1521.
      • SANCHEZ, G. 1990. Response of Solanum tuberosum subsp. andigena and selected species to virus eradication therapy. Ms. Thesis, Cornell University. 90 pp.
      • SANCHEZ, G. E., SLACK, S. A., and DODDS, J. H. 1990. Response of selected Solanum species to virus eradication therapy. Amer. Potato J. 67:(accepted for pub.).