Arch Virol (1992) [Suppl5]: 221-222 © by Springer-Verlag 1992
Potyvirus taxonomy: potyviruses that affect solanaceous crops E.N. Fernandez-Northcote International Potato Center (CIP), Lima, Peru
Summary: Serology has been the main, or at least an important, tool for differentiating potyviruses that affect solanaceous crops. At present, analysis of the genome by hybridization techniques has supported the differentiation of viruses demostrated by serology. Phylogenetic groupings, based on nucleic acid sequences, should be combined with serological detection to make the groupings more usable.
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The taxonomy of potyviruses should serve pathologists' needs. It should consider phylogenetic relationships determined on the basis of characters that can be detected reliably by simple techniques usable in unsophisticated laboratories. For potyviruses which infect such solanaceous crops as potato, tomato, pepper, and tobacco, drop-microprecipitin tests with purified virus have shown that isolates with serological differentiation index (SDI) units equal to or greater than five are, for all practical purposes, different viruses [2,4]. This criterion correlates well with results in sodium dodecyl sulfate-agar immunodiffusion [5] using antigen in crude sap where formation of a weak spur indicates an SDI equal to or greater than five. These results also correlate well with a more recent technique like the standard direct, double antibody sandwich ELISA (DAS-ELISA) using proper polyclonal antibodies and crude sap. Isolates which, on the basis of drop-microprecipitin or SDS-agar double diffusion are considered to be different viruses, do not react in DAS-ELISA with polyclonal antibodies in the heterologous combination. Modified indirect ELISA on nitrocellulose membranes (NCM-ELISA) with crude sap, is less specific than DAS-ELISA; here different potyviruses are distinguished by SDI as in microprecipitin tests. When monoclonal antibodies (MAs) are used, some common epitopes are found among potyviruses with weak serological relationships with poly clonal antisera (different viruses but related), but a majority of MAs detect epitopes which are distinct for different viruses [3]. Serology has been the main, or at least an important, tool for differentiating potyviruses because serological characteristics of viruses are relatively stable.
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E. N. Fernandez-Northcote: Potyviruses that affect solanaceous crops
This technique has been called into question prompting studies to analyze differences in the rest of the virus genome (about 10% of the genome codes for the coat protein) [1,6,7]. At present, analysis of the genome by hybridization techniques has supported the differentiation of viruses demonstrated by serology [8]. Even if differences are found in 90% of the noncoat-protein portion of the genome, these would be of secondary importance since the coat protein plays a critical role in the processes of vector-transmission and infection. Transmission and infection may determine an evolutionary process of the virus related to host specialization. This is, in the end, what is of interest to the pathologist. Serological differences among isolates of a virus can be used for differentiating serotypes. These differences are important for appropriate virus detection. The aphid-transmitted viruses of the old potyvirus group are considered a "genus" and each of the viruses a "species". Pathogenic differences within a virus allow for grouping isolates (here differences in vector relationships could also be considered) into strains. Virulence to specific genes for resistance within hosts can be used to differentiate pathotypes. Nucleic acid technology can give a phylogenetic arrangement based on sequence homology within and between potyvirus species. These phylogenetic groupings, based on nucleie acid sequences, should be combined with serological detection to make the groupings more usable [l, 7] because serological tests are easily used in most field laboratories.
References 1. Baulcombe DC, Fernandez-Northcote EN (1988) Detection of strains of potato virus X and of a broad spectrum of potato virus Y isolates by nucleic acid spot hybridization (NASH). Plant Dis 72: 307-309 2. Fernandez-Northcote EN (1978) Detection and characterization of Peruvian tomato virus strains affecting pepper and tomato in Peru. PhD Thesis. University of Wisconsin, Madison, Wisconsin, USA 3. Fernandez-Northcote EN (1987) Reaction of a broad spectrum of potato virus Y isolates to monoclonal antibodies in ELISA. Fitopatologia 22: 33-36 4. Fernandez-Northcote EN, Fulton RW (1980) Detection and characterization of Peru tomato virus strains affecting pepper and tomato in Peru. Phytopathology 70: 315-320 5. Purcifull DE, Batchellor DL (1977) Immunodiffusion tests with sodium dodecyl sulfate (SDS)-treated plant viruses and plant viral inclusions. Fla Agric Exp Stat Bull 788 6. Robaglia C, Durand-Tardif M, Tronchet M, Boudazin G, Astier-Manifacier S, Casse-Delbert F (1989) Nucleotide sequence of potato virus Y (N strain) genomic RNA. J Gen Virol 70: 935-947 7. Shukla DD, Ward CW (1988) Amino acid sequence homology of coat proteins as a basis for identification and classification of the potyvirus group. J Gen Viro169: 2703-2710 8. van der Vlugt R, Allefs S, de Haan P, Goldbach R (1989) Nucleotide sequence of the 3 '-terminal region of potato virus yN RNA. J Gen Virol 70: 299-233 Author's address: E. N. Fernandez-Northcote, International Potato Center (CIP), Apartado 5969, Lima, Peru.
Potyvirus taxonomy: potyviruses that affect solanaceous crops E.N. Fernandez-Northcote International Potato Center (CIP), Lima, Peru
Summary: Serology has been the main, or at least an important, tool for differentiating potyviruses that affect solanaceous crops. At present, analysis of the genome by hybridization techniques has supported the differentiation of viruses demostrated by serology. Phylogenetic groupings, based on nucleic acid sequences, should be combined with serological detection to make the groupings more usable.
*
The taxonomy of potyviruses should serve pathologists' needs. It should consider phylogenetic relationships determined on the basis of characters that can be detected reliably by simple techniques usable in unsophisticated laboratories. For potyviruses which infect such solanaceous crops as potato, tomato, pepper, and tobacco, drop-microprecipitin tests with purified virus have shown that isolates with serological differentiation index (SDI) units equal to or greater than five are, for all practical purposes, different viruses [2,4]. This criterion correlates well with results in sodium dodecyl sulfate-agar immunodiffusion [5] using antigen in crude sap where formation of a weak spur indicates an SDI equal to or greater than five. These results also correlate well with a more recent technique like the standard direct, double antibody sandwich ELISA (DAS-ELISA) using proper polyclonal antibodies and crude sap. Isolates which, on the basis of drop-microprecipitin or SDS-agar double diffusion are considered to be different viruses, do not react in DAS-ELISA with polyclonal antibodies in the heterologous combination. Modified indirect ELISA on nitrocellulose membranes (NCM-ELISA) with crude sap, is less specific than DAS-ELISA; here different potyviruses are distinguished by SDI as in microprecipitin tests. When monoclonal antibodies (MAs) are used, some common epitopes are found among potyviruses with weak serological relationships with poly clonal antisera (different viruses but related), but a majority of MAs detect epitopes which are distinct for different viruses [3]. Serology has been the main, or at least an important, tool for differentiating potyviruses because serological characteristics of viruses are relatively stable.
222
E. N. Fernandez-Northcote: Potyviruses that affect solanaceous crops
This technique has been called into question prompting studies to analyze differences in the rest of the virus genome (about 10% of the genome codes for the coat protein) [1,6,7]. At present, analysis of the genome by hybridization techniques has supported the differentiation of viruses demonstrated by serology [8]. Even if differences are found in 90% of the noncoat-protein portion of the genome, these would be of secondary importance since the coat protein plays a critical role in the processes of vector-transmission and infection. Transmission and infection may determine an evolutionary process of the virus related to host specialization. This is, in the end, what is of interest to the pathologist. Serological differences among isolates of a virus can be used for differentiating serotypes. These differences are important for appropriate virus detection. The aphid-transmitted viruses of the old potyvirus group are considered a "genus" and each of the viruses a "species". Pathogenic differences within a virus allow for grouping isolates (here differences in vector relationships could also be considered) into strains. Virulence to specific genes for resistance within hosts can be used to differentiate pathotypes. Nucleic acid technology can give a phylogenetic arrangement based on sequence homology within and between potyvirus species. These phylogenetic groupings, based on nucleie acid sequences, should be combined with serological detection to make the groupings more usable [l, 7] because serological tests are easily used in most field laboratories.
References 1. Baulcombe DC, Fernandez-Northcote EN (1988) Detection of strains of potato virus X and of a broad spectrum of potato virus Y isolates by nucleic acid spot hybridization (NASH). Plant Dis 72: 307-309 2. Fernandez-Northcote EN (1978) Detection and characterization of Peruvian tomato virus strains affecting pepper and tomato in Peru. PhD Thesis. University of Wisconsin, Madison, Wisconsin, USA 3. Fernandez-Northcote EN (1987) Reaction of a broad spectrum of potato virus Y isolates to monoclonal antibodies in ELISA. Fitopatologia 22: 33-36 4. Fernandez-Northcote EN, Fulton RW (1980) Detection and characterization of Peru tomato virus strains affecting pepper and tomato in Peru. Phytopathology 70: 315-320 5. Purcifull DE, Batchellor DL (1977) Immunodiffusion tests with sodium dodecyl sulfate (SDS)-treated plant viruses and plant viral inclusions. Fla Agric Exp Stat Bull 788 6. Robaglia C, Durand-Tardif M, Tronchet M, Boudazin G, Astier-Manifacier S, Casse-Delbert F (1989) Nucleotide sequence of potato virus Y (N strain) genomic RNA. J Gen Virol 70: 935-947 7. Shukla DD, Ward CW (1988) Amino acid sequence homology of coat proteins as a basis for identification and classification of the potyvirus group. J Gen Viro169: 2703-2710 8. van der Vlugt R, Allefs S, de Haan P, Goldbach R (1989) Nucleotide sequence of the 3 '-terminal region of potato virus yN RNA. J Gen Virol 70: 299-233 Author's address: E. N. Fernandez-Northcote, International Potato Center (CIP), Apartado 5969, Lima, Peru.
