Potato viruses in Finland and their identification

Abstract

The occurrence of potato viruses in Finland and alternative methods for their identification are reported in this study. The following seven viruses were found to occur; potato viruses X, S, M, Y, A, potato leaf roll virus (PLRV) and tobacco rattle virus (TRV). The isolates of potato viruses X and Y included two clearly distinct strains. The other viruses had only minor variants. The most severe and important of the viruses was PVY, particularly its Y° strain. Other important viruses were PVM and PVA and potentially PLRV. PVY was found to be the most easily transmitted in the field. For serological identification of the viruses, indigenous antisera produced for selected isolates were mostly used. Significant serological variation was only found among the PVY isolates. The lowest concentration of PVX D-protein detected with the agar gel double diffusion test was 10 µg/ml and 1 µg/ml with the single diffusion test. With the ELISA test 0.1 ng of virus /ml could be detected. For PVX the lowest relative value detected in potato leaf sap was a dilution of between 10-6 and 10-7. The chloroplast agglutination test was too unreliable for detecting PVY in potato samples. Also the agar gel double diffusion test was found to be too insensitive for the identification of potato viruses but the single diffusion test could be used in certain cases. With the ELISA test potato viruses X, S, M and Y could be reliably detected in potato leaf sap and with almost the same accuracy in sap from sprouting tubers. The ELISA test was also found to give satisfactory results during routine testing for the identification of PVA and PLRV in potato leaves or non-dormant tubers.

Antigenic Characterization of Potato Virus X with Monoclonal Antibodies

“…The PVX samples included an uncharacterized field isolate of PVX from the Estonian potato cv. Ando and also two 'mild mosaic' and two ringspot strains of PVX in four Finnish potato cultivars (Kurppa, 1983).…”

“…Complete adjuvant was used in the first injection and incomplete in the following injections. Rabbits were immunized by a combination of intravenous and intramuscular injections and were bled at 1 week intervals after two to four injections (Kurppa, 1983). The immunoglobulin fraction was purified by precipitation with PEG 6000 (J/irvekiilg et al, 1987), essentially as described above for MAbs.…”

“…MAbs 21XB4, 21XD2 and 23XA5 recognized common strains ('mild mosaic' strains) and ringspot strains of Finnish PVX isolates (listed in the paper by Kurppa, 1983) and also all PVX isolates available in the U.S.S.R up to now. Therefore, MAbs 21XD2, 21XB4 and 23XA5 seem to be specific to epitopes common to several PVX isolates.…”

Time-resolved Fluoroimmunoassay in the Detection of Plant Viruses

“…For comparative tests to detect potato viruses X (PVX) and Y (PVY) with TR-FIA and ELISA, sap from healthy and infected tuber and leaf samples was serially diluted in 10-fold steps, 10 to 106, in sample buffers. The PVY samples included the isolates YSF10 (PVY°), YSFI 1 (PVY") (Kurppa, 1983), and an uncharacterized field isolate of the PVY ~ strain, all in the potato cv. Record.…”

“…Control samples for PVX also included potato viruses M, S and Y. A Protein-A Sepharose-purified fraction of rabbit immunoglobulins (IgG PVX, Kurppa, 1983;IgG PVY, Kurppa & Korhonen, 1984) was used at 1 l.tg/ml for coating the plates and for preparing the conjugates.…”