Effect of Storage Temperatures on Potato Virus Infectivity Levels and Serological Detection by Enzyme-Linked Immunosorbent Assay

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Abstract
Leaves infected with potato leafroll virus or potato virus [PV] A, S, X, or Y stored at 25.degree., 4.degree., -20.degree. or -70.degree. C produced variable infectivity and serological readings. Freezing at -20.degree. C lowered the A405 values in ELISA [enzyme linked immunosorbent assay] for all potato viruses tested except PVX. Infectivity levels of PVA and PVY were also lowered at -20.degree. C. Refrigeration of leaves at 4.degree. C or freezing at -70.degree. C preserved the infectivity and serological activity up to 12 days. The lower A405 values at -20.degree. C were not due to dilution effect, were not affected by host species, and were similar for stored leaves and expressed sap. Purification of PVY from leaves stored at 4.degree., -20.degree. and -70.degree. C produced the lowest yield of virus at -20.degree. C and the highest at -70.degree. C. Pretreatment of leaves in solutions of 5% yeast extract, 5% bactotryptone, 5% bactopeptone, 10% sucrose or 10% glycine followed by storage at -20.degree. C partially retained both infectivity and serological activity.