Some effects of other viruses and of temperature on the multiplication of potato virus X

Abstract

SUMMARY The severity of symptoms shown by tobacco plants infected with potato virus X (PVX) was correlated with virus concentration. The virus multiplied optimally between 20 and 24deg;C. and increasing temperature above 25°C. decreased symptoms and virus concentration. PVX did not multiply detectably in plants at 34°C. Tobacco leaves systemically infected with both PVX and potato virus Y (PVY) contained more PVX than leaves infected with PVX alone. The greatest relative increase was at 31°C. because at this temperature PVX alone barely multiplied and failed to move out of the inoculated leaf. The concentration of PW was not altered by the presence of PVX and the optimum temperature for its multiplication appeared to be 28°C. Three other viruses (namely tobacco mosaic virus, cucumber mosaic virus (yellow strain), and henbane mosaic virus) that multiply at 31°C. also assisted the systemic spread of PVX at this temperature, possibly by aiding its movement between mesophyll cells and into the phloem. PVY may also aid PVX at lower temperatures mainly by increasing the number of cells it infects.