DETECTION, SPREAD, AND INTERACTIONS OF PEPINO MOSAIC VIRUS AND PYTHIUM APHANIDERMATUM IN THE ROOT ENVIRONMENT OF TOMATO IN HYDROPONICS

Pepino mosaic virus (PepMV) is a well-known and widely distributed plant virus affecting tomato production. PepMV is highly contagious and can be efficiently transmitted by nutrient solution in a closed recirculating system within six weeks, although it was not detectable directly in nutrient solution using ELISA or Immunocapture RT-PCR. Roots tested positive for PepMV one to three weeks after inoculation. Subsequently a rapid spread from the roots into the young leaves and developing fruits was seen within one week. The effect of pre-infection with the common root pathogen of tomato, Pythium aphanidermatum, on spread of PepMV in tomato plants was studied. Pre-infection of tomato cv. Hildares roots delayed infection with PepMV significantly. When mechanically inoculated with PepMV at the 2-4 leaf stage, losses in total yield were observed in all plants. However, yield losses for plants invaded through the nutrient solution with PepMV were observed for cv. Castle Rock only. Losses in total yield infected by PepMV and/or P. aphanidermatum amounted from 0.4% up to 40% depending on experimental conditions, such as climate, cultivar, and growing period. A significant reduction of blossom-end rot on fruits was observed upon P. aphanidermatum- and PepMV-infected plants.