Purpose: To compare the survival of FCV, MNV, SaV and TV on lettuce leaves post-harvesting.
Methods: Viruses were propagated in cell culture and harvested in the media (untreated). To accurately compare these viruses, we removed the cell culture media by ultrafiltration using Amicon® centrifugal filter devices (100K) followed by re-suspension in original volume with sterile water. The survival of untreated as well as ultrafiltered viruses was compared: (i) in suspension at room temperature (RT) for 28 days; and (ii) following spot inoculation onto lettuce leaves at RT (for 3 days) and 4°C (for 14 days). Virus infectivity titers were determined by end-point dilution.
Results: At RT, untreated FCV, SaV and TV lost infectivity by days 7, 14 and 21; respectively, while MNV remained infectious through day 28. In contrast, ultrafiltered viruses remained infectious through at least day 28 with 0.05, 1.2, 1.9 and 2.03 log reduction in infectious titers for MNV, TV, FCV and SaV, respectively. When the untreated viruses were inoculated onto lettuce leaves for 3 days at RT, MNV was significantly more stable than SaV and FCV (1.1 versus 2.5 and 2.7 log reduction in infectious titer, respectively). In contrast, ultrafiltered viruses showed no significant difference in survival by day 3. Inoculation of leaves with the untreated viruses at 4°C for 14 days showed that MNV was significantly more stable than SaV and FCV; however, ultrafiltered MNV showed similar survival to SaV and FCV.
Significance: Our results suggest that after reconstitution in water, all surrogate viruses survived similarly on lettuce leaves.