Serial Transmission of Plant Viruses by Cutting Implements during Grafting

Abstract

Reciprocal grafts of two tomato (Solanum lycopersicum L.) cultivars were made by hand using commercial grafting techniques. The razor blade used to cut the rootstock or scion was first contaminated by making a single cut on tomato plants infected with either Tomato spotted wilt virus (TSWV) or Tomato mosaic virus (ToMV). Although no transmission of TSWV was observed in these experiments, ToMV was spread plant to plant through razor blade exposure to this virus. The presence of this virus was confirmed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) at 21 days post-inoculation. The highest rate of infection was 25% of the inoculated plants. The greatest number of positive virus assays was found in the first 10 plants of each experiment. These areas contained 84% of the DAS-ELISA-positive plants. Gaps of up to 10 plants occurred during serial inoculation before infection resumed. Random dispersion occurred in two experiments. Similar results were observed whether the contaminated implement was used to cut the rootstock or the scion before graft assembly. This work demonstrates that some viruses from a single contamination can be moved in a serial manner during the grafting process, especially with varieties with minimal or no resistance to viral plant pathogens. Also, visual diagnosis cannot always be relied on as a means of eliminating virus-infected plants, especially when higher greenhouse and annealing temperatures are maintained.