Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2009
Publication Date: 2/10/2010
Citation: Ling, K. 2010. Effectiveness of chemo- and thermo-therapeutic treatments on Pepino mosaic virus in tomato seed. Plant Disease. 94:325-328.
Interpretive Summary: Pepino mosaic virus (PepMV) is an emerging disease for greenhouse tomato. It poses a great threat to the $400 million greenhouse tomato industry in the United States. PepMV is seed-borne but not seed-transmitted virus, and the ease of mechanical transmission of PepMV from tomato seeds to seedlings makes the commercial tomato seed a potential source of initial virus inoculum. Previously, we determined that PepMV is localized on the tomato seed coats, but not in the embryos. This surface-locating nature of PepMV on tomato seed makes it possible to deactivate the virus infectivity through seed treatment. In this study, we evaluated the effectiveness of several chemo- and thermo-therapeutic methods against a heavily PepMV-contaminated commercial tomato seed lot. Even though chemotherapy with trisodium phosphate (TSP) or sodium hypochlorite (Clorox) greatly reduced the PepMV titer, dry-heat at 80C for 72 hours was most efficacious with total deactivation of virus infectivity and no adverse effect on seed germination. It is therefore recommended to consider using a combination of chemo (Clorox or TSP) and thermotherapy (dry heat) to achieve the complete effect of seed treatment for PepMV in tomato seed.
Technical Abstract: Pepino mosaic virus (PepMV) is a seed-borne virus of importance in greenhouse tomatoes. The ease of mechanical transmission of PepMV from contaminated tomato seeds to seedlings makes commercial tomato seed a potential source of initial virus inoculum. The objective of this study was to evaluate the effectiveness of chemo- and thermo-therapeutic treatments on PepMV using seeds from a commercial hybrid tomato seed lot. The effect of various seed treatments was evaluated through bioassay with mechanical inoculation of the treated seed extract on indicator plants (Nicotiana benthamiana). Three commonly used seed treatment chemicals and two thermo-treatment methods were evaluated. The most effective chemical was the Clorox solution (0.5% and 1.0% sodium hypochlorite), followed by trisodium phosphate. On the other hand, hydrochloric acid treatments were not effective. Under the stated chemotherapeutic treatment conditions, the rate of seed germination was not significantly affected. With thermotherapeutic treatments, although hot water soaking for 2 h at 55oC deactivated virus infectivity, it also resulted in a detrimental effect on seed germination. However, treatment with dry-heat baking (72oC or 80oC for 48-72 h) was effective in reducing PepMV infection, resulting in minimum impact on seed germination.