Identification of natural weed hosts of Tomato chlorosis virus in Korea by RT-PCR with root tissues

Tomato chlorosis virus (ToCV) is a whitefly-transmitted crinivirus that causes interveinal chlorosis and bronzing on tomato leaves. Although outbreaks of ToCV have been reported in many countries, the virus was not reported in Korea until 2013. To identify weed hosts of ToCV that may serve as virus reservoirs, we analyzed various weeds that were growing together with ToCV-infected tomatoes and viruliferous Bemisia tabaci in a tomato greenhouse. We performed reverse transcription-polymerase chain reaction (RT-PCR) analysis of root samples from 148 samples of 61 species from 24 families of plants grown in the greenhouse to avoid possible ToCV contamination by whiteflies on leaves. Seventeen weed species were identified as ToCV hosts based on RT-PCR results of root samples: Conyza canadensis, Erigeron annuus, Sonchus asper, Youngia japonica, Trigonotis peduncularis, Cardamine flexuosa, Cerastium glomeratum, Stellaria media, Chenopodium album, Ipomoea hederacea, Quamoclit coccinea, Vicia angustifolia var. segetilis, V. tetrasperma, Phytolacca americana, Mazus pumilus, Solanum americanum and S. nigrum. The amplicons obtained by RT-PCR were confirmed as ToCV by sequence analysis. Life cycle analysis of the weeds indicated that each weed could play an important role as a “green bridge” or virus reservoir between tomato cultivation seasons. This is the first report documenting the possible occurrence of ToCV in tomato plants based on weed life cycles.