Plant virus causing variegation in camellia
In ornamental plants, variegation in flower and leaf is quite important trait. Virus infection is one of causes for variegation. In general, variegation by plant virus is not favored because plants become weaker. However in case of camellia, tree growth seems not so seriously affected. People prefer variegation because of its beauty thus those are very valuable. When white pattern appears in the red background of petals, usually leaves also variegated. This variegation is known to be transferable by grafting, so that it is considered to be caused by virus. But no causal virus has been isolated. Recently camellia chlorotic dwarf associated virus (CaCDaV) was discovered, but they did not mention for flower color variegation (Zhang et al., 2018). In this study we are aiming to isolate causal virus responsible for flower variegation. Variegated cultivars were used. Nicotiana benthamiana, which is known as a host plant for many different plant viruses, was used as a test plant for inoculation. First inoculation using crude extracts of variegated camellia leaves or petals by rubbing was performed to check the existence of virus. If mechanical inoculation could be done successfully, it was indicating involvement of virus. Disease symptoms such as discoloration or dwarf were appeared 10-30 days after inoculation into N. benthamiana leaves. Then second inoculation into another N. benthamiana individual was done with crude extract of firstly infected N. benthamiana leaf. Almost identical disease symptom appeared. By these experiments, we could confirm the existence of plant virus in variegated camellia. Double-strand RNA (dsRNA) was obtained from crude extract of infected N. benthamiana leaves by using DRB (Double-strand RNA Binding) protein. This result also suggests the involvement of plant virus, because virus forms dsRNA in the process of duplication. Further analysis of dsRNA sequencing is ongoing.
Terada, K., Katayama, H. and Uematsu, C. (2021). Plant virus causing variegation in camellia. Acta Hortic. 1331, 319-324
sap inoculation, RT-PCR, viral dsRNA, RNA-Seq, DECS