There is an excellent article in the journal Plant Disease, May 2012, Vol 96 no 5 by Valverde, Sabanadzovic and Hammond that has tons of examples of variegation caused by viruses that were introduced on purpose to make plants patterned and variegated. Most of them are plants that Myself don;t grow. Tulips, Cannas (Bengal Tiger and Pretoria are both examples of variegation caused by virus), some of the ornamental maples, just a ton of different plants.
The Dasheen Mosaic Virus that I referred to above is a virus spread via aphids and it is almost universally present in all commercial aroid producing growing operations. It isn;t one that is encouraged, when nurseries find it they usually destroy the affected plants, because Taro (some forms of Elephant Ears) are a major food crop in some countries.
Yes, I have read that the plants intentionally infected with color break viruses can revert back. Sometimes the effect is transitory. I can;t speak to tomatoes....I haven;t grown them for probably 30 years!
The introduction of tissue culture radically decreased to incidence of viruses plants in some species.
