In the autumn of 2022, researchers in Greece studied a type of tomato called Ekstasis, which was grown in Aspropyrgos, Attiki, Greece. These tomatoes were infected with Tomato brown rugose fruit virus. The researchers used a method called RNA-Seq to analyze the tomato samples. They isolated RNA (a type of genetic material) from the leaves of the tomatoes and used a special kit and a machine called Illumina Novaseq 6000 for this analysis. When they examined the genetic material of these tomatoes, they found not only ToBRFV but also two other viruses: Southern tomato virus (a type of virus known as Amalgavirus) and Tomato fruit blotch virus (ToFBV).
Tomato fruit blotch virus is a newly identified virus that causes uneven and blotchy ripening along with dimpling and dark spots on tomato fruits. From its first identification in 2018-2019 in Italy and Australia, it was newly reported in Spain, Brazil, Slovenia, and Tunisia and retrieved from stored samples, dating back its presence in Italy to 2012, Belgium researchers shared earlier on.
ToFBV has been reported in other countries like Italy, Australia, Brazil, Spain, Portugal, Slovenia, and Tunisia and is linked to a disease in tomatoes. However, it's important to note that they hadn't proven that ToFBV was causing the disease in these tomatoes, and they also hadn't confirmed if it could be spread mechanically or through seeds.
ToFBV belongs to a group called Blunervirus, and its genetic material is made up of four single-stranded, positive-sense RNAs. When they compared the genetic material of the Greek ToFBV with isolates from other places, they found that it had a high level of similarity to the Tunisian and Italian isolates.
To confirm the presence of ToFBV, the researchers used a technique called RT-PCR to amplify a specific part of its genetic material. This helped them verify that ToFBV was indeed present in the tomato samples.
Additionally, they tested 11 tomato fruit samples from a greenhouse in Crete and one from a field in Evia, Greece, which also showed fruit blotch symptoms. When they tried to infect other plants with sap from these tomatoes (a way to check if the virus is mechanically transmitted), no symptoms appeared. This suggested that ToFBV was not mechanically transmitted.
They also checked for the presence of other viruses in these samples but found that only ToFBV was present. Interestingly, all the plants were infested with tomato russet mites, which are suspected to be a possible way the virus is spread.
This study marks the first time ToFBV was identified as infecting tomatoes in Greece, and it's a concern for tomato cultivation due to its potential association with fruit blotch disease and possible mite transmission.
This work was funded by the General Secretariat for Research and Innovation through the National Recovery and Resilience Plan "Greece 2.0" (action code TAEDR-0535675).