Squash mosaic virus (SqMV)

( Comovirus, Comoviridae )

SqMV is a comovirus transmitted by phytophagous beetles * , but also by seed and by contact . It is not a very common virus, even in parts of the world where its vectors are present, possibly due to the fairly effective control of vectors by insecticides. SqMV has only been reported in France very occasionally, always in connection with the use of contaminated seed lots . Some dissemination of the virus can then occur by mechanical transmission during pruning operations or by simple friction between neighboring plants, in the absence of a vector.

SqMV was described in California in 1956. It was then reported in many other parts of the USA, South America, Taiwan and the southern Mediterranean Basin (Israel, Morocco ) where beetles vectors of this viruses are present. It is occasionally reported in France, Spain or Italy.

The SqMV exhibits paraspheric particles 28 nm in diameter which often appear with a hexagonal outline under electron microscopy. The viral genome is divided, it consists of two single-stranded RNA molecules of positive polarity.

Many viruses cause mosaics in Cucurbits, which often makes visual diagnosis difficult. However, the symptoms of SqMV at the seedling stage are quite characteristic (vein-banding, leaf deformation) and allow rapid identification of the virus. On older plants, confusion is possible with WMV. Commercial diagnostic kits ELISA are available, as well as primers for molecular diagnosis by RT-PCR . Recently, rapid detection kits have been developed: they make it possible to detect the presence of SqMV in a few minutes in the field.

* A insect phytophagous is an insect that feeds on plants or leaves. Thus, there are species of ladybugs that eat aphids but other species feed exclusively on leaves and can transmit plant viruses.