Résumé
Sugarcane streak mosaic virus (SCSMV) has not been successfully transmitted experimentally using insects such as aphids or leafhoppers, and the vector of this virus remains unknown. SCSMV belongs to the genus Poacevirus (family Potyviridae) that consists officially of three virus species, including sugarcane streak mosaic virus (Poacevirus sacchari) and triticum mosaic virus (Poacevirus tritici). The helper component protein (HC-Pro) of Potyviridae is critical for virus transmission. A zinc finger-like (ZFL) motif at the 5' end of the HC-Pro is involved in the binding of the potyvirus coat protein to the aphid vector and for triticum mosaic virus to the wheat curl mite (WCM) Aceria tosichella. A phylogenetic tree was constructed with the HC-Pro sequence of 129 Potyviridae species and was linked to virus vectors. Among these 129 species, the KITC [or a similar motif that is attached to the C(X2)C motif of the ZFL motif] and PTK motifs were present in almost all aphid-transmitted potyviruses but were missing in all non-aphid transmitted viruses. SCSMV clustered with a group of viruses spread by Aceria mites of the Eriophyidae family. Aceria mites hosted by sugarcane are currently not present in the USA, and SCSMV has not spread in Louisiana despite the virus being present for several years in imported sugarcane germplasm. Two species of Aceria mites have been found on sugarcane, Ac. mervei in South Africa and Ac. sacchari in several Asian countries and in Côte d'Ivoire, a country where streak mosaic emerged recently. The geographic distributions of SCSMV and Ac. sacchari are concomitant. Furthermore, transmission of a streak disease virus by Ac. sacchari from symptomatic to asymptomatic sugarcane was demonstrated in India in 1972. These findings provide evidence that Ac. sacchari is a vector of SCSMV. Inoculation experiments are in progress in Côte d'Ivoire to verify this hypothesis.