Résumé
To date, sugarcane streak mosaic virus (SCSMV) has not been successfully transmitted experimentally from plant to plant using insects, including aphids. Consequently, the insect vector of SCSMV remains unknown. SCSMV belongs to the genus Poacevirus of the family Potyviridae. This genus currently includes four virus species: Sugarcane streak mosaic virus, Triticum mosaic virus, Caladenia virus A, and Zoysia mosaic virus. Triticum mosaic virus is transmitted by the wheat curl mite (WCM) Aceria tosichella, an eriophyid mite that failed to transmit SCSMV. This mite is also the vector of wheat streak mosaic virus (WSMV), a tritimovirus of the family Potyviridae. WSMV has a zinc finger like (ZFL) motif [H(X2)C X29 C(X2)C] in the HC-Pro protein that is necessary for its transmission by the WCM. However, all viruses of the Potyviridae family that possess a HC-Pro protein have a ZFL motif in the HC-Pro, which is therefore not specific to mite transmission. Two other well studied motifs, namely KITC and PTK, are associated with aphid-transmission of potyviruses. Among 131 species of the Potyviridae family, the KITC [or a similar motif that is attached to the C(X2)C motif of the ZFL motif] and the PTK motifs are present in almost all aphid-transmitted potyviruses, but are missing in all non-aphid transmitted viruses. A phylogenetic tree was constructed with the HC-Pro sequences of the 131 Potyviridae species and was linked to protein motifs and virus vectors. SCSMV clustered with a group of viruses spread by Aceria mites, which suggested that at least one mite species is a vector of SCSMV. Most mite species found on sugarcane belong to the Eriophyidae family with at least 10 species belonging to six genera that are distributed in Africa, America, Asia, and Oceania. Eriophyid mites are able to spread most mite-transmitted viruses. Consequently, eriophyid mites are good candidates for vectoring SCSMV and should be identified and tested in geographical locations where this virus is present.