Résumé
Maize yellow stripe virus (MYSV), found on maize, sorghum and wheat plants in Egypt, causing serious losses in late sown maize, has several features in common with tenuiviruses, but is transmitted by a cicadellid leafhopper rather than delphacid planthoppers. Since tenuiviruses are known to multiply in their vectors, multiplication of MYSV in its vector Cicadulina chinai, following an acquisition access period (AAP) of 1-3 days on infected plants, was studied by two basically different methodologies. Using dot blot hybridisation analysis, that detects viral RNA, MYSV was not detected in leafhoppers one day following a 2-day AAP, but was detected in single or groups of leafhoppers 5-20 days post-acquisition. Additionally, using DAC-ELISA assays of capsid protein in single leafhoppers that had a Ior 3-day AAP, MYSV titer, as indicated by ELISA absorbence values, increased gradually and significantly in vector leafhoppers reaching its highest levels 8-14 days post-acquisition. Transovarial transmission of MYSV was not detected in 600 C. chinai nymphs that hatched from eggs laid by MYSV infective mothers. The above results indicate that, like tenuiviruses, MYSV is propagative in its vector; but unlike most tenuiviruses, MYSV apparently is not efficiently transmitted transovarially through the vector. Based on various differences and similarities between MYSV and tenuiviruses, we suggest that MYSV is the type member of a new genus "Cicatenuivirus" (transmitted by Cicadellidae), within a family "Tenuiviridae" that includes the present Delphacid transmitted tenuiviruses in another genus. (Texte intégral)