Résumé
Yellow leaf syndrome of sugarcane caused by the Sugarcane yellow leaf virus (SCYLV) was first reported in Hawaii and in Brazil in the late 1980s and early 1990s. The pathogen was subsequently found to be widespread in most sugarcane producing countries. SCYLV was first detected in Reunion in 1997, but sugarcane leaf yellowing had been observed on the island since 1980. The genetic variability of SCYLV was analysed using 48 virus isolates from Reunion Island and 24 isolates from other countries. One fragment from each of the six ORFs in the genome was amplified by RT-PCR, cloned and then sequenced. Phylogenetic analysis of the obtained sequences showed that the most variable regions of SCYLV are in ORF 1 which codes for a multifunctional protein and ORF 2 which codes for the replicase. On the other hand, the region the most conserved is ORF 3 which codes for the capsid protein. Depending on the region observed, the virus isolates were classified into two to four phylogenetic groups. Based on the variability of the entire genome, the majority of isolates from Reunion Island were different from the isolates of other origins. Four isolates from Reunion Island were, however, very close to these foreign isolates. This suggests that SCYLV was introduced to Reunion Island from another country and that one particular genotype evolved and spread on the island. (Texte intégral)