THE GENETIC diversity of Sugarcane yellow leaf virus (SCYLV) was investigated in a sugarcane selection plot in Guadeloupe to determine the incidence of the different known virus genotypes (BRA-PER, CUB and REU) in a breeding progeny. Four F1 leaves were randomly collected from each of 154 sugarcane clones and tested for the presence of SCYLV by tissue blot immunoassay (TBIA). The leaf samples were stored at ¿80°C until total RNA was extracted from SCYLV-infected leaves. The virus genotypes were determined by RT-PCR and primer pairs specific to each virus genotype. Eighty-two percent of the tested leaves were infected by SCYLV and all known virus genotypes occurred in the selection plot. The majority of plants were infected by genotypes CUB or REU, or by a mixture of these two genotypes. This situation was completely different from the situation observed in commercial fields in Guadeloupe where the incidence of SCYLV is much lower and where most plants are infected by genotype REU. The significance of this striking situation will be further investigated.