Biological and serological variability, evolution and molecular epidemiology of Zucchini yellow mosaic virus (ZYMV, Potyvirus) with special reference to Caribbean islands

Zucchini yellow mosaic virus (ZYMV, Potyvirus) emerged as an important pathogen of cucurbits within the last 20 years. Its origins and mechanisms for evolution and worldwide spread represent important questions to understand plant virus emergence. Sequence analysis on a 250 nucleotide fragment including the N-terminal part of the coat protein coding region, revealed one major group of strains, and some highly divergent isolates from distinct origins. Within the major group, three subsets of strains were defined without correlation with geographic origin, year of collection or biological properties. ZYMV was first observed in Martinique and Guadeloupe in 1992 and 1994, respectively. We studied the evolution of ZYMV variability on both islands in the few years following the putative virus introduction. In Martinique, molecular divergence remained low even after 6 years, suggesting a lack of new introductions. Interactions between strains resulted in a stability of the high biological variability, while the serological diversity decreased and molecular divergence remained low. In Guadeloupe, as in Martinique in 1993, serological variability was high shortly after virus introduction. While the first introduction in Guadeloupe was independent from Martinique, the ‘Martinique’ type was detected in 1998, suggesting further introductions, maybe through viruliferous aphids or imported plant material.