Spread of cymbidium mosaic potexvirus and potyvirusesin vanilla plants grown in shade houses in Reunion Island

Abstract

Introduction. Beginning in 1994, vanilla vines grown under shade houses in Reunion Island have developed disorders mainly due to the cymbidium mosaic potexvirus (CymV) and potyviruses. To reduce damage and avoid viral epidemics, we considered developing a vanilla nursery to supply farmers with virus-free plant material and to provide prophylactic advice. Accordingly, we determined the relationship between symptoms on vanilla leaves and viral diagnosis. We also determined the temporal and spatial distribution patterns of viral diseases. Materials and methods. Symptom assessment and serological tests were carried out on vanilla leaves (Vanilla fragrans) at various times. The relationship between symptoms and viral infection data was analyzed with Statistica software. Spatial distribution patterns of infected plants were generated with two-dimensional distance class analysis (2DClass). Results and discussion. Results showed that symptoms do not correlate well with serological diagnosis. Plants in all shade houses in the survey were infected mainly by CymV which spreads in the row according to cultural practices. Potyviruses could be transmitted both by insect vectors and mechanically, but for the latter case less efficiently than CymV. Conclusion. Results from this study can be used to develop control measures, including the production of healthy planting materials to manage plant disease epidemics. Further studies will involve the characterization of vanilla potyviruses so that reliable serological techniques and better molecular tools can be developed.