J. Nourrisseau, M. Lansac, M. Garnier
A new decline of strawberry (Fragaria × ananassa) has been observed in France since 1988. It is observed in strawberry nurseries as well as in fruit production fields and on all cultivars. The same decline has also been observed in strawberry nurseries in Spain (J.G. Nourrisseau) since 1984. The main symptom is the presence of marginal chlorosis (2 mm wide) on the young leaves. No symptom of interveinal chlorosis are observed. Other typical symptoms are severe stunting of the plant and, in nurseries only, a red coloration of the leaves and root necrosis of young runners. In this case the production is stopped. In fruit production fields the plant produce flowers and fruits but the latter are small and deformed. At maturity they have a purple-red coloration, a very soft texture and a sour taste rendering the crop unmarketable. The cases of mortality are very few. The most severe symptoms are observed when the temperature is high and when the plants have a good growth. The number of affected plants can vary in each plot and is more important in southern than in northern France.

Electron microscopy observation revealed the presence of Bacteria Like Organism (B.L.O.) in the phloem of affected strawberry plants. Moreover DAPI staining carried out on the same samples resulted in fluorescent staining of DNA in the phloem. For these reasons, DAPL staining can be used to investigate the presence of B.L.O. in large numbers of symptomatic plants. Moreover the DAPI test has to be used carefully as it is not specific of the B.L.O. and can also detect other MLO pathogens in strawberry. B.L.O. transmission from strawberry to Catharanthus roseus by dodder is underway. As the insert vector(s) of the disease is unknown, control of the disease is done by eradication of infested plants only in nurseries.

Nourrisseau, J., Lansac, M. and Garnier, M. (1993). ASSOCIATION OF A B.L.O. TO MARGINAL CHLOROSIS: A NEW DISEASE OF STRAWBERRY. Acta Hortic. 348, 516-516
DOI: 10.17660/ActaHortic.1993.348.110

Acta Horticulturae