The two common-aphid transmitted virus diseases affecting tomatoes in France, Italy and other mediterranean countries are Cucumber Mosaic Virus (CMV), and Potato Virus Y (PVY). The different strains of the two viruses may be roughly classed into mosaic or non-necrotic and necrotic types.
Potato Virus Y though isolated as late as 1972 in France, it was not a damaging disease. Nevertheless, this virus is already known as an important disease of tomatoes in other continents (Australia, South America). Since the last 6 years very severe damages have been observed on protected and open field grown commercial tomato crops in south France ( Gebre Selassie et al., 1987a). A Lycopersicon hirsutum PI 247087 line has been reported as resistant to Australian PVY strains by J.E. Thomas (1981). The same line has been tested against PVY French strains and was found resistant (Gebre Selassie et al., 1987b). Therefore a breeding program was started in 1985 and is well advanced.
Cucumber mosaic virus has already caused severe epidemics in 1974 in commercial field grown tomatoes in East France. The virus has remained in most mediterranean countries to cause severe but sporadic damage in tomatoes. Since the las few years very severe damage has been observed in protected and open field grown commercial tomato crops. Therefore screening for possible sources of resistance was started in 1989 in France and Italy. A collection of 18 lines belonging to 6 species were tested:
*Lycopersicon esculentum var cerasiforme: *Lycopersicon hirsutum:
- WVa 106 - Bruinsma
- LA 1393
*Lycopersicon pimpinellifolium: - LA 1777
- hirsute - PI 126449
- LA 121 - PI 134417
- typique site n^o^10 - PI 247087 Australia
- WVa 700
*Lycopersicon peruvianum:
*Lycopersicon chmielewskii: - CMV selec. INRA
- one accession - PI 128648-6
- PI 127831
*Lycopersicon pennellii: - PI 127832
- one accession from Clayberg - PI 126435
The plants were tested in greenhouse and open field conditions. For the
greenhouse test 4 mosaic or fernleaf and 1 necrotic type strains were used in
France and 1 mosaic and 1 necrotic strain in Italy. Plants were mechanically
inoculated at abut the 4th leaf stage. Every plant was checked for symptom
and absence of infection visually and serologically by DAS-ELISA test
technique.After the results of the two trials (greenhouse and open field) in the two different countries, we have found the L. hirsutum line PI 247087, that was already found resistant to PVY, was also more resistant that the other lines against CMV in the two different countries. Though we have found antoher new source of resistance agianst CMV in the 247087 line, it is necessary to evaluate and compare the performance of this line with the lines that we have received from J.L. White and J.M. Kaper (1987). Moreover, it will be interesting to to elucidate if the two viruses CMV and PVY are controlled by identical or different mechanisms.
Literature cited
Gebre Selassie K., G. Marchoux, H. Laterrot and D. Blancard 1987a Graves attacques de la tomate par des souches necrogenes du Virus Y de la Pomme de Terre. P.H.M. - Revue Horticole, no. 281, 43-46.
Gebre Selassie, K., H. Laterrot and G. Marchoux 1987b Breeding tomatoes for resistance against necrotic strain of Potato Virus Y. 10. Meeting Eucarpia Tomato Working Group "Modern trends in tomato genetics and breeding". Pontecagnano (ITA), 25.
Thomas, J.E. 1981 Resistance to Potato Virus Y in Lycopersicon species. Aust. plant. Pathol. 10. 67-68.
White, J.L. and J.M. Kaper 1987 Absence of lethal stem necrosis in select Lycopersicon spp. infected by cucumber mosaic virus strain D and its necrogenic satellite CARNA 5. Phytopathology 77, 808-811.