Epidemics of TYLCSV and TYLCV in tomato crops in Calabria (Southern Italy)

Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV) are the two main whitefly-transmitted viruses affecting protected and open field tomato crops in southern Italy. TYLCSV has been detected since the late 1980s in Sicily and Sardinia, whereas TYLCV was detected in Sicily in 2003 and only recently in continental Italy, in 2004. In Calabria (Southern Italy), a yellow leaf curl disease has been described since the early 1990s in tomato, but precise information concerning the causal agent responsible for the observed disease is still not available for this region. Thus, surveys were undertaken for tomato yellow leaf curl viruses in tomato-growing areas of Calabria, both in the field and in plastic greenhouses. Observed symptoms included yellowing, leaf curling and stunting. Collected samples were subjected to molecular analysis using PCR amplification coupled to RFLP in order to discriminate between TYLCSV and TYLCV. The results obtained from the molecular investigation clearly showed the presence of both viruses in greenhouse as well as in field cultivation. Single plants have been shown to be infected by the two viruses singularly, as well as together in mixed infections. These data represent a further confirmation of TYLCV spread in continental Italy and highlight the risks which might derive from the selection of more aggressive recombinants between TYLCSV and TYLCV, as reported for other Mediterranean countries. It would also complicate the breeding strategy for the selection of promising resistant/tolerant tomato genotypes.