First report of Tomato yellow leaf curl virus (TYLCV) in Italy

Since the late 1980's, tomato (Lycopersicon esculentum L.) crops in Sicily and Sardinia have been severely affected by yellow leaf curl disease. Molecular studies identified a new geminivirus species, now named Tomato yellow leaf curl Sardinia virus (TYLCSV, formerly TYLCV-Sar, Fauquet et al., 2000), as the causal agent. The full genomic sequences of isolates from Sicily (Acc. No. Z28390) and from Sardinia (Acc. No. X61153) were determined and molecular tools for TYLCSV-specific detection were developed (Accotto et al., 2000). Another viral species causing the same disease, Tomato yellow leaf curl virus (TYLCV, formerly TYLCV-Is), was originally described in Israel and currently occurs in many countries worldwide (Moriones and Navas-Castillo, 2000).

Over the past five years, surveys have been conducted in the main tomato production area of Sicily - Ragusa province- to determine whether viral species other than TYLCSV were present. A PCR/RFLP procedure described in Accotto et al. (2000) to identify TYLCSV and TYLCV was used. A 570 bp DNA fragment amplified from the capsid protein gene was digested with Ava II restriction enzyme and separated by gel electrophoresis. Until the end of 2001, only TYLCSV was identified. In 2002, symptomatic leaf samples were collected in April, September and November from 8 greenhouse grown tomato crops, in different areas of Ragusa province. DNA was extracted and analysed as above. Out of 49 samples analysed from individual plants, 16 produced a pattern typical of TYLCSV, 7 that of TYLCV and 26 produced a combination of the two patterns, indicating the presence of both viruses. Sequence analysis of DNA amplified from two samples infected with TYLCV showed that, in this genomic region, the virus isolated in Sicily is more than 95% homologous to TYLCV isolates characterized in many different countries. These include Israel, Portugal, Spain, USA, Japan, Cuba, Dominican Republic, Iran and many others.

This is the first report of TYLCV in Italy. Our data indicates that TYLCV has spread very quickly in an area where the other viral species causing yellow leaf curl disease, TYLCSV, is the only geminivirus detected in previous years (Sánchez-Campos et al., 1999). The data also indicates that mixed infections are very frequent under field conditions, thus complicating the development of breeding strategies to obtain genetic resistance.