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June 20, 2003
Source: Brit Soc Plant Pathol, NEW DISEASE REPORTS, Vol 7 [edited]


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

GP Accotto <g.accotto@ivv.cnr.it> (Istituto di Virologia Vegetale, CNR,Strada  delle Cacce 73, 10135 Torino, Italy.); M Bragaloni (Seminis Vegetables Seeds Italia, Via Canneto di Rodi, 04010 Borgo Sabotino (LT), Italy; D Luison (as for Bragaloni); S Davino (Dipartimento di Scienze e Tecnologie Fitosanitarie,
Università degli Studi di Catania, Via S. Sofia 100, 95100 Catania, Italy; & M. Davino (as for S Davino). Accepted for publication 22/04/03

Since the late 1980's, crops of tomato (_Lycopersicon esculentum_ L.) in Sicily and Sardinia have been severely affected by yellow leaf curl disease. The causal virus was identified as a new geminivirus species, now named Tomato yellow leaf curl Sardinia virus (TYLCSV, formerly TYLCV-Sar, Fauquet et al., 2000). Tomato yellow leaf curl virus (TYLCV, formerly TYLCV-Is), originally described in Israel, causes the same disease in many countries worldwide (Moriones & Navas-Castillo, 2000).

The full genomic sequences of TYLCSV isolates from Sicily (Acc. No. Z28390) and Sardinia (Acc. No. X61153) were determined and used to develop molecular tools specifically for detection of the virus (Accotto et al., 2000). A 570 bp DNA fragment amplified from the capsid protein gene was digested with Ava II restriction enzyme and separated by gel electrophoresis.

Over the past 5 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) was used to identify TYLCSV and TYLCV. Only TYLCSV was
identified in 2001.

In 2002, symptomatic leaf samples were collected in April, September & November from 8 greenhouse grown tomato crops, in different areas of Ragusa province, and DNA was extracted and analysed as above. 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 2 patterns, indicating a mixed infection of both viruses.

Sequence analysis of DNA amplified from 2 samples infected with TYLCV showed that, in this genomic region, the virus isolated in Sicily is more than 95 percent 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, was 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 development of breeding strategies to obtain genetic resistance.

References:

Accotto GP, Navas-Castillo J, Noris E, Moriones E , Louro D. 2000. Typing of tomato yellow leaf curl viruses in Europe. European Journal of Plant Pathology 106,179-86.

Fauquet CM, Maxwell DP, Gronenborn B, Stanley J. 2000. Revised proposal for naming geminiviruses. Archives of Virology 145, 1743-61.

Moriones E, Navas-Castillo J. 2000.Tomato yellow leaf curl virus, an emerging virus complex causing epidemics worldwide. Virus Research
71,123-34.

Sánchez-Campos S, Navas-Castillo J, Camero R, Soria C, Díaz JA, Moriones E. 1999. Displacement of Tomato yellow leaf curl virus (TYLCV)-Sr by TYLCV-Is in tomato epidemics in Spain. Phytopathology 89, 1038-1043.

[TYLC is one of the most devastating viral diseases of cultivated tomato in tropical and subtropical regions worldwide, and losses of up to 100 percent are frequent. It is often the main limiting factor in tomato production. The progressive displacement of TYLCSV by TYLCV in Italy is reminiscent of the same phenomenon earlier in southern Spain, where TYLCV spread very quickly and displaced TYLCSV from that region. Possible reasons that might explain the shift in Spain could be that local biotypes of _Bemisia tabaci_ [whitefly] are more efficient vectors of TYLCV and that common bean (_Phaseolus vulgaris_) is a reservoir host for TYLCV but not for TYLCSV.

Additional reference:
<http://www.apsnet.org/phyto/PDFS/1999/0907-01R.pdf> -Mod. DH]