First report of Cucurbit aphid-borne yellows virus in Italy

In May 2006, a survey was performed to investigate a yellowing viral disease complex in the major cucurbit-growing areas of southern Italy (Campania, Sicily and Basilicata). Symptoms consisted of interveinal mottling and yellowing of older leaves (Fig. 1), combined with thickening and brittleness. These were observed in several melon crops, both under plastic-tunnels (Cucumis melo var. cantalupo) and in the open field (Cucumis melo var. inodorus). Yellowing disorder is reported to be caused primarily by three different viruses that are widespread in many countries of Mediterranean Basin: Beet pseudo-yellows virus (BPYV, genus Crinivirus, family Closteroviridae; Tomassoli et al., 2001) that has affected melon and cucumber in Sardinia (Italy) since 2001; Cucurbit yellow stunting disorder virus (CYSDV, genus Crinivirus , family Closteroviridae; Celix et al., 1996) and Cucurbit aphid-borne yellows virus (CABYV, genus Polerovirus, family Luteoviridae; Lecoq et al., 1992).

Total RNA was extracted from leaf tissue of symptomatic and asymptomatic plants and screened for the presence of BPYV and CYSDV using RT-PCR methods (Tomassoli et al., 2001; Celix et al., 1996). The analysis showed that only a few plants with symptoms from Campania were positive to BPYV, while none of the samples were infected with CYSDV. RT-PCR assays were carried out using a primer set specific to the CABYV coat protein gene (Jaurez et al., 2004) in a one-step procedure; a Spanish isolate was used as positive control. Electrophoresis of the RT-PCR products showed a fragment of the predicted size (ca. 600bp) from 39 of 80 samples showing symptoms. All plants without symptoms, the healthy and water controls tested negative. Amplified DNA obtained from two different samples (S7 from Sicily and C49 from Campania) were sequenced (GenBank Acc. Nos. EF029114 and EF029115) and subjected to nucleotide sequence analysis using BLAST. Both isolates shared the highest nucleotide sequence identity (99%) with the isolate CABYV-N (GeneBank Acc. No. X76931).

CABYV was found in all three of the regions surveyed. In total, 72% of the sites showing yellowing-symtpoms were infected by the virus. The highest frequency of CABYV occurred in the winter-melon growing areas (Basilicata and Sicily) during the summer period. This is the first report of the occurrence of CABYV in Italy.

Acknowledgments

The authors would like thank Dr. M. Jaurez for the CABYV isolate. This work was supported with project PROM from Ministry of Agriculture (Italy).