Cucurbit yellow stunting disorder virus (Genus Crinivirus) Associated with the Yellowing Disease of Cucurbit Crops in Portugal

During autumn 1998, chlorotic mottling, yellowing, and stunting symptoms were observed on cucumber (Cucumis sativus L.) plants in an experimental plot, in Algarve, southern Portugal. The first symptoms appeared 3 weeks after planting, associated with a heavy infestation of Bemisia tabaci (Gennadius). Plants affected early produced few and small fruits. Analysis of double-stranded RNA (dsRNA) extracted from symptomatic cucumber leaves revealed the presence of two dsRNAs of about 8 and 9 kbp, not present in healthy cucumber plants. Reverse-transcription polymerase chain reaction (RT-PCR) using dsRNA or total RNA extracts as template and the oligonucleotide primers 410L and 410U (1), specifically amplified a fragment of expected size of the HSP70-homolog gene of Cucurbit yellow stunting disorder virus (CYSDV). The RT-PCR-amplified fragment was sequenced (Acc. No. AF287474) and showed 99% sequence identities with the corresponding sequences (GenBank accessions AJ223619 and U67170) from two CYSDV isolates belonging to group I (2), confirming CYSDV detection. CYSDV was also detected in samples of cucumber, melon (Cucumis melo L.) and watermelon (Citrullus lanatus [Thunb.] Matsun.) collected during the summer of 1999 in commercial greenhouses. CYSDV is an emerging and important virus of cucurbits in the Middle East and Mediterranean Europe (2). This is the first report of CYSDV infecting cucurbit crops in Portugal.