Further studies on cucurbit yellow stunting disorder closterovirus in Spain
The out-of-season cultivation of cucurbits under plastic is of major economic importance in many Mediterranean countries. In particular in Spain, melons and cucumbers under plastic occupy 16,000 ha along the south-eastern coast. Since the late 1970s, melons and cucumbers have been seriously affected by yellowing diseases transmitted by whiteflies. In Spain, beet pseudo-yellows closterovirus transmitted by Trialeurodes vaporariorum was found (it is thought that cucumber chlorotic spot closterovirus observed in France is also a strain of beet pseudo-yellows closterovirus). Since the early 1990s, cucurbit yellow stunting disorder closterovirus (CYSDV - EPPO Alert List) transmitted by Bemisia tabaci (EPPO A2 quarantine pest) has been observed (see also EPPO RS 97/063). It is noted that the appearance of this virus disease coincided with the displacement of T. vaporariorum by B. tabaci. In Spain, populations of B. tabaci are essentially composed of the B biotype (also referred to as B. argentifolii) and the Q biotype which seems specific to Spain and Portugal.
During 1994-1997, samples of yellowing melons and cucumbers were collected from the regions of Almería, Málaga and Murcia during winter and spring, and tested by RT-PCR. On the 96 melon samples tested, 30% were infected by CYSDV and none by beet pseudo-yellows closterovirus. 75 % of the 134 cucumber samples were infected by CYSDV (and 3 samples were also infected by beet pseudo-yellows closterovirus). Additional tests were done for lettuce infectious yellows closterovirus (EPPO A1 quarantine pest) and cucurbit aphid-borne luteovirus (virus found in some places in Europe, see EPPO RS 94/210), but all results were negative. A natural infection of courgette by CYSDV was found for the first time in one crop in Almería. Although courgette and watermelon are experimental hosts of CYSDV, the crops are not widely affected by CYSDV. Finally, transmission experiments showed that both B and Q biotypes of B. tabaci were efficient vectors of CYSDV, whereas the A biotype was inefficient.
Sources
Berdiales, B.; Bernal, J.J.; Sáez, E.; Woudt, B.; Beitia, F.; Rodrígues-Cerezo, E. (1999)
Occurrence of cucurbit yellow stunting disorder virus (CYSDV) and beet pseudo-yellows virus in cucurbit crops in Spain and transmission of CYSDV by two biotypes of Bemisia tabaci.
European Journal of Plant Pathology, 105(2), 211-215.