Non-cucurbitaceous weed species shown to be natural hosts of Cucumber vein yellowing virus in south eastern Spain

Cucumber vein yellowing virus (CVYV) was first detected in Cucumis spp. in Israel (Cohen & Nitzany, 1960) but has since been reported to occur also in Jordan (Mansour, 1993) and, more recently, in Spain (Cuadradro et al., 2001). Since its detection in south east Spain in the autumn of 2000, this Bemisia tabaci-transmitted virus has occurred with increasingly frequency in cucurbitaceous crops in Almeria, Granada and Murcia (Cuadrado et al., 2001).

During the spring of 2001, leaf symptoms that ranged from vein clearing to general leaf chlorosis occurred on weed species that commonly grow within or near commercial horticulture greenhouses. Samples of six weed species were collected and tested for CVYV by RT-PCR using CVYV-specific primers (Cuadrado et al., 2001). A single band of the expected size (449 bp) was amplified in nucleic acid extracted from the following weed species: Ecballium elaterium (Cucurbitaceae) (Fig. 1a), Convolvulus arvensis (Convolvulaceae), Malva parviflora (Malvaceae), and Sonchus oleraceus (Fig 1b), S. asper , and S. tenerrimus (Compositae).

In addition, whitefly transmission was used to confirm that S. oleraceus is a natural host of the virus; healthy female B. tabaci whiteflies (15-20) after being allowed to feed on a naturally infected plant with vein yellowing symptoms, successfully transmitted the virus to 10 healthy cucumber plants as verified by RT-PCR and sequencing of the amplification products.

CVYV was previously reported to have a narrow host range that is restricted to the Cucurbitaceae (Cohen & Nitzany, 1960; Mansour & Al-Musa, 1993). However, in south eastern Spain, natural infection of the six common weed species consistently coincided with an outbreak of CVYV in cucurbitaceous crops and a high infestation rate of B. tabaci in commercial greenhouses. The role of these wild host species thus needs to be considered in developing strategies for the control or eradication of the virus.