Mechanical inoculation of 12 greenhouse-grown cucumber (Cucumis sativus) cultivars at the three to four-leaf stage with an isolate of zucchini yellow mosaic virus ( ZYMV ) from Saudi Arabia resulted in various symptoms in 11 cultivars. Significant differences in plant height, fruit numbers, and fruit weight were observed between the inoculated and the control plants of the 11 affected cultivars. The cultivar Dina was asymptomatic, and no significant differences were observed between the inoculated and control plants for any of the parameters tested. Virus recovery test from cultivar Dina performed on the susceptible cultivar, Farol, together with lack of virus detection by enzyme-linked immunosorbent assay ( ELISA ) indicated that this ZYMV isolate did not infect Dina. However, inoculation of Dina at the cotyledon stage revealed minor symptoms that were confined to a few of the lower leaves, suggesting that Dina is resistant but not immune to this ZYMV isolate. Virus titer in Dina was low and the virus was restricted to the older leaves; whereas in Farol virus titer was considerably higher and the virus spread to all leaves.

Under greenhouse conditions ( 24-28o C ) , twenty four cucumber, 14 squash, 13 melom, 8 watermelon, and 4 pumpkin cultivars were mechnically inoculated with extract of an isolate of ZYMV at the two true leaves stage. Symptoms were observed on all cultivars of the different cucurbit species, ten days post-inoculation. All tested cultivars were susceptible, except two cucumber “ Dina “ and 3126 / 90, and the bottlegourd cultivar “ Prolific Long “. The negative ELISA results for these cultivars indicates that they are either resistant or immune to this virus isolate