Behavior of Watermelon Cultivars after Inoculation with Watermelon mosaic virus in Saudi Arabia

All seven watermelon cultivars that were screened for their reactions to a severe Saudi Arabian isolate of Watermelon mosaic virus (WMV-SA) that was found inducing a severe disease in watermelon in Riyadh region, were found to be susceptible and showed different virus-like symptoms upon mechanical inoculation. Sugar Baby, Crimson Sweet 1 and Crimson Sweet 2 cultivars showed milder symptoms and, therefore, got lower grand mean of weekly symptom ratings than Charleston Gray No. 502, Jubilee, Black Diamond and Charleston Gray No. 133 in both first and second experiments. Artificial inoculation with this isolate significantly reduced the plant height, fresh and dry weights of the tested cultivars. The reduction percentages in plant height of Sugar Baby and Crimson Sweet 2 were significantly lower than those of Crimson Sweet 1, Charleston Gray No. 502 and Charleston Gray No. 133 in both experiments. Also the reduction in percentages of fresh weights of Sugar Baby, Crimson Sweet 2 and Jubilee were significantly lower than reduction percentages of Crimson Sweet 1, Black Diamond and Charleston Gray No. 133. The dry weight reduction percentages of Jubilee, Sugar Baby and Crimson Sweet 2 were lower than those of Charleston Gray No. 502, Charleston Gray No. 133, Black Diamond and Crimson Sweet 1 in both experiments. No correlation existed between the virus titer in the infected cultivars and their performances. In general, Sugar Baby and Crimson Sweet 2 performed better than the other cultivars as they had the lowest symptom severity ratings, the lowest percentages of plant height, fresh and dry weight reductions compared to the other tested cultivars.