VIRUSES INFECTING CUCURBITS IN RIYADH, GASSIM AND HAIL REGIONS OF SAUDI-ARABIA

During 1992 and 1993 growing seasons, 385 curcubit plant samples showi ng virus like symptoms have been collected for the purpose of identify ing nine viruses that might cause cucurbit diseases in Riyadh, Gassim and Hail regions. The direct or indirect ELISA and agar double diffusi on tests have been used for the identification. All the nine plant vir uses to which the tests were performed have been identified in the cen tral area of Saudi Arabia (Riyadh, Gassim and Hail regions). The zucch ini yellow mosaic virus (ZYMV) was identified from all cultivated cucu rbit species: cucumber (Cucumis sativus L.), melon (Cucumis melo L.), watermelon (Citrullus lanatus Thunb.), pumpkin (Cucurbita maxima Duch. ), squash (Cucurbita pepo L.), bottlegourd (Lagenaria siceraria L.) an d snake cucumber (Cucumis melo var flexuoses). The squash mosaic virus (CMV), watermelon mosaic virus-1 (WMV-1) which is known as papaya rin gspot virus (PRSV) were identified from all previously mentioned cucur bit species except from bottlegourd, pumpkin and snake cucumber respec tively. The watermelon mosaic virus-2 (WMV-2) was identified from all species except pumpkin and snake cucumber. The Prune dwarf virus (PDV) has been identified from cucumber, melon, squash, and pumpkin. The cu cumber green mottle mosaic virus (CGMMV) was identified from watermelo n, melon, and bottlegourd. The cucumber leaf spot virus (CLSV) was ide ntified from the plants of squash, pumpkin and bottlegourd, while the beet western yellows virus (BtWYV) was identified from the bottlegourd plants only. The results of this study confirmed that the ZYMV was th e most detected virus affecting all the cucurbit species in the differ ent locations of the central area of Saud Arabia, with 60.5% of detect ion. The lowest detection percentage (0.5%) was observed with BtWYV. T he immunological tests revealed that most of the tested samples had mi xed infections, also it revealed that about 25.7% of these samples gav e negative reactions to all of the tested viruses. This is the first c omplete and comprehensive study on viruses that infect cucurbits in Ri yadh, Gassim and Hail regions which together form the central area of Saudi Arabia. In this study, the WMV-1 was identified in the central a rea for the first time, while four cucurbit viruses which include BtWY V, CLSV, PDV and WMV-2 were identified for the first time not only in the central area alone, but in Saudi Arabia as a whole.