Identification and distribution of viruses responsible for mosaic diseases affecting cucurbits in Tunisia.
Cucurbits are economically important in Tunisia. These crops are exposed to many viral diseases that have a negative effect on the yield and commercial value of the production. Severe mosaic on leaves of cucurbits was observed in outdoor crops and under plastic-tunnels. Following these observations, two major surveys were conducted in 2000-01 and 2002-03 to attempt to identify these viruses using DAS-ELISA. Samples were collected from the major production areas of cucurbits in Tunisia and were tested for the presence of Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), Moroccan watermelon mosaic virus (MWMV), Papaya ringspot virus (PRSV-W), Zucchini yellow fleck virus (ZYFV), Cucumber mosaic virus (CMV), Squash mosaic virus (SqMV) and Melon necrotic spot virus (MNSV). This study confirmed the occurrence of six viruses (WMV, CMV, PRSV-W, ZYMV, ZYFV and SqMV) already reported in Tunisia with a notable evolution of ZYMV frequency in all regions and species. The percentage of infection with ZYMV reached the 34% in the second major survey (2002-03). In contrast MWMV was absent in all tested samples. We also reported the first occurrence of MNSV in more than 9% of all tested samples of cucurbits namely melon in outdoor crops and on squash and on watermelon under plastic tunnels. Moreover, a wild cucurbit species Ecballium elaterium was found infected with ZYFV and for the first time with CMV, PRSV-W and WMV. A percentage of samples showing mosaic symptoms could not be explained by the presence of any of these studied viruses. This might be explained by the involvement of other viruses or abiotic factors which remain to be identified.