Viral diseases are one of the limiting factors for cucurbit production around the world that some of these viruses can cause a severe reduction in crop yield. In the present study, 92 leaf and fruit samples of various species of cucurbits were collected from different farms in Zanjan and Hamedan provinces, based on descripted symptoms such as yellowing, mosaic, deformation, leaf asymmetry, and wrinkling of leaf veins, to detect and investigate the incidence of some important viruses in cucurbit fields. After total RNA extraction, RT-PCR were conducted using specific primers for Cucumber mosaic virus (CMV), Cucurbit aphid-borne yellows virus (CABYV), Cucumber green mottle mosaic virus (CGMMV), Squash mosaic virus (SqMV), Ourmia melon virus (OuMV), Zucchini yellow mosaic virus (ZYMV), and general primers of the Orthotospovirus genus to amplify a part of the genome corresponded with each of these viruses. The results showed evidence of the presence of CMV, CGMMV, ZYMV, and CABYV, in the tested samples, while OuMV, SqMV and Orthotospoviruses were not detected in any of the tested samples. Among the detected viruses, CABYV was detected as the most common virus. Phylogenetic analysis of the new isolates and other isolates from different countries showed that CMV strains were placed in both subgroups I and II. The newly detected ZYMV strains from Zanjan were clustered with the Vietnamese strain, and CGMMV strains were grouped with strains from India, Pakistan, Uzbekistan, the Netherlands, and Spain in the cluster II. CABYV strains were grouped in the Mediterranean, Asian, and a new independent group, along with the Taiwanese and Indonesian strains. In addition, mixed infections of those virus infections were detected commonly in squash and cucumber. Especially, CGMMV+CABYV, CMV+CABYV and the infection of ZYMV+CABYV+CMV, ZYMV+CGMMV+CMV, and ZYMV+CGMMV+CABYV mixed infections were detected. The results of this study will be useful in developing management strategies to reduce losses of cucurbit viruses.
