Occurrence, Genetic Variability, and Symptomatology of Potyvirus citrulli (Watermelon Mosaic Virus) Infecting Cucurbits in Iraq

During 2022-2023 growing season, 11 Iraqi provinces were surveyed for the prevalence of Potyvirus citrulli in cucurbit fields. Thirty-six symptomatic samples were screened using reverse transcription-polymerase chain reaction and three sets of potyviral specific primers targeting the partial helper component proteinase (HCPro), cylindrical inclusion (CI), and nuclear inclusion b protein (Nib) genes within P. citrulli genome. Twentynine out of 36 samples were infected with P. citrulli. Sequence comparisons of the three genomic regions revealed that 17 isolates shared 88-100% nucleotide identity with isolates from National Center for Biotechnology Information indicating they were genetically variable. Phylogenetic analyses confirmed the variation of HC-Pro, CI, and NIb separating the 17 isolates within P. citrulli group. The high nucleotide sequence identity to existing isolates suggests successful introduction enabling to overcome and adaptation of those isolates to the Iraqi environment. Inoculation tests revealed variable symptoms, when zucchini plants exhibited the most severe symptoms compared to watermelon and cucumber plants. These findings highlight that P. citrulli can be a serious threat to cucurbit cultivation in Iraq.