First Report of Watermelon Mosaic Virus Infecting Luffa cylindrica in Shandong, China

Watermelon mosaic virus (WMV, genus Potyvirus, family Potyviridae) was first described in Israel by Cohen and Nitzany (1963) and has a wide host range, encompassing more than 170 plants from 27 families (Lecoq et al. 2011). In July 2024, a Luffa cylindrica sample with virus-like symptoms (e.g., mosaic and vein clearing) was collected from the Luffa cylindrica germplasm in the resource nursery (35°38N, 116°20E) of Tai'an City, Shandong Province, China. Total RNA was extracted from the Luffa cylindrica sample, and RT-PCR was performed (primers: WMV-F: 5’-CCAGTGGCAAAGGTGATA-3’ and WMV-R: 5’-TGCTGCGTCTGAGAAATG-3’; product size: 458 bp) (Wang et al. 2010). BLASTn analysis of the sequenced PCR products revealed that the tested sample shared 98% nucleotide identity with the WMV HS-sq6 isolate (MN854646). This partial WMV sequence was submitted to GenBank with the accession number PQ119827. In addition, the WMV coat protein (CP) antibody was used to detect WMV by western blot. A 37 kD WMV CP protein was detected from the corresponding diseased samples taken from Tai’an City, using a 1:6500 dilution of the WMV antibody. To determine the occurrence of WMV infection in Luffa cylindrica, as mentioned earlier, 50 leaf samples with viral symptoms (collected from Tai'an City, Shandong Province) were tested using RT-PCR, 32 of which were positive for WMV. To the best of our knowledge, this study reports the first documented case of watermelon mosaic virus infection in Luffa cylindrica in Shandong Province, China. Luffa cylindrica is rich in nutrients and is an important vegetable crop in China and other countries. As China is the primary growing area for Luffa cylindrica, improving WMV detection and monitoring is crucial here.