First report of mosaic disease of crape myrtle caused by watermelon mosaic virus in Jiangsu Province in China

The crape myrtle (Lagerstroemia indica) is a deciduous shrub and becomes a popular landscape tree on public or private properties. However, crape myrtle is constantly subjected to multiple pathogen attacks, which severely affect the yield and quality and cause economic losses. In June 2019, foliar virus-like symptoms chlorosis and mosaic were observed on plants of crape myrtle in Yangzhou city, Jiangsu Province, east China. Leaf samples were collected from symptomatic crape myrtle plants. All samples were assayed by western blotting using polyclonal antiserum to cucumber mosaic virus (CMV), and tobacco mosaic virus (TMV) and double-antibody sandwich (DAS)-ELISA assay for watermelon mosaic virus (WMV). Results revealed the all samples reacted positively with the WMV but negative with CMV and TMV. Next, RT-PCR was employed to confirm the obtained serological results. An amplicon of 288 bp was obtained from all the samples. Nucleotide BLAST analysis revealed that the sequence had 98.25-100% nucleotide identity to 8 isolate WMV sequences available in GenBank. A pathogenicity assay was conducted using virus-free Nicotiana benthamiana seedlings inoculated with sap extracted from symptomatic crape myrtle leaves. Systemic infection of WMV was also confirmed in N. benthamiana by RT-PCR. On the basis of the data from serological and molecular analyses, the virus was identified as WMV. To our knowledge, this is the first report of WMV on crape myrtle in Jiangsu Province in China.