Characterisation of watermelon curly mottle virus, a geminivirus distinct from squash leaf curl virus

Purified preparations of watermelon curly mottle virus (WCMoV), a whitefly‐transmitted geminivirus, contained dimeric or geminate particles of 20 times 30 nm and the virus was transmissible by mechanical means. Virus yields ranged from 100–150 μg/100 g leaf tissue. Purified preparations exhibited a typical nucleoprotein absorbance profile with a maximum absorbance at 258 nm, and A280 / A260 ratio of 0.61–0.64. Infectivity was associated with two light‐scattering, virus‐containing bands following sucrose density gradient centrifugation. The viral capsid protein was resolved as a doublet by SDS‐PAGE. The estimated mol. wts of the two bands within the doublet were 29 100 (±1550) and 27 733 (±1550), respectively. DNA isolated from virus particles was resolved by gel electrophoresis into two circular single‐stranded DNA bands of approximately 2.6 to 2.7 kb. The two bands are believed to represent the individual components of a bipartite genome, characteristic of previously described whitefly‐transmitted geminiviruses.