Ourmia melon virus, a virus from Iran with novel properties

A virus associated with a mosaic disease in melons in the Ourmia district in northern Iran was mechanically transmissible to a wide range of test plants but was not transmitted using aphids, the whitefly Trialeurodes vaporariorum or the mite Tetranychus urticae. Its rather stable particles somewhat resembled those of both geminiviruses and alfalfa mosaic virus; they were 18·5 nm in mean width, parallel-sided, and of several discrete lengths, 30 nm and 37 nm being the shortest and commonest lengths. Both ends of all particles were sharply triangular in profile. The particles contained linear single-stranded RNA of three sizes, estimated as 0·91,0·35 and 0·32, all × 10⁶ molecular weight, and two coat proteins of 26·3 and 23·3 × 10³ estimated molecular weight. The virus, named Ourmia melon virus, appears to be the first described representative of a new virus group.