Genus Bromovirus

Type Species	Brome mosaic virus	(BMV)

Virion Properties

Morphology

Virions are polyhedral, and all the same size, with a diameter of 27  nm.

Physicochemical and Physical Properties

Virions prepared below pH 6.0 have S_20w of 88S, are stable to high salt and low detergent concentrations, and are nuclease- and protease-resistant. At pH 7.0 and above, virions swell to a diameter of 31  nm, S_20w decreases to 78S, salt and detergent stability decreases dramatically, and protein and RNA are susceptible to hydrolytic enzymes. This swelling is accompanied by conformational changes of the capsid which are detectable by physical and serological means.

Nucleic Acid

RNA 3-termini are tRNA-like, are very similar in all viruses sequenced so far, and can be aminoacylated with tyrosine.

Proteins

Coat protein Mr is 20 10³, unlike the 24-26 10³ of other members of the family Bromoviridae. The 3a and CPs of Bromovirus species share sequence similarities with one another, and more distantly with Cucumovirus spp., but not with Ilarvirus or Alfamovirus spp.

Antigenic Properties

All members are serologically related, although antigenic differences between species are large.

Biological Properties

The natural host range is narrow, and is limited to a few plant hosts for each species. All species are thought to be beetle-transmitted, although Brome mosaic virus (BMV) is inefficiently transmitted by aphids in a non-persistent manner.

List of Species Demarcation Criteria in the Genus

The criteria demarcating species in the genus are:

	Host range,
	Serological relationships,
	Compatible replicase proteins (i.e., 1a and 2a proteins),
	Nucleotide sequence similarity between species ranges from 50 to 80% depending on the gene used for comparison.

List of Species in the Genus

Official virus species names are in italics. Tentative virus species names, alternative names ( ), strains or serotypes are not italicized. Virus names, CMI/AAB description numbers ( ), genome sequence accession numbers [ ], and assigned abbreviations ( ) are:

Species in the Genus

Broad bean mottle virus (101)	[K01776, K01777, K01778, M64713, M65138, M60291]	(BBMV)
Brome mosaic virus (3, 180)	[V00099, J02042, J02043, K02706, K02707, X01678, X02380, M25172]	(BMV)
Cassia yellow blotch virus		(CYBV)
Cowpea chlorotic mottle virus (49)	[M28817, M28818, J02052, K01779, K01780, M65139, M18658, M65155]	(CCMV)
Melandrium yellow fleck virus (236)		(MYFV)
Spring beauty latent virus		(SBLV)

Tentative Species in the Genus

None reported