Family: Partitiviridae

Genus: Deltapartitivirus

Distinguishing features

All members of the genus Deltapartitivirus infect plants. Deltapartitiviruses have two dsRNA segments that are believed to be individually encapsidated in separate particles and the genome is typically 3.1–3.2 kbp in total. 

Virion

Morphology

The virions of pepper cryptic virus 1 and pepper cryptic virus 2 are isometric and approximately 30 nm in diameter (Sabanadzovic and Valverde 2011).  

Physicochemical and physical properties

Virions of beet cryptic virus 2 have a buoyant density of  1.36 g cm⁻³ in CsCl gradients (Accotto and Boccardo 1986). 

Nucleic acid

Viral genome comprises two dsRNA segments, which are individually about 1.6–1.7 and 1.4–1.6 kbp. 

Proteins

There is a single major coat protein (CP) with predicted Mr ranging from 38 to 49 kDa. The Mr of the RNA-dependent RNA polymerase (RdRP), as predicted from nucleotide sequence analysis, is  approximately 54 kDa. Virion-associated RNA polymerase activity is present. 

Genome organization and replication

Each genome segment is monocistronic: dsRNA1 codes for the RdRP and dsRNA2 codes for the major CP. Additional dsRNA segments representing second versions of dsRNA2 and encoding seemingly full-length capsid proteins with unknown function have been detected in several deltapartitiviruses, including beet cryptic virus 2 (HM560704), Fragaria chiloensis cryptic virus (DQ355439), Raphanus sativus cryptic virus 2 (DQ218038) and Rose cryptic virus 1 (EU413668). Deltapartitiviruses do not usually have long poly(A) tracts near the plus-strand 3′-terminus of their genome segments. 

Biology

Deltapartitiviruses induce  persistent infections in plants. They are transmitted by ovule and by pollen to the seed embryo. 

Species demarcation criteria

The species demarcation criteria within genus Deltapartitivirus are:

• ≤ 90% aa sequence identity in the RdRP, and
• ≤ 80% aa sequence identity in the CP

Related, unclassified viruses 

Virus names and virus abbreviations are not official ICTV designations. 

* Representative isolate of a virus with a complete published genome sequence

^‡ Segment encoding the larger version of CP