Pseudodiploid (also called "pseudoploid") refers to one of the essential components in viral reproduction. It means having two RNA genomes per virion but giving rise to only one DNA copy in infected cells.
The term is also used to refer to cells that are diploid, but have chromosomal translocations.
Retrovirions for example are considered as pseudoploid in character - they have two genomes encapsidated, but in general only one provirus is seen after infection with single virions.
Retrovirus particles contain two copies of the RNA genome held together by multiple regions of base pairing (strongest pairing at 5’ ends) which is also called 70S complex (dimer of 35S genomes). This property gives viruses evolutionary advantages such as the capability to survive extensive damage to their genomes as at least parts of both genomes are used during the reverse transcription process. It also explains the high rates of genetic recombination in retroviruses. The retroviral genome is coated by a viral nucleocapsid (NC) protein that may function like a single stranded binding protein and therefore is enhancing processivity and facilitating template exchanges. The NC first organizes RNA genomes within the virion and then facilitates reverse transcription within the infected cell.