Hypovirus

Hypovirus is a genus of viruses, in the family Hypoviridae. Fungi serve as natural hosts. There are four species in this genus. Diseases associated with this genus include: host virulence reduction.
Species.
The following species are recognized:
Structure.
The diameter is around 50–80 nm. Genomes are linear, around 9–13kb in length. The genome has 1 or 2 open reading frames.
Life cycle.
Viral replication is cytoplasmic. Replication follows the double-stranded RNA virus replication model. Double-stranded RNA virus transcription is the method of transcription. The virus exits the host cell by cell to cell movement. Fungi serve as the natural host.
CHV1 – Chestnut blight hypovirulence.
Hypovirus CHV1 is the only hypovirus found in Europe up to 2000. It is known for reducing the virulence of the fungus that causes chestnut blight (i.e. hypovirulence). "Cryphonectria parasitica", the ascomycete fungus, originated in Asia and causes the disease chestnut blight in several chestnut species ("Castanea" spp.). Although symptoms are mild in Asian chestnut species that have co-evolved with the fungus, they are very severe in the North American chestnut species "C. dentata" and also in the European sweet chestnut, "C. sativa". Hypovirus has been used for protection against chestnut blight in Europe since the 1970s.