piiloviruses

Piiloviruses are a genus of plant-infecting viruses in the order Tymovirales, family Betaflexiviridae. The name "piilo" is Finnish for "hidden," referring to the difficulty in detecting these viruses due to their low concentrations in infected plants. Piiloviruses are transmitted by fungal vectors, specifically species of the oomycete genus *Phytophthora*. They possess a single-stranded, positive-sense RNA genome. The virions are filamentous and flexuous, with a characteristic length of approximately 750-800 nanometers. Replication occurs in the cytoplasm of host cells. Symptoms of piilovirus infection in plants can vary but often include mild mosaic patterns, stunting, or leaf distortion. However, due to their cryptic nature, symptoms may be absent or difficult to distinguish from other stressors. Diagnosis typically relies on molecular methods such as RT-PCR, as serological assays are often unreliable. Several species are recognized within the genus, infecting a range of plant hosts, including crops and wild plants. Research into piiloviruses is ongoing to better understand their epidemiology, host interactions, and potential impact on agriculture.