Viruses and virus‐like pathogens transmitted by zoosporic fungi 1

The viruses and virus‐like pathogens transmitted by zoosporic fungi are reviewed. The nine furoviruses (and possible members of the group), with labile rod‐shaped particles, have nearly all been shown to be transmitted by plasmodiophoromycete vectors. As they have been reviewed extensively elsewhere, they are covered only briefly; important examples are beet necrotic yellow vein furovirus and potato mop‐top furovirus. Five viruses with filamentous particles, tentatively recognized as poty viruses, are transmitted by Polymyxa graminis . Within this group, wheat yellow mosaic virus should be considered to include wheat spindle streak mosaic virus, while the M and NM forms of barley yellow mosaic virus, the best known members of the group, should probably be regarded as distinct viruses. Chytrids (especially Olpidium brassicae ) transmit a variety of viruses in different groups (e.g. tobacco necrosis necrovirus, lettuce big‐vein virus, melon necrotic spot carmovirus, red clover necrotic mosaic dianthovirus). Finally, several diseases caused by uncharacterized pathogens appear to be transmitted by O. brassicae : freesia leaf necrosis, lettuce ring necrosis, pepper yellow vein, watercress chlorotic leaf spot.