Exobasidium cylindrosporum

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Exobasidium cylindrosporum
Subdivision : Ustilaginomycotina
Class : Exobasidiomycetes
Order : Naked Basidia (Exobasidiales)
Family : Nude basid relatives (Exobasidiaceae)
Genre : Naked basidia ( Exobasidium )
Type : Exobasidium cylindrosporum
Scientific name
Exobasidium cylindrosporum

Exobasidium cylindrosporum is a smut fungus art from the family of Nacktbasidienverwandten (Exobasidiaceae). It lives as an endoparasite on rhododendrons ( Rhododendron spp.). Symptoms of infection by the fungus are leaf galls on the upper side of young leaves, from the underside of which white mycelium laterbreaks and the leaf overgrows.


Macroscopic features

Exobasidium cylindrosporum is initially invisible to the naked eye. The initial symptoms of the infestation can be seen on the leaves: the leaves of infected rhododendrons form round or elliptical, concave or convex galls of 9–13 × 4–6.5 mm on the top. Later, white mycelium sprouts between the leaf veins on the underside and begins to overgrow the leaf.

Microscopic features

The mycelium of Exobasidium cylindrosporum grows intercellularly and forms suction threads that grow into the host's storage tissue. The three- to five-pore, 17–30 × 4–6  µm large basidia are long, unseptate and cylindrical. The cylindrical spores are hyaline , 15–20.5 × 4 µm in size and have thin walls. Initially they are unseptate, but when ripe they have 3–8 septums .


Exobasidum cylindrosporum was originally described from Japan, later the species was also found in China.


Exobasidium cylindrosporus attacks rhododendrons ( Rhododendron spp.). The fungus feeds on the nutrients present in the storage tissue of the plants, its basidia later break through the stomata on the underside of the leaf and release spores. These germinate in germ tubes 24 hours after they have fallen on a suitable substrate.


  • Zhenying Li, Lin Guo: Two New Species and a New Chinese Record of Exobasidium (Exobasidiales) from China. In: Mycotaxon 105, 2008. pp. 331-336. ( Full text ; PDF; 940 kB)