Dictyothyrium hibisci (F. Stevens) Gadgil & M.A. Dick 2014
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Nomenclature
Classification
Associations
Descriptions
Dictyothyrium hibisci (F. Stevens) Gadgil & M.A. Dick 2014
This fungus was originally described from Hawaii on Hibiscus sp. as Microthyriella hibisci (Stevens 1925). According to Müller and von Arx (1962) Microthyriella Höhnel is a synonym of Schizothyrium Desmazières. This view is generally accepted (Kirk et al. 2008) and most species previously placed in Microthyriella have been transferred to Schizothyrium. Müller and von Arx (1962) also pointed out that Microthyriella hibisci, did not follow the type of Microthyriella and was wrongly placed in that genus. Microthyriella rickii (Rehm) Höhnel, the type species of Microthyriella (in common with species in Schizothyrium), does not have an ostiole, the whole surface of the shield splitting and allowing the ascospores to escape. As Microthyriella hibisci has a distinct ostiole, it does not belong in Microthyriella and has to be redisposed to a genus other than Schizothyrium. Morphologically, M. hibisci belongs to the Micropeltidaceae and all keys (Batista, 1959; Müller and von Arx, 1962; Luttrell 1973; von Arx and Müller 1975) show that it is best placed in Dictyothyrium Theissen. Molecular analysis yielded no close matches to any records in Genbank.
The thyriothecia of the fungus are entirely superficial, the shield-shaped fruiting bodies merely sitting on the leaf surface without a basal wall. No superficial mycelium was seen and there is no penetration of the host tissue. The concentric arrangement of the thyriothecia (Figure 3A) makes the fungus easily recognisable. It is not uncommon in New Zealand. It has also been recorded (as Microthyriella hibisci) in Australia (Walker and McLeod 1971).