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Hendersonula toruloidea

Neoscytalidium dimidiatum
Neoscytalidium dimidiatum microscopic.jpg
Scientific classification
Kingdom: Fungi
Division: Ascomycota
Class: Dothideomycetes
Order: Botryosphaeriales
Family: Botryosphaeriaceae
Genus: Neoscytalidium
Species: N. dimidiatum
Binomial name
Neoscytalidium dimidiatum
(Penz.) Crous & Slippers (2006)
Synonyms
  • Torula dimidiata Penz. (1882)
  • Hendersonula toruloidea Nattrass (1933)
  • Scytalidium dimidiatum (Penz.) B. Sutton & Dyko (1989)
  • Fusicoccum dimidiatum (Penz.) D.F. Farr (2005)

Neoscytalidium dimidiatum was first described in 1933 as Hendersonula toruloidea from diseased orchard trees in Egypt. Decades later, it was determined to be a causative agent of human dermatomycosis-like infections and foot infections predominantly in the tropical areas; however the fungus is considered to be widespread. A newer name, Scytalidium dimidiatum, was applied to synanamorph of Nattrassia mangiferae, otherwise known as Neofusicoccum mangiferae. Substantial confusion has arisen in the literature on this fungus resulting from the use of multiple different names including: Torula dimidiata, Scytalidium dimidiatum, Fusicoccum dimidiatum, and Hendersonula toruloidea.

In 1933, British mycologist Dr. Rolland Marshall Nattrass described an arthroconidial asexual fungus that he named H. toruloidea that was responsible for causing die-back disease of plum, apricot and apple trees in Egypt. At the time, he recognized that single spore cultures of the fungus yielded two "forms" in culture - a mycelial form resembling members of the genus Torula that produced fragmenting chains of arthroconidia, and a pycnicial form characterized by the production of greenish, ellipsoidal spores that oozed from tiny sacs. The name H. toruloidea applied to the latter pycnidial form. Others likened the Torula form to Torula dimidiata described by Otto Penzig in 1882. Despite that the fungus was known by this name for over 50 years by one or the other of these names, increased scrutiny of the species and its close relatives using molecular genetic methods spawned significant controversy in its taxonomy and naming.

In 1989 Sutton and Dyko created the genus Nattrassia to accommodate H. toruloidea and applied the name Scytalidium dimidiatum to the mycelial synanamorph. They also included in the new genus Nattrassia a fungus described by father-son mycologists Paul and Hans Sydow as Dothiorella mangiferae, which became Nattrassia mangiferae, thought to be very closely related to and perhaps indistinguishable from Nattrass's original pycnidial form. Farr and coworkers recognized that both states were asexual forms affiliated with the genus Fusicoccum, an anamorph of the plant pathogenic ascomycete genus, Botryosphaeria. They proposed the transfer of Scytalidium dimidiatum to the genus Fusicoccum as F. dimidiatum. A reappraisal of the family Botryosphaeriaceae by Crous and coworkers in 2006 concluded that the genus Fusicoccum was polyphyletic, and they created a new genus, Neoscytalidium to accommodate Nattrass's fungus. Separately they erected the genus Neofusicoccum to accommodate Nattrassia mangiferae. Crous and colleagues concluded it inappropriate to collapse the entirety of Scytalidium with Fusicoccum because they demonstrated N. dimidiatum to be phylogenetically distinct from Neofusicoccum mangiferae; thus, they interpreted N. dimidiatum to be the correct name for Nattrass's fungus.


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