Observation 99305: Hypoxylon rubiginosum (Pers.) Fr.

When: 2012-07-01

Collection location: Greensburg, Pennsylvania, USA [Click for map]

Who: John Plischke (John Plischke)

No specimen available



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Recognized by sight
Based on microscopic features

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By: Danny Newman (myxomop)
2016-08-08 16:07:57 PDT (-0700)

particularly in light of all the look alikes:

“Hypoxylon rubiginosum has long been a broadly circumscribed complex of species (Miller, 1961). Petrini & Müller (1986) were the first to recognize H. rubiginosum in the narrow sense adopted herein, separating it from two taxa to which they gave the varietal rank, H. rubiginosum (Pers.:Fr.) Fr.var. cercidicola (Berk.& Curtis ex Peck) L.E. Petrini and H. rubiginosum (Pers.: Fr.) Fr.var. perforatum ( Schw.) L. E. Petrini. In their revision of the genus Hypoxylon, Ju & Rogers (1996) assessed that all tropical species formerly included under the epithet rubiginosum could be separated from the North temperate taxon based on pigments yielded in KOH and morphological and cultural data. They likewise considered H. perforatum (Schw.:Fr.)Fr. a distinct species owing to its amber pigments in KOH and its Virgariella-like anamorph. More recently, chemical data provided by HPLC techniques confirmed the presence of a peculiar secondary metabolite (hypomiltin) in stromata of H. perforatum (Stadler et al., 2005) and confirmed that the morphological differences between H. rubiginosum and its variety cercidicola were supported by differences in secondary metabolites (Stadler et al., 2004b). The new name H. petriniae Stadler & Fournier was given to this former variety, for the epithet cercidicola remains ambiguous. (See notes under H. petriniae).

As to HPLC profile, H. rubiginosum is characterized by the association of mitorubrin, rubiginosin A and orsellinic acid as main secondary metabolites (Stadler et al., 2004b). Rubiginosins B and C, rubiginosic acid, entonaemin A and daldinin C were additional compounds recently isolated (Quang et al., 2004)

Among the other Hypoxylon species sharing with H. rubiginosum its stromatal colour and its orange KOH-extractable pigments, H. rutilum differs in having papillate ostioles and ascospores averaging less than 10 µm long, H. cercidicolum differs in having a swollen stellate stromatal margin and an inamyloid apical ring, H. ferrugineum and H. julianii differ in having ascospores averaging more than 15 µm long, and H. laschii differs in having erumpent pulvinate stromata and ascospores averaging less than 10 µm long. Hypoxylon crocopeplum, a taxon recently recorded from Europe for the first time, is much like H. rubiginosum in gross morphology. Its immature stromata are distinctive in having a brighter orange colour and greyish discs around ostioles; moreover, its ascospores are larger and have a sigmoid germ slit.

H. ticinense and H. subticinense differ mainly from H. rubiginosum in their peculiar discoid undulate stromata, lying on a thick black basal tissue, lined with a yellow fimbriate margin when young. Moreover, the former differs in having ascospores averaging less than 7 µm long, while the latter differs in having ellipsoid-equilateral ascospores.

Two recently described species closely related to H. rubiginosum are H. liviae (Granmo, 2001) and H. salicicola (Granmo, 1999). Both are host specific, the former is specific for Sorbus aucuparia, the latter for Salix sp., and are likely to have a boreal distribution. These two species are still unknown from France. Hypoxylon liviae differs from H. rubiginosum in having whitish pruinose brown stromata, yellow stromatal granules yielding luteous (12) to sienna (8) pigments in 10% KOH, and dark brown nearly equilateral ascospores. Hypoxylon salicicola is much like H. rubiginosum and differs primarily in having smaller perithecia 0.1-0.35 mm diam and smaller ascospores 7-10 × 3-4.5 µm. Ju and Rogers (1996) cultured it and observed a Nodulisporium-like anamorph, but growing more slowly than that of H. rubiginosum."

emphasis mine – Source

Hi John
By: Martin Livezey (MLivezey)
2012-07-06 04:59:03 PDT (-0700)

Any chance we will get to see the images through the scope?

Created: 2012-07-05 21:12:15 PDT (-0700)
Last modified: 2012-07-05 21:14:05 PDT (-0700)
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