Musicillium theobromae (Turconi) Zare & W. Gams | MYCO-LICH

Musicillium theobromae (Turconi) Zare & W. Gams

ShareThis
Genus: 
Musicillium Zare & W. Gams, Nova Hedwigia 85: 482, MycoBank MB 510696
Species: 
Musicillium theobromae (Turconi) Zare & W. Gams, Nova Hedwigia 85: 482, MycoBank MB510697
Synonymy : 
≡ Stachylidium theobromae Turconi, Atti Ist. bot. R. Univ. Pavia 17: 7 (1920).
Synonymy : 
≡ Verticillium theobromae (Turconi) E.W. Mason & S. Hughes, in Hughes, Mycol. Pap. 45: 10 (1951).

Colonies on OA or PCA reaching 40–50 mm diam in 10 days at ca 20°C, finely floccose, near the centre becoming grey-brown. Vegetative hyphae pale brown, 2–3.5 μm wide, initially not torulose, but after 2 weeks some torulose hyphae develop, initially subhyaline, later brown, 8–10 μm diam, and sometimes aggregating into microsclerotium-like structures. Conidiophores clearly distinct from vegetative hyphae by their brown pigmentation that extends almost up to the highest parts, in some isolates to 250, in others to 500 μm tall, at the base 2.0–2.5(–3.5) μm wide, sometimes indistinctly asperulate, in the lower part with 4–9 septa in 30–50 μm distance, bearing up to 6 whorls of 3–6 phialides in the upper part. Phialides in divergent whorls of 3–6 (rarely solitary), (sub)hyaline, aculeate, 17–35 μm long, tapering from 1.5–2.7 μm near the base to approximately 1(–1.5) μm at the tip; collarette and periclinal wall thickening hardly recognizable. Conidia adhering in slimy heads, hyaline, smooth-walled, cylindrical with symmetrically rounded ends, 4–6.5(–9) ´ 1.0–1.7(–2.0) μm, L/W = (2.5–)3–4.5(–5.4). Odour indistinct.

Type: The species was described from discoloured leaves of Theobroma cacao in the Botanic Garden in Pavia, Italy. No type is preserved in Pavia or Padova (Vanda Terzo, pers. comm.). Hughes (1951) simply stated that the identity of this fungus with the causal agent of cigar-end rot of banana was well established, but this has never been critically examined. In order to formally establish this identity, we designate a dried culture of CBS 968.72, which was isolated from banana in Egypt, as neotype (Herb. CBS 19864).

Discussion: Musicillium theobromae has some similarity with Stachylidium bicolor Link : Fr., in that the conidiophores are similarly pigmented, but in that genus the phialides are relatively short and taper at the tip. Stachylidium theobromae was originally found on discoloured leaves of Theobroma cacao in the Botanic Garden in Pavia, growing together with Physalospora theobromae Turconi.

Musicillium is introduced here for the causal agent of cigar-end rot. The prefix of the generic name chosen highlights the host plant association, while the suffix reflects the organism’s similarity to Verticillium.

The distinction of Musicillium and Verticillium is mainly based on molecular grounds. Morphologically, M. theobromae is similar to Verticillium albo-atrum (Hawksworth & Holliday 1970). The most distinctive feature of Musicillium species are their very long, dark brown, thick-walled conidiophores with pronounced verticils of phialides; the pigmentation is more consistent than that seen in V. albo-atrum, and it extends higher into the conidiophore. Although reports have mentioned an absence of moniliform resting structures in M. theobromae, we have seen gradually darkening chains of moniliform cells in all isolates studied. This, then, contrasts with the presence of initially pigmented resting structures that characterize V. albo-atrum. Musicillium theobromae does not form discrete chlamydospores. Its melanin pigmentation does not show a tendency to disappear during the degeneration of colonies, as is generally observed in the genus Verticillium.

Ecology and pathogenicity: This species was originally described from leaves of Theobroma cacao. Since then the species concept has generally been applied to the causal agent of cigar-end rot of banana (Meredith 1965, Hawksworth & Holliday 1970, Ershad 1972, Slabaugh 1994). This disease is widespread in banana-growing countries and is often caused by an association of M. theobromae and Deightoniella torulosa (Sydow) M.B. Ellis or the oomycete Trachysphaera fructigena Tabor & Bunting (particularly in Africa), or by one of these organisms occurring singly (Meredith 1965, Slabaugh 1994). Ershad (1972) and Jones & Stover (2000), however, reported that M. theobromae was the only organism isolated from cigar-end rot of banana in the western hemisphere, Iran, and Queensland. The species is a common colonizer of banana leaf trash and flowers. Conidia are disseminated in air currents and infect dying flower parts (Jones & Stover 2000). The pathogen first colonizes the perianth of banana saprotrophically and then attacks the fruit only in a late stage (Meredith 1965). In the complex crown-rot disease of boxed bananas, M. theobromae was also found rather regularly, but at low relative frequencies (Griffee 1976, Griffee & Burden 1976, Wallbridge 1981, Knight 1982). When inoculated into cut crown surfaces, the fungus penetrated some 5 mm in 5 days, but was outcompeted by Fusarium graminearum in mixed inoculations (Griffee 1976).

The species has also rarely been isolated from macerated litter of Heliconia mariae, a plant related to banana, in Costa Rica (Bills & Polishook 1994).

Distribution in Iran: Chabahar (Musa sapientum) and Mazandaran (Musa nana).

Reference

Zare, R., Gams, W., Starink-Willemse, M. and Summerbell, R.C. 2007. Gibellulopsis, a suitable genus for Verticillium nigrescens, and Musicillium, a new genus for V. theobromae. Nova Hedwigia 85(3–4): 463–489.

Addition: 
No
E-Record: 
No