Anthracocystis rhytachnes-rottboellioidis (Vánky) T. Denchev & Denchev 2016

Denchev, Teodor T. & Denchev, Cvetomir M., 2016, Anthracocystis rhytachnes-rottboellioidis and A. urelytri, two new combinations of smut fungi (Ustilaginales) from Africa, Phytotaxa 253 (3), pp. 227-231 : 227-229

Anthracocystis rhytachnes-rottboellioidis (Vánky) T. Denchev & Denchev , comb. nov. ( Figs 1 –7)

Index Fungorum number: IF551929

Basionym: — Sporisorium rhytachnes-rottboellioidis Vánky, Mycotaxon 85: 54, 2003.

Type: — On Rhytachne rottboellioides , UGANDA, Masaka Distr., 13 km E of Masaka, on Bukakata road, alt. c. 1140 m, 17 November 2002, C., T. & K. Vánky ( H. U. V. 19 994, holotype (!); isotypes MHU, BPI 842 312, IMI, K) .

Sori in all ovaries of an infected plant, cylindric or bacilliform, 3–6 × 0.4–0.7 mm, partly concealed by the floral envelopes; covered by a thin, yellow-brown or grayish brown peridium, often with remnants of stigmas on its tip. The peridium ruptures irregularly, exposing the pulverulent, blackish brown mass of spore balls and spores, surrounding a single, flagelliform columella. The columella not exceeding the length of the sorus, slightly tapering, not ramifying, with shallow longitudinal furrows.Anthers often present around the sori. Spore balls subglobose, broadly ellipsoidal, irregular or ellipsoidal, sometimes elongated, 25–55(–65) × 20–35(–45) μm, dark reddish brown, composed of 15 to tens, easily separating spores. Sterile cells absent. Spores slightly dimorphic, variable in shape, polyhedral, irregular, subglobose, ellipsoidal, irregularly elongated or broadly ellipsoidal, (7–)7.5–12(–13.5) × (6–)6.5–8.5(–9.5) (9.4 ± 1.2 × 7.6 ± 0.6) μm (n = 200); wall slightly uneven, 0.5–1.0 μm thick, often with one or few thinner areas in which the wall is collapsed and with lighter colour. Outer spores medium yellow-brown to medium reddish brown, minutely verruculose, spore profile smooth or nearly so; inner spores light yellow-brown, smooth. In SEM minutely verruculose, warts up to 0.2 μm high.

Additional specimen examined: —On Rhytachne rottboellioides Desv. ex Ham. : Liberia: Yéképa, Mt. Nimba, January 1965, leg. J. G. Adam 23 893 ( B 10 0506789) (Fig. 7). It is a new record for Liberia.

Known host and distribution: —On Poaceae : Rhytachne rottboellioides ; Africa ( Uganda, Liberia; Fig. 8) ( Vánky 2003, Vánky et al. 2011).

Comments: —The description given above is based on the type specimen ( Figs 1–6 ).

Rhytachne rottboellioides is distributed in Tropical and South Africa and Madagascar, and is naturalized in America (from Mexico to Brazil) ( Clayton et al. 2015, Poilecot 2015). We expect that A. rhytachnes-rottboellioidis is more widely distributed in Africa.

Anthracocystis rhytachnes-rottboellioidis differs from A. rhytachnes by developing sori in the ovaries of the infected plant (while the sori of A. rhytachnes destroy the inflorescence), and having smaller spores, (7–)7.5–12(–13.5) μm long, versus 11–15(–16) μm long for A. rhytachnes .

Anthracocystis rhytachnes-rottboellioidis differs from Sporisorium urelytri by developing sori in the ovaries of the infected plant (while the sori of S. urelytri destroy sessile and pedicellate spikelets), and having smaller spores, (7–)7.5–12 (–13.5) (9.4 ± 1.2) μm long versus (10–)10.5–14(–15.5) (12.4 ± 0.9) μm long for S. urelytri .

Based on the morphological characters that separate Anthracocystis from Sporisorium (cf. McTaggart et al. 2012b), Sporisorium urelytri should be transferred to Anthracocystis . A new combination is proposed here.

Figures

FIGURES 1–6. Anthracocystis rhytachnes-rottboellioidis on Rhytachne rottboellioides from Uganda (holotype, H.U.V. 19 994). 1, 2. Habit. Arrowheads in Fig. 1 indicate immature sori with remnants of stigmas. Arrows in Fig. 2 show single, flagelliform columellae. 3, 4. Spore balls and spores in LM. Arrow in Fig. 4 indicates inner spores. 5, 6. Spore balls in SEM. Scale bars: 1, 2 = 0.5 cm, 3–5 = 10 μm, 6 = 2 μm. FIGURE 7. Anthracocystis rhytachnes-rottboellioidis on Rhytachne rottboellioides from Liberia—spore balls in SEM (B 10 0506789). Scale bar = 10 μm. FIGURE 8. Geographic distribution of Anthracocystis rhytachnes-rottboellioidis (red circles) (generated with SimpleMappr, Shorthouse 2010). Scale bar = 500 km.