Yelsemia arthropodii J. Walker

Description

Sori in the stems, leaf axils and seeds, swollen, ±distorting the host organs, leaden to greyish black, 6–8 (–20) mm long, 3–5 mm wide, bursting at maturity and exposing a black granular-powdery mass of spores. Infection in seedling stage systemic, resulting in production of several flowers per node and elongation of sterile bracts and floral pedicels.

Spores solitary, globose, subglobose to ovoid, 20–25 × 16–22 µm, dark blackish brown, with 2 oppositely situated hyaline to pale brown polar caps (a result of the localised separation of the inner and outer layers of the spore wall), the space between them being filled with a homogenous transparent substance; wall of the equatorial part 2.0–2.5 µm thick, finely and densely verruculose, with 1 (or 2 opposite) small (c. 2 µm diam.) circular hilar scars (where the sporogenous hyphae were attached); wall beneath the polar caps thinner, paler, smooth. Outer wall at the polar areas thin, pale yellowish brown, minutely verruculose.

Spore germination through the polar caps, resulting in 1 or 2 aerial holobasidia, from very short to 50 µm long, 4–6 µm wide at the base, 9–10 µm wide at the apex, sometimes with 2 branches near the apex. Mature basidia usually with 1–3 retraction septae and 2–6 apical broadly fusiform hyaline basidiospores measuring 25–50 × 4–6 µm, at first unicellular, later with 1–3 (–4) transverse septa and germinating from 1 or several cells by 1 or 2 hyphae, often forming anastomoses with neighbouring basidial cells to produce dikaryotic infection hyphae.

Hosts
   
Host family: Anthericaceae
   
Host species: Arthropodium curvipes S.Moore
Arthropodium minus R.Br.

Distribution

States & Territories: NSW, WA

Comments

Yelsemia arthropodii is known from the monocotyledonous host Arthropodium at two localities, both arid areas on opposite sides of Australia. The other two species of Yelsemia in Australia occur on dicotyledonous hosts in the arid tropics of northern W.A. and N.T.