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Uromycladium robinsonii McAlpine

Description
Spermogonia on phyllode spots, amphigenous, subepidermal, erumpent, hemispherical, ca. 100 µm wide × 50 µm high.

Spermatia subglobose to cylindrical, hyaline, 3‒6 × 2‒4 µm.

Uredinia on phyllodes, amphigenous, bordering elongated spots up to 1 cm long, confluent, erumpent, bullate, linear, brown.

Urediniospores fusiform, narrowly ellipsoidal, often asymetrical or slightly curved, apex obtuse, yellowish brown, 30‒58 × 16-22 µm; wall 1.5‒2.5 µm thick, densely covered in conical warts up to 2 µm high and 1.5 µm across base with acute or rounded apices, with 3‒5 equatorial or subequatorial germ pores, apex up to 6 µm thick.

Telia indistinguishable from uredinia, formed around spermogonia or scattered on phyllodes, up to 0.5 mm long, confluent.

Teliospores depressed globose or subglobose, apex obtuse, yellowish brown, 21‒27 × 24‒30 µm; wall 2‒5 µm thick, thickened at apex up to 5 µm, 1 conspicuous germ pore present, smooth, formed on septate pedicels that bear one or two vesicles; vesicles globose or broadly ellipsoidal, 15‒25 µm diam., hyaline, thin-walled.

Hosts
Host family: Fabaceae
Host species: Acacia implexa
Acacia maidenii
Acacia melanoxylon

Distribution
NSW, NT, QLD, VIC, WA

Comments
Uromycladium robinsonii was first described from Acacia melanoxylon by McAlpine (1906). The records of this rust on A. maidenii and A. implexa warrant closer scrutiny as each is vegetatively very similar, and sometimes confused with A. melanoxylon. U. robinsonii and U. simplex are readily differentiated from other Acacia rusts by having septate pedicels bearing one teliospore together with a hyaline vesicle. U. robinsonii has coarsely warted urediniospores, unlike U. simplex, which has finely warted urediniospores.

Highslide JS
Uromycladium robinsonii on Acacia implexa - BRIP 53583.
Highslide JS
Spermogonia and aecia of Uromycladium robinsonii on Acacia implexa - BRIP 53583.
Scale bar = 1 mm.
Highslide JS
Telia of Uromycladium robinsonii on Acacia melanoxylon - BRIP 30440.
Scale bar = 5 mm.
Highslide JS
Spermogonium of Uromycladium robinsonii on Acacia implexa - BRIP 53583.
Scale bar = 100 µm.
Highslide JS
Urediniospores of Uromycladium robinsonii on Acacia implexa - BRIP 53583.
Scale bar = 10 µm.
Highslide JS
Teliospores and vesicles of Uromycladium robinsonii on Acacia implexa - BRIP 31943.
Scale bar = 10 µm.
Highslide JS
Teliospore with attached vesicle of Uromycladium robinsonii on Acacia melanoxylon - BRIP 30440.
Scale bar = 10 µm.