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Tranzschelia discolor (Fuckel) Tranzschel & M.A. Litv.

Description
Uredinia on lower leaf surface, scattered or confluent, corresponding upper leaf surface exhibits small yellowish irregular spots with diffuse purplish haloes mostly less than 2 mm diam., subepidermal, erumpent, round, 200‒500 µm diam., reddish brown; paraphyses intrasoral, capitate, subhyaline, pale yellow to yellowish brown, 30‒60 µm long; wall 0.5 µm thick at the sides, up to 3.0 µm thick at apex.

Urediniospores cylindrical, ellipsoidal, obovoid or oval, subhyaline to yellowish brown, 25‒42 × 12‒22 µm; wall 1‒2 µm thick at sides, apex 4‒7 µm thick, densely echinulate at the base becoming smooth at the apex.

Telia on lower leaf surface, subcuticular, erumpent, dome-shaped, reddish brown.

Teliospores ellipsoidal, apex rounded, 2 celled, reddish brown, 31‒38 µm long, upper cell 18‒24 wide, globose with a truncate base; lower cell 16‒20 wide, doliiform.; wall 2.0‒4.5 µm thick, thickened at apex, echinulate, upper cell covered in dense conical warts or spines up to 2 µm high, lower cell less densely verrucose to smooth and lighter in the lower part; single pedicel up to 35 µm long.

Hosts
Host family: Rosaceae
Host species: Prunus domestica
Prunus dulcis

Distribution
QLD, SA

Comments
Tryon (1889) first reported Tranzschelia discolor (as Puccinia pruni-spinosae) on apricot (Prunus armeniaca)and European plum (P. domestica) from Queensland. This rust affects other cultivated species of stone fruits, including peach and nectarine (P. persica), almond (P. dulcis) and Japanese plum (P. salicina). Tranzschelia discolour is reportedly macrocyclic and heteroecious, producing aecia on Anemone, Hepatica and Thalictrum. The aecial stage has not been found in Australia and does not appear to play a role in the epidemiology of this rust.

Highslide JS
Tranzschelia discolor on Prunus dulcis - BRIP 53349.
Scale bar = 5 mm.
Highslide JS
Tranzschelia discolor on Prunus domestica - BRIP 57627.
Scale bar = 1 mm.
Highslide JS
Paraphyses of Tranzschelia discolor on Prunus dulcis - BRIP 53349.
Scale bar = 10 µm.
Highslide JS
Urediniospores of Tranzschelia discolor on Prunus dulcis - BRIP 53349.
Scale bar = 10 µm.
Highslide JS
Teliospores of Tranzschelia discolor on Prunus domestica - BRIP 57627.
Scale bar = 10 µm.