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Puccinia merrilliana (Syd. & P. Syd.) McTaggart & R.G. Shivas

Description
Uredinia on lower leaf surface, subepidermal, erumpent, round to ellipsoidal, 0.5‒1 mm, reddish brown to brown, peridium present.

Urediniospores globose, subglobose or ovoid, apex obtuse, yellowish brown, 22‒26 × 20‒23 μm; wall 2‒4 μm thick, thicker towards the base, finely echinulate, with (1-)2 supraequatorial germ pores.

Hosts
Host family: Convolvulaceae
Host species: Operculina aequisepala

Distribution
WA

Comments
Puccinia merrilliana is only known from its uredinial stage (Shivas 1989 as Uredo operculinae). Puccinia merrilliana has (1-2) germ pores, which differentiates it from P. operculinae with 3-4 germ pores (McTaggart and Shivas 2017). This rust is widespread across northern Australia.

Highslide JS
Puccinia merrilliana on Operculina brownii - BRIP 60950.
Highslide JS
Puccinia merrilliana on Operculina brownii - BRIP 56913.
Scale bar = 1 cm.
Highslide JS
Urediniospores of Puccinia merrilliana on Operculina brownii - BRIP 56913.
Scale bar = 10 µm.