A smut fungus of Gagea spp. (G. lutea and G.bohemica in GB&I), visible as lesions/pustules on leaves and stems, up to 10 mm in length, that later split to release a dark black-brown powdery mass of spores.
Sori 1-5(-10) mm long, dark blackish-olive-brown ellipsoidal or fusiform pustules on leaves of Gagea lutea in GB&I, initially covered by the epidermis, but then rupturing longitudinally to expose a blackish brown, powdery spore mass. Spores variable in shape and size; subglobose, ovoid, irregular, subpolyhedral or elongate; sometimes with an acute tip or short pedicel; 10.5-19(-24) µm x 9.5-15 µm, yellowish to reddish brown; wall 0.5-1.5 µm thick, apparently one-layered, nearly to finely smooth, moderately densely punctate-verruculose, but dots not affecting the spore profile. Sterile cells few, solitary or in groups of 2-4, subglobose, ellipsoidal, slightly irregular, rarely elongated, collapsed in old specimens, 11-20 µm long, usually of the same colour as the spores; wall 1.5-3(-4) µm thick, one-layered, smooth (but rough under high magnification SEM). Infection systemic, appearing on the same host plant year after year.
Description based on Vánky (2013). For external images see the Bioimages website.