SORI (sr) in markedly deformed leaves, sheaths, culms, and spikes, occur in long strips, at first lead-coloured and covered by epidermis, later the epidermis ruptures longitudinally and exposes reddish black, dusty spore balls.

SPORE BALLS (sb) subglobose, ovoid to irregular, (10.5-)13.5-20 x (12-)16-30(-40) µm diam, composed of 1-3(-5) spores surrounded by sterile cells.

SPORES (s) subglobose, ovoid, oblong to irregular, frequently with flattened or depressed sites, reddish brown, (8-)10-13.5(-16) x (11-)13-20(-22.5) µm.

Sterile cells (sc) subglobose, ovoid to irregular, pale yellow, smooth, 6-13 µm long.

GERMINATION. Spores germinate by formation of aseptate basidia, bearing (2-)4-6, apical, elongated basidiospores. Following meiosis and nuclear division taking place in the basidium, each basidiospore receives nucleus. After fusion of two compatible basidiospores, dikaryotic hypha infects the plant host (Vanky 1994).

PLANT HOST AND DISTRIBUTION. The plant host of U. occulta is Secale cereale L.

Urocystis occulta occurs in the whole world (Vanky 1994).

NOTES. Urocystis occulta causes leaf and stalk smut of rye.

Seedling infection is imitated by spores contaminating the grains (Smith et al. 1988).

REFERENCE

Vanky K. 1994. European smut fungi. Gustav Fischer Verlag. Stuttgard-Jena-New York, 570 pp.