SORI (sr) in blistery swellings or galls of a different size, formed on infected stems, leaves, or inflorescences. When young, the swellings or galls are covered by a thin, pale greenish to greyish-silvery, smooth membrane that later becomes brown, ruptures, and exposes the medium to dark brown spore conglomeration.

SPORES (s) globose to subglobose, ovoid, rarely irregular, pale oliviaceous brown, 7-11 x 7-13 µm, with a wall ca. 0.5 µm thick, ornamented with fine spines.

GERMINATION. Spores germinate by formation of a four-celled basidium, laterally and terminally bearing basidiospores.

The basidiospores germinate and penetrate the plant host directly. All young meristematic tissues are susceptible. A limited amount of haploid hyphae develop after infection. However, after conjugation of compatible haploid hyphae, only the dikaryotic, secondary hyphae continue the infection which terminates in the production of spores (Barnes 1979).

PLANT HOST AND DISTRIBUTION. Ustilago maydis affects different plant species of the genera Euchlaena and Zea (Poaceae; Vanky 1994).

The fungus occurs world-wide (Vanky 1994).

NOTES. Ustilago maydis is uniquely adapted to exist as a saprotroph. Its spores persist in the soils and refuse.

REFERENCES

Barnes E. H. 1979. Atlas and manual of plant pathology. Plenum Press. New York and London.

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