LEAF SPOTS brownish, rectangular or elliptical, up to 8 x 3 mm, with centers turning greenish-grey to straw-coloured, surrounded by a diffuse, reddish brown margin, frequently confluent and forming extensive, irregular, yellowish lesions.

PYCNIDIA (p) scattered, or usually more numerous and crowded on the lesions, dull brown to blackish at maturity, usually conspicuous, epiphyllous or amphigenous, immersed or slightly erumpent, subepidermal, separate, unilocular, subglobose to ellipsoidal, 80-220 µm wide, up to 150 µm high, with a subcircular to elliptical, slightly papillate ostiolum, 10-34 µm diam, usually opening into a stoma.

Wall (w) 6-16 µm thick, composed of 3-7 layers of cells; cells of the outer layer thick-walled, dark brown, more or less flattened, merging with inner layers of smaller, relatively thin-walled, angular, nearly isodiametric, subhyaline cells.

Conidiogenous cells (cc) phialidic, hyaline, sessile or terminal and intercalary on short, septate conidiophores; sessile and terminal conidiogenous cells lageniform, ampulliform, or conoidal, 6-15 x 2.3-5.4 µm, producing conidia at the tip from a narrow neck; intercalary conidiogenous cells doliiform to short cylindrical, producing conidia laterally immediately below transverse septa.

 

CONIDIA (c) hyaline, narrowly cylindrical or subulate, flexuous to nearly straight, slightly attenuate toward the apex, usually 3-septate at maturity, 28-85 x 1.5-2.2 µm; apex more or less acutely rounded, base obtuse or truncate.

PLANT HOST AND DISTRIBUTION. Septoria tritici affects Triticum aestivum L. and T. durum Desf.

This fungus has a worldwide distribution (Teterewnikowa-Babajan 1987).

NOTES. Septoria tritici causes "speckled leaf blotch" of wheat. The disease is favoured by cool weather and prolonged precipitation. Septoria tritici can be distinguished readily from Stagonospora nodorum (Berk.) Castell. & Germaño, another septorioid species commonly affecting Triticum, in having narrower, more elongate, and flexuous conidia.

The teleomorph of S. tritici is Mycosphaerella graminicola (Fuckel) Schroter.

REFERENCE

Teterewnikowa-Babajan D. N. 1987. Griby roda Septoria w SSSR. Izdatelstwo An Armianskoj SSR, 480 pp.