Roberge ex Desm. f. sp. tritici
SPERMOGONIA (s) 80-145 µm diam, usually on the upper leaf surface, within yellow to red brown spots, up to 15 mm diam.
Peridium cup-shaped or cylindrical, 0.2-0.6 mm diam, up to 0.5 mm high, white to yellowish, with an irregularly crenate or ragged edge.
Peridial cells with an outer wall, 6-7 µm thick, and an inner wall, 2-3 µm thick, both warty.
AECIOSPORES (ae) flattened, globose to ellipsoidal, 16-26 x 16-20 µm.
Wall colourless, up to 1 µm thick, densely covered with small warts.
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UREDINIA (u) mainly on the upper leaf surface, ellipsoidal, up to 1 µm long, rusty-brown, dusty, usually partly covered with a cracked epidermis, frequently occur on the whole leaf that becomes yellow to brown.
UREDINIOSPORES (ue) globose to ellipsoidal, 22-30 x 18-23 µm.
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Wall brown yellowish, 1.5-2.0 µm thick, ornamented with spines spaced 2-3 µm apart.
Germ pores (7-)8-10, dispersed.
TELIA (t) on the under leaf surface, ovoid or prolate, up to 1 mm long, frequently connected with each other to form long conglomerations, black, permanently covered with epidermis.
TELIOSPORES (te) clavate to irregularly ellipsoidal, asymmetrically rounded or flattened at the top, slightly narrowed at the transverse wall, 33-45 x 15-21 µm.
Wall yellowish, thin aside, yellow brown, up to 3-5 µm thick at the top.
Germ pores (gp) indistinct.
Pedicel yellowish, with a yellow brown, thickened up to 2-4 µm wall at spore base, persistent.
PLANT HOST AND DISTRIBUTION. Spermogonia and aecia of P. recondita f. sp. tritici develop on different plant species of the genus Thalictrum (Majewski 1979). Uredinia and telia form on different species of the genus Triticum. Puccinia recondita f. sp. tritici has a worldwide distribution (Smith et al. 1988).
NOTES. Puccinia recondita f. sp. tritici causes the severe brown rust of wheat.
The aecial stage is unimportant epidemiologically and the fungus mainly overwinters in the uredinial stage (Smith et al. 1988). This can survive relatively low temperatures. Uredinial mycelium survives on autumn-sown wheat under extreme conditions. In regions of mild winters, infections may initiate spores germinating at a temperature range of 5-25oC, although the optimum temperature is between 10-20oC. The life cycle time under favourable conditions (warm and moist weather) is approximately 7-10 days.
REFERENCES
Majewski T. 1979. Grzyby (Mycota) XI. Podstawczaki (Basidiomycetes), Rdzawnikowce (Uredinales) II. Warszawa-Kraków, 462 pp.
Smith I. M., Dunez J., Lelliott R. A., Phillips D. H., Archer S. A. 1988. European handbook of plant diseases. Blackwell Scientific Publications.