untitled

Uredospores

(dikaryotic)

Aeciospores

Spermogonia
Spermatia

Basidiospores

haploid stage

Meiosis

Nuclear fusion

Teliospores

Repeatedly

infect wheat

Wheat

Barberry

Fig. 14.22Outline of the disease cycle of Puccinia

graminis, which alternates between phases of

growth on wheat and on barberry.

Fig. 14.23Black stem rust of wheat caused by Puccinia graminis. (a) Elongated stem lesions bearing uredospores.
(b) Stained section of a wheat stem with a pustule of uredospores breaking though the plant epidermis. (c) Section
of a pustule with teliospores.