Puccinia
Occurrence Puccinia is large genus. It has several obligatory parasitic species. tritici is a parasite of wheat. It completes its life cycle in two different hosts: wheat and barely. Thus it is hetcrocious rust. It infects the stem of wheat and causes black or stem rust. Life cycle The life cycle of Puccina is divided into five stages on the basis of nature of spores. These stages are: I. Uredinial stage: Its ;nfection appears in March. Reddish brown pustules or soni appear on the stem of wheat. These son are called uredosori. Uredosori contains numerous uredospores. These are globose and thick walled spores. These spores borne on long stalks. Each uredospore has two nuclei. It has one germ pore in its wall. The uredospore detached. Wir.1 carries them to other healthy plants. Uredospores germinate on new wheat plants. They develop one or more germ tubes. The germ tubc reaches at the tip of stomata of host leaf. The tip of germ tube swells form v...