Urediniospores are formed in structures called uredinia, which are produced by fungal mycelia on the cereal host 1–2 weeks after infection.
Since the urediniospores are produced on the cereal host and can infect the cereal host, it is possible for the infection to pass from one year's crop to the next without infecting the alternate host (barberry).
Note that this cycle consists simply of vegetative propagation - urediniospores infect one wheat plant, leading to the production of more urediniospores which then infect other wheat plants.
For instance many of them are ineffective against the Ug99 lineage.
Notably Ug99 has virulence against Sr31, which was effective against all previous stem rust races.
Thirty years later it received its name, Puccinia graminis, by Persoon, and in 1854 brothers Louis René and Charles Tulasne discovered the characteristic five-spore stage that is known to some stem rust species.
The brothers were also able to make a connection between the red (urediniospore) and black (teliospore) spores as different stages within the same organism, but the rest of the stages remained unknown.
There are multiple pathotypes (including QCC and MCC) affecting barley, within forma specialis tritici.
Infected plants produce fewer tillers and set fewer seed, and in cases of severe infection the plant may die.
Puccinia graminis produces all five of the spore types that are known for rust fungi.