Rusts are
fungal plant pathogen
Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like orga ...
s of the order Pucciniales (previously known as Uredinales) causing
plant fungal disease
Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like orga ...
s.
An estimated 168 rust
genera
Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
and approximately 7,000 species, more than half of which belong to the genus ''
Puccinia
''Puccinia'' is a genus of fungi. All species in this genus are obligate plant pathogens and are known as rusts. The genus contains about 4000 species.
The genus name of ''Puccinia'' is in honour of Tommaso Puccini (died 1735), who was an Ital ...
'', are currently accepted.
[
] Rust fungi are highly specialized plant pathogens with several unique features. Taken as a group, rust fungi are diverse and affect many kinds of plants. However, each species has a range of hosts and cannot be transmitted to non-host plants. In addition, most rust fungi cannot be
grown easily in pure culture.
Most species of rust fungi are able to
infect two different plant hosts in different stages of their life cycle, and may produce up to five
morphologically and
cytologically distinct
spore
In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...
-producing structures viz.,
spermogonia,
aecia,