''Puccinia coronata'' is a
plant pathogen
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...
and causal agent of oat and barley crown rust. The pathogen occurs worldwide, infecting both wild and cultivated oats. Crown
rust
Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO( ...
poses a threat to
barley production, because the first infections in
barley
Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...
occur early in the season from local
inoculum.
Crown rusts have evolved many different physiological races within different species in response to host resistance. Each pathogenic race can attack a specific line of plants within the species typical host. For example, there are over 290 races of ''P. coronata''. Crops with resistant phenotypes are often released, but within a few years virulent races have arisen and ''P. coronata'' can infect them.
Symptoms
Uredinia are linear, light orange, and occur mostly on the leaf blades but occasionally occur also on
leaf sheath
A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...
s,
peduncles
and
awns. Extensive
chlorosis
In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...
is often associated with the