(1921) Puccinia coronata is a plant pathogen and causal agent of oat and barley crown rust.
[1] 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.
[2] Crops with resistant phenotypes are often released, but within a few years virulent races have arisen and P. coronata can infect them.
[5] In addition, if plants are badly infected, they become more sensitive to drought conditions which can cause death.
[6] Teliospores on barley straw and residue of susceptible grasses left in the field germinate in the spring and produce basidiospores that infect Rhamnus cathartica.
The primary infections, which can occur as early as the three leaf stage of barley in the spring, develop into uredinia.
Urediniospores produced in the uredinia repeat the infection process, and the fungus undergoes several cycles of reproduction on barley during the growing season.
The fungus readily forms telia on these hosts, which serve as a reservoir of overwintering teliospores.
Uredinial/telial stages also occur on a wide range of grass species (Poaceae) in the genera Agrostis, Arrhenatherum, Bromus, Calamagrostis, Elymus, Festuca, Glyceria, Holcus, Hordeum, Lolium, Poa and Schedonorus etc.
Recent molecular studies suggest that with high intraspecific genetic variation, Puccinia coronata harbors multiple phylogenetic lineages.
[7][8] Sources of resistance to crown rust have been identified in barley germplasm from diverse regions, but most malting barley cultivars currently grown in the northern Great Plains of North America are susceptible to crown rust.
[1] Typically P. coronata can overcome resistant gene within five years, making it difficult for researchers to control its damaging effects on the oat production industry.
In lab studies A. barbata has done remarkably well in conferring resistance to various strains of crown rust.
The main goal of the researchers is to not only confer resistance to crown rust, but also to develop oat varieties with additional desirable traits such as high yield and drought tolerance.
[9] Research into P. coronata on A. sativa/oat crown rust has been foundational to the understanding and definition of "tolerance" in phytopathology.
Although they noted that most interest was in breeding for hypersensitive responses, they located, differentiated, quantified, and defined "tolerance" for the first time in cultivars prevalent in the United States.