Puccinia striiformis on wheat. Image by the Agricultural Research Institute.

The Puccinia striiformis PST78 genome was not sequenced at JGI and was imported from the Broad Institute. Below is the description of this lineage written by the Broad Instutute.

Puccinia striiformis Westend. f. sp. tritici Eriks. (Pst) causes stripe rust, an important disease of wheat worldwide. Other formae speciales of P. striiformis cause stripe rust of barley or other grasses. Stripe rust is most prevalent in cool regions of the world where most of the world's wheat and barley are produced. Because stripe rust is favored by low temperatures, the disease occurs earlier in the growing season than leaf and stem rusts, and therefore, has potential to cause more damage. Pst has become increasingly important in the U.S. where epidemics since 2000 have caused yield losses of over 246 million bushels in spite of millions of dollars spent on fungicides.

Unlike P. triticina and P. graminis, the Pst lifecycle consists of uredinial, telial, and basidial stages; pycnial and aecial stageshave not been found. The fungus produces one-celled, dikaryotic (n+n) urediniospores-containing yellow to orange-colored uredia on leaves, leaf sheaths, and glumes of wheat or other grasses. Urediniospores are airborne and infect wheat and grasses, and produce new urediniospores. The growth and reproduction of the fungus within the plant tissue destroys leaf area and utilizes water and nutrients from the host plant, which inhibits growth and desiccates the plant, reducing grain yield and quality. Later in the season, black telia may form along uredia. Teliospores produced in telia are diploid (2n) and two-celled, which can germinate to form one-celled and haploid (n) basidiospores. Because Pst has no known alternate hosts, basidiospores have no known function in the pathogen lifecycle.

Pst populations change their virulence amazingly rapidly by mechanisms that are largely unknown. Pst is recalcitrant to classical genetic manipulations because it is an obligate biotroph without a known sexual stage.