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The fungal ancestors of stem rust have infected grasses for millions of years and wheat crops for as long as they have been grown. [7] According to Jim Peterson, professor of wheat breeding and genetics at Oregon State University, "Stem rust destroyed more than 20% of U.S. wheat crops several times between 1917 and 1935, and losses reached 9% twice in the 1950s," with the last U.S. outbreak in ...
Puccinia graminis is a macrocyclic heteroecious fungus that causes wheat stem rust disease. [citation needed] The sexual stage in this fungus occurs on the alternate host – barberry – and not wheat. The durable spore type produced on the alternate host allows the disease to persist in wheat even in more inhospitable environments.
Wheat rusts include three types of Pucciniae: P. triticina , wheat leaf rust , leaf rust, wheat brown rust, or brown rust P. graminis , stem rust , wheat stem rust, barley stem rust, or black rust
Another online database of cereal rust resistance genes is available at . Unfortunately, less is known about rye and particularly triticale R-genes. Many R-genes have been transferred to wheat from its wild relatives, and appear in such papers and catalogues, thus making them available for triticale breeding.
Other cereal rust fungi have macrocyclic, heteroecious life cycles, involving five spore stages and two phylogenetically unrelated hosts. P. striiformis was thought to be microcyclic for centuries until 2009, when a team of scientists at the USDA-ARS Cereal Disease Lab led by Yue Jin confirmed that barberry (Berberis and Mahonia spp.) is an alternate host. [3]
Ug99 is a lineage of wheat stem rust (Puccinia graminis f. sp. tritici), which is present in wheat fields in several countries in Africa and the Middle East and is predicted to spread rapidly through these regions and possibly further afield, potentially causing a wheat production disaster that would affect food security worldwide. [1]
Wheat stem rust is an example. By convention, the stages and spore states are numbered by Roman numerals . Typically, basidiospores infect host one, also known as the alternate or sexual host, and the mycelium forms pycnidia , which are miniature, flask-shaped, hollow, submicroscopic bodies embedded in the host tissue (such as a leaf).
Wheat may suffer from the attack of insects at the root; from blight, which primarily affects the leaf or straw, and ultimately deprives the grain of sufficient nourishment; from mildew on the ear; and from gum of different shades, which lodges on the chaff or cups in which the grain is deposited.