Diseases Which Challenge Global Wheat Production - The Cereal Rusts

Authors: Kolmer, James; Chen, Xianming; Jin, Yue

Submitted to: Wheat: Science and Trade
Publication Type: Book / Chapter
Publication Acceptance Date: 6/15/2008
Publication Date: 6/15/2009
Citation: Kolmer, J.A., Chen, X., Jin, Y. 2009. Diseases Which Challenge Global Wheat Production - The Cereal Rusts. In: Carver, Brett F., editor. Wheat: Science and Trade. Hoboken, NJ: Wiley Press. p. 89-124.

Interpretive Summary: Wheat is attacked by three types of rust fungi. The rust Puccinia graminis causes the stem rust disease of wheat; the rust Puccinia triticina causes leaf rust disease of wheat, and Puccinia striiformis causes stripe rust of wheat. All three rust diseases of wheat occur in the United States and cause millions of dollars annually in yield losses in wheat. The rust pathogens of wheat are genetically diverse with many different types of biologic forms that differ in ability to attack rust resistance genes in wheat. The rusts are spread throughout the wheat producing regions by means of infectious spores that are carried in the winds and are deposited on wheat crops in rainfall. Many different genes in wheat provide resistance to the wheat rusts, however the rusts continually mutate to new biologic forms that regain ability to attack wheat cultivars. Genetic resistance in wheat is the most economical means of reducing yield losses due to rust. Some genes in wheat provide resistance to all known biologic forms of rust and have been the most useful types of resistance.

Technical Abstract: The rusts of wheat are common and widespread diseases in the US and throughout the world. Wheat rusts have been important throughout the history of wheat cultivation and are currently important diseases that are responsible for regularly occurring yield losses in wheat. The wheat rust fungi are obligate parasites that require living plant tissue in order to infect and reproduce by the clonal production of dikaryotic urediniospores. The wheat rust fungi are wind dispersed across long distances in the atmosphere by urediniospores that infect wheat plants with proper temperature and moisture conditions. New races of wheat rusts have recently emerged in the US and world-wide, complicating efforts to develop rust resistance wheat cultivars. Wheat leaf rust, caused by the rust fungus Puccinia triticina is the most common and widespread rust of wheat in the US and world-wide. Leaf rust can be found throughout most of the wheat growing regions of the US. A large population of P. triticina overwinters annually in the southern US in which mutations regularly occur, leading to races with new virulences. Although the alternate host is not present in North America, P. triticina is highly diverse for virulence as many races are found annually in the US. Genes Lr34 and Lr46 have provided durable resistance in wheat cultivars to leaf rust. Wheat stripe rust caused by Puccinia striiformis f. sp. tritici is an important disease in areas where wheat grows and matures in cool temperatures. Wheat stripe rust is common and widespread in the Pacific Northwest, California, and the Gulf Coast. In recent years wheat stripe rust has increased in occurrence in the southern-mid Great Plains and the southeastern states. Gene Yr18 and high temperature adult plant resistance genes have provided durable resistance in wheat to stripe rust. Wheat stem rust caused by Puccinia graminis f. sp. tritici is potentially a highly destructive disease of wheat. Wheat stem rust occurs in continental areas where wheat matures in hot weather. Wheat stem rust overwinters in south Texas and in the Gulf Coast area, and the urediniospores are wind dispersed throughout the Great Plains and southeastern states. The alternate host, Berberis vulgare has largely been eradicated from North America, reducing the number of stem rust races. Major epidemics of wheat stem rust occurred periodically from 1900-1954 in North America, causing severe yield losses. The widespread cultivation of stem rust resistant winter wheat and spring wheat since the 1950s has greatly reduced the population size of P. graminis f. sp. tritici, resulting in many fewer stem rust infections on an annual basis. Wheat cultivars with the gene Sr2 have had durable resistance to stem rust.