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What is Puccinia graminis?

puccinia graminis

Puccinia graminis, the causal agent of stem rust, has caused serious disease of small cereal grains (wheat, barley, oat, and rye) worldwide. P. graminis is the first sequenced representative of the rust fungi (Uredinales), which are obligate plant pathogens. The rust fungi comprise more than 7000 species and are one of the most destructive groups of plant pathogens. Stem rust of wheat has been a serious problem wherever wheat is grown and has caused major epidemics in North America (1). In 1999, a new highly virulent race TTKS (Ug99) of P. graminis was identified in Uganda, and since then has spread, causing a widening epidemic in Kenya and Ethiopia (2). Due to its devastating ability to cause epidemics, P. graminis was developed as a biological warfare agent during the Cold War (3) and is now considered one of the most important potential agricultural bio-terrorism threats to U. S. agriculture (4).

Puccinia graminis is a heteroecious rust fungus with five spore stages and two hosts (5). The asexual stage (uredinial) infects cereal and grass hosts and is the economically important form of the pathogen. The sexual stage begins in the resting spore (teliospore) on leaves and stalks of the gramineous host. The sexual stage is completed on the aecial (alternate) host, barberry. P. graminis, as a species, has a broad host range that includes more than 300 species of cereals and grasses. Wheat stem rust, P. graminis f.sp. tritici is known to naturally infect 28 species belonging to eight genera, including wheat, barley and rye.

References

  1. A. P. Roelfs, in The Cereal Rusts Vol II. Diseases, Distribution, Epidemiology, and Control A. P. Roelfs, W. R. Bushnell, Eds. (Academic Press, Orlando, 1985) pp. 3-37.
  2. www.globalrust.org
  3. R. F. Line, C. S. Griffith, in Stem Rust of Wheat, From Ancient Enemy to Modern Foe P. D. Peterson, Ed. (APS Press, St. Paul, 2001) pp. 83-118.
  4. Public Health Security and Bio-terrorism Preparedness and Response Act (2002).
  5. K. J. Leonard, L. J. Szabo. 2005. Pathogen profile: Stem rust of small grains and grasses caused by Puccinia graminis. Molecular Plant Pathology 6:99-111.