Better Understanding of a Major Wheat Killer

Puccinia triticina, the fungus that causes the dreaded wheat leaf rust, is no easy foe. Leaf rust is the world's most widely distributed wheat disease. Reports indicated that infection can lead to yield loss of up to 20 percent. In Kansas, for instance, wheat producers lost some 50 million bushels to a leaf rust epidemic three years ago. Emerging strains of Puccinia are an increasing threat to wheat crops in Southern United States.

The fight against the fungus relies mainly on varietal resistance. More than 60 genes have been identified to combat Puccinia. But the pathogen is so genetically diverse and quick to adapt that most wheat resistance genes prove ineffective within a few years. Thanks to the effort of researchers at the US Department of Agriculture's Agricultural Research Service (ARS), scientists are now armed with information to combat the fungus. James Kolmer and colleagues has completed a comprehensive genetic analysis of emerging strains of P. triticina collected in a recent survey of North America's major wheat-producing areas. According to them, the fungus comes in five genetically distinct groups in the US, with two widely distributed groups accounting for 90 percent of the total population. The genetic groups were found to differ in their ability to overcome resistance genes.

The findings will help scientists monitor the shifts in Puccinia virulence and unravel clues about its migration patterns.

Read the complete article at http://www.ars.usda.gov/is/pr/2009/090505.htm