Researchers use genetics to identify costly fungus

 

WSU researchers are turning to genetic “fingerprinting” to reassure China that grass seed it imports from the Pacific Northwest is free from a fungal contaminant.

Nearly 15 million pounds of grass seed valued at $9 million was exported from the United States to China in 2005. But Chinese quarantine officials have said that 20-30 percent of seed exports from the Pacific Northwest are “highly contaminated” with smut fungi.

China and other countries ban imports of contaminated seed, so keeping smuts in check is economically important for U.S. growers, including those who raise Kentucky bluegrass in the Pacific Northwest.

Smut spores from cultivated fine fescue, a smut Carris and her colleagues described as a new species in 2007.

Smuts infect grasses, including cereal crops like wheat and corn. Infected plants are often stunted, though the reduced size is not noticeable until maturity. If not detected before harvest, millions of fungal spores are released, contaminating healthy kernels or landing on the soil to infect the next year’s crop.

 

“Identification of smut fungi found in grass seed shipments is difficult, as many closely related species have morphologically similar spores,” said Lori Carris, WSU associate professor of plant pathology.

 

 

 

Wheat heavily contaminated with smut from cheatgrass. Cheatgrass seed and pieces of smut-infected cheatgrass seed are visible among the grains of wheat.

In fact, the species of smut Chinese scientists say is infecting imported seed isn’t known to infect bluegrass. The infection could be a contaminant from some other source – for example, weedy grasses – or perhaps a new species.

Carris and colleagues are using genetic fingerprinting tools to distinguish one species of smut from another. Correctly identifying the infectious agent is a necessary step in controlling the fungus – through seed treatments, weed control or genetic resistance – and reassuring China and other importers of U.S. grasses and crops.