Researchers Clone Powdery Mildew Resistance
Gene By Jennifer Arnold
September 7, 2001
Service scientists in Ames, Iowa, have cloned and characterized the powdery
mildew resistance gene from barley. This is the first successful cloning of a
gene that confers active disease defense to small-grain cereals.
ARS geneticist Roger Wise, postdoctoral assistant Dennis
Halterman and Ph.D. candidate Fusheng Wei, at the ARS
Corn Insects and Crop
Genetics Research facility in Ames, collaborated with Paul
Schulze-Leferts group at the
Laboratory in the United Kingdom to isolate from barley two of the 30
alternative forms of the Mla resistence gene, Mla6 and
Mla1. A patent has been filed on the newly isolated genes.
Powdery mildews form a superficial white, powdery coating on
leaves, buds, shoots and flower petals. The mildews are caused by more than
1,600 species of fungi.
Fungal pathogens are perhaps the greatest impediment to cereal
grain production worldwide, sometimes causing yield losses of up to 50 percent.
To reduce such losses, plant breeders have turned to genetic varieties that
resist fungal diseases.
In recent years, scientists have successfully cloned resistance
genes from a variety of model plant species, such as Arabidopsis, rice and
tomato. The Arabidopsis genome-- 120 million letters of genetic code--is the
smallest in plants. It has been more difficult to isolate genes from crop
plants, some of which possess genomes even larger than that of human beings.
For example, the barley genome is 40 times larger than the Arabidopsis
The Ames researchers were able to show that Mla6 confers
resistance to powdery mildew in wheat. This is the first demonstration of using
genetic engineering to transfer a resistance gene between cereal crop
The research aids the understanding of how disease resistance
genes work in interactions between pathogens and their crop plant hosts.
ARS is the U.S. Department of
Agricultures chief scientific research agency.