Little-known ancient grains could hold keys to saving wheat, one of the world’s most important cereal crops, from an unrelenting fungus.
Except for wheat breeders, farmers and scientists, few people have ever heard of einkorn wheat, an ancient variety still cultivated in some parts of the Mediterranean. Emmer wheat, found at some archeological sites and still growing wild in parts of the Near East, may be equally obscure.
Wheat is under attack by a fungal pathogen that has become an international priority for scientists. Ug99 is a strain of the stem rust fungus (Puccinia graminis) that threatens up to 90 percent of the world’s wheat and much of its barley. Even worse, the fungus is constantly evolving. Genes that seem to offer immunity one growing season become susceptible to newly developed “races” the next growing season.
Since Ug99 was first reported in Uganda in 1999, at least six related races of the pathogen have been discovered. It has yet to reach the United States, but it is spreading throughout eastern and southern Africa, Iran, and Yemen.
Researchers worldwide are working to identify genes capable of resisting Ug99 for eventual use in wheat and barley. As part of that effort, Agricultural Research Service scientists Matt Rouse and Yue Jin are searching for resistance genes among some of wheat’s lesser-known relatives. Both scientists are at the ARS Cereal Disease Research Laboratory in St. Paul, Minnesota. Along with einkorn and emmer wheat, candidates for study include goatgrass (Aegilops tauschii), triticale (x Triticosecale), and other wild relatives of wheat.
Goatgrass is a wild relative of domesticated wheat, and breeders have tapped genes from it to boost the immunity of commercial wheat to a number of pests and pathogens. Triticale, found in some breakfast cereals and other foods, is a hybrid of rye and wheat. It holds promise because rye is nearly immune to Ug99. Also, triticale is considered a potential bridge for transferring genes from rye into wheat.
Scientists often study a crop’s wild ancestors for genes that will confer resistance to emerging pests and pathogens. But what may be noteworthy is the diversity of grasses being evaluated by ARS scientists and others as part of the international effort to combat this fungal menace. Rouse and Jin say the extensive search is necessary because Ug99 evolves so quickly that breeders will probably need several resistance genes for “stacking” into commercial cultivars. That way, when the pathogen attacks, it will have more than one genetic hurdle to overcome. Several genes recently discovered by ARS researchers and their colleagues are being deployed by international breeding teams and are offering some Ug99 protection.
In one study, Rouse and his colleagues focused on locating a gene in einkorn wheat that confers near immunity to Ug99. The gene, known as Sr35, was previously discovered in einkorn, but its exact location in the plant’s vast genome remained a mystery. The wheat genome is huge, containing nearly two times more genetic information than the human genome.
Read more at USDA-ARS magazine website.