Plant geneticist Bob Graybosch, at the USDA’s Agricultural Research Service’s (ARS) Grain, Forage, and Bioenergy Research Unit in Lincoln, Nebraska, U.S., developed a wheat that has no polyphenol oxidase — an enzyme present in all plants that causes discoloring. The enzyme causes browning in sliced apples, black spots in cut avocados and dark marks on banana peels.
The new wheat line, 070R1074, was developed by crossing two Australian wheats entered into the ARS National Small Grains Collection in the 1930s. Collaborating with the University of Nebraska and Montana State University, Graybosch screened wheats in the collection for polyphenol oxidase and then mated wheats with different forms of the genes that produced this enzyme. Wheat breeding lines with very low levels of polyphenol oxidase were generated from these crosses.
Although some low-polyphenol oxidase hard winter white wheats have been developed, many U.S. white wheats still have high levels of polyphenol oxidase, according to Graybosch. High polyphenol oxidase levels make U.S. producers less competitive in domestic and export markets.
In Asia, hard white wheat is popular for making products such as fresh noodles, and white whole grain breads are gaining favor in the U.S. To be competitive, U.S. milling companies need wheats with low or no polyphenol oxidase, the USDA said.
In their research, Graybosch and his colleagues discovered naturally occurring genetic mutations in the new wheat line, which resulted in nearly complete loss of polyphenol oxidase activity. Researchers have used the trait to improve breeding lines and could eventually incorporate it into elite lines to produce highly desirable cultivars.
ARS is USDA’s principal intramural scientific research agency.