ARS | Publication request: Large Scale Survey of Tocol Content in Barley Germplasm

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: April 25, 2009
Publication Date: July 18, 2009
Citation: Wise, M.L. 2009. Large Scale Survey of Tocol Content in Barley Germplasm. American Society of Plant Biologists Annual Meeting, July 18-22, 2009, Honolulu, Hawaii. Poster No. P60028.

Technical Abstract: The tocochromanols (or tocols, compounds showing vitamin E activity) are biosynthesized exclusively by photosynthetic organisms. Although the precise benefits of vitamin E are not known, diets deficient in vitamin E appear to be associated with atherosclerosis and other cardiovascular disease. The tocochromanols consist of eight naturally occurring compounds: alpha-, beta-, gamma-, delta-tocopherol and alpha-, beta-, gamma-,delta-tocotrienol. All eight compounds consist of a phenolic, polar chromanol head group, the four isomers differing in the methylation pattern on the phenolic moiety. The tocopherols are differentiated from the tocotrienols by being conjugated to a saturated phytyl side chain whereas the tocotrienols are conjugated to an unsaturated geranylgeranyl side chain. Among the cereal grains barley has moderately high levels of tocochromanols. Barley is somewhat unique in that the grain contains all eight congeners. The few published reports on tocol concentrations in barley indicate that levels of tocopherol and tocotrienols are highly variable and this variability is correlated primarily to genotype. This study examines the tocol content in 864 germplasm lines of barley from year one of the Barley Coordinated Agriculture Project (Barley CAP). Ninety-six lines from 9 different locations were analyzed. The total tocol content ranged from 21.9 to 103 mg/kg with a mean of 59.9 mg/kg. As expected alpha-tocotrienol represented the dominate tocol congener and ranged from 4.8 to 61.6 mg/kg with a mean of 32.5 mg/kg. These preliminary results again demonstrate that tocol production in barley is highly variable. Although the data does not allow analysis of an environmental effect there is clearly a large genetic effect. Noteworthy is the relatively high levels of gamma-tocotrienol found in the Virginia Tech germlines. These ranged from 4.5 to 13.1 mg/kg with a mean of 8.3 mg/kg, almost twice the mean of the next highest location. The basis for this higher gamma-tocotrienol level is not clear although it can be noted that these particular lines were winter barley varieties.