METABOLISM AND ANALYSIS OF CEREAL PHYTOCHEMICALS
Location: Cereal Crops Research
Title: Factors Effecting Phytonutrient Biosynthesis in Oat
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2008
Publication Date: June 29, 2008
Citation: Wise, M.L., Jackson, E.W., Doehlert, D.C. 2008. Factors Effecting Phytonutrient Biosynthesis in Oat [abstract]. In: International Oat Conference, June 28 - July 2, 2008, Minneapolis, Minnesota. p. 5.
Numerous reports correlate oat consumption with lowered risk of cardiovascular disease. Although much of this research has focused on the role of soluble fiber, oat produces other phytonutrients having beneficial physiological effects. These include avenanthramides, tocopherols, and tocotrienols. Although avenanthramides were described almost twenty years ago by F. William Collins, only recently has substantial evidence surfaced that these metabolites provide health benefits. One of these is to mitigate inflammatory responses in model systems for atherosclerosis. They also appear to reduce oxidative damage in exercise stressed rats.
The levels of avenanthramides found in oat grain are highly variable, ranging from below 10 ppm up to 400 ppm or more. What factors mediate these variations is poorly understood, although there are clear genotypic and environmental relationships. Seedling studies show that leaf tissues respond to crown rust infection or pathogen elicitors by up-regulating avenanthramide biosynthesis. A limited number of field studies have shown clear environmental effects on avenanthramide content in oat leading to speculation that grain avenanthramide levels are elevated in response to rust infection. This discussion will provide clear evidence that such a relationship exist. Data from replicated field trials evaluating eighteen oat cultivars in eastern North Dakota will be presented. Two of the test environments suffered heavy rust pressure, the other four did not. Avenanthramide content showed a distinct correlation with the occurrence of rust, with levels from ten to thirty times higher in the infected plants. Additionally, there appears to be a strong genotypic influence on grain avenanthramide production. Field tests in a crown rust free environment (Idaho) were conducted to evaluate avenanthramide levels in seed of a recombinant inbred line (RIL) population derived from a cross of the crown rust susceptible parent ‘Otana’ and the resistant parent TAM O-405. Parents and RILs were grown under an artificially produced crown rust epidemic and under no disease pressure. In the disease free environment, one fungicide application of Tilt® was applied at the flag leaf stage. Again, a correlation between rust infection and avenanthramide production was observed. Interestingly, some of the RILs showed extremely high avenanthramide levels, with or without rust infection. These preliminary results suggest the possibility of breeding for higher avenanthramide content in oat.
To study the factors affecting tocopherol levels in oat, a-tocotrienol, a-tocopherol, and total tocopherol contents were measured in seed of the Ogle/TAM O-301 RIL population from replicated Idaho field trials. Mean levels of all three tocopherol measurements were higher from the irrigated Aberdeen location than from the non-irrigated Tetonia location. This data indicates that moisture content and soil nutrients could directly affect whole grain tocopherol levels. Genetic analysis detected one quantitative trait loci (QTL) with major effects and four QTL with minor effects accounting for a majority of the a-tocotrienol variation across all locations, while six QTL accounted for a majority of the a-tocopherol variation. Only one QTL affecting total tocopherol was detected apart from QTL affecting a-tocotrienol and a-tocopherol. These results should facilitate the development of markers linked to key genes affecting tocopherol production in oat whole grain, as well as, the identification of the environment factors influencing these important quality traits.