Effect of additional water supply during grain filling on protein composition and epitope characteristics of winter oats.

Pure oats in gluten-free diets (GFD) represent important nutritional benefits for people suffering from celiac disease (CD). However, oat cultivars do not contain the typical CD-related wheat gliadin analog polypeptides. Emerging evidence suggests that oat cultivars containing gluten-like epitopes in avenin sequences may pose potential health risks for celiac patients in rare cases, depending on the individual's susceptibility. Consequently, it is necessary to screen oats in terms of protein and epitope composition, to be able to select safe varieties for gluten-free applications. The overall aim of our study is to investigate the variation of oat protein composition directly related to health-related and techno-functional properties and to examine how the protein compositional parameters change due to irrigation during the grain-filling period as compared to the natural rain-fed grown, in a large winter oat population of different geographic origin. Elements of an oat sample population representing 164 winter oat varieties from 8 countries and the protein composition of resulting samples have been characterized. Size distribution of the total protein extracts has been analyzed by SE-HPLC, while the 70% ethanol extracted proteins were analyzed by RP-HPLC. Protein extracts are separated into 3 main groups of fractions on the SE-HPLC column; polymeric, avenin, and non-avenin monomeric protein groups, representing 59.17-80.87%, 12.89-31.03%, and 3.40-9.41% of total protein content, respectively. The ratio of polymeric to monomeric proteins varied between 1.71 and 6.07. 91 RP-HPLC-separated peaks have been differentiated from the ethanol extractable proteins of the entire population. The various parameters identified a lot of variation, confirming the significance of genotypic variation. In addition, it was also established that the additional water supply during grain filling significantly affected the various quantitative parameters of protein content, but not its qualitative structure. This environmental effect, however, was strongly genotype-dependent. Winter oat genotypes with low levels of epitope content were identified and it was proven that these characteristics were independent of the environmental factor of water availability. These genotypes are appropriate for initiating a specific breeding program to yield oat cultivars suitable for CD patients.