Improving wheat as a source of dietary fibre for human health

Wheat is a major source of dietary fibre (DF) in the UK diet, with bread alone providing 20% of the total daily intake in adults(1).Furthermore, although white bread contains less DF (2·5–4·5%) than wholemeal (10–14%), the high consumption (about 65% of totalbread products) means that it alone contributes 11% of the total intake of DF(1). The major DF components in white flour and breadare cell wall polysaccharides, principally arabinoxylan (AX) and β-glucan which account for about 70% and 20% of the total,respectively.Analyses of 150 wheat cultivars grown on the same site showed that the total content of AX in white flour ranged from 1·35% to2·75% dry wt, and of soluble AX from 0·30% to 1·40%(2). The proportion of soluble AX was generally about 25% of the total.However, the Chinese cultivar Yumai 34 was shown to contain the highest contents of both total and soluble AX, and is nowbeing exploited by wheat breeders as a source of these traits.We have now analysed wheat lines of wider genetic diversity, including a core set of lines from the Watkins collection of land raceswhich were collected from 32 European, Asian and North African Countries in the 1920s and 1930s(3). Preliminary analyses showedthat the range of content of total AX in wholemeal was wider than in the 150 cultivars, with up to 35% soluble AX (Figure 1). Thishigh solubility may be related to differences in the fine structure of AX, particularly the ratio of xylose residues which are substitutedwith single and two arabinose residues: this is being compared by fingerprinting the patterns of oligosaccharides released after digestionwith endoxylanase.