Genetic analysis of water extractable arabinoxylans in bread wheat endosperm

Two mapping populations were used for the analysis of the water-extractable arabinoxylans. One originated from a cross between the hexaploid cultivars 'Courtot' and 'Chinese Spring' and the other from a cross between an amphi ploid (Synthetic) and cv 'Opata'. Arabinose (Ara), and xylose (Xyl) content s were quantified for the 91 and 76 lines obtained from the two crosses, re spectively. Relative viscosity (eta(rel)) Of the wheat flour aqueous extrac t was evaluated by capillary viscometry. Both crosses gave similar correlat ion coefficients between sugar contents and relative viscosity. There were strong positive relationships between arabinose, xylose and arabinoxylan co ntents. The relative viscosity was strongly and positively related to the a rabinoxylan content and strongly and negatively related to the Ara/Xyl rati o (arabinose content to xylose content). For one of the two crosses two mea surements of relative viscosity were generated from 2 years of consecutive harvesting. As a strong correlation was observed between these two measurem ents, an important genotypic effect can be deduced for the relative viscosi ty of water-extractable arabinoxylans. QTL (quantitative trait locus) resea rch did not reveal any chromosomal segments that were strongly implicated i n variations in sugar content. However, a QTL was found for relative viscos ity values and the Ara/Xyl ratio on the long arm of the IB chromosome for t he two crosses considered. This QTL explained 32-37% of the variations in r elative viscosity and 35-42% of the variations in the Ara/Xyl ratio. Genes located at this QTL controlled relative viscosity through modifying the Ara /Xyl ratio. Variations in the Ara/Xyl ratio were supposedly related to diff erences in the molecular structure of water-extractable arabinoxylans. Mino r QTLs were also obtained for relative viscosity and Ara/Xyl ratio, but the chromosomes concerned were different for the two populations evaluated.