Characterization of old and modern durum wheat genotypes in relation to gluten protein and dietary fibre composition

Abstract

Old wheat varieties have been suggested to have greater health benefits compared with modern cultivars in relation to both bioactive components and gluten composition. However limited data are available supporting this hypothesis, in particular for durum wheat. So the purpose of this thesis was to improve our understanding of the influence of Italian 20th century breeding on the main grain quality characters. To this aim phenotyping of an old and a modern durum wheat group of genotypes was performed in relation to gluten and dietary fibre composition. The better gluten index observed in the modern group of genotypes was related to higher contents of glutenin and B- type LMW-GS which were, on average, two times higher in the modern group of durum wheat genotypes. Instead, a drastic reduction of the content of ω- 5 gliadins, also known as Tri a 19 a major allergen in food wheat allergy (WDEIA), was observed in the modern genotypes. The immunological and proteomic approaches adopted allowed these differences to be related not only to global down-expression, but also differences in specific isoforms. In relation to environmental influence on gluten protein composition, a higher glia/glu ratio, and contents of omega gliadins and type B LMW-GS content were observed when water deficit occurred during grain filling in 2013 crop season. Cell wall dietary fibre were determined with arabinoxylan (AX) and β-glucan (MLG) composition being determined by enzymatic fingerprinting in wholemeal and semolina flour. Although no significant variations were observed in the total amount of AX, a higher proportion of water soluble AX was observed in the modern varieties in wholemeal flour. The water soluble AX extracted from semolina flour showed a lower arabinose : xylose ratio in the old genotypes while a higher MLG content in semolina was observed in modern varieties. No differences were observed between the viscosities of aqueous extracts of soluble DF in old and recent varieties but considerable variability was observed between the different durum wheat genotypes. Similarly, no significant differences were observed between the contents of bound phenolic acids in the old and the modern genotypes. In relation to environmental influence on dietary fibre composition, increases in %WE-AX, relative viscosity and G3/G4 β-glucan ratio were observed when higher rainfall occurred during grain filling in 2014. In conclusion the 20th century breeding seems to have improved both technological and healthy quality of Italian durum wheat genotypes.