Abstract
The impact of breeding on grain yields of wheat varieties released during the 20th century has been extensively studied, whereas less information is available on the changes in gluten quality associated with effects on the amount and composition of glutenins and gliadins. In order to explore the effects of breeding during the 20th century on gluten quality of durum wheat for processing and health we have compared a set of old and modern Italian genotypes grown under Mediterranean conditions. The better technological performance observed for the modern varieties was found to be due not only to the introgression of superior alleles of high (HMW-GS) and low molecular weight (LMW-GS) glutenin subunits encoded at Glu-B1 and Glu-B3 loci, but also to differential expression of specific storage proteins. In particular, the higher gluten index observed in modern genotypes was correlated with an increased glutenin/gliadin ratio and the expression of B-type LMW-GS which was, on average, two times higher in the modern than in the old group of durum wheat genotypes. By contrast, no significant differences were found between old and modern durum wheat genotypes in relation to the expression of α-type and γ-type gliadins which are major fractions that trigger coeliac disease (CD) in susceptible individuals. Furthermore, a drastic decrease was observed in the expression of ω-type gliadins in the modern genotypes, mainly ω-5 gliadin (also known as Tri a 19) which is a major allergen in wheat dependent exercise induced anaphylaxis (WDEIA). Immunological and 2DE SDS-PAGE analyses indicated that these differences could be related either to a general down-regulation or to differences in numbers of isoforms. Lower rainfall during grain filling period was related to overall higher expression of HMW-GS and ω-gliadins. In conclusion, breeding activity carried out in Italy during the 20th century appears to have improved durum wheat gluten quality, both in relation to technological performance and allergenic potential.
Highlights
Durum wheat (Triticum turgidum L. spp. durum) is a worldwide crop, cultivated on about 30–35 million hectares and in particular in the Mediterranean basin where it represents a staple crop (Guzmán et al, 2016)
The better technological performance observed for the modern varieties was found to be due to the introgression of superior alleles of high (HMW-GS) and low molecular weight (LMW-GS) glutenin subunits encoded at Glu-B1 and Glu-B3 loci, and to differential expression of specific storage proteins
A drastic decrease was observed in the expression of ω-type gliadins in the modern genotypes, mainly ω-5 gliadin which is a major allergen in wheat dependent exercise induced anaphylaxis (WDEIA)
Summary
Durum wheat (Triticum turgidum L. spp. durum) is a worldwide crop, cultivated on about 30–35 million hectares and in particular in the Mediterranean basin where it represents a staple crop (Guzmán et al, 2016). Endosperm prolamins, accounting for up to 80% of the total grain proteins, determine the technological quality of durum wheat flour (semolina) that is mostly used for the production of pasta, bread and cous cous These alcohol-soluble grain storage proteins are classified, based on their electrophoretic mobility, into monomeric gliadins (α-, γ- and ω-) and polymeric glutenins (comprising high and low molecular weight glutenin subunits, HMW-GS and LMW-GS). On the basis of N terminal amino acid sequences, three subgroups of typical LMW-GS can be recognized, called LMW-s, LMW-m and LMW-i types, according to the first amino acid residue of the mature protein: serine, methionine or isoleucine, respectively (D’Ovidio and Masci, 2004) They are encoded on the chromosomes 1 at the Glu-A3 and Glu-B3 loci (1A and 1B) and at the loci tightly linked to the Gli-1 and on the group 6 chromosomes at Gli-2 loci. The B-subunits are typical LMW-GS with a characteristic structure and are encoded by genes on the group 1 chromosomes while the C- and
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