Chromosome 1B-encoded gliadins and glutenin subunits in durum wheat: Genetics and relationship to gluten strength

Abstract

The progenies of crosses between Berillo and four durum wheat cultivars were analysed for storage protein composition (by four different electrophoresis procedures), genetic segregation and gluten quality (by SDS sedimentation test and Viscoelastograph). The crosses enabled the segregation patterns of alleles at Gli-B1, Glu-B3 and Glu-B1 on chromosome 1B, and at Gli-A2 on chromosome 6A to be determined. The gene order on chromosome 1B was deduced to be Glu-B1-centromere-Glu-B3-Gli-B1, with 47% recombination between Glu-B1 and Glu-B3, and 2% between Glu-B3 and Gli-B1. Genes coding for γ-gliadins at Gli-B1 were distal to ω-gliadin genes with respect to the centromere. Analyses of the progeny (F4 grains) from single F2 plants, indicated that gliadins γ-42 and γ-45 are only genetic markers of quality, whereas allelic variation for low molecular weight (LMW) glutenin subunits encoded at the Glu-B3 locus is primarily responsible for differences in SDS sedimentation volume and gluten viscoelastic properties. High molecular weight (HMW) glutenin subunits 7+8 also gave larger SDS sedimentation volumes and higher gluten elastic recoveries than subunits 6+8 and 20. The positive effects of the so-called LMW-2 glutenin subunits and HMW subunits 7+8 were additive, with LMW-2 being the most important proteins for pasta-making quality as evaluated by SDS-sedimentation and gluten viscoelasticity (both parameters related to firmness of cooked pasta). Two alleles at Gli-A2 coding for α-gliadins were also found to have different effects on gluten firmness.