High variation in the gluten composition and grain protein content among synthetic wheat lines

Wheat wild relatives are important sources for the genetic enhancement of cultivated wheat. Here, we evaluated the gluten composition, grain protein content, and several quality-related gluten indices across 47 synthetic wheat lines or amphiploids resulted from the crosses between emmer wheat, durum wheat, T. timopheevii, Ae. crassa, Ae. ventricosa and Ae. tauschii. The grain protein content ranged from 15% to 23.5%, in 79% of the studied lines. Lines exhibiting high protein contents generally demonstrated normal gluten strength. This characteristic primarily resulted from the inclusion of emmer wheat, durum wheat, or T. timopheevii as one of the parental lines in their pedigree. About 18% of the lines, which mainly resulted from (T. durum × Ae. tauschii) × common wheat crosses demonstrated strong gluten properties. The analysis of high molecular weight glutenin subunits (HMW-GSs) revealed a greater diversity for the Glu-B1 locus than those from Glu-A1 and Glu-D1. The most frequently identified HMW-GSs included Null, 1, and 2* at the Glu-A1 locus; 21 + 19, 7 + 8, 14 + 15, 6 + 8, 14 + 18, 21 + 15, 13 + 16 + 9, and 6 + 22 at the Glu-B1; and 3 + 10 or 3 + 10.5, 2 + 12 or 2 + 12.5, and 5 + 10 or 5 + 10.5 at the Glu-D1. Subunits associated with the bread-making quality of wheat, particularly observed in durum wheat × Ae. tauschii cross combinations. Cluster analysis based on gliadin and glutenin subunits did not accurately reflect the genomic composition of the lines, though some lines with similar genomic backgrounds were clustered together. These results suggest the potential of our synthetic wheat lines to enhance the nutritional and baking quality of wheat flour.