Assessment of genetic diversity in bread and durum wheat landraces based on biochemical and in silico analysis of glutenin and gliadin proteins

This study assessed the genetic diversity between durum wheat landraces (L1-L12) and bread wheat landraces (L1-L12) using a comparative biochemical (SDS-PAGE) and bioinformatics analysis of their major gluten proteins: LMW-GSs, HMW-GSs, and gliadin fractions. Biochemical analysis revealed significant polymorphism in both species, with approximately 24-26% of the assessed loci showing variability. Cluster analysis based on the overall protein profiles successfully grouped all genotypes into three distinct clusters. Specific focus on the HMW-GSs and omega-gliadins revealed molecular markers related to end-use quality. Significant allelic polymorphism was detected at the Glu-1 loci: the Glu-A1 subunit 1 was fixed in durum wheat but rare in bread wheat, while Glu-A1 subunit 2 showed the inverse distribution. Diverse alleles (7, 8, 17, 18) were found at Glu-B1. Furthermore, bread wheat generally had five omega-gliadin subunits, compared to only four in durum wheat. Crucially, hierarchical clustering using the combined HMW-GS and omega-gliadin data provided a robust molecular signature, cleanly separating all genotypes into two clusters (Durum and Bread). This demonstrates the effectiveness of these two protein groups in distinguishing the wheat types, reflecting quality-related genetic differences. The subsequent bioinformatics analysis of 3D structures showed that most fractions (LMW-GSs, gamma-gliadin, and alpha/beta-gliadin) are highly conserved, with only minor variations in the N-terminal regions. In contrast, HMW-GSs and omega-gliadin exhibited significant structural divergence in their central repetitive domains. HMW-GS variations in beta-turn and beta-spiral distribution directly correlated with dough viscoelastic properties. Notably, durum omega-gliadin was found to be longer and contained more rigid polyproline type II helices, highlighting key structural differences influencing wheat quality.