Gene-ecology of durum wheat HMW glutenin reflects their diffusion from the center of origin

Abstract

The production of many food items processed from wheat grain relies on the use of high gluten strength flours. As a result, about 80% of the allelic variability in the genes encoding the glutenin proteins has been lost in the shift from landraces to modern cultivars. Here, the allelic variability in the genes encoding the high molecular weight glutenin subunits (HMW-GSs) has been characterized in 152 durum wheat lines developed from a set of landraces. The allelic composition at the two Glu-1 loci (Glu-A1 and -B1) was obtained at both the protein and the DNA level. The former locus was represented by three alleles, of which the null allele Glu-A1c was the most common. The Glu-B1 locus was more variable, with fifteen alleles represented, of which Glu-B1b (HMW-GSs 7 + 8), -B1d (6 + 8) and -B1e (20 + 20) were the most frequently occurring. The composition of HMW-GSs has been used to make inferences regarding the diffusion and diversification of durum wheat. The relationships of these allelic frequencies with their geographical distribution within the Mediterranean basin is discussed in terms of gene-ecology.

Figure 1

Example of the outputs of the multiple method used to assign the subunit 7 + 19 to the durum wheat landrace SSD 453. SDS-PAGE and Lab-on-a-chip were run on the samples (A,B). Then PP4 primer pairs (BxF/BxR) were tested (C). (A) SDS_PAGE; (1) Durazio Rijo cv, 14 + 19; (2) SSD 322, (3) SSD 451, (4) SSD 453, (5) Marques cv, 7 + 15; (B) Lab-on-a-chip on SSD 453; (C) PP7 marker profile; (1) SSD 451; (2) SSD 453; (3) SSD 494; (4) Francia, 17 + 18, (5) Chinese Spring, 7 + 8; (6) David, 18*; (7) Negative control. To improve the clarity and conciseness of the figure, cropped section of bigger gels have been reported for SDS-PAGE and TAE gel.

Figure 2

Geographic distribution and the relative frequencies for (A) Glu-A1 and (B) Glu-B1. Colors indicate the diverse HMW-GS subunits identified within each country of provenance of the durum wheat germplasm entries.