Results and discussion

Fourteen alleles and 34 allelic compositions were detected in the set of 120 cultivars. The most frequent HMW-GS patterns were null, 7+9 and 5+10, which were present in 21 cultivars. Ten of the wheat accessions analyzed (8.3%) were observed to be heterogeneous in their glutenin profiles. Five cultivars were heterogeneous at one locus, two cultivars at two loci and another three varieties were heterogeneous at all three Glu-1 loci.

Three alleles were detected at the Glu-A1 locus. The most abundant allele was Glu-A1c, encoding the null subunit (57.1%, Table 1). It was found mostly in cultivars bred in SVK, CZE, YUG and GBR (Table 2). In contrast, the alleles Glu-A1b (subunit 2*) and Glu-A1a (subunit 1) were present in only 14 and 29% of the genotypes, respectively. These alleles were observed mainly in Hungarian, Italian, Austrian and American wheat samples (Table 2). A high frequency of alleles encoding subunits 1 and 2* in wheat cultivars from the USA was observed also by Shan et al. (Reference Shan, Clayshulte, Haley and Byrne2007). These subunits (1, 2*) have a positive impact on the rheological properties of dough, so they are highly desirable in cultivars used for bread-making.

Table 1

The frequencies of HMW-GS coded at the Glu-1 loci

Table 2

The frequencies (%) of HMW-GS at the Glu-1 loci according to the country of origin

A total of nine HMW-GS were identified at the Glu-B1 locus. Subunit 7+9 was the predominant one (43.3%, Table 1); it was abundant mostly in wheat bred in HUN, SVK, YUG, RUS and UKR. The subunit 6+8, which is associated with poor bread-making quality, was highly frequent in British and Austrian wheat samples (Table 2). Low-frequency HMW-GS, such as 13+16, 20, 21, 7 and 18, which are encoded by alleles at the Glu-B1 locus were also detected (Table 1). An unpaired subunit 7 was present mainly in French cultivars and also in wheat samples originating from USA, RUS and ITA (Table 2). The rare subunit 21 was found in the cultivar Mironovskaja ulucsennaja (UKR). Subunit 18, which is expressed commonly coupled with subunit 17, was observed as an unpaired subunit in the Italian cultivar Glutinoso. Redaelli et al. (Reference Redaelli, Ng and Pogna1997) observed expression of unpaired subunit 6 in some cultivars of T. aestivum L. They assumed that it was derived from the HMW-GS pair 6+8 (because it had the same mobility as subunit 6 of this pair), but that the expression of only subunit 6 was caused by a switch-off mutation in the coding sequence or in the regulatory region of the gene for subunit 8. Yuan et al. (Reference Yuan, Chen, Zhang, Yan, Zheng and Liu2009) characterized two inactive y-type genes for Glu-B1 in T. aestivum ssp. yunnanese and ssp. tibetanum. They indicated that the silenced 1By genes were 1By9 and that the silencing was caused by deletions of nucleotide A, which resulted in frameshift mutations responsible for the presence of premature stop codons.

Most of the cultivars (61.9%, Table 1) were found to express the subunit pair 5+10, which is encoded by allele Glu-D1d at the Glu-D1 locus. It has been shown that varieties that contain the pair 5+10 can form stronger dough than those that contain subunits 2+12 (Payne, Reference Payne1987; Liang et al., Reference Liang, Tang, Pena, Singh, He, Shen, Yao, Xia and He2010). Thus, wheat carrying the pair 2+12 can be utilized in the production of cookies, crackers or pasta rather than in bread-making. In this study, subunit pair 2+12, encoded by allele Glu-D1a, was observed frequently in cultivars bred in ITA and GBR (Table 2). A high frequency of subunit pair 2+12 has been published for wheat originating in Asian countries, such as China and Japan (Nakamura, Reference Nakamura2001; Li et al., Reference Li, Huang, Sui, Fan, Li and Chu2009), where wheat is used predominately in the production of noodles. Our analysis revealed also the presence of subunit 4+12, encoded by allele c at the Glu-D1 locus, in one cultivar that originated in the USA.

The wheat–rye 1BL.1RS translocation was identified in 25 cultivars by use of A-PAGE. No cultivars that originated in USA and FRA were found to carry this translocation. The presence of the 1BL.1RS translocation has a negative effect on the rheology of dough; it produces a sticky dough with a lack of overmixing, and low loaf volumes (Graybosch, Reference Graybosch2001; Gobaa et al., Reference Gobaa, Brabant, Kleijer and Stamp2008; Zheng et al., Reference Zheng, Byrne, Bai, Shan, Reid, Haley and Seabourn2009).

The Glu-score and Rye-score varied greatly; some samples reached the maximum value of 10 (cultivars GK Kapos, GK David, Vlasta, Baltimor, Luzanovka, Maverick and Smuggler). These cultivars are supposed to have superior bread-making quality. The highest average value of Glu-score was achieved by Hungarian cultivars (8.1). In contrast, the HMW-GS composition of British wheat samples resulted in an average value of only 5.9.