## 3 Results
### Composition of the Grain Protein Fractions

Table 2: Relative share of the gliadin protein sub-fractions (% of total SDS-PAGE lane intensity for each treatment within a variety), depending on the treatments (well watered: WW, moderate drought stress: MD, severe drought stress: SD) of the Iranian (Alvand, Mihan) and German wheat genotypes (Impression, Discus, Rumor and Hybery). For each variety, different letters within the same row represent significant differences between treatments (small letters: within \(\omega\)-gliadin; capital letters: within \(\gamma\)-gliadin; italic letters: within \(\alpha/\beta\)-gliadin). No letter means no significant differences in this group; \(p<0.05\); \(n=4\). Figure 4: Mean values of the glutenin concentration (mg g\({}^{-1}\) flour) depending on the treatments (well watered: WW, moderate drought stress: MD, severe drought stress: SD) of the Iranian (Alvand, Mihan) and German wheat genotypes (Impression, Discus, Rumor and Hybery). The error bars represent the standard errors of the measured values. Significant differences between treatments within a genotype are indicated by an asterisk (*). The bracket under the asterisk shows which treatments are significantly different from each other. Different letters within the same treatment represent significant differences (small letters: within WW treatment; capital letters: within MD treatment; italic letters: within SD treatment). \(p<0.05\); \(n=4\). Two-way ANOVA results are shown in the upper right corner of the diagram. G: genotype; T: different water treatment; GxT: Interaction between genotype and different water treatment; ns: not significant; *: significant effect. The protein bands of the glutenin fraction have been classified into the sub-fractions HMW (128.2-71.5 kDa), LMW-D (63.8-46.0 kDa), LMW-B (39.5-30.0 kDa) and LMW-C (29.7-24.0 kDa) (Table 3). Under WW conditions, HMW glutenins represented 27.3% to 41.3% of the total glutenins, with by far the highest values for the genotype Impression. This protein fraction was not affected by moderate drought, but increased significantly in the four German genotypes under severe drought stress. Interestingly, only a very slight increase was detectable in the Iranian genotypes (Table 3). The LMW-D glutenins represented the smallest sub-fraction with 1.6% to 6.4% of the total glutenins under non-stressed conditions. This group was absent in the genotype Mihan. The LMW-D glutenins increased significantly under severe drought stress in Discus and Rumor, and slightly in Alvand, while the opposite trend was observed in Impression and Hybery. The LMW-B glutenins accounted for 26.7% to 39.2% of the total glutenin under control conditions, with highest values for the genotype Mihan, and were overall not affected by drought stress (Table 3) with a slight exception of Rumor at severe stress. In well-watered plants, 22.8% to 37.9% of the total glutenins belonged to the LMW-C sub-fraction, with by far the highest values for the Iranian cultivar Alvand. In all four German wheat genotypes, the share of LMW-C glutenins was significantly reduced as a result of severe drought stress, while moderate drought had no significant effect (Table 3). A tendency towards lower LMW-C concentrations under severe stress was also observed in the Iranian genotype Alvand, while no effect was seen in Mihan. Overall, drought-induced changes in glutenin sub-fractions are reflected in the HMW/LMW ratio, which increased significantly under severe drought stress in all the German, but not in the Iranian genotypes.