## 3 Results
### Composition of the Grain Protein Fractions  
Gliadin and glutenin fractions were further analyzed by SDS-PAGE and relative band intensities for each fraction were obtained. In total, between 16 and 20 protein bands were recorded for the gladin fraction, depending on the genotype. They can be divided into the three sub-fractions \(\omega\)-gliadins (61.3-45.4 kDa), \(\gamma\)-gliadins (39.3-32.2 kDa) and \(\alpha/\beta\)-gliadins (30.3-20.7 kDa) according to their molecular weight and their position. The relative share of the gliadin sub-fractions changed with increasing drought stress (Table 2). Under well-watered conditions, the \(\omega\)-gliadins represented the smallest sub-fraction with 10.7-16.4% of the total gliadins. Their share increased significantly in all six wheat genotypes under drought stress, and in five out of six genotypes this effect was significantly stronger in the severe compared to the moderate drought treatment. The \(\gamma\)-gliadins represented the second largest gliadin sub-fraction under WW conditions, with a share of 23.2-36.1% of the total gliadins. While \(\gamma\)-gliadins were not significantly affected by drought stress in four out of the six wheat genotypes, they were significantly increased under severe drought stress compared to WW plants by 4.9% and 3.3% in Rumor and Discus, respectively. An opposite tendency was observed for \(\alpha/\beta\)-gliadins, which represent the dominant gliadin sub-fraction with a share of 45.7-61.8% of the total gliadins under WW conditions. With the exception of Alvand, \(\alpha/\beta\)-gliadins were reduced under drought stress in all genotypes (significant for Mihan, Discus and Rumor). Figure 3: Mean values of the gliadin 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. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Genotype** & \multicolumn{3}{c}{**Alvand**} & \multicolumn{3}{c}{**Mihan**} & \multicolumn{3}{c}{**Impression**} \\ \hline Treatment & WW & MD & SD & WW & MD & SD & WW & MD & SD \\ \hline \(\omega\)-Gliadin & 14.9 b & 15.5 b & 17.0 a & 12.4 c & 14.6 b & 15.5 a & 16.4 b & 17.2 ab & 17.4 a \\ \(\gamma\)-Gliadin & 36.1 & 37.0 & 48.1 & 34.6 Ab & 31.9 B & 35.5 A & 23.2 & 23.7 & 24.8 \\ \(\alpha/\beta\)-Gliadin & 45.7 & 48.1 & 48.4 & 53.0 \(a\) & 53.5 \(a\) & 48.7 \(b\) & 60.4 & 59.1 & 57.8 \\ \hline \(\Sigma\) & 100 & 100 & 100 & 100 & 100 & 100 & 100 & 100 \\ \hline
**Genotype** & \multicolumn{3}{c}{**Discus**} & \multicolumn{3}{c}{**Rumor**} & \multicolumn{3}{c}{**Hybery**} \\ \hline Treatments & WW & MD & SD & WW & MD & SD & WW & MD & SD \\ \hline \(\omega\)-Gliadin & 11.3 c & 12.8 b & 14.4 a & 10.7 c & 12.0 b & 13.1 a & 13.3 c & 14.4 b & 16.5 a \\ \(\gamma\)-Gliadin & 28.2 B & 30.9 Ab & 31.5 A & 29.2 B & 30.9 B & 34.1 A & 24.9 & 25.1 & 23.9 \\ \(\alpha/\beta\)-Gliadin & 60.5 \(a\) & 56.2 \(b\) & 54.1 \(b\) & 60.1 \(a\) & 57.1 \(a\) & 52.7 \(b\) & 61.8 & 60.6 & 59.7 \\ \hline \(\Sigma\) & 100 & 100 & 100 & 100 & 100 & 100 & 100 & 100 \\ \hline \hline \end{tabular}
\end{table}