Two–dimensional polyacrylamide gel electrophoresis, with immobilized pH gradients in the first dimension, of barley seed proteins: Discrimination of cultivars with different malting grades

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Abstract
The suitability of high‐resolution two‐dimensional gel electrophoresis for barley cultivar discrimination and for classification with respect to their malting properties was studied. Seed proteins of 14 barley cultivars with different malting qualities were extracted with urea/dithiothreitol/Nonidet P‐40 buffer and subjected to two‐dimensional gel electrophoresis with immobilized pH gradients in the first dimension (IPG‐DALT). The results of IPG‐DALT were compared to the protein patterns obtained by a standard technique, sodium dodecyl sulfate polyacrylamide gel electrophoresis of hordeins. Sodium dodecyl sulfate‐gel electrophoresis yielded seven different “B” and four different “C” hordein patterns; “A” and “D” hordein patterns were uniform in all cultivars tested. Four cultivars could be distinguished unequivocally, the others were classified into three groups containing between two and five cultivars. In contrast to these findings, IPG‐DALT yielded three different “A”, eight different “B”, four different “C” and two different “D” hordein patterns. When the “A”, “B”, “C” and “D” hordein patterns were combined, ten cultivars exhibited unique hordein patterns whereas the remaining ones were classified into two groups containing two cultivars each. Moreover, when albumin and globulin proteins were used for evaluation in addition to the hordeins, all cultivars could be discriminated by IPG‐DALT. IPG‐DALT, performed on small‐scale and/or ready‐made gels, proved to be an ideal complementary system to one‐dimensional electrophoretic methods for routine seed testing purposes because of its speed, reliability, and simplicity. IPG‐DALT was also applied to study the relationship between the different polypeptide patterns and the malting quality. Although cultivars with identical one‐dimensional protein patterns but different malting quality could be successfully differentiated by IPG‐DALT, a direct correlation between specific protein spots or protein patterns to the malting quality was not found within the cultivars tested.