The identification of specific, heritable characters which are associated with malting quality is of economic importance not only for barley breeders for developing new, high quality cultivars, but for quality control purposes for maltsters and brewers as well. This study was undertaken with the aim to investigate whether a correlation exists between the malting quality character "final attenuation" and specific amylase isoenzymes. For this purpose, buffer soluble proteins were extracted from malted or germinated barley grain. After a heat treatment (60-degrees C, 15 min) these extracts were subjected to isoelectric focusing (IEF) either on pH 3 - 10 gradient gels (carrier ampholyte IEF) or pH 4 - 9 gradient gels (Immobiline-IEF). Protein bands exhibiting amylase acitvity, were specifically detected using starch impregnated polyacrylamide print gels, followed by iodine staining. As a whole, 17 spring and 20 winter barley cultivars covering a wide range of final attenuation values were subjected to these investigations. Our results are as follows: In the 37 cultivars examined. the occurrence of certain amylase-isoenzymes was found to be closely associated with the malting quality character "final attenuation": All cultivars which are of low or at best moderate final attenuation values possess the isoenzyme band "B" (isoelectric point almost-equal-to 6.8), whereas those cultivars which do not possess this "B" isoenzyme band, but exhibit a very pronounced "A" isoenzyme band instead, are predominantly of high malting grade. Because of the evident relationship between the amylase isoenzyme bands "A" and "B" and final attentuation values, these isoenzyme bands can be utilized to predict the approximate final attenuation values of unknown barley cultivars or new breeding lines. Preliminary results (utilizing the different temperature stabilities and staining behaviour of amylases) showed that these isoenzyme bands "A" and "B" are beta-amylases.

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.