THE RELATIONSHIP BETWEEN D-HORDEIN AND MALTING QUALITY IN BARLEY

The contribution of gain protein to the malting quality of barley (Hor deum vulgare L.) was investigated by comparing the hordein composition and the malting quality in barley produced under a range of field con ditions. Two malting cultivars, Schooner and Arapiles, and one feed cu ltivar, Galleon, were grown under five nitrogen regimes in each of two years. Hordein composition of the grain was determined at maturity us ing a combination of sodium dodecyl sulphate-polacrylamide gel electro phoresis and laser densitometry. Malt extract was determined on all sa mples after micromalting. Variation in growth conditions resulted in a wide range of grain protein contents and malt extract values, as well as variation in the proportions of the individual B, C and D hordeins in the grain. D hordein in particular varied over a 10-fold range. Hi gh levels of all protein fractions were associated with low malt extra ct. Total protein, as expected, displayed a strong, negative correlati on with malt extract. The relationship was cultivar specific and separ ate regression lines were generated for each cultivar. Of the individu al hordein fractions, D hordein displayed the strongest negative corre lation with malt extract and its relationship to malt extract was inde pendent of cultivar. A consistent relationship between D hordein and m alt extract was observed across seasons, treatments and cultivars that was indicative of a causal relationship between D hordein and malting quality. D hordein therefore offers an alternative measurement to tot al protein for the prediction of malting quality over a wide range of environmental conditions and cultivars. (C) 1996 Academic Press Limite d