Genetic Variability of the Alpha-Amylase Gene Family in Domesticated and Wild Barley

Barley α-amylase (α-(1,4)-D-glucanohydrolase; EC 3.2.1.1) is an endohydrolase that catalyses the cleavage of internal α-(1,4)-glucosyl linkages of amylose and amylopectin and is a key enzyme in the degradation of starch during brewing. The enzyme has been shown to be an important factor in influencing fermentability, a critical quality parameter for brewing (Evans et al. 2005, 2007). The genetic variation for α-amylase has been assessed in a range of varieties (Takano and Takeda 1985), however functional characteristics of this variation has not been reported. The aims of this study are to characterise different allelic forms of α-amylase at biochemical and molecular levels and to investigate the impact of this genetic variation on fermentability and other key malt quality parameters. Barley germplasm including breeding lines, wild barley accessions and mapping population parents were screened for variation in α-amylase using isoelectric focusing (IEF) in conjunction with activity staining. IEF screening found significant variation in IEF banding patterns with 14 and 49 different forms of α-amylase isoenzymes identified for low and high-pI groups respectively. The genetic control of differences in α-amylase characteristics and the association of allelic variation with malt quality parameters for different isoenzymes were studied in mapping populations and the results will be described in this paper.