O-5
A single PCR marker for predicting the activity levels of various enzymes responsible for cell wall and starch degradation during malting
Presenter: Michael Voetz, VLB Berlin, Berlin, Germany
Co-Authors: I. Fechter and F. Rath, VLB Berlin, Berlin, Germany

Due to the lack of molecular markers, the assessment of newly bred barley lines is still based on micromaltings and malt analyses. In the past, this time-consuming and cost-intensive strategy restrained the European breeders from using high-yielding but low-quality feed barley varieties in their crossings. Consequently, malting barley has significant yield deficits in comparison to other crops. The resulting poor competitiveness increasingly threatens the supply of high-quality malting barley to the brewing industry. The examination of physical, chemical, and germinative properties of several unmalted barley varieties showed no systematic differences between malting and feed barley types. The barleys were micromalted and samples were taken at different stages of the malting process for enzyme measurements and gene expression studies. In general, the malting cultivars were characterized by higher activities of the relevant cytolytic, proteolytic, and amylolytic enzymes. In feed barley, these enzymes are synthesized at later stages and their distribution within the germinating kernel is more limited. The variation in enzyme activity could be traced back to differential gene expression: the mRNAs of the corresponding enzyme genes are present in germinating malting barley in up to twofold higher concentrations than in feed cultivars. Further studies resulted in the finding of another transcript which accumulates in up to 500-fold higher concentrations, during germination, in all malting cultivars tested. The corresponding gene product possibly has a regulating impact on the complete set of relevant enzymes synthesized in the aleurone. Within that gene, a DNA polymorphism between malting and feed barley could be detected and subsequently used for the design of a selective PCR primer. In all barley genotypes hitherto analyzed, those with low enzyme activities and thus poor malting quality could be recognized using this marker. So, it is now possible for the first time to use a robust PCR marker system to predict enzyme activities and potential malt quality without malting the barley, thus substantially reducing the amount of time spent on breeding of optimized barley varieties. The use of the PCR marker guarantees the conservation of enzyme-dependent quality traits in the progenies when high-yielding feed varieties are used as crossing partners for malting varieties. Thus, the selection of important agronomic traits, e.g. yield, will be revalued. This could lead to an improved competitiveness of malting barley in the future.

Michael Voetz, born in 1964, received a diploma in biology from the University of Cologne in 1991. He earned a Ph.D. in plant molecular biology from the University of Cologne/Max-Planck-Institute for Breeding Research in 1995. From 1995 to 2000, he was scientific collaborator at the Research Department of the Weissheimer Malzfabrik in Andernach, working in the field of barley biotechnology. Since 2000, he has been head of the biotechnology/PCR laboratory at the Research Institute for Raw-Materials within VLB in Berlin.