Understanding beta glucan and beta glucanase genes: potential for barley and malt improvement through biotechnology.

Ullrich, S.E., Han, F. and Romagosa, I.

Abstract
The beta glucan content of barley and the development of beta glucanase activity during germination are controlled by a complex set of interactions between genetic factors and other influences, making it difficult to obtain a clear understanding of the genetic component and thus hindering improvements in the relevant aspects of malting quality by barley breeders. However, recent developments in genetic mapping have enabled the authors to identify three quantitative trait loci relating to raw grain beta glucan content, six for malt beta glucan, three affecting beta glucanase activity in green malt and five influencing beta glucanase activity in finished malt. The loci with the greatest effects on these four traits were found on chromosomes 2, 1, 4 and 7 respectively. Additive effects among different loci for the same characteristic were also found. The genetic relationships between the traits studied here and other malting quality characteristics (such as alpha amylase activity, dormancy and malt extract yield) are discussed together with the use of genetic markers identified by quantitative trait locus mapping to enable barley breeders to select for malting quality at an earlier stage of a breeding project than is possible at the time of writing.
Keywords : barley beta breeding enzymic activity gene genetic mapping genetic marker glucan glucanase malt malting prospect quality selection