Genetic characterisation, expression and association of quality traits and grain texture in barley (Hordeum vulgare L.)

Grain texture defines the structural component of barley and can be quantified by measuring endosperm hardness and grain density. Both components impact on important grain quality traits, in particular water-uptake efficiency, steeping, malt-extract potential, pearling efficiency, milling efficiency, digestibility, and grain appearance. Grain composition, grain size, grain morphology are traits found to impact the expression of endosperm hardness and grain density. However, little is known about the genomic regions that are directly associated with the expression of grain texture and how these regions may be employed to improve grain quality. A combination of small-scale phenotyping tools, consensus maps, proteomics, and genomics will aid in understanding how grain texture is associated with barley processing and malt-quality related traits. This review highlights the interactions between endosperm hardness, grain density, grain size traits, and malt-quality. For grain texture it is clear that even when all the allelic variations at the Hardness locus have been fully described, there will remain a need to understand the pleiotropic effects on grain texture of a range of other gene loci that are currently considered to be important in physical grain size or phenology.