Aleurone and subaleurone morphology in native Australian wild cereal relatives

The pericarp and aleurone layer of cereal grains are associated with the accumulation of anti-nutritional factors, vitamins, high-value proteins and trace elements. Variations in these tissues may be associated with important differences in the nutritional and functional value of cereals as human or animal feeds. Wild crop relatives (WCR) have been successfully utilised in breeding programs to improve agronomic traits such as dwarfism and pest and disease resistance. Australia’s undomesticated grass species (Poaceae) provide a unique and genetically diverse array of WCRs and therefore the grains of 17 Australian WCRs were examined by scanning electron microscopy (SEM). Aleurone of each WCR was compared with that of its nearest domesticated cereal relative, with little significant morphological variation observed to this structure. A novel subaleurone morphology was observed in the Sorghum WCRs which had the appearance of being a very dense protein matrix only sparsely embedded with small starch granules or completely lacking starch granules. Histochemical analysis of a subsample of the specimens confirmed that the described morphology was lacking starch granules and had a proteinaceous matrix. Such morphological variations within Australian wild crop relatives of commercial cereals may provide novel sources of genetic diversity for future grain improvement programs.