Understanding the genetic bases of modification

Abstract

The proportion and degree of starch, protein and cell wall modification during malting are critical in determining the quality of the final product. While high levels of cell wall modification are desirable to prevent filtration problems, only partial degradation of protein is required. The relationship between cell wall and protein modification is complex with numerous genes likely to be involved. A number of commonly measured traits give an indication of the level of modification. Free amino nitrogen (FAN), Kolbach Index (KI) and soluble protein (SP) are used as indicators of the level of modification of the proteins, while wort -glucan (WBG) and wort viscosity indicate the level of modification of the cell walls. The Australian National Barley Molecular Marker Program (NBMMP) has investigated these traits using a number of Australian mapping populations. Due to the complex relationship between protein and carbohydrate modification this information will not be useful to barley breeders unless knowledge of how and why these regions are influencing modification is known. This paper investigates the regions found to be associated with modification related traits and in doing so aims to gain a greater understanding of the processes involved in modification.