Governing Grain Protein Concentration and Composition in Wheat and Barley: Use of Genetic and Environmental factors

For commercial production of wheat and barley, grain yield (GY), grain protein concentration (GPC) and protein composition are considered important. Genetic (G) and environmental (E) factors are important constraints affecting GPC and protein composition in wheat and barley. This thesis examined the options to govern GPC and protein composition in wheat and barley grain by using G and E factors. The results showed that combination of G and E factors played an important role, more important than single factors solely, to determine GPC, protein composition, accumulation and protein breakdown in wheat and barley grains. Differences in maturation times of wheat and barley plants, due to variation in G and E factors, were found to be a significant factor in determining GPC and protein composition. By governing the maturation times, using different genotypes, N application rates and timings, preand post-anthesis temperature, the options to govern GPC and protein composition increased. Early maturing cultivars, N application at anthesis and high pre-anthesis temperature resulted in high amounts of sodium dodecyl sulphate (SDS)-extractable proteins (TOTE). Late maturing cultivars, N application at spike formation and high post-anthesis temperature resulted in high percentage of SDSunextractable polymers into total polymers (%UPP). Pre-anthesis temperature influenced mainly TOTE, while post-anthesis temperature influenced mainly %UPP. Maturation time was found more important for determining GPC and protein composition at high temperature while at low temperature late nitrogen supply was of higher relevance. Differences in the buildup of TOTE and polymeric proteins were found to initiate from 12 days after anthesis and thereafter the build-up rate pertained throughout the grain maturation period. In barley, breakdown of proteins at malting were found dependent on plant maturation time and GPC i.e. higher breakdown rate at higher GPC. A negative correlation was found between GY and TOTE and between TOTE and %UPP. The results from this thesis help to understand how GPC, protein composition, accumulation and breakdown are governed in wheat and barley by various G and E factors. Moreover, the results may help in creating a simulation based quality model in which both G and E factors can be used to model GPC and protein composition in wheat and barley.