Characterization of malting barley cultivars with more or less stable grain protein content under varying environmental conditions

The grain protein content (GPC) in barley is influenced to a high degree by the environment and this may cause problems if the barley is intended for malt. Barley used for malt should have a GPC not exceeding 11.5% under any environmental condition. It is, therefore, important to breed for cultivars with low and less environmentally influenced GPC. In a 2-year field experiment seven spring barley (Hordeum vulgare L.) cultivars, with varying GPC stability, were grown at two or three nitrogen application rates, respectively, to determine the differences in leaf area development, N-uptake, yield components, GPC and GPC stability. The time course of leaf area index was followed by measuring light transmission and light reflectance. Total shoot N and biomass and yield components were determined by sub-sampling an area of 3×0.25 m⁻² at heading and at maturity. No clear differences were observed in leaf area development between cultivars with low or high GPC stability, but two of the three stable cultivars showed an earlier reduction of the leaf area and less variance in leaf area index during grain filling. Cultivars with low GPC stability tended to be late, had more biomass accumulated at heading, a larger number of ears per m², and a higher yield and a lower GPC than more sensitive cultivars. From the results of a factor analysis an ideotype for low and stable GPC is postulated. This type is characterized by late heading, many tillers and many seeds per ear. It is suggested that breeding for a prolonged vegetative period would reduce the environmental effects on GPC.