ACCUMULATION OF DRY-MATTER AND NITROGEN IN LOW PROTEIN BARLEY CV KARL AND ITS OFFSPRINGS

In Japan, protein content of malting barley is required to be between 9.5% and 11.5% by brewing industry, but the farmer's product of dominant cultivars often shows more than the upper limit of the range. Therefore, it is important to develop cultivars with a low protein content in barley breeding. In this paper the succesive changes of the characteristics relating to grain nitrogen accumulation were studied in the six rowed low-protein malting barley cv. Karl, together with its two rowed offsprings Daikei HC-1 and Daikei HC-2. The rate of increase of grain dry matter exhibits significant changes during the ripening period. Therefore the period was divided into three phases, lag phase (LP), linear increase phase (LIP) and late filling phase (LFP) (Fig. 1). The ratio (dN/dW) of grain nitrogen increase (dN) to grain dry matter increase (dW) was higher in the LFP than in the LIP. In Karl, the dN/dW was relatively low both in the LIP and LFP and the values of dN and dW were considerably low during the LFP (Table 2). Consequently, at maturity, the grain nitrogen percentage in Karl was 0.5% lower than that in Misato Golden, a popular malting barley cultivar. On the other hand, Daikei HC-1 and Daikei HC-2 showed a grain nitrogen percentage intermediate between that of Karl and Misato Golden (Table 3). The values of the ratio dN/dW in these lines were lower in the LIP compared with Misato Golden, but equivalent to or higher than those of Misato Golden in the LFP (Table 2). It is considered that for these lines the longer period of LIP resulted in the decrease of the grain nitrogen percentage. During the ripening period, the nitrogen percentage of the leaves least decreased in Karl among the materials (Fig. 2). The nitrogen percentage of the flag leaf of harvested plants was 1.3% or higher in Karl than in the other materials (Table 3). It is suggested that the lower decrease of the nitrogen n percentage of the leaves during the ripening period was related to the low dN/dW ratio in Karl. Selection for a high nitrogen content of the leaves may be useful for breeding low-protein malting barley. Since no clear differences in the protease activity of the leaves were observed among four materials, the differences in the protease activities can not account for the varietal difference in the nitrogen content of the leaves. Further studies should be carried out to analyse the factor(s) responsible for the lower reduction of the nitrogen content of the leaves in Karl.