NITROGEN ACCUMULATION AND GRAIN PROTEIN-FRACTION OF A LOW-PROTEIN STRAIN IN 2-ROWED BARLEY

Two-rowed low-protein barley Daikei HC-15, which is related to low-protein cultivar Karl, was studied to determine the changes in the percentage of nitrogen in the grain, leaf and stem during ripening period, and the grain protein fraction at maturity. As compared with commercial variety Mikamo Golden, Daikei HC-15 accumulated dry matter equally but less nitrogen in grains during the middle phase of the ripening period (3 -5 weeks after heading). There was 0.5% difference in the grain nitrogen percentage between two genotypes at 5 weeks after heading, but in the last phase of the ripening period (5-7 weeks after heading), the two genotypes similarly accumulated much nitrogen in the grains. In contrast with these genotypes, Karl accumulated less nitrogen during the last phase. At maturity, the Daikei HC-15 grain nitrogen percentage was 0.37% lower than Mikamo Golden and 0.17% higher than Karl. During the middle phase of the ripening period, the nitrogen percentage of laminae decreased less in Daikei HC-15 than in Mikamo Golden, but during the last phase, it decreased considerably in Daikei HC- 15. In Karl, the decrease in the nitrogen percentage of the laminae was the smallest throughout the ripening period. In the protein fraction, Karl showed a markedly lower concentration of hordein than Mikamo Golden. Though Daikei HC-15 also showed a significantly lower hordein concentration than Mikamo Golden, it had a greater proportion of hordein than Karl. It has previously been reported that hordein accumulates in grains during the later stage of the ripening period. It was concluded that the difference in hordein concentration between Daikei HC-15 and Karl was caused by the difference in grain nitrogen accumulation during the last phase of the ripening period.