Genotypic variability in nitrate assimilation in rice
1996
Barlaan, E.A. | Ichii, M.
In nitrate assimilation, reduction of nitrate to ammonia is catalyzed by nitrate reductase (NR) and nitrite reductase (NiR). To determine the activities of these enzymes in rice, 53 cultivars from six varietal groups based on isozyme variations were randomly selected. Seedlings were analyzed in vitro for nitrate reductase activity (NRA) and nitrite reductase activity (NiRA) and nitrate content. Significant differences in NADH-NRA, NADPH-NRA, NiRA, and nitrate content among rice cultivars and six varietal groups were observed. Differences in NRA and NiRA among cultivars within a group were significant for some groups but not so in nitrate content. Among rice genotypes, threefold differences in NADH-NRA and NiRA were found. Based on NADH-NRA, rice genotypes could be classified into three NRA categories-high, moderate, and low. NRA expresses the ability of the plants to use nitrate. Results suggest that certain cultivars and varietal groups were good nitrate assimilators. Cultivars with high NRA were identified. Of the six varietal groups, Groups II, V, and I (indica) and higher NRA than japonica, floating, and deepwater rices. In all cultivars, activity of NADH-NR was higher than that of NADPH-NR. In separate experiments, 14 cultivars with varying NRA levels were evaluated under irrigated lowland conditions. Significant and positive correlations were observed between NRA and grain yield and between NRA and biomass
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