Genetic variations in dry matter production and physiological nitrogen use efficiency in rice (<i>Oryza sativa</i> L.) varieties

Abstract

The objective of this study was to investigate varietal differences in dry matter production and physiological nitrogen use efficiency (PNUE) using a wide range of rice (Oryza sative L.) varieties at an early growth stage. The results provide useful information for breeding suitable varieties for cultivation under conditions of low soil fertility or with reduced fertilizer use for sustainable agriculture. Thirty-one rice varieties were used, and seedlings were grown under 8 nitrogen treatment conditions. The effects of natural variations in embryo and/or endosperm size on initial growth were controlled for by comparing the relative dry weight (RDW) of nitrogen-treated samples and controls. The rice varieties were classified into 5 groups by cluster analysis. Overall, the present study found that there are wide variations in PNUE among varieties with similar levels of RDW under varying nitrogen conditions. Variations in PNUE were greater under lower nitrogen conditions; in contrast, variations in RDW were greater under higher nitrogen conditions. These data, along with those of other studies, indicate differences in nitrogen use efficiency between Indica-and Japonicatypes, upland and lowland varieties, and landraces and improved types.

Genotypic Variation in Nitrogen Uptake during Early Growth among Rice Cultivars under Different Soil Moisture Regimes

“…2), suggesting that N uptake capacity and its utilization efficiency of indica I differ from those of indica II groups． produced inconsistent results regarding the association of PNUE with biomass production. For example, in a study where a variation in PNUE ((dry weight of N treatmentdry weight of non-N control)/(N content of N treatment-N content of non-N control)) among 31 cultivars was examined under varying N conditions, a significant cultivar difference in PNUE was found (Namai et al, 2009), although the definition of PNUE was different from our study. They suggested that the variation reflects the genetic and/or cultural backgrounds of the cultivars employed, including 20 indica and japonica types.…”

Variation in free amino acid profile among some rice (Oryza sativa L.) cultivars

“…Since A/G ratios represent the relative abundance of Asp-derived and Gluderived FAAs in the grains, the difference observed between the two grain types appears to indicate key differences in the manner in which the two rice ecotypes accumulate these free amino acids in their respective endosperms. Rice researchers have identified many fundamental differences between indica and japonica-type rices (Wang et al 1998, N'tanos and Koutroubas 2002, Lon et al 2004, Namai et al 2009). The difference observed in the present study might therefore fit within the broader framework of the indica-japonica dichotomy.…”

Genetic Variations in Dry Matter Production, Nitrogen Uptake, and Nitrogen Use Efficiency in the AA Genome Oryza Species Grown under Different Nitrogen Conditions

“…A previous study revealed a large genotypic difference in NUE among cultivars of O. sativa, and the indica cultivar, Kasalath, showed the highest N sensitivity (Namai et al, 2009). Duan et al (2007) also confirmed that, when NO 3 -were applied together with NH 4 + , cultivars with high NUE showed higher N accumulation, dry matter production, and yield than those with low NUE and suggested that there was a close relationship between NO 3 -application and NUE.…”

“…Currently, there are many reports on the physiological difference between the subspecies of O. sativa. Namai et al (2009) reported that the indica type has higher N sensitivity in the dry matter productivity than the japonica type. In addition, the indica type develops roots more extensively than the japonica type under the LN condition (Namai et al, 2009).…”

“…Namai et al (2009) reported that the indica type has higher N sensitivity in the dry matter productivity than the japonica type. In addition, the indica type develops roots more extensively than the japonica type under the LN condition (Namai et al, 2009). Kubota et al (1992) also showed that the dry matter productivity and N sensitivity at the vegetable stage were higher in O. glaberrima than in O. sativa.…”