Opportunities for increased nitrogen-use efficiency from improved lowland rice germplasm

Growth of Three Rice (Oryza sativaL.) Cultivars under Upland Conditions with Different Levels of Water Supply

“…This also led to comparable cumulative amounts of radiation interception whereas radiation-use effi ciency was similar between RU and FL (data not shown). Longer growth duration, particularly in the vegetative stage, enhances the amount of N uptake and hence dry matter production in lowland rice (Ladha et al, 1996;Inthapanya et al, 2000). The present study supports these observations under favorable upland conditions with adequate and frequent water supply.…”

“…Cultivars that could maintain water and nutrient uptake under less moist soils may produce larger amounts of dry matter, and these cultivars would thus become important as the water supply decreases. Dry matter production, one of the major determinants of grain yield, would result from resource acquisition (e.g., nitrogen (N) uptake and radiation absorption) and the conversion of these resources into plant biomass (Ladha et al, 1996). Phenological development (Yun et al, 1997), and plant morphological features such as tillering, leaf area expansion, and rooting (Kondo et al, 2003) may differ between upland and lowland cultivars, and between upland and lowland conditions.…”

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

“…The definitions of N use efficiency vary with the purpose of individual studies (Ladha et al, 1998;Fageria et al, 2008). In this study, physiological N use efficiency (PNUE) for shoot biomass production was calculated as follows: PNUE = aboveground dry weight/aboveground N content Statistical analysis and cluster analysis were conducted by using JMP 8 software (SAS Institute, Cary, NC, USA).…”

Four Decades of Breeding for Varietal Improvement of Irrigated Lowland Rice in the International Rice Research Institute

“…The poor grain filling of NPT lines was probably due to lack of apical dominance within a panicle (Yamagishi et aI., 1996), compact arrangement of spikelets on the panicle (Khush and Peng, 1996), a limited number of large vascular bundles for assimilate transport (S. Akita, personal comm. ), and source limitation due to early leaf senescence (Ladha et al, 1998). The NPT lines are also susceptible to diseases and insects and have poor grain quality.…”