title: Physiological Mechanisms Underlying the High-Grain Yield and High-Nitrogen Use Efficiency of Elite Rice Varieties under a Low Rate of Nitrogen Application in China.
abstract: Selecting rice varieties with a high nitrogen (N) use efficiency (NUE) is the best approach to reduce N fertilizer application in rice production and is one of the objectives of the Green Super Rice (GSR) Project in China. However, the performance of elite candidate GSR varieties under low N supply remains unclear. In the present study, differences in the grain yield and NUE of 13 and 14 candidate varieties with two controls were determined at a N rate of 100 kg ha(-1) in field experiments in 2014 and 2015, respectively. The grain yield for all of the rice varieties ranged from 8.67 to 11.09 t ha(-1), except for a japonica rice variety YG29, which had a grain yield of 6.42 t ha(-1). HY549 and YY4949 produced the highest grain yield, reflecting a higher biomass production and harvest index in 2014 and 2015, respectively. Total N uptake at maturity (TNPM) ranged from 144 to 210 kg ha(-1), while the nitrogen use efficiency for grain production (NUEg) ranged from 35.2 to 62.0 kg kg(-1). Both TNPM and NUEg showed a significant quadratic correlation with grain yield, indicating that it is possible to obtain high grain yield and NUEg with the reduction of TNPM. The correlation between N-related parameters and yield-related traits suggests that promoting pre-heading growth could increase TNPM, while high biomass accumulation during the grain filling period and large panicles are important for a higher NUEg. In addition, there were significant and negative correlations between the NUEg and N concentrations in leaf, stem, and grain tissues at maturity. Further improvements in NUEg require a reduction in the stem N concentration but not the leaf N concentration. The daily grain yield was the only parameter that significantly and positively correlated with both TNPMand NUEg. This study determined variations in the grain yield and NUE of elite candidate GSR rice varieties and provided plant traits that could be used as selection criteria in breeding N-efficient rice varieties.
authors.affiliation: National Key Laboratory of Crop Improvement, Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Lilian
authors.initials: L
authors.lastname: Wu
authors.affiliation: National Key Laboratory of Crop Improvement, Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Shen
authors.initials: S
authors.lastname: Yuan
authors.affiliation: National Key Laboratory of Crop Improvement, Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Liying
authors.initials: L
authors.lastname: Huang
authors.affiliation: National Key Laboratory of Crop Improvement, Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Sun
authors.affiliation: National Key Laboratory of Crop Improvement, Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Guanglong
authors.initials: G
authors.lastname: Zhu
authors.affiliation: National Key Laboratory of Crop Improvement, Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Guohui
authors.initials: G
authors.lastname: Li
authors.affiliation: National Key Laboratory of Crop Improvement, Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Shah
authors.initials: S
authors.lastname: Fahad
authors.affiliation: National Key Laboratory of Crop Improvement, Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Shaobing
authors.initials: S
authors.lastname: Peng
authors.affiliation: National Key Laboratory of Crop Improvement, Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
keywords: Green Super Rice; daily grain yield; grain yield; nitrogen use efficiency