PDF(Pubmed)
Abstract：
Higher grain yield in high-yielding rice varieties is mostly driven by nitrogen (N) fertilizer applied in abundant amounts leading to increased production cost and environmental pollution. This has fueled the studies on nitrogen use efficiency (NUE) to decrease the N fertilizer application in rice to the possible extent. NUE is a complex physiological trait controlled by multiple genes, but yet to be completely deciphered in rice. With an objective of identifying the promising physiological traits associated with NUE in rice, the performance of 14 rice genotypes was assessed at N0, N50, N100, and N150 for four (two wet and two dry) seasons using agro-morphological, grain yield, flag leaf traits, photosynthetic pigment content, flag leaf gas exchange traits, and chlorophyll fluorescence traits. Furthermore, the data were used to derive various NUE indices to identify the most appropriate indices useful to screen rice genotypes at N50. Results indicate that with the increase in N application, cumulative grain yield increased significantly up to N100 (5.02 t ha-1); however, the increment in grain yield was marginal at N150 (5.09 t ha-1). The mean reduction of grain yield was only 26.66% at N50 ranging from 15.0% to 34.2%. The significant finding of the study is the identification of flag leaf chlorophyll fluorescence traits (Fv/Fm, ΦPSII, ETR, and qP) and Ci associated with grain yield under N50, which can be used to screen N use efficient genotypes in rice under reduced N application. Out of nine NUE indices assessed, NUpE, NUtE, and NUEyield were able to delineate the high-yielding genotypes at N50 and were useful to screen rice under reduced N conditions. Birupa emerged as one of the high yielders under N50, even though it is a moderate yielder at N100 and infers the possibility of cultivating some of the released rice varieties under reduced N inputs. The study indicates the possibility of the existence of promising genetic variability for grain yield under reduced N, the potential of flag leaf chlorophyll fluorescence, and gas exchange traits as physiological markers and best suitable NUE indices to be deployed in rice breeding programs.
摘要：
高产水稻品种的较高谷物产量主要是由大量施用氮（N）肥料导致的，从而导致生产成本增加和环境污染。这推动了氮利用效率（NUE）的研究，以尽可能地减少水稻中的氮肥施用。NUE是由多个基因控制的复杂生理性状,但还没有完全在大米中破译。为了确定与水稻NUE相关的有希望的生理性状，使用农业形态学在N0，N50，N100和N150的四个（两个湿润和两个干燥）季节评估了14种水稻基因型的性能，粮食产量，旗叶性状，光合色素含量，旗叶气体交换性状，和叶绿素荧光性状。此外，这些数据用于得出各种NUE指数，以确定最适合筛选N50水稻基因型的指数。结果表明,随着施氮量的增加,累计粮食产量显著增加至N100(5.02tha-1)；然而，粮食产量的增加在N150(5.09tha-1)是微不足道的。在N50从15.0％到34.2％的范围内，谷物产量的平均降低仅为26.66％。该研究的重要发现是鉴定了旗叶叶绿素荧光性状（Fv/Fm，ΦPSII,ETR,和qP）和Ci与N50下的籽粒产量相关，可用于筛选减少施氮量下水稻的氮素高效基因型。在评估的九个NUE指数中，不，NutE,NUEyield能够描述N50的高产基因型，并可用于在减少的氮条件下筛选水稻。Birupa在N50下成为高产者之一，尽管它在N100下是中等高产者，并推断了在减少氮素投入下种植某些释放的水稻品种的可能性。研究表明，在减少的N下，谷物产量存在有希望的遗传变异性的可能性，旗叶叶绿素荧光的潜力，和气体交换性状作为生理标记，并在水稻育种计划中部署最佳的NUE指数。
