| Recently, the investigation on increasing the rice nutrient utilization efficiency by upgrading the cultivation system and exploring the genotypic potential has been emphasized. We studied yield performance and its physiological characters, as well as nutrient utilization traits of high yielding rice varieties through different treatments, including cultivation (conversional tillage and no tillage), seeding (transplanting and direct seeding) and fertilizer application strategies. Moreover, the QTL analysis of nutrient utilization efficiency was analyzed using a RIL population. In addition, proteomic analysis of the high yielding rice exposed to the different nitrogen levels was also conducted. The main results are as follows:1. There was a large variation in grain yield for the two super-rice varieties among locations and years. The realization of high yield potential for the two varieties was closely related to the improved sink size, i.e. more panicles per m2 or grains per panicle. Stem and leaf biomass was mainly accumulated during tillering to heading stages, and showed slow decline at grain-filling stage. Meanwhile, some photosynthetic characters, including net photosynthesis rate (Pn), leaf area index (LAI), specific leaf area (SLA), fluorescence parameter (maximum quantum yield of PSII, Fv/Fm), chlorophyll content (expressed as SPAD value), as well as nutrient (N, P, K) uptake were also measured to determine their variations over genotypes and environments and their relationships with grain yield. Although there were significant differences between years or locations for most measurements, SLA at tillering and heading stages, Fv/Fm and LAI at heading stage, stem biomass at heading and maturity stages, and leaf nitrogen concentration at tillering and heading stages remained little changed, indicating their possible applications as selectable characters in breeding programs. It was also found that stem nitrogen accumulation at tillering stage is one of the most important and stable traits for high yield formation.2. The influence of no tillage (NT) on leaf photosynthesis nutrient uptake, remobilization and partitioning in rice plants was determined. Te experiments with treatments NT and conventional tillage/plough follow (CT) were carried out at two locations (Jiaxing and Hangzhou) for two years (2005 and 2006). Grain yield was constantly lower in Jiaxing, but slightly higher in Hangzhou for NT cultivation than for conventional one in the both two years. In comparison with the conventional cultivation, no-tillage cultivation had less biomass accumulation before heading and higher capacity of matter production during grain filling. A significantly higher leaf net photosynthetic rate was observed for the plants under NT than for those under CT. A fluorescence parameter, Fv/Fm did not show any difference between the two cultivations. The effect of cultivation methods on transpiration rate (Tr) and SPAD value was dependent on the location and year. N concentrations in stem and panicle in no tillage (NT) were lower than those in conventional tillage (CT). However, leaf N concentration was relatively higher in NT plants after heading stage. No significant difference was found in P concentration between two tillage treatments before heading stage. However, at mature stage, NT had higher P concentration in panicle. NT plants had higher K concentrations in both leaf and stem than CT ones before heading stage. At maturity stages, the difference about the nutrient accumulation between the two tillage treatments varied with plant organs. NT plants had significantly higher stem and leaf nutrient accumulations than CT ones at late stages, while at early stage, the difference between the two tillage treatments varied with location and year. Both N and K harvest index (NHI and KHI) was significantly higher in NT plants than in CT plants, but the difference between the two tillage treatments in P harvest index (PHI) was changeable over year and location. NT plants had lower nutrient utilization efficiency in comparison with CT plants.3. The responses of six super-rice cultivars to two cultivation methods, transplanting (TP) and direct-sowing was investigated. It was shown that grain weight and tillers per plant at early growth stage, maximum quantum yield of PSII (Fv/Fm) and transpiration rate (Tr) was higher in DS than in TP, while grain yield, panicles per m2, grain-setting percentage, panicle weight, net photosynthetic rate (Pn) and stomatal conductance (Cond) were just opposite. Meanwhile, little difference was found in grains per panicle, stem (shoot) and leaf weight between the two planting methods. The responses of plant growth and physiological traits to planting method differed greatly among the 6 cultivars. It was found that the higher yield of Chunyou 58 was associated with more panicles per m2 and grains per panicle in both planting methods than the other cultivars. Chouyou 58 and Yongyou 6 had the highest and lowest panicle biomass in the both planting methods, while Chunyou 58 had the highest Pn value in TP and Yongyou 6 had the lowest Pn value in DS. Significant genotypic difference were found in the rice mill, appearance and cooking qualities. However, Effects of planting method on the nutritional harvest index, nutritional efficiency and grain cooking qualities (excluding Gel consistency) differed between the different environments, as the three way interactions were significant. For both nutrient harvest index and utilization efficiency, large genotypic differences could be also found. Rice chalkiness, transparency, gel consistency, amylase and protein contents were all significantly correlated with N, P and K nutrient traits.4. Field experiments were conducted in Jiaxing (2006), Xiaoshan (2007), Hangzhou (2008), using Xiuyou 5 and Xiuyou 5, and Yongyou 6 and Chunyou 58, respectively, in order to investigate the effect of different fertilizer applications (Fl: control; F2:-10% amount of fertilizer; F3:+10% panicle topdressing fertilizer; F4:-10% amount of fertilizer with +10% panicle topdressing fertilizer) on yield, physiological response and nutritional utilization of high yielding rice. The result showed that yield were slightly decreased or kept consistent in F2 and F4, and increased in F3, compared with F1. Panicles per m2 and grains per panicle in F2 and F4 were smaller than that in F1, while little difference was found between F1 and F3. Grain filling percentage was improved in F2, F3 and F4 for some extent, while grain weight was found no difference among the treatments. It is suggested that the sink capacity was weaken by the decreased early fertilizer and compensated by the increased topdressing fertilizer. Early stem biomass accumulation were related to the fertilizer directly, with F4 was significantly smaller than F1. For PI and HS, no significant difference was found among the treatments suggesting that there is higher biomass turnover efficiency in F4 than in F1. Differences in SPAD value and net photosynthetic rate were only found at heading stage, with F3 being significantly higher than F1. Lower early stem nutrient concentration and accumulation were found in F4, but little difference in leaf, compared with F1. The treatments of F2, F3 and F4 were significantly increased in NUE, but for NHI, PUE, PHI, KUE and KHI, the influence of the treatments varied with environment and genotype.5. QTL mapping for nutrient utilization traits, including NUE, PUE, KUE, NHI, PHI and KHI were conducted in two year (2007 and 2008) using a population of 247 RILs derived from a super hybrid rice cross of "ZS97 X MY46". The result showed that the tremendous transgressive segregation for nutrient utilization traits was observed in the population and the frequencies of these traits were approximately normally distributed. A total of 7 major QTLs and 6 pairs epistatic effect QTL distributed on all the chromosomes, except 4,7 and 9, were detected in both years. Only QTLs (qNUE 5-23 and qPUE1-5) were found for NUE and PUE, respectively. Two, two and one QTLs for NHI, PHI and KHI were also detected, respectively. Phenotypic variance explained by a single QTL ranging from 3.36% to 7.27%. QTLs controlling PUE and NHI were closely located, indicating the linkage of the nitrogen and phosphors utilization.6. In order to understand molecular mechanisms of the difference in NUE of rice, a systematic proteomic study was carried out to investigate N stress-responsive proteins in two high yielding rice cultivars differing in NUE. Four leaf-old seedlings were treated with N-free solution for 12 h,3 d and 7 d. Total proteins of leaves were extracted and separated by two-dimensional gel electrophoresis. Although more than 1000 protein spots were reproducibly detected, only a very small proportion of spots showed differential expression, including 10 and 24 up-regulated,2 and 12 down-regulated in the two cultivars Chunyou 58 and Yongyou 6, respectively. It was indicated that relatively simply biochemical pathways maybe involved with NUE, thus it should be efficiently manipulated. Mass spectrometry based peptide mass fingerprinting (PMF) procedure identified 31 protein spots. Six stress-induced proteins were found, including DegP2, harpin binding proteins, Heat shock-related proteins, glutathione S-transferase GSTF14, Fibrillin-like protein and Glyceraldehyde-3-phosphate dehydrogenase. Apart from the stress related proteins, the other differential proteins identified were mainly these involved in the regulation of the main leaf biological function, photosynthesis metabolism, such as Rubisco activase, RuBisCo large subunit, etc. The study also detected two novel proteins, harpin binding protein and oryzains gamma precursor. The current study gives new insights into N stress response and theoretical bases for improving NUE of rice.
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