【作者】 潘俊峰；

【导师】 崔克辉；

【作者基本信息】 华中农业大学 ， 植物生理学， 2010， 博士

【摘要】 水稻茎鞘中储藏的非结构性碳水化合物(NSC)对产量形成,特别是对水稻库的活性和缓冲逆境造成的同化物不足所导致的产量下降具有重要意义。氮作为植物生长发育的重要营养元素之一,其对水稻源-库-流特征具有重要的调控作用。然而,不同供氮水平下水稻源-库-流特征对茎鞘NSC积累转运及产量形成的影响,以及其遗传基础仍然不清楚。本研究的目的在于：(1)明确氮素和水稻源库流特征对茎鞘NSC积累转运上的影响以及各性状与产量形成的关系；(2)研究水稻茎鞘NSC积累转运与株高、库容量的关系；(3)检测控制水稻茎鞘NSC积累转运相关性状进行QTL,并对两个重要的QTLs进行了初步的功能验证,探讨茎鞘NSC转运与产量关系的遗传基础。期望本研究结果为水稻高产性状的遗传改良,筛选、培育高产水稻品种等后续研究提供依据。本研究利用大田和盆栽试验进行相关研究,已取得的主要研究结果如下：1)以来源于珍汕97与明恢63的重组自交系(RIL)家系(46个家系)为研究材料,在大田条件下设置二个氮水平(低氮0 kg N hm-2和正常氮130kgNhm-2),以源、库、流相关性状为研究对象,阐明茎鞘中NSC对产量形成的机理,以及源库关系对NSC积累转运的影响。结果发现：低氮条件下,抽穗期茎鞘中NSC的浓度(CNSC at heading)、积累量(TMNSC at heading)、茎鞘NSC的表观转运量(ATMNSC)和NSC对产量的表观贡献率(ACNSC)均显著的高于正常氮水平,而NSC的表观转运率(ARNSC)在不同氮处理之间没有显著差异。在两个氮水平下ATMNSC分别与籽粒产量、千粒重和ACNSC呈显著的正相关；而ARNSC与收获指数和ACNSC显著相关。在两个氮水平下,抽穗期叶面积对产量的贡献均高于ATMNSC。通径分析表明,与正常氮水平相比低氮条件下ATMNSC对籽粒产量具有较大的直接效应；抽穗期TMNSC、穗颈小维管束数量(SVB)对ATMNSC均具有较大的正向效应；SVB和每平方米颖花数对ARNSC均具有较大的正向效应,而大维管束数目(LVB)对其效应为负；抽穗期TMNSC和SVB对ACNSC均具有正向效应。本研究中,低氮处理增加了茎鞘NSC的积累,并促进其向籽粒的转运和对产量的贡献,NSC对产量的表观贡献率为0.71%-28.44%,平均为13.09%,而正常氮水平下为0.96%-15.30%,平均为9.53%；而源、库、流性状对茎鞘NSC转运及其对产量形成的贡献,受到基因型与供氮水平的协同调控。2)在两个氮水平下(低氮0 kg N hm-2和正常氮130kgNhm-2)研究不同库容量家系茎鞘中NSC积累和转运特征,结果表明：抽穗期茎鞘中NSC的积累量与库容量呈极显著的线性正相关。随着水稻家系库容量的增大,水稻NSC的转运量(需求)也相应增加；且库容量越大,NSC的转运量增加幅度越大,在低氮条件下更为明显。穗茎组织特征在两个氮水平下均与库容量呈显著或者极显著的线性相关。在正常氮水平下,随着穗颈直径、大小维管束的增加,NSC的转运量呈增加的趋势,且线性相关达到显著水平,低氮水平下这种关系不明显；与正常氮水平相比,低氮处理明显促进茎鞘NSC向籽粒的转运。3)以株高为分类依据的研究表明：随着株高的增加,抽穗期茎鞘中NSC的积累量呈先增加后降低的变化,而水稻植株茎鞘中NSC的表观转运率和干物质的输出率均随株高的增加而降低。茎鞘中NSC的表观转运量和干物质的输出量随着株高的增加呈二次曲线线变化,抽穗期每株叶面积与茎鞘NSC输出量的变化趋势一致。当株高在115cm左右时,同化物(干物质与NSC)的输出量达到峰值。本研究结果说明,株高为115cm时,抽穗期茎鞘作为籽粒灌浆的临时“源”分别与植株叶面积、NSC的表观转运量及产量均处在峰值范围,该阈值可为育种实践提供理论参考。4)以超级杂交稻两优培九,常规籼稻扬稻6号和热带籼稻IR64为材料,以主茎上部三个伸长节间与相应叶鞘为对象,研究低氮和高氮水平下水稻不同节间非NSC的变化特征及其与产量的关系。水稻生长发育后期,倒一叶鞘中NSC含量变化受到氮影响较小,NSC含量在小于135mg g-1的范围内变动。在水稻抽穗至籽粒灌浆期间,不同品种倒二、倒三节间与相应叶鞘中NSC的含量均呈先增加后降低的变化,以上组织NSC含量的峰值受到不同氮水平的影响；其中倒三节间中NSC含量的动态变化受氮肥影响最大,其次为倒三叶鞘、倒二节间和倒二叶鞘。不同品种之间,两优培九节间和叶鞘中NSC的含量比常规品种高,并对氮肥处理较敏感；低氮处理增加了扬稻6号倒二节间和叶鞘中NSC的含量和输出量。叶源和库容较小的品种(IR64)茎鞘中NSC含量的变化受氮肥处理影响较小。上部三个节间和叶鞘中NSC含量的变化存在基因型差异；不同氮肥处理显著影响倒二、倒三节间及相应叶鞘中NSC含量的动态变化,杂交稻的表现更为明显；倒二叶鞘中NSC含量的变化与产量形成密切相关。5)在两个氮水平下(正常氮和低氮)检测茎鞘中NSC积累和转运、产量及其构成因子等9个性状的QTLs,结果显示：抽穗期共检测到6个控制茎鞘NSC积累的主效QTL,分别位于第1、6(2个)、7(2个)和11染色体上,正常氮水平下三个累积贡献率为54.29%,增效等位基因均来自珍汕97；低氮水平下三个主要效QTL的累计贡献率为50.35%。检测到的5个NSC转运率QTL均位于第5、10和11染色体上,正常氮水平下2个累计贡献率为20.37%；低氮条件下3个QTL累积贡献率为42.49%。检测到NSC转运量的QTL在正常和低氮水平下的累积贡献率分别为47.79%和46.38%。在两个氮水平下共检测到到66个具有显著加性效应的QTLs,其中控制6个性状的QTLs在两个氮水平下均被检测到处在相同或邻近区段,其他占总检测数量76%的QTLs在不同的氮水平下均特异性表达。在第1染色体上R753附近来自珍汕97的等位基因对抽穗期NSC的积累量、NSC表观转运量和千粒重均有增效作用；在第5染色体RG360-R3166区间来自珍汕97的等位基因具有增加NSC表观转运率、表观转运量和千粒重的作用,这一发现为性状间的相关提供了重要的遗传解释。6)在重组自交系群体中,筛选重要农艺性状(抽穗期、库容量、抽穗期叶面积和株高)一致的三个家系,包括R91、R156和R201,前两者分别包含与产量性状和NSC转运相关的分子标记位点RG360-R3166和G359-R753-C161,而R201不含有以上分子标记片段。R91与R156的产量分别比R201高49%和70%,收获指数分别比R201高55%和67%,而成熟期R201残留在茎鞘中的NSC的量(g pot-1)为28.6g pot-1,是R91的5.8倍、R156的3.3倍。R91、R156和R201的茎鞘NSC的表观转运率分别为：75%、57%和-5%,对产量的表观贡献分别为：27%、31%和-4%。R201在抽穗后10天至成熟期同化物向籽粒的转运出现障碍,造成大量NSC在茎鞘中积累,这可能是造成产量差异的主要原因。因此,推测目标区段可能包含与糖在库端卸载相关酶的基因或调控因子。更多还原

【Abstract】 Generally, assimilates for filling grains in cereals are supplied concurrently from two sources:current assimilates in photosynthetic leaves during the grain filling duration and reserves in stems (leaf sheaths and culms) accumulated before heading. In rice, the apparent contribution of non-structural carbohydrates (NSC) in stems to final grain yield has been estimated at 30% under normal condition. A large amount of carbohydrate in stems at heading stage can play an important role in raising sink activity, improving lodging resistance and buffering the yield loss under unfavorable conditions. Nitrogen is considered to be one of the most important macronutrient for rice production, and an amount of nitrogen application can affect markedly characters of source-sink-flow in rice. However, it is poorly understood that genotypes differences and genetics analysis of non-structural carbohydrates accumulation and recombination in rice under different nitrogen conditions.The objectives of this study were:1) to study relationships of non-structural carbohydrates accumulation and translocation with yield formation and effects of source-sink-flow characters in rice recombinant inbred lines under two nitrogen levels,2) to examine a difference in NSC accumulation and translocation in rice lines with different sink content under two nitrogen conditions; 3) to examine the genotypic variations in NSC accumulation and translocation in rice lines with different plant height under two nitrogen conditions; 4) to compare the effects of nitrogen fertilizer on the contents of non-structural carbohydrate at different internodes in different rice verities,5) to understand the genetic basis of relationships of non-structural carbohydrates accumulation and translocation with yield formation in rice under the two nitrogen applications, and 6) to identify two new locus responsible for increased grain weight and NSC translocation and to elucidate its physiological function to understand how to improve potential yield in rice. In this study, field and pot experiments were conducted. The following results were obtained:(1) Stem non-structural carbohydrates (NSC) and its relationships with yield formation were investigated for two years under low (LN) and normal nitrogen (NN), using 46 recombinant inbred lines from Zhenshan 97 x Minghui 63. Concentration of NSC (CNSC) and total mass of NSC in stem (TMNSC) at heading, apparent transferred mass of NSC (ATMNSC) and apparent contribution of transferred NSC to grain yield (ACNSC) were larger under LN compared with those under NN, respectively, however, there was no significant difference in apparent ratio of transferred NSC from stems to grains (ARNSC). ATMNSC positively correlated with grain yield,1000-grain weight, and ACNSC under both nitrogen levels, while ARNSC markedly correlated with harvest index and ACNSC.Leaf area had more contributions to grain yield compared with ATMNSC under LN and NN. ATMNSC had larger direct effects grain yield under LN than that under NN. For ATMNSC, TMNSC at heading, small vascular bundles (SVB) and spikelets per m2 under LN had positive direct effects. For ARNSC, SVB and spikelets per m2 under LN had larger and positive direct effects, and large vascular bundles had negative direct effects. For ACNSC, TMNSC at heading and SVB under LN had positive direct effects. In brief, low nitrogen supply increased stem NSC accumulation and translocation to developing grains. For example, apparent contribution of transferred NSC to grain yield (ACNSC) was higher under LN, ranging from 0.71% to 28.44% with mean of 13.09%, versus from 0.96% to 15.30% with mean of 9.53% under NN. Characters of source-sink-flow system had different effects on NSC translocation and contribution to yield formation, depending on genotypes and nitrogen levels.(2) In this study, sink content (SC) showed an abundant variation in RI lines, and 6 SC types of rice were clustered by SPSS soft ware. SC minimum A-type and maximum F-type was 388g m-2 and 887g m-2 under normal nitrogen condition, respectively. Effect of nitrogen levels on SC was significant. SC was significantly decreased under low nitrogen condition. RI lines with larger SC had higher NSC accumulation in stems at heading, higher ratio of NSC translocation and higher transferred mass of NSC during grain filling. The pattern of change in dry matter showed a similar trend with NSC in stem. As sink increased, dry matter and NSC translocation in stem increased. It indicted that the activity of NSC metabolism in stem can be regulated by SC. However, NSC residues in stem at maturity had no significant differences under all SC types. Apparent contribution of transferred NSC to grain yield was increased under low nitrogen condition. Apparent contribution of transferred NSC to grain yield showed decreasing, when SC was less than 730g m-2 under normal nitrogen condition. ACNSC show increasing trend, when SC was over 730g m-2. Under normal nitrogen condition, apparent contribution of transferred NSC and dry matter to grain yield in A-type had higher than that in C-type by about 3.73% and 8.69%, respectively. When SC was over 730g m-2, F-type had higher than that in C-type by about 2.13% and 6.59%, respectively.(3) To understand the phenotypic variation of nonstructural carbohydrate (NSC) accumulation in rice culms and leaf sheaths and its relationship with yield formation during grain filling period under two nitrogen conditions; Three rice verities: Liangyoupeijiu (indica hybrid variety), Yangdao 6 (indica inbred variety) and IR64 (tropical indica variety), were grown in pots under two nitrogen treatments. In this study, upper three internodes on the main stem per plant were divided into six parts of the peduncle, the penultimate internode, the third internode, flag leaf sheath,-2 leaf sheath and -3 leaf sheath. NSC concentration was measured at different parts in stems. The NSC concentration was always less than 135mg g-1 at the peduncle, and it is no sensitive for nitrogen treatments. The results showed that the peduncle maybe play an important role in transporting of assimilates. The penultimate internodes, the third internodes and corresponding sheaths, as mainly NSC storage organ before heading, were affected by nitrogen treatments in NSC concentration, especially the top value of NSC concentration at different organs. The NSC concentration of third internodes was most sensitive for nitrogen treatments among of different organs. Otherwise, Liangyoupeijiu had the higher NSC concentration than inbred varieties in this study, but it is more sensitive than inbred varieties. On the other hand, NSC concentration is not sensitive for nitrogen treatments in IR64, but this part of NSC in stems is very important to grain yield development, especially to maintaining grain filling percentage. The results indicate that varieties in different genetic backgrounds showed different changes under different nitrogen conditions, and it is the main reason that genotypic variation for stem NSC in response to nitrogen supply. Carbon remobilization in the penultimate internode and -2 leaf sheath played an important role in grain yield formation.(4) As plant height increased. NSC accumulation at heading and at maturity show the increasing at first then decreasing, and C distribution in structural carbohydrates increased according to vascular bundle characters in stem. As plant height increased, ratio of NSC translocation and dry matter showed the decreasing trend, while apparent transferred mass of NSC showed that increasing at first then decreasing. The change of leaf area at heading showed a similar trend with apparent transferred mass of NSC as plant height increased. When plant height was 115cm, apparent transferred mass of NSC arrived at the top value. However, apparent contribution of transferred NSC to grain yield showed decreasing as plant height increased. It suggested that leaf source, stem source and assimalition matter (dry matter and NSC) translocation were concordant at 115cm (plant height).(5) To understand the genetic basis of relationships of non-structural carbohydrates accumulation and translocation in rice culms and leaf sheaths with yield formation under two nitrogen levels, quantitative trait loci (QTLs) for 9 related traits were mapped with a RIL (recombinant inbred line) population derived from a cross between Zhenshan97 (indica var.) and Minghui63 (indica var.) under field environment. Six QTLs affecting NSC accumulation at heading were detected on chromosome 1,6 (2 locus),7 (2 locus) and 11. The three QTLs were identified under normal nitrogen condition, accounting for explaining 54.29% of the total phenotypic variation. The Zhenshan97 alleles increased the trait value at all. Another three QTLs were detected under low nitrogen condition, accounting for 50.35% of the total variation. The numbers of QTLs for ARNSC under normal and low nitrogen conditions were two and three four, respectively. The amounts of total variation explained by the ARNSC QTL were 20.37% and 42.49% under normal and low nitrogen conditions, respectively. Under normal nitrogen condition, a total of five QTLs were detected for, jointly explaining 47.79% of the total variation, while those explained by the three QTL were 19.37%,14.42% and 12.59% under low nitrogen condition. The Zhenshan97 allele increased NSC accumulation at heading stage, ATMNSC and at the region near R753 on chromosome 1. Another QTL at the region RG360-R3166 on chromosome 5 increased ARNSC, ATMNSC and 1000-grain weight. Zhenshan97 contributed the allele at QTLs. In all, the two regions, i.e., G359-R753-C161 and RG360-R3166 provide a genetic explanation for the close correlations between NSC translocation and grain yield traits.(6) Two pleiotropic QTLs for grain weight and NSC translocation in stem were localized on a rice genetic map under different nitrogen conditions. QTLs were detected on chromosome 1 (G359-R753-C161) and 5 (RG360-R3166) respectively, and two loci all explained large phenotypic variation from Zhenshan 97. Based on the above results, we selected two lines from RILs including plelotropic QTLs (R91 and R156), and a line didn’t include two loci (R201). QTLs functions were further confirmed in a plot experiment. There were no significant differences in leaf area at heading, total biomass at maturity and sink capability among of three lines. The concentration of soluble sugars and starch in stems showed increasing trends among of three lines early reproductive stage, but there were significant differences in changes of from 10 days after heading to maturity. For example, the soluble sugars and starch maintain increasing trend in R201, but the others all (R91 and R156) showed significantly decreasing. These results suggest that NSC translocation from stems to grains is baffled during late grain filling stage in R201. Further studying found that there were significant differences in soluble sugars concentration in branches among three lines, and showed higher soluble sugars concentration in R201 than that in others, suggesting that NSC remobilized from stems to rachis branches is normal to R201. However, R201 re-accumulate soluble sugars and starch in stems at late grain filling stage. It suggests that R201 can’t normally unload NSC from branches to grains, consequently resulting in NSC re-accumulation in stems. We forejudge that either G359-R753-C161 on chromosome 1 or RG360-R3166 chromosome 5 may include sucrose synthase gene which can regulate sugar unloading in grains after heading 10 days. So the two chromosomal regions will show remarkable value in map-based cloning and breeding programs using a marker assisted approach. Two loci can be transferred to other large sink breeding materials, it may significantly improve grain yield.The results of this study showed that stored NSC in stem play an important role in yield formation, especially in super rice varieties. So studying relationships of non-structural carbohydrates accumulation and translocation with yield formation, and its genetic mechanisms under different nitrogen conditions will help to understating yield formation mechanism, especially under low nitrogen stress. As the additive effects are harmonic among QTLs affecting yield trait and NSC translocation, the favored allele (from ZS97 in this study) will be transferred to other breeding materials to validate the effect of molecular assisted selection (MAS), targeting on the large chromosomal segment, as a candidate MAS strategy. The best way is to combine breeding programs and crop management strategies depending on the improvement of carbohydrate storage and translocation to grains. It will be an important significance for increasing rice yield potential.更多还原