Activities of Enzymes for Sucrose-Starch Conversion in Developing Endosperm of Rice and Their Association with Grain Filling in Extra-Heavy Panicle Types

Abstract

Rice cultivars with numerous spikelets per panicle (extra-heavy panicle types) frequently fail to exhibit their high yield potential due to low grain filling. Existing genetic variation in grain filling, however, opens possibilities for genetic improvement for this trait. We studied the correlation between grain filling and the activities of enzymes for sucrose-starch conversion in developing endosperm. The activity of sucrose synthase (EC 2.4.1.13, SuSy) and ADPglucose pyrophosphorylase (EC 2.7.7.27, AGPase), were measured in three extra-heavy panicle types and a standard cultivar grown at two locations under different environmental conditions. The proportions of grains with definite specific gravities and the rate of grain filling were adopted as the parameters related to grain filling. AGPase activity, but not that of SuSy, was consistently correlated to high proportions of high-density grains (specific gravity > 1.20) and high rates of grain growth in spikelets, particularly in those on secondary branches in which low grain filling is the rule. Such correlation was also detected in spikelets on primary branches which generally show better grain filling, but only early stages. Therefore, a high activity of AGPase might contribute to the reduction of the sucrose concentration by accelerating sucrose metabolism at the developing seed, a sink terminus of the phloem. Thus the sink-directed phloem transport of sucrose would be promoted, resulting in improved grain filling of extra-heavy panicle types. SuSy would play some roles in such a cultivar difference in grain filling, but depending on environments.     

Effects of Dry Matter Production,Translocation of Nonstructural Carbohydrates and Nitrogen Application on Grain Filling in Rice Cultivar Takanari,a Cultivar Bearing a Large Number of Spikelets

Abstract

The effects of dry matter production and the remobilization of nonstructural carbohydrates (NSC) on grain filling were investigated using the Indica-based Japonica crossed rice cultivar Takanari, which can bear a large sink. For three years,beginning in 1994, shade treatments were conducted with different nitrogen applications to develop large variations in plant growth. The percentage of ripened spikelets showed the greatest correlation with the total amount of carbohydrate supply per spikelet during 10 to 20 days after heading, calculated by adding the amount of dry matter increase to the amount ofNSC decrease in leaf sheaths and culms during the period. Between the two components, the dry matter increase was more important. The NSC reserve played a role in compensating for the shortage of carbohydrate supply from assimilates after heading and showed a tendency to increase the percentage of ripened spikelets when dry matter production after heading was limited. However, the maximum ratio of compensatory translocation from the NSC reserve was estimated to be only 48%, becauseofsmaller reservoir size compared with the demand. The NSC reserve at heading was not significantly increased by increasing the dry matter production before heading. It was concluded that to increase grain filling ability it is more effective to increase the dry matter production after heading than that before heading. Nitrogen application showed negative effectson the translocation of reserve NSC. It is important to optimize the nitrogen content to maximize the total source of carbohydrate supply.     

Effects of High Temperature on Growth,Yield and Dry-Matter Production of Rice Grown in the Paddy Field

Abstract

The effect of high temperatures on growth, yield and dry-matter production of rice growing in the paddy field was examined during the whole growth period in a temperature gradient chamber (TGC) from 2002 to 2006. Experimental plots, TG1 (control), TG2, TG3 and TG4, were arranged along the temperature gradient (from low to high temperature) in TGC. The mean and maximum air-temperatures in TG4 were 2.0 –3.6ºC and 4.0º7.0ºC higher, respectively, than those in TG1. The plant height was taller and the maximum tillering stage was earlier in TG2, TG3 and TG4 than in TG1. Plant dry weight at maturity in TG2 and TG3 was 12.8?16.4% heavier than that in TG1. In TG4, the increase in the panicle dry weight during the ripening period was smallest and plant dry weight at maturity was 11–16% heavier than that in TG1. The increase in plant dry-matter during the ripening period was smallest in TG4. The decrease in the dry weight of stem and leaf during the ripening period, which represents the amount of assimilate translocation to the panicle, was also larger in TG2-4 than in TG1. The increase in the dry weight of stem in TG2-4 at maturity was also larger than that in TG1. The photosynthetic rate in TG2-4 was up to 35.6% lower than that in TG1 because of the acceleration of leaf senescence. Brown rice yield in TG4 was 6.6?39.1% lower than that in TG1. This yield decline was due to the decrease in the percentage of ripened grains and increase in the percentage of sterile spikelets. The relation between brown rice yield and mean air-temperature during 20 days after heading showed that the brown rice yield declined when mean air-temperature exceeded 28ºC.     

Relationship between Dry Weight at Heading and the Number ofSpikelets on Individual Rice Tillers

Abstract

The objectives of this study were to identify the growth parameters involved in determining the number of spikelets on an individual tiller (ST) and to elucidate how ST is determined in rice (Oryza sativa L.). We examined the correlation of ST with the dry weight (DWT), leaf area (LAT), and the amount of nitrogen (NT) at heading for individual tillers grown under different conditions that were expected to affect spikelet production. In 1999, the japonica rice cultivars “Mineasahi” (short-duration), “Hinohikari” (intermediate-duration), and “Akebono” (long-duration) were transplanted in a paddy field on two different dates (EARLY and LATE). In 2000, Hinohikari was grown under three different treatments (gibberellic acid application, nitrogen topdressing, and thinning of hills at panicle initiation) and without treatment (control). Covariance and partial correlation analyses indicated that ST was positively and essentially correlated with DWT rather than with LAT and NT. The regression of ST on DWT was stable within each cultivar regardless of the treatment, year, tiller order, and number of differentiated spikelets. The slope of the regression was the steepest in the short-duration cultivar. These results suggest that the steep slope is desirable for high-yielding cultivars with large panicles. We conclude that ST is mostly determined by dry matter production of an individual tiller regardless of the number of differentiated spikelets. We present a diagram showing the relationship between dry matter production and the number of differentiated, surviving, and degenerated spikelets on an individual tiller.     

Effect of Top-dressing and Planting Density on the Number of Spikelets and Yield of Rice Cultivated with Nitrogen-free Basal Dressing

Abstract

The effects of nitrogen-free basal dressing (BNo) and top-dressing on the growth and yield of two rice varieties, Akitakomachi and Hitomebore, planted at a standard density (22.2 hills m^?2) and sparse density (16.7 hills m^?2) were examined. The maximum number of stems and the number of panicles per unit area were lower in both BNo plots with a standard planting density (BNo22) and sparse planting density (BNol7) than in the control plot with standard nitrogen dressing and standard planting density (CONT) in both varieties. The number of panicles and spikelets per unit area was lower in both BNo22 and BNo 17 than in CONT, but the number of spikelets per panicle in BNo 17 was significantly higher than that in CONT, although that in BNo22 was not. In BNo22, the percentage of ripened grains and 1,000 grain weight were significantly higher than those in CONT, but in BNo 17, 1,000 grain weight was similar to that in CONT, although the percentage of ripened grains was higher than that in CONT. Grain yield in both BNo22 and BNo 17 was not significantly different from that in CONT, and that in BNo 17 was 660 and 710 g m^?2 in Akitakomachi and Hitomebore, respectively. The leaf area index was lower and crop growth rate was higher in both BNo22 and BNol7 than in CONT at the grain-filling stage. The net assimilation rate and specific leaf weight were significantly higher in BNo22 and BNo 17 than in CONT at the panicle formation and grain-filling stages, respectively. Nitrogen top-dressing at the neck node differentiation stage was found to be very useful for the cultivation of these rice varieties under BNo with sparse planting density in the Tohoku district.     

Morphological Evaluation of the Trace of Grain Detachment in Japonica Rice Cultivars with Different Shattering Habits

Abstract

Seed shattering is an important agronomic trait in rice as it directly affects the yield. Manipulation of the degree of shattering will maximize the yield potential. This study was performed to find an indicator for indirect selection to facilitate the selection of medium-shattering habit in japonica rice breeding. The grain shattering pattern and microscopic morphology of the separation zone on pedicels of five japonica rice cultivars with different shattering habits were compared. Almost all grains were separated between the sterile lemma and rudimentary glume in cultivars with medium-shattering, easily-shattering and very easily-shattering habits. On the other hand, approximately 50% of the grains of the cultivar with hardly-shattering habit were torn off at the bent portion of pedicel. A separation pileus was formed on the terminal of the pedicel. The pileuses were most prominent in cultivars with easily-shattering and very easily-shattering habits, while cultivars with a medium-shattering habit had more flat pileuses than prominent pileuses. Additionally, in the cultivar with a hardly-shattering habit all pileuses were flat. Development of fibrous cell walls on the separation pileus varied with degree of shattering habit. The easier the grain shattered, the poorer was the development of fibrous cell walls. These results strongly suggest that the shape of separation pileus and the development of fibrous cell walls are related to the shattering habit in japonica rice. Additionally, it is highly probable that the medium-shattering habit is characterized by the type of shattering that separates between sterile lemma and rudimentary glume with the flat shape of pileus.     

粳稻穗角和每穗颖花数的遗传分析

 调查了粳稻直立穗品种丙8979与弯曲穗品种C堡杂交组合的P1、P2、F1、F2四个世代（2002年）和P1、P2、F1、F2、F2∶3五个世代(2003年）的穗角和每穗颖花数的表型分布。运用主基因+多基因混合遗传模型和分离世代加不分离世代联合分析的方法，对这两个性状进行了遗传分析。结果表明，穗角和每穗颖花数性状均受2对主基因+多基因共同控制。独立的2对主基因和多基因都存在加性 显性 上位性效应。穗角性状以主基因遗传为主；每穗颖花数性状以多基因遗传为主。     

Effects of Planting Time and Nitrogen Application on Dry Matter Yield of the Forage Rice Cultivar Tachiaoba in Southwestern Japan

Abstract

We examined the effects of planting time on the dry matter (DM) yield of the forage rice cultivar Tachiaoba in southwestern Japan. DM yield was much higher with early planting than with normal planting. Dry weight (DW) per tiller was much higher with early planting than with normal planting. Thus, early planting is effective to obtain high DM yield. DM yield was closely related to the DW increase from transplanting to the full-heading stage (DW increase before heading) and DW per tiller. These results suggest that early planting leads to an increase in DW at the full-heading stage through an increase in DW per tiller and gives a high DM yield at the yellow-ripe stage. We also examined the effects of nitrogen (N) application rate and method on DM yield at the yellow-ripe stage. DM yield was higher with application of 22.5 g N m-² than with 15.0 g N m-². Although DW per tiller was slightly lower with application of 22.5 g N m-² than with 15.0 g N m-², the number of tillers per square meter was much higher with application of 22.5 g N m-² than with 15.0 g N m-². DM yield was the highest with N application method 1 that was applied more N early, followed by methods 2 that was applied more N evenly over time and 3 that was applied more N later. The number of tillers per square meter was much higher with method 1 than with method 2 or 3. Thus, application of 22.5 g N m-² by method 1 is effective to obtain high DM yield. With both early and normal plantings, DM yield was closely related to the DW increase before heading and the number of tillers per square meter. These results suggest that application of 22.5 g N m-² by method 1 lead to an increase in DW at the full-heading stage through an increase in the number of tillers per square meter resulting in a high DM yield at the yellow-ripe stage.     

Effect of Leaf Phosphorus and Potassium Concentration on Chlorophyll Meter Reading in Rice

Abstract

Chlorophyll meter (SPAD) is a convenient tool to estimate leaf nitrogen (N) concentration of rice plants. There is no information on the effects of leaf phosphorus (P) and potassium (K) concentration on SPAD readings and on the relationship between SPAD values and leaf N concentration in the literature. In 1996 dry season, cv IR72 was grown at the International Rice Research Institute (IRRI) and the Philippine Rice Research Institute (PhilRice) under various N, P and K fertilizer combinations. SPAD measurements were made on the topmost fully expanded leaves at mid-tillering and panicle initiation. The leaves were then detached, dried and analyzed for N, P and K. The SPAD values were highly correlated with leaf N concentration (r = 0.93 to 0.96). Fertilizer-K application did not affect SPAD values, leaf N concentration, or the relationship between the two. Phosphorus deficiency reduced leaf N concentration at mid-tillering, but increased leaf N concentration at panicle initiation when the same amount of N was applied. The SPAD values were 1 to 2 units greater for zero-P plants than P-treated plants at a given leaf N concentration at mid-tillering. At panicle initiation, the relationship between SPAD values and leaf N concentration was not significantly affected by leaf P status. These results suggest that a different regression equation between SPAD values and leaf N concentration should be used to estimate leaf N concentration of P-deficient and P-sufficient rice leaves at vegetative stage using a SPAD.     

Effects of Nitrogen Application on the Development and Accumulation of Protein Bodies in Developing Rice Seed

Abstract

We examined the nature of protein bodies affected by nitrogen application in developing rice endosperm using scanning and transmission electron microscopes. Protein body type II, Pb-II, was observed at the first week after heading independent of nitrogen application, whereas protein body type I, Pb-I, was not observed in either the low nitrogen or non-fertilized group. However, in the high nitrogen group, Pb-I was also observed at 1 week after heading. Pb-I was formed by enlargement of endoplasmic reticulum cisternae, but Pb-II had a close relationship with the Golgi apparatus and was accumulated in the envelope-like vacuole. The smallest protein body, Pb-III, about 0.6-0.8 μm in diameter, appeared at 2 weeks after heading, and the amounts of this protein body increased substantially at 3 weeks after heading. This protein body also originated from endoplasmic reticulum cisternae. Pb-I was observed only in cytoplasm, but, Pb-II appeared in both the endoplasmic reticulum and envelope-like vacuole. The amount of protein bodies in the rice endosperm cell varied with the cultivar and amount of nitrogen applied. In cv. Koshihikari (Japonica), the application of much nitrogen increased the amount of protein bodies not only in the subaleurone, but even in the fifth layer from the aleurone layer. However, in cv. Belle patna (Indica), the application of much nitrogen increased the amount of protein bodies up to the sixth ayer of aleurone layer, and caused the accumulation of a few protein bodies even in the central part of endosperm. It was concluded that storage protein transported by Golgi vesicles and rough endoplasmic reticulum (RER) plays an important role in the accumulation of reserve substances in rice seed. Development of mitochondria and RER was enhanced by the application of nitrogen.     

江苏省粳稻品质育种的现状与对策

2000年以来,江苏省的粳稻品质改良取得了显著成绩,育成了48个品质达国标三级以上优质稻谷标准的优质粳稻新品种。但品质突出的优质品种不多,尤其是食味品质不能满足消费者的需求。同时,现有优质品种的抗性普遍较差,尤其缺乏对水稻条纹叶枯病和稻瘟病抗性强的品种。针对上述问题,提出江苏省粳稻品质改良的对策,应在重视外观品质改良的基础上,特别重视食味品质和抗性的改良,提高江苏粳稻品种的综合丰产性。     

Effects of Elevated Atmospheric Carbon Dioxide Concentration on Silica Deposition in Rice (Oryza sativa L.) Panicle

Abstract

The effects of elevated carbon dioxide concentration ([CO₂]) on silica deposition on husk epidermis of rice (Oryza sativa L. cv. Akitakomachi) during the flowering stage were investigated in this study. The study was motivated by the concept that the rice yield maybe affected by global warming as a result of elevated [CO₂] environment since sterility of rice is related to the panicle silica content that influences transpiration, and elevated [CO₂] could affect plant transpiration. Silica deposition analysis was focused on the flowering stage of the rice crop grown hydroponically under two [CO₂] conditions: 350 μmol mol-¹ (ambient) and 700 μmol mol-¹ (elevated). Silica deposition on the husk epidermis from three parts of the panicle at four flowering stages were examined using a scanning electron microscope (SEM) combined with an energy dispersive X-ray microanalyzer (EDX). The results demonstrated that elevated [CO₂] significantly suppressed silica deposition on the husk epidermis at the lower part of the panicle, and at the early flowering stage when 1/3 of the panicle emerged from the leaf sheath. In the transverse section analysis of the husk, silica deposition on the husk epidermis under elevated [CO₂] was less than that under ambient [CO₂] at the late flowering stage. The less silica deposition observed on the husks at the late flowering stage under elevated [CO₂] might be related to the suppressed transpiration from the panicle by elevated [CO₂] found in a previous study.     

Effects of Silicon on Tolerance to Water Deficit and Heat Stress in Rice Plants (Oryza sativa L.), Monitored by Electrolyte Leakage

Summary

To evaluate the positive efTects of silicon on the stress tolerance of rice plants, we measured the electrolyte leakage (El) from leaf tissue caused by desiccation with polyethylene glycol (PEG) and by high temperature to estimate the integrity of cell membranes. The El caused by 30% and 40% solutions of PEG decreased with the increase in the level of Si in leaves. In leaves of plants grown with 100 ppm Si02, the level of polysaccharides in cell walls, which is one of the factors related to tolerance to desiccation, was 1.6-fold higher than that in leaves of plants grown without Si. Ultrastructural observations of leaves revealed that polymerized Si accumulated in the walls of epidermal cells but not in those of the mesophyll cells, which are probably the main sites of El. These findings suggested that silicon in rice leaves is involved in the water relations of cells, such as mechanical properties and water permeability and plays a role in preventing El through the synthesis and functions of cell walls. The El caused by high temperature (42.5° C) was also lower in the leaves grown with Si than in the leaves grown without Si, suggesting the involvement of silicon in the thermal stability of lipids in cell membranes. These results suggested that silicon prevents the structural and functional deterioration of cell membranes when rice plants are exposed to environmental stress.     

Effect of Grain Position within a Panicle and Variety on As, Cd, Cr, Ni, Pb Concentrations in japonica Rice

Two japonica rice varieties, a compact panicle (CP) Xiushui 63 and a loose panicle (LP) Xiushui 11 were grown in a slightly contaminated paddy field, to determine the effect of grain positions within a panicle and variety on grain As, Cd, Cr, Ni and Pb concentrations. There was a significant difference in grain As, Cd, Cr, Ni and Pb concentrations among grain positions, and the extent of the difference was variety- and metal-specific; Xiushui 63 showed greater difference than Xiushui 11, and As, Cd, Cr and Pb being greater than Ni. The top grains (TG) of a panicle had higher As, Cd and Ni concentrations than the middle ones (MG), and the bottom ones (BG) contained the lowest. With regard to Cr and Pb, the case was opposite. Significantly positive correlations were found between grain weight and As, Cd, Ni concentrations, but there was a negative correlation between grain weight and Cr, and Pb concentrations. There was a remarkable variation in grain filling pattern among grains within a panicle, and between Xiushui 63 and Xiushui 11. In comparison with MG and TG, BG had the lowest grain filling rate and grain weight, leading to obvious difference in grain weight among grains within a panicle, and a greater difference for Xiushui 63 than for Xiushui 11. The regression analysis showed that grain As and Cd concentrations were positively correlated with the maximum grain filling rate (GRm),while negatively correlated with the required time for reaching the maximum grain filling rate (Tpol). Concerning Cr and Pb, the case was just reverse. It is suggested that As and Cd accumulation in grains might be accompanied by the carbohydrate accumulations, while Cr and Pb accumulation displayed a different pattern.     

Identification of Nutrients Limiting Rice Growth in Soils of Northeast Thailand under Water-Limiting and Non-Limiting Conditions

Summary

Glasshouse nutrient omission trials are useful in identifying nutrient limitations for plant growth in soils under the same environmental conditions. Soils of low fertility are commonly used for production of rainfed lowland rice (Oryza sativa L.), and the crop often encounters water stress. Nutrient requirements may be modified when standing water disappears from the field. Two experiments with rice seedlings were conducted in a glasshouse at Ubon Rice Research Center, Thailand, to identify the nutrients which limit rice growth in soils of Northeast Thailand, and to determine whether nutrient limitations are affected by water availability. In Experiment 1, rice was grown on two soils (Roi et and Ubon series) under well-watered and water-limiting conditions, and 15 nutrient treatments were imposed. In Experiment 2, six soils from Northeast Thailand were examined using the same 15 nutrient treatments. The nutrients which clearly limited the growth of rice plants in soils of Northeast Thailand were nitrogen (N) and phosphorus (P). In some cases, potassium (K) and sulfur (S) also limited growth, and in one soil zinc (Zn) and boron (B) also limited growth. A shortage of N was the most important limitation for plant growth in all soils except one in which P was more important. The low supply of P decreased plant height and leaf area development during early growth ; low N supply had a greater effect later during growth. The omission of P had a larger detrimental effect on growth when water supply was limited. In the Roi et soil, the omission of S had a large effect on leaf area and total dry matter production only under water stress conditions, but this was not found in the other soils examined. These results from glasshouse studies show that the nutrients limiting rice growth depend on soil type and water availability in soils of Northeast Thailand.     

水稻长穗大粒RIL群体主要品质性状的遗传分析

为探讨水稻长穗大粒RILs群体主要品质性状的遗传规律,以自育的一个水稻长穗大粒品系FJCD与籼型三系恢复系IR24配制杂交组合,单粒传法构建含有178个株系的RILs群体(F11)为材料,分别在福州和沙县2个不同生态条件下种植,采用植物数量性状的主基因+多基因混合遗传模型及其相应的统计方法,研究水稻主要品质性状的遗传特征。结果表明:除了精米率呈多基因遗传外,其他9个品质性状的最适遗传模型符合主基因+多基因混合遗传。精米率、米粒长、米粒宽、米粒长宽比、透明度、碱消值和直链淀粉含量在不同环境中表现相似的遗传模型;整精米率、垩白度和垩白粒率表现不同的遗传模型。由主基因遗传率为主的有整精米率、米粒长、垩白粒率、垩白度、透明度、碱消值和直链淀粉含量;由多基因遗传率为主的有米粒宽和米粒长宽比。环境因素对碱消值的影响最大。在不同生态条件下稻米主要品质性状间的相关性有82.22%的比率表现较为一致,不因环境的变化而改变其相关性。因此,在稻米品质选择与鉴定时需对整精米率、垩白度和垩白粒率在多个特定环境中进行,才能提高育种效率;对由主基因和多基因遗传率为主的性状需分别采用不同选择方法和育种策略。     

Geostatistical Analysis of Yield,Soil Properties and Crop Management Practices in Paddy Rice Fields

Abstract

We examined the possible benefit of rational site-specific crop management practices in 17 paddy fields located in an area of 2.0 ha for the prevalence of precision agriculture methods on a cooperatively managed large-scale farm in Sakurai, Nara Japan. Data on grain yield, soil physicochemical properties and farmer's crop management practices were collected in each paddy field. Unhulled rice yield was estimated at a resolution of 5m ? 5m in an area of 1.2 ha using a yield-monitoring combine. The spatial distribution of the variations for the collected data was characterized using geostatistical procedures. The kriged map of the unhulled rice yield drawn from the results of geostatistical analysis indicated the potential value of rational site-specific crop management using the yield-monitoring combine. The ratio of spatially structured variation to the total variation of brown rice yield, that is, the controllable proportion to total variation, was 75.4%. Each yield component i.e., the number of spikelets per square meter, filled-spikelet percentage and 1000-grain weight contributed 33.7%, 54.7% and 11.6%, respectively, to brown rice yield. These three yield components combined contributed to 96.5% of the brown rice yield variation. The agronomic factors (soil fertility factor, early growth factor, N dressing and uptake factor) contributed 79.7%, 52.1% and 41.8%, respectively, to the variation of these three yield components. Therefore these agronomic factors accounted for 58.1% of the total variation of the brown rice yield and 77.1% (i.e. 58.1% out of 75.4%) of the spatially structured variation of the brown rice yield. This controllable proportion may be a criterion for the prevalence of site-specific crop management in large-scale farm management in general, although only one case study was conducted.     

耐盐芦苇大片段BIBAC载体构建及水稻遗传转化

利用盐生植物的耐盐基因改良作物耐盐性是保障土壤盐渍化地区粮食生产和改良盐渍化土地的最经济最有效的途径。本研究以生长于西北盐盖上的一种耐盐野生芦苇为材料,制备了Mb级耐盐芦苇基因组DNA,酶切后经脉冲场凝胶电泳将其分离为不同大小的大片段DNA区段,并与酶切回收的BIBAC-S载体进行连接,成功构建了耐盐芦苇不同大小的大片段DNA-BIBAC载体,经根癌农杆菌EHA105介导,成功地转化了粳稻品种‘中花11’成熟胚愈伤组织,获得了转基因水稻植株。研究表明,不同大小的大片段DNA-BIBAC载体在转化同一受体材料时,其所获得的愈伤转化率、植株转化率、转基因植株的阳性率等存在差异,说明插入片段的大小与转化效率之间存在关系。本研究为创制耐盐水稻新种质、克隆盐生植物的耐盐基因提供了理论和技术参考。