Genetic Erosion from Modern Varieties into Traditional Upland Rice Cultivars (Oryza sativa L.) in Northern Thailand

The purpose of this study was to assess the extent of genetic erosion of traditional upland germplasm in northern Thailand as a result of gene-flow from distinct strains carrying different genotypes. Even modern variety specific markers have not been developed, there is a comparative population in Laos. Thus, both populations were compared with various characters to evaluate gene-flow from modern variety to landraces. Glutinous and glabrous strains are predominated in Laos. However, such strains were drastically decreased in north–east Thailand. Gene diversity is higher in Thailand, compared to Laos at seven isozyme loci. This was a result of the higher frequencies of Indica strains and heterozygotes in Thailand. Plastid type was also determined by using an INDEL marker. Nearly half of Indica strains carried the Japonica plastid. Heterozygotes also tended to carry Japonica cytoplasm. Such nuclear–cytoplasm substituted strains and heterozygotes were probably generated by natural hybridization. Japonica strains tended to be a maternal donor rather than Indica ones. Or Indica strains would easily release pollens, which grow outside of upland fields.     

介质pH与氮形态对不同水稻基因型根部通气组织形成的影响

在溶液培养条件下研究了不同介质pH和氮形态对5种不同的水稻(Oryza.sativa.L.)基因型(常规籼稻、杂交籼稻、常规粳稻、杂交粳稻和旱稻)根部通气组织形成的影响。结果表明,不同形态的氮与不同介质pH对水稻根通气组织形成的影响存在基因型差异。以NH4+-N为单一氮源时,低pH(pH.4.5)更有利于籼稻根的通气组织形成,而粳稻和旱稻根通气组织的形成受介质pH的影响不明显。以NO3--N为单一氮源时,近中性条件(pH.6.5)更有利于粳稻和旱稻根的通气组织形成,介质pH对籼稻根通气组织形成的影响未显示出明显差异。低pH条件下且以NH4+-N为单一N源时,稻根皮层处更易形成通气组织,可能是植物为了减轻低pH条件下铵毒害而产生的一种适应性机制。     

不同水分条件下水稻根解剖结构的比较分析

在旱作和淹水两种培养方式下,研究了5种基因型水稻(Oryza.sativa.L.)(常规粳稻、杂交粳稻、常规籼稻、杂交籼稻和旱稻)幼苗根系解剖结构的差异。结果表明,两种水分条件下,水稻根通气组织的形成和皮层厚壁细胞的形态均存在基因型差异。5种基因型间,淹水条件下杂交粳稻根形成通气组织的时间最晚,根皮层厚壁细胞形态上的差异在常规粳稻和常规籼稻之间表现得更为明显;旱作条件下旱稻的根通气组织形成较其他基因型晚,常规粳稻根皮层厚壁细胞排列疏松,细胞壁加厚程度小。与淹水条件相比,旱作条件下杂交稻根通气组织形成较迟,常规粳稻根皮层厚壁细胞排列较疏松。     

Genotypic variation in grain cadmium concentration of lowland rice

Cadmium (Cd) contamination of paddy rice soils is commonly observed in the Yangtse River Delta, China. Large Cd uptake by rice plants and its translocation into the grains can entail human‐health risks. Genotypic variations in Cd uptake and a differential Cd partitioning into grains will be the basis for developing a rice screening or breeding tool for low grain Cd. A field experiment, conducted at the experimental farm of Jiaxing, Zhejiang province from 2002 to 2004, compared 38 rice genotypes of different types (indica vs. japonica) collected from the Yangtse River Delta. The results showed large differences in Cd concentrations in straw, brown rice, and grain chaff among the rice genotypes grown on Cd‐contaminated soil. Concentrations in brown rice ranged from 0.06 to 0.99 mg Cd kg^–1. The total Cd uptake in brown rice varied between 0.96 and 28.58 μg plant ^{– 1}. In general, indica‐type cultivars accumulated significantly more Cd than the japonica‐type cultivars. The Cd concentration in straw was highly correlated with that in brown rice. While significant differences in the Cd‐partitioning ratio (% share of total Cd uptake found in brown rice) among rice genotypes were observed, these were not correlated with Cd concentration of brown rice. This indicates that the Cd accumulation in rice grains appears to be governed mainly by the Cd uptake by the plant and probably not by differential Cd partitioning. The large genotypic variation suggests the possibility to lower the Cd content of rice by genotype selection. The development of such breeding tools should focus on low Cd uptake rather than Cd partitioning between straw and grain.     

Population structure of the primary gene pool of Oryza sativa in Thailand

The gene pool of cultivated Asian rice consists of wild rice (Oryza rufipogon Griff.), cultivated rice (O. sativa L.) and a weedy form (O. sativa f. spontanea). All three components are widespread in Thailand, frequently co-occurring within fields and providing the opportunity for gene flow and introgression. The purpose to this study is to understand the on-going evolutionary processes that affect the gene pool of rice by analysis of microsatellite variation. Results indicate that O. rufipogon, the wild ancestor of rice, has high levels of genetic variation both within and among populations. Moreover, the variation is structured predominantly by annual and perennial life history. High levels of variation are detected among cultivars indicating Thai cultivated rice has a broad genetic base with only a 20 % reduction in diversity from its wild ancestor. The weedy rice populations reveal varying levels of genetic variation, from nearly as high as wild rice to near zero. Weedy rice is genetically structured into 2 groups. Some populations of invasive weedy rice are the result of hybridization and gene flow between local wild rice and local cultivated rice in the regions of co-occurrence. Other populations of weedy rice are genetically nearly identical to the local cultivated rice. The diversity analysis indicates that the rice gene pool in Thailand is a dynamic genetic system. Gene flow is ongoing among its three main components, first between cultivated and wild rice resulting in weedy rice. Weedy rice in turn crosses with both cultivated varieties and wild rice.     

粤北普通野生稻籼粳分化的SSR分析

本文利用28对籼粳特异性SSR引物对174个粤北普通野生稻个体进行分析。28对引物均有多态性,平均每对引物扩增出的等位变异数和基因型数分别为10.6和28。粤北普通野生稻群体有较高的遗传多样性(0.7681),除了能扩增出典型的籼、粳特异基因,还能扩增出野生稻特有的基因。遗传一致度聚类分析表明粤北普通野生稻存在初步籼粳分化;2份(1.15%)材料偏籼,172份(98.85%)材料偏粳,群体以偏粳为主。基因组水平上整个粤北群体没有发现原始类型。     

籼、粳超级稻氮素吸收利用与转运差异研究

【目的】目前我国选育和认定的超级稻品种很多,但如何发挥其高产潜力至关重要。氮素是影响水稻生长发育、 产量和品质形成的最活跃因素之一,因此,深入分析籼、 粳超级稻氮素吸收、 利用与转运特征及其与产量形成的关系,从氮素营养层面上阐明超级粳稻高产形成机理,以期为超级稻品种的合理利用以及增产潜力的挖掘提供参考。【方法】2011~2012年在江苏苏中地区,以主体且具有代表性的5个超级杂交籼稻组合和5个常规粳型超级稻品种为试验材料,对稻-麦两熟制条件下籼、 粳超级稻主要生育期植株含氮率和氮素积累量、 氮素阶段吸收速率和阶段吸收量、 氮素利用效率,以及抽穗至成熟期叶、 茎、 鞘氮素转运量、 表观转运率和转运贡献率等进行了系统的比较研究。【结果】1）粳稻平均实收产量、 氮素吸收总量和百公斤籽粒吸氮量分别达10.89 t/hm2、 224.50 kg/hm2和2.79 kg,分别较籼稻高13.21%、 32.74%和17.45%,差异极显著。2）移栽有效分蘖临界叶龄期、 拔节抽穗期和抽穗成熟期, 粳稻氮素积累量显著或极显著高于籼稻,而有效分蘖临界叶龄期拔节期粳稻极显著低于籼稻。氮素阶段吸收速率表现的趋势与氮素阶段吸收量一致。3）抽穗期和成熟期粳稻植株各器官以及整个生育期整株的含氮率均显著或极显著高于籼稻。4）粳稻氮素吸收利用率和农学利用率略高于籼稻,但氮素生理利用率、 籽粒生产效率、 干物质生产效率和氮肥偏生产力,除氮素生理利用率外,均显著或极显著低于籼稻。5）成熟期,粳稻叶、 茎、 鞘含氮量所占比例均极显著地高于籼稻,但穗中含氮量所占比例极显著低于籼稻,因此,籼稻氮素收获指数极显著高于粳稻。6）抽穗成熟期,粳稻叶、 茎、 鞘氮素转运量、 表观转运率和转运贡献率均小于籼稻,除鞘的氮素转运贡献率外其他指标均达显著或极显著水平。7）籼稻籽粒氮主要依靠抽穗前源器官中贮积的氮素的输出与转运,粳稻主要依靠生育中后期(拔节成熟期)氮素的高速吸收。【结论】在稳定生育前期(移栽拔节期)氮素吸收的基础上,大幅提高生育中期和后期(拔节成熟期)氮素吸收速率和氮素积累量,是稳定形成较高的氮素吸收总量及粳稻高产形成的关键。     

灌浆期不同光强对水稻不同粒位籽粒品质的影响

为探讨灌浆期光照强度对水稻籽粒品质的影响及在不同品种类型和粒间差异,揭示弱光下水稻籽粒充实不良和米质变劣的生理机制,本文以代表性的超级稻品种"扬两优6号"和"武运粳23"为材料,以穗中部不同粒位籽粒为研究对象,以自然光强为对照,设置3种弱光处理(光强分别为对照的71%、55%和40%),研究了灌浆期不同光照强度对稻米品质的影响。结果表明:1)灌浆期光照强度对稻米品质影响较大,光强减弱稻米品质变劣,光照对米质形成的影响因光照强度大小、品种类型和籽粒着生位置不同而存在差异,同枝梗上迟开花籽粒稳定性较差,早开花籽粒稳定性较好。2)随光照强度降低,整精米率和直链淀粉含量降低,垩白度增加,不同光强下一次枝梗籽粒变化幅度大于二次枝梗籽粒;光强越弱,崩解值越低,消减值和粗蛋白含量越高,稻米蒸煮食味品质变差。3)生产上应因品种类型合理安排播期,通过栽培措施改善稻株受光条件,减轻光照不足对稻米品质形成的影响。     

云南地方稻种资源核心种质的微卫星分析

摘要：以来自云南地方稻(Oryza sativa L.)种资源核心种质中的113份材料为研究对象，运用36对微卫星引物，研究了籼(indica )粳( japonica )两个亚种间和云南5个稻作生态区间的遗传多样性分布趋势，并筛选了籼粳亚种、水陆生态型和不同生态区的特异指纹标记。结果表明，粳稻的遗传多样性大于籼稻，遗传分化水平较低；而5个生态区中滇西南水陆稻区遗传多样性最大，遗传分化水平较低；滇东北高原粳稻区的遗传多样性最小。这种遗传多样性的分布趋势与前人在形态和同工酶水平上对云南稻种资源多样性的考察，以及云南地方稻种资源核心种质在形态和同工酶水平上的遗传多样性分布趋势基本一致。另外，在所出现的416个指纹标记中，分别发现籼粳特异指纹标记6个，水陆特异指纹标记15个，不同生态区特异指纹标记3个。初步认为，云南地方稻种资源核心种质代表了云南省地方稻种资源的遗传多样性；从DNA水平上看，云南地方稻种资源的遗传多样性中心在云南省的西南部，粳稻的分化水平低于籼稻。微卫星标记是种质资源遗传多样性检测、分类和生态型确认以及核心种质研究中有用的工具。     

水稻品种和砷污染对土壤溶解性有机碳氮的影响

选取有机质含量和pH不同的2种水稻土(黄泥田和红泥田),通过盆栽实验研究砷(As)污染条件下,种植9个水稻品种对土壤溶解性有机碳(DOC)和溶解性有机氮(DON)含量的影响,分析水稻品种、As污染和土壤类型的相对影响与交互作用.结果表明,水稻品种显著影响了土壤DOC和DON的变化,在水稻收获后,DOC平均含量的大小顺序为杂交稻(41.09±0.92 mg kg-1)＞籼稻(38.10±1.53 mg kg-1)＞粳稻(37.74± 1.37 mg kg-1);DON平均含量的大小顺序为粳稻(2.94± 0.40 mg kg-1)＞杂交稻(2.61±0.42 mg kg-1)＞籼稻(1.45± 0.17 mg kg-1).As污染降低了土壤DOC和DON的含量,但不同品种水稻的响应不同.与对照相比,As污染条件下,黄泥田和红泥田中DOC平均含量分别下降了14.4％和11.1％,DON平均含量分别下降了65.0％和44.7％;DOC在种植杂交稻后降幅最小,而DON在种植籼稻后降幅最小.在两种水稻土中,黄泥田的DOC和DON平均含量高于红泥田,在没有As污染条件下,分别高22.4％和45.8％,这与黄泥田有机质含量和pH高有关.水稻品种、As污染和土壤类型对DOC和DON变化的影响不同,3个因子对DOC变化的相对贡献率分别为7.7％、15.5％和27.6％,对DON变化的相对贡献率分别为14.7％、24.2％和2.0％.     

甬优系列籼粳杂交稻氮素积累与转运特征

【目的】 比较分析甬优系列籼粳杂交稻氮素吸收利用与转运特征,从氮素层面阐明甬优系列籼粳杂交稻高产形成特征。 【方法】 2013～2014 年,选用 7 个甬优系列籼粳杂交稻组合为试验材料,以 2 个常规粳稻品种和 2 个杂交籼稻品种为对照,比较研究甬优系列籼粳杂交稻主要生育时期植株含氮率、氮素积累量,不同生育阶段氮素积累量与吸收速率,抽穗期和成熟期各器官的含氮率和氮积累量所占比例,抽穗至成熟期各器官间的氮素转运,以及氮素利用效率等特征。 【结果】 甬优系列籼粳杂交稻抽穗期植株含氮率和氮积累量分别为 1.47%、202.67 kg/hm2,成熟期植株含氮率与氮积累量分别为 1.31%、257.23 kg/hm2,极显著大于对照类型。甬优系列籼粳杂交稻氮素最大阶段性积累量为 107.63 kg/hm2,所占比例为 41.84%,最大吸收速率为 2.73 kg/(hm2·d),且均出现在拔节至抽穗阶段,杂交籼稻出现在移栽至拔节阶段。甬优系列籼粳杂交稻抽穗期茎鞘和叶的含氮率分别为 1.19% 和 2.34%,成熟期分别为 0.75% 和 1.58%,高于对照类型。甬优系列籼粳杂交稻抽穗期茎鞘和叶氮积累量所占比例分别为 43.92% 和 43.87%,成熟期分别为 16.44% 和 17.44%,极显著大于杂交籼稻。甬优系列籼粳杂交稻氮素转运量大,表观转运率和转运贡献率不高,抽穗后的氮素净积累量贡献率为 32.06%,显著大于对照类型。甬优系列籼粳杂交稻百公斤籽粒吸氮量为 2.29 kg,极显著大于杂交籼稻;氮肥偏生产力为 37.54 kg/kg,极显著大于常规粳稻;氮素籽粒生产效率、氮素干物质生产效率和氮素收获指数偏低。 【结论】 甬优系列籼粳杂交稻总吸氮量大,在拔节期足量氮素积累的基础上,提高了拔节至抽穗期与抽穗至成熟期两个阶段的氮积累比例;抽穗至成熟期茎鞘和叶的氮素转运量大,但表观转运率与表观转运贡献率低,抽穗后氮素积累优势明显,氮素净积累量贡献率高,满足了灌浆期籽粒对氮素的需求。      

Comparison of the physicochemical properties and ultrastructure of japonica and indica rice grains

The physicochemical properties and ultrastructures of japonica vs indica rice varieties and waxy vs nonwaxy rice varieties were compared. The viscogram values of the indica varieties were significantly higher than those of the japonica varieties. The gelatinization temperatures, breakdown, and setback were significantly lower for waxy than for nonwaxy rice varieties. Japonica rice exhibited lower hardness but higher adhesiveness than indica rice. The air space between individual starch granules was larger for waxy than for nonwaxy rice. The starch granules were compact in japonica rice, while the compound starch granules of indica rice were much smaller than those of japonica rice and were scattered widely in the endosperm. The protein bodies in japonica rice were concentrated near the cell wall, whereas those in indica rice were scattered around amyloplasts. These results suggest that the ultrastructure of rice affects the texture of the cooked product.     

The Weedy Rice Complex in Costa Rica. I. Morphological Study of Relationships Between Commercial Rice Varieties,Wild <Emphasis Type="Italic">Oryza</Emphasis> Relatives and Weedy Types

Weedy rice is a complex of Oryza morphotypes widely distributed in commercial rice fields, which interfere with rice cultivation, seed production, industrial processing and commercialization of this crop in several countries. The objective of this study was to characterize the weedy rice complex of Costa Rica by comparing it with the cultivated and wild rice species found in the country. A collection of weedy rice accessions, representative of the morphotypes found in the country, was established and characterized. Their morphometric relationships were established by comparing 27 morphological traits with commercial rice cultivars, landraces and wild Oryza species and by performing a multivariate analysis. Twenty-one weedy rice morphotypes were identified among 735 weedy accessions by using a three-digit code based on seed characters. Three principal components (PCs) explained 66.25% of the variation observed. The first PC accounted for 36.21% of the variation and separated CCDD genome type Oryza latifolia and O. grandiglumis from AA genome species O. sativa, O. glumaepatula, O. rufipogon and O. glaberrima. The second (18.9%) and third (11.14%) PCs separated the weedy morphotype groups from the AA genome species O.sativa, O. glaberrima and O. rufipogon. The weedy morphotypes were scattered between the indica commercial rice varieties, the cluster landraces–glaberrima and O. rufipogon. Additionally, a group of morphotypes showed intermediate characteristics between O. sativa and O. rufipogon, suggesting that hybridization could have taken place in the past between these species. None of the morphotypes collected in Costa Rica clustered with the allotetraploids CCDD species or O. glumaepatula.     

不同类型水稻种质氮素营养效率的变异分析

采用田间试验,在常规氮素管理下,以氮素吸收效率(NAE)、利用效率(NUE)和收获指数(NHI)为衡量指标,分析了国内外607份不同类型水稻种质氮素营养效率的变异状况。结果表明,水稻NAE、NUE和NHI存在显著的基因型差异,以NHI为最大和NAE为最小。不同类型水稻间的NAE、NUE和NHI未达显著差异,但籼型杂交稻NAE、NUE和NHI的变异小于常规籼稻和常规粳稻。相关分析表明,水稻NAE与NUE、NHI呈极显著负相关,NUE与NHI间无显著相关;水稻NUE和NHI与单株产量存在极显著的正相关,NAE与单株产量无显著相关。频数分析可知,常规籼稻NAE、NUE及NHI和籼型杂交稻NUE的种质频数分布呈典型正态曲线,低、高效种质较少,中效种质众多;常规粳稻NAE、NUE和NHI种质的频数分布呈近似正态分布,略偏向低效;籼型杂交稻NAE的种质频数分布离散程度较高和高效种质较多,NHI的种质频数分布呈近似正态分布和略偏低效。籼型杂交稻的NAE、NUE和NHI差异小而分布较集中,常规粳稻最分散,常规籼稻居中。不同类型水稻的氮素营养效率的极差很大,可分为若干组,各组间差异显著。     

Crop–weed hybrids are more frequent for the grain amaranth ‘Plainsman’ than for ‘D136-1’

White-seeded cultivated amaranth [Amaranthus caudatus L., A. cruentus L., and A. hypochondriacus L.] grain is less valuable if contaminated with brown off-type seeds from the hybrid weedy progeny of spontaneous crop–weed crossing. Crop–weed crossing frequency was estimated by using two grain amaranth cultivars. Both cultivars were planted at the same nine locations in the Midwest United States and exposed to pollen from local weedy Amaranthus species. Harvested seeds were grown in a greenhouse, and the frequency of crop–weed hybrids was determined by observing dominant weed traits in the progeny. The cultivar ‘Plainsman’ was approximately tenfold more likely to hybridize with weedy amaranths than was ‘D136-1’. These are the first amaranth cultivars to be evaluated in this way. The reduced hybridization potential of ‘D136-1’ or similar material can be exploited to reduce the occurrence of off-type seed contamination in grain amaranths.     

Practical phytoextraction in cadmium-polluted paddy fields using a high cadmium accumulating rice plant cultured by early drainage of irrigation water

Some indica rice varieties are potential phytoextractors for paddy fields polluted with Cd because of their high biomass and because they can accumulate Cd to moderate levels in their shoots. To establish a practical phytoextraction system, phytoextraction using two indica rice cultivars (MORETSU and IR-8) was carried out in a paddy field polluted with moderate Cd levels (2.91 and 2.52 mg kg⁻¹, respectively). The Cd concentration and Cd uptake of MORETSU increased when irrigation water was drained at the maximum tillering stage, and the paddy soil was under oxidative conditions until harvesting. The Cd uptake of MORETSU and IR-8 increased and reached 516 and 657 g ha⁻¹, respectively, at the beginning of October. After phytoextraction using these high Cd accumulating rice varieties for 2 years, the Cd concentration in the paddy field decreased by 18% compared with the initial Cd concentration. The Cd concentration in the rice grains of a japonica ordinary rice variety (HINOHIKARI) subsequently grown on the field after the phytoextraction was lower than the concentration in rice grown on a non-phytoextracted field. These results suggest that phytoextraction using high Cd accumulating rice varieties with early drainage of irrigation water is a practical remediation system for moderate Cd polluted paddy fields in southwest Japan.     

气吹集排式水稻旱直播机关键部件设计与试验

针对中国水稻直播品种不一、高速作业和大播量的要求,该文设计了一种气吹集排式水稻旱地精量直播机,直播机主要由均匀分种装置、定量排种装置、气力输送装置、同步传动装置、大尺寸集成种箱、开沟覆土镇压装置和支撑悬挂装置组成。从直播机的稻种适应性、作业速度、播量调节等方面研究了气吹集排式分种器的分种机理和分种均匀性。根据不同品种水稻种子的物理特性和气流输送原理,分析了不同种子在持续气流作用下,种子在分种器中的运动轨迹。按照大播量可调要求,设计了播量无级可调槽轮式排种器,槽轮槽形为圆弧状,通过双地轮驱动排种器保证播量同步。设计变速传动装置增加定量排种装置高速作业的适应性,气力输送装置使定量排种装置排出的种子在高速作业下连续排入播种沟。分种器的均匀稳定分种提高了直播机播种的均匀性和稳定性,通过减少排种器数量和使用气力输送种子,降低了伤种率。对比不同籼、粳稻品种在直播过程的运动规律和田间播种效果,得到了适应不同稻种的分种器结构及相关参数。试制了气吹集排式直播机并进行田间试验。田间试验结果表明,气吹集排式直播机的播量在75～375 kg/hm2可调,最高作业速度为14 km/h,10行幅宽2 m和20行幅宽4 m的每行播种量变异系数分别为4.89%和5.06%,田间播种的稻种破损率为0.46%。2017年,在宁夏播种富源4号品种的产量为10 372.5 kg/hm2,在广东播种粤农丝苗品种的产量为7 074kg/hm2,生产试验结果表明,所研制的气吹集排式水稻旱直播机达到了设计目标,满足作业需求。     

Nitrogen acquisition and its relation to growth and yield in recent high-yielding cultivars of rice (Oryza sativa L.) in Japan

During the last two decades, high-yielding cultivars for multipurpose use of rice have been bred and released in Japan. Some of them have repeatedly recorded high yields of over 9?t?ha^?1 of brown rice (about 11.25?t?ha^?1 of rough rice). Here, characteristic features of nitrogen (N) acquisition and its relation to formation of yield components, dry matter production and grain yield at yield levels over 9?t?ha^?1 of brown rice in recent high-yielding cultivars, a large grain type of japonica variety, “Akita 63,” extra-panicle weight types of indica variety, “Takanari” and “Saikai 198,” and a panicle weight type of japonica variety, “Fukuhibiki,” are described as compared with those in the standard japonica cultivars, “Toyonishiki” and “Nipponbare.” The grain yield of the recent high-yielding cultivars was 9.4 to 11.6?t?ha^?1 of brown rice; that is 1.2?1.7 times greater than those of the standard cultivars. Sink capacity (1000-grain weight?×?spikelet number per unit land area) was 47?62% greater in the recent high-yielding cultivars, largely due to their 1.3?1.5 times greater N-use efficiency for sink formation (sink capacity per unit amount of total plant N in the aboveground part at maturity), although major component(s) responsible for their greater sink capacity differ among the cultivars. The ratio of grain yield to total dry matter was 1.1?1.4 times greater in the recent high-yielding cultivars than in the standard cultivars, indicating that the former efficiently translocate dry matter into spikelets during the grain-filling period. N-use efficiency for dry matter production (total dry matter per unit amount of total plant N) was comparable between “Akita 63,” “Fukuhibiki” and “Toyonishiki,” and slightly greater in “Takanari” and “Saikai 198” than in “Nipponbare.”

These results indicate that greater N-use efficiency for sink formation and efficient translocation of dry matter into spikelets contribute greatly to the high-yielding potential of the recent high-yielding cultivars.     

Nitrogen Use Efficiency of Rice Under Cadmium Contamination:Influence of Rice Cultivar Versus Soil Type

There is a need for rice cultivars with high yields and nitrogen (N) use efficiency (NUE), but with low cadmium (Cd) accumulation in Cd-contaminated paddy soils. To determine the relative effects of rice genotype, soil type, and Cd addition on rice grain yield and NUE, a pot experiment consisting of nine rice cultivars was conducted in two types of paddy soils, red soil (RS) and yellow soil (YS), without or with Cd spiked at 0.6 mg kg^-1. The N supply was from both soil organic N pools and N fertilizers; thus, NUE was defined as the grain yield per unit of total crop-available N in the soil. Cd addition decreased grain yield and NUE in most rice cultivars, which was mainly related to reduced N uptake efficiency (NpUE, defined as the percentage of N taken up by the crop per unit of soil available N). However, Cd addition enhanced N assimilation efficiency (NtUE, defined as the grain yield per unit of N taken up by the crop) by 21.9% on average in all rice cultivars. The NpUE was mainly affected by soil type, whereas NtUE was affected by rice cultivar. Hybrid cultivars had higher NUEs than the japonica and indica cultivars because of their greater biomass and higher tolerance to Cd contamination. Reduction of NUE after Cd addition was stronger in RS than in YS, which was related to the lower absorption capacity for Cd in RS. Canonical correspondence analysis-based variation partitioning showed that cultivar type had the largest effect (34.4%) on NUE, followed by Cd addition (15.2%) and soil type (10.0%).     

不同基因型机插稻植株氮素积累运转特性

【目的】明确机械化育插秧条件下不同基因型水稻氮素吸收利用的特点,分析提高其氮素吸收利用的途径。【方法】以3个中籼中熟杂交稻、3个中籼迟熟杂交稻、4个粳稻共计10个品种为材料,采用随机区组大田试验设计,测定不同生育时期各器官干物重和氮素含量、产量等,研究了不同基因型机插稻植株氮素积累、分配和运转特性的差异及其原因。【结果】1)育插秧机械化条件下水稻植株氮素积累符合Logistic曲线增长规律。2)整个生育期机插稻植株含氮量呈下降趋势,粳稻植株的含氮量在生长中期(拔节期—抽穗期)高于杂交籼稻,而后逐渐降低,到成熟期极显著低于杂交籼稻,中籼中熟杂交稻因降低缓慢到成熟期植株含氮量最高。3)粳稻植株的终极氮素积累量最低,中籼中熟杂交稻和中籼迟熟杂交稻终极氮素积累量平均比粳稻高23.0%和33.1%。4)中籼中熟杂交稻抽穗期—成熟期氮素积累量最大,在氮素积累上具有后发优势,且穗部分配率、叶片与茎鞘氮素表观转运率、氮素籽粒生产效率和氮素转运效率均较高,说明育插秧机械化条件下,中籼中熟杂交稻品种的氮素在转运和利用上具有高效性。其中,F优498的终极氮素积累量高,且具有前期积累快,后期运转分配合理等优势。5)中籼迟熟杂交稻氮素积累出现最大增长速率较晚,平稳持续增长时间较长,终极积累量最大,但氮素积累对产量的贡献没有优势。6)粳稻中杂交粳稻69优8号相比其他粳稻品种,氮素积累量大且产量高,也具有氮素转运和利用的高效性。【结论】机插稻植株氮素积累转运特性受不同基因型的显著影响。本研究采用植株含氮量、终极氮素积累量、百千克籽粒吸氮量等反映机插稻氮素吸收转运特性的指标进行比较发现,在育插秧机械化条件下,中籼中熟杂交稻相比中籼迟熟杂交稻和粳稻氮素具有积累转运和利用高效性,其中F优498在氮素积累、分配并促进产量形成方面具有遗传上的优势。中籼迟熟杂交稻虽具有氮素积累量潜力,但氮素积累对水稻产量的贡献相对较低。机插粳稻氮素积累较低,但相比其他粳稻品种机插杂交粳稻69优8号具有氮素积累量大且产量高的潜力,较适合机插。