同源四倍体水稻花粉的发育特征

利用激光扫描共聚焦显微技术观察了同源四倍体水稻紫粳 4x花粉的发育过程及其败育时期和方式。在成熟花粉中正常花粉只占45.5％,还有54.5％的花粉在发育过程中发生败育。在小孢子母细胞减数分裂过程中出现了一些异常现象,如染色体不能正常配对、形成异常二分体及二分体分裂不同步等现象。绝大部分花粉败育发生在单核小孢子期和二胞花粉晚期。在败育花粉中典败花粉粒占21.4％,圆败花粉粒占5.0％,染败花粉粒占28.1％。导致紫粳 4x花粉败育的原因可能是由于其染色体数目加倍,在减数分裂过程中有些染色体不能正常配对,从而进行异常分裂造成的。     

不同倍性水稻的花粉发育特征分析

以水稻品种红米2x和其对应的同源四倍体红米4x为试验材料,用激光扫描共聚焦显微镜观察了不同倍性水稻的花粉发育特征。结果表明,不同倍性水稻花粉粒形成过程基本相似,但与相应的二倍体水稻相比,同源四倍体水稻在减数分裂及后期发育过程中存在多种异常现象,如纤维素壁降解不完全、细胞不均等分裂及分裂不同步等现象;在成熟花粉中,二倍体水稻的正常花粉占89.92%,败育率为10.18%,四倍体水稻的正常花粉占69.96%,败育率高达30.04%;四倍体水稻的花粉直径显著大于二倍体水稻,且四倍体水稻的花粉粒萌发延迟。认为不同倍性水稻的花粉发育存在差异,染色体加倍对水稻花粉发育产生了不良影响。     

水稻胚囊形成过程与分期

 利用改进的GMA半薄连续切片技术对水稻品种IR36胚囊形成和发育进行了研究。结果表明：a)大孢子母细胞减数分裂Ⅰ形成的二分体和减数分裂Ⅱ形成的四分体的各个子细胞的大小都是不均等的；b)单核胚囊的3次有丝分裂的方向都较为固定；c)极核发育过程有明显的形态特征变化；d)胚囊形成各阶段淀粉粒出现与否有规律性。根据IR36胚囊形成的特点，初步将水稻胚囊形成过程分为8个时期，即孢原细胞形成期、大孢子母细胞形成期、大孢子母细胞减数分裂期、功能大孢子形成期、单核胚囊形成期、胚囊有丝分裂期、八核胚囊发育期和胚囊成熟期。     

水稻 (Oryza sativa L.)花粉及花药壁发育的超微结构研究

 运用透射电子显微镜技术,系统观察了水稻花粉及其花药壁层的发育过程,发现了一些新的现象：(1)小孢子母细胞减数分裂期间,伴随核内染色体变化的同时细胞质发生了“改组”现象,主要表现为核糖体分布密度的规律性变化,这标志着孢子体向配子体的转变。(2) 小孢子外壁的发育始于四分体晚期,最早表现在四分孢子质膜上沉积了少量的壁物质。随后沉积增多,至小孢子早期即形成初生外壁。此后外壁发育迅速,到小孢子晚期外壁已基本发育完成。(3)小孢子中期,小孢子细胞核的双层核膜局部分开,并逐渐扩张成一个“大泡”。核膜扩张在这一时期是一种普遍现象。(4)在花粉发育过程中,绒毡层细胞结构发生明显变化：小孢子母细胞形成之初,绒毡层细胞结构完整,内质网极少;随着减数分裂的进行,绒毡层胞质浓缩,细胞内出现“空腔”,内质网丰富;到了小孢子中期,仍有较多堆叠的内质网,此后逐渐消失。表明内质网在绒毡层的发育中起着重要的物质合成及运输作用。(5)花粉完全成熟时,花药中层细胞的壁以及绒毡层的外切向壁紧贴在一起,形成了一叠合的“壁”结构。     

转基因水稻B2花粉活力的温度模型

 以含bar基因的抗Basta转基因粳稻B2为材料,分别在5℃、10℃、15℃、20℃、25℃、30℃、35℃、40℃、45℃下进行处理,用2,3,5-氯化三苯基四氮唑（TTC）染色法测定了不同温度处理下转基因水稻B2花粉离体0、1、2、3、4、5、6、8、12、14 min后的活力。B2花粉离体后活力呈现“S”型下降,用Logistic模型可精确模拟两者的关系; 其次, B2花粉离体后活力随着温度先升后降,花粉活力的最适温度范围是20℃~30℃,25℃时活力最强,高温对花粉活力的胁迫作用更大。采用指数方程和Logistic方程分段函数,建立B2花粉活力的温度模型,可精确预测花粉存活时间和寿命,为进一步准确估算转基因水稻基因飘移距离提供依据。     

光周期对光敏核不育水稻小孢子发生和花粉发育的超微结构的影响

 以光敏核不育水稻农垦58S为材料，在杭州中国水稻研究所人工气候箱(Koitotron S-153W )群中进行光周期处理。自秧苗6叶期开始，先经10 h／d的短日照处理10 d 到幼穗开始分化，然后分别在13.14 h／d的光周期条件下发育。通过透射电镜观察探索光周期在决定花粉育性中的作用。结果发现，在13 h／d光周期条件，花粉发育正常，而在14h／d的光周期条件下，花粉在单核晚期败育，表现在核糖体呈聚合状态，内质网、质体、线粒体等细胞器逐渐解体，缺乏淀粉积累，吞噬泡增多，细胞质稀薄，最终变成不育。另一方面，绒毡层细胞保持完整状态，无解体迹象。     

水稻花粉萌发及花粉管生长动态

用显微镜观察水稻花粉粒的萌发、花粉管在雌蕊中的生长以及授粉后不同时间剪除柱头处理对颖花结实率的影响。 水稻花粉粒在授粉2 min后开始萌发;5～10 min后花粉管穿过柱头进入花柱生长;约经30 min花粉管顶端到达子房基部;40 min时有些花粉管顶端可接近胚囊,此时花粉管内胼胝质形成,但数量较少;50 min后花粉管内胼胝质塞大量形成,花粉粒萎缩干瘪。水稻花粉管在柱头、花柱和子房中的生长速率分别为1500、5000、5400 μm/h。水稻授粉后10～15 min剪除柱头的处理只有极少量颖花结实,授粉后20～50 min剪除柱头处理的颖花结实率随处理时间推迟而升高,授粉后50 min剪除柱头处理的结实率达60％以上,接近正常。     

花粉诱导效应对水稻杂交种子粒重的影响

以三系杂交梗稻的不育系、恢复系和常规粳稻品种为材料,研究了花粉诱导效应对水稻杂交种子粒重的影响.结果表明:对水稻杂交种子粒重具有重要影响的花粉诱导效应广泛存在,其影响程度取决于杂交父母本的具体配组.对于某一杂交父本而言,如果与不同的母本分别杂交,由花粉诱导效应引起的杂交种子粒重的变化往往具有一定的倾向性,这种倾向性具有强弱之分,因父本品种而异;对于某一杂交母本而言,如果与不同的父本分别杂交,由花粉诱导效应引起的杂交种子粒重的变化在不同组合之间大都具有显著或极显著的差异.     

栽培稻抗旱性研究的现状与策略

 水资源短缺正成为制约我国农业发展的重要因素。培育抗旱的栽培稻品种并实现水稻旱作，不但可在很大程度上节约水资源，而且有利于增产稳产，节约能源和减少环境污染。抗旱性包括逃旱性、避旱性、耐旱性和复原抗旱性。形态生理学的研究揭示出大量的与栽培稻抗旱性有关的形态特征和生理特性，如根系和叶片性状、生育期、渗透调节、脱落酸含量与栽培稻抗旱性密切相关，且已利用分子标记对上述性状进行了基因定位（QTL）研究。旱稻品种改良也已取得重大进展。在进行抗旱品种改良的基础上，通过引进相应的栽培技术，节水种植，实现水稻旱作，并达到稳产与增产的目的，是抗旱性研究的战略目标。在增产、稳产和优质的前提下，以培育耐旱性极强的水稻（或旱稻）为中心，建立有代表性的抗旱性研究基地, 进一步加强稻属抗旱基因资源的发掘和创新、抗旱生理学和遗传学的研究、利用现代生物技术实现不同物种间抗旱基因的转移、建立节水种植栽培技术新体系是目前抗旱性研究的主要内容。     

Salinity-Induced Ultrastructural Alterations in Leaf Cells of Rice (Oryza sativa L.)

Summary

High concentrations of NaCl significantly reduced the fresh and dry weights and lengths of roots and shoots. NaCl exhibited a more rapid effect in water culture than in soil culture. In both water and solid cultures, root growth was suppressed more severely than shoot growth. Electron microscopic studies revealed that NaCl caused swelling of thylakoids, accumulation of starch grains and lipid droplets, distortion of grana stacking, increase in the size and number of plastoglobuli and vesiculation of cellular membrane. Mitochondria became deficient in cristae, swelled and the matrix appeared pale in salt-treated plants as compared with control plants. Disappearance of nucleolus and nuclear chromatin and destruction of vascular tissues were occasionally observed in salt-treated plants.     

Rapid Swelling of Pollen Grains in Response to Floret Opening Unfolds Anther Locules in Rice (Oryza sativa L.)

Abstract

The changes in pollen grain diameter were examined in relation to the floret opening and anther dehiscence in rice (Oryza sativa L.). In the first experiment, the florets were artificially opened by excising the top of the glumes at various times before the expected natural flowering time. Pollen diameter increased rapidly in the artificially opened florets, but slowly in the controls in which the glumes were left intact. The time of anther dehiscence coincided well with the time when pollen grains reached their maximum diameter. In addition, the pollen grain diameter was significantly correlated with the percentage of dehisced anthers in the florets artificially opened at various times. These results indicate that floret opening induces the swelling of pollen grains and that the swelling is an important event for anther dehiscence. In the second experiment, anther segments with pollen left remaining intact and those with pollen removed were immersed in water. The septa in the anther segments without pollen failed to rupture in water, whereas 70% of the septa in the anther segments with pollen left remaining ruptured, indicating that the septa can be ruptured by the swelling pressure of pollen grains resulting in unfolding of anther locules. From these findings, we infer that the rapid swelling of pollen grains in response to floret opening is a driving force to rupture the septum and unfold the locules.     

The Green Fence of Chinese Hibiscus (Hibiscus rosa-sinensis L.) Prevents Pollen Dispersal of Transgenic Rice (Oryza sativa)

Abstract

Transgene escape mediated by pollen dispersal is one of the preeminent concerns about genetically modified crops, including rice. In this study, the rice pollen donor of non-glutinous Oryza sativa ssp. japonica cv. ‘Tainung 67’ [TNG 67] had a greater potential of pollen flow, which was shown by the greater quantity, germination rate, and viability of pollen, than the other rice pollen donor of transgenic AAN. The pollen-mediated gene flow was detected by the frequency of outcrossed seeds in a “checker-board pattern” and alternating row arrangement of rice pollen donor (TNG 67 or AAN) and pollen recipient (glutinous rice ‘TNG 73’) in the fields. We conducted field experiments to assess rice pollen dispersal with or without a “green” fence of Chinese hibiscus, Hibiscus rosa-sinensis L., of approximately 2 m in height and 0.6 m in thickness. Without a green fence, the outcrossing rate of TNG 73 seeds decreased with increasing distance from the pollen donor, from 1.68% at 1 m to 0.01% at 35 m, with no outcrossing beyond 40 m. The outcrossing rate varied with the direction of pollen donor, from 0.05% in the northeastern direction to 0.78% in the southern direction, which was caused by prevailing wind direction. With the green fence, no seeds of TNG 73 were outcrossed. Since a buffer zone of at least 40 m is needed to prevent outcrossing of rice by pollen dispersal in an open field, planting of Chinese hibiscus around the rice field as a green fence would be an effective measure for preventing transgene escape mediated by pollen flow.     

Grain Protein Content of Interspecific Progenies Derivedfrom the Cross of African Rice (Oryza glaberrima Steud.) and Asian Rice (Oryza sativa L.)

Abstract

The protein contents of the grain of 50 interspecific progenies developed from the cross between WAB56-104, an Oryza sativa variety, and CG 14, an Oryza glaberrima line, were investigated. In contrast to the higher protein content of O. glaberrima than O. sativa on the average, the protein content of CG 14 was always lower than that of WAB56-104. However, judging from the average of three seasons, 72% of the interspecific progenies had a higher protein content than the mid-parent and 50% of them had a higher protein content than WAB56-104. Although the actual values of protein content of the interspecific progenies were significantly different among the seasons, a highly significant correlation was always observed in protein content between any two of the three seasons. Protein content therefore was considered character of each interspecific progeny though it was also affected by environment. A significant correlation was not observed between paddy yield and protein content in any season; several interspecific progenies showed higher protein content and paddy yield than the mid-parents. A low paddy yield is likely to be associated with high protein content through physiological regulation without a genetic linkage between the two traits. However, the results suggest that the transgressive segregation of protein content observed in the interspecific progenies is attributed not to this physiological regulation but to a certain mechanism to concentrate protein in grains with a genetic background.     

利用同工酶标记水稻亲本遗传差异及其在杂交水稻育种中的利用

利用淀粉凝胶和聚丙烯酰胺凝胶电泳显示的同工酶差异，分析17个杂交水稻亲本、3个新株型株系和22个光壳稻、爪哇稻品种的遗传差异，研究光壳稻和爪哇稻及其与温带粳稻之间的关系，探索同工酶标记水稻亲本遗传差异在杂交稻育种中利用的可能性。在本研究中，8个同工酶18个多态性位点至少在2个基因型间存在差异。每个具有多态性的酶谱带分别以1和0记录存在与否，由同工酶数据计算的Nei’s遗传距离创建聚类树状图。聚类分析结果表明，籼稻和粳稻容易被分开，普通粳稻与光壳稻、爪哇稻混合聚在一起；光壳稻与爪哇稻之间的遗传距离要比它们与普通粳稻之间的遗传距离小。利用光壳稻、爪哇稻选育不同生态群方向的恢复系和不育系，已配组育成了强优势的杂交稻组合。     

不同生态环境下水稻穗部性状QTL鉴定

【目的】发掘与产量相关的穗粒性状QTL对进一步克隆和利用高产基因具有重要意义。【方法】以超级粳稻龙稻5号和典型高产籼稻中优早8号杂交衍生的重组自交系群体为试材,在4种环境下对穗部性状进行比较和QTL分析。【结果】共检测到63个穗部性状QTL,分布于除第9染色体外的11条染色体上。在4个环境下分别检测到27、27、18和35个QTL。其中,16个QTL能在2个环境下被检测到,12个在3个以上环境下稳定表达,分别占QTL总数的25.40%和19.05%;第1、3、4和5染色体的多效QTL簇能在不同环境下稳定表达,对穗部性状具有明显的调控作用。【结论】第3染色体STS3.3-STS3.6区间的qSNP3、第4染色体RM5688-RM1359区间的qSNP4.1是2个新的稳定表达的多效性QTL簇。此外,上位性效应是调控穗部性状的重要组分。     

Ammonia Emission from Leaves of Different Rice (Oryza sativa L.) Cultivars

Abstract

NH₃ emission from leaves of three rice (Oryza sativa L.) cultivars, Akenohoshi, Shirobeniya and Kasalath, was examined using a simple open chamber system.　In the three cultivars, NH₃ emission rate (AER) and NH₄⁺ content of leaves decreased with decreasing NH₄⁺ concentration in the root medium, but these values differed significantly with the cultivar. In the daytime, AER, NH₄⁺ content and glutamine synthetase (GS) activity in leaves changed similarly with maximum values around midday. Akenohoshi showed significantly lower AER and NH₄⁺ content but higher GS activity than Kasalath. The difference in AER among the rice cultivars may be related to the activity of GS involved in photorespiratory NH₃ recycling. Akenohoshi can be a breeding material useful for improving N recycling.     

Screening,Inheritance and Linkage Marker Analyses of Salt Tolerance in Mutated Scented Japonica Rice (Oryza sativa L.)

Abstract

We grew 1005 mutated scented japonica rice lines to the seventh steady genetic generation, and treated the seedlings with six true leaves with 300 mM NaCl for three days. Only the salt-tolerant line, SM61, survived. We obtained F₁, F₂ and F₃ populations from the cross between SM61 and a salt-susceptible indica variety, TCS17. After culture with 200 mM NaCl for five days, SM61 and F₁ (SM61×TCS17; TCS17×SM61) plants survived (R) while TCS17 plants did not (S). The R to S ratio in 513 F₂ plants showed a good fit to the Mendelian 3 : 1 segregation ratio by a Chi-square test indicating that the salt-tolerance of SM61 was governed by a single dominant gene. The mutated salt-tolerance gene explained close to 100% of the total phenotypic variation, and was tightly linked to RM223 (marker) located on chromosome 8, which was different from the results of previous studies investigating the relationship of QTLs with salt tolerance. This is the first report of mapping tightly linked markers of a single dominant mutated salt-tolerance gene.