龙须草花粉活性及结实率与其无融合生殖的关系

以两种生态型无融合生殖龙须草为材料,经去雄套袋、去掉柱头及相互杂交等处理,比较几种方式下的结实率。结果表明：去雄套袋、截去柱头以破坏授粉和杂交授粉等处理与去雄不套袋作对照之间结实率的差异不显著。两种生态型龙须草的成熟花粉粒都具有活力,在蔗糖溶液中的离体萌发率分别为28％和34％;花粉在柱头上的附着和生长的荧光观察表明：花粉附着率较低,花粉在柱头上可以萌发,但不能进入柱头和花柱。证明龙须草花粉对其结实率没有显著影响;龙须草具有很高的无融合生殖度,是优良的无融合生殖基因供体。     

水稻籼、粳花粉源基因飘流的竞争性

基因飘流是水稻(Oryza sativa L.)转基因安全性研究中的重要内容,研究花粉竞争对基因飘流的影响对于建立并完善转基因飘流模型具有重要意义。本实验分别以籼、粳型转基因水稻和籼、粳常规水稻为花粉供体,不育系为花粉受体,研究籼、粳型双供体在基因飘流中的竞争性。结果表明,同种亚种双供体的基因飘流率与花粉源数量成正相关关系,且基因飘流率与供体花粉数量关系符合S曲线。基因飘流是花粉数量竞争和遗传竞争的综合结果。     

风信子品种间杂交与幼胚离体培养研究

选用5个风信子品种进行花粉生命力测定,对完全双列杂交获得的杂种种子剥胚进行离体培养.试验表明:(1)风信子不同品种花粉萌发率差别较大,其中Fondante的花粉萌发率最高为74.45%,Amsterdam的最低为12.68%,其他3个品种的花粉萌发率介于二者之间.(2)品种间自交杂交亲和力存在一定差异,结实率大于30%的组合从高到低依次为Fondante×Atlantic(61.2%)、Fondante×Fondante(54.0%)、Carnegie×Carnegie(42.6%)、JanBos×JanBos(36.0%)、Carnegie×Atlantic(32.7%)、Atlantic×Fondante(30.0%),组合Atlantic×Amster-dam、Carnegie×JanBos、Amsterdam×Fondante、Amsterdam×JanBos、JanBos×Amsterdam未得到果实,其余组合结实率介于0～30%之间.(3)适宜风信子杂交幼胚离体培养的初代培养基为MS+100 mg/L谷氨酰胺,其次为MS+0.2 mg/LIBA+0.02 mg/L6-BA+100 mg/L谷氨酰胺...     

花粉离体培养基的优化和苯达松除草剂对敏感型水稻恢复系''''Mc526''''花粉活力的影响

建立了适合水稻花粉离体萌发的液体培养基配方,并用花粉萌发和碘-碘化钾（I2-KI）染色测定法检测了喷施苯达松后含敏感致死基因的水稻恢复系‘Mc526’的花粉生活力。结果表明,苯达松处理前期（施后14d）,‘Mc526’花粉活力与未作处理的接近;处理后期（施后5-8d）略低于未作处理的,但差异不显著。苯达松对母本结实率影响不显著。     

甘蓝型油菜CMS微粉活力研究及其对杂交制种纯度的影响

通过对微粉和正常花粉在不同和同一雌蕊上的结实力比较和结实竞争研究,表明微粉虽能够授粉结实,但活力低、萌发慢、持续时间短、受精结实能力差,与正常花粉的竞争力弱,授微粉后间隔３－７２ｈ,再授恢复系花粉,其结实表现仍可达到或超过单独授恢复系花粉的结实率,最高的还超过了只授恢复系花粉结实率的９．５７％;授微粉后间隔０－４８ｈ再授恢复系花粉仍可获得７０．３５％－９１．００％的异交率,说明微粉对油菜杂交制种过     

风速对转基因棉花基因漂移的影响

在转基因作物全球商业化推广的20年间,公众对基因漂移生态安全问题的关注持续升温。本试验以转基因双价棉SGK321(Cry1Ac/Cp TI)为花粉供体,常规棉"石远321"和"中棉35"为花粉授体,借助PCR和蛋白检测技术,研究温室中3种风速(0.54、0.92和1.27 m·s-1)条件下的Cry1Ac基因漂移频率。结果表明:"石远321"作为花粉受体时,基因漂移频率受风速影响,低风速下最高,高风速下最低;"中棉35"作为花粉授体时,基因漂移频率整体较低,不受风速影响;基因漂移频率与所选择的花粉受体品种有关,"石远321"(转基因棉亲本)(10.63%)作为花粉受体时基因漂移频率高于"中棉35"(2.50%);转基因棉花基因漂移频率随着转基因作物种植区与非转基因作物之间距离的增加而下降。本试验为风介导的基因漂移的生态风险评估提供一定的理论参考。     

玉米pepc基因在杂交转育的转基因水稻后代中的传递和表达特征

在合肥、海南两地以高光效转玉米pepc基因水稻为父本,与培矮64S、2302S、2304S、2306S、5129、02428、皖粳97和双九A等8个受体杂交,转育转pepc基因水稻新种质材料。至2002年已转育成一批转pepc基因水稻品系,对这些材料世代跟踪研究显示：(1)玉米pepc基因以一个显性基因稳定传递给后代,符合孟德尔分离规律,自交F2呈3：1分离,BC1为1：1分离;(2)玉米pepc基因在杂交转育的转基因水稻中高水平表达,与受体亲本相比,PEPC活性提高3.7～17．4倍,表达水平与受体亲本和转基因拷贝数有关,来源相同的世代间有相似的表达水平,但同一世代不同个体间表达水平有差异,这可能与其位置效应、拷贝数和环境条件有关;(3)杂交后代结实率不高,容易产生异交结实导致转基因材料混杂分离。采取抗生素催芽初筛、PCR分析抽检、PEPC活性测定和田间表型观测的转玉米pepc基因水稻选育筛选体系,辅之以受体为轮回亲本适当回交可有效地控制。利用该途径已育成3个稳定的高表达的转玉米pepc基因水稻品系H1596、H1597和Y1470,说明通过常规杂交转育的方法,可以培育实用的稳定高表达的转玉米pepc基因水稻品种。     

由RTS-barnase嵌合基因的表达导致的雄性不育水稻植株

用PCR方法从水稻品种IR36的总DNA中扩增了RTS基因 5’调控区 (- 12 2 8～ 2 5 )顺序并与从解淀粉芽孢杆菌 (Bacillusamyloliquefaciens)染色体DNA中克隆的RNase(barnase)基因编码区构建了嵌合基因 ,通过根癌农杆菌介导转化水稻品种ZH11,所获得转基因植株的主要性状与供体亲本无显著差异 ,但开花后药壁不开裂 ,并且大多数植株的花粉不被I KI染色 ;自交条件下结实率为零 ,表现为完全不育 ;而用空载体转化所得到的植株及未转化的对照植株则是可育的。转基因不育株经人工授以正常的花粉 ,可以获得杂交种子。F1代的遗传分析结果表明 ,以单拷贝整合于不育植株基因组中的RTS barnase嵌合基因可以通过杂交遗传并且雄性不育性状与其存在直接相关     

贯叶连翘的开花动态与繁育系统研究

野外观察贯叶连翘的开花进程和花部形态特征,运用花粉萌发、杂交指数、花粉-胚珠比等方法测定其繁育系统。结果显示:贯叶连翘雌雄异熟,柱头先花药成熟,雌雄蕊无明显异位。单花花期4～5d。仅在开花当日有昆虫传粉,蜜蜂为主要传粉者。花粉在花药开裂1h后活力最大,萌发率达40.10%,花粉在柱头萌发3h后接近子房。根据杂交指数(OCI)推测其繁育系统属于异交,部分自交亲和,有时需要传粉者。花粉-胚珠比(P/O)则表明贯叶连翘的繁育系统为兼性异交。贯叶连翘结实率低,可能与花粉活力,花粉管的生长速度及花粉在柱头的竞争有关。     

外源硅对花期高温胁迫下杂交水稻授粉结实特性的影响

以杂交中熟籼稻品种金优63、汕优63为供试材料,采用盆栽试验,在水稻生长前期连续喷施3次硅酸钠(Na₂SiO₃·9H₂O),于人工气候箱内在水稻开花期进行常温(日均温26.6 ℃,日最高温度29.4 ℃)和高温(日均温33.2 ℃,日最高温度40.1 ℃)处理5 d,研究施硅在花期高温胁迫下对杂交水稻剑叶叶绿素含量、光合性能、抗氧化酶活性、丙二醛(MDA)含量、花粉活力、花药酸性转化酶活性、柱头授粉性能和结实率等的影响.结果表明: 与对照相比,施硅可显著提高高温胁迫下水稻剑叶叶绿素含量,提高净光合速率和气孔导度,减少胞间CO₂浓度,增强叶片光合作用,减少MDA含量,提高超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性;提高花药中可溶性酸性转化酶活性和花粉活力,增加花粉囊基部裂口宽度,提高水稻每柱头上授粉总数、萌发数、花粉萌发率和萌发数大于10粒者所占的比例,降低花粉总数小于20粒者所占的比例;使金优63、汕优63结实率的降低分别减轻13.4%、14.1%.因此,在水稻生长前期喷施外源硅,可减轻水稻在开花期结实率的降低,提高杂交水稻的抗热性.     

Pollen source affects female reproductive success and early offspring traits in the rare endemic plant Polemonium vanbruntiae (Polemoniaceae)

Understanding the relative magnitudes of inbreeding and outbreeding depression in rare plant populations is increasingly important for effective management strategies. There may be positive and negative effects of crossing individuals in fragmented populations. Conservation strategies may include introducing new genetic material into rare plant populations, which may be beneficial or detrimental based on whether hybrid offspring are of increased or decreased quality. Thus, it is important to determine the effects of pollen source on offspring fitness in rare plants. We established pollen crosses (i.e. geitonogamous‐self, autonomous‐self, intrasite‐outcross, intersite‐outcross and open‐pollinated controls) to determine the effects of pollen source on fitness (seeds/fruit and seed mass) and early offspring traits (probability of germination, number of leaves, leaf area and seedling height) in the rare plant Polemonium vanbruntiae. Open‐pollinated, intrasite‐outcross and geitonogamous‐self treatments did not differ in fitness. However, plants receiving autonomous‐self pollen had the lowest fitness and the lowest probability of seed germination. Intersite‐outcross plants contained fewer seeds/fruit, but seeds germinated at higher frequencies and seedlings were more vigorous. We also detected heterosis at the seed germination stage. These data may imply that natural populations of P. vanbruntiae exhibit low genetic variation and little gene flow. Evidence suggests that deleterious alleles were not responsible for reduced germination; rather environmental factors, dichogamy, herkogamy and/or lack of competition among pollen grains may have caused low germinability in selfed offspring. Although self‐pollination may provide some reproductive assurance in P. vanbruntiae, the result is a reduction in germination and size‐related early traits for selfed offspring.     

Gene silencing using the recessive rice bacterial blight resistance gene xa13 as a new paradigm in plant breeding

Resistant germplasm resources are valuable for developing resistant varieties in agricultural production. However, recessive resistance genes are usually overlooked in hybrid breeding. Compared with dominant traits, however, they may confer resistance to different pathogenic races or pest biotypes with different mechanisms of action. The recessive rice bacterial blight resistance gene xa13, also involved in pollen development, has been cloned and its resistance mechanism has been recently characterized. This report describes the conversion of bacterial blight resistance mediated by the recessive xa13 gene into a dominant trait to facilitate its use in a breeding program. This was achieved by knockdown of the corresponding dominant allele Xa13 in transgenic rice using recently developed artificial microRNA technology. Tissue-specific promoters were used to exclude most of the expression of artificial microRNA in the anther to ensure that Xa13 functioned normally during pollen development. A battery of highly bacterial blight resistant transgenic plants with normal seed setting rates were acquired, indicating that highly specific gene silencing had been achieved. Our success with xa13 provides a paradigm that can be adapted to other recessive resistance genes.     

Introduction of a rice blight resistance gene,Xa21, into five Chinese rice varieties through anAgrobacterium-mediated system

A cloned gene, Xa21 was transferred into five widely-used Chinese rice varieties through an Agrobacterium-mediated system, and over 110 independent transgenic lines were obtained. PCR and Southern analysis of transgenic plants revealed the integration of the whole Xa21 gene into the host genomes. The integrated Xa21 gene was stably inherited, and segregated in a 3 : 1 ratio in the selfed T1 generation when one copy of the gene was integrated in the transfor-mants. Inoculation tests displayed that transgenic T0 plants and Xa21 PCR-positive T1 plants were highly resistant to bacterial blight disease. The selected Xa21 homozygous resistant transgenic lines with desirable qualities may be propagated as new varieties or utilized in hybrid rice breeding.     

Introduction of a rice blight resistance gene, Xa21, into five Chinese rice varieties through an Agrobacterium-mediated system

A cloned gene, Xa21 was transferred into five widely-used Chinese rice varieties through an Agrobacterium-mediated system, and over 110 independent transgenic lines were obtained. PCR and Southern analysis of transgenic plants revealed the integration of the whole Xa21 gene into the host genomes. The integrated Xa21 gene was stably inherited, and segregated in a 3∶1 ratio in the selfed T1 generation when one copy of the gene was integrated in the transformants. Inoculation tests displayed that transgenic T0 plants and Xa21 PCR-positive T1 plants were highly resistant to bacterial blight disease. The selected Xa21 homozygous resistant transgenic lines with desirable qualities may be propagated as new varieties or utilized in hybrid rice breeding.     

No effect of transgene and strong wild parent effects on seed dormancy in crop–wild hybrids of rice: implications for transgene persistence in wild populations

Soil seed banks act as a gene pool for local plant species and, as such, can buffer local populations, especially those experiencing challenging environmental conditions. Seed dormancy has important implications to dynamics of soil seed banks. Therefore, estimating the seed dormancy of transgenic crop–wild hybrids could shed light on the persistence of transgenes in wild‐plant soil seed banks. Individuals from eight populations of wild rice Oryza rufipogon were crossed with those of three insect‐resistant transgenic rice lines. Selfed (F2–F4) and backcrossed populations (BC1, BC1F2 and BC1F3) were then made from the hybrids. Seed germination was tested under three treatments: (a) normal; (b) overwintering in soil; and (c) one‐week heat‐shocking. The effects of transgene, wild parent and hybrid generation on hybrid seed germination were examined. No significant effect of insect‐resistant transgenes (Bt and CpTI) was detected on the seed dormancy of crop–wild hybrids, while a significant wild parent effect was found. The seeds of advanced generation hybrids have higher germination percentages and lower dormancy than do those of F1 and BC1 generations. The study showed that the dormancy of hybrid seeds was determined mainly by their genetic backgrounds. All hybrid seeds have higher germination percentages and lower dormancy (and, consequently, a poorer overwintering ability), compared with wild seeds, and reduce dormancy would contribute to a fitness disadvantage, compared with wild types. Therefore, such seeds might form part of naturally occurring soil seed banks, through which crop genes would persist in wild populations.     

FITNESS CONSEQUENCES OF MIXED-DONOR POLLEN LOADS IN THE ANNUAL LEGUME CHAMAECRISTA FASCICULATA

We experimentally examined the effects of pollen composition on progeny fitness in the self-compatible, annual plant Chamaecrista fasciculata. Plants were hand-pollinated with single- and mixed-donor pollen loads and with various combinations of self- and outcross pollen. For outcrosses, pollen was obtained from two plants at each of two different distances within the same subpopulation as the female parent. Seedlings from all crosses were planted back into the maternal site. For single-donor crosses, seed weight, progeny fruit production, and overall relative fitness were significantly higher for outcross, as compared to self-treatments, but we found no significant differences among outcross sources. For all fitness components, the value observed for crosses derived from mixed loads was intermediate between the values for the singledonor crosses that comprised the mixed load. In a parallel experiment, an analysis of seed paternity of progeny which resulted from pollen mixtures of self- and outcross pollen showed random paternity in two maternal families, and significant excess of outcross in one family. Our results demonstrate that mixed pollen loads do not confer a fitness advantage to the maternal plant in this species, and that the fitness observed for progeny derived from mixed loads is generally consistent with a hypothesis of random paternity.     

Intra-inflorescence variation in floral traits and reproductive success of the hermaphrodite Silene acutifolia

BACKGROUND AND AIMS: Intraspecific variation in floral components and reproductive success is often located at the intra-individual level. The arrangement of flowers within inflorescences may explain a great deal of this variation. The variation in number of ovules, fruit set, number of seeds per fruit, seed set, seed weight and seed germination is investigated at different positions within the inflorescence of Silene acutifolia. METHODS: Data were obtained in natural populations, and germination experiments were conducted in a germination chamber. KEY RESULTS: The number of ovules, fruit set, number of seeds, seed set and seed weight, showed a significant decline from early (primary) position to later (tertiary) position. The patterns of intra-inflorescence variation were consistent in different populations and years of study. Seed germination showed an opposite pattern, seeds from primary position showed the lowest germination percentages and seeds from tertiary position the highest, although the effect of position on germination was only marginally significant. There was significant among-population variation in number of ovules per flower. Fruit set also varied significantly among populations, with lower fruit set in the smaller and more isolated population. No significant among-population differences were detected in number of seeds per fruit and seed set. Seeds from the smallest and more isolated population (Arnado) were the lightest. Seed germination showed strong differences between populations, seeds from Arnado started to germinate later, and showed the lowest final germination percentages. CONCLUSIONS: Architectural effects or resource competition are the most commonly proposed hypothesis to explain these patterns. Data suggest that there is less pollen available to pollinate tertiary flowers, and that there is not enough outcross pollen in Arnado. The germination percentages suggest that there is variation in the source of pollen within inflorescences, with high probability of receiving outcross pollen in flowers from primary position, and higher probability of geitonogamous crosses in tertiary flowers.     

基因枪转化获得的转基因水稻中外源基因整合与表达规律研究

通过基因枪法将cecropin B和bar基因共转化水稻,获得多个水稻优良品系的转化材料,对转基因的结构和表达的系统分析,发现外源基因的整合模式多种多样,有简单也有复杂,其中插入位点数的变化范围为1－7个,拷贝数的变化范围为1－10个,转基因拷贝数的多少与其表达和沉默不存在必然的联系,相同整合模式的转基因事件中基因的表达存在较大的差异,选择标记基因bar比非选择标记基因cecropin B的表达框的完整性和转录概率要高,但是发现大部分表达框完整的bar基因发生基因沉默,而在终止子发生序列丢失的cecropin B基因的表达则明显提高。     

COSTS OF SELF-POLLINATION IN A SELF-INCOMPATIBLE PLANT,POLEMONIUM VISCOSUM

Plants of Polemonium viscosum are strongly self-incompatible, yet have floral features that enforce spatial and temporal separation of pollen and stigma presentation. In this study, we address the widely held view that such barriers to selfing are maintained because they reduce interference by self pollen in performance of outcross grains. In the first year of the study we found that 24 hr precedence of self pollen on the stigma (24S), reduced outcross pollen germination by 32%, and seed set by 40% in flowers of P. viscosum. In the second year significant negative effects of self pollen on compatible pollen germination were seen when self pollen was applied four hours before (4S) or immediately prior (S×) to outcross pollen. Surprisingly, however, in the second year of study, seed set was not reduced with as much as 50% inhibition of compatible pollen germination. Results suggest that by interfering with normal functioning of outcross grains, incompatible self pollen can increase pollen limitation in P. viscosum. Reduction in seed production as a result of this phenomenon should select for displacement of pollen presentation from stigma receptivity.     

Fitness estimation through performance comparison of F1 hybrids with their parental species Oryza rufipogon and O. sativa

BACKGROUND AND AIMS: Introgression of crop genes into populations of wild relatives has important implications for germplasm conservation as well as for the persistence of novel transgenes in wild populations. Studies of hybrid fitness can be used to evaluate the potential for introgression to occur following episodes of interspecific hybridization. METHODS: This study estimated relative fitness of interspecific hybrids through performance comparison of F(1) hybrids with their parental species, a cultivated rice (Oryza sativa) Minghui-63 and perennial common wild rice (O. rufipogon) under the cultivation conditions. KEY RESULTS: Compared with their parents, the hybrids had the lowest values of seedling survival ability, pollen viability and seed production; intermediate values of seed germination, spikelet production and flag leaf areas; and the highest values of plant height, number of tillers and panicles. The hybrids performed poorly at the stage of sexual reproduction, although they had a slightly higher hybrid vigour at the vegetative growth stage and better tillering ability than their wild parent. There were no significant differences in composite fitness across the whole life-history between the hybrids and their wild parental species. CONCLUSIONS: Rice genes, including transgenes, might persist in wild rice populations through vegetative and sexual reproduction. Further studies are needed to examine whether the extent of gene flow from rice is sufficiently significant to influence genetic diversity in wild populations of O. rufipogon, a species that has become endangered in some regions of south-east Asia.