Maternal and embryonal control of seed colour by different Brassica alboglabra chromosomes

Most oilseed rape, Brassica napus, cultivars are black‐seeded. The progenitor species, Brassica rapa, has either yellow or black seeds, while known cultivars of the other progenitor species Brassica oleracea/alboglabra have black seeds. To determine which chromosomes of B. alboglabra are carriers of seed colour genes, B. rapaalboglabra monosomic addition lines were produced from a B. napus resynthesized from yellow‐seeded B. rapa and brown/black‐seeded B. alboglabra. Eight out of nine possible lines have been developed and transmission frequencies of the alien chromosomes were estimated. Three B. alboglabra chromosomes in three of these lines influenced seed colour. B. rapa plants carrying alien chromosome 1 exhibited a maternal control of seed colour and produced only brown seeds, which gave rise to plants with either yellow or brown seeds. However, B. rapa plants carrying alien chromosome 4 or another as yet unidentified alien chromosome exhibited an embryonal control of seed colour and produced a mixture of yellow and brown seeds. The yellow seeds gave rise to yellow‐seeded plants, while the brown seeds gave rise to plants that yielded a mixture of yellow and brown seeds, depending on the absence or presence, respectively, of the B. alboglabra chromosome. Consequently, both maternal and embryonal control of seed colour are expected to contribute to the black‐seeded phenotype of oilseed rape.     

Reducing potential gene escape in time by appropriate post-harvest tillage—Evidence from field experiments with oilseed rape at 10 sites in Europe

Persistence of oilseed rapeseed in soil can result in weed problems but also reduce oil quality of following rape crops or result in unwanted gene escape which is particularly relevant in the context of genetically modified oilseed rape. In this paper data from 13 field experiments at sites in England, Austria and Germany are presented where tillage operations were tested that potentially reduce the build-up of a seed bank. In the majority of experiments seed losses were artificially simulated by broadcasting ca. 10,000 freshly ripened rapeseed m⁻² onto cereal stubbles. Oilseed rapeseedlings in autumn, the seed bank in winter–spring and yields of the following crop winter wheat were assessed as a function of tillage regime. During summer and autumn 19–70% of the seeds germinated and emerged. This part of the population was killed by following tillage operations or herbicide applications. However, 0–29%, in moist years 0–5%, of the initially broadcasted seeds developed dormancy and remained ungerminated in the soil until the following winter–spring.

Delaying incorporation of the seeds by leaving the stubble untouched for up to 4 weeks resulted in a reduced seed bank in almost every case. Also, repeated stubble tillage compared to an early single stubble tillage operation resulted in a smaller seed bank. The type of primary tillage (ploughing versus non-inversion cultivation) had no clear effect. No relation was found between the number of seedlings in autumn and the size of the seed bank the following winter–spring. Grain yield of the following crop winter wheat was not adversely affected by delayed stubble tillage.

The results indicate that stubble tillage aiming at a reduced seed bank of oilseed rape should focus on conditions avoiding induction of secondary dormancy rather than improving germination conditions. This means that, under the climatic conditions of central and western Europe, the stubble should be left untouched for several weeks after harvest before starting the usual tillage sequence with stubble tillage and ploughing or a non-inversion tillage sequence.     

Population dynamics of volunteer oilseed rape (Brassica napus L.) affected by tillage

Volunteer plants of oilseed rape (Brassica napus L.) from persistent seeds in soil can affect subsequent crops. Apart from the agricultural disadvantages, the environment and the marketing of the seeds may also be affected, particularly if plants with special ingredients or genetically modified (gm) plants are grown. In order to investigate the influence of soil cultivation and genotype on seed persistence and gene flow via volunteers, a field experiment was set up testing four tillage treatments and two cultivars in a split-plot design. The cultivars tested were near-isogenic to two gm cultivars. To simulate harvesting losses, 10 000 seeds m⁻² were broadcast on a soil in July. The subsequent tillage treatments were combinations of immediate or delayed stubble tillage by a rotary tiller, primary tillage with plough or cultivator, or zero tillage. Over the following year, the fate of the seeds was determined. Immediate stubble tillage with following cultivator or plough resulted in 586 resp. 246 seeds m⁻² in the soil seed bank. After delayed stubble tillage with following plough, 76 seeds m⁻² were found, and no soil seed bank was built up in the zero tillage treatment. Nevertheless, in the zero tillage treatment, several robust volunteer plants survived the herbicide application before the direct drilling in autumn until following spring. In the zero tillage treatment and in the cultivator treatment, 0.19 volunteers m⁻² resp. 0.06 volunteers m⁻² flowered simultaneously to ordinarily sown oilseed rape in the following crop of winter wheat and produced 73 resp. 18 seeds m⁻². Delayed stubble tillage reduced the risk of gene escape via the soil seed bank, while zero tillage resulted in the highest risk of gene escape by pollen and by production of a new generation of seeds. In terms of a labelling threshold for gm food this number of seeds would be below the threshold of 0.9% of transgenic parts in conventially bred food or feed.     

温度、CaCl2和光照解除桑树种子次生休眠的效果分析

以黑龙江省农家桑树的种子为试验材料,研究了外源钙浸种、提高温度和光照等对解除桑树种子次生休眠的影响.结果表明,常温(25℃)条件下,25 mmol/L CaCl2浸种24 h,可提高桑树种子的发芽率,其中,未休眠桑树种子的发芽率由81％提高到97％,次生休眠的桑树种子的发芽率由16％提高到44％.在25 mmol/L CaCl2浸种基础上进行不同温度(25,28,30,35,37℃)处理,以及相同温度下照光和遮光处理,进一步探讨次生休眠的桑树种子萌发对温度和光照的响应.结果表明,次生休眠的桑树种子的发芽率、发芽势和发芽指数随着温度的升高呈现先升高后下降的趋势,35℃温度处理的发芽率达到最高,可达90％左右,说明提高温度是解除桑树种子的次生休眠的有效方法.桑树种子萌发对光照不敏感,且照光对桑树种子的根长和茎长生长具有抑制作用.     

滇重楼种子休眠机理研究

探讨滇重楼种子休眠机理,为打破种子休眠促进滇重楼实生育苗提供理论基础。采用重量法、胚率测定、ELISA等方法对种子吸水特性、萌发抑制物及种胚休眠与发育的内源机理进行了研究。结果表明,滇重楼种子休眠属于形态学-生理学休眠类型。滇重楼种胚发育不完全、种子中存在萌发抑制物质是种子休眠的主要原因。种子不存在吸水障碍,与休眠无关。内源激素ABA和GA3在滇重楼种子休眠与萌发过程中起着重要作用,ABA是引起休眠的关键因素,ABA含量的降低是滇重楼种胚发育的始动因子,GA3有助于种子的生理后熟。萌发抑制物的存在可能抑制了种胚发育,而与生理学后熟过程无关。在自然条件下,滇重楼生境中较长的低温时期可能是滇重楼种子具有较长时间休眠的外界原因。     

The genetic relations between length of time to germination and seed dormancy in lisianthus (Eustoma grandiflorum)

Summary The inheritance of speed of germination and its genetic relations with seed dormancy was investigated in lisianthus (Eustoma grandiflorum). The study was based on data from parental, F1, BC1F1 and F2 generations of a cross between a normally germinating genotype (P1) and a chill-requiring genotype (P2). The mean post-chilling germination speed of P2 was considerably lower than that of P1. Germination speed was found to be under nuclear embryonic control. Analysis of generation means for prechilled seeds revealed an additive gene action with complete dominance of the alleles conferring higher germination speed, since the means of the F1 and the BC1 (P1) were indentical to that of P1. Such dominance was not found for unchilled seeds, in which the mean germination speed of the F1 and the BC1 (P1) was lower than that of P1. It was hypothesized that slow germination speed was induced by pleiotropic effects of seed dormancy alleles. Seed prechilling seemed to eliminate these effects in progeny heterozygous for dormancy alleles, but not in progeny homozygous for dormancy alleles.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, No 1292-E, 1993 series.     

乙烯的生物合成与信号及其对种子萌发和休眠的调控

种子萌发是一种关键的生态和农业性状,由调控种子休眠状态和萌发潜势的内在和外部信息所决定,在植物随后的生长发育和产量中起着极其重要的作用。休眠是指种子在合适的条件下暂时不能萌发。乙烯是一种简单的具有多种功能的气体植物激素,在分子、细胞和整体植物水平调节植物的代谢。在适宜和逆境条件下,乙烯通过与其他信号分子的相互作用影响植物的行为。本文主要综述乙烯的生物合成与信号、乙烯在种子萌发和休眠释放中的作用以及乙烯与植物激素脱落酸和赤霉素的相互作用;并提出了需要进一步研究的科学问题,试图为解释乙烯调控种子萌发与休眠的分子机制提供新的研究思想。     

Temperature effects on seed germination and expression of seed dormancy in wheat

Because preharvest sprouting decreases quantity and quality of wheat grain, researchers need effective protocols to assess response to preharvest sprouting conditions. The aim of this study was to determine which temperature gives the greatest difference in seed germination and expression of seed dormancy in 10 spring wheat genotypes. The genotypes were grown in the field near Swift Current, Saskatchewan in 2000 in a randomized complete block with four replicates. Seed samples were harvested at approximately 25% moisture content (wet weight basis) and dried to 12% moisture content with minimal after-ripening. Germination was under controlled environment at temperatures of 10, 15, 20 and 30 °C in darkness. A weighted germination index (WGI) was calculated. The analysis of WGI, for each temperature, showed highly significant (p ≤ 0.01) genotype effects on germination. Most genotypes decreased in WGI (increased dormancy) as temperature was increased from 10 to 30 °C. The greatest differences in seed germination tended to be at 15 °C and 20 °C. The level of seed dormancy depended on the genotype and germination temperature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evolution of weed beet (Beta vulgaris L.) seed bank: Quantification of seed survival,dormancy, germination and pre-emergence growth

Weed beet is an important weed of sugar beet crops. Weed and cropped beets can cross easily and the management of weed beet is therefore crucial in the case of the advent of GM sugar beet, especially herbicide-tolerant cultivars, in order to ensure the co-existence of GM and non-GM crops and to avoid the appearance of herbicide-resistant weed beet. The inability of weed beet to compete in most other crops of the rotation makes the seed bank evolution a crucial stage of the life-cycle because in the rotation, sugar beet is at the most cultivated only every 3 years. The present study used seed burial experiments and laboratory analyses to characterise each step of the evolution of the weed beet seed bank and the external factors that could modify seed persistence in the soil. A monthly seed mortality of 10% was observed between October and December, while mortality was nil during the other seasons. Equations were then developed to describe the observed seasonal variations in seed survival. Seed dormancy also varied with season: the proportion of non-dormant seeds increased during winter (appearance of secondary dormancy) and decreased during the remaining seasons (loss of dormancy). In addition, the germinating seeds decreased with seed age and seed depth, while the presence of light stimulated germination. These observations were also translated into equations. Last, the pre-emergence hypocotyl growth and its variability were studied according to seed age, but no significant effect was observed. The results confirm the importance of the effects of cropping system on the evolution of the weed seed bank, especially the effect of soil tillage, which determines the date and conditions of seed burial, seed excavation and germination stimulation.     

水青冈种子萌发研究

水青冈是我国中亚热带常绿阔叶林中的优势树种之一,其成熟林内尽管每年有大量种子散落,但实生苗极少.本研究比较4种打破水青冈种子休眠的方法,结果表明:(1)种子种皮切伤和去除种皮后,发芽率增大,均超过了90.0%,并提早12 d萌发;(2)100ms/L的赤霉素浸种效果最好,发芽率为72.2%,提早5 d萌发;(3)随着低温干藏时间的延长,水青冈种子的发芽率也提高;(4)经40℃处理后种子的萌发效果最好,发芽率达76.8%.     

光照和沙埋对沙生针茅种子萌发与幼苗出土的影响

为了对沙生针茅种子萌发特征和休眠机理的研究,采用种子萌发学和实验生态学方法,研究了不同光照、划破种（果）皮及切除不同比例胚乳对种子萌发的影响和模拟野外条件对不同沙埋深度幼苗出土的影响。结果表明：黑暗条件下种子萌发率显著高于光条件下;移走胚乳75%时,种子萌发最快;不同沙埋深度以0.5 cm的浅层沙埋时的种子萌发率和幼苗出土率最高而休眠率最低;沙埋超过2 cm后,种子萌发率、幼苗出土率与沙埋深度呈负相关,休眠率随着沙埋深度的增加而增加。说明沙生针茅种子为休眠型暗条件萌发类型。人工播种应以0.5~2 cm深度为宜。     

Heat stress during seed development affects forage brassica (Brassica napus L.) seed quality

In two consecutive seasons, forage rape (Brassica napus L.) plants were exposed to short periods (240°C hr) of heat stress (30°C day/25°C night) during seed filling (80% seed moisture content = S1), at physiological maturity (50% seed moisture content = S2) and at both S1 plus S2 (=S3) in a Biotron before being returned to the field until seed harvest. Seeds were hand harvested at 14% seed moisture content and their quality assessed by measuring germination, seed vigour (using the accelerated ageing and conductivity tests) and seed mass (as determined by thousand seed weight). Heat stress at both S1 and S2 caused a small (<10%) but significant reduction in germination in both seasons. There was a significant heat stress timing interaction in the first but not the second season. Reductions in germination were a result of increased abnormal seedling production not seed death. All three heat stress treatments significantly reduced seed vigour, with S3>S2>S1. Seed mass was reduced by heat stress at S1 but not at S2. Variable seed vigour in high‐germinating New Zealand‐produced forage rapeseed lots is most likely explained by short periods of heat stress during seed development.     

多花黄精种子结构与休眠及萌发的关系研究

本实验主要针对多花黄精种子的形态学结构、内含物等进行研究,使用机械法去除种皮及化学试剂去除种皮束缚,以探究多花黄精种子结构及其休眠类型与萌发之间的关系。结果表明,多花黄精种子粒径大小为(3.950±0.422)mm×(3.683±0.404)mm。鲜种子千粒重为(25.036±2.117)g,生活力为(83.33±5.51)%,鲜种子含水量为(45.29±2.76)%,种子吸水4 d后可达饱和;10%硫酸处理种子1 min为最佳处理方式,可有效打破休眠状态,并提高萌发率。     

厚皮甜瓜‘翠雪5号’种子破休眠方法研究

厚皮甜瓜‘翠雪5号’新收获种子存在休眠现象,采用自动破休眠、高温、低温冷冻以及外源激素等处理进行种子萌发试验,以期找出破除‘翠雪5号’种子休眠、提高种子发芽率的方法。结果表明,‘翠雪5号’种子的休眠解除主要依赖于自动破休眠过程,高温处理可加速该过程。另外,低温冷冻以及外源NAA和GA₃处理不能破除‘翠雪5号’的种子休眠、提高萌发率,而外源6-BA可以在延长发芽时间的基础上显著促进种子萌发。     

Plasticity of seed weight compensates reductions in seed number of oilseed rape in response to shading at flowering

Understanding the response of the number of seeds and seed weight to the availability of assimilates is crucial for designing breeding strategies aimed to increase seed and oil yield in oilseed rape. This study aims to answer the questions: i) do seed number and seed weight in oilseed rape differ in their plasticity in response to the availability of assimilates at flowering? and ii) how sensitive are oil and protein concentrations to the availability of assimilates during flowering?A spring oilseed rape hybrid was sown in two field experiments and the treatments were combinations of i) two plant densities and ii) shading or no shading between the beginning and end of flowering. Seed yield was not affected by plant density or by shading. Lower plant density was compensated by an increase in seed number per plant, without effects on single-seed weight. However, the negative effect of shading during flowering on seed number per area was fully compensated by an increase in single-seed weight by 47–61%. The plasticity of single-seed weight observed in the present study of oilseed rape has never been reported for annual seed crops. Shading at flowering increased both the seed filling rate and the duration of the seed filling period at all positions in the canopy. We also observed that the reduction of the source-sink ratio at flowering increasing seed weight does not necessarily modify oil or protein concentrations. Thus, single-seed weight could be targeted to increase seed yield in oilseed rape without compromising oil content.     

华重楼种子预处理对其萌发特性的影响

目的:筛选华重楼种子最佳预处理方法,为生产上及早破除种子休眠,促进种子萌发提供指导.方法:新鲜的华重楼种子经不同去皮方式、不同层积基质及不同浸种药剂处理后,于18℃层积条件下进行发芽试验,每周观察并记录,比较分析种子的发芽率、发芽势、平均发芽天数的差异.结果:与带皮种子相比,冷冻去皮可显著缩短种子平均发芽天数,而砂搓、纱布、手剥去皮的种子发芽率和发芽势均有显著降低;与壤土基质相比,细砂、蛭石、木屑层积的种子发芽率及发芽势均有显著提高,且蛭石基质层积可显著缩短平均发芽天数;NaN3、H2O2、KNO3浸种处理均能显著提高种子发芽率.结论:华重楼生产上宜采用冷冻法去除种子外种皮,使用0.001％浓度的H2 O2浸种14 h后于18℃蛭石中层积.     

Quantitative trait locus analysis of seed germination,seedling vigour and seedling‐regulated hormones in Brassica napus

Good germination and seedling vigour are major breeding targets in winter oilseed rape (Brassica napus), because seedling vigour and prewinter crop establishment are closely associated with postwinter growth and yield. Here, we identified quantitative trait loci (QTL) related to germination, seedling vigour and seedling‐regulated hormones in a doubled haploid (DH) mapping population from a cross between winter oilseed rape parents with high vigour (Express 617) and low vigour (1012‐98). By phenotyping in a climate‐controlled glasshouse, we identified a total of 13 QTL on nine chromosomes for germination and seedling‐related traits at 7 and 14 days after sowing (DAS), explaining up to 11.2% of the phenotypic variation for seedling vigour. Forty‐seven metabolic QTL on 15 chromosomes were identified for auxin, abscisic acid (ABA) and dihydrophaseic acid (DPA) at 5 and 12 DAS, explaining up to 49.4% of phenotypic variation in seedling hormone composition. Multitrait QTL hot spots contribute to our understanding of the genetics and metabolomics of germination and seeding vigour in B. napus, and represent potential targets to breed high‐vigour cultivars.     

铁棒锤种子发芽抑制机理及解除方法研究

目的:揭示铁棒锤种子发芽抑制机理,探寻提高种子发芽率的方法。方法:通过铁棒锤种子中生物碱类物质对油菜种子发芽率及生长情况的影响,明确铁棒锤种子的休眠机理;测定不同浓度的GA₃处理对铁棒锤种子发芽率的影响。结果与结论:铁棒锤种子中的发芽抑制物质为生物碱,适宜浓度的GA₃处理能打破休眠,且以400 mg/kg GA3处理14 h效果最好,发芽率达到91%。     

多花黄精种子萌发过程的形态和解剖研究

为解除多花黄精种子休眠、促进种子萌发,利用Nikon-SMZ 800体式显微镜观察多花黄精种子不同萌发时期的外观形态,采用石蜡切片法将多花黄精种子特殊部位制成切片,在Olympus-BX 61光学显微镜下观察其解剖结构,探究多花黄精种子萌发过程中的形态变化及解剖特征。结果表明,1)多花黄精种子萌发过程可分为:刚采摘、未萌发、刚萌发、小球茎形成、初生根茎形成和出苗6个阶段;2)成熟的多花黄精种子,其胚未分化出明显的子叶、胚芽和胚根,随着种子的萌发而分化成成熟胚;3)多花黄精种子的萌发伴随着胚乳的降解;4)多花黄精种子同时存在生理休眠和形态休眠,具有形态生理休眠特性。     

不同处理对褐鳞苔草种子萌发的影响

为摸清褐鳞苔草种子的休眠机理、萌发过程,解决种子繁育难题,对褐磷苔草种子用物理（热水浸种、机械处理、层积催芽）、化学（浓H2SO4浸种、NaOH溶液处理、GA3处理）及综合方法处理后进行萌发试验。结果表明：褐磷苔草存在休眠,且休眠程度较高,使用10%NaOH溶液可以打破休眠,将自然条件下不萌发的种子发芽率提高到13.75%,其次是切破种皮+GA3 1000 mg/L,种子发芽率达到12.5%。