Medium-term seed storage of 50 genera of forage legumes and evidence-based genebank monitoring intervals

Genebanks maintaining seeds for long-term genetic resources conservation monitor seed lots to detect early loss in viability. Monitoring is costly and depletes valuable seed. Three decades of genebank seed germination test results of diverse forage species from 50 legume genera in the International Livestock Research Institute’s medium-term store (circa 8 °C with 5% moisture content) were analysed to determine whether advice on seed monitoring intervals could be derived. Cumulative normal distributions were fitted by probit analysis for each seed lot and compared within each genus. Six patterns of within-genus variation were identified: no detectable trend in germination test results during storage (4 genera); detectable trends, but variable (positive to negative) amongst lots (5); consistent slope of loss in viability amongst lots (17); consistent slope of increase in ability to germinate amongst lots (21); common loss in viability amongst lots (2); common increase in ability to germinate amongst lots (1). Seed lot monitoring intervals for the medium-term store were derived for each of 19 genera with consistent loss in viability across seed lots: three genera provided comparatively rapid deterioration, five met the general expectations for a medium-term store (2–10 years’ maintenance of high viability), whilst 11 provided much better survival. Moreover, 26 further genera provided no evidence as yet of seed deterioration; of these, 22 improved in ability to germinate during storage indicating confounding of hardseededness with viability in germination tests.     

内蒙古自治区柠条种子害虫为害情况及其对柠条种子质量的影响

2003年对内蒙古自治区各柠条产区种子害虫为害情况的系统调查研究结果表明,柠条种子害虫在内蒙古自治区从东到西各调查样地普遍发生,均为柠条种子小蜂(Bruchophagus neocaraganaeLiao)、柠条豆象(Kytorhi-nus immixtusMotschulsky)、豆荚螟(Etiella zinckenellaTreitschke)3种害虫混合为害,所调查地区各样地为害程度均在 以上,平均种子虫害率为26.53%,虫株率达100%;进行了虫害对种子质量的影响评价试验,结果表明,平均每千粒种子因虫害损失掉的重量是3.12 g,种子发芽率平均降低了9.51%。     

Light- and Temperature-Dependent Dormancy in Stored Seed of Poa pratensis L. from Northern Norway

Abstract

Seed dormancy and slow germination often cause poor establishment of Poa pratensis L. in lawns and pastures. This study was conducted to determine whether persistent dormancy occurs and the influence of light and temperature on germination of Poa pratensis L. strains from Northern Norway. Seed from 23 different genotypes and seed lots was germinated in various phytotron chambers during the winters of 1986 and 1990. At 21°C constant temperature, dormancy was evident even after seven years of storage in a dry room at 0–10°C. By contrast, alternating temperatures (21/12°C) elicited 80–100% germination of viable seed of nearly all genotypes and seed lots. Light treatment had no impact on germination after 28 days at 21/12°C, but continuous darkness and continuous fluorescent light were both inferior to 8 h light/16 h dark illumination cycles at 21°C constant temperature. Seed of the commercial cultivar Lavang produced in Southern Norway developed the same long-term, temperature-dependent dormancy as seed produced in Northern Norway. One lot of the cultivar Holt showed a higher ability to germinate at low temperatures than any of the other genotypes.     

Preservation of seed viability during 25 years of storage under standard genebank conditions

Maintaining sufficient viability is critical to the sustainability of ex situ conserved seed collections. For this reason, accessions are regenerated when viability falls below a predefined threshold. Viability is monitored by determining the germination ability of accessions at predefined time intervals. Optimizing the frequency of these germination tests, in order to avoid waste of resources, is hampered by the scarce availability of data about seed longevity, particularly for material maintained under genebank conditions. Here we report on the analysis of nearly 40,000 germination test results collected for a wide range of crop species over a 25-years period by the centre for genetic resources, the Netherlands (CGN), where seeds of genebank accessions are dried to 3–7 % moisture content and stored for the long term under near-vacuum in aluminium foil bags at ?20 °C. The results indicate that seed viability is well maintained for the large majority of seed lots during the first 25 years after regeneration as only 3.3 % of the monitoring tests revealed below-threshold germination values. It is argued that the majority of these sub-standard seed lots are due to other causes than seed ageing, including dormancy problems and estimation error in germination testing. For material, maintained under the seed management procedures and storage conditions practiced by CGN, it is therefore recommended to delay the first germination monitoring tests to 25 years after regeneration.     

内蒙古自治区鄂尔多斯高原茭蒿种子萌发特性研究

通过对内蒙古自治区鄂尔多斯高原的茭蒿与其他2种蒿属植物种子萌发特性的对比研究。结果表明,茭蒿种子质量很小,千粒重仅为(0.090 1±0.005 1)g,这种特性有利于其种子的传播;茭蒿种子质量虽然很小,但在相同条件下,与其他植物种子发芽率并没有表现出显著差异,即种子质量的大小没有对茭蒿种子的萌发造成影响。茭蒿在拥有小种子的同时又具有高的种子萌发率,是其对黄土丘陵沟谷的有效适应途径。     

人工诱导的同源四倍体西瓜种子形态结构变异研究

四倍体西瓜作为三倍体无籽西瓜的母本,其性状对三倍体西瓜组合选配起着重要作用,其中四倍体西瓜种子性状对三倍体西瓜品种的种子发芽率、成苗率、采种量起关键作用。为研究四倍体西瓜种子的性状变异,以41组秋水仙素诱导的T6同源四倍体西瓜为试验材料,以其诱导前的同源二倍体为对照,比较加倍后四倍体西瓜种子发芽率、单瓜种子数、百粒重和形态结构变异。结果表明,秋水仙素诱导加倍后,四倍体种子发芽率、单瓜种子数均低于其同源二倍体,但种子长度、宽度、厚度、喙宽、种皮厚度和百粒重均大于其二倍体。四倍体西瓜的单瓜种子数与其二倍体西瓜的种子数极显著相关,二倍体和四倍体西瓜的百粒重与其本身的长度和宽度极显著相关,四倍体西瓜种子种皮厚度与多个性状都显著相关,但四倍体种子的发芽率除与其种子的喙宽显著相关外,与其他性状都无显著相关性。本研究通过比较人工诱导的同源四倍体与其原始二倍体西瓜种子的差异,为诱导四倍体的选择及多倍体西瓜育种提供了一定的理论依据。     

Effects of seedbed properties on crop emergence: 1. Temporal effects of temperature and sowing depth in seedbeds with favourable properties

Abstract

Rapid and uniform crop establishment is a prerequisite for efficient crop production and minimal environmental impact. Experiments were carried out in shallow plastic boxes placed directly on the ground in the field for studies of the effects of seedbed properties on emergence of various crops. This paper presents an analysis of the time required for germination and emergence under near-optimal seedbed conditions. The crops studied were barley, oats, wheat, pea, rape seed, white mustard, sugar beet, red clover and timothy. The time required for germination generally increased with size of the seeds, presumably because larger seeds needed more water to initiate germination. This applied both when comparing different crops and different seed sizes of the same crop. However, considerable differences occurred between seed lots of the same crop and there were greater differences between seed lots of the same crop than between the three small grain crops studied. Growth rate of the seedlings generally increased with seed size, presumably because of increased energy content in the seed. Consequently, the most rapid emergence was obtained from small seeds at shallow sowing and from large seeds at deep sowing. The crops studied had a minimum temperature for germination and seedling growth close to 0 °C. Under optimal seedbed conditions, thermal time required for 50% germination of barley was typically about 65 °C days over this base temperature and for seedling growth about 6 °C days cm^?1. From 4 cm sowing depth, about 80 °C days were required for emergence but with considerable variations between seed lots. For rape seed or white mustard about 40 °C days were required for germination and about 8 °C days cm^?1 for the seedling growth.     

The effect of soil fertility and harvesting stage on maize seed quality under rain-fed conditions

Abstract

Management practices during seed development are crucial for boosting seed quality and establishment. This study determined the interactive effect of soil fertility and maturity stage on maize seed quality. The cultivar SC701 were harvested at milk, dent, and physiological maturity stages and dried to <12% moisture content. Field trials were split plots replicated four times. Seed quality was evaluated using standard germination test, vigor indices and electrical conductivity test. Highly significant interactions (p?相似文献   

~(60)Coγ辐射对野牛草干种子的刺激生长效应

用不同剂量(25～300Gy)60Coγ射线辐射野牛草干种子,对辐射后干种子的发芽情况和幼苗的性状进行了室内和田间观测,结果表明:辐射可促进干种子萌发,特别是100Gy辐射剂量可明显提高种子的发芽率;对田间出苗率,幼苗的根长、高度而言,150Gy是其临界点;辐照剂量在100Gy以下对幼苗的茎叶和根系鲜重有促进作用;因而,从实验结果中我们初步确定促进野牛草种子萌发适宜的辐射剂量为100～150Gy。     

Seed consumption by millipedes

Seed predation is a key mortality factor for plants that reproduce by seeds. We investigated seed consumption by Cylindroiulus caeruleocinctus (Wood, 1864), an abundant representative of an unrecognised group of seed predators – the millipedes (Diplopoda: Julidae). The consumption of small seed species by millipedes was measured in the absence (41 species) and in the presence (11 species) of alternative food sources (dead leaves). We examined whether millipedes would consume seeds at all and if so whether there were any seed size constraints that determined millipede seed acceptance (i.e., the proportion of millipedes that ate seeds) and seed consumption (i.e., the mass of the seeds eaten). Our results indicated that C. caeruleocinctus readily accepted seeds with 75% of seed species accepted in a no-choice experiment and 100% of seed species in a choice experiment. Seed acceptance decreased with increasing seed mass but increased with increasing millipede mass. Seed consumption increased with the size of the offered seed species but was found to be independent of millipede mass. After the millipedes were given dead leaves to consume, the acceptance slightly decreased, and the consumption of the more preferred seed species decreased. Seeds form a small part of the millipede diet but are consumed regularly. Because of millipedes’ foraging preferences and their patchy distribution they may notably contribute to the local mortality of some seed species in their natural environment.     

Influence of a volatile inhibitor in natural or limed soil on fungal spore and seed germination

Seed germination on sterilized moist filter or blotting papers resting on natural soils in stacked “Nalgene” plastic specimen dishes was inhibited particularly in alkaline soils in comparison with controls under similar conditions but without soil. The same response was observed when seeds were suspended on filter or blotting papers above the soils, suggesting the influence of an inhibitory volatile factor. Seed germination was not affected in Good's buffers over the pH range of the soil samples tested indicating that inhibition on filter or blotting papers in contact with soils was not due to the direct effect of pH. The observed inhibition of seed germination is similar to that found in the germination of conidia of common soil fungi; a volatile fungistatic factor was also detected in these soils. Liming of moderately acid soils increased conidial inhibition on indirect soil contact or from volatiles: germination of seeds, however, was not affected by liming in five of six soils tested. These results indicate that seeds of higher plants as well as fungal conidia are affected by some natural soils and volatiles are at least partially responsible for inhibition.     

Seed consumption by millipedes

Seed predation is a key mortality factor for plants that reproduce by seeds. We investigated seed consumption by Cylindroiulus caeruleocinctus (Wood, 1864), an abundant representative of an unrecognised group of seed predators - the millipedes (Diplopoda: Julidae). The consumption of small seed species by millipedes was measured in the absence (41 species) and in the presence (11 species) of alternative food sources (dead leaves). We examined whether millipedes would consume seeds at all and if so whether there were any seed size constraints that determined millipede seed acceptance (i.e., the proportion of millipedes that ate seeds) and seed consumption (i.e., the mass of the seeds eaten). Our results indicated that C. caeruleocinctus readily accepted seeds with 75% of seed species accepted in a no-choice experiment and 100% of seed species in a choice experiment. Seed acceptance decreased with increasing seed mass but increased with increasing millipede mass. Seed consumption increased with the size of the offered seed species but was found to be independent of millipede mass. After the millipedes were given dead leaves to consume, the acceptance slightly decreased, and the consumption of the more preferred seed species decreased. Seeds form a small part of the millipede diet but are consumed regularly. Because of millipedes’ foraging preferences and their patchy distribution they may notably contribute to the local mortality of some seed species in their natural environment.     

Soil salt and NaCl have different effects on seed germination of the halophyte Suaeda salsa

Seed germination is a key life‐history stage of halophytes. Most studies on seed germination of halophytes have focused on the effects of a single salt, while little information is available on the effects of mixed salt in the natural habitat. Due to the contribution of multiple ions in saline soil, we hypothesized that the effect of mixed salt on seed germination will differ from that of a single salt and the mechanism of how germination is affected will differ as well. The effects of mixed salt and NaCl on germination, water imbibition, and ionic concentrations of seeds of Suaeda salsa (L.) Pall. were compared at various salinity levels. Germination percentage (GP) and rate (GR) decreased with increasing salinity level, regardless of salt type. There was no difference in GP or GR between mixed salt and NaCl when the salinity level was below 20 dS m^?1. Above 20 dS m^?1, GP and GR in NaCl were lower than those in mixed salt. At the same salinity level, Na⁺ concentration in seeds was higher in NaCl than that in mixed salt, but the reverse was true for Ca²⁺ and Mg²⁺ concentrations. Imbibition rate for seeds in NaCl was lower than that in mixed salt at the same salinity level. Addition of Ca²⁺ and Mg²⁺ alleviated the inhibition of NaCl on seed germination. In conclusion, our results suggest that the effects of soil salts and NaCl on seed germination are different, and using NaCl instead of soil salt might not be realistic to show the effect of saline stress on seed germination of halophytes in the natural habitat.     

Scheduling Viability Tests for Seeds in Long-Term Storage Based on a Bayesian Multi-Level Model

Genebank managers conduct viability tests on stored seeds so they can replace lots that have viability near a critical threshold, such as 50 or 85?% germination. Currently, these tests are typically scheduled at uniform intervals; testing every 5 years is common. A?manager needs to balance the cost of an additional test against the possibility of losing a seed lot due to late retesting. We developed a data-informed method to schedule viability tests for a collection of 2,833 maize seed lots with 3 to 7 completed viability tests per lot. Given these historical data reporting on seed viability at arbitrary times, we fit a hierarchical Bayesian seed-viability model with random seed lot specific coefficients. The posterior distribution of the predicted time to cross below a critical threshold was estimated for each seed lot. We recommend a predicted quantile as a retest time, chosen to balance the importance of catching quickly decaying lots against the cost of premature tests. The method can be used with any seed-viability model; we focused on two, the Avrami viability curve and a quadratic curve that accounts for seed after-ripening. After fitting both models, we found that the quadratic curve gave more plausible predictions than did the Avrami curve. Also, a receiver operating characteristic (ROC) curve analysis and a follow-up test demonstrated that a 0.05 quantile yields reasonable predictions.     

苦豆子和披针叶黄华种子萌发和幼苗生长对干旱胁迫的响应

以采集于河西走廊中部荒漠边缘的苦豆子(Sophora alopecuroides L.)和披针叶黄华(Thermopsis lanceolate L.)种子为试验材料, 以不同渗透势PEG-6000 溶液模拟干旱条件, 研究了2 种植物种子萌发和幼苗生长对干旱胁迫的响应特征。研究结果显示, 随着干旱胁迫程度的加剧, 2 种植物种子吸胀速率、萌发率、萌发指数、活力指数、苗高、根长和组织饱和含水量等指标均表现出明显降低趋势, 而幼苗干重、根干重和根冠比均呈先升后降趋势。2 种植物种子萌发对干旱胁迫均较为敏感, 苦豆子和披针叶黄华种子能够萌发的最低渗透势阈值分别为-0.65 MPa 和-0.42 MPa。2 种植物因干旱胁迫未能萌发的种子复水后萌发率均较高。分析认为, 2 种植物种子萌发和幼苗生长对干旱胁迫的响应特征对幼苗的成功定植和种群的自然更新具有重要生态学意义, 但在人工栽培时保证土壤墒情应是保障建植成功的关键措施。     

玉米种子人工老化过程中生理特性与种子活力的变化

种子贮藏过程中各项活力逐渐降低,即种子的老化。老化不仅影响种子萌发与幼苗的生长,也会影响到后期植株的产量与品质。以玉米自交系昌7-2、杂交组合郑单958和农大108的F1种子为试验材料,通过人工加速老化的方法,对3个品种(系)的玉米种子人工老化过程中生理特性与种子活力的变化规律进行了分析。结果表明,玉米种子的发芽势、发芽率、发芽指数和活力指数均随老化时间的延长而降低;过氧化物酶(POD)的活性随老化时间的增加而降低,与种子的各项活力指标呈正相关,其中昌7-2与各项活力指标的相关性、郑单958与活力指数的相关性达显著水平;浸出液的相对电导率和丙二醛(MDA)含量随种子的老化时间而升高,与种子的各项活力指标呈负相关,其中昌7-2和农大108的相对电导率、昌7-2的MDA含量与各项活力指标的相关性均达到极显著水平,郑单958的相对电导率与活力指数和MDA含量与各项活力指标的相关性也达到显著水平;玉米种子的发芽率和活力指数随着老化时间的增加呈现一个先缓慢后加快的下降趋势;农大108的抗老化能力较弱,昌7-2和郑单958表现出较强的抗老化能力。     

镉对紫花苜蓿种子萌发与幼苗生长的影响研究

试验研究Cd胁迫对紫花苜蓿种子萌发与幼苗生长的影响结果表明,Cd2 浓度为0~10mg/kg时对种子发芽率的影响不显著,但对发芽势的影响较明显;当浓度达30mg/kg后对发芽的抑制作用表现非常明显,发芽势和发芽率均急剧下降。不同浓度Cd2 对芽和幼根的生长均有明显抑制作用,且对根抑制作用大于芽,同时对活力指数的影响也表现显著;随Cd2 浓度的增加,其抑制作用不断增强,活力指数也随之下降;当浓度达到50mg/kg后幼苗生长几乎完全被抑制。     

Seed nitrogen accelerates the rates of germination,emergence, and establishment of rice plants

We examined the effect of seed nitrogen content on the rates of germination, emergence, and establishment of rice plants. Several seed lots with various nitrogen contents were obtained from the parent plants grown under 3 planting densities and 4 rates of nitrogen application. There was a clear negative correlation between the seed nitrogen content and germination time (R =0.88), whereas the correlation between the seed dry weight and germination time was very low (R=0.23). The seed lot with a high nitrogen content absorbed water faster than the seed lot with a low nitrogen content, especially on the first day after soaking, and also showed a faster emergence, exsertion of the fourth leave, and a more uniform germination. Moreover, the increase of seed nitrogen content as well as the prolongation of soaking time resulted in a uniform emergence. Therefore, seed vigor is likely to be enhanced by the increase of seed nitrogen content, which may be achieved by an adequate application of a large amount of nitrogen to parent plants. Consequently, it may be possible to improve and stabilize the establishment of directly sown rice plants by the sowing of vigorous seeds with a high nitrogen content.     

Fat but slim: Criteria of seed attractiveness for earthworms

Earthworms were shown to significantly affect seeds and seedlings survival via their ingestion and digestion for nutritive purposes. Such selective feeding of earthworms on plant seeds is likely to favour certain plant species and to affect seed bank composition, plant recruitment and plant community structure. Relationships between earthworms and seeds, particularly seed traits that determine attractiveness of seeds for earthworms, are yet to be determined. In this study, the influence of six seed traits was tested on the ingestion, digestion and germination of seeds by two earthworm species (Lumbricus terrestris, anecic and Satchellius mammalis, epigeic). The seed traits tested were their length, width, weight, shape, oil content and the presence of trichomes on their surface. Each earthworm species was introduced into a microcosm with eleven seed species from a chalk grassland that represented those different traits. Ingested, digested and germinated seeds were counted after voiding the guts of the earthworms. Univariate and multivariate analyses showed that seed length, width, weight and seed oil content could significantly affect the ingestion of seeds for both earthworm species. Seed width and seed oil content were the two traits that influenced the digestion of seeds the most, but only for L. terrestris. We also found that seed ingestion was earthworm species-specific but we found no correlation between earthworm traits and number of ingested or digested seeds. Few seeds germinated from L. terrestris casts and no seeds germinated from S. mammalis casts. Implications in terms of plant evolution strategies are further discussed.     

Effect of nitrogen,phosphorus and potassium fertilizer on growth and seed germination of Capsella bursa-pastoris (L.) Medikus

We investigated how plant height, number of stem and branch, seed production and seed germination of Capsella bursa-pastoris were affected by nitrogen (N), phosphorus (P) and potassium (K) fertilizer using a pot fertilizer experiment. Plant growth parameter was determined, and fully ripen seeds were tested for germination. C. bursa-pastoris exhibited great phenotypic variation in plant height, number of stem and branch in relation to N, P and K supply. Seed production per plant was lowest in the control and low P treatment, and highest in NPK treatment. More than 16,000 seeds per plant were produced in treatments where N and P were applied together. A balanced N, P and K supply results in producing a high percentage and fast germinating seeds, while a deficiency of P and K together with a high N supply results in low germination ability and fast germinating of the produced seeds in C. bursa-pastoris.