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.     

Viability of Oryza sativa L. seeds stored under genebank conditions for up to 30 years

Germination ability, equilibrium relative humidity (eRH), and moisture content of ‘control’ seed samples representing 183 rice accessions stored in the active (2–4 °C) and base (?10 °C until 1993, then ?20 °C) collections of the T. T. Chang Genetic Resources Center were determined after storage for 20.5–30.5 years. Germination of seeds that had been stored in the base collection was generally high (>70 %), whereas germination was more variable for seeds stored in the active collection. Samples with lower viability after storage in the active collection were likely to have lower viability after storage in the base collection. There were significant differences in the moisture content-eRH relationship of the seeds depending on whether the seeds had been stored in the active or base collection. Based on re-test data for regular seed samples regenerated in 1979–1980 and stored in the active collection for up to 31 years, estimates of the time for ability to germinate to fall to 50 % (p ₅₀) ranged from 54 to 997 years. For the same seed samples stored in the base collection for approximately 31 years, ability to germinate has been maintained and germination increased due to improved procedures. The ability to germinate of base collection samples was also generally higher than that of ‘safety duplicate’ samples of the same seed lots that had been sent to the National Center for Genetic Resources Preservation, USA in 1981 and stored at ?18 °C. This may have been due to uptake of moisture either during processing for dispatch or as a consequence of poor packaging material. The results are discussed in relation to long-term seed storage and genebank management.     

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.     

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.     

Vermicompost Leachate as a Promising Agent for Priming and Rejuvenation of Salt-Treated Germinating Seeds in Brassica Napus

Salinity is a major constraint hampering germination and early seedling growth, especially in aged seed lots. Any rejuvenation treatment improving salt resistance at these crucial developmental stages will be of special interest. Two sets of experiments were performed in Brassica napus to precise the impact of vermicompost leachate (VCL) on seed germination in the presence of NaCl and to analyze its putative interest as seed priming agent before NaCl exposure. Two seed lots were used: one old seed lot (cv. Libomir) and a recent one (cv. Harry). VCL increased the germination percentage of aged seeds in the absence of NaCl and increased seedling length in both cultivars. VCL had only a minor impact when directly added to the NaCl-containing germinating solution. In contrast, priming with VCL strongly improved subsequent germination in the presence of NaCl in relation to a more efficient management of oxidative stress in both cultivars. The improvement of salinity resistance provided by VCL priming was not due to modification in ion or proline content. It is concluded that VCL may act as a rejuvenation agent invigoring old seed lots and as an efficient priming agent for improvement of salinity resistance at the germination stage. Valuable properties of VCL are discussed in relation to the simultaneous presence of several protecting compounds.     

Patterns of SSR variation in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) seeds under ex situ genebank storage and accelerated ageing

Maintaining seed viability and germplasm integrity is a challenging task in conservation of plant genetic resources, as seeds under storage will lose viability and genetic changes will occur. Attempt was made to analyze the patterns of genetic changes in wheat germplasm under ex situ genebank storage and accelerated ageing treatments. A set of 16 naturally aged wheat accessions under ex situ genebank storage since 1994 were sampled. Four recently regenerated wheat accessions were selected, four random seed samples were chosen from each accession, and three of them were exposed to three different accelerated ageing treatments. These 32 seed samples in two germplasm sets displayed a range of germination rates from 4 to 98 %. Thirty-seven microsatellite markers representing 21 wheat chromosomes were applied to screen 12 seeds of each sample and 449 SSR alleles were scored. Large SSR variation was found in each germplasm set. There was 73.1 % of the total SSR variation present among the naturally aged samples and 78.2 % present among the accelerated ageing samples. Several analyses for genetic association consistently revealed no clear genetic separations among samples of high or low germination rates in both germplasm sets. Samples under different accelerated ageing treatments did not show much genetic differentiations from the original sample of each accession. Mantel tests revealed non-significant associations between SSR variability and sample germination rates for both germplasm sets. These findings are useful for understanding seed deterioration under different ageing conditions and suggest that genome-wide SSR variability may not provide sensitive markers for the monitoring of wheat seed viability.     

水土保持边坡固化植草技术研究

通过建立4种形式的边坡植草护坡处理试验小区,并对每种处理各设2组重复试验小区,对边坡防护效果及草籽出芽生长情况进行对比试验。研究结果表明,结合土壤固化剂和撒播草籽进行边坡表土处理后,草籽能够正常萌芽及生长,而且边坡表土层的抗冲刷能力明显增强,坡面侵蚀细沟显著减少。实践证明,边坡固化植草是一种行之有效的护坡绿化技术方法。     

Seed longevity in terrestrial orchids - Potential for persistent in situ seed banks

Terrestrial orchids typically produce numerous small seeds that contain very small nutrient reserves. The seeds are structurally adapted for wind dispersal but little is known about their fate after dispersal. Some studies of seed viability in situ indicate survival for up to two years in temperate orchid species. Seeds stored in the laboratory may last much longer. We investigated seed viability of seven North American orchid species with seed packets buried in a range of soil and wood substrates within their natural habitats. In Goodyera pubescens most seeds germinated within one year. Four other species continued to germinate sparsely during the observation period, but after almost seven years many seeds were still viable. In one species, Liparis liliifolia, seeds that had been in situ for four years had germination rates as high as 68% when sown in vitro with a compatible fungus. The remaining two species did not germinate during the observation period but the seeds were judged to be intact and tested positively for viability after four years in the ground. These observations are interpreted as different species-specific strategies for in situ germination and their seed bank potential is discussed.     

Effects of accelerated ageing on germination and biochemistry of eight rice cultivars

Rice seed deterioration rate due to aging is correlated with ambient temperature, relative humidity, and moisture. Eight cultivars were analyzed for differences in seed deterioration via accelerated ageing at 45°C and 100% relative humidity (RH) for 24, 48, 72, 96, 120 hr. Khazar and Neda had highest germination percentages when exposed to 120 hr seed ageing. For Lenjan, with increased seed ageing, moisture content increased from 9.8% in the control to 21.7% after the 120 hr treatment. Khazar and Shiroudi had the lowest decrease in shoot length. Root length decreased from 0 hr control to 120 hr treatment, and was lowest in Fajr and Khazar. Minimum electrical conductivity was observed in Neda and Fajr after 120 hr. Lowest increases in lipid peroxidation from control to 120 hr treatment was in Fajr, Khazar, and Neda. Neda and Khazar are the most suitable cultivars to store in the humid, sub-tropics of northern Iran.     

Intercluster correlations for binomial data: An application to Seed Testing

Certification of crop seeds from a seed lot requires determination of the seed germination rate through tests governed by the International Seed Testing Association (ISTA) and the Association of Official Seed Analysts (AOSA). The results from four tests of 100 seeds each are compared with published tolerances to determine whether seed lots concur with a labeled germination rate. Examination of results from numerous corn and soybean seed lots sent to more than 30 member laboratories of the AOSA and the Society of Commercial Seed Technologists (SCST) suggested that, in aggregate, counts reported by the laboratories frequently show less sample variability than expected under independentbinomial sampling due to positive correlation among the individual test results. Whereas much of the recent literature on correlated binomial data is concerned with efficient methods for estimating the binomial success probabilities, comparatively little attention is paid to the problem of diagnosing whether correlations exist and are significant. Considering the replicate tests as clusters, we propose an estimator for the intercluster (interreplicate count) correlation coefficient and examine its statistical properties. Results from applying the estimator in unblinded and blinded seed tests are presented. The results are revealing; the estimates tend to be larger and significant in the unblinded seed tests.     

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.     

Light and Temperature Requirements during Germination of Potential Perennial Grasses for Rehabilitation of Degraded Sandy Arabian Deserts

Few plants can tolerate the loose sandy‐soils of the arid deserts. Selection of native plants that could be used in rehabilitation of degraded deserts necessitates information about their seed dormancy and germination requirements. This study assessed the effects of light and temperature requirements during germination for eight common perennial grasses that have the potential to rehabilitate the arid Arabian deserts. The selected grasses vary considerably in seed mass. Germination of clonally propagated grasses (six species) was significantly greater, but slower, than that of two non‐clonal grasses. Four of these six species (Lasiurus scindicus , Panicum turgidum , Aeluropus lagopoides and Halopyrum mucronatum ) produce larger seeds and attained greater germination in both light and darkness at a wide range of temperatures. However, the other two (Centropodia forsskaolii and Coelachyrum piercei ) produce medium‐sized seeds with higher dormancy. Smaller seeds of Sporobolus arabicus were positively photoblastic at all temperatures, but those of Sporobolus spicatus were neutrally photoblastic at lower temperatures and positively photoblastic at higher temperatures. There was a significant negative relationship between seed mass and relative light germination, indicating that small seeds require more light during germination. It is recommended to use seeds of the six clonal grasses for restoration of degraded arid deserts. The ability of these grasses to germinate in different light and temperature regimes indicates their ability to germinate at any time of the year, even when seeds are buried. The light and temperature requirements of the different grasses are explained in the light of their adaptation and distribution in natural habitats. Copyright © 2017 John Wiley & Sons, Ltd.     

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.     

Germination of 151-year old <Emphasis Type="Italic">Acacia</Emphasis> spp. seeds

A collection of seeds from five Acacia species was made in Egypt in 1856. Since then, the seeds have been stored at room temperature in different Swedish museums. Due to the extreme longevity within the seeds of Acacia and related species, germination tests were performed on the now 151-year old seed. Seeds of two of the five species tested germinated. The first, Acacia farnesiana (L.) Willd., had two seeds germinate, and Acacia melanoxylon R. Br. ex Ait. f. had one seed germinate. In addition, DNA was extracted from the aged seed and DNA preservation was analyzed. Four of the tested species displayed well preserved DNA, whereas DNA from Albizia lebbeck (L.) Benth. showed signs of degradation. The 151-year longevity of the Acacia seeds is among the longest of dry-stored seeds reported. Several independent studies now report on extreme survival capacity for Acacia and related genera suggesting that these genera are suitable for studies on the characteristics of seeds with long storage performance. The results also demonstrate that herbaria and seed collections stored in museums and institutional depositories can be alternate sources of plants genetic material and should be given conservation attention.     

重金属和pH值对类芦种子萌发的影响

类芦(Neyraudia reynaudiana)是一种具有极强耐干旱、贫瘠、高温等逆境的多年生禾草植物,是南方水蚀荒漠化地区、采矿采石厂及各类边坡植被自然恢复中的先锋植物。为探索在各类矿区及受重金属污染的地区采用类芦进行生态修复的可行性,通过室内发芽试验,对类芦种子在Hg2+,Cr6+,Cd2+,Pb2+,Zn2+,Cu2+等6种重金属离子胁迫及不同pH值条件下的萌发能力进行了研究。结果表明,类芦种子在pH值为5.0~9.0的范围内具有良好的萌发能力;6种重金属离子随着处理浓度的升高,对类芦种子的抑制作用逐渐加强,且出现显著抑制作用的最低浓度顺序为:Cd2+Cu2+Hg2+,Zn2+,Cr6+Pb2+;6种重金属对类芦种子活力指数出现显著影响的浓度均较显著影响发芽率、发芽势和发芽指数3个指标的浓度低,说明类芦幼苗生长比种子萌发对6种重金属更加敏感。     

北京山区不同质地类型自然边坡土壤种子库特征

为了解北京山区土质边坡和土石边坡土壤种子库特征,在北京市鹫峰、百花山和云蒙山采用野外调查和室内萌发试验相结合的办法,研究这3个区域中土质边坡和土石边坡土壤种子库大小、物种组成及其与地上植被之间的关系。各个研究区的土壤种子库共包含54种植物,隶属于26科53属,其中有30种灌木,23种草本,1种蕨类,未观察到乔木种;土壤种子库密度介于(16 166.67±2 165.16)~(20 612.50±2 717.32)粒/m~2;各个试验地0—5cm土壤层与5—10cm土壤层种子库的种子数量垂直分布有一致的规律性,0—5cm土壤层种子库密度略高于5—10cm土壤层;土壤种子库与相应样地地上植被之间相似性指数介于0.390~0.492。通过研究发现,所选地区土壤种子库中包含大量植物种子,在合适的环境条件下,可以顺利萌发,能够满足一般情况下的生态修复要求,可以考虑作为客土在北京山区的环境修复中发挥作用。     

The Effect of Temperature on the Viability Of Weed Seeds in Compost

In this study, the effect of different constant temperatures on the viability of weed seed contaminants of municipal composted waste was determined. Seeds of eight weed species were buried in moist compost in small recoverable packets. The seeds were subjected to three constant temperatures, typical of the composting process, removed after 3, 21 and 84 days and their germination and viability determined. At 55°C all of the recovered weed seeds failed to germinate and were found to be non-viable. At 35°C and 45°C an effect of incubation period was noticeable, and it was evident that there were significant differences between species in tolerance to temperature. The study showed that three days at 55°C was sufficient to destroy all the selected weed species. It was concluded that, among the species studied, seeds that survive the composting process do so as a result of localized “cool spots” caused by inefficient turning of the windrow. Alternatively wind blown species could be entering the outer parts of the windrow, immediately prior to packaging.     

小麦与油菜种子萌发对酸雨胁迫的反应研究

用pH2.0、2.5、3.0、3.5、4.0、5.0模拟酸雨处理小麦和油菜种子试验结果表明,pH2.0时小麦和油菜种子不发芽,pH2.5时只有小麦异状发芽,pH≥3.0时小麦和油菜种子发芽率、发芽势、发芽指数、活力指数均与pH值显著正相关,小麦异状发芽率则随pH值上升而降低。小麦和油菜的吸水值、呼吸速率、贮藏物质运转效率也与pH值显著正相关,小麦贮藏物质消耗率与pH值显著正相关,而油菜与pH值显著负相关;小麦和油菜的根、芽长抑制指数均与pH值显著负相关,且小麦抗酸雨胁迫能力强于油菜。     

GGR6浸种处理浓度对沙打旺种子活力及萌发特性的影响

利用植物生长调节剂调节植物生长、发育和繁殖,是有效提高植物对逆境适应能力和生产能力的重要手段.为探究植物生长调节剂GGR6对沙打旺种子活力及萌发特性的影响,通过观测不同GGR6浓度(0、50、100、150和200 mg/L)浸种处理下,沙打旺种子活力及萌发特性指标,利用隶属函数法,综合分析筛选出适宜沙打旺种子萌发的GGR6处理浓度.结果表明:1)种子发芽动态呈“单峰型”,GGR6处理提高了种子发芽速度和发芽率,缩短发芽时间;2)处理浓度为100 mg/L以下时,种子活力、发芽势、发芽率、发芽指数、萌发指数和活力指数均随着GGR6浓度升高而升高,且浓度在50 ～ 100 mg/L之间,升高最为显著,高于100 mg/L后,各处理之间差异不显著(P＞0.05);3)促进沙打旺种子萌发的最佳GGR6作用浓度为100 mg/L.研究对利用植物措施在荒漠化土地治理中,加速植被建设的进程和效果具有重要意义.     

Variability Among Maize (Zea mays L.) Inbred Lines for Seed Longevity

Genotypes conserved in active collections may suffer genetic erosion and modifications. The objective of this work was to investigate changes in germination and vigour in maize (Zea mays L.) inbred lines during cold storage in an active collection. Seeds of 16 maize inbreds produced along 16 years were evaluated for emergence and seedling vigour in a growth chamber. Linear and quadratic regressions of vigour and viability-related traits over seed age were calculated and tested for homogeneity. The seed of five production years of five inbreds that behaved differently in the regression analysis was multiplied in 1998, and original and renewed seed were evaluated in a growth chamber in 1999. Viability and vigour decreased linearly with age for most inbreds, particularly for B84 and EP10, varied at random for a few inbreds, and remained high for EP56 and A295. Aging caused reduction of vigour and loss of viability in most inbreds. There was variability for seed longevity among inbred lines; longevity was highest for inbred EP56. During storage, some seeds of each inbred died, while enduring seeds, when multiplied, produced new seed with enhanced viability and vigour compared to the average seed of the inbred, suggesting natural selection for viability and vigour during storage within inbred lines.