Seed production and subsequent seed germination of Senecio vulgaris (groundsel) grown alone or in autumn-sown crops

Senecio vulgaris is a common weed of agriculture in the UK, but is also of food value to invertebrates and birds. Thus, it may be beneficial to retain it within agricultural ecosystems to enhance overall biodiversity. A less intensive approach to weed management requires a sound understanding of weed population dynamics so as to avoid unacceptable population growth. Experiments were carried out in 2003 and 2004 to assess seed production, and subsequent germination, by S. vulgaris growing alone, in winter wheat, or in winter field beans. Plant and seed samples were collected during May and June. There was a strong allometric relationship between capsule number and plant weight, irrespective of the year or the presence of crop competition. Numbers of seeds/capsule varied slightly from 51 to 66 seeds per capsule. Plants growing alone were estimated to produce 8471 to 12 887 seeds per plant, whilst those in wheat only 923 to 2156. Germination tests in Petri dishes in incubators showed that virtually all seeds were viable and germinated under daily alternating light:dark conditions within 10 days. Seeds in continuous dark germinated less readily, reaching only 30% after 21 days. On the basis of this and other published work, it would appear that the retention of S. vulgaris in arable fields will not pose a major threat to the long-term viability of crop production.     

Inter-population variabilities in seed mass and germination of Panicum turgidum and Pennisetum divisum in the desert of Kuwait

Understanding variability in seed germination among populations is essential for planning an effective germplasm collection for restoration and conservation purposes.The knowledge of germination and dormancy patterns among populations of desert grasses is crucial for determining the potential of the species and populations to be used for restoration and conservation as well as forage production.Variability in seed germination of Panicum turgidum Forssk and Pennisetum divisum(Gmel.)Henr.in the desert of Kuwait was evaluated in different populations in May 2017.Experiment of seed germination(25 seeds and 4 replicates)was conducted for each population at night/day temperatures of 15℃/20℃and 20℃/30℃under the following light condition:continuous darkness or 12 h/12 h light/dark.Results showed that seed masses of both species strongly varied according to their seed provenances,and both species produced heavier seeds in population with a higher soil electrical conductivity.Seed germination percentage considerably varied between two species,and the variation in P.turgidum was greater(17%–49%)than that of P.divisum(72%–93%).Germination percentage in P.turgidum was greater at high temperature(20℃/30℃)than at low temperature(15℃/20℃).However,temperature regimes had no effect on germination percentage of P.divisum seeds.Mean germination time of both species exhibited significant inter-population variability.This result is especially relevant to assure the selection of the best population of each species and the regeneration success of the species.Besides this,inter-population variability also provides valuable information for enhancing our understanding of the mechanisms that regulate seed germination and how they might be related to seed provenance.     

论我国牧草种子业生产体系中的一些问题

牧草种子业是一个包括种质资源搜集、品种选育、种子生产与推广、种子加工及处理、种子流通和质量监控等一系列内容的产业。通过对牧草种子业中各主要内容组分现状的分析 ,作者认为 :在目前阶段 ,牧草种子生产是牧草种子业中的薄弱环节 ,是限制我国牧草种子业发展的主要因子。在牧草种子生产中 ,由于生产条件、思想认识、市场价格等方面的原因 ,牧草种子生产的相对效益长期以来一直偏低 ,成为制约牧草种子业发展的一个主要因素。要保证牧草种子业的长期、稳定发展 ,提高效益是第一位的。在目前的基础上 ,牧草种子生产的效益要提高一倍才能调动各方面的积极性 ,保证牧草种子各业的健康发展。根据我国的具体情况 ,本文提出了以牧草种子生产为重点 ,以提高牧草种子的产量、质量及生产效益为突破口 ,组织协调好科研、推广、生产和销售各环节 ,靠挖掘现有生产条件潜力、依靠技术进步、理顺市场供求关系等措施 ,推动我国牧草种子业发展的设想。     

Burial rates of surrogate seeds in arable fields

The probability of seed consumption by surface-dwelling predators depends on the duration of seed exposure on the soil surface. We investigated seed burial using painted ceramic beads as surrogate seeds. Fifty beads of three size classes each were applied to small arenas within crop fields and their fates were followed from August to October. New sets of beads were applied as soon as most beads had disappeared from the soil surface. Bead availability on the soil surface declined immediately after placement, and then declined steadily over time, with increased loss during rain and management practices. Smaller beads were incorporated into the soil/litter matrix more easily than larger beads. Bead burial differed considerably among crop environments, with more burial in forage crops (red clover, lucerne) than in row crops (soyabean, maize). The fact that seed availability differed among crop environments suggests that it can be manipulated to maximise predation risk.     

Seed degeneration in potato: the need for an integrated seed health strategy to mitigate the problem in developing countries

Seed potato degeneration, the reduction in yield or quality caused by an accumulation of pathogens and pests in planting material due to successive cycles of vegetative propagation, has been a long‐standing production challenge for potato growers around the world. In developed countries this problem has been overcome by general access to and frequent use of seed, produced by specialized growers, that has been certified to have pathogen and pest incidence below established thresholds, often referred to as certified seed. The success of certified seed in developed countries has concentrated the research and development agenda on the establishment of similar systems in developing countries. Despite these efforts, certified seed has had little penetration into the informal seed systems currently in place in most developing countries. Small‐scale farmers in these countries continue to plant seed tubers acquired through the informal seed system, i.e. produced on‐farm or acquired from neighbours or local markets. Informal seed tubers frequently have poor health status, leading to significant reductions in yield and/or market value. This review emphasizes the need to refocus management efforts in developing countries on improving the health status of seed tubers in the informal system by integrating disease resistance and on‐farm management tools with strategic seed replacement. This ‘integrated seed health strategy’ can also prolong the good health status of plants derived from certified seed, which would otherwise be diminished due to potential rapid infection from neighbouring fields. Knowledge gaps, development challenges and impacts of this integrated seed health strategy are discussed.     

甘肃河西制种区不同成熟期玉米杂交种贮藏期种子活力变化

选择先玉335、郑单958和吉祥1号三个杂交种制种田,于授粉后32 d每隔5 d采收果穗直到授粉后72 d,测定种子电导率、标准发芽率和冷浸发芽率,次年测定田间出苗率以及上述指标,对比分析不同收获期种子在贮藏过程中的变化及其贮藏特性。研究结果表明,随着收获期的推迟,玉米杂交种种子贮藏后标准发芽率和冷浸发芽率降幅减小,电导率的增幅也减小,并且收获后期种子的贮藏性高于前期收获的种子。在授粉后32~47 d、47~62 d、62~72 d采收种子的标准发芽率平均降低6.90%、4.99%、4.48%,前期发芽率的降低速率为中后期的3.75倍;冷浸发芽率依次降低9.70%、13.33%、10.78%,降低幅度明显高于标准发芽率,说明低温冷害后的贮藏性降低。对于不同基因型的玉米杂交种种子,其贮藏后标准发芽率、冷浸发芽率降低程度也不同,先玉335分别降低2%和6.8%,吉祥1号分别降低3.5%和6.9%,郑单958降低3.7%和15%,电导率却依次增大,分别为0.46μs·cm~(-1)·g~(-1)(先玉335)、0.56μs·cm~(-1)·g~(-1)(吉祥1号)、0.49μs·cm~(-1)·g~(-1)(郑单958),说明贮藏10个月后郑单958种子活力衰退幅度最大,贮藏性最差,其次为吉祥1号,先玉335最小,而在活力衰退最小范围内先玉335的适宜收获期为授粉后47~57 d,吉祥1号为授粉后52~57 d,郑单958为授粉后57~62 d,为获得高活力种子提供理论依据。     

西瓜重要种传病害研究进展

本文围绕目前我国西瓜生产中西瓜蔓枯病、细菌性果斑病、黄瓜绿斑驳病毒病等重要的种传病害,阐述了其发生与危害;讨论了国内外在病原物种子传带机制方面的研究进展;分析比较种子健康传统检测技术与现代分子检测技术的优点与局限性;总结现有的种子处理方法,最后提出了尚未明确和亟须研究的问题,为西瓜种传病害的防控提供参考。     

不同干扰条件下荒漠区土壤种子库

在内蒙古阿拉善荒漠区选择开垦、轮牧、过牧和禁牧4种不同干扰条件的样区,于2005年4月(春)、7月(夏)和10月(秋)分别对土壤种子库取样,并在实验室条件下进行发芽试验,得出如下结果:(1)4种不同干扰区在春、夏、秋三个季节土壤种子库可萌发种子平均数量分别为,开垦干扰:688粒/m2;轮牧干扰:1328粒/m2;过牧干扰:1488粒/m2;禁牧干扰:944粒/m2;(2)开垦区与禁牧区在4月份(春)、7月份(夏)、10月份(秋)土壤种子库可萌发种子数量呈连续上升趋势,而轮牧区与过牧区则呈先上升后下降趋势;(3)4种不同干扰条件下,开垦区、过牧区和禁牧区在不同深度土层中水分含量均无显著差异;而轮牧区0-5cm与其它三个土层中水分含量出现显著差异,而且0-5cm土壤层的水分含量与种子的萌发数量呈显著正相关。     

苦豆子种子特性与种群扩展关系的研究

苦豆子(Sophora alopecuroides L.)种子体积大,千粒重达21.6g。种皮较厚,制约了种子的萌发,采用浓硫酸浸种和机械磨损破坏种皮明显提高了萌发率。种子散布主要依靠自身重力,其散布格局是聚集型散布,多分布在母株周围,为该区域的种子库提供较多的种质资源。此外,还有动物散布和水力作用的散布,使种子能传播较远的距离,同时种子被采食后,通过消化道的磨损使种皮的通透性提高,促进了种子的萌发。     

大豆疫病的种子处理技术研究

本试验用不同浓度的瑞毒锰锌、杀毒矾和克露进行大豆种子处理试验，结果表明，５００ｐｐｍ瑞毒锰锌对大豆疫病具有很好的治疗作用，而用杀毒矾以种子重量０．４—０．５％的剂量闷种，能显著地抑制大豆疫霉菌的侵入     

Influence of hairy vetch seed germination and maturation on weediness in subsequent crops

Hairy vetch is a widely adopted cover crop in the United States. However, hairy vetch can become weedy in subsequent crops as seeds germinate after the cover crop growing season, which is largely attributed to seed dormancy. We conducted two field experiments to determine seed germination, viability and seed production phenology of two common hairy vetch cultivars in Blacksburg and Blackstone, Virginia, US. ‘Groff’ and ‘Purple Bounty’ seed were sown in October 2015 and May 2016 and germination was tracked until June 2017. Subsequently, ungerminated seeds were tested for viability. Both cultivars had <2% germination after the initial germination period, and <1% of seed recovered was still viable at the end of the experiments. We also conducted experiments to determine when these cultivars produce viable seed. Hairy vetch seeds were counted and tested for germination in the spring. Both cultivars produced seed beginning in late‐May, but most seed were not viable until mid‐June in Virginia. Our results indicate that seed dormancy is not the primary cause of hairy vetch weediness in subsequent crops as nearly all germination, 99% of the total germinated seed, occurred during the cover crop growing season. Also, if complete termination occurs before mid‐June in Virginia, it is unlikely viable seed will be added to the seed bank. To better utilise this cover crop species, cultivar selection and proper termination are important to prevent weediness.     

Germination ecology, emergence and host detection in Cuscuta campestris

Trials were carried out to study the germination and dormancy of Cuscuta campestris Y. (dodder) seeds and factors influencing the success of early parasitisation of sugarbeet. Primary dormancy can be removed by seed scarification. Germination was negligible at 10°C and optimal at 30°C, while it was not influenced by light. Seed burial induced a cycle of induction and breaking of secondary dormancy. Seedling emergence was inversely proportional to the depth of seed burial and only seed buried within 5 cm of the soil surface emerged. Storage of C. campestris seeds in a laboratory for 12 years resulted in the loss of primary dormancy, enabling the germination of all viable seeds. Host infection (i.e. protrusion of parasite haustoria from host tissue) was heavily influenced by host growth stage. Tropism towards a host was due to the perception of light transmitted by green parts of sugarbeet plants. Insertion of a transparent glass sheet between host leaves and parasite seedlings did not modify this response. This phototropism permitted Cuscuta to identify host plants with high chlorophyll content as a function of the lower red/far red ratio of transmitted light.     

Potential for endozoochorous seed dispersal by sheep and goats: Risk of weed seed transport via animal faeces

Endozoochory is known as an important mechanism for the spread of weeds. We carried out experiments to assess the fate of seeds of several weed species (Convolvulus arvensis, Cuscuta campestris, Rumex crispus, Hordeum spontaneum and Sorghum halepense) after passing through the gut of sheep and goat. Eighteen animals of both sheep and goat received diet mixed with seeds of the weed species or control with only wheat bran (five weed species + control × three replications). Results showed that a higher proportion of seeds were missing after passage through the sheep gut than in goats. In goats, a greater proportion of seeds were dead after passage, but the number of seeds collected from dung was also greater. Weed species differed, with the highest seed recovery and viability in Cuscuta campestris. Based on time of seed passages through the animal gut estimated for the different weed species, we recommend that sheep should be kept in a corral for 96 hr to minimise seed transportation via their faeces. For goats, if R. crispus and C. arvensis seeds could be excluded from the diet, then maintaining them for 96 hr in an animal stall would ensure little seed transportation via dung, but we found R. crispus and C. arvensis seeds to be present and viable in goat dung even 120 hr after feeding. Very large numbers of viable seeds can be found in goat and sheep dung, so the use of rotted manure is highly recommended to avoid transportation of viable seeds via manure fertilisers.     

Assessment of the abrasion potential of pesticide-treated seeds using the Heubach test

During sowing of pesticide-treated seeds, pesticide-laden dust and abraded seed particles may be emitted to the environment, possibly leading to environmental contamination and posing health risks. In many countries there is currently no legislation concerning the acceptable amount of dust of treated seeds. This study aimed to gain insight in the abrasion potential of available pesticide-treated seeds and its associated factors. The abrasion potential of 45 seed samples of 7 different species (viz. sugar beet, oat, barley, wheat, spelt, pea, and maize) was determined using the Heubach test and amounts of dust were expressed as g 100 kg_seeds^?1, g 100,000 seeds^?1, and g ha^?1. The abrasion potential fell generally within the boundaries of maximum permissible values adopted by different countries. Species, seed treatment company, number of active ingredient (AIs) and combination of AIs had significant effects on the abrasion potential, whereas little or no effect of agitation and conservation was found. However, species were situated differently with respect to each other depending on the unit in which the abrasion potential was expressed. A standard unit that takes into account the species’ seed rate is suggested to give the fairest assessment of dust drift risk and would allow international comparison.     

Effects of individual plant phenology on dormancy of Rumex obtusifolius seeds at dispersal

In 1998–2000, the relationship was investigated between the time of bolting of shoots and the percentage of germinability in seeds from individual plants of Rumex obtusifolius . Each year, the date of bolting of shoots was recorded in 30–108 plants, which were then grown intact until maturation, and their seeds were collected before dispersal. The proportion of germinable seeds increased with the date on which the shoots bolted. The timing of shoot bolting and seed germinability for individual plants persisted over the years of observation. To discriminate between the effect of mother plant and timing of seed maturation, shoot bolting of another 40 (1998) and 50 (1999) plants was recorded, and their shoots were then cut in late June The shoots of cut plants regrew and matured nearly simultaneously, later than in intact plants, whereas overall seed germinability decreased. In individual plants, the seed germinability was still significantly correlated with the date when plants originally bolted.     

毛乌素沙地天然臭柏群落种子产量、种子库及幼苗更新

采用样方调查法,研究了毛乌素沙地臭柏(Sabinavulgaris)群落的种子产量、种子库及幼苗更新。结果表明:毛乌素沙地天然臭柏群落的球果丰富,约为3093. 83粒/m2,种子产量为9118. 5粒/m2,优良种子达2954. 4粒/m2。5种立地条件间的土壤种子库差异大、质量低,种子优良度最高的也仅为3. 7%。土壤种子集中分布于0 ~5cm土层内,并随着土壤深度增加,优良种子数由0~5cm的30. 52粒/m2减少到5~10cm的1. 3粒/m2。5 种立地中当年幼苗数的平均值仅为7. 98株/m2,最高的(A类立地)为14. 7株/m2,仅占表土优良种的30%左右,最低的(D类立地)已经丧失了更新能力。臭柏群落内种子更新苗少,而且种子更新集中在少数滩地小生境中。种子库小、质量差、更新环境的丧失是限制臭柏群落天然更新与拓展的主要因子。     

Weed seed movement and dispersal strategies in the agricultural environment

This paper reviews the current knowledge on weed seed movement in an agricultural environment. Seed movement is analyzed both from an agronomic and ecological perspective, focusing predominantly on horizontal seed movement. Abiotic (anemochory and hydrochory), as well as biotic (autochory, myrmecochory, epizoochory, and endozoochory) weed seed dispersal typologies are examined, highlighting the mechanisms involved, the specializations displayed by weed species that have evolved by exploiting a particular dispersal mechanism, and their adaptive interaction with the surrounding ecosystem. Emphasis is also placed on the crucial role of human activity (anthropochory), which can affect natural (biotic and abiotic) weed seed dispersal at several stages, partly via the worldwide commercial seed trade but, above all, by crop management operations, thereby potentially facilitating the entry and spread of alien weed species. This phenomenon, together with the invasive expansion of existing weeds that more successfully coevolve and adapt to the new environment, might exert an adverse effect on biodiversity. In-depth knowledge of weed seed dispersal, survival, and germination mechanisms is therefore essential for effective and eco-compatible management of the weed phytocoenoses present in the agroecosystem in order to promote a rational trade-off between agricultural productivity and environmental protection.     

Ecological aspects of seed dormancy-break and germination in Heteranthera limosa (Pontederiaceae), a summer annual weed of rice fields

Summary Heteranthera limosa seeds were buried in flooded and in non-flooded soil and exposed to natural seasonal temperature changes in Lexington, Kentucky, USA. Seeds exhumed after various periods of burial ranging from 2 to 36 months were tested for germination under both flooded and non-flooded conditions. Seeds were dormant at maturity in September and became non-dormant during winter. Seeds buried in non-flooded soil during winter germinated to higher percentages and over a wider range of temperatures when tested under flooded conditions (in light) during spring and summer, than did those buried in flooded soil during winter. Thus, the water regime associated with rice culture (non-flooded in winter and flooded in summer) is optimal for dormancy-break and germination of H. limosa seeds. A portion of the buried seeds exhibited an annual dormancy/non-dormancy cycle, whereas others had a conditional dormancy/non-dormancy cycle. Regardless of the type of cycle, seeds buried in non-flooded soil retained the ability to germinate in light at high temperatures under flooded conditions throughout the summer. Thus, seeds potentially can germinate at any time during the growing season, whenever rice fields are flooded. Flooding fields during winter and/or sowing rice relatively early in the growing season may help in establishing rice before seeds of H. limosa germinate.