小麦种质贮藏过程中生活力丧失特性及田间出苗率表现

通过对贮藏2～20年的378份中期库小麦种质进行生活力测定(每一贮藏年份测定种质份数为10～30),结果表明贮藏年限为2～12年的种质平均发芽率都高于83％,而贮藏年限为15年的种质平均发芽率已降至20％,这表明小麦种质在中期库贮藏过程中,生活力丧失存在着骤降特性。同时对同一品种分别来自中期库低活力和长期库高活力种质进行田间出苗率和农艺性状调查,发现中期库种质的室内发芽率与田间出苗率相关极显,其相关显性高于长期库种质,且不论是来自中期库低活力种质还是长期库高活力种质,总体上田间出苗率都比室内发芽率低20％以上,在子一代种子的农艺性状上两之间无显差异。     

国家库贮藏20年以上种子生活力与田间出苗率监测

对34种作物1.4万多份的国家库贮存种子进行了生活力监测,结果表明,贮存20年后,92.9%被监测种子的发芽率仍保持在85%以上,但有155份种子（占被监测份数的1.1%）出现了明显的下降（发芽率从80%以上降至70%以下）。发芽率显著下降的作物包括蚕豆、红小豆、黄麻、蓖麻、甜菜、西瓜、烟草、牧草。小麦等8种作物2078份种子的田间出苗率调查表明,所有种质均有出苗,但有8份种质的出苗率低于10%。出苗率与入库初始平均发芽率存在差别,平均出苗率最高的作物为普通菜豆86.2%,比该批入库初始发芽率平均值低9.3%;平均出苗率最低作物为谷子39.2%,比该批种子的入库初始发芽率平均值低51.3%。总体而言,国家库内保存的作物种子中,多数可安全保存20年以上,尤其是水稻等禾谷类作物种子,但对于蚕豆、红小豆等平均监测发芽率出现显著下降的作物种子需要增加监测频率,以确保种子的长期安全保存。     

种子老化诱导小麦染色体畸变及大麦醇溶蛋白带型频率变化的研究

通过时20份小麦种质发芽率和根尖细胞染色体畸变的测定,结果表明同一品种贮藏于中期库的低发芽率种质,其染色体畸变率明显高于贮藏于长期库的高发芽率种质.从总体上看,种子根尖细胞染色体畸变率与发芽率呈负显著相关,而与贮藏年限无显著相关.但对长期库和中期库的种质分别进行统计分析,种子根尖染色体畸变率与发芽率和贮藏年限均无显著相关.对大麦地方品种"普乃干木"的醇溶蛋白分析表明,该品种有4种biotype,随着发芽率的下降,其群体中的4种bio-type的频率发生了变化,当发芽率从95%降到34%时,其中一种biotype出现了消失,而有一种biotype频率从83%上升至95%,此结果表明,种子生活力下降和不同biotype种子存活能力存在差异,可能导致了异质种质材料遗传选择和漂变的发生.     

低温库种质安全保存理论的研究进展

20世纪70年代以来,低温库种质安全保存理论研究有了较大进展。本综述在延长种子贮藏寿命、种质贮藏过程中的生活力丧失和遗传变化、以及种质发芽率更新标准等方面的研究进展。并强调指出,加强上述基础理论研究,对确保低温库种质安全保存尤为迫切且意义重大。     

α-淀粉酶和超氧化物歧化酶等位酶与水稻种子超干燥保存遗传完整性的研究

不同含水量的水稻种子在0℃和室温中保存40个月后,经发芽检测和а-淀粉酶、超氧化物歧化酶等位酶分析,结果表明,种子含水量降至3.0%以下,种子的耐贮性下降,发芽率降至61%以下,种子的遗传完整性受到影响。а-淀粉酶等位酶技术适合用于检测水稻种子超干燥保存的遗传完整性。     

无菌马尾松种子超低温保存技术研究

该研究利用液氮将不同含水量的无菌马尾松种子(27.4%、24.6%、22.7%、16.8%、15.8%、10.7%、7.5%、6.1%、4.8%、3.2%)进行超低温保存。结果表明:(1)在3.2%～6.1%含水量范围内,经液氮冷冻保存后的发芽率随着含水量升高而逐渐升高,在含水量6.1%时,发芽率达到最大值(91.33%);当含水量大于6.1%时,发芽率逐渐下降,尤其是当含水量大于15.8%时,发芽率迅速下降;在3.2%～7.5%含水量范围内冻存后发芽率在80%以上。(2)冷冻、化冻方式影响超低温保存效果。种子无需低温预冷,直接投入液氮保存(快速冷冻)效果最好;室温空气化冻(缓慢化冻)较42℃水浴化冻发芽率高,且后者容易发生种皮炸裂现象。(3)种皮对马尾松种子超低温保存过程起到保护作用,使其免受机械损伤,去掉外种皮的种子冻存后发芽率显著下降,且容易出现形态不正常的幼苗。(4)超低温保存对马尾松种子萌发具有一定"刺激"作用,在最适含水量6.1%时,经超低温保存后种子的发芽率显著大于对照种子。总之,含水量、冷冻方法、化冻方法、种皮结构显著影响超低温保存效果,马尾松种子超低温保存的最优方法是将种子含水量控制在6.1%,直接投入液氮快速冷冻后室温空气缓慢化冻,冻后发芽率可在90%以上。马尾松种子超低温保存技术体系的建立,为其种质资源的长期保存提供了技术支持。     

一个预测贮藏在低温种质库的小麦种子寿命的方程

为探讨将种子发芽率转化为存活比,促使种子存活曲线转变成直线,并用于预测种子寿命的可行性,3个含水量水平的3种8个种子批的小麦种子被贮藏在20℃、30℃和40℃的温度下长达810d,以获取发芽率数据。比较和分析了概率、存活比与贮藏时间绘制的种子存活曲线、构建的概率回归和存活比线性回归方程的拟合性比,以及贮藏温度和种子含水量对种子死亡时间分布标准差的影响。结果表明,和概率值相比,存活比更容易使种子存活曲线直线化,和贮藏时间的线性回归方程的拟合性也更优于概率回归方程;贮藏温度和种子含水量的交互作用对种子寿命的影响是真实的,其作用也大于单独的温度、水分或水分的对数;只包含贮藏温度和种子含水量交互作用的预测种子寿命的存活比线性回归方程,即Gi/G0=A-P/10KE-CWH(t譵),被贮藏在低温种质库的小麦种子的实际发芽率和贮藏时间证明,是适合用于预测贮藏在低温种质库的小麦种子寿命的,尤其在预测发芽率时较预测贮藏时间有更高的准确性。     

低温贮藏下真空与非真空包装对小麦种子生活力的影响

对以铝箔袋真空包装和铝盒非真空包装的89份小麦种子,在-4～0℃的低温种质库中贮藏11年后的贮藏效果进行了研究.从种子贮藏后的发芽率与入库前的初始发芽率差异,2种包装方式的种子年份间、同一年份2种方式间的种子发芽率差异等3个方面探讨了2种包装方式的种子在低温贮藏条件下的贮藏效果.结果表明:通过低温贮藏11年的小麦种子生活力测定.82%的材料在低温保存后其种子平均发芽率高于初始发芽率.而贮藏第10年后发芽率才出现较初始发芽率明显下降;铝箔袋包装的种子发芽率下降幅度小于铝盒包装,且差异达显著水平;铝箔袋真空密封包装的贮藏效果明显好于非真空包装的种子.     

国家棉花种质中期库(安阳)

<正>国家棉花种质中期库依托于中国农业科学院棉花研究所,1979年始建,目前所用种质库为2001年重建,2002年投入使用,库房面积50m~2,库容1万份,2011年6月又建成一座集干燥、冷藏于一体的现代化种质库,库房面积300m~2,库容4万-5万份,2012年开始投入使用。中期库库温为0℃±2℃,相对湿度50%±7%,种子可安全保存15年。目前棉花种质资源中期库有专职研究人员8人,其中研究员1人、副研2人。国家棉花中期库根据国家整体需求,负责收集国内外棉花种质资源、经整理、鉴定评价、繁殖更新、入库保存和向全国棉花育种、生产等单位分发利用。截至2013年11月,国家棉花种质中期库共保存来自世界53个产棉国棉花种质资源9682份,其中陆地棉8282份、海岛棉836份、亚洲棉546份、草棉19份。近5年发放种质12634份次。     

阿根廷作物种质资源考察报告

阿根廷是南美洲第二大国家,是世界重要的粮食生产大国之一。主要种植作物有大豆、玉米、小麦、水稻、向日葵、花生、棉花等。阿根廷作物种质资源统一由阿根廷国家农业技术研究院（INTA）进行管理,全国生物资源设有首席项目协调员, 统一管理和协调全国的生物资源收集、保存、评价鉴定、研究与交换等项目工作。下设动物资源协调员、植物资源协调员和微生物资源协调员。阿根廷有作物种质资源保存长期库1个,中期库9个,收集品库8个。长期库设在INTA生物资源所,中期库和收集品库分别设在INTA所属的全国各地的研究所和试验站。保存有玉米、牧草、向日葵、花生、高粱等29040份作物种质资源。     

小麦种子在不同保存条件下的生活力丧失特性研究

近年来种子在低温种质库和室温保存条件下的生活力丧失特性研究日益受到关注,但是与其重要性相比,目前很少见有文献报道此方面进展。本文中我们监测了在中期库、室温和人工加速老化条件下小麦种子的生活力变化,以了解种子在这些保存条件下的生活力变化特性。结果表明,三种条件下所有种子的存活曲线均呈反S形,这种特点不受保存条件的影响。随着保存温度的降低,种子生活力丧失速度降低,反S形曲线的平台期和种子寿命延长。我们采用T检验来判断平台期和种子生活力快速下降期之间的转折点（Pt）,发现小麦种子在不同条件下保存时,其Pt均十分接近,在82.2%到83.6%之间。本文讨论了将Pt以及其他生理指标作为种子保存过程中生活力快速下降的预警指标的可能性。     

繁殖世代对水稻植株农艺性状及稻米品质的影响研究

以国家长期库躬存种质为对照,选择在生产上一直种植的同一品种为高繁殖世代材料,一起进行田间种植以了解两者之间在田间出苗率、生育期、植株农艺性状及稻米品质上是否存在差异。结果表明,在6个供试粳稻品种中,有5个品种的高繁殖世代种质,其稻米垩白品质出现了退化现象,而其他稻米品质特性没有出现明显的变化。来自库存的种质,其每穗粒数都比一直在生产上种植的种质少,这可能与母本长时间低温贮藏有关。此外,来自库存的种质,其田间出苗率也相对较低。     

小麦地方品种繁殖更新过程中的遗传多样性变化分析

采用分别保存于长期库及中期库的3个小麦地方品种的6份材料,进行了9项农艺性状及35个与农艺性状相关的微卫星标记检测,每份材料选取30个单株进行遗传多样性与遗传结构分析。结果表明:(1)更新前,3个小麦地方品种均为遗传异质性群体,在SSR位点上的异质度分别为57.14%、48.57%和5.71%。(2)在农艺性状表现上,只有温泉小麦3在株高和穗粒数上更新后比更新前显著增加,其他材料无显著差异。(3)在SSR位点多态性表现上,3个品种在更新后均发生了遗传多样性变化,8个与粒重、产量、生育期性状相关位点存在等位位点丢失现象,其中2个与粒重、生育期相关位点频率变化显著。(4)综合农艺性状调查与SSR分子标记检测结果发现,3个品种更新前后在多样性指数上无显著差异,遗传分化系数Gst分别为0.0269、0.0324和0.0380,即更新前后遗传差异分别为2.69%、3.24%和3.80%。上述结果建议,经繁殖更新的小麦种质资源能够比较完好地保持其遗传多样性和遗传结构。对于遗传异质性小麦地方品种在繁殖更新后存在遗传多样性丢失的危险,为了保证更新前后的遗传完整性,建议在繁殖更新过程中每个品种至少应保持300个单株的群体。     

Delayed Germination of Beauveria bassiana Conidia after Prolonged Storage at Low, Above-freezing Temperatures

Powder formulations were prepared with conidia of the entomopathogenic fungus Beauveria bassiana strain 447 originally isolated in Brazil from the red imported fire ant, Solenopsis invicta. The carrier materials used in formulations included talc hydrous magnesium silicate , silica gel, powdered rice and cornstarch. The formulations were stored in plastic containers under three conditions: a ambient temperature 15-38 C ; b refrigerator 6 2 C ; and c freezer 10- 7 C . Formulations stored under ambient temperature conditions completely lost viability after 1-8 months. Unformulated conidia stored under ambient conditions were totally unviable after just 2 months. All formulations stored under refrigerator and freezer conditions maintained 100 viability for 7 years. The virulences of the conidial preparations against adult workers of the fire ant, S. saevissima, and the sugarcane borer, Diatraea saccharalis, were higher for fresh conidia or conidia stored in the freezer than for conidia stored in the refrigerator. After 30 months of storage, the unformulated conidia and the formulations stored in the refrigerator showed slow germination and had low virulence. There was a strong correlation between the rate of germination and the virulence toward D. saccharalis, but not toward S. saevissima.     

Molecular characterization of the genetic integrity of wheat (Triticum aestivum L.) germplasm after long-term maintenance

The genetic identity of eight wheat (Triticum aestivum L.) accessions maintained in the Gatersleben genebank and regenerated up to 24 times was studied by using wheat microsatellite markers (WMS). It was demonstrated that WMS can be used to analyze bulks of seeds stored more than 50 years in a seed reference collection at room temperature. No contamination due to foreign pollen or incorrect handling during the multiplication cycles was discovered. For one accession (TRI 4599) genetic drift was observed, whereas for TRI 249 a heterogenous situation for two markers was maintained over the years. We were able to show that microsatellites can be used as a simple and reliable marker system for the verification of the integrity and genetic stability of genebank accessions. Received: 29 March 1999 / Accepted: 22 June 1999     

Loss of genetic diversity from heterogeneous self-pollinating genebank accessions

Genebank seed accessions of predominantly self-pollinating species may be stored either as bulked (mixed) seed lines or as pure line cultivars. If seed lines are bulked in storage then when considered over several regeneration cycles, loss of genetic diversity within heterogeneous self pollinating genebank accessions is shown to be severe. This within-accession loss of diversity represents opportunities foregone through the random loss of individual genotypes. Amongst working collections, the utility and repeatability of genebank accessions is paramount in the justification of the germ plasm resource. Therefore, the only practical solution to the management of predominantly self-pollinating species is to preserve individual accessions as pure lines.     

Germination capacity and viability of threatened species collections in seed banks

Facing the current biodiversity crisis, the value of ex situ conservation has been increasingly acknowledged in international treaties and legislations. Seed banks are a good way of conserving biodiversity, providing that seeds are of high quality and at maximum viability. However, despite the number of established ex situ facilities, there is little information on seed viability in botanic garden seed banks. This paper analyses the status of the seed collection of the National Botanic Garden of Belgium by determining the germination capacity and viability of seeds that have been stored for 1–26 years. It aims at: (1) ensuring that existing storage conditions provide effective ex situ conservation of threatened species; (2) providing viability data on threatened species; (3) planning future collection and storage efforts for seeds of West European species of conservation value. Results from this study showed that the germination and viability percentages of the 250 tested species reached on average 59 and 79% respectively. Some families typically performed better than others. Within a species, consistent results were not always obtained. Over a quarter of accessions exhibited some degree of dormancy. Considering the current lack of knowledge in seed germination and dormancy of many rare and threatened species, we believe that the quality of a seed collection should be estimated by its viability and not by its germination percentage. This study calls for further research in order to better understand the biology of a range of threatened native species.     

Dormancy Breaking and Storage Behavior of Garcinia cowa Roxb. (Guttiferae) Seeds: Implications for Ecological Function and Germplasm Conservation

The dormancy breaking and storage behavior of Garcinia cowa Roxb. seeds were investigated.The seeds of G. cowa had 8-11 months dormancy in their natural habitat. Seeds were matured and dispersed at the end of the rainy season (mid-late August to late September) and were scatter-hoarded by rodents as food for winter after the seeds had fallen to the ground. Seedlings often emerged in the forest during the rainy season (May to August) the following year. Intact seeds of G. cowa failed to germinate after being sown at 30 ℃ for 120 d and the mean germination time (MGT) of seeds cultured in a shade (50% sunlight)nursery was 252 d. The most effective method of breaking dormancy was to remove the seed coat totally,which reduced the MGT to 13 d at 30 ℃. Germination was also promoted by partial removal of the seed coat (excising the hilum and exposing the radicle) and chemical scarification (immersion in 1% H2O2 for 1 d).Unscarified seeds take up water rapidly in the first 96 h, but water was absorbed by the outside seed coat,without penetrating through it. The moisture content (MC) of G. cowa seeds was high (50% in fresh weight)at shedding. The seeds could tolerate desiccation to some extent, until the MC reached approximately 40%;below that, the viability decreases rapidly and all seeds died at approximately 17% of MC. Seed viability decreased rapidly when seeds were chilled at 4 ℃; germination was 2% after storage for 1 week. Even stored at 10 ℃, seeds began to be damaged after 4 weeks. Seed storage for 1 yr revealed that in both dry (relative humidity (35 ± 5)%) and moist (wet sand) storage conditions, seed viability declined, but germination percentages for seeds stored under moist conditions are better than for seed stored under dry conditions.Because of their low tolerance to desiccation, marked chilling sensitivity and relatively short lifespan, G.cowa seeds should be classified into the tropical recalcitrant category. The ecological implications of dormant recalcitrant seeds and cues on storing recalcitrant seeds were discussed.