日本蚱的生活史及其它生物学特性

日本蚱Tetrix japonica是一种广布于东亚地区的直翅目昆虫。本文通过野外观察与室内饲养相结合的方法,研究了日本蚱的卵块和各虫龄的形态特征、生活史、若虫及成虫的主要生活习性。结果表明：日本蚱喜欢栖息于具苔藓的矮草地表,主要取食幼嫩苔藓及腐殖质;在羽化7 d后开始出现交配现象,交配时间为1~1.5 h;交配后1~3 d内将大米粒状卵粒产于苔藓泥土中,卵块的形状近似橘瓣状,卵粒数目通常为10~30粒;卵经过6~10 d可孵化为若虫;雄性共有6龄,雌性共有7龄,每个虫龄历期随虫龄的增长而增加;不同虫龄的日本蚱在形态上具有一定的差异。此外,研究还发现日本蚱的前胸背板与翅型存在多态现象,可能在进化适应中起重要作用。     

稗类(Echinochloa spp.)植物的开花生物学特性

对稗类（Echinochloa spp.）常见种类[稗Echinochloa crusgalli(L.)Beauv.;无芒稗 E.crusgalli var.mitis(Pursh)Peterm.;西来稗E.crusgalli var.zelayensis(H.B.K.)Hitchc.;细叶旱稗E.crusgalli var.praticola Ohwi;旱稗E.hispidula(Retz.)Nees和光头稗E.colonum(L.)Link]的开花过程和节律,温度、光周期、晴天和阴雨天对其中部分稗类植物开花的影响以及套袋条件下无芒稗和旱稗的结实率进行了研究。结果表明,不同稗类植物的开花的过程基本相似,从颖壳微微张口到闭合大约需20－30min,但花约伸出颖壳后,散落花粉的过程很快,颖壳闭合后柱头外露率达100％。稗类植物每穗开花持续时间较长,一般为20－25d,随种类的不同略有变化;稗类植物每穗每天开花数量的变化趋势基本呈抛物线状,每天的开花比例变化较平缓,即使在开花高峰期,开花数也只占总数的10％－15％,开花高峰期因稗草种类的不同略有变化,但都在始花后11－15d左右。每日的开花节律为70％－80％的颖花在7：00之前开,15％－20％在7：00－8：30开,8：30之后零星开花,10：30尚未见开花。温度、光周期、晴天和阴雨天对开花都有一定的影响。不同条件下的结实率没有明显差异。     

濒危植物峨眉黄连的生活史和繁殖特性及生态特征

峨眉黄连（Coptis omeiensis（Chen）C.Y.Cheng）是一种药用价值较高的国家二级保护植物。采用野外观察与室内解剖的方法,详细描述和分析了峨眉黄连的生活史、繁殖特性及生态特征,并寻找致危因子。结果表明：峨眉黄连从种子萌发至自然死亡,其生活史可分为4个时期,寿命长达15年以上。峨眉黄连行有性繁殖,无侧生无性繁殖枝;顶生芽是一个混合芽,由侧生花序和1个定芽组成;花的各部分均发育正常,花瓣原基和雄蕊原基同源;花粉粒直径16-24μm,有刺状雕纹。种子腹面有窄翼状突起,胚后熟,翌年萌发。海拔1100-1700m的阴湿岩壁是其最适生长环境,降雨量、温度、湿度和光照等因素对其生存与分布至关重要。     

大猿叶虫龙南种群的生物学特性

系统研究大猿叶虫Colaphellus bowringi Baly江西龙南(24°9′N,114°8′E)种群生物学特性。结果显示,该虫仅在春季和秋季发生为害,以成虫在土中越冬和越夏。由于成虫滞育期的差异,该虫显示出生活史多样性,有些个体隔年繁殖;有些个体是一化性,仅在春季或秋季繁殖1代;有些个体是二化性,在春季和秋季各繁殖1代;有些个体是多化性的,春季1代,秋季2~3代,因此,在田间1年可发生1~4代。春季,滞育成虫于2月中旬至4月初陆续出土繁殖,羽化的成虫于4月上旬至5月中旬陆续入土越夏;秋季,滞育成虫于8月中旬至10月中旬陆续出土,羽化的成虫于9月中旬至12月中旬陆续入土越冬。成虫一生能多次交配,在25℃下,春季世代雌虫产卵期为8~29d,平均产卵量为776粒;秋季世代雌虫产卵期为9~39d,平均产卵量为1003粒。各虫态的发育历期:在18~28℃间,卵为8.66~3.85d,幼虫为19.37~7.92d,蛹为8.57~3.41d。卵、幼虫和蛹的发育起点温度分别为10.5、11.5和11.9℃。滞育成虫的寿命为5~28个月。     

干湿交替灌溉下不同稗草种对水稻产量及生理特性的影响

以两优培九(籼稻)和南粳9108(粳稻)为材料,从移栽至成熟期分别与无芒稗(T₁)、稗(T₂)、西来稗(T₃)和光头稗(T₄)共生,以无稗草水稻处理为对照,研究干湿交替灌溉条件下不同稗草种对水稻产量和生理特性的影响.结果表明： 与对照相比,T₁、T₂、T₃和T₄处理下两优培九分别减产13.8%、10.6%、23.8%和0.5%,南粳9108分别减产45.5%、36.9%、60.7%和15.1%.T₁、T₂和T₃处理显著降低了水稻产量,T₄处理对两优培九产量无显著影响,但显著降低了南粳9108的产量.T₁、T₂、T₃和T₄处理增加了水稻灌浆期叶片丙二醛含量,降低了叶片中过氧化氢酶、过氧化物酶和超氧化物歧化酶的活性,降低了成熟期干物质积累量、灌浆期根系氧化力以及根系中吲哚-3-乙酸和玉米素+玉米素核苷的含量.4种处理对水稻各生理指标的影响程度为T₃>T₁>T₂>T₄.稻-稗共生时水稻灌浆期叶片抗氧化系统酶活性、根系氧化力、根系中吲哚-3-乙酸和玉米素+玉米素核苷含量及成熟期干物质积累量的降低以及灌浆期叶片丙二醛含量的增加是水稻减产的重要原因.     

稗草生防真菌稗属炭疽菌(Colletotrichum echinochloae) B-48的生物学特性及基因组测序分析

【背景】稗草生防真菌稗属炭疽菌(Colletotrichum echinochloae) B-48是从水稻田自然发病的稗草上分离鉴定得到的,前期研究发现该菌株对稗草具有良好的生防效果,对主要作物如水稻、小麦、玉米等具有良好的安全性。【目的】研究稗草生防真菌B-48的最佳生长和产孢的培养基、生长温度、pH、光照条件、碳氮源等生物学特性,以便优化该菌株的培养和应用条件。解析该生防菌株的基因组序列信息,挖掘其次级代谢产物基因资源,为深入研究该菌株的除草活性天然产物及天然产物的生物合成机制奠定基础。【方法】对稗草生防真菌B-48的生长最适培养基、温度、pH、光照、生长碳氮源及致死温度等生物学特性进行研究。利用Nanopore及Illumina测序平台对稗草病原真菌B-48进行全基因组测序,采用相关软件进行菌株基因组序列拼接、基因组结构预测,以及基因组功能注释、并预测其次级代谢产物合成基因簇。【结果】稗草生防真菌B-48在马铃薯蔗糖琼脂(potato sucrose agar, PSA)培养基上生长产孢良好,最适生长温度为30 ℃,最适生长pH 7.0,最适光照条件为持续光照,最适碳氮源分别为淀粉和酵母浸粉,致死条件为55 ℃、10 min。全基因组序列结果显示该菌株基因组大小为62.25 Mb,G+C含量46.59%,预测到蛋白质编码基因11 324个,预测到次级代谢产物生物合成基因簇76个。【结论】稗属炭疽菌B-48具有开发为稗草生物除草剂的潜力,其次级代谢产物生物合成基因簇预示着其具有合成除草活性天然产物的潜力。以上结果为该菌后续发酵培养、次级代谢生物合成研究及实际应用奠定了理论基础。     

AM真菌生活史、遗传特性与纯培养的生物学基础

<正>丛枝菌根(AM)真菌可能是地球上最古老的通过无性繁殖后代的多核生物,属于单元类群。基于AM真菌分子特征的研究进展,Schü?ler等在真菌界(Fungi)建立一个新门——球囊菌门Glomeromycota,并提出了AM真菌最新分类系统:包括1个纲,4个目,7个科,9个属,200余种。虽然该类真菌的分类地位越来越高,但对其生活史和遗传特性了解甚微,而且目前尚未获得纯培养。     

农作物抗除草剂遗传工程研究进展

控制杂草提高农作物产量是农业生产中共同面临的问题,发展抗除草剂农作物将是最经济最方便控制杂草的技术。由于对除草剂的作用模式和除草剂代谢途径的了解,弄清了除草剂的关键靶酶及其基因,因此分离除草剂靶酶基因,克隆能解毒除草剂的酶基因,通过转化技术可获得抗除草剂农作物,大量的抗除草剂转基因农作物大田试验表明,将最有希望在２０００年进入市场。     

除草剂对杂草微观进化及多样性的影响

本文归纳了除草剂作用下杂草种下分化的机理及影响这一过程的内外因素,指出除草剂作用下农田杂草多样性的特点及杂草遗传和多样性变化研究的理论意义。     

Biorational management tactics to select against triazine-resistant Amaranthus hybridus: a field trial

1. The individual and joint effectiveness of two biorational tactics (crop interference and exploitation of negative cross-resistance to certain herbicides) in the management of triazine-resistant Amaranthus hybridus L. (smooth pigweed) were estimated. Biorational tactics exploit biological idiosyncracies of resistant (R) genotypes to maximize fitness cost(s) of resistance. We quantified selection against triazine resistance by relative performance comparisons between lines having comparable nuclear genomes but either resistant or susceptible cytoplasm. Increasing soybean density by reducing row spacing (from 76 cm to 25 cm) did not significantly increase the fitness cost of resistance.
2. Low doses of bentazon (100 and 300 g active ingredient ha^–1) did strongly increase the cost of resistance. Over 2 years, the mean relative performance of R genotypes in bentazon treatments was 0·40, compared to 0·60 in the absence of bentazon. Therefore, use of bentazon in soybean production has the potential to delay evolution of triazine resistance in maize–soybean rotations using triazines.
3. There was no consistent indication that increased soybean density and bentazon herbicide could act synergistically to increase costs of triazine resistance in Amaranthus hybridus . Nor were differences in response to biorational tactics evident between the two populations of origin (Maryland and Virginia, USA) from which experimental lines were derived.
4. Effects of the biorational tactics differed markedly between years, highlighting that resistance management depending primarily on these tactics would have widely variable results. Use of such tactics is likely to be most effective in the context of diversified weed management.     

Life history traits variation in heterogeneous environment: The case of a freshwater snail resistance to pond drying

Ecologists and population geneticists have long suspected that the diversity of living organisms was connected to the structure of their environment. In heterogeneous environments, diversifying selection combined to restricted gene flow may indeed lead to locally adapted populations. The freshwater snail, Galba truncatula, is a good model to address this question because it is present in a heterogeneous environment composed of temporary and permanent waters. In order to test the selective importance of those environments, we proposed here to measure survival of lineages from both habitats during drought episodes. To this purpose, we experimentally submitted adults and juveniles individuals from both habitats to drought. We found a difference in desiccation resistance between temporary and permanents waters only for adults. Adults from temporary habitats were found more resistant to drought. This divergence in desiccation resistance seems to explain the unexpected life history traits differences between habitats observed.     

基于同质园栽培的21种淫羊藿属植物花部特征的分类学意义

以采自中国多地并同质园栽培于吉首大学种质资源圃的21种淫羊藿为研究材料,通过观测这些物种的花梗长、花直径、内萼片长宽、蜜距长、雌雄蕊长、花药长、花柱长、胚珠数、花粉大小及花粉量等16个花部特征数量性状和花序类型、有无蜜距、花瓣颜色、内萼片颜色、内萼片与花瓣相对长度及花粉颜色6个质量性状,并对其分类学意义进行探讨。结果表明,(1)21种淫羊藿内轮萼片花瓣状,4枚花瓣除无距淫羊藿外均特化成蜜距,但花部形态种间存在显著差异,尤其体现于花直径、内萼片长宽、蜜距长、雌蕊长、胚珠数、花粉量、花粉直径等特征。(2)主成分分析显示花直径、内萼片长、花药长、胚珠数和花粉直径等性状信息负荷量较大,在该属分类中起主要作用。(3)根据花部特征聚类分析,物种间区分良好,21物种可分为4支:第1支花小,花瓣短于内轮萼片,囊状距或兜状距;第2支花较大,花瓣远长于内轮萼片,长距状;第3支花小,花瓣没有特化形成蜜距;第4支花较小,花丝伸长明显,可达10 mm,花蜜距呈钻状。(4)依据所观察到的花部形态特征编写了淫羊藿属21种植物花部特征分种检索表。研究认为,基于同质园栽培下的淫羊藿属物种的花部特征具有分类学意义,可以为该属分类提供一定依据。     

Evolutionary-thinking in agricultural weed management

Agricultural weeds evolve in response to crop cultivation. Nevertheless, the central importance of evolutionary ecology for understanding weed invasion, persistence and management in agroecosystems is not widely acknowledged. This paper calls for more evolutionarily-enlightened weed management, in which management principles are informed by evolutionary biology to prevent or minimize weed adaptation and spread. As a first step, a greater knowledge of the extent, structure and significance of genetic variation within and between weed populations is required to fully assess the potential for weed adaptation. The evolution of resistance to herbicides is a classic example of weed adaptation. Even here, most research focuses on describing the physiological and molecular basis of resistance, rather than conducting studies to better understand the evolutionary dynamics of selection for resistance. We suggest approaches to increase the application of evolutionary-thinking to herbicide resistance research. Weed population dynamics models are increasingly important tools in weed management, yet these models often ignore intrapopulation and interpopulation variability, neglecting the potential for weed adaptation in response to management. Future agricultural weed management can benefit from greater integration of ecological and evolutionary principles to predict the long-term responses of weed populations to changing weed management, agricultural environments and global climate.