大豆疫霉菌对大豆下胚轴侵染过程的细胞学研究

 接种后1.5~24h,用光镜和电镜研究了2个大豆品种与大豆疫霉菌Ps411的亲和性和非亲和性互作。观察结果表明,大豆疫霉菌对大豆下胚轴的侵染过程可分为侵入前、侵入、皮层组织中的扩展和进入维管束组织4个连续阶段。大豆下胚轴接种后在25℃保湿培养,1.5h后游动孢子即形成休止孢并萌发产生附着孢,3h后侵入表皮细胞,6h后进入皮层组织,24h后进入维管束组织。病原菌主要以侵染菌丝直接侵入表皮,表皮细胞间隙是主要侵入部位。皮层细胞是病原菌定殖和发展的主要场所,胞间菌丝侵入皮层细胞并形成吸器。在菌丝与寄主细胞接触部位的寄主细胞壁与质膜之间常有胞壁沉积物的形成。在抗病品种上病菌的侵染事件与感病品种基本一致,但不能形成正常的吸器,胞壁沉积物明显多于感病品种,菌丝在寄主组织内的扩展明显受到抑制。利用β-1,3-葡聚糖免疫金标记单克隆抗体进行的免疫细胞化学的研究表明,胞壁沉积物内含有大量的β-1,3-葡聚糖,在大豆疫霉菌菌丝壁中也存在β-1,3-葡聚糖。以上结果表明,病原菌的侵染可诱导抗病寄主细胞内β-1,3-葡聚糖迅速的合成与积累、并形成胞壁沉积物,以抵御病菌的侵染与扩展。     

青杨叶锈病菌(Melampsora larici-populina Kleb.)侵染过程的超微结构研究

 采用电子显微镜技术对青杨叶锈病菌(Melampsora larici-populina Kleb.)的侵染过程进行了研究。发现该菌夏孢子萌发产生1~3个芽管,且具较多的树杈状分枝。芽管由气孔侵入,侵入前不形成明显的附着胞或仅个别芽管形成附着胞。芽管侵入气孔后在气孔腔内形成气孔下囊,再分化出圆形的膨大体而产生1~2支初生菌丝。初生菌丝在寄主细胞间扩展,与叶肉细胞壁接触后分化出吸器母细胞,吸器母细胞中的细胞器与胞间菌丝相同,双核。吸器母细胞产生侵入钉侵入叶肉细胞内部形成吸器,成熟吸器由细长具颈环的管状颈部和膨大的吸器体组成,此时胞间菌丝在吸器母细胞处分化出次生菌丝,在叶肉细胞间扩展形成次生菌落,产生孢子堆。病菌在寄主细胞间隙或沿寄主细胞壁延伸时,寄主细胞仍保持正常状态。     

三唑酮拌种对小麦条锈病菌叶部侵染过程的影响

 供试小麦种子用干拌法施药,在一叶期接种小麦条锈菌(Puccinia striiformis West)毒性小种,用整叶透明染色方法研究三唑酮拌种对条锈菌叶部侵染过程的影响.结果表明,由初生吸器形成开始,三唑酮对吸器产生和菌落扩展表现出多方面的影响.拌种植株叶片中条锈菌侵染菌丝的生长和分枝严重受阻,吸器母细胞和吸器形成显著减少,菌落亦不再进一步分化,多数侵染点还出现寄主细胞坏死。这些组织病理学变化与抗病品种的过敏性坏死反应很相似.     

小麦叶锈菌在感病寄主上发育的组织病理学和超微结构研究

 应用荧光显微技术、微分干涉技术和生物电镜技术,系统地研究了小麦叶锈菌在感病寄主上的发育过程及其超微结构特征。小麦叶锈菌在感病品种上的发育过程可分为几个明显的阶段,即孢子的萌发、附着胞的形成、气孔下囊的分化、初生菌丝和次生菌丝的形成和生长、吸器母细胞和吸器的形成、夏孢子床和夏孢子堆的产生以及夏孢子的形成。小麦叶锈菌的胞间菌丝呈丝状,生长和分枝通常沿寄主细胞壁进行。胞间菌丝与寄主细胞的接触诱导了吸器母细胞的分化,吸器母细胞在与寄主细胞壁的接触部位发育形成入侵栓,穿透寄主细胞壁后于细胞内形成吸器。胞间菌丝和吸器母细胞均含有双核,而成熟吸器则含有单核。经常规染色后,胞间菌丝和吸器母细胞的壁与隔膜均可分辨出由多层构成。     

内吸杀菌剂烯唑醇对小麦条锈菌和白粉菌发育影响的研究

 小麦幼苗分别用小麦条锈菌和白粉菌接种3天后,用内吸杀菌剂烯唑醇喷雾施药。电镜观察烯唑醇对条锈菌和白粉菌在寄主上发育的影响,结果表明,烯唑醇引起两种病菌和寄主细胞发生一系列变化。小麦条锈菌和白粉菌菌丝细胞壁的内层普遍不规则地加厚,菌丝细胞的隔膜发育受阻而成为畸形;两病菌的吸器外间质变宽,并沉积有电子致密度较高的物质。小麦条锈菌的部分吸器母细胞产生的畸形入侵栓,不能穿透寄主细胞壁,部分吸器不能正常发育,吸器体呈分枝状,不能完全扩张、膨大。此外,被侵小麦细胞所分泌的物质可将条锈菌吸器完全包围起来。小麦条锈菌和白粉菌以上的细胞学变化可能导致了它们进一步发育受阻。     

种衣剂17号包衣对小麦条锈菌影响的组织病理学研究

种衣剂１７号内含三唑醇等杀菌剂和其它化学成分，小麦种子用种衣剂包衣，出苗后一叶期接咱小麦条锈菌毒性小种，采用荧光染色技术和整叶透明技术，研究了种衣剂１７号对条锈菌在寄主内发育的影响。观察结果表明，该种衣剂对对叶表的夏孢子萌发和芽管入侵无明显影响，但可使菌丝扩展和菌丝分枝严重受抑，吸器母细胞和吸器形成的数目减少，每一侵染点的吸器一般不超过２个，并且对吸器具有致畸作用。在多数侵染点内可观察到寄主细胞坏     

小麦全蚀病菌不同致病力菌株的致病特点

利用小麦种子根接种小麦全蚀病菌Gaeumannomyces graminis var．tritici，研究了不同致病力菌株的致病特点。结果表明，弱致病菌株可侵染小麦，但罹病过程缓慢，接种第5天仅在皮层观察到少量菌丝体，13天有少量菌丝进入中柱，中柱组织在菌丝侵入前褐变，未出现导管堵塞现象，也不能导致典型的黑根症状。强致病菌株接种第2天可侵入皮层，8天即进入中柱，并在寄主组织内产生大量菌丝体，致使寄主皮层组织和中柱细胞大量褐变和坏死，以及导管堵塞。     

广寄生侵染广宁红花油茶过程的组织解剖学观察

本研究通过石蜡切片和显微观察,从组织解剖学水平观察了广寄生Taxillus chinensis侵入广宁红花油茶Camellia semiserrata的过程。结果表明:广寄生侵入寄主有2种形式,一种是种子侵入,另一种是缠绕根侵入。种子侵入主要是通过自身分泌的胶状物质在寄主细胞间流动并包裹寄主细胞,随后降解寄主细胞形成多个微小的囊状结构,同时寄主形成愈伤组织,逐渐将广寄生种子包裹到体内。缠绕根侵入则是通过“膨胀螺丝结构”将寄主皮层撑开,同时吸根组织不断分泌胶状物质进入寄主组织降解寄主细胞,并逐渐生长进入寄主体内。本研究为进一步揭示广寄生的致病机制具有一定的参考意义。     

列当生防菌Br-2的DsRed红色荧光标记及定殖

为探明生防菌Br-2在分枝列当体内及番茄根围的定殖能力,采用PEG-CaCl_2介导的原生质体转化体系将红色荧光蛋白基因DsRed转入到菌株Br-2中,并构建其生长曲线,测定其对分枝列当种子萌发的抑制率,通过共聚焦显微镜观察其在分枝列当茎内及番茄根围的定殖情况。结果表明:通过原生质体转化体系得到了标记菌株Br-2-DsRed,继代培养5代后,其在共聚焦显微镜下仍可观察到亮红色荧光,经PCR检测带有DsRed基因,证明其稳定性好。标记菌株Br-2-DsRed与野生菌株Br-2的生长曲线基本一致,对分枝列当种子萌发的抑制率分别为75.86%和74.14%,无显著差异。显微观察发现,标记菌株Br-2-DsRed接种1 d后即能够侵染分枝列当的茎部表皮,3 d后主要分布在茎表皮和厚壁细胞间隙,5 d后侵染到厚壁细胞及维管束细胞内部并导致茎部腐烂;而标记菌株Br-2-DsRed不能侵染番茄根尖的内部,主要定殖在番茄根尖表面。     

寡聚糖诱导黄瓜对白粉病抗病反应的超微结构研究

 中科6号(2%氨基寡糖素)处理黄瓜植株叶片,5 d后接种白粉菌Sphaerotheca fuliginea(Schlecht.) Poll.,可诱导黄瓜Cucumis sativus产生对白粉病的抗病性,寄主细胞对病原菌的侵入产生了防卫反应结构和物质以及过敏性坏死反应。表现为寄主细胞壁加厚,染色加深,寄主细胞壁下产生多层次结构的乳突,在寄主细胞壁与质膜之间有黑色物质沉积;吸器外质膜皱褶,染色加深,吸器外基质中出现染色加深的颗粒状电子沉积物;寄主细胞质紊乱,细胞器解体,整个寄主细胞解体、坏死。     

小麦新抗源一粒葡抗条锈病的组织学和超微结构研究

 采用荧光显微镜、微分干涉显微镜和电子显微镜技术,系统研究了小麦新抗源一粒葡抗小麦条锈病的组织学和超微结构特征。结果表明:相对于感病品种铭贤169,一粒葡对条锈菌的侵染,在组织学和超微结构上均表现出明显的抗性特征。在组织学水平,表现为菌丝生长受抑,菌落发育延迟或败育,吸器母细胞和吸器数目明显减少;同时,侵染点的寄主细胞表现出不同程度的过敏性坏死症状。电镜观察发现,在一粒葡和感病品种中,条锈菌均可由芽管顶端直接进入或通过形成附着胞进入小麦气孔。其后,在一粒葡上,病菌胞间菌丝、吸器母细胞、吸器在细胞和亚细胞水平均发生了一系列异常变化,表现为原生质染色逐渐加深,液泡增多变大,逐渐消解原生质;胞间菌丝、吸器母细胞细胞壁不规则增厚;胞间菌丝线粒体肿胀,数目增多,逐渐解体;吸器母细胞细胞质逐渐空泡化后丧失其生理功能;吸器外质膜皱褶;吸器外间质加宽并有丝状或颗粒状物质形成,吸器体壁逐渐消解出现孔洞,吸器体最终畸形坏死。同时,寄主细胞产生一系列显著的结构防卫反应:形成胞壁沉积物、乳突、吸器鞘等结构,以及发生坏死,阻碍并抑制病菌的发育及扩展。     

Possible peroxidase functions in the interaction between the parasitic plant, Orobanche aegyptiaca, and its host, Arabidopsis thaliana

The mechanism by which the flowering holoparasitic plant, Orobanche aegyptiaca , infects its host without evoking a defence mechanism is still poorly understood. In this work, we studied several mechanisms used by phytopathogenic fungi. We focussed on the possible role of peroxidases during O. aegyptiaca penetration into the roots of Arabidopsis thaliana . A convenient experimental system for studying the interaction under sterile conditions was developed. The formation of extracellular reactive oxygen species (ROS) was detected at the interaction site before, during, and after the parasite penetrated into the host. These extracellular ROS probably originated from the parasite. However, no intracellular ROS could be detected at the site of the interaction. Peroxidase activity was observed mainly at the apex of the root of the parasite and in the adventitious roots of the tubercle. Benzhydroxamic acid, a peroxidase inhibitor, was used to probe the possible role of peroxidase in the infection process. Peroxidase activity was observed in the root apex and adventitious roots of O. aegyptiaca, but no evidence was found for its participation in the actual infection process. Peroxidase activity was also found in the later stages of the interaction between the host and the parasite. We propose that peroxidases could have a role in generating extracellular ROS for loosening the cell wall of the host in order to facilitate penetration. Alternatively, the ROS could act in facilitating the root elongation of the parasite.     

Effects of brassinolide on the growing of rice plants

Brassinosteroids are plant steroid hormones that are essential for plant growth. When germinated rice seeds were treated with brassinolide (BL), stems were elongated and root spiral formation was observed at 5 nM of BL. Such root spiral formation was not induced by other plant hormones such as auxin and gibberellin. Since weak non-steroidal brassinolide-like compound (NSBR1) also induced spiral formation, this root spiral induction can be used as the index in the search for BL-like compounds.     

Methyl jasmonate and methyl salicylate, but not cis-jasmone, evoke defenses against infection of Arabidopsis thaliana by Orobanche aegyptiaca

The mechanism by which some plant species develop resistance to the root parasite, broomrape ( Orobanche aegyptiaca ), is still not clear. Resistance to other pathogens can be induced by methyl jasmonate and systemic acquired resistance can be induced by treatment with salicylic acid, while cis -jasmone can act as a signaling molecule in plant–insect interactions. The three compounds studied, methyl jasmonate, cis -jasmone, and methyl salicylate, were applied to Arabidopsis thaliana seedlings that were then transferred to Nunc cell culture plates and exposed to the germinating seeds of O. aegyptiaca . The number of infections of the roots of single seedlings of A. thaliana was then quantified. Exposure for 24 h to very low concentrations of methyl jasmonate or methyl salicylate, which were then removed, effectively induced resistance to infection of A. thaliana by O. aegyptiaca , reducing attachment and tubercle formation by 90%. cis -Jasmone was far less effective in inducing a similar resistance to infection. These results support the view that methyl jasmonate can induce almost full resistance to infection by broomrape. The fact that such resistance is not observed under normal conditions of infection supports the idea that the root parasite does not evoke the full defensive response in the host plant.     

菜豆锈病菌侵染对寄主超微结构的作用及菜豆抗锈病的细胞学表现

 在电镜下观察发现,菜豆锈病菌侵染菜豆后,逐步对其超微结构产生影响:寄主细胞发生质壁分离;叶绿体变形;叶绿体的片层结构排列零乱;线粒体脊模糊不清,直至叶绿体解体;线粒体空泡化;少数细胞的细胞壁分解;不同细胞的细胞器堆积在一起。同时,病原菌的侵染激发了寄主抗病性的细胞学表现:供试的抗感菜豆品种都表现为在病原菌侵入位点的寄主细胞壁内侧有高电子致密物质沉积;与吸器母细胞接触的寄主细胞壁加厚以及在吸器颈周围有电子不透明物质形成。只是这3种反应在抗病品种中表现得更加强烈。此外,抗病品种中还有一些特有的抗性特征,如被侵染细胞及其相邻细胞的快速坏死,吸器母细胞侵入位点的寄主细胞壁外侧也有一种高电子致密物质沉积,抗病品种中真菌吸器周围聚集含大量线粒体的寄主细胞的细胞质,且吸器外基质比感病品种中的宽。     

Microscopical studies of resistance to powdery mildew disease in the hop cultivar Wye Target

Microscopical studies of fungal development and host responses during infection of the hop cultivars Northern Brewer (susceptible) and Wye Target (resistant) with a Zenith isolate of Sphaerotheca humuli are described. Resistance to powdery mildew disease in cv. Wye Target is principally determined by the R₂ major gene. Fungal growth was typically restricted in cv. Wye Target following formation of a single haustorial initial or haustorium which failed to develop the characteristic lobes found in susceptible cells. The hypersensitive reaction of penetrated epidermal cells was associated with death of haustorial initials but the associated appressorium remained alive during the first 2 days after inoculation. In leaves expressing resistance, histochemical staining revealed deposition of lignin-like material and callose in penetrated cells and to a lesser extent in underlying palisade mesophyll cells. Transmission electron microscopy and enzymic digestion clearly demonstrated extensive paramural deposition of β-1.3 glucans (callose) in reacting mesophyll cells. Plant cell death, lignification and widespread callose deposition were rarely observed at infection sites in cv. Northern Brewer but collars of callose were deposited around the necks of all haustoria formed.     

胡杨根际可培养细菌的分离及抑制瓜列当种子萌发研究

从胡杨生存的干旱强光照逆境中获得新的细菌资源,从中筛选新的可抑制瓜列当种子萌发的生防菌。采用3种分离培养基,以稀释涂布法对塔里木河流域3处胡杨根系样品进行可培养细菌分离,通过分析分离菌株16S rRNA基因序列确定其种属分类。采用皿内培养法测定其对瓜列当种子萌发的抑制活性,利用盆栽试验检测分离菌株M2-3对瓜列当寄生的防治效果。结果分离获得98株细菌,分属于28个属,马赛菌属Massilia、Pontibacter、玫瑰单胞菌属Roseomonas为优势菌属。其中,菌株M2-3与Pontibacter salisaro HMC5104T的相似度最高,为97.92%,其菌体发酵液10倍稀释液对瓜列当种子萌发抑制率为87.8%,盆栽试验表明该菌株对瓜列当防效可达36.9%,具备进一步开发可能性。     

小麦与条锈病菌不亲和互作的超微结构

 采用条锈菌同一小种的野生型菌系和弱毒突变菌系,分别接种同一小麦品种的方法,研究了不亲和互作的超微结构特征。在不亲和互作中,条锈菌的胞间菌丝、吸器母细胞和吸器明显受抑。吸器可以在发育早期受抑坏死,也可迟滞至吸器体形成之后坏死。吸器外质膜严重皱褶,并出现孔洞,吸器外间质加宽,沉积大量电子致密物质。侵染位点的小麦叶肉细胞表现与过敏性坏死反应相关联的一系列变化。细胞壁内侧还出现乳突状或颗粒状沉积物等防御结构或物质。     

天然油菜素内酯对五种牧草种子发芽和胚根下胚轴伸长的影响

用9个不同浓度的天然油菜素内酯溶液浸种处理5种牧草种子,观测其对种子发芽和胚根下胚轴伸长的影响。结果表明,0.01 mg/L浓度处理使苜蓿种子发芽率比对照提高了32.2%,发芽天数缩短了1.4 d;0.01mg/L处理使鲁梅克斯种子发芽率增加了27.8%,0.05 mg/L处理使其发芽天数提前了0.8 d;0.03 mg/L处理使普那菊苣种子发芽率提高了28.9%,发芽天数缩短了0.3 d;0.4 mg/L处理使串叶松香草种子发芽率增加了26.7%,发芽天数提前了1.2 d;0.03 mg/L处理使小冠花种子发芽率提高了23.3%,0.05 mg/L使其发芽天数缩短了0.9 d。0.05、0.07、0.03、0.4和0.03 mg/L处理对苜蓿、鲁梅克斯、普那菊苣、串叶松香草和小冠花胚根下胚轴伸长的促进效应最为明显。