落叶松-杨栅锈菌在感病杨树寄主上发育过程的组织学研究

采用荧光染色技术、光学显微镜和电子显微镜技术,系统研究了落叶松-杨栅锈菌在感病杨树叶片上的发育过程。结果表明,在侵染前期（接种12h以内）,锈菌夏孢子在杨树叶片上萌发,利用芽管或附着胞穿透叶表气孔后形成气孔下囊,进而在胞间产生侵染菌丝。进入活体营养生长阶段（接种后24-96h）,锈菌不断产生大量吸器来满足营养需求的同时,侵染菌丝在叶肉细胞间隙蔓延分枝生长至形成菌落结构。最终在产孢阶段（接种120h之后）产孢菌丝分化形成的夏孢子在表皮下聚集成堆,待成熟后突破表皮显露出来。     

小麦与叶锈菌互作过程中细胞程序性死亡的细胞学观察

小麦(Triticum aesetivum)品种洛夫林10和叶锈菌(Puccinia recondita f.sp tritici)小种162、165分别组成不亲和组合与亲和组合。透射电镜观察表明,在小麦与叶锈菌的不亲和组合中,接种后12h,侵染点周围叶肉细胞核变形;接种后24h,核内染色质开始凝聚,并趋于细胞核边缘,同时叶绿体膨胀;接种后48h,核内染色质凝聚加剧,叶绿体开始解体;最终在接种后72h,细胞核、叶绿体完全解体,线粒体开始退化。此外,内质网和液泡共同行使溶酶体功能,吞噬各种细胞器残体及原生质降解组分。以上结果表明：在小麦与叶锈菌不亲和组合的互作过程中,寄主细胞呈现细胞程序性死亡的典型特征。而在亲和组合中,叶肉细胞间隙中可见有大量菌丝蔓延,菌丝与寄主细胞壁接触后分化产生吸器母细胞。菌丝的存在对寄主细胞的超微结构产生一定影响。从接种后24h开始,与菌接触的细胞出现质膜下陷,叶绿体稍显膨胀;在接种后48h、72h,大部分叶绿体膨胀,而其它细胞器无明显变化。     

小麦与叶锈菌互作过程中细胞程序性死亡的细胞学观察

小麦(Triticum aesetivum)品种洛夫林10和叶锈菌(Puccinia recondita f.sp tritici)小种162、165分别组成不亲和组合与亲和组合。透射电镜观察表明,在小麦与叶锈菌的不亲和组合中,接种后12h,侵染点周围叶肉细胞核变形;接种后24h,核内染色质开始凝聚,并趋于细胞核边缘,同时叶绿体膨胀;接种后48h,核内染色质凝聚加剧,叶绿体开始解体;最终在接种后72h,细胞核、叶绿体完全解体,线粒体开始退化。此外,内质网和液泡共同行使溶酶体功能,吞噬各种细胞器残体及原生质降解组分。以上结果表明:在小麦与叶锈菌不亲和组合的互作过程中,寄主细胞呈现细胞程序性死亡的典型特征。而在亲和组合中,叶肉细胞间隙中可见有大量菌丝蔓延,菌丝与寄主细胞壁接触后分化产生吸器母细胞。菌丝的存在对寄主细胞的超微结构产生一定影响。从接种后24h开始,与菌接触的细胞出现质膜下陷,叶绿体稍显膨胀;在接种后48h、72h,大部分叶绿体膨胀,而其它细胞器无明显变化。     

短柄草柄锈菌在感病寄主二穗短柄草上发育过程的组织学研究

本研究采用荧光染色和荧光显微镜技术,系统研究了短柄草柄锈菌Puccinia brachypodii (分离系F-Co和K-Ki)在感病二穗短柄草Brachypodium distachyon自交系Bd21-3叶片中的发育过程。荧光显微镜观察结果表明,接种12-18 h时,病原菌通过芽管侵入短柄草叶表皮气孔后形成气孔下囊,产生初生菌丝并形成吸器母细胞,进而侵入植物细胞形成吸器;接种24-48 h后,病原菌初生菌丝分支并形成次生菌丝;接种72 h后,短柄草锈菌开始形成菌落。F-Co的发育过程快于K-Ki,在120-216 h时,F-Co的菌落扩展面积明显高于K-Ki。本研究证实F-Co、K-Ki和二穗短柄草均为亲和互作。     

条形柄锈菌(小麦条锈病菌)侵染结构体外形成的观察

通过荧光显微镜和扫描电镜分别对条形柄锈菌夏孢子在寄主植物-小麦叶表和非寄主植物-水稻叶表以及小麦穗部和茎秆上的萌发过程进行了观察。结果发现,夏孢子在小麦叶片体表萌发产生芽管后,可依次分化形成气孔下囊、初生菌丝与吸器母细胞;在小麦颖片、稃片及茎秆部位表面,同样可观察到病菌在体外分化形成吸器母细胞;并且在水稻叶片上也观察到病菌侵染结构存在体外分化现象。经荧光染色发现,条形柄锈菌在体外与在小麦组织中形成的侵染结构没有明显的差别。观察结果可为条形柄锈菌侵染结构的离体诱导与调控机理研究提供依据。     

小麦条锈菌吸器母细胞入侵菌丝现象的进一步研究

应用电镜技术对小麦条锈菌吸器母细胞入侵自身菌丝的现象进行了研究,观察发现,在吸器母细胞与寄主细胞和菌丝细胞同时相接触的情况下,入侵栓可在与寄主细胞接触处形成,也可在与菌丝接触处形成;在菌落中心部位,吸器母细胞虽然未与寄主细胞接触,但同样可在与菌丝细胞接触处产生入侵栓;吸器母细胞在与菌丝接触处形成的人侵栓,其超微结构正常,并且可侵入到菌丝细胞壁内,但是未能穿透菌丝细胞壁。本文观察结果表明,小麦条锈菌吸器母细胞和人侵栓形成所需诱导因子可能是物理接触作用,而不涉及到化学作用,并且该病菌与寄主间的识别作用可能发生在入侵栓形成之后。     

小麦条锈菌吸器母细胞入侵菌丝现象的进一步研究

应用电镜技术对小麦条锈菌吸器母细胞入侵自身菌丝的现象进行了研究。观察发现,在吸器母细胞与寄主细胞和菌丝细胞同时相接触的情况下,入侵栓可在与寄主细胞细胞接触处形成,也可在与菌丝接触处形成;在菌落中心部位,吸器母细胞虽然未与寄主细胞接触,但同样可在与菌丝细胞接触处产生入侵栓;吸器母细胞在与菌丝接触处形成的入侵栓,其超微结构正常,并且可侵入到菌丝细胞壁内,但是未能穿透菌丝细胞壁。本文观察结果表明,小麦条     

苜蓿假盘菌侵染苜蓿叶片的细胞学研究

采用微分干涉相差显微镜、扫描和透射电镜技术系统研究了苜蓿假盘菌Pseudopeziza medicaginis在苜蓿叶片的侵染过程及超微结构特征。结果表明,接种4h后,子囊孢子萌发产生芽管：12h后,芽管以直接侵入的方式进入表皮细胞形成侵染菌丝：24h后,表皮细胞中侵染菌丝向相邻表皮细胞扩展,同时侵入到叶肉细胞以胞内生长方式扩展：接种72h后,侵染菌丝在表皮细胞下的叶肉组织中形成初始菌落;第5d后,菌丝扩展至整个叶片组织,大量菌丝聚集形成子座组织,并进一步形成子囊盘与子囊。病菌菌丝在侵入寄主细胞初期,并不穿透寄主质膜与原生质,而是被其所包围。但随着菌丝进一步扩展,叶片组织发生了一系列的病理变化,其中包括叶肉细胞肿胀、细胞质消解、叶绿体等细胞器解体以及寄主细胞坏死塌陷,并最终在叶表面产生典型的褐斑病症状。     

苜蓿假盘菌侵染苜蓿叶片的细胞学研究

采用微分干涉相差显微镜、扫描和透射电镜技术系统研究了苜蓿假盘菌Pseudopeziza medicaginis在苜蓿叶片的侵染过程及超微结构特征。结果表明,接种4h后,子囊孢子萌发产生芽管;12h后,芽管以直接侵入的方式进入表皮细胞形成侵染菌丝;24h后,表皮细胞中侵染菌丝向相邻表皮细胞扩展,同时侵入到叶肉细胞以胞内生长方式扩展;接种72h后,侵染菌丝在表皮细胞下的叶肉组织中形成初始菌落;第5d后,菌丝扩展至整个叶片组织,大量菌丝聚集形成子座组织,并进一步形成子囊盘与子囊。病菌菌丝在侵入寄主细胞初期,并不穿透寄主质膜与原生质,而是被其所包围。但随着菌丝进一步扩展,叶片组织发生了一系列的病理变化,其中包括叶肉细胞肿胀、细胞质消解、叶绿体等细胞器解体以及寄主细胞坏死塌陷,并最终在叶表面产生典型的褐斑病症状。     

梨胶锈菌性孢子和锈孢子阶段吸器的超微结构研究

本文对梨胶锈菌性子期和锈子期菌丝吸器的形成方式、吸器及其与寄主细胞界面的超微结构进行了研究。观察结果表明：梨胶锈菌性子期和锈子期寄主胞间菌丝吸器的形成方式有两种：一种是由寄主胞间菌丝直接形成吸器;另一种是由寄主胞间菌丝先形成吸器母细胞,然后由吸器母细胞形成吸器。吸器在开始形成时只是一个乳头状的侵入楔,以后逐渐形成囊状、镰刀状、指状及其它不规则形状的吸器。多数吸器分化为颈和吸器主体两部分,在颈部及部分吸器主体外有一个由类似寄主细胞壁物质形成的领圈。吸器内部的超微结构与寄主胞间菌丝基本相同,但吸器壁比胞间菌丝或吸器母细胞的壁薄。吸器鞘的厚度随着吸器伸长膨大 而逐渐增厚。     

Ultrastructure of intercellular hypha and haustorium of the rust fungus,Uromyces euphorbiae

The ultrastructure of intercellular hyphae and dikaryotic haustoria of Uromyces euphorbiae, and the host response to haustorial invasion was investigated. The intercellular hyphae share common characteristics with those of other uredinial stages of rust fungi. Three types of septa were recognized inside the intercellular hypha. This study showed that the extrahaustorial membrane was possibly formed before the development of the haustorium. The periodic acid-thiocharbohydrazide-silver proteinate technique showed that the haustorial mother cell wall at the penetration site, and the haustorial wall contained more carbohydrates than other fungal structures. In addition, the neckband, present around the haustorial neck, contains different material from those of the rest of the haustorial neck wall. The close associations of host organelles, such as the nucleus, chloroplasts, mitochondria, endoplasmic reticulum and microtubules, with the haustorium, is described.     

苜蓿假盘菌侵染苜蓿叶片的细胞学研究

采用微分干涉相差显微镜、扫描和透射电镜技术系统研究了苜蓿假盘菌Pseudopeziza medicaginis在苜蓿叶片的侵染过程及超微结构特征。结果表明,接种4h后,子囊孢子萌发产生芽管;12h后,芽管以直接侵入的方式进入表皮细胞形成侵染菌丝;24h后,表皮细胞中侵染菌丝向相邻表皮细胞扩展,同时侵入到叶肉细胞以胞内生长方式扩展;接种72h后,侵染菌丝在表皮细胞下的叶肉组织中形成初始菌落;第5d后,菌丝扩展至整个叶片组织,大量菌丝聚集形成子座组织,并进一步形成子囊盘与子囊。病菌菌丝在侵入寄主细胞初期,并不     

尖角突脐孢菌侵染过程及稗草反应超微结构观察*

为了解尖角突脐孢菌侵染稗草植株的致病机理,应用电镜观察了该菌侵染稗草植株过程和寄主细胞的超显微结构变化。结果表明：尖角突脐孢菌分生孢子于接种8h后从突脐孢的基部开始萌发菌丝,接种13h后菌丝直接穿透稗草叶表面细胞连接处或经气孔侵入,接种后24～26h完成侵染过程。被侵染的寄主,膜结构发生变形,同时细胞线粒体的嵴变形膨大,叶绿体内的淀粉粒消失,寄主细胞内有大量酚物质出现。     

Micro-autoradiographic studies on host-parasite interactions

Tritium labeled uredospores of Uromyces phaseoli were produced be feeding the host, Phaseolus vulgaris, with ³H-orotic acid. These spores were allowed to germinate on and to penetrate into a bean leaf. 24 hrs after inoculation, the bean rust had formed the first haustorium. All fungal structures, including the fungus walls, were heavily labeled. No label could be detected in the cells that had come into contact with the hyphae. In the infected host cell, the haustorium was labeled heavily, but the sheath around the haustorium and the host cell remained free of label. These results indicate that no detectable amounts of label leach from the bean rust into the host at this stage of infection although it is known that the rust takes up many metabolites. Since the sheath remains free of label and all fungal structures are evenly labeled, it is concluded that the sheath is formed by the host.     

Histopathology of Leaf Rust Infection and Development in Wheat Genotypes containing Lr12 and Lr13

Evidence exists that certain genes for resistance to leaf rust in wheat, e.g. Lr13 and Lr34 , may interact with other genes to condition higher levels of resistance than that conferred by each gene individually. In this study, the hypothesis that Lr12 and Lr13 , both genes for adult plant resistance to Puccinia recondita Roberge ex. Desmaz f. sp. tritici Eriks. and Henn., interact to confer an improved level of resistance, was investigated using fluorescence and phase-contrast microscopy. Flag leaf segments of monogenic and digenic Thatcher lines, sampled 64 and 240 h post-inoculation, were stained with Uvitex 2B and screened, using fluorescence microscopy, for development of infection structures or host response. To study cell wall appositions, specimens were stained with trypan blue and a solution of picric acid in methyl salicylate. Aborted penetration, consisting of nonpenetrating appressoria and aborted substomatal vesicles, showed that inhibition of fungal growth in wheat lines containing Lr12 and/or Lr13 was activated, to a certain degree, before haustoria were formed. At 240 h after inoculation colony size indicated that fungal colonies in the Lr gene combination lines were generally smaller than in the parents, but not necessarily smaller than those in a line with Lr13 only. Host cell necrosis was more frequently associated with infection sites, specifically of pathotype UVPrt2, in the combination lines than in the parents. The morphology of cell wall appositions varied considerably from a narrow, luminous zone slightly wider in the centre, to a thick central part opposite the haustorium mother cell, sharply decreasing towards both ends. Histological assessments could, however, not conclusively prove pronounced resistance enhancement or unconventional resistance mechanisms due to combining the genes Lr12 and Lr13 .     

The Differentiation of Infection Structures as a Result of Recognition Events between some Biotrophic Parasites and their Hosts

Most uredospores of rust fungi develop infection structures in a typical pattern so that they can infect the host plant. The function of these infection structures is divided into the following three phases:

• 1 In the recognition phase, the germ tube recognizes the cuticle and the stoma. This process may occur independently from the host plant since copies of the cuticle induce similar reactions of the fungus. During fungal growth on the epidermis, unspecific stress responses of the plant are triggered.
• 2 In the signal phase, the fungal substomatal vesicle and infection hypha(e) contact the host cells within the leaf parenchyma. A signal from the host induces further development of the fungus. Haustorium mother cell differentiation is effected and haustorium formation is initiated. At the same time, the fungus suppresses the synthesis of stress metabolites by the plant.
• 3 In the parasitic phase, the fungus penetrates the host cell and complex interactions between host and parasite begin. A highly specialized interface around the haustorium develops presumably in order to allow a more efficient nutrient transfer from host to parasite. Eventual defence reactions of the plant, generally on the race-cultivar level, fail to be evoked or are suppressed in compatible combinations.

     

不同抗病性小麦品种上白粉菌吸器发育超微结构研究

利用电镜技术对不同抗病性小麦品种上白粉菌吸器发育及相应寄主细胞变化的超微结构进行了研究,并对吸器的Ca2+－ATP酶活性及几丁质的分布进行了细胞化学定位分析。结果表明,小麦白粉菌（Blumeriagraminisf．sp.tritici）成熟吸器在内部结构上类似一个代谢活跃的菌丝细胞,有大量的线粒体和多聚核糖体;Ca2+－ATP酶主要被定位在寄主质膜及病菌核膜上;随吸器的不断发育,吸器外膜厚度增加,同时Ca2+-ATP酶活性增强。几丁质均匀地分布在吸器壁上,其含量随吸器的成熟而增加。在不同抗病性小麦品种上,吸器细胞核最先退化,然后是线粒体的液泡化和多聚核糖体的解聚。中抗寄主细胞内的吸器普遍退化较早,相当一部分在吸器中心体阶段已解体。此外,高感寄主表皮细胞与叶肉细胞之间有发达的胞间连丝;而且在吸器形成后,能比中抗寄主细胞更快地增殖和聚积大量与能量代谢、物质合成及分泌活动有关的细胞器。