外源诱导尾叶桉非培养内生细菌的激活

【目的】探究桉树非培养内生细菌的激活,为应用内生细菌防治桉树青枯病提供参考。【方法】选用恶臭假单胞杆菌WCS358r、荧光假单胞杆菌WCS374r及其嗜铁素缺失突变体JM218和Mut2,荧光假单胞杆菌WCS417r及其脂多糖缺失突变体WCS417OA-(B4)作为外源激活菌株,在限菌系统中采用尾叶桉无菌实生苗与外源菌共培养方法,外源菌作为激活因子对桉树非培养内生细菌进行激活,使植物体内非培养内生细菌恢复可培养状态,并依次利用抗利福平检测、革兰氏染色反应和分子鉴定方法对分离到的内生细菌进行鉴定。【结果】3种外源菌WCS358r、WCS374r和WCS417r分别与同源同代桉树苗共培养后,WCS358r和WCS417r处理的桉树苗中均获得被激活的细菌。WCS358r可定殖于桉树体内,且在不同部位激活出2株解淀粉芽孢杆菌;WCS417r可在桉树根、茎和叶内定殖,且在根和茎内的定殖量显著高于叶片,但不能激活桉树体内的非培养内生细菌。不同种子桉树苗经WCS358r激活后,分离到的菌株种类存在差异,分别激活出链霉菌、苏云金杆菌、解淀粉芽孢杆菌和其他芽孢杆菌,且WCS358r在根、茎内的定殖量表现...     

野生蒜头果丛枝菌根真菌和深色有隔内生真菌调查研究

为探明我国特有濒危野生植物资源蒜头果根系中丛枝菌根真菌(AMF)和深色有隔内生菌(DSE)的定殖状况,对蒜头果的天然分布中心—云南省广南县4个蒜头果主要分布点的AMF及DSE自然定殖情况进行调查研究。结果表明:蒜头果根系能被AMF及DSE双重定殖,并形成良好的共生关系,且DSE的平均定殖率(52.69%)高于AMF平均定殖率(46.96%)。其AMF和DSE的自然定殖率因立地条件而异,在4个分布点中,以旧莫乡汤盆村AMF自然定殖率最高,达70.75%,以懂堡乡三仙洞村DSE定殖率最高,达76.58%。     

纵坑切梢小蠹伴生菌危害机理的研究

该文对纵坑切梢小蠹伴生菌Leptographium yunnanense的危害机理作了初步研究，结果表明，L.yunnanense在与小伴随侵入后，产生致病毒素对寄主树林进行危害，从而辅助纵坑切梢小蠹成功定殖于寄主树木内，该毒素在低浓度条件下仍维持一定的致病力，进一步表明伴生菌在小蠹虫成功蛀害的过程中具有重要的作用。     

杨树腐烂病拮抗细菌的筛选及其定殖研究

通过平板对峙培养,从1 013株分离于杨树干部的拮抗细菌中筛选出13株对杨树腐烂病病原菌(Valsa sordida)有较强拮抗作用的菌株;再结合发酵液的生长抑菌率测定,进一步筛选出了抑菌作用最强的JK-SH007和JK-SX001两株拮抗细菌.两拮抗菌株定殖的研究结果表明,JK-SH007、JK-SX001对杨树腐烂病病原菌的生长及孢子萌发具有较好的抑制作用,而对宿主无毒害作用,具有内生性,能在杨树体内较长期定殖,且对宿主具有显著的促生作用.     

植物花色素合成的转录调控研究进展

花色素是由植物类黄酮代谢途径产生的次生代谢产物,决定了花、果实和种子的颜色。随着类黄酮代谢途径的研究不断地深入,多种植物编码合成花色素的结构基因也已得到克隆,并研究证明花色素合成结构基因与转录因子(MYB、 bHLH和WD40)有着极其复杂的相互作用模式。本文主要对花青素合成相关的MYB、bHLH和WD40转录因子及其在调节结构基因表达和花青素合成中的作用进行了综述。     

东乡野生稻原生境土壤微生物群落结构研究

以普通水稻为对照,以基于16S rDNA基因以及功能基因的高通量测序技术为手段,比较分析了栽培稻田土与东乡野生稻原生境土壤中微生物群落结构差异,并利用RDA分析探讨了环境因子与细菌群落结构的关系。结果表明:在氮磷钾营养物质、土壤细菌多样性和固氮菌多样性上,东乡野生稻原生境土壤均高于栽培稻土壤。东乡野生稻原生境土壤中细菌优势门为变形菌门、放线菌门和绿弯菌门。栽培稻土壤中优势门为变形菌门(Proteobacteria)、放线菌门、绿弯菌门和酸杆菌门。东乡野生稻土壤中固氮菌的优势属为慢生根瘤菌、Pseudacidovorax和固氮螺菌属,而栽培稻的优势属为慢生根瘤菌、甲基球菌属和红长命菌属。由RDA分析可知,碱解氮、速效磷和速效钾是影响土壤细菌群落结构的主要影响因子,碱解氮、速效磷和全氮是影响土壤固氮菌细菌群落结构的主要影响因子。     

病原菌毒素对植物的致病作用

病原菌在侵染植物的过程中产生的毒素一向被认为是致病的重要因子，然而对毒素致病作用的确定却是一个复杂的问题，毒素在一般生物测定中表现出来的对植物组织的伤害与破坏作用并不一定代表其具备致病力的密切相关，但是对于具体毒素在相应病种中的作用程度及对致病力的贡献大小还需要一些更严格的试验予以确定。     

大兴安岭4种杜鹃花科植物的DSE真菌分布

深色有隔内生真菌在寒温带地区的研究在国内还属空白。本研究首次对内蒙古大兴安岭兴安落叶松林下笃斯越橘、越橘、杜鹃和杜香的DSE真菌进行了研究。结果表明,这4种杜鹃花科植物都有DSE真菌定殖,但DSE定殖率都小于10%。DSE菌根定殖率与全氮呈极显著负相关。依据菌落形态特征和菌丝体的显微结构特征将这4种植物的根样中分离得到的187个DSE菌株分为15个菌株类型,并对这4种植物进行回接实验,其中有8种DSE菌株类型可以定殖这4种植物,8个菌株类型属于子囊菌门的Phialocephala属,分属4个种。     

荧光假单胞菌的溶磷机制及其在杨树菌根际的定殖动态

【目的】探究荧光假单胞菌菌株JW-JS1的溶磷能力及其在杨树根际和菌根际的定殖动态,揭示菌株的溶磷机制并进一步阐明溶磷细菌与外生菌根真菌的互作机制,为杨树专用复合菌剂的开发与应用提供理论依据。【方法】通过液体培养试验分析荧光假单胞菌菌株JW-JS1培养液可溶性磷含量、p H和可滴定酸含量的变化,采用高效液相色谱(HPLC)法测定有机酸种类和含量,利用抗利福平标记法筛选稳定的标记菌株,运用灌根法研究其在杨树根际和菌根际的定殖动态。【结果】1) JW-JS1菌株培养液可溶性磷含量随接种时间延长逐渐增加,培养液pH与可溶性磷含量呈极显著负相关(r=-0.889~(**)),可滴定酸含量与可溶性磷含量呈极显著正相关(r=0.958~(**));2) JW-JS1菌株分泌的总有机酸量(434.39 mg·L~(-1))明显高于CK (25.94 mg·L~(-1))(P0.05),共检测出草酸、酒石酸、柠檬酸、顺丁烯二酸和反丁烯二酸5种有机酸,其中,草酸含量(273.69 mg·L~(-1))明显高于其他种类有机酸,约占总有机酸量的63.01%;3)筛选出含有300μg·mL~(-1)利福平抗性的标记菌株JW-JS1~(Rif),与原始菌株相比,其菌落形态和溶磷能力均未发生明显变化(P0.05);4)标记菌株在杨树根际和菌根际均能长期稳定存活并保持一定的定殖数量,随接种时间延长定殖数量呈下降趋势,定殖动态基本一致,其中,接种50天后定殖数量分别为5.2×10~4和4.5×10~4cfu·g~(-1)。【结论】荧光假单胞菌菌株JW-JS1的溶磷能力与培养液pH、可滴定酸含量和有机酸密切相关,特别是菌株分泌的草酸可能在溶磷过程中发挥重要作用。荧光假单胞菌菌株JW-JS1在杨树根际和菌根际均能长期稳定存活并保持一定的定殖数量。荧光假单胞菌菌株JW-JS1与红绒盖牛肝菌Xc是构建杨树专用功能复合微生物肥料的理想材料。     

植物耐盐机理与耐盐植物选育研究进展*

文中结合对植物耐盐生理基础的讨论，综述了耐盐植物，尤其是耐盐树木的选育研究进展。植物对盐分胁迫的反应和适应是一个复杂的生理过程，既有蛋白质、核酸、碳水化合物等结构和能量物质的代谢，还有酶、激素等生长调节物质的合成与激话。在这一系列的反应过程中包含着离子交换与逆向运输，信号刺激与传递．基因活化与合成，其中渗透调节起着关键作用；在渗透调节过程中，离子如K^ 、Ca^2 等在浓度和时空上的变化对渗透调节的启动，调节速率和调节能力都有着重要作用。此外，脯氨酸、脯氨酸甜菜碱、甘氨酸甜菜碱等作为可配伍溶质在调节渗透势变化、整合盐分离子方面有着无可代替的作用。Ca^2 |作为第二信使的一个重要组成部分．在胁迫信号传递方面的功能正受到日益重视。激素如ABA在渗透调节和胁迫基因的诱导方面发挥了重要作用。胁迫基因目前主要是指渗透调节基因。首先在细菌中被发现，后来在高等植物中也相继分离克隆出来。有许多不同的方法用来选育耐盐植物，包括选、引、育等常规育种方法和基因工程，突变体育种等生物工程方法。它们各有特点．都发挥了各自的作用。对植物耐盐机理有限的认识以及高等植物结构与功能的高度复杂性制约着耐盐植物选育工作的进展。     

青枯假单胞杆菌对木麻黄致病机理的初步研究

通过用病原菌悬浮液及培养滤液等对木麻黄无根苗和有根苗进行接种处理，发现青枯菌ＰｓｅｕｄｏｍｏｎａｓｓｏｌｏｎａｃｅａｒｕｍＥ．Ｆ．Ｓｍｉｔｈ培养滤液对木麻黄具有强烈的致萎作用。小苗枯萎主要是由滤液中毒性物质诱导植物产生填充体堵塞导管所致。细菌培养滤液中毒性物质对热稳定，在ｐＨ４～１０的范围内毒性不受影响，而且能够致萎多种针阔叶树种小枝，具有非特异性     

松材线虫病致病机理的研究进展

该文对松材线虫病的致病机制的研究进行了概述。目前对松材线虫病的病原有两种看法，一种认为松材线虫是惟一病原，另一种认为病原为松材线虫和细菌两种生物。对于松材线虫的致病机理，目前存在3种观点。第1种观点认为松材线虫的酶使松树薄壁细胞的细胞壁和细胞膜遭到破坏，树脂不正常地从树脂道中渗漏并扩散到相邻的管胞中，使水分输导受阻，导致萎蔫。第2种观点认为松树感染了松材线虫后，木质部内挥发性萜烯类物质的含量增加，这些物质进入管胞在管胞中形成空洞，致使水分输导受阻。第3种观点认为松树感染松材线虫后，体内产生有毒物质，这些物质使松树萎蔫。     

Physiological responses of Eucalyptus spp. hybrids to infection by Ceratocystis fimbriata

In Brazil, the selection and planting of eucalyptus clones resistant to Ceratocystis fimbriata is the pre‐eminent control strategy for the wilt pathogen. However, little is known about host defence responses associated with resistance of eucalyptus to C. fimbriata infection. In this work, enzymatic activity, sugars, lignin, total phenols and phenolic compounds involved in the defence response of eucalyptus clones resistant (RC) and susceptible (SC) to the Ceratocystis wilt were evaluated. Changes were detected in the sugars produced by RC clones, with higher concentrations occurring compared with SC. A similar response occurred with lignin content at 28 days after inoculation (dai) in RC plants. SC plants had an increase in polyphenol oxidase and peroxidase activities at 7 dai. In contrast, RC plants demonstrated high activity of the same enzymes at 2 and 4 dai, decreasing afterwards. There was no difference in phenylalanine ammonia‐lyase activity between resistant and susceptible clones. Hydroxycinnamic acid concentration was higher in RC than in SC; however, there was no difference between RC and SC in flavonoid concentrations. RC had high concentrations catechin, chlorogenic acid and caffeic acid. Histochemical tests demonstrated the presence of phenolic compounds and lignin, at higher intensities, in xylem of RC plants. Inoculation with C. fimbriata induced defence responses in both resistant and susceptible eucalyptus clones, but both the intensity and speed of the responses were higher in RC. Alterations in the concentrations of sugars and lignin, as well as certain enzymes and phenolic compounds, could be used to predict the relative susceptibilities to Ceratocystis wilt of different phenotypes of eucalyptus clones.     

Impact of laurel wilt,caused by Raffaelea lauricola,on xylem function in avocado,Persea americana

Laurel wilt, caused by Raffaelea lauricola, is a lethal, vascular disease of avocado, Persea americana. Its impact on xylem function was examined in artificially inoculated plants of the ‘Simmonds’ cultivar. Three, 7, 14, 21 and 42 days after inoculation (dai), plants were rated externally and internally for disease severity on a subjective one (asymptomatic) to 10 (dead or 100% symptomatic) scale. Stems were then cut under water, 15 cm below the inoculation point, and placed in 0.1% aqueous solutions of acid fuschin in a greenhouse. After 48 h, the percentage of functional xylem was estimated 10 and 5 cm above and below the inoculation point by quantifying acid fuschin‐stained portions of digitized stem cross‐sections. Hydraulic conductivity was determined by placing the proximal end of 5‐cm‐long stem sections, harvested between 5 and 10 cm above the inoculation point, in water and quantifying the volume of water that was drawn over time through the distal end under partial pressure (350 mm Hg). Functional xylem decreased by 3 dai, well before the development of vascular discoloration (7 dai) and wilting of foliage (14 dai). By 14 dai, extensive vascular discoloration had developed and there was a dramatic reduction in functional xylem; plants with internal disease severities of 7 or greater had <20% functional xylem. Hydraulic conductivity decreased exponentially as non‐functional xylem and disease severity increased. In plants with internal severities >7, mean flow rates of water were 0.07 ml^?1 min^?1 cm^?2vs. 42 ml^?1 min^?1 cm^?2 in mock‐inoculated plants. The rapid development of these changes suggests that it may be difficult to manage laurel wilt in avocado once plants are infected by R. lauricola. Better understanding of the temporal and spatial development of infection and how the host responds to infection may assist efforts to select laurel wilt‐tolerant avocado cultivars.     

Responses ofQuercus sapwood to infection with the pathogenic fungus of a new wilt disease vectored by the ambrosia beetlePlatypus quercivorus

Quercus serrata andQ. crispula wilt during the summer in wide areas along the Sea of Japan. Mass attacks of trees by an ambrosia beetle (Platypus quercivorus) are characteristic before appearance of the wilting symptoms. This study investigated the pathogenic effects of a fungus detected specifically in the wilting trees. This hyphomycete fungus,Raffaelea sp., has a distribution that correlates with the discolored xylem area called wound heartwood in which vessels are dysfunctional. Tylosis formation around the hyphae indicates vessel dysfunction. In areas with discoloration, the fungal hyphae were invading living ray parenchyma cells from the vessel lumen. As a protective reaction the ray cells exuded yellow substances into the vessels, but these substances seemed ineffective against the fungal activity, probably because the fungus disperses along the beetle's gallery before enough substance can accumulate. It should allow wide discoloration in sapwood. Cambium was not necrotic around the fungus. The cytological process in the host was as follows: (1) synthesis of secondary metabolites by the stimuli of oak fungus; (2) exudation of yellow substances into vessels; and (3) dysfunction of vessels and wound heartwood formation. In regard to wilting of trees, the pathogenicity of the fungus should be assessed by its ability to stop sap flow.     

Research Advances in Interplay of Bursaphelenchus xylophilus and Other Key Biological Factors Related to Pine Wilt Disease

Pine wilt disease is fatal to pine trees, which has become the most dangerous biological disaster in forest historically (Chai Ximin et al. 2003; Yang Baojun et al. 2003; Zhang Xingyao et al. 2003). The outbreak and epidemic of pine wilt disease relate closely to host trees, insect vector and symbiotic microorganisms, and its pathogenic mechanism is not clear so far (Tominaga et al. 1984; Ishikawa et al. 1986; Shuto et al. 1987; Stamps et al. 1998a; Cheng yuexin et al. 2005; Tan Jiajin et …     

青枯菌对桉树及非寄主树木根部吸附和侵入的比较

通过接种青枯菌与非病原的大肠杆菌,对2个桉树无性系和1种非寄主树木的根表吸附菌量及根内含菌量进行测定.结果表明:青枯菌对感病寄主根表的吸附量多于对抗病寄主和非寄主根表的吸附量,对感病寄主根部的侵入量多于对抗病寄主但少于对非寄主根部的侵入量;病原菌较非病原菌对感病寄主根表的吸附量大,但二者对感病寄主根部的侵入量则依据根部伤口的有无而互有高低.青枯菌接种24 h内,感病寄主根表吸附菌量和根内含菌量呈上升趋势,在抗病寄主及非寄主根表的吸附菌量和根内含菌量却呈下降趋势.从统计学上看,青枯菌对寄主根部的吸附和侵入都显示出了一定的选择性,但由于病原细菌能够大量地吸附和侵入抗病寄主和非寄主根部,非病原细菌也能够大量地吸附和侵入桉树根部,因此这种选择性的生物学意义不大,青枯菌对桉树根表没有表现出明显的识别行为.     

防治松萎蔫病的新策略及林间防效初报

在松萎蔫病是由松材线虫与其携带的致病细菌诱导的一种复合侵染病害的新学说的指导下,根据松萎蔫病在疫区病树呈聚集分布,提出了防治松萎蔫病的新策略,即利用我们研究开发防治松萎蔫病的新药剂α-三噻吩与杀细菌剂恶喹酸对在以病死树中心周围半径50 m的范围内所有寄主树进行注干处理。经过2010—2011年在面积近20 hm2的处理黑松林地的防治试验,至2011年12月已经取得了良好的防效。处理林地中没有再发生病死树,对照区内却有24株病死树。防治仍在继续,新结果将继续报道。     

Mechanism of cavitation development in the pine wilt disease

Volatile terpenes increase in xylem tissue after infection of Pinus thunbergii with the pine wood nematode (Bursaphelenchus xylophilus). The role of these terpenes in traeheid cavitation, which blocks xylem-sap ascent and leads to water deficit in pine trees, was assessed. Volatile terpene concentration increased long before initiation of tracheid cavitation. After the volatile terpenes reached the highest concentration, severe cavitation developed. Direct injection of α-pinene into healthy pine trunks formed artificial cavitation in xylem. These observations support the hypothesis that excessively produced volatiles, which are hydrophobic and have lower surface tension than water can promote tracheid cavitation in pine wilt disease.     

Xyleborus glabratus attacks and systemic colonization by Raffaelea lauricola associated with dieback of Cinnamomum camphora in the southeastern United States

Laurel wilt, caused by Raffaelea lauricola, is responsible for extensive mortality of redbay and other American members of the Lauraceae in the southeastern United States. Raffaelea lauricola is a mycangial symbiont of the redbay ambrosia beetle (Xyleborus glabratus), and the beetle and fungus were accidentally introduced from Asia. Branch dieback of camphortree (Cinnamomum camphora), an Asian member of the Lauraceae, has been occasionally observed in areas where laurel wilt has decimated redbay populations, and R. lauricola was isolated from such camphortrees. However, the role of X. glabratus and R. lauricola in this branch dieback remains unclear. Examination of camphortrees on Jekyll Island, Georgia showed that healthy‐appearing trees and those with branch dieback had been attacked by X. glabratus, but the trees with branch dieback had four times as many beetle attacks. Raffaelea lauricola was routinely isolated from discoloured xylem near beetle tunnels in healthy trees and those with dieback. Single‐point inoculations with R. lauricola on stems of mature, healthy camphortree trees failed to induce wilt‐like symptoms or branch dieback, although areas of discoloration were scattered throughout the xylem, and R. lauricola was reisolated irregularly at various heights in some inoculated trees. In growth chamber experiments, single‐point inoculations with R. lauricola resulted in systemic colonization but no wilt symptoms or branch dieback in camphortree saplings. In contrast, inoculations at multiple points along the stem (simulating multiple attacks by the vector) caused branch dieback and wilt‐like symptoms, including a brownish, diffuse discoloration of the xylem. Camphortree appears to be more resistant than American species of Lauraceae to the vascular wilt caused by R. lauricola. The fungus does colonize camphortrees systemically, however, and can apparently cause branch dieback. This suggests that the fungus may provide brood material for X. glabratus in Asia as it does in the southeastern United States.