青枯菌胞外酶对木麻黄的致病作用研究

对三个致病性不同的木麻黄青枯菌Ｐｓｅｕｄｏｍｏｎａｓ ｓｏｌａｎａｃｅａｒｕｍ Ｅ．Ｆ．Ｓｍｉｔｈ产生的胞外酶活性测定显示,聚半乳糖醛酸酶（果胶酶）在活性在各菌之间无明显差别,但纤维素酶活性差别明显,并随菌株的致病性上升而增加,菌株致病性与酶活性具有高度正相关。     

木麻黄青枯菌的致病性与其对寄主根表吸附的关系研究

对３个不同致病性的青枯菌菌株接种于７个不同抗性的木麻黄无性系上的研究表明：各菌株间对无性系根表吸附量达显著差异，而无性系间对同一菌株的吸附量差异不显著；根表吸附量与菌株的致病性呈负相关；说明青枯菌对木麻黄根表的吸附，就是两者的识别过程，而识别程度不同，则体现在吸附量的大小上，但是单从吸附量所反映的青枯菌致病性，难以确定出其对苗木最终的感病程度。     

青枯假单胞杆菌对木麻黄致病机理的初步研究

通过用病原悬浮液及培养滤液等对木麻黄元根苗和有根苗进行接种处理，发现青枯菌Ｐｓｅｕｄｏｍｏｎａｓ ｓｏｌｏｎａｃｅｚａｒｕｍ Ｅ．Ｆ．Ｓｍｉｔｈ培养滤波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民管所致细菌培养滤液中毒性物质对热稳定，在ｐＨ－４－１０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，个有非特异性。     

木麻黄无性系对青枯菌抗性及菌株变异初探

用３个青枯菌菌株，对７个木麻黄无性系作接种测试和菌株兔血清双向琼脂扩散试验，结果表明：木麻黄无性系对青枯菌的抗性以水平抗性为主，也存在垂直抗性；３个菌株致病力顺序与其来源无性系的抗病力顺序相一致，菌株对来源无性系接种死亡率显著高于其它菌株，显示了寄主与病原物相关变异的迹象。从同一地点不同无性系分离的菌株，存在抗原──抗体差异，表明在高抗无性系的选择压力下，青枯菌可能发生变异，而形成能克服特定抗病无性系的菌株。     

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     

木麻黄青枯菌的根表吸附及根内增殖与其致病性关系

对 3个不同致病的青枯菌菌株和 7个不同抗病性的木麻黄无性系苗的研究得出 ,各菌株对寄主根表吸附量具有显著差异 ,吸附量与致病性呈负相关 :各菌株在寄主根内的增殖量差别明显 ,增殖量与致病性呈正相关。病菌脂多糖 (LPS)对幼苗根的预处理 ,可使其供体菌的吸附量减少5 8.5 %　 97.3% ,但胞外多糖 (EPS)对供体菌的吸附量无明显影响。洗去EPS和LPS的菌体较完整菌体对根表的吸附量减少 6 3.3%　 74 .2 %。而仅洗去EPS的菌体对根表的吸附有所增加 ,最高达19.1%。各菌体SDS PAGE电泳图谱显示出一定差异 ,其中强毒菌株 6 0 1B具有Rf=0 .35的特异谱带。结果表明青枯菌对木麻黄的致病性与其在寄主根表的吸附情况和在根内的快速增殖具有密切关系。LPS在此病理系统中 ,起着细菌识别因子的作用 ,EPS对LPS进行掩盖 ,二者都是病菌致病性的重要因子     

木麻黄根瘤内生菌——弗兰克氏菌对青枯病菌的抑制作用研究

试验结果揭示了木麻黄弗兰克氏菌和木麻黄根瘤浸提液能抑制青枯菌生长,弗兰克氏菌Ｏｒ９３０２和９０２１菌株的抑菌效果比其它供试菌株高;粗枝木麻黄的根瘤浸提液抑菌效果较山地木麻黄和普通木麻黄的抑菌效果好。苗圃试验表明根瘤量高的苗木对青枯病具有较强的抵抗能力。     

大孔吸附树脂纯化木麻黄总黄酮及对青枯菌的抑制

为探索获得较为纯化的木麻黄总黄酮的便捷有效方法,研究了利用大孔吸附树脂分离纯化木麻黄总黄酮的工艺。结果表明:选择D101大孔吸附树脂的最佳工艺条件为吸附液料比20∶1(黄酮粗提液∶大孔吸附树脂,mL.g-1);吸附液pH为2;解吸液pH为11;最佳静置吸附时间为90 min;乙醇洗脱体积分数为80%;洗脱液料比为20∶1(80%乙醇溶液∶大孔吸附树脂,mL.g-1)。分离到的总黄酮对青枯菌具有明显的抑制作用。同时也证明了气质联用不适于鉴定黄酮类大分子物质。     

木麻黄对青枯菌的水平及垂直抗性研究

６个青枯假单胞杆菌菌株对７个木麻黄无性系的交互接种试验表明，病害的相对强度在无性系与菌株间存在着显著性差异，无性系与菌株之间的交互作用也极显著。结果说明在木麻黄－青枯菌病理系统中，同时存在着水平抗性和垂直抗性或水平致病性与垂直致病性；这一交互作用特征的揭示对于木麻黄的抗病育种及防滑战略具有重要意义。     

桉树对青枯病抗性与过氧化物酶及同工酶关系的研究

对７个具有不同青枯病抗性的桉树品系的叶部和根部的过氧化物酶活性进行了测定,对同工酶进行了电泳分析。酶活性测定结果表明,桉树各品系叶部的过氧化物酶活性显著高于根部。对青枯病具有不同抗性的７个桉树品系,其叶部的过氧化物酶活性存在着显著差异。对青枯病抗性较弱的Ｆ１１和Ｅ１３品系体内的过氧化物酶显著比其它抗性品系体内的酶活性低。同工酶电泳分析表明,桉树对青枯病不同抗病性品系之间的同工酶谱带,在条带数和各条     

青枯菌对植物的致病机制及其调节

青枯菌引起许多植物及林木青枯病。该菌侵染植物根部,首先在根皮层细胞间隙等处定殖,然后入侵维管束,在木质部导管内扩展危害;细菌在导管及相邻组织内迅猛增殖和广泛散布,由此产生输水管道的阻塞和破坏并最终导致植物枯萎。胞外多糖(EPSI)、细胞壁分解酶(主要是果胶质酶和纤维素酶)、Ⅲ型Hrp分泌系统产物是主要的致病因子,其中EPSI尤为突出,它在保护细菌、促进细菌移动和定殖以及堵塞和破坏寄主导管方面都起着重要作用。而上述致病因子的协调作用则由一复杂的调节系统控制,这一系统由随细菌密度变化而变化的3 -羟基棕榈酸甲基酯水平作为信号,以PhcA调节基因的启动和转录为核心,自动而精密地调节病菌有关致病基因的表达及关闭,并由此控制细菌的生长状态。     

我国植物青枯病抗病性研究新进展

文章综述了近年来我国植物抗青枯病的抗病鉴定方法、抗病机制、抗病遗传、抗病育种及诱导抗病性等的研究进展及成果；并提出了今后的研究方向。     

Susceptibility of Eucalyptus hybrid clones to Botryosphaeria canker in Uganda

ABSTRACT

The study assessed the susceptibility of the nine commonly grown Eucalyptus clones to Neofusicoccum species associated with Botryosphaeria canker in Uganda. The inoculation trials indicated that susceptibility of Eucalyptus hybrids differed significantly (p = .000), clones GU609, GU7, GC578, and GC796 exhibiting a higher tolerance than GC784, GC550, GU8, GC514, and GC540. The results further revealed that N. parvum was more pathogenic than N. kwambonambiense. The generated information can be exploited in sustainable forest management by expanding the growing of tolerant hybrids in areas with high Botryosphaeria canker disease pressure.     

New role for glyoxylate cycle enzymes in wood-rotting basidiomycetes in relation to biosynthesis of oxalic acid

The key enzymes of the glyoxylate cycle, isocitrate lyase (ICL) and malate synthase (MS), were detected in varying amounts in the mycelia of the woodrotting basidiomycetes tested, although they were grown in a glucose-rich medium. The highest specific activities of ICL (0.37 U/mg protein) and MS (0.63 U/mg protein) were measured for the brown-rot basidiomycetesLaetiporus sulphureus andFomitopsis palustris, respectively. The results indicate that the glyoxylate cycle enzymes occur in wood-rotting basidiomycetes as the seemingly constitutive enzymes at varying levels. The glyoxylate cycle enzymes, including malate dehydrogenase (MDH), and the oxalate-producing enzymes glyoxylate dehydrogenase (GDH) and oxaloacetase (OXA) were found to have good correlation with biosynthesis of oxalic acid and fungal growth, which was also confirmed by use of an ICL inhibitor. A new role for the glyoxylate cycle is discussed in relation to oxalic acid biosynthesis in wood-rotting basidiomycetes.This paper was presented in the 50th annual meeting of the Japan Wood Research Society, Kyoto, April 2000     

不同环境条件下气孔和光合作用模型: 4个杨树无性系对光照、温度和相对湿度的反应(英文)

用配有Ｌｉ－６１０露点发生器的Ｌｉ－ｃｏｒ６２００在温室中测定了４个杨树无性系叶水平上的气孔导度（Ｃｓ）和净光合速率（Ｐｎ）．在３个相对湿度（ＲＨ）水平（７０％，５０％和３０％）控制下，不同温度（２５℃，３０℃和３５℃）条件下，杨树无性系的Ｐｎ、Ｃｓ、蒸腾速率（Ｅ）和胞间ＣＯ２浓度（Ｃｉ）表现出显著差异（Ｐ＜０．０００１）．随着空气湿度的减小，Ｅ、Ｃｓ、Ｃｉ明显下降．结果表明：ＲＨ低时，而不是ＶＰＤ高时，气孔关闭在调节蒸腾速率和胞间ＣＯ２浓度中起更大作用．另外，还选用了净光合速率－光照模型和Ｃｓ－Ｐｎ复合模型模拟了不同光照、温度和相对湿度条件下Ｐｎ和Ｃｓ间的关系．尽管无性系、温度和湿度间存在差异，但在模拟Ｐｎ对光照的关系上净光合速率－光照模型最合适．关于Ｃｓ－Ｐｎ模型，检验了Ｌｅｕｎｉｎｇ模型，建立了新的Ｃｓ－Ｐｎ模型：Ｃｓ＝Ｃｓ０＋ａ０Ｐｎ／［（ＣＯ２－Γ）（１＋ｆ（Ｔ）（１－ＲＨ／１００）／Ｄ０）］．基于它们之间的关系，式中加入了反映温度和ＲＨ的变量，代替了ＶＰＤ变量．与田间数据模拟结果相比较，新模型和Ｌｅｕｎｉｎｇ模型一样适合．并且，为了预测气孔和气体交换的行为，可以用净光合速率－光照模型修正Ｃｓ－Ｐ     

The role of topkill in the differential response of savanna woody species to fire

Understanding the impact of fire on the demography of savanna trees and shrubs is necessary for understanding human impacts in tropical savannas. In a replicated experiment, we studied the impact of fire and vegetation cover on survival and growth of two subshrubs (Periandra mediterranea and Protium ovatum), two shrubs (Miconia albicans and Rourea induta) and three trees (Myrsine guianensis, Piptocarpha rotundifolia and Roupala montana) of the Brazilian cerrado savannas. Burning increased complete mortality (i.e. death of the individual) of five of the seven species, but primarily among individuals with stem diameters <4 mm. Stem mortality (i.e. topkill) was much more prevalent, primarily affecting individuals with stem diameter <32 mm, though all species experienced some topkill in even the largest size classes. Fires of higher intensity (flame length >2 m) caused greater mortality and topkill than fires of lower intensity (flame length <2 m). Pre-burn vegetation density had little effect on survival or resprout size, but did affect subsequent growth rates. Four species had greater growth rates in open sites, whereas only one species had greater growth rates in dense sites. For the three tree species and one shrub, resprouting individuals did not reach the minimum reproductive size within 1 year of burning, while the other shrub and the two subshrubs were able to reach reproductive size during this time, indicating that growth form largely determines the population response to frequent burning.     

The role of gaps and tree regeneration in the transition from dense to open black spruce stands

Black spruce forests growing on clay soils in northwestern Quebec change structure from dense even-aged stands to open uneven-aged stands such that almost all forests older than 200 years have an open canopy. These forests become unproductive over time because they are prone to paludification. The main goal of our study was to document the transition between dense and open stands in terms of gap dynamics, with a focus on tree regeneration. Our objective was to determine whether forests remain open due to a lack of regeneration, a lack of growth or both. Nine stands along a 50–250-year-old time since fire gradient were sampled with the line intersect sampling method. Gap fraction increased with stand age and reached a maximum of 77% in the oldest site. In old-growth stands, gaps were interconnected due to the low density of these forests. Most of the gap makers were found with broken stems. Regeneration was dominated by black spruce layers and was relatively abundant (1.71 stems/m²). However, the majority of gap fillers were smaller than 1 m in height in stands of all ages. Instead of a lack of regeneration, the opening of the forests is due to a lack of growth associated with cold and wet organic deposits. Partial harvesting could be implemented on the most productive sites, while management techniques including soil disturbances will be required on low productivity sites to recreate good growth conditions.