云南水稻白叶枯菌的RAPD分析

选取云南水稻白叶枯病菌优势小种的代表菌株41个,利用从258个RAPD随机引物中筛选出多态性好的24条引物对其DNA进行多态性分析.指纹图谱和聚类分析结果表明,各优势小种间遗传差异较大,菌株间具有明显的遗传多态性,在不同的相似水平下可分为不同的遗传组群.水稻白叶枯病菌优势小种间在分子水平上存在明显差异,且遗传组群与小种间有对应关系,遗传距离为0.2时可以将41个水稻白叶枯代表菌株分为10个遗传相似组,其中第2、8、10组为主要组群,第2组包括14个菌株,主要为7号小种;第8组有9个菌株,全部为8号小种.     

Integration of Pseudomonas fluorescens and acibenzolar-S-methyl to control bacterial spot disease of tomato

Xanthomonas axonopodis pv. vesicatoria was isolated from infected tomato seedlings grown in an open field in Egypt. All the tested isolates infected tomato plants but with different degrees of disease severity. In an attempt to manage this disease, tomato seeds and/or seedlings were treated with an antagonistic local isolate of Pseudomonas fluorescens as a suspension or its formulation or acibenzolar-S-methyl (BTH). When the above three treatments were applied to tomato seeds under laboratory conditions, they improved seed germination and seedlings vigour relative to control seeds treated with sterile distilled water and pathogen but P. fluorescens culture was the most effective. Under greenhouse and field conditions, combinations of the above treatments were used. All treatments significantly reduced disease severity of bacterial spot in tomato relative to the infected control. The biggest disease reduction compared to seedlings inoculated with the pathogen alone resulted from a foliar application of P. fluorescens. Combined application of P. fluorescens or its formulation with BTH reduced the pathogen population and increased seedling biomass and tomato yield relative to control seedlings.     

不同诱导处理后水稻悬浮细胞的活性氧变化与有关酶系的关系

以水稻（Oryza sativa L.）感病品种浙福802为材料,研究了3种不同因子处理后其悬浮细胞中活性氧及其一些抗病酶系的变化情况。结果表明：(1) 3种因子均能导致H2O2的形成和积累。XOO.75-1处理后的H2O2含量分别在0.5和6 h出现突增现象,而XOO.76-25处理只在0.5～1 h达到一个峰值。推测XOO.75-1和浙辐802间的互作属于非亲和性互     

柠檬叶片溃疡病菌的分离鉴定及室内防治药剂筛选

为了明确湛江地区柑橘溃疡病的病原类型并筛选出高效的防治药剂。以柠檬病叶为材料,用组织分离法对病样进行病原菌分离鉴定后,通过抑菌圈法测定了5种常用药剂对该病原菌的室内毒力。典型菌株zlm1908在NA培养基上菌落呈蜡黄色,圆形,全缘,有光泽,微隆起,黏稠,回接健康柠檬叶片后能产生明显的溃疡病斑,结合生理生化反应特点和特异性引物扩增序列分析确定菌株zlm1908为柑橘黄单胞柑橘亚种(Xanthomonas citri subsp.citri,Xcc)。5种药剂对菌株zlm1908的EC₅₀值分别为18.45 g/L、14.99 g/L、5.28 g/L、14.60 g/L和32.81 g/L。从EC₅₀的大小可以看出5种杀菌剂中枯草芽孢杆菌的抑制作用最强,其次为中生菌素,碱式硫酸铜和氢氧化铜,氯溴异氰尿酸抑制作用最弱。     

贝莱斯芽胞杆菌HN-2发酵上清液抑制三种黄单胞菌的生物活性研究

贝莱斯芽胞杆菌Bacillus velezensis HN-2为本实验室从土壤中分离得到的一株生防菌，本文研究了菌株HN-2发酵上清液活性成分的最优提取方式、抑菌效果及其活性成分的稳定性。结果表明，通过不同方式提取的菌株HN-2发酵上清液活性成分对3种黄单胞菌均有良好的抑菌活性。其中正丁醇提取物对水稻细菌性条斑病菌Xanthomonas oryzae pv. oryzicola的抑菌效果最好，抑菌圈大小为（41.57±0.33）mm；并且在10 mg/mL浓度下，贝莱斯芽胞杆菌HN-2正丁醇提取物比杆菌肽、春雷霉素和叶枯唑具有更好的抑菌效果。稳定性试验结果表明，贝莱斯芽胞杆菌HN-2正丁醇提取物对pH有较宽的适应范围（pH 1.0～9.0），且在紫外线及高温等环境下仍具有较好的稳定性。综上所述，贝莱斯芽胞杆菌HN-2正丁醇提取物具有开发成为生物源农药的潜力。     

柑橘溃疡病菌的药剂筛选及抗药性分析

柑橘溃疡病是柑橘生产上重要细菌病害,药剂防治是其主要的防治措施.本文通过平板抑菌圈试验,测定了来自广东和江西等地的21个柑橘溃疡病细菌对8种化学药剂的敏感性.结果表明:叶枯唑1 000×、新植霉素2 800×、水合霉素1 300×等3种药剂对供试的21个柑橘溃疡病菌菌株均没有抑菌作用;链霉素、中生菌素、溃疡克星、氢氧化铜.锌和必备等5种药剂对溃疡病菌表现不同程度的抑菌作用,其中,链霉素的抑菌作用最强;部分溃疡病菌株对这5种药剂产生了不同程度的抗药性.田间试验结果表明,链霉素、中生菌素对溃疡病防治效果较好.     

3种常用杀菌剂对不同来源木薯细菌性萎蔫病菌的毒力测定

细菌性萎蔫病是世界范围内木薯种植中的重要病害，但防控技术研究较少。采用含毒介质法评价了3种常用杀菌剂对不同来源的29个病菌菌株的抑菌作用。结果表明，供试菌株对净刹(80%乙蒜素EC)和农用硫酸链霉素(72%硫酸链霉素SP)敏感性较高，而对可杀得贰仟(53.8%氢氧化铜WG)表现出不同程度的抗性。建议生产中使用乙蒜素和硫酸链霉素对该病进行防治。     

水稻白叶枯病黄单胞菌rpfF基因的定位及其在致病调控中的作用

检测到水稻白叶枯病菌能产生一种“跨菌调控因子”，在固体平板上，这种因子由白叶枯病菌分泌到细胞外后可以扩散并进入甘蓝黑腐病菌，调控甘蓝黑腐病菌致病因子的表达．本研究从水稻白叶枯病菌中克隆鉴定了一个与这种“跨菌”调控因子合成有关的基因ｒｐｆＦ，通过转座子诱变和标记置换（ｍａｒｋｅｒｅｘｃｈａｎｇｅ）技术，构建了ｒＰｆＦ突变体，突变体丧失了产生这种“跨菌”调控因子的能力，在水稻植株上的致病能力明显减弱，ＤＮＡ序列分析得知ｒｐｆＦ基因编码的产物和大肠杆菌的３－酮脂酰－ＣＯＡ硫解酶（３－ｋｅｔｏａｃｙｌ－ＣＯＡｔｈｉｏｌａｓｅ）同源。     

柑橘溃疡病菌单链二硫键稳定重组抗体的构建、表达和特性

柑橘溃疡病(citrus bacterial canker disease,CBCD)是危害柑橘(Citrus reticulata Blanco)的重要病害,为了给柑橘溃疡病的现场快速诊断提供一种稳定的重组抗体,构建一种快速检测技术,本研究以鼠源抗柑橘溃疡病菌(Xanthomonas axonopodis pv.citri,Xac)表面脂多糖的二硫键稳定性抗体dsFv为模板进行基因改造,利用重叠延伸PCR在其重链可变区(VH)和轻链可变区(VL)之间引入一条人类抗体重链恒定区1(CH1)5'端12个氨基酸的序列作为连接肽,构建重组单链二硫键稳定抗体基因sc-dsFv。将获得的基因连接pET24a(+)载体,转入大肠杆菌(Escherichia coli)BL21(DE3)得到工程菌,IPTG诱导表达。表达产物经体外复性并以Ni-NTA亲和层析对目标蛋白sc-dsFv进行纯化,利用斑点免疫杂交、ELISA和BIAcore检测抗体的活性、稳定性、特异性及亲和力。构建的抗体基因经测序结果表明,抗体重链可变区(VH)和轻链可变区(VL)基因之间成功引入目标连接肽序列,重组sc-dsFv蛋白实现了原核高效表达;通过体...     

Isolation and Sequence of a Gene, celD Xo Involved in Cellobiose Utilization in Xanthomonas oryzae pv. oryzae

A genomic library of Xanthomonas oryzae pv. oryzae (X. o. pv. oryzae) T7174 was screened for 4-methylumbelliferyl β-D-glucoside-hydrolyzing (MUGase) activity. In subcloning of one of the MUGase-positive clones, an approximately 4.2-kb SacI-SphI fragment conferred not only MUGase activity but also 4-methylumbelliferyl β-D-cellobioside-hydrolyzing (MUCase) activity. Sequence analysis showed that the fragment contained an ORF of 2951 bp. The conceptual ORF product was significantly homologous with 1,4-β-D-glucan glucohydrolase D (CELD) from Pseudomonas fluorescens subsp. cellulosa, and was named CELD_Xo. Cell fractionation experiments suggested that CELD_Xo is localized in the cell-envelope fraction. We constructed a CELD_Xo-deficient mutant (74ΔCELD) from X. o. pv. oryzae. Little MUCase activity was detected in the cell-envelope fraction prepared from the mutant. The mutant 74ΔCELD did not grow in synthetic medium containing cellobiose as the sole sugar source. On the other hand, growth in rice leaves and pathogenicity of the mutant and the parental strain did not differ. These results suggested that CELD_Xo is involved in cellobiose utilization of X. o. pv. oryzae but that the gene is not required for bacterial growth in rice leaves. Received 16 February 2001/ Accepted in revised form 11 April 2001