Response of black rot in cabbage to spatial distribution of inoculum

Disease progress of black rot in cabbage crop was studied over three years in field plots to compare the effects of uni-focal and multi-focal inoculum applied in equal amounts per plot. Disease progress (plant incidence and leaf incidence) was plotted over time, three dimensional maps were made, and disease aggregation was studied by means of geostatistics, black-black counts and Moran's I statistic. Black rot progress was primarily due to focus expansion. Secondary foci may appear at short distances from the initial focus but they usually merge with the expanding initial focus. Anisotropy occurred occasionally but was of minor importance. Disease proceeds faster in plots with multi-focal inoculation than in those with uni-focal inoculation. Probably, serious epidemics in Dutch cabbage fields originate from large numbers of foci.     

Molecular characterization of the incitant of cowpea bacterial blight and pustule, Xanthomonas campestris pv. vignicola

Strains of Xanthomonas campestris pv. vignicola (Xcv), isolated from cowpea leaves with blight or minute pustules and collected from various geographic areas, were selected on the basis of pathological and physiological features. All strains were analyzed for genotypic markers by two methods: ribotyping with EcoRI endonuclease, and RFLP analysis with a plasmid probe (pthB) containing a gene required for pathogenicity from Xanthomonas campestris pv. manihotis. Ribotyping revealed a unique pattern for all the strains that corresponded to the previously described ribotype rRNA7. Based on polymorphism detected by pthB among Xcv strains, nine haplotypes were defined. The observed genetic variation was independent of the geographic origin of the strains and of pathogenic variation. Some haplotypes were widely distributed, whereas others were localized. In some cases, we could differentiate strains isolated from blight symptoms and pustules according to haplotypic composition. However, in most cases, no significant differences were observed. Our results and the previous pathogenic and biochemical characterizations suggest that the strains isolated from leaves with blight symptoms or minute pustules belong to the same pathovar. We provide information on pathogen diversity that can be used to identify and characterize resistant germplasm.     

Leaf necrosis and twig dieback of sweet persimmon (Dyospiros kaki L.) caused by Pseudomonas syringae pv. syringae in Italy

In spring 1996, extensive leaf necrosis and twig dieback were observed on young sweet persimmon (Dyospiros kaki L.) trees, cultivars O'Gosho, Hachija, Mercatelli and Kaki-tipo planted in the Abruzzo region (central Italy). Many trees were killed. When the dieback reached the trunk, in many cases, new vegetation was noticed above the graft point. The cultivar Jiro-C was not affected by the disease. During 1997, no symptoms were observed on any plant. The orchard was planted in a clay soil with a very low content of organic matter. Biochemical, nutritional and pathogenicity tests indicated Pseudomonas syringae pv. syringae van Hall as the causal agent of the disease. This is the first report of this bacterium as a pathogen of sweet persimmon in Europe.     

杉木细菌性叶枯病的发生及防治措施

杉木细菌性叶枯病是杉木的主要病害之一,由丁香假单胞杆菌杉木致病变种(Pseudomonas syringae pv. cunning-hamiae)引起。本文综合阐述了其发病原因和发病规律,并针对其发病特点提出了综合防治措施。     

中国水稻主产区白叶枯病菌致病型分析及近等基因系鉴别寄主的构建

【目的】分析中国不同稻区白叶枯病菌（Xanthomonas oryzae pv. oryzae）致病型,建立近等基因系鉴别寄主,为白叶枯病菌群体结构田间实时准确监测、抗性品种应用以及抗病育种提供科学依据。【方法】利用中国鉴别寄主、IR24以及15个抗白叶枯病近等基因系等共21个鉴别寄主,采用人工剪叶接种方法,对2018—2021年采自广东、广西、海南、浙江、湖南、辽宁、云南共7个省（自治区）的954个单菌落分离菌株进行致病型测定,探明白叶枯病菌致病型种类、分布及毒性分化;基于测试菌株与15个近等基因系及IR24的抗感互作,应用主成分因子分析法,开展近等基因系与病菌互作的变量因子分析,构建白叶枯病菌致病型近等基因系鉴别寄主;基于抗病基因与测试菌株的抗感反应,分析抗病基因聚合效应。【结果】954个测试菌株在中国鉴别寄主上鉴定出11个致病型,包括SRRRR（I）、SSRRR（Ⅱ）、SSSRR（Ⅲ）、SSSSR（Ⅳ）、SSRRS（V）、SRSRR（Ⅵ）、SSSSS（Ⅸ）、SSSRS（新型1）、SRSRS（新型2）、SRSSS（新型3）以及SSRSS（新型4）,占测试菌株的比率分别为11.53％、4.82％、7.34％、6.18％、7.23％、1.05%、59.96％、1.57%、0.10%、0.10%、0.10%。Ⅸ型菌作为致病性最广的强毒菌系已上升为华南和长江中下游湖南和浙江稻区的优势致病型,西南稻区的云南以Ⅳ型菌为主,东北稻区的辽宁以I型菌为主。15个水稻抗白叶枯病近等基因系对954个菌株的抗感性分析结果表明,测试的15个近等基因系可分为5种类型,第Ⅰ类为高感基因系,包括IRBB1、IRBB2、IRBB10、IRBB11、IRBB4;第Ⅱ类为中感基因系,包括IRBB3、IRBB203、IRBB14;第Ⅲ类为中抗基因系,包括IRBB8、IRBB13;第Ⅳ类为抗病基因系,有IRBB21;第Ⅴ类为高抗基因系,包括IRBB5、IRBB7、CBB23、GDBB23;测试菌株中,出现可侵染抗病基因xa5的有42个、Xa7的有34个、Xa23的有31个。对以白叶枯病近等基因系为主的16个品种（系）与954个菌株组成的抗感互作变量数据矩阵进行因子分析,以解释总变量>85.0%为界,提取出8个主成分因子,组建了以近等基因系为主的10个品种(系)组成白叶枯病菌近等基因系鉴别寄主,按其对变量方差贡献大小,这些寄主分别为IRBB10（Xa10）、IRBB4（Xa4）、GDBB23（Xa23）、IRBB5（xa5）、IRBB7（Xa7）、IRBB21（Xa21）、IR24（Xa18）、IRBB13（xa13）、IRBB3（Xa3）、金刚30;新鉴别寄主可将954个测试菌株划分为55个致病型,对测试稻区的白叶枯病菌菌株表现出较好的鉴别力。基因聚合联合抗性分析表明,不同抗病基因聚合对病菌的抗性频率有一定的提升,不同抗病基因对测试菌株的抗性具有一定的互补性。【结论】监测稻区的白叶枯病菌系趋向多样化,毒性分化明显,强毒菌系Ⅸ型菌在部分稻区已上升为优势致病型,侵染xa5、Xa7及Xa23等广谱抗性基因的菌株有上升趋势;抗病基因聚合可拓宽品种对病原菌系的抗性谱,是培育广谱抗性品种的有效途径;近等基因系鉴别寄主的建立与应用可为白叶枯病发生流行的精准监测以及田间实时预警提供技术支撑。     

水稻OsNHO1基因cDNA序列分离及表达分析

OsNHO1是一种甘油激酶,受多种因素的诱导,在植物先天免疫反应中起着重要的作用。笔者采用同源序列法,根据已报道的拟南芥NHO1基因序列结合水稻基因组测序结果,筛选水稻OsNHO1基因,采用RT-PCR获得水稻OsNHO1基因全长cDNA(1 590 bp,529AA),并通过半定量RT-PCR方法分析OsNHO1基因在SA,PXO99刺激下的表达模式,结果显示OsNHO1基因的表达受SA,PXO99的诱导,为进一步研究OsNHO1的具体功能和作用机理奠定了基础。     

三七细菌性叶斑病病原菌鉴定

[目的]对引起三七细菌性叶宽病的病原菌进行系统鉴定。[方法]以2011及2012年在云南文山及石林县的三七苗圃采集的三七细菌性叶斑病病株为材料,采用柯赫氏法则,检测分离菌株致病性并重新分离得到病原菌。通过病菌形态观察、致病性测定、16SrD—NA序列分析及生理生化特性分析（Biolog系统）对其进行鉴定。[结果]确定三七细菌性叶斑病病原菌为丁香假单胞菌丁香致病变种（Pseudomonas syringae pv．syringae）。[结论]该研究为三七细菌性叶瘫病菌详细鉴定的国内首报。     

水稻白叶枯病菌转录调控因子OxyRxoo对细菌抗氧化系统的调控作用

病原细菌对活性氧的降解是抗氧化和侵染中的重要毒性机制之一。阐述了水稻白叶枯病菌（Xanthomonas oryzaepv.oryzae）的转录调控因子OxyRxoo在病菌抗氧化系统中的调控作用,以及目前对OxyRxoo的研究进展。     

李树叶片细菌性穿孔病的发生规律及防治研究

细菌性穿孔病可导致李树叶片大量脱落,树势衰弱,产量降低,品质下降.研究发现,病害的初侵染源来自枝干病斑,生长季节枝、叶、果互相交叉传染.种植感病品种、树势强旺、雨日多、雨量大为该病的流行因素.选用抗病品种、消除初侵染源、加强栽培管理、生长期用药控制是防治该病的有效措施.     

Resistance to common bacterial blight in Phaseolus vulgaris L. recombinant inbred lines under natural infection of Xanthomonas axonopodis pv. phaseoli

Among the main causes of poor yield in common beans are fungal, viral and bacterial diseases. Common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli (Xap), is one of the major bacterial diseases leading to significant losses in Brazil. Chemical control is ineffective, therefore, the use of resistant varieties becomes an interesting alternative. The objective of the present work was to evaluate disease resistance under natural infection of the pathogen in 109 recombinant inbred lines (F₇) of P. vulgaris originated from the cross HAB-52 (susceptible — snapbean) × BAC-6 (resistant — common bean) in two different environments, as well as to calculate genetic parameters to assist in the selection of promising materials to be used in the CBB resistance breeding program. The data of the genetic parameters were compared to those calculated for the F₃ generation originated from the same cross. The heritability results for DI (disease index) and VI (variation index) in F₃ were 26.85% and 0.26, respectively, whereas in F₇ they were 91.77% and 1.36, respectively. These results demonstrate a potential to be explored for this advanced population, that in the future, along with other pathogen variability studies and tests in other environments, may provide more information regarding a more precise evaluation of promising genotypes to be used in common bean breeding programs aiming to obtain CBB resistant varieties. This revised version was published online in July 2006 with corrections to the Cover Date.