观赏百合叶枯病症状类型与病原菌鉴定

引起甘肃省百合叶枯病的主要致病菌为椭圆葡萄孢[Botrytis elliptica(Berk.)Cooker],分离率为70.5%;其次是灰葡萄孢(Botrytis cinerea Peers),分离率为23.0%。该病原菌在不同品种百合叶片上造成的症状有4种类型。不同症状类型病斑分离的病原菌种类不同,其中紫缘黄褐斑型、褐色环纹型和黄缘褐斑型主要致病菌为椭圆葡萄孢,平均分离率为82.5%;叶缘干枯型的主要致病菌为灰葡萄孢,分离率达93.7%。温度为15℃时,易产生菌核;菌核萌发最适温度为15~20℃。     

水稻细菌性基腐病的侵染规律和病理解剖学研究

 水稻细菌性基腐病是近年来发现并日趋严重的水稻病害.经鉴定,病原菌的细菌学性状与菊欧氏杆菌玉米致病变种(Erwinia chrysanthemi PV.Zeal)相似。本文通过接种实验和扫描电镜观察,证明基腐病细菌可从叶片上的水孔、伤口、受伤的叶鞘和根系侵入,引起不同类型的症状,而以根系侵入为主.首次报导该病原菌侵入后主要在根、茎的气腔中作系统侵染.     

First report of bacterial blight of crucifers caused by Pseudomonas cannabina pv. alisalensis in Japan

In October 2010, a bacterial disease produced flecks and spots on leaves of Chinese cabbage, cabbage and Japanese radish in Nagano Prefecture, Japan. The symptoms started on the abaxial surface of leaves as angular, water-soaked flecks of 1–2 mm in diameter with a yellow halo of 3–4 mm width. These flecks then became visible on both leaf surfaces, enlarged and coalesced into large blight lesions. The symptoms were similar to bacterial leaf spot caused by Pseudomonas syringae pv. maculicola. The bacterium isolated from leaf lesions formed a white colony and produced polysaccharides on YP agar. The isolates were identified as P. syringae group by LOPAT tests and the 16S rDNA sequence. Moreover, the results of pathogenicity on cruciferous plants, bacteriological characteristics, rep-PCR and the sequences of rpoD and gyrB showed that the isolates should be identified as P. cannabina pv. alisalensis (recently transferred from P. syringae pv. alisalensis). This is the first report of P. cannabina pv. alisalensis isolated from diseased crucifers in Japan.     

<Emphasis Type="Italic">Clavibacter michiganensis</Emphasis> subsp. <Emphasis Type="Italic">michiganens</Emphasis>is strains virulence and genetic diversity. a first study in Argentina

Tomato leaves showing severe leaf spot symptoms have been observed and sampled in the central west and southwest Taiwan during 2015 and 2016. The symptoms were similar to those of bacterial leaf spot/late blight diseases, but only Stemphylium-like fungi were consistently isolated from the diseased tomato. Upon spray inoculation of tomato, Stemphylium-like isolates caused leaf spot symptoms identical to those of naturally infected plants, and the pathogenic isolates were successfully re-isolated from inoculated leaves. The tomato-pathogenic isolates were identified as S. lycopersici based on morphological characterization and molecular identification. S. lycopersici has been previously reported to cause gray leaf spot of tomato in the temperate regions, but the majority of S. lycopersici-caused lesions were black/dark brown rather than gray in our surveillance. Accordingly, it is suggested that S. lycopersici-caused disease of tomato is named Stemphylium leaf spot of tomato more appropriately than tomato gray leaf spot. Moreover, S. lycopersici-caused leaf spot disease on tomato has been distributed in major tomato production regions in Taiwan. The information provided by our study will be important for future breeding of tomato cultivars, especially for tomato producers in Taiwan.     

Bacterial soft rot of myoga (Zingiber mioga) caused by Erwinia chrysanthemi

In 2010, a bacterial soft rot was found on myoga [Zingiber mioga (Thunb.) Rosc.] in Japan. Initial small spots on flower buds rapidly enlarged while changing from light brown to brown. Diseased flower buds became completely rotten. Several bacteria isolated from the diseased tissues caused the same symptoms as those observed in the fields and were reisolated from the tissue. These bacteria were identified as Erwinia chrysanthemi and were classified into subdivision IV and biovar 3. This is the first report of bacterial soft rot of myoga in the world.     

加那利海枣叶斑病病原鉴定*

对加那利海枣叶斑病的症状进行了观察。结果表明,加那利海枣叶斑病主要发生在叶片和叶柄。初期症状是在叶片和叶柄出现水渍状褪绿色的褐色小点,病斑扩大成浅褐色椭圆形或不规则病斑,病斑周围有黄色的晕圈,后期变褐色至灰褐色,中央产生小黑点。按照柯赫氏法则对该病害的病原菌进行分离和致病性测定。通过形态学观察和rDNA ITS序列分析鉴定,将病原菌鉴定为异色拟盘多毛孢［Pestalotiopsis versicolor (Speg.) Steyaert］。     

Bacterial leaf blight of strawberry (Fragaria (x) ananassa) caused by a pathovar of Xanthomonas arboricola, not similar to Xanthomonas fragariae Kennedy & King. Description of the causal organism as Xanthomonas arboricola pv. fragariae (pv. nov., comb. nov.)

A new bacterial disease of strawberry is described. This disease, called bacterial leaf blight of strawberry, is characterized by dry, brown necrotic leaf spots and large brown V-shaped lesions along the leaf margin, midrib and major veins. Symptoms are different from angular leaf spot of strawberry caused by the bacterium Xanthomonas fragariae . Strains of the bacterial leaf blight pathogen were characterized in a polyphasic approach by biochemical tests, fatty acid analysis, protein electrophoresis, serology, PCR, pigment analysis, ice-nucleation activity, AFLP analysis, DNA:DNA hybridization, pathogenicity and host range tests, and compared with a number of reference strains of X. fragariae and other Xanthomonas species. Bacterial leaf blight strains formed a homogeneous group in all tests, completely different from X. fragariae . They were the only strains causing leaf blight of strawberry upon artificial inoculation into strawberry. Fatty acid and protein electrophoretic analysis showed that the strains belong to the phenon X. campestris ( sensu latu , including pathovars now classified as belonging to X. arboricola ). AFLP analysis and DNA:DNA hybridization further clarified their taxonomic position as belonging to X. arboricola. The name X. arboricola pv. fragariae is proposed for the bacterium causing leaf blight of strawberry with strain PD2780 (LMG 19145) as pathovar type strain. Criteria for routine identification are given and the taxonomic status is discussed.     

中华常春藤细菌性叶斑病病原菌的鉴定

 2015年春季在昆明市区绿化带种植的中华常春藤上发现一种由细菌侵染而引起的病害,称为中华常春藤细菌性叶斑病。通过发病症状、菌落形态观察、致病性测定、Biolog分析,16S rDNA序列和核糖体DNA内转录间隔区(internal trans-cribed spacer, ITS )序列分析比较,对昆明地区的常春藤叶斑病病原菌及其系统进化关系进行研究。分离病原菌接种中华常春藤叶片完成科赫法则验证,发病初期在叶片表面形成带有黄色叶晕的不规则褐色斑点,后期叶片边缘形成倒V字型坏死并起皱。将菌株CCT1和CCT6测序结果与现有的黄单胞菌菌株的16S rDNA序列和核糖体DNA的ITS序列构建进化树,结果均显示病原菌与野油菜黄单胞菌的序列相似度最大,属于同一支。研究确定该病原菌为野油菜黄单胞菌(Xanthomonas campestris)。这是中国首次报道由X. campestris 引起的中华常春藤叶斑病。     

湖南杂交水稻凋萎型白叶枯病的调查研究

 杂交水稻南优2号、南优3号近年来在湖南普遍发生枯心凋萎现象。病株除在秧苗后期至分蘖盛期呈现枯心、凋萎死亡和茎基有大量菌脓的突出症状外,拔节期后继续发病的稻株逐渐转为叶片受害,甚至在壮苞期引起死穗现象。此外,在调查中还发现少数常规品种偶有发生,但受害轻微。     

山茱萸褐斑病病原鉴定

 山茱萸(Cornus officinalis)为山茱萸科(Cornaceae)山茱萸属植物, 其成熟干燥果肉(俗称枣皮)为我国常用名贵中药材。河南省南阳市(西峡、内乡和南召等县)为我国山茱萸主产区之一, 仅西峡县截止1990年已发展到500万株, 年产枣皮315万kg, 产值达4 200万元, 居全国首位。近年, 作者对西峡县山茱萸产区进行病害调查时发现, 由链格孢菌(Alternaria sp.)引起的山茱萸褐斑病发生普遍, 该病严重发生时可致植株95%以上叶片枯死, 落果率高达87%, 造成山茱萸大幅减产, 给当地果农带来严重经济损失。迄今, 未见链格孢菌引起的山茱萸病害报道。本研究对该病的病原菌进行分离鉴定, 以期为病害的防控提供依据。     

广东南瓜细菌性叶枯病及其病原鉴定

 在广东省雷州市发生一种南瓜(Cucurbita moschata)叶枯病,病株叶片边缘开始出现水渍状病斑,逐步发展成大病斑,后期病斑焦枯;在叶片上也可形成近圆形水渍状病斑,伴有黄色晕圈,后期病斑联合形成不规则大枯斑;叶柄和匍匐茎被侵染后呈水渍状腐烂。从病斑上分离到一种细菌,在KB培养基上,菌落为椭圆形,乳白色,半透明,边缘参差不齐,紫外灯照射下产生荧光反应。致病性测定结果表明,该病原细菌可侵染6个南瓜品种引起与田间症状相同的叶枯病。生理生化试验结果表明,该病原细菌与丁香假单胞丁香致病变种(Pseudomonas syringae pv. syringae)的特性一致。应用假单胞菌属特异引物Ps-for/Ps-rev和丁香假单胞丁香致病变种组群特异性引物Group III-F/Group III-R,可从该病原细菌中扩增出预期大小分别为1 018 bp和750 bp的目的片段。应用丁香致病变种syrB基因特异性引物B1/B2,可从该病原菌中扩增出预期大小为750 bp的丁香霉素基因片段。基于16S rDNA与gyrB基因序列系统进化分析均表明,南瓜叶枯病菌株与已报道的P. syringae pv. syringae菌株HS191(CP006256)亲缘关系最近,二者聚类在一起形成一个小分支。人工接种条件下,该病原细菌还可侵染西葫芦、丝瓜、茄子、番茄、菜豆、扁豆等植物。这些结果表明,引起广东省南瓜叶枯病的病原为丁香假单胞丁香致病变种(Pseudomonas syringae pv. syringae)。这是首次在中国发现丁香假单胞丁香致病变种引起南瓜叶枯病。     

First report of bacterial leaf blight on cosmos (Cosmos bipinnatus Cav.) caused by Pseudomonas cichorii in Japan

Since 2006, a commercial grower in Japan has noted a leaf blight symptom on potted cosmos plants grown in a field. In August 2012, a Pseudomonas-like bacterium was isolated from the symptomatic leaves and found to cause the same symptom on cosmos seedlings after inoculation. On the basis of bacteriological and phylogenetic analyses, the causative bacterium was identified as Pseudomonas cichorii. This is the first report of bacterial leaf blight on cosmos caused by P. cichorii in Japan.     

小麦链格孢叶枯病的病原学研究

 自70年代以来,在黄河中游麦区发生了一种病原菌未知的小麦叶枯病,1993年至1996年依据柯赫氏证病律进行了病原学研究。结果由陕西、甘肃和河南等省采集的田间病叶标样,发现了11个小麦链格孢(Alternaria triticina Prasada and Prabhu)分离菌株。在PCA平板上培养,该菌的初生分生孢子梗着生由(1~)2~5个孢子构成的短链,分生孢子褐黄色,宽卵球形、椭圆形,具3~8个横隔,0~5个纵隔或斜隔,分隔处缢缩,孢子体20~50 μm×10~15 μm,假喙柱形或膝状,5~47.5 μm×4~5μm。接种小麦叶片上出现长卵形、椭圆形褐色斑点,进而扩展成长条形和不规则形病斑,周边有亮黄色晕圈。严重发病常导致叶枯,叶片大部死亡。     

小麦链格孢叶枯病的病原学研究

 自70年代以来,在黄河中游麦区发生了一种病原菌未知的小麦叶枯病,1993年至1996年依据柯赫氏证病律进行了病原学研究。结果由陕西、甘肃和河南等省采集的田间病叶标样,发现了11个小麦链格孢(Alternaria triticina Prasada and Prabhu)分离菌株。在PCA平板上培养,该菌的初生分生孢子梗着生由(1~)2~5个孢子构成的短链,分生孢子褐黄色,宽卵球形、椭圆形,具3~8个横隔,0~5个纵隔或斜隔,分隔处缢缩,孢子体20~50 μm×10~15 μm,假喙柱形或膝状,5~47.5 μm×4~5μm。接种小麦叶片上出现长卵形、椭圆形褐色斑点,进而扩展成长条形和不规则形病斑,周边有亮黄色晕圈。严重发病常导致叶枯,叶片大部死亡。     

The spatial structure of spontaneous epidemics of different diseases in a groundnut plot

Spontaneous epidemics of rust, early leaf spot, late leaf spot, andRhizoctonia blight simultaneously developed in a groudnut plot. Geostatistical techniques were used to describe and compare the spatial patterns of epidemics.Rhizoctonia blight exhibited a strong aggregative structure, contrasting with leaf spots and rust. The latter disease developed a general epidemic, in combination with local intensification. A strong negative interaction between rust and early leaf spot, and a close correspondence between rust intensification andRhizoctonia blight development were indicated.     

水稻白叶枯病杂草带菌和传病的研究

水稻白叶枯病自发现到现在已有90年的历史。由于发生地区广泛,为害严重,各国对此病曾做了大量研究。日本对它已研究了半个多世纪,我国也有二十多年的研究经历。但对其侵染来源和传播途径,仍有不同看法。我国最初认为种子传病是首要的。但在病区单抓种子处理还不能收到预期效果,又认为病稻草是病区次年的主要菌源。近年来,又发现在严格处理病革、病种子的情况下,仍然发病,故怀疑除上述两种传播途径外,还有其它传播途径。关于杂草传病问题,日本已进行了多年的研究,但和我国国内一样,对杂草带菌传病问题,意见很不一致。我们认为对这一传播途径有彻底弄清的必要,它不仅关系到一个病的侵染循环问题,而且直接关系到对白叶枯病的彻底防治。如果这一传播途径确实存在,我们若不承认它,在防治上就会出现大的漏洞。如果白叶枯病确与杂草无关,盲目地采用相应的措施,也是多余而毫无意义的。这次试验是采用较直接的“离心浓缩针刺接种法”,其结果:第一年证实有马唐等六种杂草、黄豆和水稻根部能够带菌;第二年证实有车前等三种杂草和水稻根不仅带菌,而且可越冬并存活到次年五月;第三年又证实在不同地区有马唐,狗牙根等四种杂草能够带菌越冬,并存活到次年五月中旬。另外,用病区杂草和水稻健苗混栽,结果稻苗上发病,而对照的不发病。通过三年来的试验研究,证实有数种杂草的根茎部不仅带菌,而且能传病。     

Biological control of botrytis leaf blight of onion byGliocladium roseum applied as sprays and with fabric applicators

Gliocladium roseum (5×10⁶ conidia ml^–1) and chlorothalonil (Bravo 500) were compared in two field tests for effectiveness in suppressing leaf blight caused byBotrytis squamosa in cooking onions. The biological control agent and fungicide were applied with sprayers and with specially designed fabric applicators that were mounted interchangeably on an aluminium carriage with bicycle wheels. In the applicators, inoculum and fungicide gravitated from a reservoir down curtains of denim strips and onto portions of onion leaves contacted by the strips. Initial applications were timed using a leaf blight forecasting system (BOTCAST) and three or four subsequent applications were made at weekly intervals. When compared to water checks,G. roseum applied as sprays or by applicators reduced density of leaf spots by about 50–58% during middle and late stages of epidemics. The antagonist was about half as effective as chlorothalonil in suppressing density of spots, regardless of application method. The applicators delivered inoculum in similar densities to proximal and distal halves of leaves, and used at least 35% less volume of inoculum compared to the sprayers. Density of inoculum on leaves treated by applicators was about the same as in spray-treated leaves when canopies were sparse, but less when canopies were dense. It is concluded thatG. roseum has good potential for controlling leaf blight sufficiently to avoid economic yield losses.     

Elucidation of factors contributing to onset of Cercospora leaf blight during later reproductive development of soybean

In Louisiana, Cercospora leaf blight (CLB) of soybean is primarily caused by Cercospora cf. flagellaris, which can be detected in asymptomatic leaves as early as V3 (third trifoliate) growth stage, while symptoms appear around R5 (beginning seed). The fungus produces cercosporin, an important virulence factor, the in vitro production of which is significantly reduced in the absence of simple sugars. Our objective was to investigate the role of foliar simple sugars and endophytic bacteria in CLB symptom onset. C. cf. flagellaris was cultured in filter-sterilized, untreated extracts made from asymptomatic R2 and R5 leaves; in extracts treated with chloroform to isolate hydrophilic molecules, including simple sugars; or with antibiotics to assess the role of endophytic bacteria. Endophytic bacteria were also isolated from leaves and leaf extracts and their interaction with C. cf. flagellaris was investigated. The fungus produced more cercosporin in total R5 and simple sugar-amended R2 leaf extracts, than in R2 leaf extracts. Furthermore, it produced more cercosporin in chloroform-treated R5 leaf extracts, which contained significantly higher levels of simple sugars, especially fructose, than the R2. To our knowledge, this is the first reported connection between foliar sugar content and cercosporin production. Additionally, morphologically diverse bacteria were isolated from different stages of soybean development. Also, bacterial endophytes in R5 leaf extracts and Paenibacillus polymyxa, isolated from R2 leaves, significantly reduced the growth of C. cf. flagellaris. These findings implicated soybean leaf fructose in CLB development and highlighted the potential of using foliar bacterial endophytes for CLB management.     

Soft rot of root chicory in Hokkaido and its causal bacteria

In August 2010, bacterial soft rot was found on root chicory (Cichorium intybus var. sativum) in Hokkaido, Japan. Severely infected plants in fields were discolored, had wilted foliage, and black necrosis of petioles near the crown. Wilted leaves subsequently collapsed and died, forming a dry, brown or black rosette. The root and crown became partially or wholly soft-rotted. Slimy masses on infected areas of roots, turned dark brown or black. Gram-negative, rod-shaped, peritrichously flagellated, facultatively anaerobic bacteria were exclusively isolated from rotted roots, and typical symptoms were reproduced after inoculation with the strains. The bacteria were identified as Dickeya dianthicola, Pectobacterium carotovorum subsp. carotovorum, and Pectobacterium carotovorum subsp. odoriferum based on further bacteriological characterization and the sequence analysis of the malate dehydrogenase gene and 16S rRNA gene. These bacteria should be included with the previously reported Dickeya (=Erwinia) chrysanthemi in Saitama Prefecture, Japan, as causal pathogens of bacterial wilt of chicory.     

Alternaria Brown Spot of Minneola in Greece; Evaluation of Citrus Species Susceptibility

During the last three years, a new disease was observed in northwestern Greece on Minneola trees, hybrid of mandarin and grapefruit. On May small brown necrotic leaf spots surrounded by yellow halo areas of various sizes appeared and covered a major portion of the leaves with extension of necrosis into the veins. On young fruits small, slightly depressed black spots were the first symptoms, which later became 2–7 mm in diameter. Brown spots were observed on the leaves and fruits in several orchards in the same area, causing leaves and fruits to drop. In some orchards over 50% of the fruits were affected. From the fruit and leaf spots the typical small-spore species Alternaria alternata was isolated. Pathogenicity tests were performed by artificially inoculating fruits of Minneola, common mandarin and Clementine. The symptoms of the disease were reproduced only on fruits of Minneola hybrids by the specific strain of the fungus Alternaria alternata pv. citri. Different citrus susceptibility tests indicated that mandarins Minneola, Nova and Page were very susceptible to tested isolates while Clementine SRA and Poros Clementine were not. All lemons and lime Seedless were not susceptible. Grapefruit New Hall was not susceptible, while the Star Ruby was. Orange Lane Late, Navel Late, Oval Poros, Olinda, Navel Athos were not susceptible and only Moro showed reaction being slightly susceptible only to one isolate.