Germination stimulatory activity of bacterial butenolide hormones from Streptomyces albus J1074 on seeds of the root parasitic weed Orobanche minor

Damage caused by Orobanchaceae root parasitic weeds is a substantial agricultural problem for global food security. Many studies have been conducted to establish practical methods of control, but efforts are still required for successful management. Seed germination of root parasitic weeds requires host-derived germination stimulants including strigolactones (SLs). Studies on SLs have revealed that a butenolide ring is the essential moiety for SL activity as a germination stimulant. Interestingly, recent studies have revealed that butenolide hormones regulate the biosynthesis of secondary metabolites and mediate communication in actinomycete bacteria. Because of the structural similarity between SLs and the bacterial butenolides, we evaluated the germination stimulatory activity of butenolides isolated from Streptomyces albus J1074 on root parasitic weeds. These butenolides were found to specifically induce seed germination of Orobanche minor. Our findings contribute to understanding the molecular mechanisms of germination stimulant perception and to the development of a method for their biological control.     

Coffee bacterial diseases: a plethora of scientific opportunities

Coffee is a very important crop for several tropical countries across different continents. The diseases bacterial halo blight (BHB), bacterial leaf spot (BLS), bacterial leaf blight (BLB) and coffee leaf scorch (CLS), caused by the bacterial pathogens Pseudomonas syringae pv. garcae (Psgc), P. syringae pv. tabaci (Psta), Pseudomonas cichorii (Pch) and Xylella fastidiosa subsp. pauca (Xfp), respectively, cause significant reductions in coffee production, although other minor bacterial diseases have also been reported in some countries. Little research progress has been made on aspects that are relevant for control and management of these diseases. In all cases, there is an urgent need to develop rapid and more reliable methods for early detection of the pathogens in order to minimize their negative impact on coffee production. Because of the high rate of intra- and intersubspecific recombination occurring in X. fastidiosa, a permanent revision of the detection methods is necessary. Greater efforts should be made to understand the genetic and virulence diversity of Psgc, Psta and Pch populations. Early studies reported the identification of potential sources of resistance against Psgc and Psta, but, to date, no resistance gene has been isolated. Little effort has been made to understand the biology and molecular mechanisms underlying the interaction between Coffea spp. and these pathogenic bacteria. This review discusses the recent progress on the molecular mechanisms used by these bacteria to cause diseases on other plant species, in order to provide a guideline for the establishment of future research programmes.     

A method for detection of seedborne bacterial diseases in tomato seeds

A method for detection and quantitative estimation of tomato seedborne pathogenic bacteria has been developed. It enables detection in a 7 g tomato seed sample of as few as ten colony-forming units per gram tomato seeds of the following seedborne pathogens of tomato:Pseudomonas syringae pv. tomato,Pseudomonas corrugata, Xanthomonas campestris pv.vesicatoria, andClavibacter michiganense subsp.michiganense. With representative seed samples, the method employs dry grinding, weighing, bacterial extraction and quantitative calculation on selective or semi-selective medium. The efficiency of this method was tested by diluting pathogen-free seed lots with naturally or artificially infested tomato seeds. This procedure enables one to determine the minimal threshold of pathogen which can be detected by this method on media, in comparison with the percentage of diseased seedlings developed from the same seed lots in the growth chamber or in the greenhouse.     

Microbial control of plant diseases with Streptomyces spp.1

Light-coloured Sphagnum fuscum peat is the substrate most widely used in glasshouses in Finland. A number of Streptomyces strains which are strongly antagonistic against a number of soil and seed-borne fungal pathogens, both in vitro and in vivo, have been isolated from light-coloured peat. Seed dusting with Streptomyces prevented or reduced damping-off and foot-rot disease caused by Alternaria brassicicola and Rhizoctonia solani on crucifers. Seed treatment slightly increased yields of cereals in fields experiments. Spraying the substrate with a suspension of Streptomyces reduced root diseases on cucumbers caused by Pythium, and in many cases successfully prevented fusarium wilt of carnations. A dry powder preparation has been made from the Streptomyces isolates, and applied at a dose of 5-10 g kg^-1 in seed dusting, and 0.1-10 g 100 m^-2 when spraying the substrate. The microbe was most effective in peat soil, although good results have also been obtained in fine sand and clay soils.     

我国甘薯新病害-茎腐病的研究初报

 2006年以来广东省主要甘薯产区发现1种甘薯新病害,主要症状表现为叶片变黄,茎基部呈黑色水浸状腐烂,并逐渐沿茎枝向顶端腐烂,后整株倒伏、死亡。从甘薯病茎部分离得到了病菌,经柯赫法则验证为致病病原菌。根据病原菌的形态特征、培养性状、生理生化及16S rDNA序列分析,鉴定其为菊欧文氏菌(Erwinia chrysanthemi)。采用茎枝、菌液共培养法接种8个甘薯品种,结果表明8个品种均无抗病性,病原菌致病性较强。这是我国首次发现该病害。      

西洋参根部病害研究进展

综述了近年来国内外关于西洋参根腐病、锈腐病、疫病等主要根部病害的研究进展,就相关病原菌及其生物学特性、影响病害发生的环境因子、采用的化学及生物防治方法进行了介绍,结合当前存在的问题提出今后应加强的研究重点。     

噬菌体防治植物细菌性病害研究进展

植物病原细菌是限制农业生产的主要原因之一,作物受害严重,造成巨大的经济损失。化学防治、农艺防治以及抗病育种等方法,对植物细菌性病害实现了较好的防治,但是这些方法各自存在着不足之处。噬菌体无处不在,有细菌的地方就有噬菌体。噬菌体具有特异性,可以自我复制,相比于植物细菌性病害的其他防治方法,噬菌体防治环境友好,且制造成本低廉,越来越多的研究学者尝试用噬菌体控制细菌性病害,以补充传统防治方法的不足。本文列举了一些较为严重的植物细菌性病害的为害、传统的防治办法,并总结了已有的噬菌体防治手段以及噬菌体防治的发展前景。     

河北省甘薯茎腐病研究初报

甘薯茎腐病是近几年在我国发现的一种新的细菌性病害,目前该病已在我国的福建、广东、江西、广西、海南、河南、重庆、江苏等地发生。2013年10月在对河北省甘薯病害的调查中在文安县发现了大量疑似甘薯茎腐病的病株,给当地的甘薯生产造成了严重的影响。经对疑似病株病原菌的分离纯化、柯赫氏法则验证、形态观察以及基于16SrDNA序列的分析,最终确定该病害为甘薯茎腐病,病原菌为达旦提狄克氏菌(Dickeya dadantii)。这是该病害首次在河北省被发现。     

Serious fungal and bacterial diseases of almond in Greece 1

The main fungal and bacterial diseases of almond in Greece are reviewed, with particular attention to phytophthora collar rot and verticillium wilt.     

拮抗细菌Bs-0728对板蓝根根腐病的防治作用

［目的］ 筛选对板蓝根根腐病有较强拮抗作用的生防菌株。［方法］ 采用平板对峙法对137个板蓝根根际土壤样本中分离到的201株拮抗细菌进行测试。［结果］ 筛选出1个对板蓝根根腐病菌有强烈抑制作用的菌株Bs-0728。结合显微镜观察确定Bs-0728菌株对板蓝根根腐病的主要致病菌茄腐镰刀菌（Fusarium solani）菌丝生长有较强的抑制作用,导致菌丝生长畸形,弯曲,部分细胞膨大。田间试验结果表明,Bs-0728的发酵液田间防效达72.97%,且增产86.26%。经形态观察、生理生化反应及16S rDNA 序列分析,初步将此拮抗细菌鉴定为枯草芽胞杆菌Bacillus subtilis。［结论］ 枯草芽孢杆菌Bs-0728菌株是一株很有应用前景的生防菌株。     

Seeing the forest for the trees: Use of phages to treat bacterial tree diseases

Trees and woody plants can be attacked by many pests and pathogens either individually or as polymicrobial infections. In particular, infections caused by tree-specific bacterial pathogens have become more common during the last decade, causing serious concern for important tree and woody plant species in horticulture, urban environments, and forests. For example, Xylella and Pseudomonas bacteria are causing significant economic and ecological devastation throughout Europe in olive, cherry, and other stone fruits, mainly because of lack of efficient control methods and the emergence of bacterial resistance to traditional antimicrobial compounds such as copper and antibiotics. Hence, there is an urgent need for innovative approaches to tackle bacterial plant diseases. One way to achieve this could be through the application of biological control, which offers a more environmentally friendly and targeted approach for pathogen management. This review will explore recent advances in use of pathogen-specific viruses, bacteriophages (or phages), for the biocontrol of bacterial tree diseases. Phages are an important component of plant microbiomes and are increasingly studied in plant pathogen control due to their highly specific host ranges and ability to selectively kill only the target pathogenic bacteria. However, their use still poses several challenges and limitations, especially in terms of managing the bacterial diseases of long-lived trees. A particular insight will be given into phage research focusing on controlling Pseudomonas syringae pathovars, Erwinia amylovora, Xanthomonas species, Ralstonia solanacearum, and Agrobacterium tumefaciens. Recent milestones, current challenges, and future avenues for phage therapy in the management of tree diseases are discussed.     

朝鲜蓟细菌性根茎腐烂病病原的分离与鉴定

 在湖南省常德市西洞庭管区种植的朝鲜蓟（Cynara scolumus  L.）上发现了一种新的病害,其症状表现为地上部分从外层叶片开始逐步枯萎,随后根部和主茎杆的髓部腐烂变褐,最后整株枯萎。从田间感病朝鲜蓟茎杆的病健交界处用NA培养基分离,获得10个菌株,分别指定为HNXDT001~010,并进行了致病性测定、形态观察和细菌学特征分析,同时对HNXDT002菌株进行分子生物学鉴定。结果表明,该系列菌株在NA培养基上均形成灰白色圆形菌落,稍突起,有光泽,半透明。在显微镜下菌体呈短杆状,两端钝圆,具有2～8根周生鞭毛,革兰氏阴性。10个菌株通过针刺法接种均可导致朝鲜蓟茎杆、胡萝卜、辣椒、白菜、土豆、番茄和莴苣茎杆软腐,经科赫法则验证为致病病原菌。该菌株的16S rDNA序列和果胶酶基因片段测序(分别用16S rDNA通用引物16SF/16SR和果胶酶基因引物Y1/Y2扩增)与系统发育学分析表明,其16S rDNA序列(GenBank Accession No. JF721958)与胡萝卜软腐果胶杆菌胡萝卜亚种（Pectobacterium carotovorum  subsp.  carotovorum）菌株ATCC15713 (GenBank Accession No. U80197)序列同源性高达99％;果胶酶基因序列(GenBank Accession No. JF721960)与胡萝卜软腐果胶杆菌胡萝卜亚种（Pectobacterium carotovorum subsp. carotovorum）PC1菌株(GenBank Accession No. CP001657)序列同源性为93%。结果表明：朝鲜蓟细菌性根茎腐烂病病原为胡萝卜软腐果胶杆菌胡萝卜亚种。     

四硫代碳酸钠对蔬菜根病的防治效果及对土壤生物学性状的影响

为明确四硫代碳酸钠(sodium tetrathiocarbonate,STTC)在蔬菜根病防治上的应用价值及制定应用技术,本研究通过室内瓶土熏蒸法,进行了STTC对病菌的室内毒力测定;用温室盆栽法,进行植前熏蒸处理,测定土壤中病菌数量的变化和对病害的防效,同时进行植后熏蒸处理,测定药剂处理点和根际处病菌数量的变化;通过土壤施药后随即移栽幼苗的方法,评价药剂对蔬菜幼苗的安全性;通过室内模拟田间熏蒸条件,测定药剂不同浓度和熏蒸时间对土壤中主要微生物类群数量和主要土壤酶活性的影响。结果显示STTC对辣椒疫霉病菌Phytophthora capsici、黄瓜枯萎病菌Fusarium oxysporumf.sp.cucumerinum、茄子黄萎病菌Verticillium dahliae、番茄立枯病菌Rhizoctonia solani和蔬菜菌核病菌Sclerotinia sclerotiorum均有较好的杀灭活性,LD50分别为3.956、4.241、5.222、5.457和6.197mg/kg;80g/m2 STTC移植前处理对辣椒疫霉病和黄瓜枯萎病的防效可分别达到91.01%和82.51%;浓度低于900μg/mL的STTC对当日熏蒸后移栽的3叶期辣椒、黄瓜、番茄、白菜和油菜幼苗均表现安全;在辣椒和黄瓜生长期穴施1 200μg/mL STTC能有效减少土壤中辣椒疫霉病菌和黄瓜枯萎病菌的数量;土壤中微生物类群数量监测结果表明,在0.1~50.0μg/g浓度范围内,STTC对土壤真菌有强烈抑制作用,对土壤细菌和放线菌为先抑制后促进。对土壤酶活性测定结果表明,当STTC用量为0.1、1.0、5.0、10.0和50.0μg/g时,对土壤脲酶和蔗糖酶的活性表现为先抑制后促进,对蛋白酶的活性表现为在STTC低浓度时活性增加,高浓度时为先抑制后增加。综合结果表明,STTC用于经济作物生产中的土壤熏蒸具有安全、有效和施用简便的特点,或可广泛使用。     

Evaluation of biocontrol agents for managing root diseases on hydroponically grown tomato

Journal of Plant Diseases and Protection - The effect of the bacterial strain Pseudomonas fluorescens 5.014 together with three commercial biocontrol products (Binab T, Gliomix and Mycostop)...     

苯醚甲环唑等杀菌剂包衣种子防治花生冠腐病和根腐病

为筛选能兼治花生冠腐病和根腐病、安全而高效的种子处理药剂,采用室内生测法比较了4种杀菌剂对花生冠腐病菌和根腐病菌的毒力,评价了其包衣种子对花生的安全性,并进行了温室接菌盆栽和田间防治试验。结果显示,苯醚甲环唑、氟啶胺、咯菌腈和氟菌唑对花生冠腐病菌的毒力差异较大,EC_(50)分别为0.05、6.56、0.52和1.43 mg/L;对花生根腐病菌的毒力均较高,EC_(50)分别为0.49、0.31、0.44和0.37 mg/L。氟菌唑2 g(a.i.)/kg种子包衣后,花生出苗率和幼苗的根长、株高和茎叶鲜重均降低,出苗时间延迟1~2 d;而氟菌唑0.5、1 g(a.i.)/kg种子包衣及苯醚甲环唑、氟啶胺、咯菌腈3种杀菌剂的所有剂量处理对花生出苗和幼苗生长均无影响。苯醚甲环唑0.5、1、2 g(a.i.)/kg种子,氟啶胺0.4、0.8、1.6 g(a.i.)/kg种子,咯菌腈0.1、0.2、0.4 g(a.i.)/kg种子和氟菌唑0.5、1 g(a.i.)/kg种子包衣对花生冠腐病、根腐病的温室接菌盆栽防效均在80.19%以上。苯醚甲环唑1、2 g(a.i.)/kg种子和咯菌腈0.4 g(a.i.)/kg种子包衣对花生冠腐病、根腐病的田间防效较高,均在75.30%以上,且对荚果的增产率为5.60%~11.10%。表明苯醚甲环唑和咯菌腈包衣种子对花生安全,且可有效防治花生冠腐病和根腐病,具有开发为兼治药剂的潜力。     

Bacterial diseases of tomato in southern Spain: application of a detached tissue assay to evaluate bacterial pathogenicity

Tomatoes are one of the most important crops in southern Spain, especially during the cold season. As a preliminary step in the design of an integrated disease management programme for tomato, a study on the occurrence of bacterial diseases in tomato houses of Almería (ES) was carried out during the 1993/1997 growing seasons. Sixty-four bacterial strains were isolated from tomato plants showing symptoms of bacterial diseases and 41 of them (64%) were characterized as pathogenic. The bacterial tomato pathogens most frequently isolated were Erwinia carotovora subsp. carotovora, Pseudomonas corrugata, Pseudomonas syringae pv. tomato and Xanthomonas vesicatoria. The pathogenicity of the bacterial isolates on tomato was tested by the conventional seedling assay and by an in vitro assay using detached tissues developed in our laboratory. Close correspondence between the two assays was observed. An in vitro detached tissue assay is proposed for determining the pathogenicity of bacterial isolates on tomato.     

Evaluation of soil solarization for control of root diseases of row crops in Victoria

The effect of soil solarization on the viability of plant pathogens and disease was evaluated in Victoria. The treatment was tested in NW and S Victoria with natural soil inoculated with high inoculum levels of Eusarium oxysporum, Plasmodiophora brassicae, Sclerotium cepivorum, Sclerotinia minor, Sclerotinia sclerotiorum, Verticillium dahliae and the nematodes Meloidogyne javanica and Pratylenchus penetrans. Other experiments were established at sites with a previous history of disease.
Solarization of artificially inoculated soils reduced inoculum levels to at least a depth of 10 cm and effectively controlled diseases caused by P. brassicae on broccoli, and S. minor and S. sclerotiorum on lettuce. The treatment reduced inoculum levels but not disease of carnations and watermelons affected by E. oxysporum , tomatoes affected by M. javanica , celery affected by P. penetrans , and onions affected by S. cepivorum. Results were inconclusive for tomatoes affected by V. dahliae.
Experiments in naturally infested soils established that solarization reduced disease and increased yields of Chinese cabbage affected by P. brassicae , celery affected by P. penetrans , lettuce affected by S. minor and watermelon affected by root rot.
Solarization reduced disease of onions affected by S. cepivorum but did not significantly increase yield. At all sites the treatment reduced the number of viable propagules of the pathogens to at least a depth of 10 cm.     

黑龙江省水稻品种资源对水稻细菌性褐斑病的抗性鉴定

选育和应用抗病品种是防治水稻细菌性病害最经济有效的措施。本研究采用苗期喷雾法和针刺法对黑龙江省42个水稻主栽品种进行抗性鉴定。结果表明,利用针刺法鉴定的各水稻品种中表现中抗以上的品种有14个,其中高抗品种2个,对接种水稻品种病斑长度进行差异显著性分析,42个水稻主栽品种间抗性存在显著差异;利用喷雾法鉴定各品种,病级表现1级的品种有7个,占16.7%。对数据进行比较分析,针刺法和喷雾法对抗病品种鉴定的结果基本一致。本研究鉴定的2个高抗稻种资源对于抗细菌性褐斑病生产实践提供重要价值。因此,加大对水稻品种资源的深入研究,对实现水稻细菌性褐斑病的可持续控制有着重要意义。     

High concentrations of antagonistic bacterial strains from diseased sanqi ginseng rhizosphere suppressed Fusarium root rot

European Journal of Plant Pathology - Sanqi ginseng Fusarium root rot caused by Fusarium oxysporum, is a serious soil-borne disease that threatens the sustainable development of the sanqi ginseng...