Effect of temperature,cultivars, injury of root and inoculums load of Ralstonia solanacearum to cause bacterial wilt of tomato

Bacterial wilt, caused by Ralstonia solanacearum , is responsible for severe losses in tomato crops in the world. In the present study, the effect of temperature, cultivars of tomato, injury of root system and inoculums load of R. solanacearum to cause bacterial wilt disease under control conditions was undertaken. Three strains UTT-25, HPT-3 and JHT-5 of R. solanacearum were grown at 5–40?°C in vitro to study, the effect of temperature on the growth of bacteria and maximum growth was found at 30?°C after 72?h in all the strains. Twenty-one days old seedlings of two cultivars of tomato i.e. N-5 (moderately resistant) and Pusa Ruby (highly susceptible) were transplanted into the pots and inoculated with R. solanacearum strain UTT-25 (5 × 10⁸?cfu/ml), mechanically injured and uninjured roots of the plant. The plants were allowed to grow at 20, 25, 30 and 35?°C at National Phytotron Facility, IARI, New Delhi to study the effect of temperature on intensity of bacterial wilt disease. Maximum wilt disease intensity was found 98.73 and 95.9 % in injured roots of Pusa Ruby and N-5 cultivars of tomato at 35?°C on 11th days of inoculation, respectively. However, no wilt disease was observed in both the cultivars at 20?°C up to 60?days. For detection of R. solanacearum from asymptomatic tomato plants, hrpB-based sequence primers (Hrp_rs2F and Hrp_rs2R) amplified at 323?bp was used in bio-PCR to detect R. solanacearum from crown, mid part of stem and upper parts of the plant. Another experiment was conducted to find out the inoculum potential of R. solanacearum strain UTT-25 to cause bacterial wilt in susceptible cultivar Pusa Ruby. The bacteria were inoculated at concentration of bacterial suspension 10 to 10¹⁰?cfu/ml in injured and uninjured roots of the plants separately and injured root accelerated wilt incidence and able to cause wilt disease 63.3% by 100?cfu/ml of R. solanacearum, while no disease appeared at 10?cfu/ml on the 11th day of inoculation in injured and uninjured roots of the plant.     

番茄连作青枯病不同发病时期的非根际土壤细菌群落变化特征

[目的]研究连作条件下番茄青枯病不同发病时期的非根际土壤微生物群落差异,明确土壤微生物对青枯病发病时期的响应机制。[方法]本研究对16S rRNA V4‒V5区进行实时荧光定量PCR和高通量测序,综合分析了连续种植第1、3、5和7季的发病高峰期和发病末期的番茄非根际土壤的病原菌数量、细菌群落多样性、群落组成、标志细菌类群和群落构建机制。[结果]发病高峰期的青枯菌数量(1.28×10⁷ copies/g)要高于发病末期(1.77×10⁶ copies/g)。随着连作时间的增加,发病时期对细菌群落多样性的影响逐渐增加。第3季和第5季不同发病时期之间的细菌群落alpha和beta多样性存在显著差异。LEfSe分析发现,番茄青枯病发病高峰期和发病末期的非根际土壤样品有其各自不同的标志细菌类群。此外,随连作时间的延长协助青枯菌致病的细菌逐渐累积。发病高峰期是微杆菌属(Microbacterium)和亚硝化螺菌属(Nitrosospira)协助青枯菌致病,而在发病末期,则由鞘脂菌属(Sphingobium)、norank f norank o SBR1031和norank f Rhodothermaceae协助青枯菌致病。群落构建过程分析发现不同发病时期细菌群落均以随机过程的扩散限制为主,但细菌群落在发病高峰期比发病末期的同质化作用更强。[结论]本研究发现青枯病发病高峰期和发病末期的番茄非根际土壤的细菌群落多样性、组成和结构在第3季和第5季时存在显著差异。此外,细菌群落会随着连作时间发生动态变化,而这些变化可能与细菌群落构建机制相关联。研究结果加深了对连作条件下的番茄青枯病发展过程的认识,可为防治青枯病提供参考依据。     

Transmission of seed-borne infection of chilli by Burkholderia solanacearum and effect of biological seed treatment on disease incidence

Abstract

A survey of chilli fields in the state of Karnataka, India, showed the presence of bacterial wilt disease in important chilli growing regions. The disease incidence ranged from 26?–?32%. The pathogen was isolated from infected plant material and seeds. Infected plant material showed the release of milky white bacterial ooze. Burkholderia solanacearum was detected from chilli seeds by liquid assay and its identity was confirmed by biochemical tests, hypersensitive reaction and pathogenicity tests. Seed transmission of the pathogen up to 45% was observed in seeds artificially infested with the pathogen. Among different tissues of the seed, endosperm showed the presence of the pathogen. Biological seed treatment with antagonistic Pseudomonas fluorescens significantly (p?=?0.05) improved the seed quality parameters under laboratory conditions and drastically reduced the bacterial wilt incidence under field conditions. Seed-borne nature, transmission and effect of Pseudomonas fluorescens in both the forms of pure culture and formulation on seed quality parameters and bacterial wilt incidence are discussed in the present work.     

噬菌体鸡尾酒联合生物有机肥防控番茄青枯病的效果研究

【背景】前期研究表明,可专性侵染青枯菌的噬菌体鸡尾酒(组合)可有效减少番茄青枯病的发生。生物有机肥虽然可降低青枯病发病率,但受田间环境影响,防控效果常不稳定。【目的】为了提高生物有机肥的防控效果,靶向抑制番茄青枯病,探究噬菌体鸡尾酒联合含有解淀粉芽孢杆菌的生物有机肥防控番茄青枯病的田间效果,以及该防控方法对番茄根际细菌群落结构的影响。【方法】将经解淀粉芽孢杆菌T-5二次发酵获得的生物有机肥(Bio-Organic Fertilizer,BOF)在春季作为基肥施入番茄大棚,开花期在番茄根部浇灌噬菌体鸡尾酒悬液,统计青枯病的发生情况和番茄根际青枯菌的数量,根据高通量测序结果分析番茄根际细菌群落的结构变化。【结果】与常规施肥相比,生物有机肥配合噬菌体鸡尾酒(BOF+P)可显著降低番茄青枯病的发病率,显著改变根际细菌群落的β多样性,提高拟杆菌门(Bacteroidetes)的相对丰度,并降低芽单胞菌门(Gemmatimonadetes)的相对丰度。【结论】噬菌体鸡尾酒可显著提升生物有机肥防控番茄青枯病的效果,具有良好的应用潜力。     

生物有机肥对土壤微生物群落结构变化及西瓜枯萎病的调控

【目的】研究施用生物有机肥处理土壤后对西瓜枯萎病发生的影响,明确可能与西瓜枯萎病发病密切相关的土壤微生物群落结构。【方法】设置2组不同年份材料对比,依次为施用生物有机肥后2016年发病期(CK2016、T12016)和2017年发病期(CK2017、T12017)。基于16S r RNA序列测定,利用Illumina Miseq高通量测序平台对施用生物有机肥后不同年份的土壤微生物群落组成和差异进行测序分析。【结果】试验结果发现,不同年份的土壤微生物群落中alpha多样性指数并无明显的差异,但是施用生物有机肥后的土壤相比对照土壤中细菌群落多样性略有增高。不同年份土壤细菌群落结构在门水平上差异不显著,其中变形菌门和硬壁菌门是构成这两个年份土壤细菌的重要组成部分,同时也是比较稳定的微生物类群。在属水平上分析发现主要动态变化菌属为芽孢杆菌属、肠球菌属、乳球菌属及水恒杆菌属。通过Spearman分析发现它们与西瓜枯萎病发生率的关系均为负相关。【结论】施用生物有机肥可帮助西瓜连作土壤的生态修复,对枯萎病防治起到一定的作用。通过对施用生物有机肥的不同年份土壤微生物种群结构动态变化及对枯萎病发生率呈正负相关的微生物菌属的分析研究,为如何利用调节土壤微生物群落结构来防治西瓜枯萎病提供了新的思路。     

利迪链霉菌M01对番茄生长、青枯病发病率及根际细菌群落组成的影响

【背景】利迪链霉菌(Streptomyces lydicus)对多种作物均有较好的促生效果,且对病原真菌具有广谱抑制作用,但该菌对细菌性青枯病的防控研究较少。【目的】探究利迪链霉菌M01能否促进番茄生长并抑制番茄青枯病,以及M01对番茄生长的影响是否通过影响根际细菌群落结构实现。【方法】采用温室盆栽试验和扩增子高通量测序技术研究M01对番茄生长、青枯病发病率及根际细菌群落组成的影响。【结果】施用利迪链霉菌M01的番茄植株鲜重、干重、株高、用土壤与作物分析开发(soil and plant analyzer develotrnent, SPAD)方法测量的叶绿素浓度、根系活力和植株P含量比对照分别提高了22.7%、12.5%、16.0%、28.1%、18.4%和17.9%,其中对株高、SPAD值和植株磷含量影响显著(P<0.05)。M01处理延缓了番茄青枯病的发病时间,接种9周后发病率比对照降低了41.8%。此外,M01对番茄根际细菌群落无显著影响(门水平群落组成,P=0.4;属水平群落组成,P=0.4)。【结论】利迪链霉菌M01可促进番茄植株生长并抑制番茄青枯病,利迪链霉菌M01对番茄生长的影响并非通过调控根际细菌群落实现。     

健康与感染青枯病烟株根际土壤与茎秆细菌群落结构与多样性

【目的】了解健康烟株与感染青枯病烟株在根际土壤、茎杆发病部位、茎杆病健交界部位以及未发病茎杆的细菌群落结构与多样性。【方法】分别对土壤与茎杆样品中细菌的16S rRNA基因V3-V4区进行扩增,采用Illumina MiSeq测序技术对扩增片段进行高通量测序,然后对健康烟株与感染青枯病烟株不同部位细菌群落结构与多样性进行分析。【结果】感染青枯病烟株发病茎杆及根际土壤的细菌群落多样性高于健康烟株茎杆及其根际土壤样品,病健交界茎杆样品细菌群落多样性低于健康烟株。变形菌门(Proteobacteria)在所有样品中均为优势菌门;所有烟株根际土壤的优势菌门为拟杆菌门(Bacteroidetes)、酸杆菌门(Acidobacteria)、放线菌门(Actinobacteria)和绿弯菌门(Chloroflexi);健康烟株茎杆部位的优势菌门为蓝细菌门(Cyanobacteria);感染青枯病烟株发病茎杆和病健交界茎杆部位的优势菌门为蓝细菌门(Cyanobacteria)和厚壁菌门(Firmicutes)。所有根际土壤样品的优势菌属为劳尔氏菌属(Ralstonia)、假单胞菌属(Pseudomonas)、鞘脂单胞菌属(Sphingomonas)、黄杆菌属(Flavobacterium)和代尔夫特菌属(Delftia),而感染青枯病烟株根际土壤的劳尔氏菌属(Ralstonia)和假单胞菌属(Pseudomonas)相对丰度显著高于健康烟株根际土壤,鞘脂单胞菌属相对丰度显著低于健康烟株根际土壤。烟株茎杆的优势菌属为劳尔氏菌属和假单胞菌属等。感染青枯病烟株病健交界茎杆中劳尔氏菌属、肠杆菌属(Enterobacter)和泛菌属(Pantoea)相对丰度显著低于健康烟株样品。【结论】健康与感染青枯病烟株茎杆样品细菌群落的丰富度和多样性明显低于相应的根际土壤样品。较健康烟株而言,感染青枯病烟株根际土壤和茎杆样品细菌群落丰富度和多样性均表现出不同程度地增加,且根际土壤细菌群落结构变化较茎杆样品明显,而病健交界茎杆样品细菌群落丰富度和多样性降低。烟草青枯病为典型土传病害,其病原茄科劳尔氏菌尽管能在烟株维管束中蔓延扩增,但主要还是分布于土壤中;它的存在似乎对土壤细菌群落的影响大于茎杆样品的。该研究结果提示对于青枯病的防治不能局限于烟株本身,田间土壤也应加大防治力度。     

Effect of combination of bio-agents and mineral nutrients for the management of alfalfa wilt pathogen Fusarium oxysporum f. sp. medicaginis

Abstract

Biological and nutrient management of soil borne disease is increasingly gaining stature as a possible practical and safe approach. Inhibitory effects of fungal and bacterial antagonists were tested under in vitro conditions against the wilt pathogen of alfalfa Fusarium oxysporum f. sp. medicaginis. Trichoderma harzianum and Pseudomonas fluorescens (PI 5) were found to be effective against the alfalfa wilt pathogen. Manganese sulphate at 500 and 750 ppm inhibited the mycelial growth of F. oxysporumf. sp. medicaginis under in vitro conditions. In pot culture studies, manganese sulphate at 12.5 mg/kg reduced the wilt incidence (23.33%). Combined application of manganese sulphate 12.5 mg/kg + T. harzianum 1.25 mg/kg of soil significantly reduced the wilt incidence accompanied by improved plant growth and yield in pot culture. The mixture of manganese sulphate (25 kg/ha) + T. harzianum (2.5 kg/ha) significantly reduced the wilt incidence when applied as a basal dose in the field conditions. The average mean of disease reduction was 62.42% over control.     

百里酚和香芹酚改变肠道微生物组成抑制羔羊腹泻的作用研究

【目的】本试验研究百里酚和香芹酚对滩羊羔羊腹泻、肠道短链脂肪酸和微生物组成的影响,旨在为利用植物提取物手段治疗羔羊腹泻提供可用的添加剂和理论基础。【方法】本研究选择腹泻发病时间为2-3 d的10只腹泻羔羊,随机分为2组,分为腹泻羔羊组(CON组)和百里酚和香芹酚处理组(SCAT组),试验期间SCAT组羔羊补充200 mg/只/d的百里酚和香芹酚1:1混合品,处理时间为7 d。【结果】百里酚和香芹酚处理能够显著提高腹泻羔羊日增重,降低羔羊腹泻指数和腹泻率(P<0.05),降低血清促炎因子表达水平(P<0.05),提高肠道短链脂肪酸(short-chain fatty acids,SCFA)丁酸浓度(P<0.05);同时百里酚和香芹酚能够改变腹泻羔羊肠道微生物组成,提高肠道中双歧杆菌(Bifidobacteriaceae)和阿克曼氏菌(Akkermansiaceae)的相对丰度,降低肠杆菌科(Enterobacteriaceae)相关菌的相对丰度。【结论】百里酚和香芹酚能够提高肠道有益菌相对丰度和有益代谢物丁酸的浓度,降低致病菌相对丰度,从而有效抑制羔羊腹泻,可作为新型替...     

Antibacterial activity of certain plant extracts against bacterial wilt of tomato

Abstract

Five isolates of Ralstonia solanacearum were isolated from a naturally wilted root of tomato plants grown in Assiut governorate. The antibacterial activity of extract of Datura, Garlic and Nerium were tested in controlling R. solanacearum in vitro and in vivo. Garlic exhibited the strongest antibacterial activity against bacterial wilt in vitro and in vivo followed by Datura and then Nerium. Cold water extracts of these plant species were more effective than hot water extract in the development of the disease in vivo. In greenhouse experiments, the application of the tested plant extract to soil at the time of inoculation, two days before inoculation and two days after inoculation the pathogen, significantly reduced the disease index of wilt on Super Marmande tomato cultivars. The application of plant extracts at the same time as inoculation resulted in the highest reduction of disease index.     

水肥菌一体化番茄基质栽培系统青枯病病株和健株根际微生物群落结构的差异

[目的]探究水肥菌一体化基质栽培系统番茄青枯病害发生与根际群落结构的相互关系.[方法]通过田间病情调查,统计番茄青枯病发病率和病情指数,进而利用高通量测序技术比较分析感染青枯病和健康番茄植株根际基质细菌群落结构多样性和组成.[结果]番茄植株在生殖生长期(移栽后60 d)的发病率(6.17％)和病情指数(5.11)均大于...     

Induction of bacterial blight (Xanthomonas oryzae pv. oryzae) resistance in rice by treatment with acibenzolar-S-methyl

The role of the plant defence activator, acibenzolar‐S‐methyl (ASM), in inducing resistance in rice against bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) was studied. Application of ASM induced resistance in rice to infection by Xoo. When the pathogen was clip‐inoculated to the rice plants, it caused bacterial leaf blight symptoms in the untreated control. However, in the rice plants pretreated with ASM, infection was significantly reduced. Induced systemic resistance was found to persist for up to 3 days in the pretreated rice plants. Increased phenolic content and accumulation of pathogenesis‐related (PR) proteins, viz. chitinase, β‐1,3‐glucanase and thaumatin‐like protein (TLP; PR 5) were observed in rice plants pretreated with ASM followed by inoculation with Xoo. Immunoblot analysis using rice TLP and tobacco chitinase antiserum revealed rapid induction and over‐expression of 25 and 35 kDa TLP and chitinase, respectively, in rice in response to pretreatment with ASM followed by Xoo inoculation. Based on these experiments, it is evident that induction of disease resistance in rice was accelerated following treatment with ASM.     

Activity of sodium trimetaphosphate,associated or not with fluoride,on dual-species biofilms

Abstract

A response surface methodology was used to build a model to predict reductions in uropathogenic Escherichia coli biofilms in response to three compounds: cranberry extract [CB] at 3.0–9.0%, and caprylic acid [CAR] and thymol [TM] at 0.01%–0.05%. The predictive model for microbial reduction had a high regression coefficient (R²?=?0.9988), and the accuracy of the model was verified (R²?=?0.9527). Values of CAR, TM, and the quadratic term CAR² were the most significant (P?10 reduction) determined by ridge analysis were 8.3% CB +0.04% CAR +0.04% TM at 37?°C for 1?min. The model could be used to predict the most cost-efficient amounts of antimicrobial agents for anti-urinary tract infection products such as catheter lock solution and antimicrobial coatings for catheters.     

Combined application of native Trichoderma isolates possessing multiple functions for the control of Fusarium wilt disease in banana cv. Grand Naine

Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) is considered as a lethal disease of bananas worldwide. To manage the disease effectively, 20 rhizospheric and 43 endophytic Trichoderma isolates obtained from 12 different Foc resistant banana accessions were evaluated against Foc in vitro and in vivo. In vitro screening among Trichoderma isolates for their multiple functions (mycelial and spore germination inhibition, hydrogen cyanide, chitinolytic enzymes, non-volatile and volatile metabolites production) in suppressing Foc and promoting plant growth (IAA production and phosphate solubilisation) indicated that the multiple biocontrol actions were significantly higher in 6 isolates of rhizospheric Trichoderma and 10 isolates of endophytic Trichoderma compared to other isolates. The greenhouse evaluation of individual application of these rhizospheric and endophytic Trichoderma isolates against Fusarium wilt pathogen in cv. Grand Naine (AAA) indicated significant suppression of Fusarium wilt disease and increased plant growth characters as compared to Foc pathogen inoculated plants. However, none of these individual Trichoderma isolates recorded complete suppression of Fusarium wilt disease. Therefore, the greenhouse evaluation involving combination of rhizospheric Trichoderma sp. NRCB3 + endophytic Trichoderma asperellum Prr2 recorded 100% reduction of Fusarium wilt disease and increased plant growth parameters up to 250% when compared to individual isolates application and Foc alone-inoculated plants. Further, the field evaluation of this combination of Trichoderma isolates applied for three times: (1) at 15 days before planting, (2) second month after planting and (3) fourth month after planting resulting in significant reduction of Fusarium wilt disease and also increase in bunch weight as compared to untreated control plants. Therefore, these Trichoderma isolates may be used in combination for the effective suppression of Fusarium wilt disease in banana.     

贝莱斯芽孢杆菌(Bacillus velezensis) JJYY防控土传病害效果评价及其全基因组测序分析和抗菌成分鉴定

【背景】土传病害是世界农业可持续发展的关键限制因子,在我国蔬菜和中药材上发生日趋严重,引起严重的连作障碍。生物防治对环境和农产品安全,是目前研究的热点和重点。【目的】明确对土传病原菌具有广谱抗菌活性菌株JJYY的种类及其防控效果和主要抗菌产物,为新型生物农药开发奠定基础。【方法】结合扫描电镜观察、生理生化分析和16S rRNA基因扩增测序技术鉴定菌株JJYY。分别利用比浊法和菌丝生长抑制法测定该菌提取物对4种土传病原细菌和5种土传病原真菌的EC₅₀,利用盆栽试验评价对番茄青枯病等病害的防控效果。利用二代Illumina NovaSeq与三代PacBio Sequel相结合测序技术对菌株JJYY进行全基因组测序,使用PGAP等软件进行基因注释等分析,利用反相制备液相色谱和质谱初步分离鉴定抗菌物质。【结果】菌株JJYY是一株贝莱斯芽孢杆菌（Bacillus velezensis）,该菌提取物对4种土传细菌和5种土传真菌的EC₅₀分别为0.940-1.092 mg/mL和2.733-3.678 mg/mL。对番茄青枯病、菊花根腐病和辣椒枯萎病的最高防效在80.00%-87.74%之间,与化学药剂链霉素或噁霉灵无显著差异（P>0.05）。该菌基因组大小为3 929 792 bp,编码3 895个基因,与B.velezensis JS25R和B.subtilis 168具有3 445个和2 997个同源编码基因。预测该基因组共有12个次级代谢产物合成功能基因簇。从该菌株提取物中共分离出9种抗菌组分,其中2个初步判定为已知大环内酯类抗生素macrolactin D和7-O-malonyl-macrolactin A。【结论】菌株JJYY是一株对土传病原细菌和真菌病害均有较高防效的贝莱斯芽孢杆菌,该菌基因组与已知贝莱斯芽孢杆菌不同,并产生多种已知和未知的抗菌物质,继续深入分析鉴定其抗菌物质和抗菌机制将为开发新型高效的生物农药奠定良好基础。     

青枯病易感和钝感桑树品种根际土壤真菌群落结构比较

为研究青枯病易感和钝感桑树品种植株根际土壤真菌群落组成,该研究以ITS1F和ITS2R为引物,基于高通量测序技术对桑树青枯病易感品种(台湾长果桑,SM)和桑树青枯病钝感品种(桂桑12号,IM)植株根际土壤真菌群落结构进行分析。结果表明:(1)两个品种间指示真菌丰富度的ACE、Chao1指数及表征多样性的Shannon指数无显著差异,门分类水平,被孢霉门(Mortierellomycota)和球囊菌门(Glomeromycota)是青枯病钝感桑树品种植株根际土壤中特有的优势真菌门; 而属分类水平,Apiotrichum、地丝菌属(Geotrichum)、足放线病菌属(Scedosporium)和腐质霉属(Humicola)等是青枯病易感桑树品种植株根际土壤中富集的特有优势真菌属。(2)青枯病易感桑树品种植株根际土壤中,缺失了被孢霉门、球囊菌门真菌,以及被孢霉属(Mortierella)、镰刀菌属(Fusarium)、曲霉菌属(Aspergillus)和毛壳菌属(Chaetomium)等具有生防功能的优势真菌门属,可能是其易感青枯病的重要原因。(3)根据真菌群落对同类环境资源的利用途径进行功能预测发现,青枯病易感桑树品种根际土壤中,富集了相对较多的病理营养型和腐生营养型真菌; 而青枯病钝感桑树品种根际土壤中,富集了相对丰富的共生营养型真菌。(4)特有真菌数量更为丰富的土壤真菌OTU分类水平,可能是青枯病钝感桑树品种田间表现出更强抗性的重要原因。可见,在青枯病钝感桑树品种植株根际土壤中,富集的被孢霉属、镰刀菌属、曲霉菌属和毛壳菌属等优势特异真菌属,具有作为拮抗桑树青枯病备选菌属的潜力。     

Evaluation of the strains of Acinetobacter and Enterobacter as potential biocontrol agents against Ralstonia wilt of tomato

Bacterial wilt (Ralstonia solanacearum) of tomato, Lycopersicon esculentum, causes a considerable amount of damage to tomato in Southern China. Biological control is one of the more promising approaches to reduce the disease incidence and yield losses caused by this disease. Based on antagonistic activity against R. solanacearum and three soil-borne fungal pathogens as well as biocontrol efficacy in the greenhouse, two bacterial strains Xa6 (Acinetobacter sp.) and Xy3 (Enterobacter sp.) were selected out of fourteen candidates as potential biocontrol agents. In order to find a suitable antagonist inoculation method, we compared the methods of root-dipping with soil-drenching in the aspects including rhizocompetence, biocontrol efficacy, and effect of promoting plant growth under greenhouse conditions. The drenching treatment resulted in a higher biocontrol efficacy and plant-yield increase, and this method was also easier to operate in the field on a large scale. Field trials were conducted for further evaluation of these two antagonistic strains. In both greenhouse and field experiments, the strain Xy3 had a better control effect against bacterial wilt than Xa6 did, while Xa6 caused higher biomass or yield increases. As recorded on the 75th day after treatment in two field experiments, biocontrol efficacy of Xy3 was about 65% in both field trials, and the yield increases caused by Xa6 were 32.4 and 40.7%, respectively, in the two trials. This is the first report of an Acinetobacter sp. strain used as a BCA against Ralstonia wilt of tomato.     

Integrated management of bacterial wilt (Ralstonia solanacearum) of ginger (Zingiber officinale) in Southwestern Ethiopia

Abstract

Ginger bacterial wilt (GBW) is a destructive disease of ginger in Ethiopia. Field studies were conducted to determine effect of integrated management of GBW, through host resistance and cultural practices, on wilt epidemics at Teppi and Jimma, southwestern Ethiopia in 2017. Treatments were factorial arranged in a randomised complete block design with three replications. Analysis of variance indicated that effect of variety, cultural practices and variety x cultural practice interactions significantly reduced GBW epidemic parameters and enhanced yield at both locations. Boziab recorded lower wilt incidence, area under disease progress curve and wilt progress rates than Local variety. Integration of lemon grass with soil solarisation and fertiliser reduced wilt incidence in Local variety up to 38.3% (Teppi) and 42.05% (Jimma) compared to the control on final wilt assessment date. In Boziab variety, integrated use of lemon grass with soil solarisation and fertiliser reduced wilt incidence up to 42.5% at Teppi and 33.85% at Jimma compared to the control on final date of wilt assessment. The overall results revealed that integrating cultural practices with host resistance are found effective to slow down GBW epidemics and improve ginger productivity; and thus, recommended for the study areas along with other crop management practices.     

Evaluation of neem seed powder for Fusarium wilt and Meloidogyne control on tomato

Fusarium wilt and root-knot are important diseases of tomato. The use of chemical is becoming less appealing because of the health implications. Also, the chemicals required are often not within the reach of farmers in most of the developing part of the world. This research is aimed at finding an alternative mode of control. Tomato variety Roma VF inoculated with Meloidogyne and Fusarium were treated with 2 g/kg soil neem seed powder in the screenhouse and 2 Mg ha ^{? 1} in the field. An untreated and Furadan treated plot in the field served as control. Neem seed powder significantly reduced the disease severity of Fusarium and root-knot in both screenhouse and field. Results suggest the possible use of neem seed powder for control of the root-knot nematodes - Fusarium wilt disease complex.     

Effectiveness of acibenzolar-S-methyl, fungicides and antibiotics for the control of brown eye spot, bacterial blight, brown leaf spot and coffee rust in coffee

This study was carried out to evaluate the potential of acibenzolar‐S‐methyl (ASM), combined or not combined with fungicides and antibiotics for the control of brown eye spot (Cercospora coffeicola) and bacterial blight (Pseudomonas syringae pv. garcae) in coffee seedlings, and ASM combined with conventional fungicide application schedules for the control of coffee rust (Hemileia vastatrix) and brown leaf spot (Phoma costarricencis) under field conditions in two coffee crops in the State of São Paulo, Brazil. ASM protected coffee seedlings against C. coffeicola when applied at the rates of 2.5 and 5 g of active ingredient per hectolitre of water (g a.i. hL^?1), providing 34–55% of disease control, and against bacterial blight, when applied at the rates of 2.5, 10 and 20 g a.i. hL^?1, with 38–57% of disease control. Tebuconazole (100 g a.i. hL^?1) and azoxystrobin (10 g a.i. hL^?1) showed the best results for brown eye spot control. Oxytetracycline + streptomycin, kasugamycin hydrochloride, oxytetracycline + metallic copper, copper oxychloride and mancozeb + copper oxychloride also controlled bacterial blight in levels similar to those shown by ASM. In the field experiments, all fungicide application schedules tested, cyproconazole (December, February, April), epoxiconazole (December, March), tetraconazole (December, February, April), cyproconazole (December, February) and azoxystrobin (January, March) were effective for coffee rust control and provided partial control of brown leaf spot. The results also showed that for all experiments, there was no synergistic effect of the combination of ASM with azoxystrobin, cyproconazole or cupric fungicides.