Seedling Petri-dish inoculation method:A robust,easy-to-use and reliable assay for studying plant-Ralstonia solanacearum interactions

Ralstonia solanacearum causes a lethal bacterial wilt disease in many crops,leading to huge losses in crop production every year.Understanding of plant-R.solanacearum interactions will aid to develop efficient strategies to control the disease.As a soilborne pathogen,R.solanacearum naturally infects plants via roots.A huge limitation in studying plant-R.solanacearum interactions is the large variation of R.solanacearum infection assay due to the variable soil conditions and uneven inoculum exposure.Here,we developed a robust and reliable Petri-dish inoculation method which allows consistent and stable infection in young plant seedlings.This method is easy to use,takes about only 10 days from seed germination to the completion of inoculation assay,and requires less inoculum of bacteria as well as growth chamber space.We proved the efficacy of the seedling Petri-dish inoculation method by analyzing plant defense primed by molecular patterns,resistance of defense-related plant mutants,and virulence of R.solanacearum mutants.Furthermore,we demonstrated that the seedling Petri-dish inoculation method can be applied to other host plants such as tobacco and has great potential for high-throughput screening of resistant plant germplasms to bacterial wilt in the future.

Effect of K1, K2 Anti-Bacterial Agents on Tobacco Ralstonia Solanacearum

The tobacco Ralstonia Solanacearum were both cultured on nutrient agar plates and inoculated in seedling stage of tobacco, then treated with K1 and K2, two anti-bacterial agents, at a serial con-centrations to study their inhibitory efficiency. The result indicated that K1 can inhibit R. Solanacearum growth entirely, at the concentration range from 1/50 to 1/5000. K2 can reach the same result at the concentration range from 1/50 to 1/50000. Compared with the control plates, K1, at the concentration 1/50000, had no significant differences, and the average number of colony per plate was 112-115. The immature tobacco shown wilt as soon as inoculated with R. Solanacearum, and recovered gradually after using K1, K2. The densities of microbial suspension, handled by K1, K2 within 10 hs, were both significantly lower than the controlled ones. The optical microscopy also shown that handled microbial body differed from the controlled, whose body was regular short, rod shape as opposed to the handled ones with irregular rod shape and damaged body. All the results indicated that K1 and K2 both had inhibitory effects on tobacco R. Solanacearum, and K2 was more efficient than K1.

Analysis of Meteorological Epidemic Factors and Soil Improvement Controlling Technology of Tobacco Bacterial Wilt (Ralstonia solanacarum)

[Objective] The paper was to analyze the meteorological epidemic factors for occurrence and prevalence of tobacco bacterial wilt （ Ralstonia solanaca- rum）, and to study control effects of different soil conditioners on the bacterial disease in Gacligongshan demonstration area of green, ecological, high quality tobac- co leaf production. [Method] The plots attacked by tobacco bacterial wilt over the years were selected and the incidence of the disease was periodically surveyed in tobacco growth period in 2012, 2103 and 2014, respectively. 10 d Effective accumulated temperature and rainfall were counted according to the meteorological data, and the relationship between meteorological factors and disease index was analyzed. The control effects of three kinds of soil conditioners ＂Zhuanggenfeng＂, refined fulvic acid and lime on tobacco bacterial wilt were tested. [ Result] The analysis results of meteorological factors showed that 10 d effective accumulated temperature and rainfall were positively correlated to disease index. The variation curve of 10 d effective accumulated temperature and rainfall reflected the change trend of disease index. The pH values were increased by 0.57, 0.50 and 0.72 respectively after applying ＂Zhuanggenfeng＂, refined fulvic acid and lime. The aver- age control effects on tobacco bacterial wilt were 60.74% -62. 18%, 53.05% -59.53%, and 48.59% -58.53%, respectively. [ Conclusion] 10 d Effective accumulated temperature and rainfall could be used as important reference for disease forecasting and controUing. The usage of soil conditioner has a certain preven- tion and control effect on tobacco bacterial wilt disease by forming soil conditions conducive to flue-cured tobacco growth but adverse to disease survival, which is an effective auxiliary method against the disease.

Silicon impacts on soil microflora under Ralstonia Solanacearum inoculation

Silicon(Si) can increase plant resistance against bacterial wilt caused by Ralstonia solanacearum and enhance plant immune response. However, whether Si alleviates soil-borne disease stress through altering soil microbial community component and diversity is not clear. In this study, effects of Si application under R. solanacearum inoculation with or without plant on soil bacterial and fungal communities were investigated through high-throughput pyrosequencing technique. The results showed that Si addition significantly reduced bacterial wilt incidence. However, Si did not reduce the amount of R. solanacearum in rhizosphere soil. Principal components analysis showed that soil microbial community composition was strongly influenced by Si addition. Total 63.7% bacterial operational taxonomic units(OTUs) and 43.8% fungal OTUs were regulated by Si addition regardless of the presence of tomato plants, indicating the independent effects of Si on soil microbial community. Si-added soil harbored a lower abundance of Fusarium, Pseudomonas, and Faecalibacterium. Our finding further demonstrated that exogenous Si could significantly influence soil microbial community component, and this may provide additional insight into the mechanism of Si-enhanced plant resistance against soil-borne pathogens.

Effect of Integrated Use of Inorganic Fertilizer and Organic Manures on Bacterial Wilt Incidence (BWI) and Tuber Yield in Potato Production Systems on Hill Slopes of Central Kenya

Bacterial wilt (BW) caused by Ralstonia solanacearum is one of the most damaging diseases of potato (Solanum tuberosum L.) in Kenya and worldwide. In Kenya, potato tuber yield losses due to BW infection are estimated at 50 ~ 100%. Low soil fertility is also one of the most important constraints limiting potato production in central Kenya highlands. Farmers tackle this problem through use of inorganic fertilisers and organic manures, both of which amend the soil environment to influence bacterial wilt development. Undecomposed organic manures can also introduce the pathogen into a clean field. Between short rains 1999 and 2000, 10 on-farm extension-researcher- farmer-designed and farmer-managed trials were done at Kianjuki catchment in Embu District. The objective was to use farmers?participatory research approach and select the most suitable organic and inorganic fertiliser combination(s) with lowest BWI and acceptable usable tuber yields, and also to demonstrate use of some components of integrated disease management methods in reduction of disease incidence and spread. Seven treatments were proposed, presented to the farmers for discussion and the most relevant four were selected for evaluation. A newly released potato variety 慉sante?was planted during the short rains 1999 and long rains 2000. BWI didn抰 result in significant differences between treatments but the tuber yields were significantly different in short rains of 1999 and 2000. During short rains 2000, both BWI and tuber yields and unusable tubers differed significantly between treatments. The results confirmed that well- decomposed manures or manures from pathogen-free areas can be used in combination with inorganic fertilisers to improve soil fertility and potato tuber yields in smallholder farms without influencing BWI. Use of certified seed tubers in pathogen free field and following recommended field sanitation measures resulted in apparently bacterial wilt free crop. Considering the high cost of inorganic fertiliser and its negative effects on the environment, reduced usage at half the recommended rates combined with half rates of FYM is feasible option friendly to the farmer, soil and environment. The interviewed farmers also ranked the option as the most appropriate combination for soil fertility improvement for potato production in smallholder farms.

Improvement of Bio-Efficacy to Reduce Bacterial Wilt Complex Disease in Tomatoes through Bacillus amyloliquefaciens and Pseudomonas fluorescens under Field Conditions

Bacterial wilt complex disease of tomato(Solanum lycopersicum L.)was incited jointly by bacterial wilt pathogen Ralstonia solanacearum and Meloidogyne incognita worldwide.Bio-efficacy of bacterial antagonists i.e.B.amyloliquefaciens DSBA-11 and P.fluorescens DTPF-3 was studied against the wilt disease complex in tomato at National Phytotran facility Indian Agricultural Research Institute(IARI),New Delhi,at 26±2°C.Minimum wilt disease incidence(26.00%)with the highest bio-control efficacy(64.15%),less juvenile population(19.33 J2/g of soil)of M.incognita was recorded in the combined application of DTPF-3+DSBA-11 after 30 d of inoculation under glasshouse conditions.In a field study,minimum bacterial wilt disease incidences 19.0%and 20.4%were recorded in the bleaching powder treatment followed by mixed application of DSBA-11+DTPF-3,19.6%and 21.2%wilt incidence in 2014 and 2015 respectively.However,a reduction of root-knot gall index was recorded a maximum of 59.76%and 69.62%in DSBA-11+DTPF-3 treated plants followed by 54.88%and 60.13%over control in DTPF-3 treatment in 2014 and 2015 respectively.The yield of tomato fruit was increased over control by 17.48%and 16.97%in 2014 and 2015 respectively under field conditions.A combination of P.fluorescens DTPF-3+B.amyloliquefaciens DSBA-11 suppressed bacterial wilt and root-knot diseases and also increased the yield of the tomato fruit significantly(p<0.05)under field conditions.

河南省花生青枯病菌的分子鉴定及其生物学特性研究

为了明确河南省花生青枯病的病原菌分类属性,对采自河南省内不同市的30个青枯病菌株在16S rDNA序列、碳水化合物利用、致病性、演化型及序列变种等方面进行了鉴定。30个青枯病菌株的16S rDNA测序结果表明,引起河南花生青枯病的病原为茄科雷尔氏菌(Ralstonia solanacearum);所有青枯病菌株可侵染茄子、辣椒、马铃薯、烟草和番茄,但不侵染姜,属于生理小种1号;根据能否利用3种双糖和3种己醇的能力,可将其中4个菌株归于生化型Ⅱ,10个菌株归于生化型Ⅲ,16个菌株归于生化型V;所有青枯病菌株均能用多重PCR扩增得到144 bp演化型Ⅰ特异条带和280 bp茄科雷尔氏菌特异条带,表明青枯病原菌均属于茄科雷尔氏菌演化型Ⅰ,即亚洲组13;利用egl基因的系统发育进化分析表明,来自河南的30个菌株与Gx525、Ah-XnJn-12-6、HA2-1聚为一支,属于序列变种14。

茄子青枯病发生率与田间生态因子的相关性分析

为了解析茄子青枯病发生率与田间生态因子的关系,在厦门同安茄子青枯病发病典型区,安装了农业生境野外数据观测装备,采集气温、地温、相对湿度、雨量、太阳辐射、光合有效辐射、光照度、CO_(2)浓度和土壤容积含水率等生态因子数据,并在营养生长期和生殖生长期调查茄子青枯病发病情况和青枯病原的分布特性。结果表明:茄子营养生长期的气温(28.6℃)、地温(30.1℃)和相对湿度(66.17%),均适宜青枯病发生;茄子在营养生长期的发病率(7.90%)和病情指数(5.40)大于生殖生长期的发病率(3.43%)和病情指数(2.47);青枯菌在发病2级的植株及根际土壤中分布最多,分别为营养生长期的81.80×10^(5) cfu·g^(−1)和生殖生长期的99.31×10^(5) cfu·g^(−1);强致病力青枯菌在发病植株和根际土壤中的分布量分别大于104 cfu·g^(−1)和105 cfu·g^(−1)。茄子青枯发病率与气温、地温、相对湿度、雨量、光照辐射和二氧化碳浓度呈极显著正相关(P<0.01),与光照度和土壤容积含水率呈显著正相关(P<0.05)。研究结果为青枯病预测预报技术的建立及病害的有效防控提供依据。

华南地区茄科作物青枯病发生与病原菌分布特性分析

调查我国华南地区番茄、茄子和辣椒等茄科作物青枯病害发病情况,采集健康植株和青枯病发病株及其根际土壤样本,进行病原菌的分离鉴定、致病力测定和分布特性分析。结果表明:番茄、茄子和辣椒发病率最高的地区分别是海南陵水、福建晋安和福建邵武,其生育期内平均发病率分别达20.01%、5.24%和23.33%。从不同地理来源的茄科作物中,共分离鉴定出86株青枯菌。进一步利用弱化指数(Attenuation index,AI)对分离的青枯菌进行致病力划分,其中7株为无致病力菌株(AI>0.75),13株为过渡型菌株(0.65≤AI≤0.75),66株为强致病力菌株(AI<0.65)。研究青枯菌的分布特性发现,对于不同寄主,青枯菌分布特性均是病株及其根际土壤分布数量显著多于健康植株及其根际土壤,且分布数量均是土>根>茎,此外,调查的茄科作物中,青枯病发病株土壤青枯菌分布数量均大于106 cfu·g^(-1),青枯病发病株根和茎青枯菌分布数量均大于105 cfu·g^(-1)。

青枯菌Ⅲ型效应蛋白调控植物免疫研究进展

青枯菌(Ralstonia solanacearum)通常从寄主植物根部侵染维管束系统,引发青枯病(Bacterial wilt),造成植物产生不可逆的萎蔫、死亡。青枯病是一种毁灭性土传细菌病害,目前已成为制约我国茄科作物生产的主要病害之一。Ⅲ型分泌系统(TypeⅢsecretion system,T3SS)在青枯菌侵染寄主过程中发挥重要作用,青枯菌利用T3SS向寄主细胞分泌大量Ⅲ型效应蛋白(TypeⅢeffectors,T3Es)以干扰寄主的免疫反应。国内外学者致力于探索青枯菌如何通过识别寄主体内的靶标蛋白来干扰寄主细胞、调控寄主免疫功能。因此,对青枯菌T3Es靶向识别的植物蛋白进行鉴定有助于了解青枯菌T3Es的生物学功能、青枯菌的致病过程,同时也有助于挖掘寄主中青枯病抗性相关蛋白及其作用机制。尽管大多数T3Es功能仍然未知,但目前已报道的青枯菌T3Es可通过多种分子机制干扰植物先天免疫、诱导植物发生超敏反应、影响植物代谢和激素信号传导通路等来调节寄主抗青枯病能力。该文综述青枯菌T3Es的特征、功能鉴定方法及其参与调控青枯菌致病性及植物免疫机制的研究进展,并对青枯菌T3Es与寄主互作机制研究进行展望,有助于更加深入地了解青枯菌的致病机理及寄主免疫系统的应答机理,为青枯菌诱导寄主抗性机制的解析及青枯病的防治提供有效参考。

福建猕猴桃细菌性枯萎病的病原菌鉴定

为明确近年来在福建省宁德市蕉城区石后乡猕猴桃苗圃新发生的一种细菌性病害病的原菌,并进一步探讨其发生流行规律,采用稀释分离法对采集病株进行病原菌的分离和纯化,对获得的细菌菌株进行致病性测定,通过柯赫氏法则验证、常规的细菌生物学特性、生理生化反应、Biolog鉴定、16S rDNA和内切葡聚糖酶基因(egl)序列分析对病原菌进行分类鉴定。结果表明,从发病猕猴桃病株上获得9株细菌菌株,将其接种在健康的猕猴桃植株后,其发病症状与田间自然发病症状基本一致,且从接种后病株的茎秆和根部又重新分离到与原菌落形态相同的细菌。柯赫氏法则证实这9株细菌菌株为猕猴桃细菌性枯萎病的致病菌。这9株菌株在NA培养基上的菌落形态一致,均呈不规则型、扁平,并逐渐向四周扩散,不产生粘稠状物质,不会使培养基变色;在TTC培养基上,菌落颜色呈暗红色,产生可扩散至培养基中的红褐色色素,其流动性较差;在YDC培养基上,菌落呈乳白色。经综合分析,这9株细菌菌株均被鉴定为假茄科雷尔氏菌(Ralstonia pseudosolanacearum),生化型Ⅲ和演化型Ⅰ(亚洲组),序列变种14。这是首例青枯菌侵染猕猴桃的报道。以上研究结果为制定猕猴桃细菌性枯萎病精准有效的综合防控提供了理论依据。

番茄青枯病病原菌生物学特性及致病机制研究进展

由青枯雷尔氏菌引起的青枯病给番茄产业发展带来了严重挑战,青枯病的侵染造成番茄产量和质量严重受损。在总结番茄青枯病病原菌生物学特性的基础上,分析了番茄青枯病病原菌的致病机理及其对作物产量和质量的危害,阐述了青枯菌的致病效应蛋白,提出了番茄青枯病生物防治方法,以期为全面了解和有效防治番茄青枯病提供参考。

无致病力青枯菌FJAT-a RS01的固态发酵及对茄果类蔬菜青枯病的防治效果

利用无致病力青枯菌研发植物疫苗防治青枯病是植物病害防治研究中的新途径。无致病力青枯菌FJAT-aRS01具有防效高和稳定遗传等特性。为了进一步开发利用该菌株,本研究以巨菌草渣为其主要发酵培养基,通过正交试验优化培养基配方和发酵条件,固态发酵FJAT-a RS01,并进行质量检测。结果表明,优化后菌株FJAT-aRS01固态发酵培养基配方为巨菌草渣36.36%、玉米粉27.27%、米糠27.27%和稻壳9.09%;发酵条件为接种量15%(10^(8)CFU/mL),料水质量比为1:0.8,装袋量为150 g/袋,发酵时间为48 h;在该发酵条件下,FJAT-aRS01的固态发酵物活菌数可达到1.80×10^(9)CFU/g,其营养成分含量超过微生物肥料的国家标准(NY/T 798-2015);FJAT-a RS01固态发酵物浸提液的50倍稀释液能促进番茄种子萌发,其100倍稀释液能促进辣椒和茄子种子萌发;在栽培基质中添加质量百分比≤15%的FJAT-aRS01固态发酵物能促进植株生长,添加质量百分比25%的FJAT-a RS01固态发酵物对于番茄、辣椒和茄子青枯病的防效均达75%以上。综上所述,无致病力青枯菌FJAT-aRS01的固态发酵物具有促生防病功能,具备良好的应用前景。

花生青枯病及其土壤微生态调控研究进展

由茄科雷尔氏菌(Ralstonia solanacearum)引起的青枯病是世界范围内广泛传播、危害严重且难以防治的毁灭性土传病害之一。花生是我国重要的油料和经济作物,也是青枯病危害严重的作物之一。近年来,连续种植导致花生青枯病发生进一步加剧,严重威胁了花生产业的发展。本文以花生青枯病的危害及其土壤微生态调控为切入点,梳理了花生青枯病的发生现状、病原菌概况、发生条件与作用机制以及主要危害与防治措施等。首先,对茄科雷尔氏菌的分类方法和致病机理进行了系统、完整地梳理,总结了茄科雷尔氏菌的4种主流分类方法,并绘制了其发病机制图解。其次,我们重点从土壤微环境、土壤微生物两个方面分析了花生连作和青枯病发病土壤区系特征,并提出相应的土壤微生态调控对策,包括调控土壤理化性质、调控土壤养分、施用化学与生物农药、引入生防菌株等。最后,我们对基于土壤微生态调控的花生青枯病可持续防治进行展望,旨在为花生青枯病防治及花生产业的高质量发展提供参考。

五种药剂对烟草青枯病菌的抑制活性及碳代谢的影响

由茄科劳尔氏菌Ralstonia solanacearum引起的烟草青枯病是烟叶生产上的重要病害之一,严重影响烟叶的产量和品质。为筛选高效防治烟草青枯病的药剂,本研究采用平板菌落计数法测定了中生菌素、土霉素、噻霉酮、春雷霉素和氯溴异氰尿酸对茄科劳尔氏菌的抑制活性,并通过Biolog GENⅢ微平板法分析了上述5种药剂胁迫下茄科劳尔氏菌的碳代谢情况和对化学物质的敏感性差异。结果表明:5种药剂均能抑制茄科劳尔氏菌的生长,抑制活性从强到弱依次为中生菌素>土霉素>噻霉酮>春雷霉素>氯溴异氰尿酸,对应的EC_(50)值分别为0.24、0.74、2.84、7.95和273.99 mg/L。Biolog GENⅢ碳代谢测定结果显示:茄科劳尔氏菌能利用Biolog GENⅢ微平板中糖类及氨基酸类等71种碳源,但在药剂胁迫下,该菌对碳源的代谢受到了不同程度的抑制,其中抑制程度最显著的是氨基酸、己糖酸、羧酸、酯和脂肪酸类碳水化合物;随着5种药剂质量浓度增加,在6 mg/L中生菌素、8 mg/L土霉素、30 mg/L春雷霉素和5738 mg/L氯溴异氰尿酸胁迫下,茄科劳尔氏菌对Biolog GENⅢ微平板中65、18、60和7种碳源的代谢强度分别降低,同时对6、53、10和60种碳源的代谢强度增强;在8 mg/L噻霉酮胁迫下,茄科劳尔氏菌对Biolog GENⅢ微平板中71种碳源的代谢强度均降低。此外,在不同浓度的5种药剂胁迫和无药剂处理时,茄科劳尔氏菌对Biolog GENⅢ微平板中23种化学物质的敏感性不同,其对低浓度NaCl敏感性较低,而对低pH值更敏感。本研究结果可为烟草青枯病化学防控药剂的选择及其高效利用提供参考。

丛枝菌根真菌提高感染青枯菌番茄根际土壤细菌群落多样性和稳定性及有益菌属相对丰度

【目的】青枯病是由茄科雷尔氏菌(Ralstonia solanacearum,亦称青枯菌)诱导产生的一种高温高湿型土传病害,土壤温度高、湿度大时易于青枯菌的繁殖进而引发青枯病。丛枝菌根真菌(arbuscular mycorrhiza,AM)可能通过调控根际微生物区系对病原体产生影响,我们研究了AM真菌对青枯菌入侵条件下土壤细菌群落的影响。【方法】以番茄(Solanum lycopersicum)为试材进行盆栽试验,供试AM真菌为摩西管柄囊霉(Funneliformis mosseae)M47V,供试病原菌为茄科雷尔氏菌QL-RS 1115(GenBank:GU390462)。催芽5日的番茄种子,接种AM菌剂的为菌根苗,未接种AM真菌的为非菌根苗。在番茄幼苗生长30天时,一半菌根苗和非菌根苗接种青枯菌,另一半不接种青枯菌,共4个处理。在接种青枯菌后1天和14天,采集番茄样品,采用抖土方法采集根际土壤,利用实时荧光PCR分析番茄根际青枯菌数量,采用16S rRNA高通量测序探究土壤细菌群落多样性和结构稳定性。【结果】在接种青枯菌初期(1天),非菌根苗接种青枯菌(TR–AMF)和菌根苗接种青枯菌(TR+AMF)两组处理的根际土壤细菌群落结构发生明显改变,Chao1指数、Shannon指数和Simpson指数显著降低(P<0.05),共现网络的节点数和连接数明显减少,模块化程度降低,共现网络简化表明细菌群落结构的稳定性降低。接种青枯菌14天后,不动杆菌属(Acinetobacter)、鞘氨醇单胞菌属(Sphingomonas)、溶杆菌属(Lysobacter)、假单胞菌属(Pseudomonas)等有益细菌属在感染青枯菌的番茄根际富集,细菌共现网络的节点数和连接数增加,模块化程度提高,表明细菌群落稳定性得到恢复。与非菌根苗相比,菌根苗接种青枯菌(TR+AMF)和菌根苗未接种青枯菌(TN+AMF)两个处理番茄根际土壤中青枯菌丰度显著降低(P<0.05)。AM真菌显著提高Chao1指数和Shannon指数(P<0.05),提高了感染青枯菌番茄根际土壤中黄杆菌属(Flavobacterium)、黄色土源菌属(Flavisolibacter)、噬胞菌属(Cytophaga)和苔藓杆菌属(Bryobacter)的相对丰度,同时增加了共现网络的节点数和连接数,并促进番茄根际细菌物种之间的良性互作,提高细菌网络的复杂程度。【结论】感染青枯菌的番茄根际会富集不动杆菌属(Acinetobacter)、鞘氨醇单胞菌属(Sphingomonas)、溶杆菌属(Lysobacter)、假单胞菌属(Pseudomonas)等有益菌属以提高其抗病性,恢复细菌多样性和群落稳定性。接种AM真菌可显著降低番茄根际土壤中青枯菌的丰度,特别是侵染青枯菌后提高番茄根际的黄杆菌属(Flavobacterium)、黄色土源菌属(Flavisolibacter)、噬胞菌属(Cytophaga)和苔藓杆菌属(Bryobacter)的相对丰度,进而抑制土壤中青枯菌的生长,并通过提高细菌的多样性和丰富度,促进番茄根际细菌物种之间的稳定共生和良性互作,从而提高细菌群落对青枯菌的抵抗能力。

青枯劳尔氏菌Ⅲ型效应子的致病和无毒机制

青枯劳尔氏菌(简称“青枯菌”)是一种危害十分严重的植物病原细菌,其引起的植物青枯病严重影响番茄和马铃薯等作物的健康生产。青枯菌寄主种类广泛,而且能够通过基因水平转移和基因重组获得新毒力,以扩展寄主范围。青枯菌的致病机制复杂,Ⅲ型分泌系统(typeⅢsecretion system,T3SS)是关键的致病因子,其分泌的Ⅲ型效应子(typeⅢeffectors,T3Es)在致病过程中发挥重要功能,从不同层面抑制寄主先天免疫反应;此外,植物寄主也能识别青枯菌的效应子,激活效应子触发的免疫反应并产生抗病性。本文对青枯菌Ⅲ型效应子的毒性机制与无毒功能进行了讨论和总结,为深入了解青枯菌的致病机制和植物抗青枯病的机制提供了思路。

维管束木质化调控植物抗青枯病的研究进展

细菌性青枯病是由青枯劳尔氏菌(Ralstonia solanacearum)(以下简称“青枯菌”)引起的一种典型的维管束病害,发病后严重影响作物产量与品质。选育抗病品种是从根本上解决青枯病危害的最有效措施,而了解植物免疫反应的分子机制是抗病育种的基础。越来越多的研究表明,维管束免疫具有细胞类型特异性。植物识别青枯菌后,通过信号传导诱导维管束细胞壁木质化,形成植物抵御青枯菌扩散的主要屏障。木质素的合成受到精细的调控,其关键合成酶基因在转录、翻译、时空特异性表达等不同方面受到调控。本文综述了植物对青枯菌的识别和信号传导机制,以及诱导维管束木质化调控青枯病抗性的研究进展,包括诱导木质素合成基因表达、木质素单体转运和聚合、不同木质素类型产生等分子机制,以期为利用维管束木质化改性技术进行青枯病的抗性育种提供理论依据。

番茄青枯病生防芽胞杆菌的筛选与鉴定

为了有效利用芽胞杆菌资源,本研究采用抑菌圈法从不同地理来源的芽胞杆菌中筛选出24个对青枯雷尔氏菌具有拮抗作用的菌株。其中,6个菌株对青枯雷尔氏菌的抑菌圈直径大于14.00 mm,菌株FJAT-11709的抑菌圈直径最大,为14.78 mm。盆栽试验比较了6个菌株对番茄青枯病的防治效果,结果表明,菌株FJAT-20261和FJAT-19700防效最好,分别达72.73%和67.77%。通过形态特征、生理生化测定及16S r RNA基因序列分析,菌株FJAT-20261和FJAT-19700分别被鉴定为耐寒短杆芽胞杆菌和特基拉芽胞杆菌。本文报道这2种芽胞杆菌对青枯雷尔氏菌具有拮抗作用,为青枯病的生物防治提供了新的菌株资源。

烟草根际细菌铜绿假单胞菌swu31-2的定殖能力及其对烟草青枯病的防治作用

从重庆黔江烟草田间分离获得一株烟草青枯菌拮抗菌株Pseudomonas aeruginosaswu31-2(简称swu31-2)。采用逐步提高药物浓度的方法,筛选获得了抗链霉素300μg/mL对烟草青枯病菌拮抗活性稳定的swu31-2突变菌株。采用灌根接种法,研究其在烟草根、茎和叶表面及内部的定殖能力及其对烟草青枯病的防治作用。结果表明,swu31-2能在烟草各组织的表面及内部定殖。该菌株在烟草各组织内部的数量均表现为"由增到减"的趋势。在接种后第8天定殖数量达到最高峰,随后有所下降;到第20天各组织内的数量仍然维持较高水平(105cfu/g以上)。同时,在接种20 d后,烟草的根、茎和叶的表面仍然可以检测到swu31-2的存在。盆栽试验结果表明,swu31-2的菌液和活性物质对烟草青枯病均有一定的防治效果。其中先施swu31-2菌液和活性物质粗提物的防效好于农用链霉素(51.25%),分别为60.87%和60.32%,而后施菌液和活性物质粗提物的防效也分别达39.50%和20.90%。