一株抗玉米纹枯病内生细菌的分离鉴定及其抗病促生作用

玉米纹枯病是玉米主要的真菌病害,从优良玉米品种川单13号中分离到一株对玉米纹枯病菌具有明显抑制作用并能够促进玉米生长的内生细菌.通过形态、生理生化特性分析以及16SrDNA序列同源性比较,鉴定该菌株为枯草芽孢杆菌.盆栽试验表明,菌株能够抑制玉米纹枯病的发生,抑菌率为 43.01%,促生试验表明,该菌能够显著促进玉米苗的生长,促生作用与植物生长刺激素(IAA)和效果相似,显示出良好的开发前景.     

一株水稻根内生拮抗细菌SM13的分离及鉴定

【背景】作物根内生细菌具有固氮、分泌激素、产生病原真菌抗性物质等特性,根系内生菌的分离及应用成为环境友好型防控技术研究的热点之一。近年来盐碱地水稻种植面积逐年增加,而关于盐碱地水稻根内生菌的分离与应用鲜有报道。【目的】从大庆盐碱地水稻根中分离内生细菌,筛选对植物真菌病害有拮抗作用的促生菌株,初步探讨其抑菌和促生功效,为进一步研究其抑菌和促生机理提供菌种资源。【方法】对水稻根表面灭菌后研磨涂布分离内生细菌,采用对峙培养法和改良Salkowski比色法筛选具有广谱抑菌效果并有分泌吲哚-3-乙酸(Indole-3-acetic acid,IAA)能力的菌株,通过形态鉴定、革兰氏染色、生理生化测定、16S rRNA结构基因以及srfA、ituA、fenB功能基因序列系统进化分析,确定细菌的分类地位。【结果】从水稻根部分离到一株内生细菌SM13,该菌株具有广谱性抑菌作用,对玉米新月弯孢菌、大豆菌核病菌、稻瘟病菌、禾谷镰刀菌的抑菌率分别为59.38%、78.13%、53.12%、37.50%,分泌IAA的能力为5.56±0.41μg/mL (n=6)。经形态学、生理生化试验结合系统进化分析初步鉴定SM13菌株属于枯草芽孢杆菌(Bacillus subtilis),该菌株在pH 11.0、盐浓度10%的NA培养基中生长良好,具有较高的耐盐碱性。【结论】水稻根内生菌SM13菌株具有耐盐碱性、促生和生防性能,可作为微生物农药及菌肥的材料。     

小麦内生细菌的分离及其对小麦纹枯菌的拮抗作用

利用涂布平板法从小麦根系中分离出8株内生细菌,从中筛选出1株对小麦纹枯菌(Rhizoctonia cerealis)具有拮抗作用的内生菌。室内测定该菌株培养液对小麦纹枯病菌的抑制作用,结果发现,小麦纹枯病菌在培养液中生长缓慢,培养6d后菌丝量与对照相比下降了89％,同时发现病菌菌丝生长畸形,出现断裂和细胞壁瓦解。双抗标记法测定该拮抗菌在小麦根系中的定殖情况,发现该菌能够在根系中长期定殖。初步的鉴定结果表明该菌为蜡样芽孢杆菌。     

一株种内拮抗的海洋枯草芽孢杆菌的分离与鉴定

从中国东海海域筛选到好氧耐盐菌株A01,此菌株显示出抗枯草芽孢杆菌和白色念珠菌的活性采取对该菌株形态特征、培养特征、生理生化特征和遗传特性进行研究的方法,结果表明此菌株与枯草芽孢仟菌（Bacillus subitilis）的特征一致;将此菌株的16S rDNA序列在GenBank中进行序列比对,结果亦显示其与Bacillus subitilis的16SrDNA的序列片段的相似性为100％;以相似性为基础构建系统发育树,分析表明该菌株与Bacillus subitilis同源关系最近最终得出结论为菌株A01是一株来源于海洋的枯草芽孢杆菌,且具有种内拮抗的特性。     

小麦内生细菌的分离及其对小麦纹枯菌的拮抗作用*

利用涂布平板法从小麦根系中分离出8株内生细菌,从中筛选出1株对小麦纹枯菌(Rhizoctoniacerealis)具有拮抗作用的内生菌。室内测定该菌株培养液对小麦纹枯病菌的抑制作用,结果发现,小麦纹枯病菌在培养液中生长缓慢,培养6d后菌丝量与对照相比下降了89%,同时发现病菌菌丝生长畸形,出现断裂和细胞壁瓦解。双抗标记法测定该拮抗菌在小麦根系中的定殖情况,发现该菌能够在根系中长期定殖。初步的鉴定结果表明该菌为蜡样芽孢杆菌。     

马铃薯立枯丝核菌拮抗菌QHZ11的实时荧光定量PCR快速检测与应用

【背景】植物根际促生菌(plant growth-promoting rhizobacteria,PGPR)在根际的定殖是其发挥作用的基础,直观有效的跟踪技术和定量方法是研究PGPR在根际原位分布规律的重要工具。【目的】建立一种马铃薯黑痣病病原菌——立枯丝核菌拮抗菌QHZ11的实时荧光定量PCR快速检测体系,并检测拮抗菌QHZ11在马铃薯根际的动态变化。【方法】根据GenBank中登录的类芽孢杆菌及近源菌株gyrB基因序列差异筛选特异性引物,优化反应条件;通过盆栽试验对马铃薯根际拮抗菌进行快速检测。盆栽试验设3个处理,T1:对照(无菌水,CK);T2:QHZ11菌悬液灌土(QHZ11);T3:将功能菌在有机肥中进行二次固体发酵制成生物有机肥(BOF11)。【结果】筛选出拮抗菌QHZ11的专用引物为gyrB-F/gyrB-R;建立的拮抗菌QHZ11实时荧光定量PCR检测方法特异性好、灵敏度高且重复性较好,线性相关系数为0.999 8,检测组内变异系数均在1%以内,扩增效率为0.9,可检测出1×103-1×1010copies/g-soil的拮抗菌,具有检出限低和扩增效率高的特点。盆栽试验...     

大豆内生细菌的分离及根腐病拮抗菌的筛选鉴定

内生细菌存在于健康植物体内,一些内生细菌具有促生长、抗病和固氮等生物学功能.本项研究采用化学药剂表面灭菌方法从黑龙江省大豆品种合丰25的根、茎、叶和种子中分离到大量内生细菌,其种群数量在根部最多,为3.4×103CFU/g,在叶部次之,为2.8×103CFU/g,在茎部和种子中最少,为2.9×102 CFU/g和1.4×102CFU/g.从121株内生细菌中筛选到31株对大豆根腐病菌Fusarium oxysporum f. sp.soybean具有较强抑制作用的拮抗内生细菌,其中菌株TF28抑菌谱广,抑菌率高,对不同植物的病原菌F. oxysporum的抑菌率为80.2%～96.7%.经形态、生理生化和16S rRNA鉴定为解淀粉芽孢杆菌(Bacillus amyloliquefaciens).     

一株拮抗立枯丝核菌的放线菌筛选、鉴定及生理特性

通过对峙实验,从采集自黄渤海海域的双齿围沙蚕(Perinereis aibuhitensis)中分离到一株内生放线菌SCF-18,并对其抑菌活性进行分析。SCF-18对立枯丝核菌(Rhizoctonia solani)和小麦根腐病菌(Bipolaris sorokiniana)都具有拮抗作用,且对立枯丝核菌生长的拮抗效果最为明显,生长抑制率为89.78%。抑菌试验结果表明:菌株SCF-18发酵滤液可以抑制立枯丝核菌丝的生长,发酵液浓度越高,抑制力越强;当发酵液浓度达到50%时,对两种病原菌的抑制率分别为89.78%和80.26%。菌株SCF-18生长特性试验结果表明:菌株SCF-18生长最适温度为30℃,最适pH值为7;放线菌SCF-18耐盐度可达5%。根据形态特征、培养特征、生理生化特性和16S rDNA序列分析,将放线菌SCF-18初步鉴定为淡紫灰链霉菌(Streptomyces lavendulae)。本研究发现,SCF-18菌株是防治立枯丝核菌等病原菌的潜在优良生防菌株,具有潜在的开发应用价值。     

1株拮抗水稻纹枯病菌鼠乳杆菌的筛选与鉴定

采用平板对峙法从浙江省金华市水稻田土壤中筛选获得1株拮抗水稻纹枯病菌的细菌QT-0304菌株,最大拮抗带宽达到20 mm。根据形态特征、生理生化特征、16S rRNA基因比对及进化树构树分析,鉴定QT-0304菌株为鼠乳杆菌（Lactobacillus murinus）。抗菌谱实验结果表明：QT-0304菌株对苹果腐烂病菌（Valsa mali）和杨树溃疡病病菌（ Botryosphaeria dothidea）均有较好的抑制作用,拮抗带宽分别达到34.5 mm和23.0 mm。     

香蕉炭疽病拮抗细菌的分离和初步鉴定

对36株从药用植物蛇足石杉中获得内生细菌进行香蕉炭疽病拮抗细菌筛选。采用对峙培养筛选法、碱基序列比对及同源性分析进行研究。结果获得2株对香蕉炭疽病有拮抗作用的菌株,其中JXS1-6和AHL1-1菌株的抑菌带宽达9 mm及4 mm。通过16S rDNA碱基序列比对及同源性分析,JXS1-6和AHL1-1均鉴定为伯克霍尔德属(Burkholderia),属于伯克霍尔德科(Burkholderiaceae),伯克霍尔德目(Burkholderiales),β-变形菌纲(Betaproteobacteria)。     

Morphological,pathological and molecular characterisation of rice sheath blight disease causal organism Rhizoctonia solani AG-1 IA in Egypt

Rice sheath blight disease caused by Rhizoctonia solani is considered a distractive soil-borne disease of rice production worldwide. The study aimed to determine the causal organism of sheath blight symptoms in Egyptian rice fields. Sheath blight symptoms were first observed in a small area during 2013, 2014 and 2016 seasons, later in a wide area of rice fields in 2016 to 2018 seasons. Pathogen identification was carried out based on morphological traits and internal transcribed spacer sequencing. Thirty-six isolates were identified as R. solani fungus. The isolates exhibited a wide range of variability in their morphological traits and virulence patterns. Five isolates were sequenced and aligned with Chinese isolates with 75–100% identity. This is the first report of R. solani AG-1 IA that associated with rice sheath blight in Egypt. Initiate a breeding program for disease resistance and integrated disease management procedures are important to keep the disease under control.     

Morphological and pathological variations of rice sheath blight inciting south Indian Rhizoctonia solani isolates

Frequent assessment of pathogen diversity is one of the most important criteria in designing disease management programmes. A study on diversity of field isolates of Rhizoctonia solani from sheath blight-infected rice fields of south India has been carried out. A total of 236 R. solani isolates were obtained from 45 locations in the surveyed area. Sclerotial features such as colour, size and shape and distribution pattern were varying among isolates. However, no other morphological features found to differ among isolates. Majority of the R. solani isolates were fast growers as they attained complete mycelial growth within 2 days in a 90-mm Petri plate and the emergence of sclerotial structures was seen even in 4 days of incubation. Selected 10 R. solani isolates exhibited considerable variations in pathogenicity on three different rice cultivars. Vellai ponni was found to be the most susceptible rice cultivar to all the field isolates of R. solani.     

两株棉花立枯病拮抗菌MH1和MH25的筛选与鉴定

从棉花根际分离了1277个细菌分离物, 以棉花立枯病病原真菌立枯丝核菌(Rhizoctonia solani Kuhn)为靶标菌, 通过平板对峙法获得25个具有拮抗性能的分离物, 其中MH1和MH25具有较强的拮抗性能, 且拮抗性能稳定, 具有较好的生防潜力。经过形态观察、生理生化特征分析及16S rDNA序列分析, MH1为短芽孢杆菌(Brevibacillus brevis), MH25为枯草芽孢杆菌(Bacillus subtilis)。MH1和MH25的16S rDNA序列在GenBank中注册号分别为: EF488102, EF488103。     

两株棉花立枯病拮抗菌MH1和MH25的筛选与鉴定

从棉花根际分离了1277个细菌分离物,以棉花立枯病病原真菌立枯丝核菌(Rhizoctonia solani Kuhn)为靶标菌,通过平板对峙法获得25个具有拮抗性能的分离物,其中MH1和MH25具有较强的拮抗性能,且拮抗性能稳定,具有较好的生防潜力.经过形态观察、生理生化特征分析及16S rDNA序列分析,MH1为短芽孢杆菌(Brevibacillus brevis),MH25为枯草芽孢杆菌(Bacillus subtilis).MH1和MH25的16S rDNA序列在GenBank中注册号分别为:EF488102,EF488103.     

Over-expression of the cloned rice thaumatin-like protein (PR-5) gene in transgenic rice plants enhances environmental friendly resistance to Rhizoctonia solani causing sheath blight disease

 A 1.1-kb DNA fragment containing the coding region of a thaumatin-like protein (TLP-D34), a member of the PR-5 group, was cloned into the rice transformation vector pGL2, under the control of the CaMV 35S promoter. The Indica rice cultivars, ‘Chinsurah Boro II’, ‘IR72’, and ‘IR51500’ were transformed with the tlp gene construct by PEG-mediated direct gene transfer to protoplasts and by biolistic transformation using immature embryos. The presence of the chimeric gene in T₀, T₁, and T₂ transgenic plants was detected by Southern blot analysis. The presence of the expected 23-kDa TLP in transgenic plants was confirmed by Western blot analysis and by staining with Coomassie Brilliant Blue. Bioassays of transgenic plants challenged with the sheath blight pathogen, Rhizoctonia solani, indicated that over-expression of TLP resulted in enhanced resistance compared to control plants. Received: 11 August 1998 / Accepted: 26 August 1998     

Functional validation of pathogenicity genes in rice sheath blight pathogen Rhizoctonia solani by a novel host-induced gene silencing system

Rice sheath blight, caused by the soilborne fungus Rhizoctonia solani, causes severe yield losses worldwide. Elucidation of the pathogenic mechanism of R. solani is highly desired. However, the lack of a stable genetic transformation system has made it challenging to examine genes' functions in this fungus. Here, we present functional validation of pathogenicity genes in the rice sheath blight pathogen R. solani by a newly established tobacco rattle virus (TRV)–host-induced gene silencing (HIGS) system using the virulent R. solani AG-1 IA strain GD-118. RNA interference constructs of 33 candidate pathogenicity genes were infiltrated into Nicotiana benthamiana leaves with the TRV-HIGS system. Of these constructs, 29 resulted in a significant reduction in necrosis caused by GD-118 infection. For further validation of one of the positive genes, trehalose-6-phosphate phosphatase (Rstps2), stable rice transformants harbouring the double-stranded RNA (dsRNA) construct for Rstps2 were created. The transformants exhibited reduced gene expression of Rstps2, virulence, and trehalose accumulation in GD-118. We showed that the dsRNA for Rstps2 was taken up by GD-118 mycelia and sclerotial differentiation of GD-118 was inhibited. These findings offer gene identification opportunities for the rice sheath blight pathogen and a theoretical basis for controlling this disease by spray-induced gene silencing.     

Differential expression of defense‐related proteins of rice and sheath blight symptoms in response to active and inactive Rhizoctonia solani toxin

The effects of the phyotoxin from the fungal pathogen Rhizoctonia solani, causing sheath blight on the expression of defense‐related proteins of rice were investigated. The toxin inactivated by chemical treatment and by the toxin‐inactivating enzyme α‐glucosidase produced by Trichoderma viride was used in the study along with the active toxin. Toxin inactivated by T. viride α‐glucosidase and sodium periodate caused significantly less damage and electrolyte leakage to test plants. The active toxin and the pathogen induced chitinase and ß‐1,3‐glucanase synthesis in rice plants, while the inactivated toxin did not have any effect on the expression of these pathogenesis‐related proteins. The toxin was found to suppress the peroxidase activity 72 h after inoculation and the inactivated toxin restored the activity as that of untreated plants. There was no remarkable change in phenylalanine ammonia lyase activity in rice sheath treated with both the forms of the toxin.     

A host-specific toxin of Rhizoctonia solani triggers superoxide dismutase (SOD) activity in rice

Changes in the activity of superoxide dismutase (SOD) in rice in response to treatment with Rhizoctonia solani toxin and/or R. solani elicitor were studied. Treatment of rice leaf sheaths with R. solani-toxin significantly increased the SOD activity within 12?h and the maximum enzyme activity was detected 36?h after treatment at which period a fourfold increase in SOD activity was recorded compared to control plants. Isozyme analysis indicated that five new SOD isozymes (SOD-1, SOD-3, SOD-6, SOD-7 and SOD-8) were induced in rice 1?–?2 days after toxin treatment. In elicitor-treated rice leaf sheaths, SOD-2 increased in activity 1?–?5 days after treatment. Pretreatment of rice leaf sheaths with elicitor suppressed the toxin-induced accumulation of SOD.