Induction of systemic resistance,root colonisation and biocontrol activities of the rhizospheric strain of <Emphasis Type="Italic">Serratia plymuthica</Emphasis> are dependent on N-acyl homoserine lactones

Quorum sensing regulation, mediated by N-acyl homoserine lactone signals, produced by strain Serratia plymuthica HRO-C48 isolated from the rhizosphere of oilseed rape, was found to be responsible for this strain’s ability to produce the broad spectrum antibiotic pyrrolnitrin. In this study, we have shown that some other biocontrol-related traits of strain HRO-C48, such as protection of cucumbers against Pythium apahnidermatum damping-off disease, induced systemic resistance to Botrytis cinerea grey mold in bean and tomato plants, and that colonisation of the rhizosphere also depends on AHL signalling. The results prove that quorum sensing regulation may be generally involved in interactions between plant-associated bacteria, fungal pathogens and host plants.     

Suppression of rice blast using freeze-killed mycelia of biocontrol fungal candidate MKP5111B

Several applications of the suppressive fungus MKP5111B, isolated from the phylloplane of rice plants, were tested in an effort to control rice blast disease. Three treatments with MKP5111B [living (Std), killed with liquid nitrogen (FR), and autoclaved (AC)] were either sprayed onto rice seedlings or mixed into seed-sown soil. Three weeks after spraying and 4 weeks after the soil application, we introduced Magnaporthe oryzae, the causal agent of rice blast, into our systems. The Std and FR treatments suppressed rice blast, but the AC treatment proved ineffective. Although a suppressive effect was seen on new leaves, no mycelium of MKP5111B was seen. The fungus thus may have induced a systemic resistance in the rice plants. A substance from MKP5111B, such as elicitor molecule(s) are likely responsible for the induced resistance.     

Suppression of fusarium wilt of radish by co-inoculation of fluorescentPseudomonas spp. and root-colonizing fungi

In an earlier study, treatment of radish seed with the bacteriumPseudomonas fluorescens WCS374 suppressed fusarium wilt of radish (Fusarium oxysporum f. sp.raphani) in a commercial greenhouse [Leemanet al., 1991b, 1995a]. In this greenhouse, the areas with fusarium wilt were localized or expanded very slowly, possibly due to disease suppressiveness of the soil. To study this phenomenon, fungi were isolated from radish roots collected from the greenhouse soil. Roots grown from seed treated with WCS374 were more abundantly colonized by fungi than were roots from nonbacterized plants. Among these were several species known for their antagonistic potential. Three of these fungi,Acremonium rutilum, Fusarium oxysporum andVerticillium lecanii, were evaluated further and found to suppress fusarium wilt of radish in a pot bioassay. In an induced resistance bioassay on rockwool,F. oxysporum andV. lecanii suppressed the disease by the apparent induction of systemic disease resistance. In pot bioassays with thePseudomonas spp. strains, the pseudobactin-minus mutant 358PSB^– did not suppress fusarium wilt, whereas its wild type strain (WCS358) suppressed disease presumably by siderophore-mediated competition for iron. The wild type strains of WCS374 and WCS417, as well as their pseudobactin-minus mutants 374PSB^– and 417PSB^– suppressed fusarium wilt. The latter is best explained by the fact that these strains are able to induce systemic resistance in radish, which operates as an additional mode of action. Co-inoculation in pot bioassays, ofA. rutilum, F. oxysporum orV. lecanii with thePseudomonas spp. WCS358, WCS374 or WCS417, or their pseudobactin-minus mutants, significantly suppressed disease (except forA. rutilum/417PSB^– and all combinations with 358PSB^–), compared with the control treatment, if the microorganisms were applied in inoculum densities which were ineffective in suppressing disease as separate inocula. If one or both of the microorganism(s) of each combination were applied as separate inocula in a density which suppressed disease, no additional suppression of disease was observed by the combination. The advantage of the co-inoculation is that combined populations significantly suppressed disease even when their individual population density was too low to do so. This may provide more consistent biological control. The co-inoculation effect obtained in the pot bioassays suggests that co-operation ofP. fluorescens WCS374 and indigenous antagonists could have been involved in the suppression of fusarium wilt of radish in the commercial greenhouse trials.Abbreviations CFU colony forming units - KB King's B - PGPR plant growth-promoting rhizobacteria - CQ colonization quotient     

Effects of light conditions on prodigiosin stability in the biocontrol bacterium Serratia marcescens strain B2

Serratia marcescens strain B2 is a potential biocontrol agent that produces the antibiotic pigment prodigiosin. When this strain was incubated under white or blue light conditions (<100µmol m^–2s^–1), prodigiosin concentration in bacterial cells decreased, but growth did not. However, red and far-red light had no effect on prodigiosin concentration in bacterial cells. Purified prodigiosin was degraded under white or blue light conditions but was not degraded under red and far-red light. Because white and blue light appeared to affect the stability of prodigiosin itself, light conditions may affect the suppressive effects of the biocontrol agent S. marcescens strain B2.     

RETRACTED ARTICLE: Effect of calcium chloride on the biocontrol efficacy of two antagonistic yeasts against <Emphasis Type="Italic">Penicillium expansum</Emphasis> on apple fruit

Two antagonistic yeasts, Candida membranaefaciens and Pichia guilliermondii, were evaluated for the control of the blue mold of apple caused by Penicillium expansum. Dual culture, cell-free metabolite and volatile tests were used for in vitro assay. Yeast strains of two genera inhibited growth of P. expansum; inhibition varied from 30.27% to 44.19% in dual culture, from 79.40% to 90.57% in the volatile metabolite test, and from 72.99% to 88.77% in the cell-free metabolite test. Calcium chloride (2% w/v) significantly inhibited the growth of the pathogen P. expansum, but did not affect the colony-forming units (CFU) of the yeasts C. membranaefaciens and P. guilliermondii in potato dextrose broth. The concentration of yeast suspension influenced spore germination and germ tube growth of P. expansum in vitro, as well as disease incidence and lesion development in fruits. There were significant negative relationships between the suspension concentrations of the yeasts and the growth as well as infectivity of the pathogen. The addition of calcium resulted in lower spore germination rates and slower growth of germ tubes in vitro, as well as in lower disease incidences and smaller lesion diameters compared with treatments with yeast antagonists alone. When yeast cell suspensions reached a concentration of 10⁷ CFU ml^-1, growth of the pathogen was completely limited in vitro, and no infection was found in apple fruits treated with or without calcium. This article has been retracted because part of the data shown has already been published before, by different authors. An erratum to this article can be found at     

蓝莓根腐病生防真菌的筛选鉴定及其生防机制分析

为筛选对蓝莓根腐病有良好防效的生防真菌资源,通过组织分离法和平板对峙法从蓝莓组织中分离筛选蓝莓根腐病病原菌——尖镰孢菌Fusarium oxysporum的拮抗真菌,对拮抗效果较好的菌株进行形态学和分子生物学鉴定,并采用平皿培养法和液相色谱-质谱联用法测定拮抗菌株代谢产物的抑菌活性及其成分,观察其重寄生现象,测定其胞外水解酶活性以及室内盆栽防效。结果显示,分离筛选到2株菌株G18和MG6对蓝莓根腐病病原菌有较好的拮抗作用,对病原菌菌丝生长的抑制率分别为60.24%和62.65%;结合形态学特征和核糖体转录间隔区（internal transcribedspacer,ITS）序列分析,最终将菌株 MG6 鉴定为球孢瓶束霉 Ascodesmis sphaerospora;菌株 G18 和MG6的发酵代谢物对蓝莓根腐病病原菌的抑制率分别为39.85%和42.86%,挥发性代谢物对其抑制率分别为21.39%和18.50%;从2株菌株发酵液中检测到了芥酸酰胺、邻苯二甲酸二丁酯和α-姜黄烯等13种已知具有抑菌活性的物质;同时发现2株菌株均可以分泌β-1,3-葡聚糖酶、纤维素酶和蛋白酶等水解酶;显微观察发现2株菌株均使病原菌菌丝出现明显的溶解、裂解等现象;菌株G18和MG6对蓝莓根腐病的防效明显,分别为65.33%和61.33%;接种菌株G18和MG6后蓝莓幼苗根中过氧化氢酶（catalase,CAT）活性最高,较清水对照组分别显著提高了1.01倍和1.02倍,接种菌株MG6后蓝莓过氧化物酶（peroxidase,POD）活性最高,在根和叶中的POD活性较清水对照组分别显著提高了 1.10 倍和 1.09 倍,先接种菌株 G18 后接种病原菌的蓝莓中超氧化物歧化酶（superoxidedismutase,SOD）活性最高,在根和叶中分别达559.61 U/g和422.68 U/g;接种菌株G18和MG6后蓝莓幼苗的叶绿素含量分别为1.036 mg/g和1.038 mg/g,均高于清水对照组。表明菌株MG6和G18是具有较好应用前景的蓝莓根腐病生防资源。     

Suppression of sporulation ofBotrytis spp. as a valid biocontrol strategy

In this study, the hypothesis was tested that removal of substrate for sporulation ofBotrytis spp. may lead to a retardation of an epidemic if the majority of the inoculum is produced inside the treated crop. Suppression of sporulation ofBotrytis spp. could be an attractive option for biological control ofBotrytis leaf spot in onions. In a field experiment, necrotic leaf tissue was removed to simulate the effect of a biocontrol agent. By this means, the amount of substrate on whichBotrytis spp. sporulates was reduced. In the experiment, the spore load above the onion plots was significantly reduced and the epidemic of onion leaf spot was retarded. At the end of the growing season, the number of leaf lesions in the green leaf area was lower in plots with substrate removal than in control plots (0.6 and 1.1 cm^–2, respectively). The results demonstrated that an epidemic of onion leaf spot largely depends on the rate of inoculum production inside a crop. Thus, suppression of sporulation on necrotic leaf tissue is a valid control strategy that could be applied by using sporulation suppressing antagonists.     

Selection and evaluation of phyllosphere yeasts as biocontrol agents against grey mould of tomato

Phyllosphere yeasts antagonistic to the infective activity of Botrytis cinerea were isolated from leaves of greenhouse-grown tomatoes and evaluated in a detached leaf assay for their ability to suppress grey mould. Nine of 30 recovered yeast isolates were found to reduce a disease index by >90% when compared to an untreated control. In greenhouse experiments, the yeast isolate Rhodotorula glutinis Y-44 was the most efficient in controlling grey mould of tomato plants. In further experiments in greenhouse-grown tomato plants the effectiveness of R. glutinis Y-44 was compared with two commercial fungicides. It was demonstrated that R. glutinis Y-44 was as effective as fungicides in controlling the pathogen. Moreover, the population of R. glutinis Y-44 was monitored for 8 weeks after application on tomato plants. The isolate successfully colonized the plant surface, although the population decreased by 10-fold 8 weeks after application. Since B. cinerea is also a major post-harvest pathogen for tomato fruits, the ability of R.␣glutinis Y-44, to protect artificially infected wounded tomato fruits was also tested. It was shown that R.␣glutinis Y-44 was able to reduce by 50% the percentage of infected wounds compared to the untreated controls.     

Biochemical changes in sunflower plants due to seed treatment/spray application with biocontrol agents

The application ofTrichoderma harzianum andPseudomonas fluorescens led to increases in dry matter content, starch, total soluble sugars (TSS) and reducing sugar contents in leaves of sunflower (Helianthus annuus) when done as seed treatment or coupled with spray. There was a significant increase in TSS and reducing sugars in stem tissue after treatment with biocontrol agents. The content of total phenols in leaves increased after treatment at 30 and 60 days after sowing (DAS) and at 30 DAS in stem tissues. Biocontrol agents increased the activities of phenylalanine ammonia lyase (PAL) in leaves and stem tissue after 30 DAS and significantly reduced total phenolic content and PAL activity in the stem at 60 DAS. Following treatment with biocontrol agents, seed lipid content increased, the proportion of linoleic acid increased and that of oleic acid decreased. Application of biocontrol agents to sunflower plants initiated certain biochemical changes, which can be considered to be part of the plant’s defense response. http://www.phytoparasitica.org posting August 6, 2008.     

产香真菌GS-1菌株鉴定及其挥发性物质对番茄灰霉病的生防效果

为鉴定产香真菌GS-1菌株物种分类和评价其挥发性物质对番茄灰霉病的生防效果,通过形态学和ITS(internal transcribed spacer)序列分析对菌株GS-1进行物种鉴定,以对扣法测定其挥发物对番茄灰霉病菌Botrytis cinerea、水稻胡麻斑病菌Bipolaris oryzae、小麦赤霉病菌Fusarium graminearum、白菜黑斑病菌Alternaria brassicae和莴苣菌核病菌Sclerotinia sclerotiorum共5种植物病原真菌的熏蒸抑制活性,以果实针刺法测定挥发物对番茄灰霉病的抑制作用,并观察对其菌丝生长的影响。结果显示,菌株GS-1为普通瘤座孢Tubercularia vulgaris;其挥发物对5种植物病原真菌均有明显的熏蒸抑制作用,72 h的抑制率为58.05%~75.81%;其挥发物可造成番茄灰霉病菌菌丝畸形、分枝增多、原生质外渗等,对番茄果实灰霉病的防效72 h后达53.62%。表明产香真菌普通瘤座孢GS-1菌株挥发物对番茄灰霉病有良好的生防效果。     

繁育寄主植物对浅黄恩蚜小蜂生防潜能的影响

为明确以雪莲果Smallanthus sonchifolius为寄主植物繁育的浅黄恩蚜小蜂Encarsia sophia的生防潜能,测定雪莲果繁育的浅黄恩蚜小蜂个体大小以及其对烟粉虱Bemisia tabaci MED隐种和温室白粉虱Trialeurodes vaporariorum的致死能力,并解析其寄生2种粉虱若虫后的子代发育情况。结果表明,雪莲果繁育的浅黄恩蚜小蜂雌雄蜂体长、头宽及后足胫节长度均显著高于番茄繁育的浅黄恩蚜小蜂。雪莲果繁育的浅黄恩蚜小蜂对烟粉虱和温室白粉虱的平均致死数量分别为24.7头和25.0头,显著高于番茄繁育的21.4头和21.0头。相对于番茄,雪莲果繁育的浅黄恩蚜小蜂寄生烟粉虱和温室白粉虱若虫后其子代发育时间更短,平均分别为13.2 d和12.5 d;而且子代羽化率也显著高于番茄繁育的子代羽化率,分别为84.1%和86.9%。表明与番茄相比,雪莲果为寄主植物繁育的浅黄恩蚜小蜂对烟粉虱和温室白粉虱具有更强的生防潜能。     

Natural occurrence of citrinin in rice grains and its biocontrol byTrichoderma hamatum

Paddy rice was sampled from El-Sharkia, El-Gharbia, El-Dakahlia and Kafr El-Shekh governorates, Egypt. Of the 30 samples taken, ten were contaminated with the mycotoxin citrinin. An average of 6.79 × 10⁴ fungal spores per gram rice was found. The isolated fungi represented 47 species and 28 genera. The predominant genera wereAspergillus, Cladosporium andPenicillium. Aspergilli were represented by 22 species;Aspergillus niger andA. flavus had the highest occurrence.Penicillium viridicatum produced the highest amount of citrinin on glucose ammonium nitrate salts broth and rice grains, and hence this isolate was selected as a good producer of citrinin in this study. The presence ofTrichoderma hamatum reduced the amount of citrinin produced byP. viridicatum compared with its respective control. The excessive growth ofT. hamatum onP. viridicatum was increased with time. Viability ofP. viridicatum conidia decreased byT. hamatum with an increase in the incubation period. Chitinases and 1,3-β-glucanase enzyme activity ofT. hamatum increased with extending the incubation period onP. viridicatum mycelia up to maximum values at 72 and 84 h, respectively.T. hamatum led to a decrease in the production of citrinin byP. viridicatum on rice grains compared with the respective control values. http://www.phytoparasitica.org posting Dec. 19, 2004.     

Fluorescent Pseudomonas isolate E11.3 as biocontrol agent for Pythium root rot in tulips

FluorescentPseudomonas isolates were obtained from Pythium-diseased tulip roots or rhizospheres. A selection of these isolates was tested for root rot-suppressing capabilities, using tulip cultivar Paul Richter (ice-tulip) as host andPythium ultimum P17 as pathogen. With isolate E11.3 root rot suppression was consistently found, but the extent of the effects varied from experiment to experiment. Beneficial effects were obtained after introduction of the bacteria either by mixing them through the soil or by dipping the bulbs in a bacterial suspension, immediately before planting. Application of bacteria in methylcellulose also reduced disease, but is of no practical value as methylcellulose by itself increased disease. In steamed soil, disease was more severe than in natural soil. In both circumstances, however, beneficial effects of bacterization with E11.3 were observed.Samenvatting Fluorescerende pseudomonaden werden geïsoleerd van tulpewortels of uit de rhizosfeer daarvan. Een aantal van deze isolaten is getoetst op wortelrot-onderdrukkend vermogen in een experimenteel systeem met tulpecultivar Paul Richter (vriestulp) als waardplant enPythium ultimum isolaat P17 als pathogeen. Wortelrotonderdrukking werd consequent waargenomen na bacterisatie metPseudomonas isolaat E11.3; de mate waarin rotonderdrukking optrad verschilde echter van experiment tot experiment. Bacterisatie vond plaats òf door de bacteriën door de grond te mengen òf door de bollen vlak voor het planten in een bacteriesuspensie te dompelen. Met beide methoden werden positieve resultaten bereikt. Toedienen van bacteriën in methylcellulose leidde ook tot reductie van de ziekte, maar heeft geen practische betekenis aangezien methylcellulose op zich de ziekte doet toenemen. Wortelrot was ernstiger in gestoomde dan in nietgestoomde grond, maar in beide omstandigheden werkte E11.3 wortelrotonderdrukkend.     

Nitric oxide-overproducing transformants of Pseudomonas fluorescens with enhanced biocontrol of tomato bacterial wilt

The relation between nitric oxide (NO) production and the protective ability of Pseudomonas fluorescens T5 against bacterial wilt disease in tomato was examined. The endogenous nitric oxide reductase gene of T5 was disrupted by homologous recombination using a suicide plasmid. Three disruptants were obtained, and all had higher levels of NO production. Infection with Ralstonia solanacearum was reduced in tomato plants treated with the NO-overproducing transformants compared with the wild type. These results suggest that the modification of pseudomonads to increase their level of NO production is a new approach to enhancing their biocontrol efficacy.     

两种蚜小蜂对烟粉虱MED隐种的田间笼罩控效评价

为明确烟粉虱Bemisia tabaci MED隐种优势寄生蜂海氏桨角蚜小蜂Eretmocerus hayati ZolnerowichRose与浅黄恩蚜小蜂Encarsia sophia GiraultDodd对其控制效果的影响,在棉田尼龙纱网笼罩中释放烟粉虱之后,再分别单独释放海氏桨角蚜小蜂、浅黄恩蚜小蜂以及二者以不同比例组合(1∶1、1∶3、3∶1)释放,定期调查统计2种蚜小蜂对烟粉虱的寄生量和烟粉虱的种群动态。结果表明,相对于不放蜂对照,自首次放蜂后40 d开始,所有放蜂处理均能显著降低烟粉虱若虫种群密度,每100 cm~2叶片上均少于1.00头,但各处理间的烟粉虱种群密度无显著差异;海氏桨角蚜小蜂和浅黄恩蚜小蜂以3∶1比例组合释放的处理中对烟粉虱的寄生量最高,每100 cm~2棉花叶片上能达到4.25头。表明在棉田中对烟粉虱进行生物防治时,以初级寄生蜂海氏桨角蚜小蜂与复寄生蜂浅黄恩蚜小蜂为3∶1的比例释放,可以到达较好的控制效果。     

辣椒炭疽病生防菌株的筛选、鉴定及其抑菌机理

为有效防控由胶孢炭疽菌Colletorichum gloeosporioides引起的辣椒炭疽病,自辣椒上分离得到内生细菌,通过平板拮抗和辣椒离体生防试验筛选对胶孢炭疽菌有抑制作用的拮抗菌株,通过形态学特征、生理生化特征以及分子生物学技术对其进行鉴定,并于室内测定其对胶孢炭疽菌菌丝生长的影响、对辣椒炭疽病的防效及接种后辣椒内抗病活性物质含量以及防御酶活性。结果显示,从辣椒上共分离纯化获得46株细菌,其中菌株SQ-6对胶孢炭疽菌有明显的抑制作用,抑制率为61.11%,显著高于其他45株。结合菌株SQ-6的形态学特征、生理生化特征以及分子生物学特征,将该菌株鉴定为解淀粉芽胞杆菌Bacillus amyloliquefaciens。SQ-6菌株的50%无细胞滤液可引起胶孢炭疽菌菌丝畸形、断裂等,对其抑制率为57.87%。SQ-6菌株的10%、50%发酵液和10%、50%无细胞滤液均能显著降低由胶孢炭疽菌引起的辣椒炭疽病的发病率和病情指数,其中50%无细胞滤液的防效最好。SQ-6菌株能够提高辣椒内Vc、酚类和黄酮类物质含量,诱导辣椒内过氧化物酶（peroxidase,POD）、丙氨酸解氨酶（p...     

红掌拮抗内生菌Y-54的分离、鉴定及其生防作用

为筛选具有广谱拮抗作用的内生菌,采用平板对峙法从健康红掌组织中分离和筛选对多种病原菌有拮抗作用的内生菌株,选择拮抗作用较好的菌株进行抑菌谱和拮抗作用测定,通过形态学特征、生理生化特性和分子生物学特征对其进行鉴定,利用盆栽试验测定其对红掌的促生作用和对红掌细菌性疫病的防效。结果显示,在健康红掌中共分离得到237株内生细菌,其中菌株Y-54的拮抗作用最强,其50倍发酵液对红掌细菌性疫病菌Xanthomonas axonopodis pv. dieffenbachiae的抑制作用最强,抑制率达37.78%;同时对多种病原真菌具有较强的抑制作用,其中对番茄叶霉病菌Cladosporium fulvum的抑制率达86.42%。结合形态学特征、生理生化特性和分子生物学特征将菌株Y-54鉴定为暹罗芽胞杆菌Bacillus siamensis。菌株Y-54的50倍发酵液可显著提高红掌叶长、叶宽和叶绿素相对含量(soil and plant analyzer development,SPAD)值,施药14 d和28 d后对红掌细菌性疫病的防效分别为62.94%和59.56%,与对照药剂的防效相当,表明菌...     

小麦茎基腐病生防菌株YB-161的分离鉴定及防效测定

为筛选防治小麦茎基腐病的高效生防菌株,采用稀释涂布法从小麦茎基腐病病土中分离细菌,以假禾谷镰孢Fusarium pseudograminearum为靶标菌,通过平板对峙培养法和室内盆栽试验筛选优良菌株并测定其田间防治效果,分析优良菌株发酵滤液对假禾谷镰孢的抑菌能力,并结合形态特征、Biolog微生物自动鉴定系统和gyrA序列分析对其进行种类鉴定,以及测定该菌株的抑菌谱。结果表明,10份供试土样中共分离到98株细菌,对假禾谷镰孢的菌丝生长抑制率超过40.00%的菌株有14株,其中菌株YB-161对假禾谷镰孢的菌丝生长抑制率最高,达63.50%。室内盆栽试验结果显示,菌株YB-161处理小麦的病情指数最低,为31.40,对小麦茎基腐病的防治效果最好,为68.15%,其对小麦也表现出较好的促生作用。田间调查结果显示,菌株YB-161菌液拌种处理对小麦茎基腐病的田间防治效果高于52.35%,并对小麦具有一定的增产作用。菌株YB-161的发酵滤液5倍稀释液和10倍稀释液对假禾谷镰孢的菌落抑制率分别达66.67%和44.33%,该菌株被鉴定为解淀粉芽胞杆菌Bacillus amyloliquefaciens。此外,菌株YB-161对辣椒炭疽病菌Colletotrichum capisci、烟草疫霉病菌Phytophthora parasitica等5种植物病原真菌均有较好的拮抗作用。表明生防菌株YB-161对绿色防控小麦茎基腐病具有良好的开发利用潜能。     

Tobacco cultivars vary in induction of systemic resistance against <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> and growth promotion by <Emphasis Type="Italic">Pseudomonas chlororaphis</Emphasis> O6 and its <Emphasis Type="Italic">gacS</Emphasis> mutant

The colonization of plant roots with certain rhizosphere bacteria promotes plant growth and induces long lasting systemic protection against a broad spectrum of plant pathogens. The role of the global regulator, GacS, in the rhizosphere colonist Pseudomonas chlororaphis O6 in stimulating growth promotion and induced resistance against Cucumber mosaic virus was examined in tobacco. Responses were compared in tobacco cvs Samsun and GX3. Root colonization of Samsun with wild-type O6 and the gacS complemented mutant-elicited reduced viral symptoms and viral titre. On GX3, there was little affect on symptoms when roots were colonized by the wild-type, gacS mutant or complemented mutant but colonization by both the wild-type and the gacS mutant lowered viral titre. Wild-type O6 and the gacS mutant caused plant growth to be maintained in both tobacco cultivars after viral infection, although the affect was stronger with GX3 than Samsun. In contrast, although a chemical inducer, benzothiadiazole, reduced symptoms and viral titre in both cultivars, plant growth was suppressed. Our results indicate rhizobacteria-elicited induced viral resistance without a negative impact on growth but there was a differential response between cultivars. Detailed knowledge regarding the mechanisms inherent to these differences between cultivars requires further investigation.     

枸杞炭疽病生防菌株筛选、生物功能测定及防治效果

为研发对枸杞炭疽病有良好防治效果的生防制剂,利用枸杞炭疽病菌Colletotrichum acutatum对实验室已分离保存的芽胞杆菌菌株进行室内筛选,并对拮抗效果较好的菌株进行形态学和分子生物学鉴定、病原菌孢子萌发抑制试验、生物学功能测定、稳定性测定、抑菌谱测定以及室内离体防治效果试验和田间防治效果试验。结果表明,菌株F3A对枸杞炭疽病菌有较好的拮抗作用,对枸杞炭疽病菌菌丝的抑制率为62.13%;结合形态学特征、16S rDNA以及gyrA基因序列分析,将菌株F3A鉴定为贝莱斯芽胞杆菌Bacillus velezensis;菌株F3A具有溶解有机磷和无机磷的能力,在含色氨酸和不含色氨酸的金氏培养液中产吲哚乙酸量分别为5.76 mg/L和5.74 mg/L;菌株F3A产蛋白酶和葡聚糖酶的活性较高;菌株F3A连续培养20代后,对枸杞炭疽病菌的抑制率为61.21%,该菌对棉花枯萎病菌Fusarium oxysporum f.sp.vesinfectum、番茄早疫病菌Alternaria solani、黄瓜枯萎病菌F.oxysporum f.sp.cucumerinum、番茄灰霉病菌Botrytis cinerea、番茄叶霉病菌Cladosporium fulvum、茄子菌核病菌Sclerotinia sclerotiorum和黄芪根腐病菌F.solani的抑制率分别为40.71%、53.58%、32.00%、53.00%、79.27%、71.13%和66.08%;菌株F3A发酵液的保护作用明显优于治疗作用,菌株F3A发酵液1倍稀释液室内预防效果为90.32%;喷施菌株F3A发酵液1倍稀释液3 d和7 d后的田间防治效果分别为78.26%和63.19%。表明菌株F3A有作为开发枸杞炭疽病生物农药的潜力。