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1.
Mating type genes of Verticillium dahliae, a wilt pathogen affecting many plant species, were identified to examine sexual recombination between Japanese pathotypes. We amplified a DNA sequence encoding high mobility group (HMG) box from V. dahliae using PCR. A cloned genomic DNA fragment included a sequence homologous to MAT1-2-1 gene. Despite that sequence's presence in all V. dahliae isolates we used, MAT1-1-1 (an opposite mating type gene) was never amplified. We concluded that V. dahliae is potentially heterothallic. Furthermore, sexual bias practically obviates sexual recombination between Japanese pathotypes. This report describes, for the first time, a mating type gene of phytopathogenic Verticillium.  相似文献   

2.
The effect of root-knot nematode (RKN) (Meloidogyne incognita) onVerticillium dahliae andFusarium oxysporum f.sp.vasinfectum in cotton (Gossypium hirsutum) was investigated. Two different inoculation methods were used, one in which inoculum was added to the soil, so that nematode and fungal inoculum were in close proximity; the other, inoculation into the stem, whereby the two inocula were spatially separated. Invasion of the roots by RKN enhanced disease severity, as measured by the height of vascular browning in the stem, following inoculation with either wilt pathogen. The effect of RKN on Fusarium wilt was more pronounced than that on Verticillium wilt. Nematode-enhanced infection byF. oxysporum is a well known effect but there are few reports of enhanced infection byVerticillium due to RKN. Relative resistance of a number of cotton cultivars to both wilt diseases, as measured by height of vascular browning, was similar to the known field performance of the cultivars. The use of vascular browning as an estimate of disease severity was therefore validated. http://www.phytoparasitica.org posting Feb. 3, 2003.  相似文献   

3.
为明确棉花内生真菌CEF-373菌株对棉花黄萎病的防效及其作用机理,利用圆盘滤膜法和平板对扣培养法测定菌株CEF-373对大丽轮枝菌Verticillium dahliae菌丝生长的抑制作用,测定其对棉花黄萎病的温室和田间防效,并通过活性氧含量及防御基因表达情况来分析其作用机理。结果表明,菌株CEF-373的挥发性代谢产物和非挥发性代谢产物对大丽轮枝菌菌丝的生长均有显著抑制作用,抑制率最高分别可达37.75%和100.00%。用1×107CFU/mL的菌株CEF-373分生孢子悬浮液灌根后,对棉花黄萎病的温室防效可达71.12%,用质量比为3%的菌株CEF-373固体菌剂拌土栽培后,对棉花黄萎病的温室防效可达62.74%,防治作用显著。菌株CEF-373的发酵液滴灌和微生物肥料处理40 d后,对棉花黄萎病的田间防效达到最大,分别为36.23%和27.71%,而在后期有所降低。菌株CEF-373可以诱导棉花叶片中细胞活性氧的爆发;且菌株CEF-373成功激活了苯丙氨酸解氨酶、过氧化物酶、多酚氧化酶、几丁质酶和病程相关蛋白基因PR10的表达,对大丽轮枝菌的侵染具有抵御作用。表明棉花内生真菌CEF-373菌株通过抑制大丽轮枝菌生长以及诱导寄主系统抗病性来有效防治棉花黄萎病,具有较好的生物防治应用前景。  相似文献   

4.
Biological soil disinfestation (BSD), or reductive soil disinfestation, achieved by amendment with organic materials such as wheat bran followed by flooding and covering the soil surface, has been used to control some soilborne diseases including Fusarium wilt and bacterial wilt of tomato. During a BSD treatment, accumulation of acetic acid and/or butyric acid was detected with high-performance liquid chromatography. Survival of Fusarium oxysporum f. sp. lycopersici or Ralstonia solanacearum was suppressed by these organic acids. Amendment of these organic acids into soil suppressed the survival of R. solanacearum at lower concentrations than the maximum detected in BSD treatment, indicating that production of these organic acids is one of the mechanisms of control. However, F. oxysporum f. sp. lycopersici in soil survived with the maximum concentrations of these organic acids achieved by BSD; thus, involvement of factors other than organic acids may be involved.  相似文献   

5.
During a survey conducted from 1998 to 2002, Fusarium proliferatum was found associated with young and adult palms belonging to the genera Chamaerops, Phoenix, Trachycarpus and Washingtonia showing symptoms of wilt and dieback. The fertility and toxicological profile of 36 strains representing different locations and hosts were studied. All of them except two, which were infertile, belonged to mating population D. Both mating types (MATD-1 and MATD-2) were isolated from the same host species, showing a high potential of genetic recombination in the field. Additionally, eight strains were fertile once crossed as female. Toxin analysis showed differences in the ability of strains to produce fumonisin B1, moniliformin, beauvericin, fusaric acid and fusaproliferin. Only 17 of them produced all the toxins analyzed. Pathogenicity tests were conducted on Phoenix dactylifera and P. canariensis using nine F. proliferatum Spanish strains and two reference strains from Saudi Arabia. Eight months after inoculation all strains caused disease, with palms showing lesions on the bases of leaves and development of wilt symptoms similar to those originally observed in affected plants. This is the first report on the occurrence of F. proliferatum on P. dactylifera in Spain and also the first report of this pathogen on C. humilis, P. canariensis, P. reclinata, T. fortunei, W. filifera and W. robusta.  相似文献   

6.
为研发用于防治香蕉枯萎病的维管组织导向杀菌剂,基于植物韧皮部“离子井”效应对非内吸杀菌剂咯菌腈进行弱酸化结构修饰,在蓖麻模型上完成韧皮部输导性筛选和机制验证,通过盆栽试验研究咯菌腈羧酸衍生物在香蕉植株上的输导分布,并测定衍生物对香蕉枯萎病的防效。结果表明：羧酸基团引入使咯菌腈衍生物在蓖麻幼苗上表现出韧皮部输导性,证明存在pH依赖的“离子井”效应机制;盆栽试验结果显示,衍生物1a在被叶片吸收后能向下传递到香蕉植株球茎和根部,并能够降解释放出咯菌腈,对香蕉枯萎病的防效为54.5%,显著高于咯菌腈原药处理组的防效6.5%。表明基于韧皮部“离子井”效应的结构修饰是香蕉维管组织导向杀菌剂研发的有效途径。  相似文献   

7.
Ascochyta blight caused by Ascochyta rabiei and fusarium wilt caused by Fusarium oxysporum. f. sp. ciceris are the two most serious diseases of chickpea (Cicer arietinum). Quantitative trait loci (QTL) or genes for ascochyta blight resistance and a cluster of resistance genes for several fusarium wilt races (foc1, foc3, foc4 and foc5) located on LG2 of the chickpea map have been reported independently. In order to validate these results and study the linkage relationship between the loci that confer resistance to blight and wilt, an intraspecific chickpea recombinant inbred lines (RIL) population that segregates for resistance to both diseases was studied. A new LG2 was established using sequence tagged microsatellite sites (STMS) markers selected from other chickpea maps. Resistance to race 5 of F. oxysporum (foc5) was inherited as a single gene and mapped to LG2, flanked by the STMS markers TA110 (6.5 cM apart) and TA59 (8.9 cM apart). A QTL for resistance to ascochyta blight (QTLAR3) was also detected on LG2 using evaluation data obtained separately in two cropping seasons. This genomic region, where QTLAR3 is located, was highly saturated with STMS markers. STMS TA194 appeared tightly linked to QTLAR3 and was flanked by the STMS markers TR58 and TS82 (6.5 cM apart). The genetic distance between foc5 and QTLAR3 peak was around 24 cM including six markers within this interval. The markers linked to both loci could facilitate the pyramiding of resistance genes for both diseases through MAS.  相似文献   

8.
The lipids metabolism of tomato and bean plants during biological control of wilt pathogens (Fusarium oxysporum f.sp.lycopersici andF. oxysporum f.sp.phaseoli, respectively) byBacillus subtilis was investigated. The interaction of wilt pathogens with both tomato and bean caused an imbalance and drastic reduction in total lipids, triacylglycerol, sterol and all phospholipd fractions except phosphatidic acid. The application of a formulated biocontrol agent,B. subtilis, eliminated the detrimental effect of both wilt pathogens and consequently prevented catabolism of lipid fractions in both tomato and bean. Moreover, the changes in the lipid fractions as a sensitive monitor for biocontrol of wilt diseases suggest a positive correlation between the application ofB. subtilis and improvement in the host metabolism towards anabolism. http://www.phytoparasitica.org posting Sept. 20, 2006.  相似文献   

9.
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  相似文献   

10.
Extracellular polysaccharides (EPSs) likely provide phytopathogenic bacteria a selective advantage both inside and outside plants. Despite the relatively scant knowledge about EPS biosynthesis in phytopathogenic bacteria, it clearly is a well controlled, complex, energy-intensive process. Unexpectedly, three phytopathogenic bacteria have been found to autoregulate EPS production in response to extracellular signal compounds (pheromones) that they produce. Like many bacteria, Pantoea stewartii subsp. stewartii produces a N-acyl-homoserine lactone (AHL) autoinducer. However, unlike most AHL-dependent autoinduction systems, that in P. stewartii subsp. stewartii somehow represses EPS production in the absence of autoinducer. Instead of an AHL-dependent system (which it also has), Ralstonia solanacearum uses a novel autoregulator identified as 3-hydroxypalmitic acid methyl ester to regulate EPS biosynthesis. A lack of this autoregulator in R. solanacearum results in repression of EPS biosynthesis by a complex two-component sensor/response regulator signal cascade. Xanthomonas campestris pv. campestris has two partially overlapping autoregulatory systems. The autoregulators are incompletely characterized, but one diffusible signal factor (DSF) is thought to be a fatty acid derivative and the other diffusible factor (DF) may be a butyrolactone. The autoregulation pathways in X. campestris pv. campestris are essentially unknown, but EPS production is controlled by both the DSF and DF systems, whereas production of extracellular enzymes and pigment production are regulated independently. In a confined micro-environment, population density and intercellular concentrations of an autoregulator will increase in parallel, so autoregulation is one way that bacteria can coordinate gene expression to synthesize EPS only at high cell density. However, because there is often limited evidence that it is actually cell density that is being detected, researchers should not assume a priori that autoregulation must function for quorum sensing. Some possible reasons for why phytopathogenic bacteria would benefit from delaying EPS production are discussed.  相似文献   

11.
Six inoculation techniques were compared for their ability to evaluate resistance toColletotrichum acutatum of five strawberry cultivars. Inoculation by dipping the whole cold stored plants in a suspension of conidia adjusted to 2.106 conidia ml–1 made it possible to screen cultivars resistant to crown rot at 28 days after inoculation. Using the dipping technique, 44 strawberry cultivars were evaluated for their resistance to one strain ofC. acutatum, 1267b. Twelve of them did not show wilt symptoms and could be classified as resistant. When another strain ofC. acutatum, 494a, was inoculated to seven cultivars, all of them including Dover, resistant to 1267b, showed wilt symptoms. This result showed the importance of investigations on genotype × isolate interactions to conduct an efficient breeding programme for screening resistance toC. acutatum.  相似文献   

12.
为明确帚枝霉属内生真菌Sarocladium brachiariae HND5菌株具体的抑菌活性物质,在全基因组测序数据的基础上,利用生物信息学对抑菌活性物质合成基因簇进行定位,通过聚类分析和系统发育树分析对基因簇合成产物进行鉴定,并通过基因缺失突变构建及代谢组分析确定具体的抑菌活性物质。结果显示,HND5菌株共含有7个非核糖体多肽合成酶(non-ribosomal peptide synthetase,NRPS)基因簇,聚类分析结果表明基因簇29合成产物为噬铁素,基因簇30合成产物为类环孢霉素类抗菌多肽;系统发育树结合生物信息学结果显示基因簇30合成产物与已知环孢霉素结构差异大,为一个新型非核糖体多肽;将基因簇30 NRPS基因缺失突变后,HND5菌株丧失抑菌活性;同野生型菌株相比,基因簇30 NRPS基因缺失突变体缺失一个分子量为887.54 Da的多肽类物质。表明HND5菌株的抑菌活性物质为一个分子量为887.54 Da的新型类环孢霉素非核糖体多肽,基因簇30负责该多肽的生物合成。  相似文献   

13.
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14.
Fusarium wilt is now a major disease of carnation crops worldwide. Methyl bromide, which is used to remedy it, is environmentally unsafe. An alternative approach integrated into biological control is to grow crops in suppressive media. Suppressiveness of seven plant growth media to Fusarium oxysporum f. sp. dianthi was evaluated in bioassays with carnation (Dianthus cariophyllus) cv. Medea. These media were: (1) grape marc compost, (2) cork compost, (3) olive oil husk + cotton gin trash composted and mixed with rice husk, (4) spent mushroom compost mixed with peat, (5) coir fibre, (6) light peat and (7) vermiculite. In order to look for carnation Fusarium wilt suppressiveness indicators, growth medium pH and β-glucosidase activity were evaluated. Furthermore, F. oxysporum populations were measured in plant growth media at the beginning and end of bioassays. The compost media showed a range of suppressiveness in comparison with peat. Grape marc compost was the most effective plant growth medium in suppressing carnation Fusarium wilt. On the other hand coir fibre, peat and vermiculite were conducive for this disease. β-glucosidase activity and pH were positively correlated with disease severity as in other reports for tomato. Therefore, these two parameters are good indicators for carnation Fusarium wilt suppressiveness, and possibly for other F. oxysporum pathosystems. All composts showed similar F. oxysporum populations at the end of the bioassays to peat and vermiculite.  相似文献   

15.
Since the beginning of the 20th century, pine trees in Japan have been seriously damaged by the pine wilt disease. This disease is caused by the pine wood nematode, Bursaphelenchus xylophilus, which is transmitted by the Japanese pine sawyer, Monochamus alternatus. The control of disease depends to a large extent on chemicals, but the public is now demanding environmentally friendly control methods. The virulence of B. xylophilus varies very widely. Pre-inoculation of young pine trees in a nursery with avirulent B. xylophilus has induced systemic resistance of trees against a subsequent inoculation with virulent B. xylophilus. This induced resistance was considered a hopeful means for developing a biological control for the disease. The induced resistance by the avirulent nematodes was also expressed in mature pine trees in a forest where the disease was naturally epidemic. However, the effects of induced resistance were not satisfactory for practical biological control. Since the inoculation with higher concentrations of the avirulent B. xylophilus induced the resistance more effectively, the pre-inoculation method will need to be improved to develop the biological control. The induced resistance of pine trees by avirulent B. xylophilus should be one of the candidate biological control methods against pine wilt disease. This induced resistance also provides an experimental system to clarify physiological interactions between the nematodes and pine trees.  相似文献   

16.
Pseudomonas fluorescens strain PfG32R actively suppresses the occurrence of bacterial wilt disease of tomato caused by Ralstonia solanacearum. To determine the characteristics affected by spontaneous mutations in the gacS gene, three spontaneous mutants NR1, NR9, and ASW6 were tested for production of several enzymes, antimicrobial activity, and biocontrol activity against bacterial wilt disease of tomato in a greenhouse. Production of biosurfactant and of enzymes such as Tween-80 lipase, gelatin protease, and lecithinase; swarming activity; and antifungal activities against Fusarium oxysporum f. sp. radicis-lycopersici and F. graminearum were inactivated by mutations in the gacS gene, indicating that they are under the regulation of the GacS/GacA two-component regulatory system. Levan production, swimming, antifungal activity against Magnaporthe grisea, and antibacterial activity against R. solanacearum and Erwinia carotovora ssp. carotovora were not controlled by the GacS/GacA system. Biocontrol activities of the three spontaneous mutants varied from strain to strain, indicating that the biocontrol activities of PfG32R are influenced not only by the GacS/GacA system but also by other complex factors, which may not be regulated by the system.  相似文献   

17.
Arabidopsis thaliana ecotype Columbia-0 was transformed with a green fluorescent protein (GFP) gene under control of a phenylalanine ammonia-lyase (PAL) promoter. PAL is a key enzyme of the phenylpropanoid pathway and is induced to high levels during plant stress. Constitutive expression of PAL1 promoter-controlled GFP occurred in vascular tissues within stems, leaves and roots and in developing flowers. PAL1 promoter–GFP expression was examined in leaves of transgenic plants subjected to an abiotic elicitor, mechanical wounding or to inoculation with the pathogens Pseudomonas syringae pv. tomato or Peronospora parasitica. Wounding of leaves and treatment with an abiotic elicitor and compatible interactions produced low to moderate levels of GFP. However, in incompatible interactions there were high levels of GFP produced. In incompatible interactions, the intensity of GFP fluorescence was similar to that produced in transgenic plants expressing GFP driven by the CaMV promoter. The bright green fluorescence produced in live cells and tissues was readily visualised using conventional fluorescence microscopy and was quantified using spectroflourometry. This is the first report of the use of GFP as a reporter of defence gene activation against pathogens. It has several advantages over other reporter genes including real time analysis of gene expression and visualisation of defence gene activation in a non-invasive manner.  相似文献   

18.
The Arabidopsis MPK3 gene product participates in disease resistance mediated by the MAP kinase cascade. The expression of the MPK3 gene is induced by pathogen inoculation and treatment with chemicals such as salicylic acid (SA) and methyl jasmonate (JA), but the detailed expression pattern of the MPK3 gene has been largely unknown. To investigate MPK3 gene expression in response to disease stress, we fused the MPK3 promoter to the firefly luciferase gene to create a real-time monitoring system for regulated gene expression in planta. The results of an in vivo reporter assay using transgenic Arabidopsis plants harboring MPK3::Fluc showed that the MPK3 promoter activity was induced by treatment with chemicals such as SA and benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), that induce defense gene expression. Inoculation with the fungal pathogen Botrytis cinerea resulted in systemic induction of MPK3::Fluc.  相似文献   

19.
番茄枯萎病菌和青枯病菌拮抗细菌的评价   总被引：3，自引：1，他引：2  
为筛选出对番茄枯萎病和青枯病有较好防效的生防菌,采用平板对峙法,以番茄枯萎病菌Fusarium oxysporum和番茄青枯病菌Ralstonia solanacearum为靶标菌,从江苏沭阳、宿迁、溧水及内蒙古海拉尔分离到的2 062株细菌菌株中筛选拮抗菌株,并采用平板对峙法、拮抗菌液灌根法、分子生物学方法进行拮抗物质检测、盆栽试验及种属鉴定。结果表明:从2 062株细菌中共筛选到21株对番茄枯萎病和青枯病具有很强拮抗作用的菌株,均能分泌蛋白酶,具有解磷作用;不能分泌几丁质酶和纤维素酶,仅4株细菌能分泌嗜铁素。拮抗细菌SY290对番茄枯萎病和番茄青枯病防效最高,分别达到74.2%和75.0%,SQ728和LS536次之,但防效均大于60%。结合各菌株形态特征、16S r DNA与gyr-B序列分析结果,菌株SY177、SY290和SQ728鉴定为解淀粉芽胞杆菌Bacillus amyloliquefaciens,菌株LS536为枯草芽胞杆菌B.subtilis。  相似文献   

20.
Five experimental trials were carried out to test different biological control agents against Fusarium wilt of lettuce, cause byFusarium oxysporum f.sp.lactucae. In the presence of a very high disease incidence, the best results in terms of disease control as well as increased growth response were shown byTrichoderma harzianum T 22 (RootShield), which, at 3 gl −1 of substrate, provided very consistent results.F. oxysporum IF 23 gave good disease control but in two out of five trials reduced the biomass produced. Less consistent, but still significant results were provided byF oxysporium MSA 25, at 3 gl −1 of substrate, and byTrichoderma viride TV 1. The twoF. oxysporum agents Fo 251/2 and Fo 47 and the mixture ofT. harzianum + T. viride (Remedier) partially reduced disease incidence but were less effective than the above mentioned. Less interesting results were offered byStreptomyces griseoviridis (Mycostop). The results obtained show that biological control can play a role in the management of Fusarium wilt of lettuce.  相似文献   

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