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1.
Twenty-seven seed samples belonging to the lettuce cultivars most frequently grown in Lombardy (northwestern Italy), in an area severely affected by Fusarium wilt of lettuce, were assayed for the presence ofFusarium oxysporum on a Fusarium-selective medium. Isolations were carried out on subsamples of seeds (500 to 1500) belonging to the same seed lots used for sowing, and either unwashed or disinfected in 1% sodium hypochloride. The pathogenicity of the isolates ofF. oxysporum obtained was tested in four trials carried out on lettuce cultivars of the butterhead type, very susceptible to Fusarium wilt. Nine of the 27 samples of seeds obtained from commercial seed lots used for sowing in fields affected by Fusarium wilt were contaminated byF. oxysporum. Among the 16 isolates ofF. oxysporum obtained, only one was isolated from disinfected seeds. Three of the isolates were pathogenic on the tested cultivars of lettuce, exhibiting a level of pathogenicity similar to that of the isolates ofF. oxysporum f.sp.lactucae obtained from infected wilted plants in Italy, USA and Taiwan, used as comparison. The results obtained indicate that lettuce seeds are a potential source of inoculum for Fusarium wilt of lettuce. The possibility of isolatingF. oxysporum f.sp.lactucae, although from a low percent of seeds, supports the hypothesis that the rapid spread of Fusarium wilt of lettuce observed recently in Italy is due to the use of infected propagation material. Measures for prevention and control of the disease are discussed. http://www.phytoparasitica.org posting Dec. 16, 2003.  相似文献   

2.
Seven experimental trials were carried out to evaluate the efficacy of the bacterial strains Achromobacter xylosoxydans AM1 and Serratia sp. DM1 obtained from suppressive soils and from soilless used rockwool substrates (Pseudomonas putida FC6B, Pseudomonas sp. FC7B, Pseudomonas putida FC8B, Pseudomonas sp. FC9B and Pseudomonas sp. FC24B) against Fusarium wilt on rocket caused by Fusarium oxysporum ff. spp. raphani and conglutinans. Along with these strains, two commercial bioproducts (RootShield—Trichoderma harzianum T22; Cedomon—Pseudomonas chlororaphis MA342) were also tested. Different application strategies such as soil treatment (trials I to VI; 107 and 108 CFU ml−1) and root dipping (trial VII; 108 and 109 CFU ml−1) were performed in a glasshouse in order to test the efficacy of the bacterial strains against Fusarium oxysporum ff. spp. raphani and conglutinans. The lowest disease incidence (16.7%) was observed with the application of Achromobacter sp. AM1, Serratia sp. DM1 at 108 CFU ml−1 and Pseudomonas sp. FC9B at 107 CFU ml−1 against F. oxysporum f. sp. conglutinans (experiment I). Maximum plant biomass (5.0 g/plant) was registered in Serratia sp. DM1 at 108 CFU ml−1 treated plants in trial IV. The trials against F. oxysporum f. sp. raphani (experiment II) showed that the application of Pseudomonas sp. FC7B, P. putida FC8B at 108 CFU ml−1 and P. chlororaphis MA342 at 7.5 × 106 CFU ml−1 significantly reduced disease incidence to values ranging between 87% and 92%. The highest plant biomass was recorded with the application of Achromobacter sp. AM1 and P. putida FC6B at 107 CFU ml−1 (3.9 to 4.2 g) carried out 7 days before the artificial inoculation of the pathogens (trial IV). The present study showed the potential biocontrol activity of the bacterial strains Achromobacter sp. AM1, Serratia sp. DM1 and Pseudomonas sp. FC9B against F. oxysporum f. sp. conglutinans and of Pseudomonas sp. FC7B, P. putida FC8B, P. chlororaphis MA342, Achromobacter sp. AM1 and P. putida FC6B against F. oxysporum f. sp. raphani. Growth-promoting activity of biocontrol bacteria used during the trials was observed.  相似文献   

3.
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   

4.
This study concerned a new disease detected in 1997 in southeastern Spain — Fusarium wilt in basil (Ocimum basilicum L.), caused byFusarium oxysporum f.sp.basilici. Its importance was evaluated at two locations in the Almería area, where 14% of the plants presented symptoms of the disease after 4 months of cropping. The search for sources of the disease inoculum was centered on the health of the seeds and the polypropylene trays that were reused for plant production. Analysis of four lots of seeds from Germany and Italy showed that two of them harboredF. oxysporum f.sp.basilici. This finding was confirmed by the analysis of seeds collected from diseased plants. Furthermore, analysis of three reused trays revealed the presence of the pathogen on them and it was concluded that the trays acted as the source of dispersion of the mycosis. http://www.phytoparasitica.org posting July 14, 2004.  相似文献   

5.
The Elegans fusaria causing wilt disease of carnation. I. Taxonomy   总被引：1，自引：0，他引：1  
The distinction of the wilt disease pathogen of carnationFusarium (oxysporum var.)redolens fromF. oxysporum (var.oxysporum) is considered. Previous reports that isolates of both taxa cause indistinguishable diseases in carnation are confirmed.F. (oxysporum var.)redolens andF. oxysporum were found to form one variable complex on morphological criteria. Apparently, host specialization rather than morphological variation reflects the evolutionary relationships in theFusarium sectionElegans. The distinction ofF. redolens fromF. oxysporum does therefore not seem justified, neither at specific nor at varietal level.Samenvatting Het onderscheid tussenFusarium (oxysporum var.)redolens enF. (oxysporum var.)oxysporum als verwekkers van verwelkingsziekte bij anjer wordt ter discussie gesteld. Fytopathologisch onderzoek bevestigde vermeldingen in de literatuur dat voor anjer pathogene isolaten van beide soorten ziekten veroorzaken die niet te onderscheiden zijn; dit is ook bekend voor andere gewassen. Op morfologische gronden blekenF. (oxysporum var.)redolens enF. oxysporum één variabel complex te vormen. Kennelijk geeft de pathogene specialisatie inFusarium sectieElegans de evolutionaire verwantschappen beter weer dan de morfologische variatie. Het onderscheiden vanF. redolens naastF. oxysporum is daarom noch als soort, noch als variëteit gerechtvaardigd.  相似文献   

6.
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   

7.
大豆枯萎病菌尖孢镰孢遗传多样性及大豆品种抗性   总被引：2，自引：0，他引：2  
 了解大豆枯萎病菌的群体遗传特征及明确大豆种质对大豆枯萎病的抗性,对抗病育种、抗性品种的合理布局以及制定更有效的病害防治策略具有重要的参考价值。本研究利用随机扩增多态性DNA(random amplified polymorphic DNA,RAPD),对采自我国不同地区的大豆枯萎病菌—尖孢镰孢菌(Fusarium oxysporum)进行遗传多样性分析,筛选到10个多态性随机引物,共扩增出75条RAPD条带,其中55条为多态性条带,占73.3%。利用UPGMA法对DNA扩增图谱进行聚类分析,以相似系数0.68为阈值,55个分离物可分为9个遗传聚类组,表明我国大豆枯萎病菌具有丰富的种内遗传多样性,所划分的群体与分离物来源地不相关。同时,对上述分离物进行致病性分析,发现我国的大豆枯萎病菌具有明显的致病力分化现象。进一步利用3个代表性分离物对来自我国不同大豆产区的180个大豆品种(资源)进行抗大豆枯萎病鉴定,发现皖豆28、中黄13、中黄51、中作X08076和5D034等5个品种对大豆枯萎病具有良好抗性,占供试材料的2.8%,表明不同大豆品种对枯萎病的抗性存在一定的差异。  相似文献   

8.
Fusarium wilt of basil (Ocimum basilicum), caused byFusarium oxysporum f.sp.basilici, is reported for the first time in Greece. Foliage inoculation of young plants resulted in a downward movement of the pathogen to the crown and roots and 20–30% plant mortality. Of 14 commercial basil cultivars evaluated for possible disease resistance using young plants, six out of eight large-leaved cultivars were found resistant, while all six small-leaved ones were susceptible. http://www.phytoparasitica.org posting Feb. 23, 2004.  相似文献   

9.
The behaviour of Fusarium oxysporum f.sp. lycopersici (Fol) and the effectiveness of the microbial control agent Trichoderma asperellum strain T34 were examined in hydroponically grown tomato plants under five ammonium/nitrate ratios. The results showed that disease severity was reduced by the action of T34 under increasing concentrations of ammonia. Furthermore, rhizosphere F. oxysporum populations decreased with T34 application. The presence of T34 augmented leaf nitrogen concentration in treatments infested with Fol. In addition, T34 application reduced iron concentration in tomato leaves at high ammonium/nitrate ratios and reduced the severity of Fusarium wilt at high iron and nitrogen leaf concentrations.  相似文献   

10.
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   

11.
四季豆枯萎病病原鉴定及防治   总被引：2，自引：0，他引：2  
从南宁市郊11个病区采集的四季豆枯萎病株标样,经分离培养鉴定和致病性测定,证明其病原菌为尖孢镰刀菌菜豆专化型(Fusarium oxysporum f. sp. phaseoli Kend & Syd)。此病在南宁于4月上中旬四季豆初花期开始发生,5月中下旬盛花至结荚期为发病高峰期。用滤纸碟法进行药效试验的结果,40%灭病威300-500倍液的抑菌圈最大,田间灌根防治也有一定效果。可用种子重量的0.5%多菌灵可湿性粉拌种。品种间抗病性有显著差异,秋抗19号和秋抗6号较抗病。  相似文献   

12.
Fusarium wilt, caused by Fusarium oxysporum f. sp. cucumerinum (FO), is one of the major diseases in cucumber (Cucumis sativus) production. Root and foliar applications of 24-epibrassinolide (EBL), an immobile phytohormone with antistress activity, were evaluated for their effects on the incidence of Fusarium wilt and changes in the microbial population and community in roots of cucumber plants. EBL pre-treatment to either roots or shoots significantly reduced disease severity followed by an improved plant growth regardless of the treatment methods applied. EBL applications decreased the Fusarium population on root surfaces and in nutrient solution, but increased the population of fungi and actinobacteria on root surfaces. PCR-DGGE analysis showed that FO-inoculation had significant effects on the bacterial community on root surfaces as expressed by a decreased diversity index and evenness index, but EBL applications alleviated these changes. Moreover, several kinds of decomposing bacteria and growth-promoting bacteria were identified from root surfaces of FO-inoculated plants and EBL-pre-treated plants, respectively. Overall, these results show that the microbial community on root surfaces was affected by a complex interaction between phytohormone-induced resistance and plant pathogens.  相似文献   

13.
We selected a reduced-pathogenicity mutant of Fusarium oxysporum f. sp. lycopersici, a tomato wilt pathogen, from the transformants generated by restriction enzyme-mediated integration (REMI) transformation. The gene tagged with the plasmid in the mutant was predicted to encode a protein of 321 amino acids and was designated FPD1. Homology search showed its partial similarity to a chloride conductance regulatory protein of Xenopus, suggesting that FPD1 is a transmembrane protein. Although the function of FPD1 has not been identified, it does participate in the pathogenicity of F. oxysporum f. sp. lycopersici because FPD1-deficient mutants reproduced the reduced pathogenicity on tomato.The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession number AB110097  相似文献   

14.
The employment of formulateBacillus subtilis as a biocontrol agent successfully controlledFusarium oxysporum f.sp.lycopersici within tomato seedlings (in vivo). B. subtilis was able to proted cortex and vascular tissues of tomato against progression of the wilt pathogen. No changes were observed in tomato tissues due to application ofB. subtilis except for hypertrophy and elongation of cortex tissues, which indicates the production of plant growth hormones byB. subtilis.  相似文献   

15.
为研究枯萎病对马铃薯光合特性的影响,在幼苗期接种尖孢镰刀菌Fusarium oxysporum后,统计抗病品种陇薯10号和感病品种新大坪的病情指数,并测定叶绿素含量、光合及荧光参数。结果表明,尖孢镰刀菌侵染30 d后马铃薯表现出枯萎病症状,叶绿素含量显著降低,其中叶绿素a含量降幅最大,抗病品种陇薯10号比对照降低9.64%,感病品种新大坪比对照降低14.24%。尖孢镰刀菌侵染后马铃薯光合效率显著降低,侵染30 d后,抗病品种陇薯10号净光合速率比对照降低39.56%,感病品种新大坪比对照降低47.13%。病株的光响应曲线参数光补偿点、暗呼吸速率和表观量子效率都显著提高;而光饱和点和最大净光合速率都显著低于对照,表明尖孢镰刀菌侵染缩小了马铃薯对光能的利用有效范围。病株CO2响应曲线参数CO2饱和点、最大净光合速率和羧化效率分别显著低于对照;病株CO2补偿点和光呼吸速率反而升高,说明碳同化过程受到尖孢镰刀菌的限制。暗适应下的初始荧光、最小荧光、最大荧光、PSII最大光化学效率、光适应下PSII最大光化学效率及实际光化学效率、光化学猝灭系数、非光化学猝灭系数和光合电子传递速率均显著低于对照,...  相似文献   

16.
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   

17.
A study was conducted in two greenhouses with a history of Fusarium crown and root rot (Fusarium oxysporum f.sp.radicis-lycopersici, Forl) and root-knot nematodes (Meloidogyne javanica andM. incognita). During the 2005–06 growing season, the effectiveness of soil disinfestation by solarization in combination with low doses of metham-sodium (500, 750, 1000 and 1250l ha−1) or dazomet (400 g ha−1), was tested against soilborne pathogens and nematodes in an attempt to find a suitable alternative to methyl bromide, which is soon to be phased out. Solarization alone was not effective in the greenhouse with a high incidence ofForl. In the greenhouse with a low level ofForl, all the treatments tested reduced disease incidence, and were therefore considered to be applicable for soil disinfestation. In addition, root-knot nematode density decreased with all the treatments tested in both of the greenhouses.  相似文献   

18.
芝麻枯萎病病原菌致病力室内鉴定方法   总被引：3，自引：0，他引：3  
 芝麻枯萎病(Sesame Fusarium wilt, SFW)是由尖孢镰刀菌芝麻专化型(Fusarium oxysporum Schl. f. sp. sesami (Zap.), FOS)引起的一种土传真菌病害, 是世界芝麻生产上的主要病害之一。为测定FOS致病力, 本文选用郑芝98N09等4个芝麻品种, 在苗期对15个FOS菌株的致病力强弱进行了室内鉴定和评价。结果表明, 采用1×106个/mL分生孢子悬浮液与无菌蛭石和无菌土壤按V1∶V2∶V6比例混合接菌(即最终接菌浓度为1.4×105孢子/g土壤), 在接菌后第7 d幼苗开始出现枯萎病症状, 调查菌株致病性的最佳时间为接菌后第25 d~28 d;在供试15个FOS菌株中, 对4个品种均表现为强致病力的菌株有8个(DI>50), 均表现为弱致病力的菌株有5个(DI<20);不同芝麻品种对不同菌株的抗性有一定差异。该方法可应用于芝麻枯萎病病原菌致病性测定和芝麻种质抗枯萎病特性评价, 并为后续的机理研究提供了技术支持。  相似文献   

19.
Nonpathogenic isolates of Fusarium oxysporum can be successful antagonists of pathogenic forms of the same fungal species that commonly attacks crop plants. The characteristics that distinguish nonpathogenic from pathogenic forms are not well understood. In this study, the mode of root colonization of Eucalyptus viminalis seedlings by a nonpathogenic F. oxysporum strain is described at the ultrastructural level. Root systems of E. viminalis plants were inoculated with nonpathogenic F. oxysporum strain Fo47 in an in vitro model system. Changes in the occurrence of nonesterified and methyl-esterified pectins in colonized E. viminalis roots were evaluated by in situ immunolabeling using two monoclonal antibodies, JIM 5 and JIM 7. Modes of penetration and root colonization patterns in E. viminalis seedlings by the nonpathogenic fungus were similar to those described for pathogenic forms of F. oxysporum. However, root interactions differed in that the nonpathogenic fungus did not induce host tissue damage. No papilla-like appositions were observed in host cells in response to invading hyphae, which did not disrupt the host plasma membrane in many cases, suggesting that a biotrophic relationship was established. Root colonization by the nonpathogenic strain did not induce alteration in JIM 7 labeling of methyl-esterified pectin in E. viminalis cell walls, whereas nonesterified pectin was detected to a significantly greater extent in cell walls of roots colonized by the fungus. Pectin components decreased slightly only at points of hyphal contact with host cells. Because nonpathogenic strains utilize pectin in pure culture, host control over enzyme activity or production by the fungi may at least partly explain their compatible interactions with host tissues.  相似文献   

20.
The potential of grafted watermelon for resistance toFusarium oxysporum f.sp.niveum on some Curcurbitaceae,Lagenaria, Luffa, Benincasa and commercial rootstocks was evaluated. Effects of grafting on yield and quality of diseased plants were evaluated. All grafted plants and rootstocks were resistant to the three known races (0, 1, and 2) ofF. oxysporum f.sp.niveum except watermelon cv. ‘Crimson Tide’, which was susceptible to race 2. Fruit yield was positively (21–112%) affected byLagenaria rootstocks but negatively affected (200–267%) byCucurbita rootstocks when compared with the control. While only minor differences in fruit quality were determined in control and grafted plants onLagenaria rootstocks, the quality parameters for watermelon grafted ontoCucurbita rootstocks were lower than in the control. The reasons for low yield and quality might be due to an incompatibility betweenCucurbita rootstocks and watermelon. These results showed that rootstock influence on disease resistance as well as yield and quality of scion fruit is important in determining the potential use of grafting applications in watermelon. http://www.phytoparasitica.org posting Feb. 2, 2003.  相似文献   

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