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1.
Fusarium wilt, caused by Fusarium oxysporum f. sp. melonis (Fom), is one of the most widespread and devastating melon diseases. This vascular disease is caused by the colonization of melon xylem vessels by any of the four Fom races reported (r0, r1, r2 and r1,2, subdivided into r1,2w and r1,2y). The macroscopic evaluation of disease symptoms (disease rating, DR) at several days post‐inoculation (dpi) with Fom spores has been the traditional method to determine the resistance of melon accessions to this fungal pathogen. In this study, one isolate from each Fom race was transformed by Agrobacterium tumefaciens to constitutively express the green fluorescent protein (GFP). Fom‐GFP transformants, as virulent as the corresponding wildtype races, were selected to develop an inoculation assay based on the non‐invasive evaluation of the fluorescence emitted by Fom‐GFP. It was determined that melon root neck was the appropriate area to follow Fom‐GFP and a fluorescence signal rating (FSR) was established in parallel to DR determination. This method allowed the evaluation of GFP signal in the root neck of inoculated melon seedlings at 11–15 dpi. The GFP signal was scored in 62 melon accessions/breeding lines inoculated with different Fom‐GFP, followed by evaluation of the macroscopic DR in the aerial part of melon seedlings at 20–28 dpi. Correlation analysis demonstrated a direct and significant relationship between FSR and DR. This method has shown to be an effective and reliable tool that can assist Fom resistance breeding programmes in melon.  相似文献   

2.
In 1994, Fusarium wilt of melon cultivars which are resistant to races 0 and 2 of Fusarium oxysporum f. sp. melonis was observed in southern area of the Lake Biwa region, Shiga prefecture. In commercial fields, mature plants of cv. Amus which were grafted onto cv. Enken Daigi 2, and of cv. FR Amus showed yellowing, wilting and finally death before harvesting of fruits. Diseased plants had vascular and root discolorations, and their stem sections yielded typical colonies of F. oxysporum. When the Shiga strains were tested for their pathogenicity to 12 species of cucurbits, they caused wilts only on melon. Using race differential cultivars of melon, the Shiga strains were classified as race 1 of F. oxysporum f. sp. melonis, which has not been reported in Japan. To further characterize their pathogenicity, the strains were used to inoculate 46 additional cultivars of melon, oriental melon and oriental pickling melon. All the race 1 strains were pathogenic to the cultivars tested, and their host range was apparently different from those of strains belonging to other races (races 0, 2 and 1,2y). DNA fingerprinting with a repetitive DNA sequence, FOLR3, differentiated race 1 strains from strains of races 0 and 2, but not from race 1,2y strains. Received 2 July 1999/ Accepted in revised form 30 September 1999  相似文献   

3.
Simultaneous inoculation with races 1 and 2 of the vascular wilt pathogenFusarium oxysporumf.sp.lycopersiciprovided a high level of protection against race 2 in three tomato cultivars carrying resistance geneI, which confers resistance to race 1 but not race 2. However, simultaneous inoculation did not provide any protection in cultivars lacking this gene. Protection resulted in reduction and delay of wilt symptoms. Similarly, avirulent races ofF. oxysporumf.sp.melonisprotected muskmelon plants against virulent races of the sameforma specialis.A ratio 10:1 between spore concentrations of inducer and challenger organism gave the highest cross protection, but ratio 0.1:1 still provided significant disease reduction. Cross protection was also obtained when inoculation with the inducer organism was performed 6 or 12 h before inoculation with the challenger organism. Autoclaved spores of the inducer did not have any protective effect, indicating that living propagules were required to initiate protection. The results suggest the presence of a gene-for-gene interaction betweenF. oxysporumf.sp.lycopersici-tomato andF. oxysporumf.sp.melonis-muskmelon, in which cross protection against a virulent race is mediated by recognition of a specific elicitor from the avirulent race by the plant resistance gene product and by subsequent induction of the plant defense reaction.  相似文献   

4.
The aim of this study was to assess the biocontrol capacity of rev157, a non-pathogenic mutant of a pathogenic strain of Fusarium oxysporum f. sp. melonis (Fom24). Inoculated in association with the virulent parental strain, the mutant rev157 did not protect the host plant (muskmelon) against infection by Fom24. Applied on flax, a non-host plant, the mutant rev157 was not able to protect it against its specific pathogen F. oxysporum f. sp. lini. On the contrary the parental strain Fom24 did protect flax as well as a soil-borne biocontrol strain (Fo47). Since the mutant rev157 was affected neither in its growth in vitro nor in its capacity to penetrate into the roots, it can be speculated that the mutation has affected traits responsible for interactions within the plant. In F. oxysporum the pair of strains Fom24/rev157 is a good candidate to identify genes involved in the biocontrol capacity of F. oxysporum and to test the hypothesis of a link between capacity to induce the disease and capacity to induce resistance in the plant.  相似文献   

5.
Fourty-four strains of Fusarium oxysporum were isolated from plants of melon with Fusarium wilt symptoms. Among these strains, thirty-nine were characterized for their pathogenicity on melon. Thirty-seven strains belonged to known races of F. oxysporum f. sp. melonis, while two strains were non-pathogenic. Four strains belonged to race 0, seven to race 1, four to race 2, and twenty-two to race 1,2. Beauvericin was produced by thirty-six strains in a range from 1 to 310gg–1. Eight isolates of race 1,2 did not produce the toxin. In addition, of the two non-pathogenic strains, only one strain produced the toxin (290gg–1). The production of enniatin A1, enniatin B1, and enniatin B was also investigated. Enniatin B was the only enniatin detected, being produced by eleven strains belonging to all the races, with a range of production from traces to 60gg–1. Finally, melon fruits belonging to two different cultivars (Cantalupo and Amarillo) were artificially inoculated with one strain of F. oxysporum f. sp. melonis (ITEM 3464). Beauvericin was detected in the fruit tissues of both cultivars at a level of 11.2 and 73.8gg–1, respectively. These data suggest that the production of both the toxins is not related to the pathogenicity of F. oxysporum f. sp. melonis, nor to the differential specificity of the races. The results confirm that beauvericin is a common metabolite of phytopathogenic Fusarium species.  相似文献   

6.
Fusarium oxysporum f. sp. melonis is an important vascular wilt pathogen of melon. Races 1, 2 and 1–2 of this fungus have been identified in Portugal by pathogenicity tests with appropriate hosts. The aim of this research was to examine the relationships between different races of F. o. melonis of Portuguese and French origin through analysis of random amplified polymorphic DNAs (RAPDs). DNA fingerprint profiles were developed for all the accessions. Each isolate showed 5–10 DNA bands with each of the 16 primers employed. A total of 126 bands was obtained. The size of amplified DNA fragments generated with these primers ranged from 0.5 to 3.2 kb. A phenogram based on the Jaccard coefficient of similarity was computed by the unweighed pair group method using arithmetic averages (UPGMA). It was found that Portuguese race 2 is very similar to French race 1, while French race 2 is the most dissimilar being clearly separated from all other races. The genetic diversity of these isolates is also being studied for vegetative compatibility by using the nit mutant system.  相似文献   

7.
Two races ofFusarium oxysporum f. sp.melonis were identified among 54 isolates of this pathogen, tested on three differential lines of melon. Of the two races, race 0 was the more prevalent, comprising 92.5% of the total number of isolates tested. Race 1 has been encountered so far in one growing area only. The identity of the local races is compared with those defined in France and in two areas of melon-growing in California.  相似文献   

8.
Fusarium wilt of melon caused by Fusarium oxysporum f. sp. melonis is a destructive fungal disease in melon growing regions. Isolates of F. oxysporum obtained from six major melon producing provinces in Iran, from melons and other hosts, were characterized based on pathogenicity to melon, vegetative compatibility groups (VCGs) and nuclear ribosomal DNA intergenic spacer (IGS) sequencing. Thirty-four of 41 isolates from Iran in this study were identified as race 1,2 which belonged to either VCG 0134 or an unassigned VCG, which based on IGS sequencing grouped with the VCG 0135 tester isolate. The seven remaining isolates were identified as nonpathogenic to melon belonging to two undescribed VCGs. Based on sequence analyses of the IGS region of Iranian and foreign isolates, nine lineages were identified, each including one VCG. The separation of VCGs into distinct lineages based on IGS sequences is mostly consistent with Repetitive extragenic palindromic PCR (Rep-PCR) results. Exceptions are VCGs 0130 and 0131, which could be differentiated with IGS sequences, but not with Rep-PCR. Different races from the USA, France and Iran associated with VCG 0134 grouped into one IGS lineage but could be differentiated with Rep-PCR, suggesting that this VCG is more diverse than previously thought. Given the long history of melon cultivation in Iran and the Rep-PCR diversity of isolates belonging to this VCG, it could be speculated that VCG 0134 perhaps evolved in Iran.  相似文献   

9.
Fusarium wilt of melon, caused by Fusarium oxysporum f.sp. melonis (Fom), is an important disease; races of the pathogen were identified by inoculating differential standard host cultivars. A total of ten isolates that were obtained from 23 fields located in four different geographical regions were identified as pathogenic. Results indicate that all four known Fom races, namely, 0, 1, 2 and 1.2, were found in north and middle Tunisia. Race 1.2 was the most prevalent.  相似文献   

10.
Tomato fields of cultivars possessing I genes for resistance to race I ofFusarium oxysporum f. sp.lycopersici were surveyed in Israel during the years 1963-1973 for the appearance of race 2, to which they are not resistant. Race 2 was found throughout the investigated periods in a total of 49 locations in 31 settlements, on all cultivars, and in increasing incidence with time. In greenhouse tests race 2 isolates were pathogenic to i i and I cultivars but not to a cultivar resistant to race 2. A detailed study was carried out in the Tel Mond area where tomatoes are grown widely. In 1971/72, race 2 was detected in 11 out of 12 fields, and in 1972/73 in 10 out of 14 fields. Its occurrence was related to frequent tomato cropping. The implications of its spread are discussed.  相似文献   

11.
Tomato plants, susceptible toFusarium oxysporum f. sp.lycopersici, were inoculated by immersing the roots in a conidial suspension ofF. oxysporum f. sp.lycopersici race 1,F. oxysporum f. sp.dianthi race 2 or a mixture of both fungi. Plants inoculated withF. oxysporum f. sp.lycopersici showed disease symptoms after 2 weeks, whereas plants inoculated withF. oxysporum f. sp.dianthi or a mixture of both fungi remained symptomless for over 7 weeks, the duration of the experiment. In another experiment root systems of plants were split and each half was separately inoculated. One half was firstly inoculated withF. oxysporum f. sp.dianthi or treated with water, followed after a week by a second inoculation of the other half withF. oxysporum f. sp.lycopersici or by a water treatment. The disease symptoms in the half firstly inoculated withF. oxysporum f. sp.dianthi were significantly delayed, compared to plants of which that half had been treated with water. BecauseF. oxysporum f. sp.dianthi reduced disease symptoms caused byF. oxysporum f. sp.lycopersici without any direct interaction with this pathogen, it is concluded thatF. oxysporum f. sp.dianthi is able to induce resistance againstF. oxysporum f. sp.lycopersici in tomato plants.  相似文献   

12.
Fusarium wilt of tobacco could be caused by Fusarium oxysporum f. sp. batatas or f. sp. vasinfectum since f. sp. nicotianae was rejected because there was no evidence of isolates specific to tobacco. Forty isolates of F. oxysporum from soil and plants from tobacco fields in Extremadura (south-western Spain) were characterized by pathogenicity on burley and flue-cured tobacco, for vegetative compatibility group (VCG), and by random amplified polymorphic DNA (RAPD). Isolates from burley were identified as race 1 of F. oxysporum f. sp. batatas based on pathogenicity on tobacco, sweet potato and cotton, and those from flue-cured as race 2. Most isolates from soil were heterokaryon self-incompatible (HSI) and the remaining isolates from soil and tobacco were grouped into four VCGs: VCG 1 (5 isolates from burley), VCG 2 (17 isolates from flue-cured and 4 from soil), VCG 3 (2 isolates from flue-cured) and VCG 4 (2 isolates from soil). This is the first report of the two races and VCGs of F. oxysporum f. sp. batatas in Spain. Analysis of RAPD revealed two clusters (C-I and C-II) related to race and VCGs. C-I included race 1 (VCG 1) isolates from burley and nonpathogenic (VCG 4 or HSI) isolates from soils. C-II included nonpathogenic (VCG 2) and race 2 (VCG 2 or VCG 3) isolates from flue-cured. VCG and RAPD markers were effective in distinguishing race 2 from race 1, suggesting that there are two genetically differentiated groups of F. oxysporum f. sp. batatas on tobacco in Extremadura.  相似文献   

13.
Two soil-borne fungal endophytes almost completely suppressed the effects of a post-inoculated and virulent strain of Fusarium oxysporum f. sp. melonis when inoculated to axenically reared melon seedlings in Petri dishes. They were identified as Cadophora sp. on the basis of ITS 1–5.8S rDNA–ITS 2 sequences and morphological characters and obtained from the roots of Chinese cabbage grown as bait plants in a mixed soil made up of samples from different forest soils from Alberta and British Columbia, Canada. Hyphae of Cadophora sp. grew along the surface of the root and colonized root cells of the cortex and reduced the ingress of the Fusarium pathogen into adjacent cells. Melon seedlings pre-inoculated with Cadophora sp. were also grown in soil amended with the different N sources, nitrate or the amino acids leucine and valine, and glucose (final C:N ratio?=?10:1). After 4 weeks, these seedlings were transplanted into the field and disease symptoms were assessed. Only the endophyte-inoculated seedlings treated with valine could effectively inhibit the development of Fusarium wilt in two plots and reduced disease symptom development by 43 and 62 %.  相似文献   

14.
A muskmelon (Cucumis melo L.) breeding line, PI-124111F, is a seventh-generation selection derived from PI-124111, which is resistant to downy mildew (Pseudoperonospora cubenis pathotype 3), powdery mildew (races 1 and 2 ofSphaerotheca fuliginea) and Fusarium wilt (Fusarium oxysporum f. sp.melonis, races 0, 1 and 2). This is the only breeding line known to carry multiple-race resistance to these diseases. PI-12411IF is a monoecious muskmelon with poor fruit characteristics.  相似文献   

15.
The vascular wilt pathogen Fusarium oxysporum f. sp. melonis causes worldwide yield losses of muskmelon. In this study, we characterized a UV-induced non-pathogenic mutant (strain 4/4) of F. oxysporum f. sp. melonis, previously identified as a potential biological control agent. During comparative analysis of vegetative growth parameters using different carbon sources, mutant strain 4/4 showed a delay in development and secretion of extracellular enzymes, compared to the wild type strain. Amendments of the growth medium with yeast extract, adenine or hypoxanthine, but not guanine, complemented the growth defect of strain 4/4, as well as secretion and partial activity of cellulases and endopolygalacturonases, indicating that the strain is an adenine auxotroph. Incubation of strain 4/4 conidia in adenine solution, prior to inoculation of muskmelon plants, partially restored pathogenicity to the mutant strain.  相似文献   

16.
Dry fungal biomass ofPenicillium chrysogenum (dry mycelium), a waste product of the pharmaceutical industry, was extracted with water and applied to the roots of melon plants before or after inoculation withFusarium oxysporum f.sp.melonis (Font). Seedlings (4–6 days after emergence) treated with either acidic dry mycelium extract (DME) or neutralized dry mycelium extract (NDME) were protected against challenge infection withFom. A single drench with 2–5% DME applied 12–72 h before inoculation provided significant control of the disease compared with water-drenched, challenged seedlings. No protection was seen in plants treated 0–6 h before inoculation or 0–48 h after inoculation. Neither DME nor NDME (0.5–5%) had any effect on fungal growthin vitro, which implied that disease controlin vivo was mediated by induced resistance. The resistance induced by DME protected melon plants not only against race 1,2, but also against the three other races of the pathogen, indicating a race-non-specific resistance againstFom. Both DME and NDME significantly increased peroxidase activity and free L-proline content in seedlings 12 h and 48 h after soil drench, respectively. Resistance to Fusarium wilt was significantly associated with elevated levels of peroxidase activity but not with free L-proline content. Thus, peroxidase might be involved in the defense mechanisms activated by DME or NDME. http://www.phytoparasitica.org posting Aug. 31, 2001.  相似文献   

17.
Mitochondrial DNA (mtDNA) extracts from 13 isolatesof Fusarium oxysporum f. sp.niveum, including 12 from widely separated geographic regions within the United States and representing the three races, and one race 2 isolate from Israel, were examined for the presence of plasmid DNA and were also subjected to restriction endonucleases analysis. None of the mtDNA from any isolate had a copurifying plasmid. The estimated size of mtDNA fromF. o. f. sp.niveum race 0, calculated as the average of the sum of restriction fragment sizes, was 45.1 ± 2.2 kb. The restriction enzymesBamHI, EcoRI, Hpal, HindIII andMbol resolved 2, 4, 9, 21, and more than 40 fragments, respectively, but no polymorphisms were observed among the 13 isolates with any of these endonucleases. However, PstI digestion showed three distinct polymorphic patterns among the isolates. Each appeared to derive from point mutations that resulted in a change of one or more restriction sites. The most common pattern was present in nine of the isolates (three of race 0, four of race 1, and two of race 2) and included a 1.5 kb fragment. A second polymorphic pattern occurred in three USA isolates (one each of race 0, race 1 and race 2) and was characterized by an apparent replacement of the 1.5 kb fragment by 0.6 and 0.9 kb fragments. The Israeli isolate [ISL-59(73) race 2| had a unique pattern lacking the 1.5 and 2.0 kb fragments present in the common pattern and, instead, had 0.6, 0.9 and 3.0 kb fragments. The mtDNA polymorphisms observed among the USA isolates were not correlated with either pathological race or geographic region of origin.  相似文献   

18.
One hundred and sixteen isolates of Fusarium oxysporum f. sp. lactucae obtained from 85 fields in three crisphead lettuce-producing areas in Nagano Prefecture, Japan were typed for races using differential cultivars Patriot, Banchu Red Fire and Costa Rica No. 4. They were also grouped into vegetative compatibility groups (VCGs) using complementation tests with nitrate non-utilizing (nit) mutants. Two California strains reported as F. oxysporum f. sp. lactucum, a type culture of F. oxysporum f. sp. lactucae, and 28 avirulent isolates of F. oxysporum obtained from crisphead lettuce were included for comparison. Among Nagano isolates, 66 isolates were identified as race 1, and 50 as race 2. Race 1 strains derived from Shiojiri and Komoro cities and race 2 from Kawakami village and Komoro city. All isolates of race 2 were biotin auxotrophs, and the race could be distinguished based on its requirement for biotin on minimal nitrate agar medium (MM). Pathogenic isolates were classified into two VCGs and three heterokaryon self-incompatible isolates. Strong correlations were found between race and VCG. All the race 1 strains were assigned to VCG 1 except self-incompatible isolates, and all the race 2 strains to VCG 2. The 28 avirulent isolates of F. oxysporum were incompatible with VCG 1 and VCG 2. California strains was vegetatively compatible with VCG 1, and they were assigned to race 1. Based on vegetative compatibility, these two races of F. oxysporum f. sp. lactucae may be genetically distinct, and F. oxysporum f. sp. lactucae race 1 is identical to F. oxysporum f. sp. lactucum. Received 7 May 2002/ Accepted in revised form 6 September 2002  相似文献   

19.
Samenvatting In grondextract waaraan een kleine hoeveelheid glucose werd toegevoegd, vormtFusarium oxysporum f. sp.melonis overvloedig chlamydosporen. Gedurende een incubatieperiode van 30 dagen neemt het aantal chlamydosporen toe met stijgende glucoseconcentratie (10–1000 ppm). 98% van de gevormde chlamydosporen kiemde na 7 uren incubatie in vers medium of in steriele grond.  相似文献   

20.
Thirty-four isolates ofFusarium oxysporum f.sp.melonis (F.o.m.) obtained from 205 fields in melon-producing areas in the southeastern Anatolia Region of Turkey were identified on the basis of colony morphology and pathogenicity by the root dip method. In this region the mean prevalence of wilt disease was 88.1% and the mean incidence of disease was 47.5%. Physiologic races 0, 1, 2, and 1,2 of the pathogen were determined by their reactions on differential melon cultivars ‘Charentais T,’ ‘Isoblon’, ‘Isovac’ and ‘Margot’ in the greenhouse. Race 1,2, representating 58.8% (20/34) of all isolates, was widely distributed. Of the other pathogenic isolates, eight were identified as race 0, five as race 1, and one as race 2. This is the first report of physiologic races ofF.o.m. in Turkey. Of 44 melon cultivars tested in the greenhouse for resistance toF.o.m. races, 36 were found to be moderately resistant to race 0, 17 were susceptible to race 1,2, 34.1% were highly resistant to race 1, and 52.2% had moderate resistance to race 2. http://www.phytoparasitica.org posting July 16, 2002.  相似文献   

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