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1.
The survival of the ring rot bacterium,Corynebacterium sepedonicum, on contaminated surfaces and in infected stems was investigated by root inoculating potato stem cuttings with aqueous suspensions prepared from these materials. The pathogen survived for 24 mo on contaminated surfaces of burlap, kraft paper, and polyethylene plastic held at 12% relative humidity (RH) at either 5 or 20°C. It persisted for less than 14 mo on surfaces held at 94% RH at either temperature. Infectious ring rot bacteria were also recovered from dried, infected potato stems held for 26 mo in an unheated machine shed. These results emphasize the importance of strict sanitation and disinfestation procedures in maintaining potato seed stocks free of bacterial ring rot.  相似文献   

2.
The ring rot bacterium,Corynebacterium sepedonicum (Spieck. and Kotth.) Skapt. and Burkh. [Clavibacter michiganense subsp.sepedonicum (Spieck et Kotth.) Davis et al.], and latent potato viruses (potato virus S and potato virus X) were investigated for their effect on atypical (ATYP) ring rot symptom development on Russet Burbank potato plants at different temperatures. Plants grown at 21 C from stem cuttings root-inoculated withC. sepedonicum developed typical wilting and chlorotic symptoms of ring rot that were equally severe on virus-free (VF) and virus-infected (VI) plants. All VF and VI plants grown at 15 C from inoculated stem cuttings exhibited ATYP symptoms that included extreme stunting, resetting, and chlorotic symptoms of ring rot. More severe ATYP symptoms developed on VI than on VF plants. Up to 5 wk after inoculation withC. sepedonicum, ATYP symptom severity ratings of both VF and VI plants increased and declined thereafter. The ATYP severity ratings were highly correlated with fresh weight of plants with high severity ratings being associated with low fresh weights. These results emphasize the need to determine the role of temperature and viral pathogens on ring rot symptomology in existing and newly developed potato cultivars and thereby enable better field detection of bacterial ring rot.  相似文献   

3.
The survival ofCorynebacterium sepedonicum, the bacterial ring rot pathogen, in infected potato stems and on burlap surfaces held at various freezing and above-freezing temperatures was investigated by root-inoculating potato stem cuttings with aqueous suspensions prepared from these materials. Infectious bacteria were recovered from dried Russet Burbank stems held for 44 mo in an unheated machine shed and from dried Warba stems held for 55 mo. Inoculum from dried stems of all cultivars held for 63 mo did not incite symptoms; however, inoculum from Russet Burbank stems incited symptomless infection in 10% of the inoculated plants. This 63-mo survival period exceeds a 26-mo survival period previously reported. Ring rot bacteria survived and remained infectious for at least 18 mo on burlap surfaces subjected to temperatures of ?40° to ?5°C, alternating temperatures of -5° to 5°C, or a constant temperature of 5°C. Inoculum from burlap stored at the lower temperatures caused the most severe symptoms. These results stress the need for keeping crop debris away from potato operations and for using proper decontamination procedures to maintain potato seed stocks free of ring rot.  相似文献   

4.
Some of the factors that affected ring rot development in potato plants grown from stem cuttings and root-inoculated withCoryncbacterium sepedonicum were investigated. Isolates ofC. sepedonicum cultured and stored for a, year on agar media were as virulent as those that had been cultured for almost 5 months. Isolates cultured for periods over 2 years gradually lost their virulence; however, decline in virulence was not as rapid as had been previously reported. One isolate became more virulent by inoculating and recovering it from a susceptible potato plant. Ring rot symptoms developed more rapidly in the cultivar Red Pontiac than in the cultivar Netted Gem; however, disease severity eventually reached the same level in both cultivars. The more mature the plants were when inoculated, the greater was the rate of ring rot development. Duration of exposure of wounded roots to inoculum of the pathogen did not affect disease development. No ring rot bacteria were recovered from plants originating from apical cuttings of ring-rot-infected potato plants that exhibited partial wilting. By this technique, plants infected withC. sepedonicum were freed from this pathogen quickly and effectively.  相似文献   

5.
The ring rot bacterium,Corynebacterium sepedonicum (Spieck. and Kotth.) Skapt. and Burkh., and latent potato viruses (potato virus S and potato virus X) were investigated for their effect on ring rot symptom development on potato plants in the greenhouse and on symptom development and yield of potatoes in the field. Both virus-free (VF) and virus-infected (VI) Red Pontiac stem cuttings root-inoculated with ring rot bacteria in the greenhouse developed typical (T) ring rot symptoms, and symptom severity did not differ between VF and VI plants. In a field study, both VF and VI Russet Burbank seed pieces knife-inoculated with ring rot bacteria produced plants with atypical (A) and T ring rot symptoms as well as a combination of both types. The data suggest that more A than T symptoms develop on VI plants and more T than A symptoms develop on VF plants. Combined infection with the ring rot pathogen and the latent potato viruses resulted in greater yield losses of total and marketable Russet Burbank tubers than infection with the bacterial or viral pathogens alone.  相似文献   

6.
Symptoms of bacterial ring rot (Corynebacterium sepedonicum) developed earlier and were more severe in root-inoculated potato plants grown from stem cuttings treated with indole-3-butyric acid (IBA) than in those grown from stem cuttings not so treated or from tuber seed pieces. Disease expression was more rapid and severe in root-inoculated plants than in plants from inoculated seed pieces. The use of IBA-treated stem cuttings provided uniform plant material for ring-rot studies.  相似文献   

7.
Corynebacterium sepedonicum was detected in symptomless potato stems and tubers with immunofluorescence using monoclonal antibodies specific for the bacterial ring rot pathogen. The concentration of bacterial cells in potato tissue preparations ranged from >500 cells/microscope field to 1 cell per preparation. Symptomless tubers containing ring rot bacteria planted in field plots yielded plants with ring rot symptoms, plants with latent ring rot infections, or plants with no detectable levels of ring rot bacteria. Tubers with the greatest number of bacteria were most likely to develop plants expressing ring rot symptoms, but even some seed tubers with a low number of bacteria developed into plants with symptoms. Some seed tubers with high levels of ring rot bacteria produced plants with only low numbers ofC. sepedonicum.  相似文献   

8.
The survival ofCorynebacterium sepedonicum, the bacterial ring rot pathogen of potatoes, on burlap surfaces held at constant freezing and above-freezing temperatures and under wide fluctuations of these temperatures was investigated by root-inoculating potato stem cuttings with aqueous suspensions prepared from these surfaces. The pathogen survived and remained infectious on burlap for 53 mo at all constant freezing temperatures, and its infectivity did not diminish throughout this period at either ?20 or ?40°C. At 42 months, viable ring rot bacteria were no longer detected at a constant temperature of 5°C. In a second experiment, ring rot bacteria survived and remained infectious on burlap for 23 months at fluctuating temperatures of ?40 to 5°C and ?40 to 25°C, but only survived for 12 months at 25°C. However, results of this study indicate that wide fluctuations between freezing and above-freezing temperatures caused decreased infectivity of the pathogen.  相似文献   

9.
《Field Crops Research》2005,91(2-3):125-130
Stem rot, a fungal disease caused by Sclerotinia trifoliorum Eriks., is often a serious problem in many important forage legumes including faba beans (Vicia faba L.). Understanding the inheritance of resistance to the disease is essential for effective breeding of resistant cultivars. Experiments were conducted to study the inheritance of resistance to stem rot of faba beans. The F1, F2, and the backcross generations of five crosses between four resistant and four susceptible populations (Alto × Polycarpe, A-90 × Polycarpe, ILB-1814 × A-247, A-90 × A-244, VT × Tanagra) were used. The eight populations were crossed properly in the field, and progenies of F1 and F2, as well as backcross progenies of F1 with each of their parents, were evaluated for resistance to stem rot disease under controlled conditions after artificial inoculation of the plants with carrot root pieces colonized by the fungus. On the assumption that inheritance of stem rot resistance is governed by a single dominant gene, no significant differences were found between the observed and the expected frequencies of resistance for progenies, except for one cross. As the expression of resistance to the disease fits the expected ratios for a single dominant gene model, it is concluded that the inheritance of resistance to sclerotinia stem rot in the evaluated faba bean populations is controlled by a single dominant gene.  相似文献   

10.
The volatile production characteristics of ring rot (Corynebacterium sepedonicum) and soft rot (Erwinia carotovora) infected potatoes were investigated under controlled conditions in order to assess the monitoring of volatiles as a technique for differentiating between the infections in stored potatoes. Total volatile production/unit time was much greater from soft rot due to more rapid development after infection. Total volatile production during the period required for the development of the soft rot infection was similar to the output detected during the longer period required for the development of the ring rot infection. The volatile profiles of the two pathogens featured a number of commonly shared metabolites, but one compound was unique to the ring rot infections and two compounds were unique to the soft rot infections. There were also consistent disease-specific changes in the relative concentration of many of the metabolites detected in the volatile profiles.  相似文献   

11.
Resistance to potato tuber soft rot caused byErwinia carotovora was transferred fromSolanum brevidens to the cultivated potato over the course of four backcross generations originating from a somatic hybrid. Soft rot reactions were determined via a tuber plug inoculation method developed during the course of these experiments. Soft rot resistance was highest in the somatic hybrid (only ca. 20% of tubers and plugs showed evidence of severe rotting) and lowest among progeny of control potato x potato crosses (ca. 80% of tuber plugs showed severe rot). Backcross generations involving somatic hybrids were intermediate in their reaction, and resistance stabilized to about 60% of tuber plugs showing severe rot in the BC2 through the BC4. Reciprocal crosses showed no difference in the inheritance of soft rot resistance, indicating that neitherS. brevidens norS. tuberosum donor cytoplasm had a significant effect on the expression of resistance. Crosses between BC3 siblings where noS. brevidens genetic markers were detected but resistance was segregating demonstrated a dosage effect for soft rot resistance. We conclude that introgression of soft rot resistance has occurred and that at least one locus responsible for resistance inS. brevidens now resides in theS. tuberosum genome.  相似文献   

12.
Netted Gem potato plants infected with either the ring rot bacterium (Corynebacterium sepedonicum) or the potato leaf roll virus alone exhibited typical symptoms of the respective diseases. Plants infected with both the bacterium and the virus exhibited severe leaf roll. Typical ring rot symptoms were masked in dual infections, thereby increasing the difficulty in detection of the bacterial disease. The combined yield-reducing effect of the two pathogens was greater than that of the potato leaf roll virus and was similar to that caused by ring rot alone.  相似文献   

13.
Bacterial ring rot-infected tuber and stem tissue reacted withCorynebacterium sepedonicum antiserum in agar immunodiffusion (AID). The AID test was as effective as immunofluorescence (IF) in confirming ring rot in potato tubers submitted for diagnosis. Precipitin bands developed in AID with tuber preparations that contained, in a 1:10 dilution of the preparation, at least 100 IF positive cells/microscope field with a 100 X oil objective. Only a low percentage of preparations with less than 100 IF positive cells were positive with AID. Samples inoculated withC. sepedonicum strains which produced non-mucoid colony types on YGM medium did not consistently develop precipitin bands in AID which suggests that the usefulness of the test may be limited where non-mucoid strains occur naturally.  相似文献   

14.
Potato ring rot, caused by the bacterium Clavibacter michiganensis subspecies sepedonicus, is considered to be one of the internationally most important seed potato diseases (Smith et al.; Eur J Plant Pathol 107:739–748, 2001) and has been a problem in Norwegian potato production since its first detection in 1964. Since 1965, Norway has had its own national legislation for the control of the disease. In recent years, this legislation has evolved to be more similar to the EU Commission Directive 2006/56/EC. In 1999, the Norwegian Food Safety Authority initiated an eradication program for potato ring rot with the aim of selling potatoes to other European countries. During the project period (1999–2008), efficient systems for sampling, analysis and eradication measures were built. From 1999 to 2002, the occurrence of potato ring rot in commercial potato production was monitored in all counties. Sampling was carried out according to the instructions of the Norwegian Food Safety Authority, while testing of samples was (from 2000 onwards) carried out by Bioforsk laboratories with modern serological and molecular detection methods. When ring rot was detected in a potato lot, the grower had to implement strict eradication measures. The survey was followed up with two monitoring periods, 2003–2004 and 2005–2008. During the project period, 328 cases of potato ring rot were found. The counties Hedmark, Nordland, Troms, and Tr?ndelag accounted for most of these. The main objectives of this study were to describe the occurrence of potato ring rot in Norwegian potato production and to evaluate the effectiveness of the eradication measures employed for the control of the disease. This survey showed that the overall ring rot situation did improve considerably during the project period (1999–2008), both in relation to prior periods, and when comparing the surveying and monitoring periods. Problem areas where monitoring must be continued remain.  相似文献   

15.
The bacterial ring rot disease of potato (Corynebacterium sepedonicum) can be detected in seed potato lots by serological tests with greater accuracy than by visual field inspections. Indexing tests can make use of highly specific immunofiuorescence probes, enzyme-linked immunosorbent assays, and perhaps other procedures. Sensitivity and specificity of these procedures need to be determined in order to estimate the confidence with which ring rot can be detected in a seed lot. In addition to the laboratory tests, the sampling strategy determines the efficacy and sensitivity of the indexing procedure. Samples might consist of stems, leaf petioles, or tubers in single or composite units. Disease incidence and number of plants sampled also determine the confidence level with which ring rot can be detected in a potato seed lot. Although research has been conducted on many aspects of ring rot testing procedures, further work needs to be done. Nevertheless, it is anticipated that indexing potato seed lots for the presence of ring rot will be a significant factor in control and eradication of the disease.  相似文献   

16.
The effect of total light energy levels on development of bacterial ring rot symptoms caused byCorynebacterium sepedonicum (Spieck. and Kotth.) Skapt. and Burkh., and growth (plant height) of cv. Red Pontiac was investigated by growing inoculated and uninoculated rooted stem cuttings under different pre-inoculation and post-inoculation total light energy levels. Infected plants grown under a 45 mW cm?2 hr pre-inoculation total light energy level had a higher (P< 0.01) mean ring rot severity rating than plants grown under 103 mW cm?2 hr. Disease severity increased as the postinoculation total light energy decreased. Plants inoculated withC. sepedonicum showed little growth under a post-inoculation total light energy of 45 mW cm?2 hr, however, under 103 mW cm?2 hr; significantly greater growth occurred. Uninoculated plants grew more rapidly than infected plants under all pre-and post-inoculation total light energy level combinations, except those grown at pre-inoculation levels of 45 mW cm?2 hr.  相似文献   

17.
Southern stem rot, caused by Sclerotium rolfsii Sacc., is a destructive soil fungal disease of peanut in China and other countries. To evaluate resistant germplasm, a total of 256 peanut accessions were investigated on their resistance to southern stem rot in 3 environments by artificial inoculation. Variance analysis indicated that disease index was significantly influenced by environment, genotype and genotype ​× ​environment interactions. Peanut accessions of var. vulgaris type exhibited higher resistance to southern stem rot. Disease index was significantly negatively correlated with linoleic acid content, while positively correlated with oleic acid content. Six resistant accessions were identified, including Hua 28, Shandongzai, ICG 6326, Quanhua 7, Quanhua 9 and Guihua 836, with their disease indexes under 40 and mortality were less than 30% in the three environments. The identified resistant accessions showed the great potential to be applied in resistant peanut breeding, and would be good genetic resources for enhancing the resistance to southern stem rot.  相似文献   

18.
The effect of moisture content and temperature on the persistence, in soil, of cells of the ring rot bacterium,Corynebacterium sepedonicum (Spieck. and Kotth.) Skapt. and Burkh., was followed with root-inoculated, rooted potato stem cuttings. Ring rot bacteria were still viable after 284 days in a sterilized Lethbridge silt loam moistened to field capacity and incubated at 15°C. However, the cells did not survive beyond 6 days in two non-sterile silt loams at field capacity and 20°C. In non-sterile Lethbridge silt loam, persistence of the pathogen increased as soil moisture content and temperature decreased. Cells persisted for 10 and 15 days, respectively, in soil at 50% field capacity held at 15 and 10°C. Ring rot bacteria were not recovered after 88 days from a non-sterile Lethbridge silt loam moistened to the wilting point and held at a temperature fluctuating between 10 and 20°C, or from soil at field capacity and at a temperature fluctuating between ?5 and +5°C. They survived for 362 days in soil at the wilting point at mean temperatures of 0 or ?10°C, but were not viable after 278 days in soil at field capacity and a mean temperature of ?10°C. In excised, infected potato stems held in a non-sterile Lethbridge silt loam, the pathogen persisted for 325 days in soil at the wilting point and a mean temperature of 0°C. These results suggest that soil infested with ring rot bacteria should be kept well moistened during warm periods to inactivate these bacteria and to ensure that they do not contaminate healthy tubers that may be stored or grown there later.  相似文献   

19.
In North Carolina (NC), USA, Pythium stem rot on tobacco is caused by Pythium aphanidermatum. During the past 10 years, Pythium stem rot incidence has been reported more frequently in tobacco fields than before. Since 1997, tobacco flue-cured cultivars carrying the Ph gene that confers immunity to race 0 of Phytophthora parasitica var. nicotianae (Ppn) have also been deployed in NC. It has been questioned whether the introduction of cultivars carrying this resistance gene contributes to the increased incidence of Pythium stem rot. We used a strain of P. aphanidermatum expressing the β-glucuronidase (GUS) reporter gene to investigate the susceptibility of stem and root tissues of four flue-cured tobacco cultivars to Pythium stem rot. Cultivars NC71 (carries the Ph gene) and RJR15 (no Ph gene, but highly resistant to Ppn) were less susceptible (P < 0.05) to P. aphanidermatum than K326 and K346 cultivars that do not carry the Ph gene. Furthermore, different parts of the plant demonstrated significant differences (P < 0.0001) to P. aphanidermatum infection although the significance depended on the cultivar. That is, in K326 and NC71 the highest percent infection was in the adventitious roots, followed by the stems and lastly the true roots, whereas in K346 and RJR15 the highest percent infection was in the adventitious roots, then the true roots and last in the stems. These results do not support the hypothesis that cultivars carrying the Ph gene may be more susceptible to Pythium stem rot than cultivars without the gene. It is likely that other reasons such as the reduction or absence of mefenoxam application in fields where cultivars carrying the Ph gene are planted or reduction in competition for infection cites with Ppn have contributed to the increase of Pythium stem rot incidence in tobacco fields in NC.  相似文献   

20.
The presence ofClavibacter michiganensis subsp.sepedonicus was detected by immunofluorescence and ELISA in diluent in which cores from 200 potato tubers had been incubated on a rotary shaker. By this procedure the ring rot pathogen was detected in composite samples from naturally infected tubers and tuber samples “spiked” with infected tissue or a pure culture of the pathogen. Populations of saprophytic bacteria increased about 100-fold in the diluent during 18 h of incubation but did not interfere with serological detection of C.m. sepedonicus. Some of the results suggest thatC. m. sepedonicus cells multiply during incubation of tuber samples. Extraction of ring rot bacteria from potato tuber tissue by incubation on a rotary shaker requires little work and minimizes the amount of plant tissue in the extract compared to the standard extraction procedure involving maceration and differential centrifugation.  相似文献   

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