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1.
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   

2.
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   

3.
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   

4.
Cells of ring rot bacteria,Corynebacterium sepedonicum, obtained from ring-rotted potato tubers were used to contaminate various surfaces found in storage areas and on machinery and clothing. The bacteria survived for at least 10 months on most of the surfaces when held in an unheated machine shed, and on burlap when held in a root cellar.  相似文献   

5.
Some disinfestants are claimed to be more effective than others in controlling ring rot (Corynebacterium sepedonicum) and blackleg (Erwinia carotovora varatroseptica) bacteria on contaminated surfaces. Of the readily available disinfestants tested mercuric chloride (0.1%) and formaldehyde (2% and 5%) were the most effective against blackleg bacteria, and bleach (10%) mercuric chloride (0.1%) and formaldehyde (5%) were the most effective against ring rot bacteria on metal, wooden and burlap surfaces.  相似文献   

6.
Blue mold of tobacco, caused by Peronospora tabacina, is a serious disease with severe commercial impact. Quarantine measures to reduce pathogen distribution affect commercial trade of tobacco even in processed stages, but survival of the pathogen after curing at high temperature or exposure to sunlight has not been investigated adequately. To assess the effect of heat and UV-light on viability and infectivity of P. tabacina, sporangia of two different strains and sporulating leaves were exposed to temperatures up to 70 °C and UV irradiation at 254 and 366 nm. Sporangial germination of both strains strongly decreased within 48 h at temperatures above 16 °C, but 1–3% of sporangia still survived 24 h treatment at 70 °C. When sporulating leaves were used to inoculate fresh tobacco, reinfection occurred with samples kept for 48 h at 50 °C, whereas no infection resulted when the inoculum had been stored at 70 °C for at least 24 h. Exposure to 254 nm UV-light was deleterious to sporangial germination and killed them within 30–40 min. In contrast, sporangia treated at 366 nm survived for more than 4 h. Similarly, sporulating leaves exposed to 254 nm were infective to fresh tobacco, when irradiation time remained below 40 min. The results suggest that thermal treatment of at least 70 °C in post-harvest processing is necessary to prevent infection risks from commercially used tobacco. Alternatively, short-term irradiation with 254 nm UV light could be used for quarantine management, if it does not affect the product quality.  相似文献   

7.
Breeding and selection for frost resistant potatoes with high yield and good quality is very promising. This has been demonstrated in a frost resistance breeding program conducted at the International Potato Center, Lima, Peru. Yield trials were conducted using selected frost resistant clones at various Andean locations at elevations from 3,200 to 3,900 meters (14). During the growth season, several hail storms and frosts occurred at these locations. These freezes (?3°C to ?4°C) were very useful in elimination of the undesirable clones under natural conditions. Clones with yield from 1 to 2 kg/plant have been selected. A yield of 1 to 2 kg/plant was superior to most common cultivars grown in the Andes. The difference in frost resistance between a resistant and sensitive type of potato is about 3 to 4°C.Solanum tuberosum is a sensitive type which, in most cases, can survive at about ?2.0°C. Evidence indicates that the difference in resistance to freezing injury is due to the genotype’s capability to tolerate freeze-induced dehydration and to withstand the aggregation of proteins under freezing stress. It is likely that freezing injury is caused primarily by the loss of membrane integrity and, therefore, that membrane thermal stability is paramount in the tolerance to freezing stress.  相似文献   

8.
The bacterial soft rot potential in potato tubers was affected by differences in temperature between tubers and suspensions ofErwinia carotovora at the time of inoculation by immersion. In general, disease severity after incubation was higher when tuber temperatures were higher as opposed to equal to or lower than that of water containing cells of the bacterium. Disease severity was also greater when tubers were stored at 20° to 23°C in contrast to 4° or 26° to 30°C for 16–18 h prior to immersion. Tubers with a pulp temperature of 8°C were more prone to bruise injury as compared with those at 18°C when struck with a pendulum type bruising instrument. When the injured tubers were inoculated and incubated, most bruises became infected with soft rot bacteria.  相似文献   

9.
Thermodynamic properties of bread dough (fusion enthalpy, apparent specific heat, initial freezing point and unfreezable water) were measured at temperatures from −40 °C to 35 °C using differential scanning calorimetry. The initial freezing point was also calculated based on the water activity of dough. The apparent specific heat varied as a function of temperature: specific heat in the freezing region varied from (1.7–23.1) J g−1 °C−1, and was constant at temperatures above freezing (2.7 J g−1 °C−1). Unfreezable water content varied from (0.174–0.182) g/g of total product. Values of heat capacity as a function of temperature were correlated using thermodynamic models. A modification for low-moisture foodstuffs (such as bread dough) was successfully applied to the experimental data.  相似文献   

10.
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   

11.
The effect of freezing on the chemical composition of Katahdin and Atlantic potatoes was studied. Tubers were exposed to a temperature of ?20°C for 24 hrs., then thawed for 1 hr. at 20°C prior to analysis. Frozenthawed tubers were compared with unfrozen controls for total lipid, phospholipid, fatty acid and mineral content. Following freezing, a significant (p<.01) decrease was observed in crude lipid and phospholipid content of both cortex and pith sections. Generally, an increase in palmitic acid and a decrease in linolenic acid occurred in the phospholipid fractions of both varieties. A decrease in both macro and micro mineral content also occurred following freezing.  相似文献   

12.
Summary Potato cultivars were grown in a glasshouse and plants periodically transferred to a growth chamber. When the ambient temperature in the growth chamber was raised from 15 to 40°C in steps of 5°C per hour, net photosynthetic rate decreased at temperatures above 20°C. At 40°C the rate was 37% of the rate at 20°C. A greater decrease in net photosynthetic rate occurred with plants of the cultivar Up-to-Date than with cultivars R100 and BP13. Low values of leaf diffusive resistance were recorded and changes in photosynthetic rate could not be explained by changes in this factor. When a constant ambient air temperature of 20°C was maintained while soil temperature was increased, net photosynthetic rate decreased.  相似文献   

13.
Strains ofPseudomonas solanacearum differed in their ability to infect tubers of different resistant potato clones grown in infested soil. When eight resistant clones (Solanum phureja orS.phureja ×S. tuberosum hybrids) were grown at 24–28°C in soil infested with a race 1 or a race 3 strain of the bacterium, relatively few plants had wilt symptoms at harvest, but 26.7% and 9.2% of the tubers harvested from plants infected with the race 1 and race 3 strains, respectively, carried latent infections. Some infected clones never yielded diseased tubers, however. The development of symptoms above ground was not correlated with the incidence of tuber infection in any particular clone. No tuber infection occurred in tolerant or resistant clones grown in infested soil at cool (12–22°C) temperatures. Tubers were inoculated directly in an attempt to evaluate the ability of bacteria to multiply in these tissues at different temperatures. Highly virulent strains ofP. solanacearum survived in susceptible tubers in higher numbers and for longer periods than in resistant ones. Low temperature (4°C) had a deleterious effect on survival of the bacterium in tubers, but did not completely eliminate the pathogen even after 40 days.  相似文献   

14.
The effect of freezing on the turgor, ascorbic acid content and enzymatic discoloration of Katahdin and Atlantic potatoes was studied. Tubers were exposed to a temperature of ?20°C for 24 hrs. then thawed for 1 hr. at 20°C before analysis. Frozen tubers were then compared with unfrozen controls. Both varieties lost turgor following freezing and exuded a sticky liquid with increased thawing time. At the end of 3 hrs. thawing, a sponge-like texture was observed in both varieties. In both varieties freezing resulted in a significant reduction (p<.01) in ascorbic acid and phenolic content (p<.01). Enzymatic discoloration was also significantly reduced (p<.01) in both varieties.  相似文献   

15.
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   

16.
The incidence of tuber decay in rail car shipments of potatoes from the State of Washington was determined from 1965 to 1969 inclusive. Reinspection certificates revealed that 7.9% of the rail cars of potatoes shipped during this period were rejected due to tuber defects; tuber decay accounted for 63% of these rejected cars. Percentage of rejections due to tuber decay was greater for Russet Burbank than for Norgold Russet potatoes. Temperature, moisture, and oxygen levels influenced development of bacterial soft rot in freshly harvested potatoes and in potatoes stored for 3 months at 35 F (2 C) previous to treatment. When tuber surfaces were kept dry, no soft rot developed in 11 days over ranges of 50–70 F (10–21 C) and 2–20.5% oxygen levels. Freshly harvested tubers partially immersed in water did not rot when cooled to 40 F (4.4 C) in < 24 hours and held for 8 days under either 20.5 or 4% oxygen levels; however, tubers, rotted when stored similarly but at 50 F or higher temperatures. Partially immersed tubers incubated for 1 day or longer at 70 F developed soft rot in a low oxygen (4%) when later stored for, 8 days at 40 F. When rot occurred, the amount was always greater under lower oxygen levels irrespective of storage temperature. Of various cooling methods tested in rail cars loaded with 100 lb (45.4 kg) sacks of potatoes, prechilling of tubers and icing of cars prior to loading lowered floor temperatures most rapidly. Icing cars after loading lowered floor temperatures the slowest. In a carton shipment, the temperature remained above 68 F (20 C) in cartons after 8 days in transit, even though the wall and floor temperatures had cooled to near 55 F (12.8 C) by the second day. Oxygen level surrounding, tubers in the center of car loads of 100 lb sacks of potatoes was approximately 20.5% after 8 days transit.  相似文献   

17.
Potato spindle tuber viroid (PSTV) infected foliage and tuber tissues when subjected to repeated freezing and thawing under controlled conditions (?18 to ? 20 C and 5 C), lost PSTV more rapidly in tuber tissues than in foliage. Tubers of 17 potato cultivars showed similar tendencies, but with some differences. In 7 of the 17 cultivars, PSTV was significantly reduced after one freeze-thaw treatment, and in 6 of the 17 cultivars, infectious PSTV was still recoverable after exposure to 4 cycles of freeze-thaw. Exposure of PSTV-infected tubers to outdoor temperature fluctuations (13.1 C to ?15.1 C) resulted in complete loss of PSTV from the tubers.  相似文献   

18.
Summary Sprout growth in a range of European cultivars was studied over two seasons at constant temperatures from 2 to 25°C, with an additional 33 (day)/22°C (night) treatment in the second season. There were only minor differences in the response of the cultivars and the optimum for sprout growth was at 15–18°C in all cases, when measured over an extended period, but initially sprout growth was more rapid at 23–25°C. Sprout growth at 23–25°C was frequently arrested by sub-apical necrosis, and at these temperatures the sprouts remained short enough for the tubers to be planted by hand without desprouting.  相似文献   

19.
A study was conducted to determine the feasibility and advantages of wound-healing potatoes at lower than recommended temperatures. The progress of wound-healing at 6, 9, and 16°C, of tissue taken from Russet Burbank potato tubers, was evaluated by inducing weight loss with high temperature or decay organisms following various curing intervals. Increasing the wound-healing temperature resulted in a greater resistance to weight loss and a decreased susceptibility to infection byErwinia carotovora subsp.carotovora. Resistance to weight loss increased as wound-healing temperature increased following 6 and 16 day intervals. However, weight loss induced after 21 days of healing appeared to level off at 9°C indicating maximum development of a wound barrier. Loss due to rot, after inoculation of fresh cores withE. carotovora, was directly proportional to incubation time and temperature. When wound-healing progress was measured by loss of fresh weight induced by elevated temperatures or rot, the advantages of woundhealing at 16°C compared with 9°C decreased significantly after 21 days of curing. Wound-healing at approximately 9°C for 25 days was found to be the best compromise temperature for keeping rot progress and weight loss at a minimum while allowing the process of healing and maturation to occur.  相似文献   

20.
Growth of 6 potato virus S (PVS)-infected potato clones in tissue culture in temperature regimes alternating between supraoptimal (40°C–45°C) and optimal (25°C) temperatures was compared to incubation of etiolated shoots at constant moderate temperatures (37°C) to obtain virus-free plants by shoot tip culture. Both procedures were effective in obtaining PVS-free propagative material. Virus-free plants were obtained in 5 of 6 clones by the alternating temperatures procedure and in 4 of the 6 clones by the constant 37°C incubation prior to shoot tip isolation. Heat tolerance, virus inactivation, and development of pathogen-free buds from the heat-treated plants depended upon the potato cultivar and the type of culture media in which the tips grew, but these characteristics did not coincide in any clone. The variety Chieftain was the least tolerant to the high temperatures and no virus-free individuals were recovered. White Rose was the most heat resistant, but Russet Burbank resulted with the highest percentage of PVS-free plants. The virus was eliminated from the variety Kennebec only by the alternating temperature treatments. Exposing potato plantlets in the alternating temperature regimes prior to isolation and regeneration of shoot tips was slightly better than the traditional method of incubation of plants at constant moderate temperatures that the plant will withstand and offers a new option in freeing plants of more tenacious viruses.  相似文献   

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