The effect of injury and infection by Gibberella zeae on the polyacrylamide gel electrophoretic pattern of soluble proteins in potato tuber tissue

Polyacrylamide gel electrophoretic patterns of soluble proteinsfrom intact potato tubers and from wounded tuber tissue wereidentical. The patterns from diseased tissue showed some minordifferences not before 3–4 days after inoculation. Itis concluded that primarily proteins of minor fractions areinvolved in protein synthesis after wounding or infection. (Received March 22, 1969; )     

Infection of Potato Tubers with the Common Scab Pathogen Streptomyces scabiei in a Soil‐less System

A novel soil‐less method was developed to define susceptibility of developing potato tubers accurately to infection with Streptomyces scabiei the causal agent of common scab disease. Hydroponic production enabled precise identification of individual tuber development. Direct inoculation of tubers with a spore suspension of S. scabiei resulted in disease development, demonstrating that infection could be initiated in a soil‐less media. Tubers were most susceptible to infection between 3 and 20 days after tuber initiation, confirming that this early period of tuber formation is critical to disease development.     

Monitoring Spongospora subterranea Development in Potato Roots Reveals Distinct Infection Patterns and Enables Efficient Assessment of Disease Control Methods

Spongospora subterranea is responsible for significant potato root and tuber disease globally. Study of this obligate (non-culturable) pathogen that infects below-ground plant parts is technically difficult. The capacity to measure the dynamics and patterns of root infections can greatly assist in determining the efficacy of control treatments on disease progression. This study used qPCR and histological analysis in time-course experiments to measure temporal patterns of pathogen multiplication and disease development in potato (and tomato) roots and tubers. Effects of delayed initiation of infection and fungicidal seed tuber and soil treatments were assessed. This study found roots at all plant developmental ages were susceptible to infection but that delaying infection significantly reduced pathogen content and resultant disease at final harvest. The pathogen was first detected in roots 15–20 days after inoculation (DAI) and the presence of zoosporangia noted 15–45 DAI. Following initial infection pathogen content in roots increased at a similar rate regardless of plant age at inoculation. All fungicide treatments (except soil-applied mancozeb which had a variable response) suppressed pathogen multiplication and root and tuber disease. In contrast to delayed inoculation, the fungicide treatments slowed disease progress (rate) rather than delaying onset of infection. Trials under suboptimal temperatures for disease expression provided valuable data on root infection rate, demonstrating the robustness of monitoring root infection. These results provide an early measure of the efficacy of control treatments and indicate two possible patterns of disease suppression by either delayed initiation of infection which then proceeds at a similar rate or diminished epidemic rate.     

丛枝菌根真菌在田间的分布特征、代谢活性及其对甘薯生长的影响

研究了大田条件下丛枝菌根(AM)真菌的分布特征、代谢活性及其对甘薯的生长效应.结果表明,接种Glomus intraradices 8周后,甘薯地上部干重,薯块鲜重和薯块个数均明显高于不接种对照;植株地上部和根系的吸磷量显著提高.与不接种对照相比,接种处理的甘薯菌根侵染率、甘薯根外菌丝密度以及甘薯根内菌丝的活性(根内菌丝碱性磷酸酶活性)显著提高.进一步分析甘薯根际不同方位上的菌丝分布,发现接种处理中平行于垄的方向的菌丝密度显著高于苗子下方的菌丝密度,而不接种处理的各个方向总菌丝密度无差异;活菌丝(具琥珀酸脱氢酶活性的菌丝)密度在各个方向的分布规律与总菌丝密度的分布规律一致.接种后根内菌丝活性的增强,根外活性菌丝密度的增加及其分布特征的改变,是甘薯产量增加的主要原因.     

Some effects of supplying benzyladenine to leaves and plants inoculated with viruses

With tomato spotted wilt virus in petunia leaf strips, N-6 benzyladenine (BA) was as effective as kinetin in decreasing numbers of local lesions, a result which could not be attributed to an effect on the virus per se. Benzimidazole, adenine and ammonium nitrate were without effect. Benzyladenine was more effective than kinetin when supplied through the petioles of excised whole leaves. Local lesions and infectivity of TSWV in detached leaves of Nicotiana rustica were decreased by supplying BA before and after inoculation. Lesions and infectivity were also decreased in attached leaves when BA was applied 9 days before inoculation. BA supplied to attached leaves after inoculation increased infectivity. Supplying BA to the lower leaves of tomato plants before inoculating with TSWV decreased infectivity of unsprayed, systemically infected tip leaves taken as inoculum; BA supplied after inoculation increased infectivity. Local lesions caused by lucerne mosaic virus in excised leaves of Phaseolus vulgaris were decreased in number by supplying BA. The effects of pre- and post-inoculation sprays of BA are considered in relation to cell metabolism. Since pretreating leaves with kinins did not prevent infection, it is suggested that those which move freely through plants without adverse effects on normal growth may prove of value in increasing the tolerance of plants to virus infection.     

Ubiquinone systems of the genus Cladosporium and morphologically similar taxa

Abstract We measured adenosine deaminase (ADA) activity in a guinea pig model of Legionella pneumophila infection. Female Hartley guinea pigs were inoculated intraperitoneally with one-quarter of the LD₅₀ dose of L. pneumophila Philadelphia-1 strain. Control groups were inoculated with clinical isolates of Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae or Klebsiella pneumoniae . Each group consisted of 5 animals. ADA activity in plasma was assayed calorimetrically before and at various intervals after infection by measuring the amount of ammonia produced after adnosine was added to plasma samples. ADA activity before inoculation was 25.6±6.0 IU/1, it reached 174.4±60.0 IU/1 on day 3 after inoculation of L. pneumophila . ADA activity returned to normal levels on day 14. ADA activity did not increase significantly in guinea pigs infected with the other types of bacteria. These findings suggest that measurement of plasma ADA activity may be useful for the diagnosis of Legionella infection.     

The Influence of Carbohydrate and Mineral Nutrient Supply on the Growth of Potato Tubers

The uptake and distribution of nitrogen, phosphorus, and potassiumhas been studied throughout the life of potato plants. Thereappears to be a net loss of all three elements from the plantduring emergence growth even though uptake occurs. When daughtertubers are formed they very quickly become the dominant sinkfor mineral nutrients, the concentrations of N, P, and K remainingsteady for a long period. These concentrations are maintainedin spite of decreasing rates of uptake, indicating the transferenceof mobile ions from the haulm to the growing tubers. ¹⁴C tracer experiments have shown that after tuberization thereis a greater export of recently incorporated photosynthate fromthe leaves than takes place before tuberization. There is nogood correlation between the size of individual tubers and theamount of photosynthate transported into them. This is thoughtto be because the largest tubers are not necessarily growingfaster than the smaller tubers. The most active sinks are alsomost active in converting the mobile ¹⁴C into storage compounds.The mother tuber continues to import ¹⁴C until it is detachedfrom the plant, but over much of this period there is no changein the tuber dry-weight, indicating that there is an equivalentexport from the tuber. The similarities between these distribution patterns and thosefound in tubers showing second-growth are described and theimplications with respect to the control of tuber growth discussed.     

Population dynamics of Erwinia carotovora subsp. atroseptica on the surface of intact and wounded seed potatoes during storage

Population dynamics of Erwinia carotovora subsp. atroseptica (Eca) on the tuber surface during storage (2–4°C) and pregermination, were studied by plating extracts of 6 mm² point samples on crystal violet pectate medium. To investigate the effect of harvest damage on Eca survival, intact, skinned (epidermis removed), and peeled (complete peel removed) tubers from a dry (pF 3.4) and from a wet (pF 2.0) soil were inoculated either immediately after harvesting or after air drying for 4 h. Eca numbers on intact tuber surface decreased rapidly after inoculation, whereas at the skinned and peeled surface numbers were significantly increased 2 d after harvest. Tubers peeled and inoculated with Eca were rotted by 2 d after harvest while tubers peeled and dried before inoculation did not rot; however, populations were significantly increased 2 d after harvest. For all treatments Eca numbers per point sample decreased to below detection limits 180 d after harvest. Examination of 600 mm² surface samples of the various treatments 222 d after harvest showed that Eca populations were still present. The number of tubers contaminated with colony-forming units (cfu) of Eca was significantly lower for intact surface inoculated tubers from dry soil than for those of the other treatments. Drying for 4 h before inoculation resulted in a significant reduction of the number of Eca cfu positive tubers compared to all other treatments. The ELISA OD values of the 600 mm² surface samples at day 222 were almost all positive and showed only a slight difference between the average of the tubers containing culturable Eca cells and those without culturable Eca cells.     

The deletion of the pif gene improves the biosafety of the baculovirus-based technologies

Our goal was to improve the biosafety of baculovirus-based technologies by deleting the pif (per os infectivity factor) gene from baculovirus expression vectors. Such a deletion would block transmission in nature without disturbing protein production. A pif deletion mutant of Autographa californica multiplecapsid nucleopolyhedrovirus (AcMNPV) was constructed and its infectivity to two host species was tested by oral or intrahemocoelic inoculation. Virus replication after oral inoculation was monitored using PCR. Oral inoculations with a mixture of the wild type and the pif deletion viruses were carried out. The pif deletion blocked oral infection but it did not hamper infectivity in cell culture. The blockage took place early after inoculation and could not be overcome by mixed inoculations with the wild type. The cat gene was inserted under the control of the polyhedrin promoter in the deletion mutant and the wild type CAT yield was measured in Spodoptera frugiperda insect cells (Sf9) infected with either recombinant. The pif deletion did not hamper CAT production. This deletion significantly improved CAT yields early in the infection. Hence, expression vectors lacking pif may produce higher quality protein. The pif deletion is a simple measure that dramatically reduces the chances of virus spread or gene transfer in nature.     

Alleviation of plant virus infection by humic acids

K-humates, obtained from oxihumolites, alleviate infection of tobacco with tobacco mosaic virus both in mixture with virus inoculum and by spraying of leaves before inoculation. However, applications of K-humates after inoculation did not influence the virus infectivity.     

Aquatic plant shows flexible avoidance by escape from tuber predation by swans

Deeper burial of bulbs and tubers has been suggested as an escape against below-ground herbivory by vertebrates, but experimental evidence is lacking. As deep propagule burial can incur high costs of emergence after dormancy, burial depth may represent a trade-off between sprouting survival and herbivore avoidance. We tested whether burial depth of subterraneous tubers is a flexible trait in fennel pondweed (Potamogeton pectinatus), facing tuber predation by Bewick's swans (Cygnus columbianus bewickii) in shallow lakes in winter. In a four-year experiment involving eight exclosures, winter herbivory by swans and all vertebrate summer herbivory were excluded in a full-factorial design; we hence controlled for aboveground vertebrate herbivory in summer, possibly influencing tuber depth. Tuber depth was measured each September before swan arrival and each March before tuber sprouting. In accordance with our hypothesis, tuber depth in September decreased after excluding Bewick's swans in comparison to control plots. The summer exclosure showed an increase in tuber biomass and the number of shallow tubers, but not a significant effect on the mean burial depth of tuber mass. Our results suggest that a clonal plant like P. pectinatus can tune the tuber burial depth to predation pressure, either by phenotypic plasticity or genotype sorting, hence exhibiting flexible avoidance by escape. We suggest that a flexible propagule burial depth can be an effective herbivore avoidance strategy, which might be more widespread among tuber forming plant species than previously thought.     

Changes in the activities of antioxidant enzymes in response to virus infection and hormone treatment

Activities of enzymes involved in the detoxification of reactive oxygen species (catalase, glutathione reductase, peroxidase and superoxide dismutase (SOD)) were examined in the leaves of Phaseolus vulgaris L. var. Top Crop treated with plant hormones and infected with a non-lesion-forming isolate of white clover mosaic potexvirus (WClMV). The activities of catalase, glutathione reductase and SOD rapidly declined after infection while peroxidase activity was enhanced. These changes occurred before the rapid increase (5 days) in WClMV replication. A mild chlorosis appeared 7–10 days after inoculation but necrosis was never observed on inoculated leaves. Plants treated with dihydrozeatin, salicylic acid and jasmonic acid prior to WClMV inoculation showed elevated catalase, glutathione reductase, and peroxidase activity, while SOD activities remained the same as in water-treated controls. These treatments all inhibited virus replication with enzyme activities remaining near control levels. We propose that a decline in free radical scavenging capacity may be required before a rapid increase in virus replication can take place. Treatments increasing the ability of the plant to scavenge reactive oxygen species may hinder virus replication. A possible role for reactive oxygen species as a requirement for virus replication is discussed.     

THE RESPIRATION OF TOBACCO LEAVES IN THE 20-HOUR PERIOD FOLLOWING INOCULATION WITH TOBACCO MOSAIC VIRUS

The effect of infection with tobacco mosaic virus on the respiration rates of detached tobacco leaves in the period immediately after inoculation differed in plants grown at different times of the year. During winter, infection increased respiration rates, and in summer decreased them. In winter-grown plants, increasing the light intensity during the period before inoculation decreased respiration rates after infection. Extending the day length for winter-grown plants did not alter the effect of infection on respiration. Respiration rates began to change in less than 1 hr. after inoculation and are unlikely to be associated with the formation of new virus.     

Squirrel monkeys support replication of BK virus more efficiently than simian virus 40: an animal model for human BK virus infection

We performed experiments to test the suitability of squirrel monkeys (Saimiri sciureus) as an experimental model for BK virus (BKV) and simian virus 40 (SV40) infection. Four squirrel monkeys received intravenous inoculation with BKV Gardner strain, and six squirrel monkeys received intravenous inoculation with SV40 777 strain. Eight of 10 monkeys received immunosuppression therapy, namely, cyclophosphamide subcutaneously either before or both before and after viral inoculation. The presence of viral infection was assessed by quantitative real-time PCR amplification of viral DNA from blood, urine, and 10 tissues. We found that squirrel monkeys were susceptible to infection with BKV, with high viral copy number detected in blood and viral genome detected in all tissues examined. BKV genome was detected in urine from only one monkey, while three monkeys manifested focal interstitial nephritis. BKV T antigen was expressed in renal peritubular capillary endothelial cells. By contrast, SV40 was detected at very low copy numbers in only a few tissues and was not detected in blood. We conclude that the squirrel monkey is a suitable animal for studies of experimental BKV infection and may facilitate studies of viral entry, pathogenesis, and therapy.     

Nitrate induced regulation of nodule formation in soybean

Nodule formation was inhibited by exposing soybean plants to nitrate in plastic growth pouches. Exposure to 15 millimolar nitrate resulted in a 2.5-fold decrease in the number of nodules formed in the region of the primary root above the mark made at the time of inoculation to indicate the position of the root tip. Serial section analysis of Bradyrhizobium infections in this region revealed that infection initiation was inhibited approximately 3-fold by exposure to nitrate. Both initial cortical cell divisions and infection thread formation were inhibited. If exposure to nitrate was delayed for 18 hours after the time of inoculation, inhibition was much reduced. This indicates that most of the nitrate-sensitive events of infection were functionally complete within less than 18 hours. Exposure to nitrate for periods of 4 to 24 hours after inoculation, followed by transfer to no-nitrate conditions for the remainder of the time, did not result in substantial inhibition of nodule number. This indicates that the effects of nitrate on infection initiation can be almost entirely reversible. Split towel pouches were used to physically separate portions of the primary root exposed to nitrate and portions of the root exposed to rhizobia. In experiments where nitrate was applied either below or above the inoculated region of the primary root, the degree of inhibition of nodulation was not correlated with either the external concentration of nitrate in contact with root cells undergoing infection or with the internal concentration of nitrate in the infectible region of the root. These results indicate that nitrate itself may not directly inhibit infection initiation or induce host regulatory responses.     

Mechanism of differences in pathogenicity between two variants of a laboratory strain of herpes simplex virus type 1

The mechanisms responsible for the difference in neurovirulence to inbred mice between two variants of the Miyama strain of herpes simplex virus type 1 (HSV-1) were studied. After intraperitoneal (i.p.) inoculation, the +GC (LPV) variant reached the spinal cord and the brain, and caused death. Conversely, the -GCr variant lacked the ability to gain access to the central nervous system (CNS) after the same route of infection and failed to kill susceptible mice. The initial virus growth after i.p. inoculation, as indicated by the number of infective centers (ICs) produced by the peritoneal exudate cells (PECs), was compared between these two variants. The virulent +GC (LPV) strain induced much more ICs than the attenuated -GCr variant. When the attenuated variant was preinoculated i.p. 24 hr before the challenge inoculation with the virulent variant by the same route, the production of ICs by the pathogenic variant was highly inhibited, and growth of this variant did not occur in the CNS. Thus, mice were protected from lethal infection by the virulent variant by preinoculation with the attenuated one. Moreover, the ability of mice to resist i.p. infection by HSV-1 was shown to be age-dependent.     

Early histopathology of experimental infection with Leishmania donovani in hamsters

The extracellular promastigote stage of Leishmania donovani is inoculated by a phlebotomine sandfly into the skin of a susceptible host, after which visceral dissemination and clinical disease may ensue. Using a hamster model we examined the histopathology of early infection with L. donovani after intradermal inoculation of cultured promastigotes. The initial response was a mixed polymorphonuclear (PMN)-mononuclear phagocyte infiltrate, noted between 1 and 24 hr after inoculation, which became primarily mononuclear by 48 hr. Parasites were initially found intracellularly in both PMN's and mononuclear phagocytes, but by 48 hr they had assumed amastigote-like morphology and were found exclusively in macrophages. The number of parasites per infected macrophage increased during the first week after inoculation, suggesting that intracellular replication of the organism was taking place. This was followed by the formation of granulomas between 4 and 6 wk. By 8 wk intracellular parasites were largely gone. The histologic response was consistent with early destruction of parasites in PMN's, and survival and replication of L. donovani in macrophages. Cutaneous infection with the parasite was eventually controlled locally, coincident with granuloma formation. Despite these local responses, the organism was able to disseminate and eventually produce typical visceral leishmaniasis.     

Influence of κ/β-carrageenan from red alga <Emphasis Type="Italic">Tichocarpus crinitus</Emphasis> on development of local infection induced by tobacco mosaic virus in Xanthi-nc tobacco leaves

The influence of κ/β-carrageenan from red marine alga Tichocarpus crinitus on the development of tobacco mosaic virus (TMV) infection in Xanthi-nc tobacco leaves was studied. It was shown that the number of necrotic lesions on the leaves inoculated with the mixture of TMV (2 μg/ml) and carrageenan (1 mg/ml) was reduced by 87%, compared to the leaves inoculated with the virus only. The suppression of virus infection was also observed when leaves were treated with carrageenan 24 h before or 24 h after leaf inoculation with TMV; however, in these cases, suppression was less evident than after inoculation with the virus-polysaccharide mixture. It is supposed that the antiviral activity of carrageenan applied together with TMV may be explained by its action not only on the plant but also on the virus itself. The inhibitory effect of carrageenan pretreatment can be explained by its favorable effect on tissue resistance to infection. The suppression of this resistance by actinomycin D indicates that carrageenan functions via its action on the cell genome.     

Suppression of the parasitemia in rodent filariasis (Litomosoides carinii) by immunization with BCG and microfilaria. II. Intravenous BCG application

By intravenous (i.v.) inoculation of living tuberculosis bacteria (BCG) non-specific resistance to microfilariae of Litomosoides carinii (Filarioidea) is induced in cotton rats. This is only possible using the preparation "Immune-BCG Pasteur F" (suspended germs), but not with "Vaccin-BCG pour scarifications" (lyophilized tuberculosis bacteria). After inoculation of Immune-BCG, followed by a challenge infection by 60 infective larvae 6 weeks later, a patent infection develops. However, the level of microfilaraemia is constantly lower than in the control. After challenge infection 12 weeks later, this effect has disappeared. Immune-BCG has no influence on the worm load or the output of microfilariae by the adult worms. If i.v. inoculation of Immune-BCG is combined with a subcutaneous injection of specific antigen--living embryos from the uteri of adult worms--the BCG-activated immune system undergoes specific sensitization. Upon challenge infection 6 weeks later, the microfilaraemia is completely suppressed, but the worm load and production of microfilariae by the adult female worms are normal. If Immune-BCG is injected i.v. 3 days before intraperitoneal injection of freeze-killed microfilariae, there is still constantly reduced microfilaraemia when challenge infection follows 12 weeks later. Obviously, the effect of this relatively weak antigen may be increased by BCG stimulation.     

Modulation of hepatitis B infection by intravenous application of an immunoglobulin preparation that contains antibodies to hepatitis B e and core antigens but not to hepatitis B surface antigen.

Repeated administration of an intravenous immunoglobulin containing antibody to hepatitis B e antigen (anti-HBe) and antibody to hepatitis B core antigen (anti-HBc) but free of antibody to hepatitis B surface antigen (anti-HBs) before and after the inoculation of 10(4.9) 50% chimpanzee infective doses of hepatitis B virus (HBV) markedly prolonged the incubation period of HBV in experimentally infected chimpanzees. Similar administration of an immunoglobulin preparation containing anti-HBc but free of anti-HBe and anti-HBs or intramuscular administration of a single dose of immunoglobulin containing anti-HBe and anti-HBc 3 days before or after inoculation with HBV did not appear to modulate HBV infection. These observations suggested that anti-HBe, or an unidentified antibody associated with it, may have biological activity in the modulation of HBV replication.