VTechWorks Repository :: Browsing by Author "Moore, Laurence D."

Browsing by Author "Moore, Laurence D."

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Comparative studies on the modes of action of SC-0224 and glyphosate
Cooley, William Edward (Virginia Polytechnic Institute and State University, 1985)
The biological actions of the herbicides SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) and glyphosate [N-(phosphonomethyl)glycine] (PMG) were compared. In each study trimethylsulfonium iodide (TMS-I) was included as a treatment because the trimethylsulfonium ion is a constituent of the SC-0224 molecular structure. In inflated duckweed (Lemna gibba L.), both formulated and technical grade forms of SC-0224 were found to be much more phytotoxic to duckweed than either formulated or technical grade forms of glyphosate. The growth inhibition caused by glyphosate was partially prevented by different combinations of the aromatic amino acids phenylalanine, tyrosine, and tryptophan; whereas, the duckweed growth inhibition caused by SC-0224 could not be reduced by the same amino acid combinations. TMS-I and SC-0224 were found to be equally phytotoxic to duckweed. SC-0224 caused larger increases than glyphosate in the pool levels of amino acids; the increases caused by SC-0224 were similar, however, to those caused by trimethylsulfonium iodide. Expressed on a per gram fresh weight basis none of the chemical treatments caused significant changes in soluble protein or the incorporation of ¹⁴C-leucine into soluble protein. On a per flask basis (allowing for decreased growth in treated flasks), both herbicides and TMS-I caused significant decreases in soluble protein and ¹⁴C-leucine incorporation. SC-0224 and TMS-I caused larger decreases than glyphosate in both cases but the SC-0224 and TMS-I treatments were not significantly different. These data indicate that differences in the phytotoxicity of SC-0224 .and glyphosate may be due to the action of the trimethylsulfonium ion of the SC-0224 structure. The effects of these herbicides on the conversion of shikimate to anthranilate in a cell-free extract of Klebsiella pneumoniae ATCC 25306 were also compared. SC-0224 and glyphosate equally inhibited the production of anthranilate indicating that SC-0224 has action similar to glyphosate on the shikimate pathway. The effects of these herbicides on photosynthetic electron transport (the Hill reaction) was determined using isolated thylakoids from Alaska pea (Pisum sativum L.). The action of SC-0224 was compared with the action of glyphosate, TMS-I and diuron [3-(3,4-dichorophenyl)-1,1-dimethylurea]. SC-0224, glyphosate and TMS-I did not inhibit the Hill reaction at concentrations up to 10 mM; whereas, diuron caused an almost total inhibition at 0.10 mM. The results of this study indicate that SC-0224 is not an inhibitor of photosynthetic electron transport. These studies indicate that both constituents of the SC-0224 structure, TMS and PMG, are phytotoxic and may act independently.
Concurrent optimization in designing for logistics support
Hatch, Melanie L. (Virginia Tech, 1994-05-15)
The military community has considerable experience in the areas of procuring and managing large systems. These systems are often expected to perform their intended function over a period of several years and as a result, they will require an extensive support structure consisting of personnel, equipment and spare assets. For this reason, Logistics Management has always been an important field within the military and is gaining recognition within private industry as well. The evolutionary process which starts with the identification of a need and continues through design, production and retirement is known as a product's life cycle. Studies have shown that the decisions which are made initially, during the design of the product, will determine 80% of the total system costs. Several efforts have been initiated to improve the product design process and emphasize the life cycle approach. These include; Concurrent Engineering, Logistics Support Analysis (LSA) and Quality Function Deployment (QFD). These efforts necessitate an overhaul of the decision-making methods used in the product design process. Consequently, within the military community and private industry, the time-honored sequential-hierarchical-decision approach to design is being replaced with concurrent decision-making. The sequential process of the hierarchical method can lead to suboptimal designs which significantly increase manufacturing and follow-on support costs.
Effect of benomyl, Topsin-M, and Botran against Monilinia fructicola and Rhizopus nigricans on peach and nectarine fruits and in vitro
Brown, Herbert Irving (Virginia Tech, 1975-05-09)
Monilinia fructicola (Wint.) Honey, and Rhizopus nigricans Erh., the causal organisms of brown rot and Rhizopus rot, respectively, have long been recognized as the two major causes of post-harvest rots on peach and nectarine fruits. Fruit losses of as much as 50% may occur during storage, transport, and marketing from these two diseases if effective fungicide treatments are not used. Application of fungicide suspensions as post-harvest dips have been reported to reduce losses from post-harvest rots considerably, however, more effective treatments are needed. Tests were made of three fungicides: benomyl [methyl-l-(butylcarbamoyl)-2-benzimidazole carbamate], Topsin-M [dimethyl-4,4'-ophenelenebis (3-thioallophanate) , and Botran (2,6-dichloro-4-nitroanaline) against the two post-harvest rot fungi, M. fructicola and R. nigricans, on peach and nectarine fruits and in vitro. Fruits were inoculated with an equal concentration of spores of both fungi, then treated, by dipping in the different fungicide suspensions at 0, 4, 8, and 12 hour intervals after inoculation. Three concentrations of benomyl or Topsin-M (300, 450, and 600 ~g/ml) were used in combination with corresponding concentrations of Botran (600" 900, and 1200 Ug/ml). Number of decayed fruits increased with time of treatment after inoculation up to 8 hours then leveled off. Lesion progression, however, was slower with all fungicide treatments as compared to those of the untreated check fruit. Percent of decayed fruit remained lower when treatments were applied within 4 hours after inoculation. Later application times were ineffective and fruits showed approximately the same level of infection as controls. Treated nectarines appeared to be more susceptible to the post harvest rots than peaches. This may be due to lower residues of the chemicals remaining on the smooth skinned fruit. Benomyl and Topsin-M were fungitoxic to M. fructicola in vitro but neither was effective against R. nigricans. Botran alone was fungistatic to both R. nigricans and M. fructicola, but often lost effectiveness after 96 hours. Combinations of benomyl plus Botran, or Topsin-M plus Botran, were fungitoxic to M. fructicola and fungistatic to R. nigricans. Botran alone and Botran in combination with benomyl or Topsin-M inhibited germination of M. fructicola and R. nigricans spores more effectively than benomyl or Topsin-M alone. There were no major significant differences in control provided by treatments containing benomyl or Topsin-M. Treatments using Botran with benomyl or Topsin-M did not effectively control post harvest rot when applied later than 4 hours after inoculation. In vitro tests, however, indicated either a synergistic or additive effect of the fungicide combinations against R. nigricans.
The Effect of Glycogen Depletion on Sarcoplasmic Reticulum Function
Batts, Timothy Wayne (Virginia Tech, 1997-12-04)
The role of glycogen in endurance performance has been accepted in theory. It has been shown that higher resting muscle glycogen levels prolong endurance performance. On the other hand, low glycogen levels have been associated with fatigue. Ultimately, a person's muscle glycogen level dictates the duration in which an activity can be maintained at a maximal effort, after which time, performance will decrease. As of yet, there has been no evidence as to what happens to the fatigued muscle. Force production in skeletal muscle is dictated by the release and uptake of Ca²⁺ from the sarcoplasmic reticulum (SR). Force production is proportional to [Ca²⁺], as [Ca²⁺] increases so does force. At the point of fatigue, there is a decrease in force production. Since fatigue has been associated with glycogen depletion, it is likely that SR function has been altered causing this decrease in force. The purpose of this study was to determine the effect of glycogen depletion on the SR. Twenty male Sprague-Dawley (Harlan Sprague-Dawley, Indianapolis, IN) rats weighing, 345 ± 70 gm were housed two per cage in the Virginia Tech Lab Animal Resources facility. They were fed ad libitum (Purina Rodent Laboratory Chow and water) until time of experiment. Ten of the rats were used as control animals and the other ten were assigned to the experimental group. Rats were allowed a minimum of 5 days to acclimate to their housing. On the morning of the day of testing, rats were selected in pairs according to the housing cage in an effort to decrease variations in food consumption. To reduce muscle glycogen levels, experimental rats were given an initial injection of either epinephrine (1mg/g: ip) while control rats were injected with saline (equal volume) at 0 hr. Thirty minutes later they received another injection of epinephrine or saline (0.5 mg/g: ip). At the end of the hour the rats were anesthetized with pentobarbital sodium (60 mg/kg:ip) for tissue harvesting. Upon reaching a surgical plane of anesthesia one gastrocnemious muscle was extracted for the muscle glycogen assay and the other removed for SR vesicle preparation. Rats were then euthanized with an overdose of pentobarbital sodium. The tissue was assayed for glycogen and glucose levels as well as for Ca²⁺ uptake and release and ATPase activity. It was found that epinephrine animals had 23% less glycogen than did the control animals and almost twice the amount of glucose (control — 2.9 nmol/g and epinephrine — 5.9 nmol/g). Ca²⁺ uptake rates in epinephrine animals were significantly decreased by 19.7% (p < .05). Control animals had a release rate of 77.15 ± 1.26 nmol/mg/min and epinephrine animals had a release rate of 75.01 ± 1.86 nmol/mg/min. Ca²⁺ release rates were decreased but not significantly. Ca²⁺ stimulated ATPase activity was significantly decreased by 17.7% in epinephrine animals (p < .05). This is one of the first studies that demonstrate that glycogen reduction in a rested muscle causes altered SR function similar to those caused by exercise. This study shows that low glycogen levels are associated with decreased SR function, which is the primary reason for causing the loss of force in muscle. Ultimately, this study suggests that glycogen loading will enhance endurance performance.
Effects of Reduced Muscle Glycogen on Sarcoplasmic Reticulum (SR), Muscle and Exercise Performance
Batts, Timothy W. (Virginia Tech, 2002-04-19)
Fatigue during exercise is associated with reduced muscle glycogen. However, evidence linking glycogen content to fatigue is lacking. In this study we examined whether reduced muscle glycogen content limited SR function or muscle performance. Two groups of female Sprague-Dawley rats were fasted for 24 hr and exercised for 90 min to reduce muscle glycogen; rats fasted after exercise formed the low glycogen (LG) group. Rats in the high glycogen (HG) group were allowed free access to food and a 5% sucrose solution. The LG group had 42% less muscle glycogen and 90% less glycogen associated with the sarcoplasmic reticulum (SR) than the HG group. Notably, time to exhaustion during a subsequent treadmill run (21 m/min at 10% grade) was markedly lower in the LG group (35 vs. 166.75 min). Despite less glycogen, the LG group had a higher SR Ca2+ uptake rate (45%) and Ca2+-stimulated ATPase activity (51%) possibly due to a 33% greater SERCA content. Surprisingly, in situ gastrocnemius initial twitch and tetanic forces were not different between groups although the rates of relaxation were higher in the LG group. The force responses to fatigue-inducing stimulus trains (20 Hz for 333 ms every 1 sec for 30 min) also were similar for both groups as were twitch and tetanic forces in the fatigued state. These results suggest that despite reduction in exercise performance, reduced muscle glycogen does not limit muscle performance or SR function.
Effects of simulated acidic precipitation on the colonization and ice nucleation activity of Pseudomonas syringae pv. syringae and Erwinia herbicola
Murray, Joseph Marshall (Virginia Tech, 1987-03-02)
Precipitation over the eastern United States has been increasing in acidity, particularly within the last three decades. The average annual pH of rain in this area is about 4.2. The foliar surface, or phylloplane, of soybean can be damaged by rain acidified to pH 2.9. Simulated acidic precipitation has an overall inhibitory influence on soil microbial processes. The effect acidic precipitation may have on epiphytic microorganisms has not been examined. Bacteria are among the most numerous residents on the phylloplane.
Effects of stratification on in vitro protein synthesis using components from embryos of Pinus lambertiana Dougl.
Dury, Carl George (Virginia Tech, 1975-01-15)
An vitro protein synthesizing system using Sephadex G-25 gel filtration for supernatant purification was used to determine the ability of extracts from embryos of dormant and stratified sugar pine seeds to promote protein synthesis. It was found that the ribosomes from the embryos of dormant seeds were more active than those from stratified seeds but they also required a greater quantity of supernatant protein to produce this activity. The supernatant fraction from stratified embryos was more active than that from dormant embryos but there were indications that this increase was due to seed imbibition. Concentrations of other essential components of the system were the same for both dormant and stratified embryo systems. In each 0.5 m1 sample, maximum incorporation occurred using 0.03-0.06 mg ribosomal protein, 0.795 μmo1es ATP, 1.8 μmo1es PEP, 13.2 μgms pyruvate kinase, 0.090 μmoles GTP, and 0.0375 mg polyuridylic acid. Optimum incubation conditions were at 37°C for 60 minutes. Ribonuclease and protease inhibited phenylalanine incorporation. Ribonuclease activity in the supernatant fraction increased with purification and was significantly higher in the dormant embryos than in the stratified. Protease activity decreased with purification of the supernatant and there was no significant difference between activity in the dormant and stratified embryo supernatant fractions. Protease activity was high in the ribosomal fraction. Ribosomes from dormant embryos appeared to bind more polyuridylic acid than did those from stratified embryos. Resedimented ribosomes consisted primarily of monoribosomes but some polyribosomes were present in both dormant and stratified embryos. Analysis of incubation mixtures produced similar results. The majority of the labelled polyphenylalanine was associated with the monoribosomes.
Identifying Sources of Fecal Pollution in Water as Function of Sampling Frequency Under Low and High Stream Flow Conditions
Graves, Alexandria Kristen (Virginia Tech, 2003-04-15)
Sources of fecal pollution were evaluated as a function of sampling frequency with stream samples from Mill Creek, Montgomery County, VA. Samples were collected monthly for one year, plus weekly for four consecutive weeks during seasonal high flows (March), and seasonal low flows (September-October), plus daily for seven consecutive days within the weekly schedules. Thirty stream samples were collected from each of two sites (60 total) in Mill Creek, and 48 isolates of E. coli per sample (total of 2,880 stream isolates) were classified by source using antibiotic resistance analysis (ARA) and comparing the resulting patterns against a known-source E. coli library (1,158 isolates). The same process was performed with enterococci isolates against an enterococci library (1,182 isolates). The average rate of correct classification (ARCC) for the E. coli library with a three-way split (human, livestock, and wildlife) was 89.0%, and the ARCC of the species-specific E. coli library (cattle, deer, goose, human, misc. wildlife) was 88.9%. The ARCC of the enterococci library with a three-way split was 85.3%, and the ARCC of the species-specific enterococci library was 88.1%. The results did not justify the need for daily or weekly sampling, but indicated that monthly was adequate (quarterly and every-other-month were not). There was a seasonal effect as the human signature was highest during high flow while the livestock signature dominated during low flow. The results also indicated that sampling should be done over a period of time that includes both seasonal wettest and driest periods (at least 8 months).
Interactions of paraquat and nitrodiphenylether herbicides with the chloroplast photosynthetic electron transport in the activation of toxic oxygen species
Upham, Brad Luther (Virginia Polytechnic Institute and State University, 1986)
The interactions of paraquat (methylviologen) and diphenylether herbicides with the Mehler reaction as investigated. Sera from two different rabbits (RS1 & RS2) were examined for their patterns of inhibition of the photosynthetic electron transport (PET) system. Serum from RS2 was greatly hemolyzed. Fifty ul of RS1 serum were required for 100% inhibition of a H₂O → methylviologen(MV)/O₂ reaction, whereas only 10 µl of a 1:10 dilution of RS2 were needed for 100% inhibition. The γ-globulin fraction from purified rabbit serum (RS1) did not inhibit PET, indicating that the antibody fraction of the rabbit serum does not contain the inhibitor. It appears that the inhibitor is from the hemolyzed red blood cells. Rabbit sera, added to chloroplast preparations prior illumination, caused no inhibition of a H₂O → MV/O₂ reaction while addition of rabbit sera during illumination inhibited the H₂O → MV/O₂ reaction within 1-3 s. Various Hill reactions were used to determine the site of inhibition. Rabbit sera inhibited photosystem I (PSI) Hill reactions, but did not inhibit a photosystem II (PSI II) Hill reaction indicating that inhibition is on the reducing side of PSI. It would be expected that a H₂O → Ferredoxin (Fd)/NADP Hill reaction should also be blocked. Surprisingly, rabbit sera did not inhibit this reaction. These results were interpreted as supportive evidence for parallel (branched) electron transport on the reducing side of PSI. Six pyridyl derivatives {benzylviologen, 2-anilinopyridine, 1,2-bis(4-pyridyl)ethane, 1,2-bis(4-pyridyl)ethylene, 2-benzoylpyridine, and 2-benzylaminopyridine} and five heme-iron derivatives {hemoglobin, hemin, hematin, ferritin, and ferrocene} were screened for their potential to counteract paraquat toxicity on pea (Pisum sativum L. cv. Little Marvel) isolated chloroplasts. H₂O → MV/O₂ and H₂O → Fd/NADP+ were the two Hill reactions assayed with these compounds. Antagonists of paraquat toxicity should inhibit the first Hill reaction but not the latter. None of the pyridyl derivatives examined inhibited the reaction H₂O → MV/O₂. Ferritin and ferrocene were also ineffective as inhibitors of this reaction. Hemoglobin inhibited the reaction H₂O → MV/O₂ without inhibiting the reaction H₂O → Fd/NADP+, providing protection to pea chloroplasts against paraquat. Hemin and hematin inhibited both Hill reactions examined. Hemin and hematin also inhibited H₂O → diaminodurene (ox) and durohydroquinone → MV/O₂ Hill reactions but not the dichlorophenylindolphenol(red) → MV/O₂ and diaminodurene(red) → MV/O₂ Hill reactions. These results indicate that hemin and hematin are inhibiting photosynthetic electron transport in the plastoquinone pool region. Potential involvement of hydroxyl and alkoxyl radicals in the peroxidative action of the p-nitro diphenyl ether herbicides acifluorfen was evaluated under laboratory conditions. Methional was added to illuminated pea thylakoids and its oxidation to ethylene was used as an indicator of hydroxyl and alkoxyl radical synthesis. Oxyfluorfenstimulation of the rate of methional oxidation was dependent on light, photosynthetic electron transport and hydrogen peroxide since it was not observed under dark conditions or in the presence of DCMU and catalase. Addition of FeEDTA, a catalyst of the Fenton reaction, stimulated the oxyfluorfen-induced enhancement of methional oxidation six-fold suggesting that hydroxyl radicals are synthesized through a Fenton reaction. Acifluorfen, nitrofen and nitrofluorfen inhibited the rate of methional oxidation whereas, acifluorfen-methyl had no effect on the rate of methional oxidation even at high concentrations (1 mM). Nitrofluorfen at 1 mM was the only p-nitro diphenyl ether herbicide tested which inhibited photosynthetic electron transport of pea thylakoids. In experiments with pea leaf discs, acifluorfen at low concentrations stimulated the rate of methional oxidation, while acifluorfen-methyl, nitrofen and nitrofluorfen had no effect. These data indicate that hydroxyl and alkoxyl radicals could be involved in the mechanism of cellular damage caused by oxyfluorfen, but they are not important for the activity of the diphenyl ether herbicides acifluorfen, acifluorfen-methyl, nitrofen, and nitrofluorfen. Diethyldithiocarbamate (DEDTC) does not accept electrons from the photosynthetic electron transport (PET), but can donate electrons to a photosystem I (PSI) Mehler reaction in the presence of the following PET inhibitors: diuron, dibromothymoquinone, and bathophenanthroline. It cannot photoreduce PSI in the presence of cyanide, a PET inhibitor. These data indicate that the site of electron donation is after the plastoquinone pool. Ascorbate is not required for the ability of DEDTC to donate electrons to PSI. There is no photoreductant activity by DEDTC in a ferredoxin/NADP Hill reaction. Superoxide dismutase inhibits DEDTC/diuron or bathophenanthroline → MV/O₂ Mehler reaction. Catalase does not restore the consumed O₂ from a DEDTC/diuron → MV/O₂ Mehler reaction, indicating O₂- has not been dissmutating into H₂O₂. These results indicate that superoxide is required for DEDTC ability to donate electrons, therefore DEDTC is limited only to Mehler-type reactions.
Manganese in Virginia soils and correction of manganese deficiency in soybeans (Glycine max L.)
Alley, Marcus M. (Virginia Tech, 1975-03-07)
The research was undertaken to provide basic information on Mn in Virginia soils and to evaluate rates and methods of Mn application to correct Mn deficiency in soybeans. Soil profile samples were analyzed from catenas representing the Appalachian, Piedmont, and Coastal Plain regions. The exchangeable, easily reducible, and total Mn contents were higher in the Appalachian soils than in the Piedmont or Coastal Plain soils. The total Mn content of the well-drained soil was higher than the poorly-drained soil in the Appalachian catena. No other differences were found between soils varying in drainage. Parent material and time appear to be the soil forming factors that exert the largest influence on total soil Mn. Further research is necessary to fully characterize soil Mn in these broad physiographic regions.
Net photosynthesis and photosynthate partitioning/of day-neutral and Junebearing strawberry plants as influenced by fruiting
Schaffer, Bruce (Virginia Polytechnic Institute and State University, 1985)
Net photosynthesis (Pn) and photosynthate partitioning were compared between fruiting and deblossomed strawberry plants. Throughout a six-week fruiting cycle, Pn (leaf area basis), specific leaf weight (SLW), and chlorophyll content were determined at 7-day intervals for an early-formed leaf (old leaf) and for the most recently expanded leaf (young leaf) of fruiting and deblossomed day-neutral plants (cv. Tribute). During the fifth week of the fruiting cycle, Pn of the young leaf was higher for fruiting plants than for deblossomed plants. Pn of the old leaf was not different between treatments during any week. During weeks 4 and 5, the young leaf of the deblossomed plants had a higher SLW than that of fruiting plants; SLW of the old leaf was higher for deblossomed plants during weeks 4-6. The young leaf of the deblossomed plants had a higher chlorophyll content than that of fruiting plants during weeks 1 and 4. Chlorophyll content of the old leaf was higher for deblossomed plants during weeks 1, 2, and 4. There were no differences between treatments for stomatal conductance for CO₂ or dark respiration during any week of the fruiting cycle. In another experiment, deblossoming day-neutral strawberry plants (cv. Tribute) increased the amount of ¹⁴C translocated to the newly-emerging leaves 48 hrs after treatment with ¹⁴CO₂. During weeks 3-6 of the fruiting cycle, leaves of deblossomed plants had a greater total area, dry weight, and total non-structural carbohydrate (TNSC) content than leaves of fruiting plants. Pn on a whole-plant basis was higher for deblossomed plants than fruiting plants. This was largely due to the greater leaf area of the deblossomed plants, since total leaf area was highly correlated with Pn (whole plant basis). Pn (whole plant basis) was highly correlated with total dry weight and TNSC of plants in both treatments. Thus, deblossoming changed Pn and dry matter partitioning of strawberry plants. The additional leaf area and greater Pn rates (whole plant basis) obtained by deblossoming strawberry plants may result in increased yields during subsequent fruiting cycles.
Procerum root disease physiology and disease interactions with ozone
Carlson, Jodi A. (Virginia Tech, 1994-02-17)
Procerum root disease of eastern white pine (Pinus strobus L.), caused by Leptographium procerum (Kendr.) Wingf., has been epidemic in Virginia Christmas tree plantations since 1990. Symptoms of chlorosis, wilt, and decreased apical growth resemble those of water stress. Resin infiltration of the xylem at the stem base may be responsible for vascular occlusion leading to severe water deficits and mortality. The pathogen has been isolated from the roots of ozone-sensitive eastern white pines in the field, although not from nearby tolerant trees, and it may be that ozone sensitivity predisposes the trees to infection. The objectives of my Studies were to investigate the physiology of diseased white pines, and to determine the effects of ozone fumigation on disease development. Impacts of vascular occlusion upon host water relations and gas exchange were investigated in 8-yr-old, plantation-grown, white pine Christmas trees. Disease severity was estimated as the proportion of resin-soaked cross-sectional area at the base of the stem. The linear response of a suite of six physiological variables to disease severity was highly significant. Individually, the variables pre-dawn water potential, daily change in pre-dawn to mid-day water potential, stomatal conductance, and photosynthetic and transpiration rates all decreased significantly with increasing disease severity. Fumigation studies were conducted on white and loblolly (P. taeda L.) pine seedlings to determine if ozone exposure increased the incidence of root disease or the amount of stem tissue colonized by L. procerum. Roots were inoculated by soil drenching with conidial suspension, and stems were wounded at the base and inoculated with mycelium. Beginning 24 h post-inoculation, and for 14 consecutive days, seedlings were fumigated in closed chambers with charcoal-filtered air or 200 ppb ozone for 5 h/day, then removed to a charcoal-filtered greenhouse. Six weeks post-inoculation, root and stem tissue were plated on a medium selective for L. procerum. Ozone treatment did not significantly affect the proportion of diseased roots per seedling or the vertical colonization of stem tissue in seedlings of either species.
Response of Leaf Protein to Ozone in Two White Clover Clones
Youlin, Tang M.S. (Virginia Tech, 1998-05-07)
A white clover ( Trifolium repens ) system, based on one ozone-sensitive (NC-S) and one ozone-resistant (NC-R) clone, has been developed as an indicator to estimate the effects of tropospheric ozone on plant biomass production. A reduction in the vegetative biomass ratio (NC-S/NC-R) of the clones was correlated with increasing concentrations of ozone during a 28-day exposure period. However, the mechanism of ozone sensitivity or tolerance at the biochemical or molecular level is not known. Superoxide dismutase isozyme activities in the two clones did not respond differently to ozone treatment. However, catalase activity increased somewhat more in the leaf tissue of NC-R, compared to NC-S, after ozone treatment. Two-dimensional polyacrylamide gel electrophoresis (PAGE) showed the presence of two proteins (Ozone-Response-Proteins, ORPs) that were more responsive to ozone in the tolerant genotype than in the sensitive one. After ozone treatment for three days, the ORPs were four-fold higher in leaf tissue of NC-R compared to NC-S. Also, the amount of the ORPs was twenty-fold higher in leaf tissue of ozone-treated NC-R than in that of control NC-R. These proteins have apparent molecular weights of 21.5 kD and 23 kD and isoelectric points of 4.1-4.4 on SDS-PAGE gels. The filtrate of a 100 kD concentrator showed that the native molecular weights of the ORPs were less than 100 kD. The results obtained from a study of field samples demonstrated that protein content in leaf tissue of both NC-R and NC-S was positively correlated with ORP content.
Roles of tannase and hydrolyzable tannins in chestnut blight
Farias, Graciela Maria (Virginia Tech, 1992-03-15)
Endothia parasitica (Murr.) P. J. & H. E. Anderson (syn: Cryphonectria parasitica(Murr.) Barr), the causal agent of chestnut blight, was able to grow in total aqueous and tannin extracts from blight-susceptible American chestnut as well as in blight-resistant Chinese chestnut bark extracts, from winter and summer bark. Differences in the amount of conidial germination and growth in extracts of the two species were small. The, E. parasitica tannase was more abundant intracellularly than extracellularly. Total tannase activities from cultures in American chestnut aqueous and tannin extracts were greater than in the Chinese chestnut extracts, for both winter and summer bark. The tannase was isolated from the mycelium of E. parasitica and purified 142-fold with a 10% yield by anion exchange chromatography and gel filtration. The estimated molecular weight was 240 kD and the molecule may be a tetramer composed of four subunits with a molecular weight of 58 kD. The pH optimum of the purified tannase was 5.5 and the temperature optimum for activity was 30 C. The enzyme was separated into six bands in the pH range of 4.6 to 5.1 which may represent isoenzymes or post-translational modifications.
Sensitivity and resistance of Sclerotinia minor to fungicides for control of Sclerotinia blight of peanut
Brenneman, Timothy Branner (Virginia Polytechnic Institute and State University, 1986)
Sclerotinia blight, caused by Sclerotinia minor, is a severe disease of peanut in Virginia. Vinclozolin (V), iprodione (I), dicloran (D), and pentachloronitrobenzene (PCNB) were evaluated for their fungitoxicity to S. minor. The mean ED₅₈ values for five isolates were found to be 0.07, 0.11, 0.91, and 1.27 μg/ml, for V, I, D, and PCNB, respectively, on fungicide-amended glucose yeast-extract agar (GYEA). Fungicide-resistant growth sectors developed on media amended with I or V. Nine such strains occurred; they were capable of growth on GYEA amended with up to 1000 μg/ml of I or V, and were cross-resistant to D or PCNB. Resistance was maintained in all but two strains after repeated culture in the absence of fungicide for 3 yr. In field microplots, two resistant strains were pathogenic to peanut and survived as well as a fungicide-sensitive field isolate. D, I and V were applied to peanuts in the microplots for 3 yr at total annual rates of 8.41, 3.36, and 2.52 kg/ha, respectively. Disease severity caused by the resistant strains was suppressed 19, 33, and 87% by D, I, and V, respectively, as compared to 15, 24, and 76% for the sensitive isolate. Isolates recovered from tissue biopsies still grew on fungicide-amended GYEA indicating that in vitro and in vivo resistance are not equivalent in this case. Fungicide treatments reduced sclerotial populations of all strains, and reduced the viability of sclerotia from sensitive but not resistant strains. Fungicide-resistant strains were capable of surviving and competing pathogenically in microplots infested with equal numbers of sclerotia from a sensitive and a resistant strain; this trend was enhanced by fungicide applications. A survey of 763 isolates from fields treated with these fungicides failed to detect resistant strains. One fungicide-resistant isolate was recovered from an iprodione-treated microplot originally infested with a sensitive field isolate. A technique utilizing excised peanut stems was devised to evaluate isolate pathogenicity, cultivar resistance to the disease, susceptibility of different age peanut tissues, and fungicide persistence on peanut stems in the field. The method was also used to screen fungicides; results verified previous findings which indicated that in vitro resistance is not equivalent to in vivo resistance. Resistance to these fungicides may eventually become a field problem, but with correct management they should provide years of disease control.
The Southern pine beetle, Dendroctonus frontalis Zimm., and associated Coleoptera attracted to dead loblolly pine, Pinus taeda L.
Egan, Peter Joseph John (Virginia Tech, 1978-06-05)
This study tests the hypothesis: Bark beetles initially locate their host trees in a non-random manner. The association of the southern pine beetle (Dendroctonus frontalis Zimm.) and associated Coleoptera with stressed trees suggested the direction for this study. Loblolly pine trees, Pinus taeda L., were stressed by severing and girdling. The bark beetle population trapped at stressed trees was then compared to the bark beetles trapped at unstressed control trees. The experiments were conducted in an apparently normal, old-field mixed pine-hardwood forest located in Nottoway County, Virginia, during 1975 through 1977. The girdling technique consisted of three circumferential chain saw cuts 5 cm deep at approximately 1 m above the ground. The severing technique was accomplished by guying the trees with 3.2 mm wire rope to maintain the trees' normal vertical position. The bole was then severed with a chain saw. The control trees were not treated in any manner. The insects associated with the treated and control trees were trapped with a four-way glass baffle placed over an aluminum funnel attached to a 1 liter jar containing 2.5 cm of water. The traps were placed at mid-bole and collected weekly during the growing season. The bark beetle complex studied in this experiment consisted of the following species: Dendroctonus frontalis Zimm, D. terebrans Oliv., Ips avulsus Eichh., I. grandicollis Eichh., I. calligraphus Germ., Hylastes spp., Cossonus spp., and Pityophthorus spp. The bark beetles were not trapped at the treated trees until the trees' foliage had begun to fade. The time period varied from two weeks to two years and also with the month of treatment. The number of bark beetles trapped at trees with faded needles was 40.06/trap-week for the first week the bark beetles were trapped at the tree. Control trees trapped the same number of bark beetles per trap-week as treated trees with green needles, .06 bark beetles per trap-week. The southern pine beetle and associated Coleoptera during endemic population levels exhibit a non-random directed attraction to the treated trees after they died, as evidenced by the fading of the trees' foliage. The conclusion is reached that these insects have the ecological role of scavengers in pine forests.

Browsing by Author "Moore, Laurence D."

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