Showing papers in "Physiologial Plant Pathology in 1972"
TL;DR: A sensitive colour reaction is described for estimating fungi which contain chitin, the glucosamine residues of which are susceptible to deamination with nitrous acid, which yields an aldehyde which is determined colorimetrically with 3-methyl-2-benzothiazolone hydrazone.
Abstract: A sensitive colour reaction is described for estimating fungi which contain chitin. The method is based on the alkaline deacetylation of chitin to chitosan, the glucosamine residues of which are susceptible to deamination with nitrous acid. This yields an aldehyde which is determined colorimetrically with 3-methyl-2-benzothiazolone hydrazone. The observed level of aldehyde, expressed as glucosamine, was related to fungal dry weight by experiments using different fungi grown in vitro. The method, requiring 5 h to complete, has been tested on five phytopathogenic fungi and three hosts, and should be applicable to a wide range of host-pathogen systems.
345 citations
339 citations
TL;DR: A group of proteins isolated from the cell walls of tomato stems, bean hypocotyls and suspension-cultured sycamore cells has been shown to inhibit the action of the Fusarium oxysporum polygalacturonase and, in doing so, to prevent cell wall degradation by the mixture of fungal enzymes present in dialyzed culture filtrates.
Abstract: When grown in liquid culture containing 1% isolated cell walls from tomato (Lycopersicon esculentum) stems as the sole carbon source, Fusarium oxysporum secretes a variety of polysaccharide-degrading enzymes. These include a polygalacturonase, a cellulase, α- and β-galactosidases, an α- l -arabinofuranosidase, and a β-xylosidase. These enzyme activities appear in the culture fluid in a definite order: the polygalacturonase in first to reach maximal activity, followed by the glycosidases, with the cellulase reaching a peak after the other enzyme activities have diminished. A small fraction of the tomato stem cell wall, which contains a polysaccharide rich in galacturonic acid, has been shown to be a better inducer of the Fusarium oxysporum polygalacturonase than walls from which the inducer has been extracted. The ability of the Fusarium oxysporum culture filtrate enzymes to degrade cell walls isolated from tomato stems has also been demonstrated. Approximately 80% of the galacturonic acid present in tomato stem cell walls is removed in 6 h of enzymolysis with dialyzed Fusarium oxysporum culture filtrates. A group of proteins, isolated from the cell walls of tomato stems, bean hypocotyls and suspension-cultured sycamore (Acer pseudoplatanus) cells, has been shown to inhibit the action of the Fusarium oxysporum polygalacturonase and, in doing so, to prevent cell wall degradation by the mixture of fungal enzymes present in dialyzed culture filtrates.
181 citations
TL;DR: Agrobacterium tumefaciens strains 1D135 and B6 were characterized and crown-gall tumor-inducing activity was not found in preparations of 70 s ribosomes, and messenger, ribosomal or transfer RNA, almost all preparations of the bacterial chromosome lacked tumor inducing activity.
Abstract: Agrobacterium tumefaciens strains 1D135 and B6 were characterized. Both strains formed circular, smooth, creamy, shiny colonies on rich medium. In the scanning electron microscope their morphologies were bacilliform rods which possessed 1 to 6 peritrichous flagella. The optimum growth temperature was 31·8±0·5 °C for strain 1D135 and 32·1±0·5 °C for strain B6. Generation times at 32 °C were 62 and 61 min for strains 1D135 and B6 respectively. Both strains possessed activities of d -glucoside-3-dehydrogenase, catalase, oxidase, urease, nitrate reductase and β-galactosidase. Both strains produced acid on basal medium with arabinose, cellobiose, fructose, galactose, lactose or salicin. The 70s ribosomal proteins of these two strains were identical in electrophoretic mobilities in 7·5% acrylamide-urea gels at pH 4·3. Crown-gall tumor-inducing activity was not found in preparations of 70 s ribosomes, and messenger, ribosomal or transfer RNA. Nor was tumor-initiating activity in the case of strain 1D135 associated with circular satellite DNA molecules. Furthermore, almost all preparations of the bacterial chromosome lacked tumor inducing activity. A few preparations of high molecular weight DNA induced crown-gall-like tumors. The implications of this finding are discussed.
111 citations
TL;DR: Changes in cell structure were restricted to cells close to the nematode, but the products of cell breakdown moved away from this region through intercellular spaces, and giant cell production was generally suppressed by the hypersensitive reaction.
Abstract: The hypersensitive reaction in roots of Lycopersion esculentum L., cv. Nematex, infected by Meloidogyne incognita was studied by light and electron microscopy. An increase in cytoplasmic density characterized by increased numbers of ribosomes, proliferation of endoplasmic reticulum and increased stainability of the cytoplasmic ground substance was the first symptom of the resistance response to the nematode larvae. Concomitant with this change was a disappearance of dense osmiophilic inclusions from the vacuoles of hypersensitive cells. There followed a general loss in distinctness of the cell membranes resulting in the disappearance of mitochondria and Golgi bodies. The fibrillar structure of the nucleoplasm disappeared and numerous electron-dense inclusions appeared in the nucleoplasm. Organized arrays of ribosomes appeared on the outer membrane of the nuclear envelope. The plastid stroma lost its granular texture although large starch grains persisted. Changes in cell structure were restricted to cells close to the nematode, but the products of cell breakdown moved away from this region through intercellular spaces. Giant cell production was generally suppressed by the hypersensitive reaction. Heat-treatment of Nematex roots inhibited the hypersensitive reaction and thus enabled giant cell formation. Treatment of roots with the growth substance kinetin did not inhibit the hypersensitive reaction although it appeared to enhance giant cell formation.
108 citations
TL;DR: Quantitative studies using a newly developed cell grading system showed that infections of resistant varieties were normally restricted to single cells which became necrotic soon after penetration, and two types of cellular response were distinguished.
Abstract: Races of Colletotrichum lindemuthianum formed appressoria on bean hypocotyls and penetrated epidermal cells regardless of the resistance or susceptibility of the cultivars used. Quantitative studies using a newly developed cell grading system showed that infections of resistant varieties were normally restricted to single cells which became necrotic soon after penetration. Two types of cellular response were distinguished; the type found depended on the fungal race used. In one incompatible combination studied in detail, hyphal growth slowed soon after penetrated cells became necrotic but continued for several days. Susceptible tissue remained visibly unaffected for 3 or more days while considerable fungal colonization took place. Necrosis then occurred and macroscopic brown lesions appeared. A dense deposit, “reaction material”, formed at the site of penetration in some cells of both resistant and susceptible tissue; hyphae developed no further. The results are discussed in relation to different hypotheses concerning processes of resistance.
67 citations
TL;DR: The pectic enzyme complex produced by S. rolfsii would appear to function in tissue maceration, as well as provide a means of converting the pecting polymers of the host plant to a utilizable substrate for pathogen growth during pathogenesis.
Abstract: Sclerotium rolfsii (isolate 14) was shown to produce at least two polygalacturonases. Both of these enzymes exhibited maximal activity on polygalacturonic acid substrates near pH 4·0 and had isoelectric points near pH 5·2. The two enzyme fractions were resolved by gel-filtration in Sephadex G-75 and sucrose density gradient centrifugation. The larger enzyme component had an estimated molecular weight of 46, 000 to 48, 000 and exhibited exopolygalacturonase activity. The smaller enzyme fraction had an estimated molecular weight of 28, 000 to 31, 000 and exhibited both endopolygalacturonase and exopolygalacturonase activities. Polygalacturonic acid substrates were readily converted to oligogalacturonides by endopolygalacturonase action and the oligomers were converted to galacturonic acid by exopolygalacturonase. The pectic enzyme complex produced by S. rolfsii would appear to function in tissue maceration, as well as provide a means of converting the pectic polymers of the host plant to a utilizable substrate for pathogen growth during pathogenesis.
66 citations
TL;DR: The phytoalexins rishitin and phytuberin are produced in potato tubers var.
Abstract: The phytoalexins rishitin and phytuberin are produced in potato tubers var. King Edward inoculated with Erwinia carotovora var. atroseptica and incubated in aerobic conditions at 11 °C. Concentrations of up to 1215 μg rishitin and 165 μg phytuberin/g fresh weight of infected tissue were found. Only trace amounts (less than 0·2 μg/g fresh weight) of these compounds were found in uninoculated tissue.
54 citations
TL;DR: The results do not eliminate the possibility that medicarpin plays a role in limiting lesion development in diseases caused by fungi pathogenic to alfalfa, but preliminary evidence suggested that degradation of medicarin by L. briosiana involved a constitutively produced enzyme or enzyme complex.
Abstract: The possible role of medicarpin in limiting the size of lesions produced by foliar pathogens of alfalfa was investigated using Stemphylium botryosum, Phoma herbarum var. medicaginis and Leptosphaerulina briosiana. Medicarpin was extracted from alfalfa leaves infected with each of these pathogens after inoculation by spraying whole plants or by using the drop diffusate technique with excised leaves. Medicarpin was present in diffusate solutions only when P. herbarum var. medicaginis was used. In contrast to results obtained in drop diffusate experiments using the corn pathogen Helminthosporium turcicum, the amount of medicarpin accumulating in tissue infected by the alfalfa pathogens was relatively low. Mycelial growth of these three alfalfa pathogens and also of a fourth pathogen, Colletotrichum trifolii, was only slightly inhibited (0 to 12%) in V-8 agar containing medicarpin at a concentration of 75 μg/ml while H. turcicum was inhibited by 50% at between 25 and 50 μg/ml. P. herbarum var. medicaginis and L. briosiana caused a loss of medicarpin when it was added to cultures growing in Czapek medium. The first detectable degradation product formed by P. herbarum var. medicaginis was similar to the degradation product SB I formed by S. boryosum. This same compound was also present in diffusate solutions obtained using P. herbarum var. medicaginis. Preliminary evidence suggested that degradation of medicarpin by L. briosiana involved a constitutively produced enzyme or enzyme complex. The results do not eliminate the possibility that medicarpin plays a role in limiting lesion development in diseases caused by fungi pathogenic to alfalfa. A final conclusion must await data on the localization and concentration of medicarpin in the lesion area.
51 citations
TL;DR: Evidence indicated that the protein-lipopolysaccharide (PLP) complex may be involved with the causation of disease symptoms in cotton plants infected with V. albo-atrum.
Abstract: Logarithmic phase cultures of Verticillium albo-atrum contained an extracellular, thermostable and non-dialyzable factor which produced all symptoms of Verticillium wilt in excised cotton leaves and seedling cuttings. The active factor was isolated and found to be a protein-lipopolysaccharide (PLP) complex. The PLP attained concentrations up to 1 mg/ml in liquid cultures and was active in excised cotton leaf bioassays at concentrations of 5 μg/ml or greater. The sensitivity of 16 cotton varieties to the PLP was positively correlated with their susceptibility to Verticillium wilt, but fungus isolates of differing virulence produced comparable amounts of the PLP on various culture media. The PLP did not block the uptake of acid fuchsin into the veins of excised cotton leaves and seedling cuttings and [ 14 C]PLP readily accumulated in the small veins and interveinal areas of cotton leaves. Although the PLP could not be isolated from diseased cotton leaves, the evidence indicated that it may be involved with the causation of disease symptoms in cotton plants infected with V. albo-atrum .
51 citations
TL;DR: It was concluded that the stored substance is probably a phenol and these plant hairs will likely provide an excellent tool for the study of phenol synthesis and storage and suggested that the phenol-containing hairs themselves may be specialized organs that sense injury and elicit protective responses.
Abstract: Many vascular plants bear stem hairs that show a highly specialized morphology. Some plants, such as tomato, have several types of morphologically distinct hairs. These hairs also occur as chemically distinct types in that they store a variety of substances in high concentrations. Of the 43 plant species examined in this study, 39 were found to have stem hairs. Thirty-two of these species had specialized hairs that contained large quantities of materials that produced strongly coloured products when treated with nitrous acid and alkali. One type of tomato hair was examined in considerable detail. It was found to contain a substance that stained cherry red with nitrous acid, canary yellow with ammonia vapours, olive green with alcoholic FeCl3 and orange-red with diazo red RC. When epidermal strips bearing large numbers of hairs were extracted and chromatographed, a large spot developed at Rf 0·59. This spot appeared dark blue under ultaviolet light and was the only spot to show the same colour reactions as the materials sotred in the hairs. The spot also became blue with a yellow center when treated with 2,6-dichloroquinone-4-chloroimine. These tomato hairs store the nitrous acid reactive material in globular masses within four lobe cells that form the cap of the hairs. It was concluded that the stored substance is probably a phenol. These plant hairs will likely provide an excellent tool for the study of phenol synthesis and storage. It is suggested that the phenol-containing hairs themselves may be specialized organs that sense injury and elicit protective responses.
TL;DR: It is concluded that the endopolygalacturonases secreted by the three races of C. lindemuthianum are identical, and that their inhibitor proteins present in the three bean varieties are also identical.
Abstract: The alpha, gamma and delta races of Colletotrichum lindemuthianum secrete endopolygalacturonases which behave in an identical manner during purification on several columnn materials. The endopolygalacturonase secreted by each of these races is completely inhibited by proteins associated with the cell walls of the Red Kidney, Small White and Pinto varieties of the true bean ( Phaseolus vulgaris ). These three bean varieties differ in their response to the alpha, gamma and delta races of the pathogen. Crude extracts from the hypocotyl cell walls of each of the bean varieties possess approximately equal abilities to inhibit each of the endopolgalacturonases. The proteins from Red Kidney and Pinto beans, which inhibit the endopolygalacturonase, purify identically, and the purified protein preparations possess equal specific activities. These proteins, purified for their ability to inhibit the endopoly-galacturonase secreted by the alpha race, are equally able to inhibit the endopolygalacturonases from the gamma and delta races. The purified endopolygalacturonases from the three C. lindemuthianum races compete equally for inhibitor. It is concluded that the endopolygalacturonases secreted by the three races of C. lindemuthianum are identical, and that their inhibitor proteins present in the three bean varieties are also identical.
TL;DR: Certain amino acids inhibited, others stimulated growth of Pseudomonas group III/IV in vitro, but on leaves numbers of bacteria could not be correlated with natural levels of specific amino acids, and levels of amino acids in droplets increased as plants aged.
Abstract: Inhibition of germination of Botrytis cinerea spores by bacteria occurred in water drops placed on mature (9-week-old or over) beetroot plants but not on younger plants (6-week-old). Numbers of bacteria were higher in water drops on mature plants and species composition changed in relation to plant age. Of 9 isolates of bacteria tested in vitro a pale yellow Pseudomonas group III/IV species caused the most inhibition of germination of B. cinerea spores. Numbers of Pseudomonas group III/IV isolated both from water droplets on leaves and unwetted leaves increased in relation to plant age. On older leaves indirect evidence indicated that the bacterium may have colonized internal parts. Levels of amino acids in droplets increased as plants aged. Of 16 different amino acids the lowest concentrations were recorded on youngest (6-week-old) plants. On 10-, 13- and 16-week-old plants levels of individual amino acids were not so clearly related to plant age. Certain amino acids inhibited, others stimulated growth of Pseudomonas group III/IV in vitro , but on leaves numbers of bacteria could not be correlated with natural levels of specific amino acids.
TL;DR: Changes in the multiple molecular forms and activity of enzymes are biochemical symptoms of disease, may be a basis for the increased metabolism associated with infection and suggest profound interactions between parasite and host.
Abstract: Multiple molecular forms of 14 enzymes (isoenzymes) from near-isogenic barley lines inoculated with powdery mildew were studied by polyacrylamide disk electrophoresis. Following inoculation of the susceptible line (ml-g) the number of isozyme bands of acetylesterase, acid phosphatase, malate dehydrogenase (NADP), succinate dehydrogenase and peroxidase increased. These new bands were not detected in extracts of healthy tissue or mycelium and conidia from infected leaves; their intensity was not reduced by removing mycelium and conidia before preparing extracts. Only the new peroxidase band appeared within one day after inoculation. Eleven enzymes from inoculated susceptible lines showed an increase in intensity of one or more bands within 7 days; four enzymes showed a decrease. A hypersensitive line (Ml-k) showed changes after inoculation that were similar to those of the susceptible line. With a resistant line (Ml-g) there was an intensity increase in one or more bands of seven enzymes within 7 days after inoculation. Such changes in the multiple molecular forms and activity of enzymes are biochemical symptoms of disease, may be a basis for the increased metabolism associated with infection and suggest profound interactions between parasite and host.
TL;DR: The wide variety of regulatory controls governing lyase synthesis and the repressive as well as synergistic effects of vegetable extracts on synthesis suggest that the etiology of bacterial soft rot diseases can be influenced by such regulatory mechanisms.
Abstract: Regulation of pectate lyase synthesis was examined in Erwinia and Pseudomonas species. Soft rot bacteria produced 100- to 1000-fold more enzyme per cell under optimal conditions than did other bacterial pathogens or saprophytes. Among pseudomonads, only Pseudomonas marginalis and a few other fluorescent strains isolated from plant tissue synthesized pectate lyase. Constitutive synthesis was common in this group. In contrast, lyase synthesis in most Erwinia species examined was inducible. Polypectate and pectin were effective carbon sources for lyase induction in some Erwinia strains while other strains showed much higher inducible synthesis on pectin than on polypectate. Vegetable extracts had profound effects on lyase synthesis. Potato extract, which was previously reported as exerting a synergistic effect on induction of pectate lyase in Erwinia carotovora ATCC 8061 grown on pectin, repressed lyase synthesis in other Erwinia strains. At high concentrations, extracts of carrot, lettuce and onion severely repressed constitutive and inducible synthesis. At low concentrations, lettuce and onion extracts stimulated constitutive lyase synthesis in Pseudomonas marginalis . The wide variety of regulatory controls governing lyase synthesis and the repressive as well as synergistic effects of vegetable extracts on synthesis suggest that the etiology of bacterial soft rot diseases can be influenced by such regulatory mechanisms.
TL;DR: Development of the bacterially induced hypersensitive reaction was overcome when tobacco leaves were pretreated with 5 × 10−5 m -kinetin, or other compounds with cytokinin activity, 48 h before inoculation with Pseudomonas pisi.
Abstract: Development of the bacterially induced hypersensitive reaction was overcome when tobacco leaves were pretreated with 5 × 10−5 m -kinetin, or other compounds with cytokinin activity, 48 h before inoculation with Pseudomonas pisi. Bacterial growth in the treated tissue was not affected. Developmental stage of the treated leaves was critical for demonstrating the protective effect of cytokinin. Only older leaves approaching senescence exhibited this effect. Development of symptoms of wildfire disease caused by Pseudomonas tabaci were delayed by cytokinin treatment, but 72 h after inoculation both water (control) and cytokinin-treated leaves exhibited the same degree of necrosis.
TL;DR: It is argued that for these reasons Botrytis cinerea could not infect tulips, but thatBotrytis tulipae could overcome the barrier of the inhibitory substances.
Abstract: The function of preformed substances in tulips, so-called tuliposides, in disease resistance was examined. As an example, the host-parasite relationships between tulips and Botrytis cinerea and Botrytis tulipae, respectively, were studied. Botrytis tulipae and Botrytis cinerea caused a release of tuliposides from both attached and detached pistils by increasing the permeability of cell membranes. Botrytis cinerea caused an essentially higher increase in permeability. Under the influence of Botrytis cinerea the tuliposides were converted into lactones with a high biological activity. Botrytis tulipae, on the contrary, caused a cleavage of the tuliposides into the corresponding acids with a very low biological activity. Botrytis cinerea was more sensitive to the inhibitory substances than Botrytis tulipae. It is argued that for these reasons Botrytis cinerea could not infect tulips, but that Botrytis tulipae could overcome the barrier of the inhibitory substances.
TL;DR: Experiments on roots of wheat, corn and oats indicate that fusicoccin lacks, or shows in a very low degree, the typical ability of auxins to inhibit cell elongation in root tissues, and the stimulation of water uptake in pea stem sections is accompanied by an irreversible extension of the cell wall.
Abstract: The activity of fusicoccin in stimulating water uptake in various plant tissues was investigated and compared with that of indole-3-acetic acid. In leaf disks (tomato, clover, tobacco) fusicoccin induced a significant increase of water uptake, but indole-3-acetic acid was inactive. The stimulation of water uptake by fusicoccin occurs in spite of the fact that the osmotic pressure values of the treated tissues become during incubation progressively lower than those found in the controls. This is interpreted as indirect evidence in favour of a capacity of fusicoccin to irreversibly extend the cell wall. Experiments on roots of wheat, corn and oats indicate that fusicoccin lacks, or shows in a very low degree, the typical ability of auxins to inhibit cell elongation in root tissues. The stimulation of water uptake in pea stem sections is accompanied by an irreversible extension of the cell wall. The effects of fusicoccin and indole-3-acetic acid on the increase in fresh weight and elongation of pea segments are very similar. The optimal effect of fusicoccin on the growth of pea stem segments is consistently higher than that of indole-3-acetic acid and no inhibitory effect was detected even at the highest concentration used (1·5 × 10−4 m ).
TL;DR: Evidence is presented that R. secalis does not produce, in vitro, toxic metabolites which specifically affects host membranes which specifically affect host membranes.
Abstract: The fungus Rhynchosporium secalis grows for 10 to 14 days after infection beneath the cuticle of barley leaves. Soluble nutrients which are present in the free space of the leaf are available for utilization by the fungus. Within 3 days after infection, and at least 7 days before the first disease symptoms appear, the fungus causes an increase in the permeability of the underlying host cells so that the concentration of nutrients in the free space is increased. The increase is greater in a susceptible than in a resistant host variety. Evidence is presented that R. secalis does not produce, in vitro , toxic metabolites which specifically affect host membranes.
TL;DR: The germination self-inhibitor from uredospores of sunflower rust, corn rust and snapdragon rust was found to be methyl 3,4-dimethoxycinnamate, and cis isomer of the ester is the only active form of the inhibitor from these spores and the spores of bean rust.
Abstract: The germination self-inhibitor from uredospores of sunflower rust, corn rust and snapdragon rust was found to be methyl 3,4-dimethoxycinnamate. Studies carried out in darkness have shown clearly that the cis isomer of the ester is the only active form of the inhibitor from these spores and the spores of bean rust. This inhibitor also prevents germination of crown rust uredospores at low concentration. Methyl cis-ferulate was found to be the only active inhibitor of wheat stem rust uredospores, race 56. Uredospores of flax rust, race 1, and wheat stem rust, race 126-ANZ-6,7, were insensitive to either inhibitor.
TL;DR: A phytotoxic glycopeptide was isolated from cultures of Corynebacterium insidiosum and from alfalfa plants infected with this organism and meets the requirements of a “vivotoxin”.
Abstract: A phytotoxic glycopeptide was isolated from cultures of Corynebacterium insidiosum and from alfalfa plants infected with this organism. The toxin causes wilting in both leaves and stems of test plants and exhibits no host specificity. Biological activity of the compound is dependent on time and on concentration. The toxin is stable to wide fluctuations in pH and still retains biological activity after heating at 121 °C for 2 h. Partial acid hydrolysis of the toxin abolished its biological activity. Modification of the glycopeptide obtained from cultures to remove chelated copper results in a colorless apotoxin which still possesses biological activity and a molecular weight virtually identical to the untreated toxin. A phytotoxic compound was also isolated from infected alfalfa tissue and was present in quantities large enough to account for symptom production in biological assay tests. The glycopeptide from alfalfa extracts was similar to the apotoxin (glycopeptide from cultures) in that the same sugar residues were present, the molecular weights were the same and the optical rotations were comparable. The compound meets the requirements of a “vivotoxin”.
TL;DR: The present findings demonstrate that, in vitro, the precursor must be split chemically or enzymically to yield the fungitoxic tulipalin A.
Abstract: Extracts of pistils, white bulb skins and outer bulb scales of tulip were prepared using methanol, acetone and buffers of various pH values. Except for the pH 7·5 extract, all extracts of the tulip cultivars under study contained a precursor of the fungitoxic substance tulipalin A. The precursor is not toxic to Fusarium oxysporum, and is relatively stable below a pH of about 5·4 and relatively unstable above pH 6·5 in extracts or in a fungal culture medium. Buffered extracts of bulb tissues contain enzymes that liberate tulipalin A very rapidly at pH values above 5. The present findings demonstrate that, in vitro, the precursor must be split chemically or enzymically to yield the fungitoxic tulipalin A.
TL;DR: Following infection of tomato plants by Fusarium oxysporum f.
Abstract: Following infection of tomato plants by Fusarium oxysporum f. lycopersici an inhibitor of the fungus is found in the roots and stems of the plants. The inhibitor, probably α-tomatine, is produced by both resistant and susceptible cultivars and its roˆle, if any, in resistance of tomato to the fungus has yet to be established.
TL;DR: Combined gas chromatography-mass spectrometry showed that the polysaccharide contained glucose, galactose, mannose and galacturonic acid, presumed to be PLP degradation products.
Abstract: A protein-lipopolysaccharide (PLP) complex was isolated from dialyzed log-phase culture fluids of Verticillium albo-atrum by DEAE-cellulose chromatography, agarose gel filtration and column electrophoresis. Excised cotton leaves supplied 5 μg/ml of the purified PLP for 24 to 36 h were indistinguishable from leaves on the fungus-infected plants. The purified PLP was somewhat unstable, tending to aggregate and precipitate in very low ionic strength solutions and degrading to lower molecular weight products in very high ionic strength solutions. The PLP had a molecular weight of c. 3 × 10 6 and was a major component of log-phase Verticillium cultures. Older cultures contained progressively larger quantities of related lower molecular weight materials, presumed to be PLP degradation products. The PLP was highly acidic and was composed of about 70% polysaccharide and 15% each of protein and lipid. Combined gas chromatography-mass spectrometry showed that the polysaccharide contained glucose, galactose, mannose and galacturonic acid.
TL;DR: Solute leakage from inoculated peas was greater than from non-inoculated peas, although the rate of increase in leakage became similar shortly after infection began, and mitochondrial damage may be significant in the deterioration of peas infected with A. ruber.
Abstract: Only 30% of peas inoculated with Aspergillus ruber germinated after 14 weeks of storage, whereas 80% of similarly stored, non-inoculated peas germinated normally. Solute leakage from inoculated peas was greater than from non-inoculated peas, although the rate of increase in leakage became similar shortly after infection began. Light and electron microscopy of cells in the embryonic axes revealed plasmalemma damage and shrinkage of the cytoplasm away from the cell wall. Shrunken cytoplasm was evident in a greater percentage of cells from infected peas than from uninfected peas. Coalesced lipid vesicles and a disordered ribosomal matrix were observed in tissue from both infected and uninfected peas. The majority of the mitochondria observed in cells from infected peas were damaged, as contrasted with only a few of the mitochondria from uninfected peas. Mitochondrial damage may be significant in the deterioration of peas infected with A. ruber since it occurred shortly after infection and was never very severe in tissue from uninfected peas.
TL;DR: Based on pathogenicity testing on six differential pea varieties, the isolates could be divided into four groups and one of the groups has the same virulence as race 1, already described in the United States.
Abstract: From Norwegian field soil samples a total of 14 isolates of Aphanomyces euteiches were obtained. Based on pathogenicity testing on six differential pea varieties, the isolates could be divided into four groups. One of the groups has the same virulence as race 1, already described in the United States. None of the Norwegian isolates had a virulence pattern similar to that designated as race 2 by previous workers. It is proposed to name the remaining three groups races 3,4 and 5 respectively. Races 3 and 4 are highly virulent on five of the differential varieties and race 5 is highly virulent on all six varieties.
TL;DR: It is concluded that this characteristic increase in protein synthesis is one of the first detectable expressions of disease resistance in the flax-flax rust interaction.
Abstract: Six gene-for-gene interactions between flax and Melampsora lini exhibited changes in the synthesis of soluble proteins 6 to 18 h after inoculation. The rates at which various-sized proteins were synthesized varied for each different gene-for-gene combination. The increased rate of synthesis detected in particular fractions from a column separation was reproducible and characteristic for certain gene combinations. In general, the net rate of protein synthesis increased in the four incompatible (resistant) interactions but did not increase in the two compatible (susceptible) interactions. It is concluded that this characteristic increase in protein synthesis is one of the first detectable expressions of disease resistance in the flax-flax rust interaction.
TL;DR: In this article, nutritional experiments with both uredospores and transferred colonies of the flax rust, Melampsora lini (Pers.) Lev are described, and the results are discussed in relation to recent work on axenic culture of the rusts.
Abstract: Nutritional experiments with both uredospores and transferred colonies of the flax rust, Melampsora lini (Pers.) Lev are described. High amounts of monobasic potassium phosphate (1 g/l) reduced growth of mycelium from uredospores. Races of this rust differed in their capacity to grow on a range of media. Using transferred material, it was established that Melampsora lini can utilize sucrose, glucose, fructose, mannose, mannitol, trehalose, raffinose, ribitol, sorbitol and maltose. It did not utilize galactose. In addition to inorganic salts and a carbohydrate source, two amino acids, alanine and methionine, were found to be required for growth. The results are discussed in relation to recent work on axenic culture of the rusts.
TL;DR: Results show that P. circinata toxin changes the characteristics of the plasma membrane, but do not prove that the membrane is the initial site of toxin activity, and suggest that resistant sorghum cells may have sites with low affinity for toxin.
Abstract: Susceptible tissues of sorghum (Sorghum vulgare) exposed to toxin from Periconia circinata had increased loss of electrolytes within 20 min; resistant sorghum tissues were not affected. Electrolyte loss from susceptible tissues increased with increases in toxin concentration from 0·1 to 100 μg/ml; the correlation was the basis for a new toxin assay. Toxin decreased the ability of tissue to take up and/or to retain amino acids from an ambient solution. Toxin also decreased the amount of amino acid incorporation into insoluble components of the cell. Tissues became less sensitive to toxin following 12 h exposure to cycloheximide. Similar exposures to phospholipase D and uranyl salts also decreased the sensitivity of tissues to toxin. Results show that P. circinata toxin changes the characteristics of the plasma membrane, but do not prove that the membrane is the initial site of toxin activity. Resistant sorghum cells may lack toxin receptor sites, or have sites with low affinity for toxin.