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During a 4-week period in May through June 1996, 15% of 50 mature lisianthus (Eustoma grandiflorum) ‘Maurine Blue’ and ‘Maurine White’ plants exhibited stem blight in a landscape planting in west-central Florida. Initial disease symptoms included stem necrosis at the soil line, and yellowing and tan discoloration of leaves. As blighting of the stem progressed, infected plants wilted and died. Symptomatic stem sections from three plants were surface-disinfested in 0.5% NaOCl and placed on acidified 25% potato dextrose agar (APDA). Sclerotium rolfsii Sacc. was isolated from all three diseased stems. Pathogenicity of each of three S. rolfsii isolates was confirmed using two lisianthus ‘Flamenco Blue’ plants grown in 10.2-cm-diameter plastic pots containing a peat-based medium. Sclerotia produced on APDA were sprinkled on the soil surface around each plant base; 50, 100, and 5 sclerotia from isolates A, B, and C, respectively, were used (isolate C grew more slowly and produced fewer sclerotia than either A or B). Two noninoculated lisianthus served as controls. Plants were maintained in a greenhouse at minimum and maximum temperatures of ≈24 and 35°C, respectively. Plants inoculated with sclerotia from isolates A and B developed blight symptoms within 6 days. One of two plants inoculated with isolate C developed blight symptoms within 17 days, and the other remained symptomless, as did the control plants. Infection by S. rolfsii was confirmed by reisolation from symptomatic tissue. This is the first report of stem blight of lisianthus caused by S. rolfsii.

Angular leaf spot of cucurbits is generally considered to be caused by Pseudomonas syringae pv. lachrymans. It has a worldwide distribution and has been observed to emerge sporadically under humid and wet conditions. Reports of multiple P. syringae pathovars associated with the disease and lack of molecular analysis has left the true diversity of populations in the United States unclear. In this study, we collected 27 P. syringae strains causing foliar lesions and blighting on watermelon, cantaloupe, and squash in Florida, Georgia, and California over several years. Strains were fluorescent on King’s medium B agar and displayed the typical phenotypic and biochemical characteristics of P. syringae. P. syringae pv. lachrymans is a member of genomospecies 2. However, the genetic profiles obtained through both MLSA (gyrB, rpoD, gapA, and gltA) and BOX-PCR (BOXA1R) identified 26 of the P. syringae strains to be distributed among three clades within genomospecies 1, and phylogenetically distinct from genomospecies 2 member P. syringae pv. lachrymans. A novel MLSA haplotype of the pathogen common to all states and cucurbit hosts was identified. Considerable genetic diversity among P. syringae strains infecting cucurbits is associated with the same disease, and reflects the larger ecological diversity of P. syringae populations from genomospecies 1.

We present a first-principles investigation of the electronic properties of monolayer ${\mathrm{WS}}_{2}$ coated with an overlayer of Fe. Our ab initio calculations reveal that the system is a half-metallic ferromagnet with a gap of $\ensuremath{\sim}1$ eV for the majority spin channel. Furthermore, the combined effect of time-reversal symmetry breaking due to the magnetic Fe overlayer and the large spin-orbit coupling induced by W gives rise to nondegenerate K and ${\mathrm{K}}^{\ensuremath{'}}$ valleys. This has a tremendous impact on the excited-state properties induced by externally applied circularly polarized light. Our analysis demonstrates that the latter induces a singular hot-spot structure of the transition probability around the K and ${\mathrm{K}}^{\ensuremath{'}}$ valleys for right and left circular polarization, respectively. We trace back the emergence of this remarkable effect to the strong momentum dependent spin-noncollinearity of the valence band involved. As a main consequence, a strong valley-selective magnetic circular dichroism is obtained, making this system a prime candidate for spintronics and photonics applications.

Ferromagnetic L10 ordered alloys are extensively studied nowadays as good candidates for high density magnetic storage media due to their high magnetic anisotropy, related to their chemical order anisotropy. Epitaxial thin bilayers NiPt/FePt/MgO(001) have been grown at 700 K and annealed at 800 K and 900 K. At 800 K, the L10 long-range order increases without measurable interdiffusion. At 900 K, the interdiffusion takes place without destroying the L10 long-range order. This surprising observation can be explained by different diffusion mechanisms that are energetically compared using molecular dynamics simulations in CoPt in the second moment tight binding approximation. In addition, the frequencies of the normal modes of vibration have been measured in FePd, CoPt and FePt single crystals using inelastic neutron scattering. The measurements were performed in the L10 ordered structure at 300 K. From a Born-von Karman fit, we have calculated the phonon densities of states. The migration energies in the 3 systems have been estimated using the model developed by Schober et al. (1981). The phonon densities of states have also been used to calculate several thermodynamic quantities as the vibration entropy and the Debye temperature.

Bacterial spot disease on tomato is a major problem in tropical, subtropical, and temperate climates. Variation within this organism has been well documented. Two distinct groups, i.e., A and B, were identified in the early 1990s based on phenotypic and genotypic tests. These two groups were determined to be distributed widely throughout the world. The two groups were placed in Xanthomonas axonopodis pv. vesicatoria and X. vesicatoria, respectively in 1995. Following the identification of these two groups, two additional groups, C and D, have been identified that are pathogenic to pepper, tomato, or both hosts. The C group was originally isolated in 1991 and has more recently been found in many tomato production regions in the United States and in Mexico. Group D strains originally isolated in Costa Rica were determined to be closely related to X. gardneri, isolated by Sutic in Yugoslavia in 1957. The group D strains have been identified more recently in Michigan and in Brazil. Based on DNA homology experiments the C and D strains were determined to have less than 70% DNA similarity with strains from the other groups, with the type strain of X. axonopodis, and with the currently classified species within Xanthomonas. We have proposed that the C group strains be designated X. perforator sp. nov. and that the D group strains, which had less than 70% DNA similarity with any of the Xanthomonas species and which never had taxonomic status be named X. gardneri to reflect the specific epithet proposed by Sutic in 1957. Tomato races designated T1 (group A strains), T2 (group B strains) and T3 (group C strains) have been identified based on differential reactions with a group of tomato genotypes. Recently, two new races, T4 and T2, were identified in Florida. These races are group C strains with mutations in the avrXv3 and the avrXv3 and avrXv4, respectively.

Tumorigenic Agrobacterium strains isolated from tumours growing on pruned branches of Ficus benjamina have previously been shown to have unique opine metabolism and sufficient 16S rRNA sequence differences to suggest that they belong to a new species. DNA-DNA hybridization results confirmed that these strains represent a new species and Agrobacterium larrymoorei sp. nov. (type strain ATCC 51759T = CFBP 5473T = NCPPB 4096T) is proposed as the name for the species.

▪ Abstract Xanthomonas campestris pv. vesicatoria, causal agent of bacterial spot of tomato and pepper, had been considered for nearly 70 years to be a relatively homogeneous organism. However, in the past decade this bacterium was determined to be composed of two genetically and phenotypically distinct groups. The two groups, designated A and B, were distinguished based on amylolytic activity, expression of unique protein bands, reaction on differential hosts (tomato races T1 and T2), reaction patterns with monoclonal antibodies, DNA restriction profiles, and DNA:DNA hybridization. The A and B groups were placed into X. axonopodis pv. vesicatoria and X. vesicatoria, respectively. A third group, designated C, was pathogenically (race T3) and serologically distinct from A and B strains, and formed unique DNA restriction profiles. DNA:DNA hybridization data suggest that C is distinct but related to A strains and may represent a subspecies of A. A final group, designated D, consisted of X. gardneri, an organism identified in Yugoslavia in 1957, and also found in Costa Rica. Group D was determined to be genetically distinct from strains within the other two groups; it represents a third Xanthomonas species pathogenic on tomato and pepper.

Bouzar et al. (1997) have recently investigated the surface of B2 FeCr alloy. In all cases of crystal growth 〈0 0 1〉, 〈1 1 0〉 and 〈1 1 1〉 they found the local polarization at the surface to be antiferromagnetically coupled with the subsurface layer in contrast to parallel coupling between Fe and Cr in bulk FeCr. In order to assert these results, we have investigated the local polarization of Fe at the (0 0 1) surface of this alloy with a tight-binding linear muffin tin Orbitals (TB-LMTO) model. Using general gradient approximation with Langreth-Mehl-Hu functional for p(1 × 1) and c(2 × 2) configurations we found the local polarization at the Fe surface layer to be antiferromagnetically coupled with the subsurface Cr layer and high magnetic moments compared to the bulk values.

The Monte Carlo model previously developed to simulate the ordering kinetics in B2 phases is now applied to the calculation of phase diagrams that display DO 3 and B2 structures and to that of the relaxation of the long range order parameters in DO 3 and B2 phases and at the DO 3 –B2 and DO 3 –A2 transitions. The model, which is based on a vacancy jump mechanism, lies on an Ising Hamiltonian with interaction energies between first and second nearest neighbors. The simulations reproduce experimental trends for the activation energy of the self-diffusion in equiatomic FeCo and for the migration energy in Fe 3 Al and Fe 3 Si compounds. Critical slowing-down of the relaxation times are observed at the order–disorder transitions, in qualitative agreement with experimental results in Fe 3 Al.

Crown gall tumours induced by four groups of Agrobacterium tumefaciens isolates, derived from galls from four different locations in North and South America and Europe, were found to contain mannityl opine-related metabolites derived from condensation of glucose with glutamine followed by Amadori rearrangement. The opines were characterized spectroscopically as N- (1′-deoxy- d -fructos-1′-yl)-5-oxo- l -proline , N α - (1′-deoxy- d -fructos-1′-yl)- l -glutamine and its spiropyranosyl lactone, chrysopine. Tumours induced by A. tumefaciens strain 2788 and by Ficus strains also contained nopaline, while those induced by A. tumefaciens K224, K289 and Chry9 contained l , and an unidentified opine, pseudo-nopaline.

Two genetically diverse groups of strains were identified among cultures of Xanthomonas campestris pv. vesicatoria isolated from plants with bacterial spot of pepper and tomato. Group A strains do not pit pectate gels or hydrolyze starch, whereas group B strains are strongly positive for these reactions. Group A strains cause a hypersensitive reaction in plants of tomato breeding line Hawaii 7998, but group B strains do not. Other differences between the two groups of strains were discovered in tests for utilization of carbon compounds, serology, fatty acid profiles, silver-stained protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels, and DNA restriction enzyme digestion profiles. The levels of DNA homology between strains belonging to the same group were more than 74%, but the levels of DNA homology between strains belonging to different groups were less than 46%. The two groups of strains have different genetic backgrounds, but cause essentially the same disease of tomato and pepper.

Crown gall tumours induced by four groups of Agrobacterium tumefaciens isolates, derived from galls from four different locations in North and South America and Europe, were found to contain mannityl opine-related metabolites derived from condensation of glucose with glutamine followed by Amadori rearrangement. The opines were characterized spectroscopically as N- (1′-deoxy- d -fructos-1′-yl)-5-oxo- l -proline , N α - (1′-deoxy- d -fructos-1′-yl)- l -glutamine and its spiropyranosyl lactone, chrysopine. Tumours induced by A. tumefaciens strain 2788 and by Ficus strains also contained nopaline, while those induced by A. tumefaciens K224, K289 and Chry9 contained l , and an unidentified opine, pseudo-nopaline.

Summary h Crown gall was observed in 99% of the plant nurseries surveyed in the major fruit tree production region of Algeria. Among 11 tree species surveyed, those with highest disease incidence were peach (5.39%), almond (3.43%), cherry (1.50%), apple (1.47%), and olive (1.30%). None of the quince and fig trees inspected had crown gall. Significant differences in the frequency of galled plants were correlated with the rootstock used by nurserymen for peach, cherry, apple and pear trees. Analysis of 60 galled samples, which yielded 154 Agrobacterium tumefaciens strains, revealed that biovar 2 and agrocin 84-sensitive strains were predominant among local agrobacteria. The ratio of agrocin-sensitive to agrocin-resistant was more than 3 times higher for biovar 2 (6:1) than for biovar 1 (1.67:1) strains; thus, suggesting that biovar 2 strains are most likely to harbor a nopaline/agrocinopine A-type Ti-plasmid. Biological control of crown gall was achieved in a field experiment in which peach ’Missour’ seedlings were dipped first in a suspension of A radiobacter K84 and subsequently in a suspension of a local agrocin-sensitive strain. In the same experiment, K84 reduced the incidence of galling by 94% in seedlings inoculated with a local agrocin-resistant A tumefaciens strain. These data indicate that K84 could be used in Algeria despite the presence of agrocin- resistant strains.

Until recently, tomato race 1 (T1) of Xanthomonas campestris pv. vesicatoria was the only race causing bacterial spot of tomato in Florida. In 1991, tomato race 3 (T3) was first identified in 3 of 13 tomato production fields surveyed. By 1994, T3 was observed in 21 of 28 fields and was the only race identified in 14 fields. In field studies, tomato genotypes with resistance to either T1 or T3 or susceptibility to both were co-inoculated with strains of both races. Lesions on 10 plants in each of three replications for each genotype were sampled three times during the experiment; bacterial isolations were made from each lesion, and tomato race identifications were made for each strain. At the third sampling date, T3 was isolated from 97% of the lesions on the susceptible genotype Walter and the T1-resistant genotype Hawaii 7998, while T3 was isolated from 23% of the lesions and T1 from the remaining 77% on the T3-resistant genotypes PI 128216 and PI 126932. In surface population studies done in growth rooms, suspensions of T1 and T3 were applied alone and in combination to the leaf surfaces of susceptible and resistant genotypes. T1 populations were reduced more than 10-fold when applied in combination with T3, compared with populations that developed when T1 was applied alone. T3 populations were not affected when applied in combination with a T1 strain. In greenhouse studies with the T3-resistant genotype Hawaii 7981, disease was significantly reduced in plants inoculated with T3 in combination with T1, compared with plants inoculated with T1 alone. These results clearly demonstrate the competitive nature of T3 in the presence of T1 and help explain the emergence of T3 as a prevalent race in Florida.

Monte Carlo simulations have been performed to investigate the relaxation of the L10 long-range order in dimensionally reduced systems. The effect of the number of (001)-type monatomic layers and of the pair interaction energies on these kinetics has been examined. The vacancy migration energies have been deduced from the Arrhenius plots of the relaxation times. A substantial increase in the migration energy for small film thickness is observed. The results agree with previous Monte Carlo simulations and with recent experimental results in L1_0 thin films and multilayers., 10 pages, and 7 figures

We present atomic-scale computer simulations in equiatomic L1$_0$-CoPt where Molecular Dynamics and Monte Carlo techniques have both been applied to study the vacancy-atom exchange and kinetics relaxation. The atomic potential is determined using a Tight-Binding formalism within the Second-Moment Approximation. It is used to evaluate the different saddle-point energies involved in a vacancy-atom exchange between nearest-neighbour sites. The potential and the saddle-point energies have been used to simulate the relaxation of the long-range order in CoPt using a Monte Carlo technique. A vacancy migration energy of $0.73\pm 0.15 eV$ and an order-disorder transition temperature of 935 K have been found., Comment: 8 pages, 4 figures; to appear in Eur. Phys. J. B

Four phenotypic xanthomonad groups have been identified that are pathogenic to pepper, tomato, or both hosts. These include groups A and C which are found in Xanthomonas axonopodis pv. vesicatoria, group B found in X. vesicatoria, and group D found in 'X. gardneri'. We present DNA:DNA hybridization data in which X. axonopodis pv. vesicatoria group A and C strains have less than 70% DNA relatedness with each other, with the type strain of X. axonopodis, and with the currently classified species within Xanthomonas and, therefore, should be removed from this species and given species status. We present information that the A strains most closely resemble the strains originally isolated by Doidge in 1921. In an attempt to avoid confusion in nomenclature as stated in Principle 1 of the Bacteriological Code, we propose that the A strains of X. axonopodis pv. vesicatoria be renamed as X. euvesicatoria (ATCC11633T= NCPPB2968T = ICMP 109T = ICMP 98T). Use of the euvesicatoria epithet should be reserved for strains originally identified by Doidge, which she designated Bacterium vesicatorium (Ann. Appl. Biol. 7: 407-430, 1921) in the original description when she referred to those strains as being feebly amylolytic. The name X. perforans sp. nov. is proposed for the C group of strains previously designated as X. axonopodis pv. vesicatoria (ATCC BAA-983T = NCPPB 4321T). We also propose that 'X. gardneri', which has less than 70% DNA relatedness with any of the Xanthomonas species and which has never had taxonomic status, be named X. gardneri (ATCC 19865T = NCPPB 881T) to reflect the specific epithet proposed by Sutic in 1957.

Since the late 1980s, a bacterium has been routinely isolated from leafspots on geranium (Pelargonium X hortorum L. H. Bailey) and more infrequently from petunia (Petunia hybrida). When inoculated on healthy geranium and petunia leaves, these bacteria caused leafspots identical to those observed on naturally infected geranium plants. Carbon substrate utilisation (BIOLOG) and fatty acid analysis (FAME) identified these isolates to the genus Acidovorax. According to BIOLOG, FAME, and pulsed-field gel electrophoresis (PFGE) data, the geranium and petunia strains formed a very tight phenotypic group that was distinct from other Acidovorax strains tested. In DNA:DNA hybridisation analyses, the geranium strains had greater than 90% homology to each other and to the petunia strain, but less than 50% homology to other Acidovorax species with the exception of A. konjaci (52%). Sequence analysis of the 16S rRNA revealed that the geranium and petunia strains had 99% homology with A. konjaci. Based on PFGE, BIOLOG, FAME, and DNA:DNA hybridisation results, the geranium petunia strains are very closely related to each other and are most closely related to A. konjaci.

Biovar (bv) 2 strains of Agrobacterium produced more acid from glucose than strains from the other two biovars This property caused the development of a clear zone around bv-2 colonies growing on potato glucose agar supplemented with 0.8% calcium carbonate. This simple cultural test produced results after 2 d at 28°C, and distinguished all 22 bv-2 strains tested from strains of other chromosomal groups of Agrobacterium; none of the 42 bv-1 and 16 bv-3 strains tested produced a clear zone around their colonies.

The taxonomy and evolutionary relationships among members of the genus Xanthomonas associated with tomato and pepper have been a matter of considerable controversy since their original description in 1921. These bacteria, which are a major affliction of tomato and pepper crops in warm and humid regions, were originally described as a single species, but subsequent research has shown the existence of at least two genetic groups differentiated by physiological, biochemical and pathological characteristics. This work synthesizes the findings from several approaches, including pathogenicity tests, enzymic activity, restriction fragment analysis of the entire genome, DNA-DNA hybridization and RNA sequence comparisons based on a 2097 base sequence comprising the 16S rRNA gene, the intergenic spacer located between the 16S and 23S rRNA genes and a small region of the 23S rRNA gene. Within the group of xanthomonads pathogenic on pepper and tomato four distinct phenotypic groups exist, of which three form distinct genomic species. These include Xanthomonas axonopodis pv. vesicatoria (A and C group), Xanthomonas vesicatoria (B group) and Xanthomonas gardneri (D group). On the basis of phenotypic and genotypic differences between A- and C-group strains, the C strains should be considered as a subspecies within Xanthomonas axonopodis pv. vesicatoria.

During a 4-week period in May through June 1996, 15% of 50 mature lisianthus (Eustoma grandiflorum) ‘Maurine Blue’ and ‘Maurine White’ plants exhibited stem blight in a landscape planting in west-central Florida. Initial disease symptoms included stem necrosis at the soil line, and yellowing and tan discoloration of leaves. As blighting of the stem progressed, infected plants wilted and died. Posted 6 June 2000.

The levels of relatedness of strains of Xanthomonas fragariae collected over several years from locations in Canada and the United States were compared by determining fatty acid methyl ester profiles, restriction fragment length polymorphisms (RFLP) based on pulsed-field gel electrophoresis (PFGE) analysis, and DNA-DNA reassociation values. Based on qualitative and quantitative differences in fatty acid profiles, the strains were divided into nine groups and four groups by the MIDI “10% rule” and unweighted pair analysis, respectively. Restriction analysis of genomic DNA by PFGE with two endonucleases ( Xba I and Spe I) revealed four distinct profiles. When a third endonuclease ( Vsp I) was used, one group was divided into three subgroups. The profile of the American Type Culture Collection type strain differed from the profile of every other strain of X. fragariae . Considerable diversity was observed within X. fragariae , although the majority of the strains represented a clonal population. The four groups based on fatty acid profiles were similar to the four groups based on RFLP, but neither method related groups to the geographic origins of the strains. The DNA-DNA reassociation values were high for representative strains, providing evidence that all of the strains belong to the same species.

Crown gall tumors, collected from branches of 1-year-old weeping fig (Ficus benjamina L.) trees, yielded both tumorigenic and nonpathogenic agrobacteria. On the basis of classical diagnostic tests, the nonpathogenic strains were identified as Agrobacterium tumefaciens, whereas the tumorigenic strains could not be assigned to any of the known terrestrial Agrobacterium spp. The tumorigenic strains also differed from other members of the genus by producing more acid from mannitol. According to cluster analysis of carbon substrate oxidation (GN Microplate; Biolog, Inc.) and fatty acid content, the tumorigenic fig strains were distinct from strains of A. tumefaciens, Agrobacterium rhizogenes, Agrobacterium vitis, and Agrobacterium rubi. Furthermore, they had unusual opine metabolism, inducing tumors that synthesized nopaline and three recently discovered opines: chrysopine (d-lactone of N-1-deoxy-D-fructosyl-L-glutamine, and N-1-deoxy-D-fructosyl-L-glutamine, and N-1-deoxy-D-fructosyl-5-oxo-L-proline. The nonpathogenic A. tumefaciens strains present in the same tumors were unable to degrade any of the opines tested. The phylogenetic position of the tumorigenic fig strain AF3.10 was inferred from comparing its rrs (i.e., 16S rRNA gene) sequence with those from the type strains of Agrobacterium and Rhizobium species. The analysis showed that strain AF3.10 clustered with A. tumefaciens and A. rubi but not with A. vitis and was far removed from A. rhizogenes. However, the sequence was significantly different from those of A. tumefaciens and A. rubi to suggest that the tumorigenic fig strain may be a new Agrobacterium species that is as different from A. tumefaciens and A. rubi as these two species are from one another.

In 1998, a new disease was detected on 3-week-old commercial broccolini (Brassica oleracea L. var. botrytis × B. alboglabra) transplants in a Salinas Valley, Monterey County, CA greenhouse. Initial symptoms were small (2 to 4 mm diameter) circular to angular, water-soaked spots. As the disease progressed, spots remained relatively small, but turned tan to brown. When diseased tissues were macerated and streaked on King's medium B, a blue-green fluorescent pseudomonad was consistently isolated. Strains were levan positive, oxidase negative, and arginine dihydrolase negative. Strains did not rot potato slices, but induced a hypersensitive reaction on tobacco (Nicotiana tabacum L. ‘Turk’). Fatty acid methyl ester analysis (MIS-TSBA, version 4.10, MIDI Inc., Newark, DE) indicated that strains had a high similarity index (0.82 or higher) to Pseudomonas syringae, and GN (version 3.50, Biolog, Inc., Hayward, CA) profiles also identified strains as P. syringae. The bacterium associated with the disease, therefore, was identified as P. syringae van Hall. Pathogenicity was demonstrated by growing inoculum in nutrient broth shake cultures for 48 h, misting the broth cultures (1×106 CFU/ml) onto broccolini (cv. Aspabrock), and subjecting the plants to 48 h of high humidity. Control plants were misted with sterile nutrient broth. After 4 to 5 days in a greenhouse, leaf spot symptoms developed on all inoculated broccolini plants, and reisolated strains were characterized and found to be P. syringae. Control plants remained symptomless. The results of two sets of pathogenicity tests were the same. Repetitive sequence-based polymerase chain reaction using the BOXA1R primer resulted in identical banding patterns for the broccolini pathogen and for known isolates of P. syringae pv. maculicola from crucifers. In host range testing, P. syringae pv. maculicolawas pathogenic to broccolini plants. The broccolini isolates and P. syringae pv. maculicola isolates had the same pathogenicity results when crucifers and tomatoes were tested as hosts; broccoli and cauliflower (B. oleracea var. botrytis) were infected, and tomato results were variable. These tests suggest that the broccolini pathogen is the bacterial leaf spot pathogen, Pseudomonas syringae pv. maculicola, that occurs on broccoli and cauliflower transplants (1). To our knowledge, this is the first report of this pathogen causing a disease on commercially grown broccolini. Reference: (1) S. T. Koike et al. Plant Dis. 82:727, 1998.

A postharvest discoloration of the cultivated mushroom Agaricus bisporus in Pennsylvania was associated with three pathotypes of fluorescent pseudomonads. Pathotype A strains caused pitted, dark-brown blotches on mushroom caps, formed precipitates in agar ('white line' reactions) with Pseudomonas tolaasii strain ATCC 14340 (reclassified as P. 'reactans'), were phenotypically like P. fluorescens biovar V, and fit descriptions of P. tolaasii. Pathotype B strains caused pitted, yellow- brown, sometimes slimy lesions on mushrooms, formed no 'white line' reactions, were phenotypically like P. fluorescens biovars III and V, and fit descriptions of P. 'gingeri'. Pathotype C strains caused mild, lightbrown discoloration on mushrooms with little tissue collapse, formed 'white line' reactions with P. tolaasii ATTC 33618 (type strain), had P. fluorescens biovar III and V phenotypes, and fit descriptions of P. 'reactans'. Isolations from mushroom casing material yielded all pathotypes including both pathogenic and nonpathogenic strains of P. 'reactans' with distinguishing phenotypic or chemical characteristics. Cellular fatty acid analysis suggested pathogenic strains of P. 'reactans' were more similar to P. tolaasii and P. 'gingeri' than to saprophytic strains of P. fluorescens, and nonpathogenic strains were more similar to saprophytic P. fluorescens than to P. tolaasii or P. 'gingeri'.

Strains of Xanthomonas campestris pv. vesicatoria were isolated from several tomato fields in Florida that differed from tomato race 1 (T1) strains commonly found in Florida. The strains produced a compatible reaction on tomato genotype Hawaii 7998 (H7998), were amylolytic and pectolytic, and were classified originally as T2 strains. However, these strains produced a rapid hypersensitive response when infiltrated into the tomato genotypes Hawaii 7981 (H7981), PI 126932, and PI 128216, whereas T2 strains produced a compatible reaction. In an experiment where electrolyte leakage was determined in leaflets of tomato cv. Bonny Best (compatible with all tomato strains), H7998 (resistant to T1 strains), and the two PIs, a member of these new strains induced a rapid hypersensitive response in the three tomato genotypes, whereas a T2 strain did not. After low concentrations of bacteria were infiltrated into the mesophyll of leaflets of PI 126932, PI 128216, H7998, and cv. Walter (compatible with all tomato strains), internal populations of the amylolytic, pectolytic Florida strain were reduced when tested in the first two genotypes but not in the latter two genotypes. Populations of the T1 strain were reduced only in H7998. These new strains are designated tomato race 3 (T3). When the T3 strains were compared with a representative group of T1 and T2 strains by fatty acid analysis and carbon substrate utilization patterns, the new T3 strains clustered distinctly from representative T1 and T2 strains. The evidence suggests the T3 strain is a recent introduction to Florida. An amylolytic, pectolytic strain isolated from seed grown in Thailand reacted similarly to the T3 strains on the tomato differentials. It also clustered with the T3 strains in the fatty acid and carbon substrate utilization dendrograms

Silver staining of sodium dodecyl sulfate-lysed cells of Xanthomonas campestris pv. vesicatoria electrophoretically separated in polyacrylamide gel revealed broad, dark gray bands in the low molecular weight region. The molecular weight of these bands was characteristic for each of the two major phenotypic groups identified in our X. c. vesicatoria collection. A 32- to 35-kDa band, designated a, was present in 192 of 197 tomato race 1 strains; whereas, a 25- to 27-kDa band, designated β, was present in all 55 strains of tomato race 2. Race 1 strains expressing an a band were unable to hydrolyze starch (Amy - ), and very few degraded pectate (Pec - ). In contrast, most race 2 strains were Amy + and Pec + [...]

Xanthomonas campestris pv. vesicatoria strains from a worldwide collection were assigned to the A or B group by testing for amylolytic activity and the presence of the α or β protein band. Cluster analyses of serological, carbon substrate utilization, and fatty acid composition data resulted in dendrograms with interspersed clusters of A and B strains, suggesting that the strain populations within each group are heterogeneous. However, further analysis of the data identified features unique to members of each group. Two monoclonal antibodies reacted only with group A strains, and two reacted only with group B strains. Reactivity patterns further subdivided each group into three serovars [...]

We report on the cloning of DNA involved in expression of two epitopes associated with lipopolysaccharide (LPS) in Xanthomonas campestris pv, vesicatoria and on the use of part of this region for differentiating A (nonpectolytic/amylolytic) and B strains (pectolytic/amylolytic) of this pathogen. From a genomic library of A-strain 75-3 that expresses two epitopes, two recombinant cosmids conferred expression of two epitopes in 87-13, an A strain that does not express the two epitopes. One of the two overlapping clones, pEC79S, contained a 27-kb insert and was used for further analysis. Immunoblots revealed that the epitopes are components of LPS in 75-3 [...]

Pathogenic and nonpathogenic strains of Agrobacterium tumefaciens (i.e., biovar 1), A. rhixogenes (i.e., biovar 2), A. vitis (i.e., biovar 3), and A. rubi were tested for their ability to utilize 95 different carbon sources available in the GN Microplate system and analyzed for fatty acid content using the MIDI gas-liquid chromatography system. Several carbon sources were identified as being of diagnostic value. With the exception of the A, rubi strain, hydroxy-L-proline and i-erythritol were exclusively metabolized by A. tumefaciens and A. rhizogenes, respectively. Analysis of fatty acid composition confirmed that cis-vaccenic acid (18:1 ω cis) is the predominant acid in all the Agrobacterium strains [...]

Two evaporation units have been constructed for preparation of metal multilayers using thermal and electron bombard sources. CuNi, CuV and CuFe multilayers have been produced with the explicit intention of correlating physical properties with structure as determined by Transmission Electron Microscopy (TEM). Low temperature resistivity and interdiffusion measurements have been performed upon a series of CuNi foils over the modulation wavelength range 1.6 nm to 10 nm. An anomalously high residual resistivity and interdiffusion coefficient were obtained for a modulation wavelength of 2.8 nm to 3.0 nm, the resistivity peak persisting after annealing of the foils for 100 hrs at 380°C even though the x-ray satellite reflections had vanished. TEM, however, indicated that interfacial defects were retained during this treatment. Annealing the foils at 480°C for three hours resulted in a loss of the anomalous resistivity peak, x-ray satellite reflections and interfacial structure.

When iron and vanadium films vaccum-deposited onto copper (111) surface were thicker than 10 and 15 nm, respectively, regular textural patterns were observed in their images of transmission electron microscopy (TEM). The textural patterns were composed of numerous rectangles like laths and showed remarkable contrast at defocussing conditions of TEM, similar to Fresnel contrast. The size of each rectangle composing texture changed with the film thickness and substrate temperature. The most remarkable textural pattern was observed in three-layer film, V/Fe/Cu, and a similar pattern was also observed in the carbon replica taken from its film surface. Therefore, the textural pattern reflects the surface microtopography of each film.

We have investigated the magnetic properties of semi-infinite systems of the ordered FeV in the CsCl structure. We use a self-consistent real-space tight-binding method in the unrestricted Hartree-Fock approximation to the Hubbard Hamiltonian. The magnetic moment at low-index surfaces (001) and (111) of perfectly ordered Fe 0.5 V 0.5 depends dramatically on the chemical component present at the surface. When Fe is at the surface, magnetic moments of 1.5μ B are obtained. The (110) structure contains both Fe and V and its magnetization is smaller.

Using a self-consistent tight-binding real-space model within the unrestricted Hartree-Fock approximation to the Hubbard Hamiltonian, we have investigated local polarisation at the low Miller-index surfaces of an FeCr (B2) alloy. In all cases, i.e. (001), (110) and (111), the local polarisation at the surface is found to be antiferromagnetically coupled with the subsurface layer, in contrast to the parallel coupling between Fe and Cr in bulk FeCr. This spin-flip configuration is directly related to surface effects, and means that the differences between recent in-situ magnetometer measurements and energy-resolved spin-polarised secondary-electron emission could be due to alloy formation at the FeCr interface.