bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of temperature and host genotype on the production of inoculum by Phytophthora fragariae var. fragariae from the roots of infected strawberry plants
Authors: DUNCAN J. M. , KENNEDY D. M.
Published: April 2007

A bioassay was used to monitor the release of inoculum in drainage water from strawberry plants inoculated with zoospores of Phytophthora fragariae var. fragariae. The fungus was detected in drainage water from plants that had been held at temperatures between 2 and 20 C. but not from plants held at 26°C. The lag phase before secondary inoculum was first released, the maximum and total amounts of inoculum released, and the length of time over which inoculum was released were all greater at the lower temperature regimes, especially those below 10 C. The results were consistent with observations on the effect of temperature on zoospore production from agar discs and on zoospore motility: more zoospores were produced at lower temperatures and they remained motile for longer. From this it is concluded that the inoculum detected consists mainly of motile zoospores. In most experiments with standardized suspensions c. 10‐15 were sufficient to initiate infection of the plants in the bioassay. In general, more inoculum was produced by host genotype/fungal isolate combinations in which there were marked root rot symptoms than in combinations in which the host was resistant.
Early stages of infection of rapeseed petals and leaves by Sclerotinia sclerotiorum revealed by scanning electron microscopy
Authors: JAMAUX I. , GELIE B. , LAMARQUE C.
Published: April 2007

The primary ascospore inoculum of Sclerotinia sclerotiorum initially infects rapeseed (Brassica napus var oleifera) via petals. Infected petals fall onto leaf surfaces, resulting in infection of those organs. A scanning electron microscopy (SEM) study of this process was undertaken to elucidate the host‐parasite relationship and to determine the best plant organ for detection by serology of early field infection as an aid to disease forecasting and cost‐effective disease control. The behaviour of ascospores deposited on young petals and on leaves was compared. Ascospores were deposited by inverting a mature apothecium above either a leaf disc, a young petal or young petal placed on a leaf surface. Spore germination, host penetration and colonization were examined by SEM. On young petals, the following steps in pathogenesis were observed: ascospore adhesion and germination, penetration of the host from short germ tubes and collapse of epidermal cells. Petals were then covered with extensive mycelium. From these sites, the mycelium invaded leaf tissues and infection proceeded. In contrast, ascospores landing directly on leaf surfaces failed to germinate. The role of petals as sites of pre‐election in the aetiology of the disease is discussed in relation to the published literature.
Quantitative relationships between Colletotrichum gloeosporioides infection of Stylosanthes scabra and weather under field conditions
Authors: CHAKRABORTY S. , BILLARD L.
Published: April 2007

In a field study over three successive years (1990‐92), quantitative relationships were established between infection by the anthracnose pathogen Colletotrichum gloeosporioides and weather. In order to detect successful spread and infection, groups of healthy seedlings of the tropical pasture legume Stylosanthes scabra were exposed to natural inoculum for 7 h (daytime), 17 h (overnight), 24 h and 48 h and then incubated in environments with different levels of relative humidity (r.h). Infection was generally associated with rainfall, hours r.h. >95% and mean hourly r.h. in the 1990 and 1992 seasons with average rainfall. Inoculum availability was an important determinant of the number of infections in the dry 1991 season. Quantitative relationships between infection and weather conditions for the exposure periods in the three seasons were established using multiple regression analysis. A regression equation containing hours of r.h. >95%, mean hourly r.h. and temperature was developed from a combined analysis of the 48‐h exposure data from 1990 and 1992. A parallelism test showed that the regression equation was equally applicable to infection data in each of the two years.
Inhibition of polyamine biosynthesis in Phytophthora infestans and Pythium ultimum
Authors: WALTERS D. R. , KEENAN J. P. , COWLEY T. , McPHERSON A. , HAVIS N. D.
Published: April 2007

Mycelial growth, polyamine concentrations and the activities of enzymes of polyamine biosynthesis and catabolism were examined in Phytophthora infestans and Pythium ultimum grown in the presence of difluoromethylornithine (DFMO), an inhibitor of omithine decarboxylase (ODC), and difluoro‐methylarginine (DFMA), an inhibitor of arginine decarboxylase (ADC). Growth of P. infestans was reduced by DFMO and a mixture of DFMO + DFMA, but was increased by DFMA at concentratiotis of 5 MM and greater, Polyamine concentrations and ODC activity were significantly reduced in P. infestans grown on all inhibitor treatments. In contrast, growth, polyamine concentrations and enzyme activities were not affected in P, ultimum exposed to the inhibitors.

It seems unlikely that P. infestans and P. uttimum possess ADC activity, as neither of the products of ADC activity (agmatine and putrescine) could be detected in ADC assays. Although ODC from P. infestans was sensitive to DFMO, ODC from P. uttimum was insensitive to the inhibitor. Moreover, uptake of DFMO by P. infestans was three times greater than that observed by P. ultimum.
Formation and survival of oospores of Phytophthora infestans under natural conditions
Authors: DRENTH A. , JANSSEN E. M. , GOVERS F
Published: April 2007

Phytophthora infestans is able to produce oospores in leaves of potato and tomato plants after inoculation with a mixture of Al and A2 mating‐type isolates. Various conditions for oospore formation were analysed. Under controlled conditions, oospores were produced in potato leaves at temperatures ranging from 5 to 25° C. In leaves of potato cultivar Bintje incubated at 15°C, oogonia and antheridia were observed 6 days after inoculation and thick‐walled oospores appeared 3‐4 days later. In field experiments oospores were found in leaves and stems of potato cultivars Bintje, Irene and Pimpernel and in leaves, stems and fruits of tomato cultivar Moneymaker within 2 weeks after inoculation. A bioassay was developed to test the survival of oospores in soil under various conditions. To determine whether late‐blight infections derived from infectious soil were caused by oospwres, DNA fingerprinting was performed. DNA fingerprint probe RG‐57 was suitable for distinguishing asexual progeny from recombinant progeny arising from soil‐borne oospores. We demonstrated survival of viable, infectious oospores of P. infestans in soil during the winter of 1992–93. Oospores were not infectious from soil exposed to temperatures of 40°C or higher but in the range 35°C to as low as – 80°C for 48 h, oospores survived.
Detection of resistance to Diaporthe toxica in asymptomatically infected lupin seedlings based on an immunoassay for phomopsin
Authors: WILLIAMSON P. M. , THAN K. A. , SIVASITHAMPARAM K. , COWLING W. A. , EDGAR J. A.
Published: April 2007

An immunoassay for the detection of phomopsin was used to detect levels of the mycotoxin in epidermal peels from resistant and susceptible lupin cultivars asymptomatically infected with Diaporthe toxica. Quantifiable levels (> 6,25μg/kg) of phomopsin were detected in susceptible lupin cultivars, but not in very resistant breeding lines or in the control. These differences reflect the differences in resistance observed in microscopical assays and mature plants in the field.
Genetics of specific resistance in pea (Pisum sativum) cultivars to seven races of Pseudomonas syringae pv. pisi
Authors: BEVAN J. R. , TAYLOR J. D. , CRUTE I. R. , HUNTER P J. , VIVIAN A.
Published: April 2007

Seven races of Pseudomonas syringae pv. pisi were distinguished using eight differential cultivars of pea (Pisum sativum). Segregation among F2 populations of crosses between differential cultivars sequentially inoculated with races of P.s. pv. pisi provided evidence for four and possibly six putative resistance(R)/avirulence(A) gene pairs. R1, R2 and R3 are dominant resistance alleles at single loci, R4 is a dominant allele at a single locus which exhibits variable expression possibly dependent on genetic background. There is evidence that R3 and R4 are at linked loci. Homology tests provided proof of the occurrence of the alleles R2, R3 and R4 in more than one cultivar. Two other alleles, R5 and R6, were postulated to explain the observed segregation ratios in certain crosses.

It can be inferred that P.s. pv. pisi races 2, 3 and 4 each carry a different single a virulence gene, race 6 carries no apparent avirulence genes, and race 7 carries at least A2, A3 and A4. Race 1 carries Al, A3, A4 and possibly A6; race 5 carries A2, A4 and possibly A5 and A6.
Ergot resistance in sorghum in relation to flowering, inoculation technique and disease development
Authors: MUSABYIMANA T. , SEHENE C. , BANDYOPADHYAY R.
Published: April 2007

Ergot is an important disease of sorghum (Sorghum bicolor) in parts of Africa and Asia. Studies were conducted to determine the relationship between flowering biology and ergot infection, and to develop an artificial field‐screening technique to identify ergot resistance in sorghum. Spikelets resisted infection after anthesis, but each day's delay in anthesis after inoculation supported 8‐3% more ergot. The screening technique consisted of three components: trimming of panicles to remove pollinated spikelets before inoculation, a single inoculation of trimmed panicles, and panicle bagging for 7‐10 days. Inoculated panicles were evaluated by a qualitative visual rating method (on a 1‐5 scale) and a quantitative spikelet counting method. Selected accessions from the world collection of sorghum germplasm were screened at Karama Research Station, Rwanda, for two seasons and 12 ergot‐resistant lines were identified. These were also resistant at ICRISAT Centre, India.
Soluble phenolic acids in Capsicum annuum stems infected with Phytophthora capsici
Authors: CANDELA M. E. , ALCÁZAR M. D. , ESPÍN A. , EGEA C. , ALMELA L.
Published: April 2007

The soluble phenolic acids of the stems of three Capsicum annuum cultivars associated with differing resistance to Phytophthora capsici showed qualitative and quantitative variation after inoculation, notably an increase in the total phenolic acid content in the resistant and intermediate varieties. The soluble phenolic acids also retarded myeelial growth of P. capsici in culture. The most pronounced inhibitory effect was produced by f‐cinnamic acid, followed by p‐hydroxybenzoic, vanillic and salicylic acids. Colonization and necrosis spread throughout the stem of the susceptible cultivar whereas the stem of the resistant cultivar was only partially invaded. In the latter, invasion of the tissue adjacent to necrosis occurred in only 20% of the plants.
Heat treatment of plant propagation material for the control of fire blight
Authors: KECK M. , CHARTIER R , ZISLAVSKY W. , LECOMTE P. , PAULIN J. P.
Published: April 2007

The thermal sensitivity of Erwinia amylovora was determined at 45° C and 50°C. In vitro assays with eight differetit strains showed that thermal death times did not exceed 70min at 45° C and 50min at 50° C (95% confidence interval). Heat treatments of naturally infected apple and pear shoots were performed using a moist and a dry heat procedure. When shoots were wrapped in wet cotton cloths (wet heat) and maintained in an incubator, no bacterial growth could be detected after an incubation of 5 h at 45° C. When shoots were sealed in polyethylene bags and immersed in water (dry heat), no Erwinia amytovora could be isolated after an immersion of 3 h at 45° C. Incubation at 50°C for 1 –2h in either condition did not eradicate the pathogen entirely. The failure rate of grafts using budwoods treated at the effective time‐temperature combinations did not exceed 25%.

The present investigations showed that the use of thermotherapy techniques for controlling Erwinia amylovora in propagation material of apple and pear might be possible.
Disease severity and yield of pure‐line wheat cultivars and mixtures in the presence of eyespot, yellow rust, and their combination
Authors: MUNDT C. C. , BROPHY L. S. , SCHMITT M. S.
Published: April 2007

Five winter wheat cultivars, six two‐component cultivar mixtures, and one four‐way mixture were grown in the presence of yellow rust, eyespot, both diseases, and neither disease for three seasons. On average, mixtures reduced the severity of yellow rust relative to their component pure stands by 53%. The four‐component mixture provided better yellow rust control than did the two‐way mixtures. Eyespot severity was reduced through mixing only in the absence of yellow rust and by only three of the seven mixtures (mean reduction = 13%). Yellow rust was 13% less severe in the presence of eyespot, and eyespot was 10% more severe in the presence of yellow rust. Averaged over all years, the mixtures increased yield relative to the pure stands by 6·2, 1·7, 7·1, and 1·3% in the presence of yellow rust, eyespot, both diseases, and neither disease, respectively. Two mixtures provided significant yield increases over the means of their component pure stands (7% and 9%) in the presence of eyespot even though one of them did not significantly reduce eyespot severity. Accounting for all disease treatments and years, four mixtures provided distinctly higher yield increases than the other three. In mixtures containing a resistant cultivar and a cultivar susceptible to eyespot, yield loss by the susceptible cultivar was not compensated for by increased yield of the resistant cultivar. The mixtures showed improved yield stability relative to the pure stands, with the four‐component mixture being particularly stable.
Decline of potato cyst nematodes, Globodera rostochiensis and G. pallida, in spring barley microplots
Authors: WHITEHEAD A. G.
Published: April 2007

In microplots of nine soils freed from volunteer potatoes and sown for four consecutive years with spring barley, the eggs of five populations of Globodera pallida and four populations of G. rostochiensis declined at annual rates of 12‐8‐40‐5%. One population of G. rostochiensis declined faster than other populations of either species, although average rates of decline did not differ significantly between the two species of Globodera. These results are compared with earlier research and their relevance to control of the nematodes by crop rotation is discussed.
Charcoal rot (Macrophomina phaseolina) resistance and the effects of water stress on disease development in sorghum
Authors: DIOURTE M. , STARR J. L. , JEGER M. J. , STACK J. P. , ROSENOW D. T.
Published: April 2007

In three field experiments, plants subjected to post‐flowering water stress and inoculated with Macrophomina phaseolina had greater development of charcoal rot symptoms than did inoculated plants not subjected to water stress. Two sorghum genotypes (B35‐6 and SC265‐14E) were found to be consistently more resistant to M. phaseolina, an assessment that was facilitated by the use of appropriate soil moisture conditions at the time of greatest plant susceptibility to charcoal rot.

In addition, an isolate of M. phaseolina originally isolated from a sorghum genotype with resistance to charcoal rot caused greater symptom development than did two other isolates originally obtained from sorghum genotypes susceptible to charcoal rot.
Identification and characterization of resistance to rhizomania in an ecotype of Beta vulgaris subsp. maritima
Authors: GEYL L. , HERIZ M. GARCIA , VALENTIN P. , HEHN A. , MERDINOGLU D.
Published: April 2007

An ecotype (S023) of Beta vulgaris subsp. maritima was identified which was highly resistant to beet necrotic yellow vein virus (BNYVV) but susceptible to its fungal vector, Polymyxa betae. A comparative study of viral development in the roots showed that the resistance was effective from the early stages of infection. Mechanical inoculation experiments suggested that the resistance was not due to a lack of transmission of BNYVV by its fungal vector. Immunogold‐silver labelling of the viral coat protein in root sections confirmed the existence of BNYVV transmission in the resistant ecotype. Virus replicated in isolated root protoplasts of both susceptible and resistant genotypes. Viral particles localized by immunogold‐silver labelling diffused over short distances from the primary infected root cells in both resistant and susceptible plants. Evidence for inhibition of long‐distance movement in the resistant ecotype requires further investigation.
A dynamic model simulating infection of apple leaves by Venturia inaequalis
Authors: XU X.‐M. , BUTT D. J. , VAN SANTEN G.
Published: April 2007

A new dynamic model of the infection of apple leaves by Venturia inaequalis is described. The model begins with the release of spores by rain and incorporates the effect of light on the discharge of ascospores from pseudothecia. The model then simulates infection through the sub‐processes of germination, appressorium formation and penetration, separately for ascospores and conidia landed concurrently on wet leaves. The rate of the infection process is determined using different equations for ascospores and conidia. Spore mortality when leaves dry is determined by the stage of infection and RH in the dry period. The infection process is driven by surface wetness, temperature and RH. The progress of each infection period is measured as infection efficiency (IE), namely the percentage of landed spores which have penetrated and thereby infected leaves. The final IE quantifies the favourability of weather in each infection period. In orchard tests in each of three years, the new model detected crucial infection periods in spring and early summer which accounted for outbreaks of leaf scab. These periods were not detected by a static model based on Mills’criteria. The models performed similarly in detecting infection periods later in summer.
Effect of Coniothyrium minitans on sclerotial survival and apothecial production of Sclerotinia sclerotiorum in field‐grown oilseed rape
Authors: McQUILKEN M. P. , MITCHELL S. J. , BUDGE S. P , WHIPPS J. M. , FENLON J. S. , ARCHER S. A.
Published: April 2007

In two field trials with oilseed rape, Coniothyrium minitans was applied to soil as a maizemeal‐perlite preparation in order to determine its effect on sclerotial survival and apothecial production of Sclerotinia selerotiorum. The mycoparasite infected sclerotia and decreased sclerotial survival, carpogenic germination and production of apothecia. Effects were greatest when inoculum of C. minitans was applied in autumn, at the time of sowing, rather than when it was applied in spring. C. minitans survived in soil for 2 years and spread to adjacent control plots and infected sclerotia within those plots. However, despite the fact that the inoculum potential of S. selerotiorum was reduced by C. minitans treatment, no disease control was obtained either in trial 1, where disease levels were low (0‐20% of plant stems affected), or in trial 2, where disease levels were high (up to 70% of plant stems affected). Possible reasons for this failure of C minitans to control sclerotinia disease in oilseed rape, and strategies to improve its efficacy in the field, are discussed.
Temporal and spatial aspects of the epidemiology of sorghum downy mildew on maize
Authors: HAU B. , DREPPER W. J. , PRASERTKIT O. , KRANZ J. , RENFRO B. L.
Published: April 2007

The development of systemic disease from primary inoculum sources of sorghum downy mildew was studied on field‐grown maize in Thailand. Data were recorded five times, from the first appearance of disease until 5 weeks after plant emergence. The incidence of diseased plants decreased with increasing distance from the primary inoculum sources, and the slope of the gradient flattened as the epidemic progressed. The steepest gradient of disease incidence was observed downwind. The progress in time and spread in space of disease about primary foci is described by three non‐linear models which fit the data equally well. However, the resulting gradients at wider distances are different. With two models the gradients decrease asymptotically to zero with increasing distance, whilst the other model leads to negative values above a certain distance. The rates of isopath movement of all models decrease with time, but the effect of distance on the isopathic rate is different; the rate can decrease, stay constant or increase with distance.
Transmission efficiency of three isolates of maize stripe tenuivirus in relation to virus titre in the planthopper vector
Authors: AMMAR E. D. , GINGERY† R. E. , MADDEN L. V.
Published: April 2007

Isolates of maize stripe tenuivirus (MSt V) from Florida (US), Costa Rica (CR), and Nigeria, Africa (AF), were transmitted to maize plants by the planthopper Peregrinus maidis (from Hawaii) with respective frequencies of 0,18, and 60% after a 1‐day acquisition access period on diseased plants, and with frequencies of 18, 71 and 93%, respectively, after a 7‐day access period. These isolates were transmitted transovarially to progeny planthoppers with respective frequencies of 21, 32, and 47%. The latent period in the vector, following oral acquisition of MSt V, was significantly longer in the US isolate than in the AF‐or CR isolates. ELISA tests of MSt V‐inoculative planthoppers indicated a significantly lower titre of MSt V‐US compared with MSt V‐CR or MSt V‐AF. These results suggest that, compared with the US isolate, the AF and CR isolates of MSt V multiply faster and reach higher levels in, and are transmitted more efficiently by, P. maidis from Hawaii.
Nature and genetic relatedness of the mycoplasma‐like organism causing rubus stunt in Europe
Authors: MÄURER R. , SEEMÜLLER E.
Published: April 2007

Cultivated red raspberries (Rubus idaeus), and wild blackberries (R fruticosus, R. caesius, and Rubus hybrids) showing symptoms of rubus stunt were collected in Germany, France, and Italy, Ribosomal DNA of the mycoplasma‐like organism (MLO) that causes rubus stunt was amplified by a polymerase chain reaction procedure and then digested with AtuI and RsaI restriction endonucleases. All samples examined showed the same restriction profiles, which were similar to those of the MLOs inducing elm yellows and alder yellows. However, the rubus stunt MLO could be distinguished from the elm and alder MLOs by Southern blot analysis using DNA probes from a strain of the elm yellows MLO, A variability of the hybridization profiles, probably caused by restriction fragment length polymorphisms, was observed among the rubus stunt samples. From both rDNA restriction site and Southern blot analyses it can be concluded that the rubus stunt agent and the elm yellows and alder yellows MLOs are not identical but closely related and can be grouped in the same taxonomic cluster.
Control of Verticillium wilt of cotton by means of soil solarization and tolerant cultivars in southern Spain
Authors: MELERO‐VARA J. M. , BLANCO‐LÓPEZ M. A. , BEJARANO‐ALCÁZAR J. , JIMÉNEZ‐DÍAZ R. M.
Published: April 2007

Eight field experiments (I‐VIII) were conducted in clay soils naturally infested with a cotton‐defoliating pathotype of Verticillium dahliae in the lower Guadalquivir Valley of Andalucia, southern Spain, during the period 1986‐90. Experiments I‐VI aimed to determine the efficacy of soil solarization in reducing populations of the pathogen in soil and eventually contributing to the control of Verticillium wilt of cotton. The population of V. dahliae in the 0‐to 40‐cm soil layer was reduced to undetectable or very low levels after solarization for 6 to 10 weeks. The final incidence of Verticillium wilt in the cotton crop following solarization was reduced to 13% or less in solarized plots, compared to 55–90·5% in unsolarized controls. The onset of disease incidence in the solarized plots was delayed by 2–7 weeks, increased at a lower rate, and had a smaller area under the disease progress curve, compared to that in unsolarized plots. Seed cotton yields in solarized plots increased by 11·3‐130·9% depending upon experiments, cultivars and years. Experiments VII and VIII aimed to determine the use of the highly wilt‐tolerant cotton cv. Acala GC 510 for control of the disease that had been cropped to susceptible cotton cultivars the year before in solarized soils. Solarized or unsolarized plots were first sown to susceptible cotton cvs Acala SJ2 and Coker 310, and the following year were sown to cv. Acala GC 510. The inoculum density of V. dahliae at the time of sowing cv. Acala GC 510 in previously solarized plots had increased to moderate levels, but remained considerably lower than that in unsolarized plots. The final disease incidence in cv. Acala GC 510 grown in unsolarized plots was lower than that in susceptible cultivars grown in the same plots the year before. Furthermore, the disease incidence in cv. Acala GC 510 grown in solarized plots was as high as that in susceptible cultivars grown the year before with much less initial inoculum.
The occurrence of carbendazim resistance in Rhynchosporium secalis on winter barley in England and Wales in 1992 and 1993
Authors: LOCKE T. , PHILLIPS A. N.
Published: April 2007

In 1992, samples of Rhynchosporium secalis from 19 winter barley crops in England and Wales were examined for carbendazim resistance. Of the 120 isolates obtained, 14·2% were resistant to carbendazim. A larger survey was carried out in England and Wales in 1993 when samples from 74 crops were examined. On this occasion 16·6% of the 639 isolates obtained were resistant to carbendazim, and resistant isolates were detected in 46% of crops.
Resistance to Polymyxa betae in wild Beta species
Authors: BARR K. J. , ASHER M. J. C. , LEWIS B. G.
Published: April 2007

Resistance to Polymyxa betae, the fungal vector of beet necrotic yellow vein virus, was studied in two wild beet species. Beta patellaris and B. procumbens. Plants grown in naturally infested soil or exposed to zoospore suspensions were examined in order to determine the stage in the life cycle of the fungus at which resistance was operating. Resting spores were never observed in the resistant species. Microscopic examination of stained transverse sections of fibrous roots taken at intervals after inoculation showed no evidence of even the earliest infection structures, the plasmodia; these were detected frequently in the epidermal cells of the susceptible Beta vulgaris. Use of the fluorescent stain DiOC6(3) to label zoospores showed that these were attracted to and attached themselves to the roots and root hairs of resistant species in the same way as to susceptible species. Maximum zoospore attachment was observed 1–6h after roots were exposed to zoospore suspensions. There was no obvious difference in the numbers attracted to resistant and susceptible hosts. Apparent infection of root hairs by encysted zoospores was observed in all three species. The resistance mechanism in the wild species must operate soon after this initial infection, possibly involving a hypersensitive response that prevents the subsequent development of plasmodia in epidermal cells.
Factors affecting the severity of bacterial canker of pear caused by Pseudomonas syringae pv. syringae
Authors: SPOTTS R. A. , CERVANTES L. A.
Published: April 2007

Several factors affecting the severity of bacterial canker of pear were studied. In the orchard, infection of shoots by Pseudomonas syringae pv. syringae occurred only when the inoculum dose exceeded 106 colony‐forming units/shoot. However, under favourable conditions in a growth chamber, cankers formed on detached shoots inoculated with 5 cfu/shoot. A second‐order polynomial relationship was established between log10 transformed canker length and log10 transformed inoculum dose. In orchard and growth chamber experiments, shoots were susceptible from the time of bud swell until after fruit harvest. The severity of Pseudomonas canker of detached shoots increased if they were frozen at – 10°C for 24 h before inoculation. Shoots were most susceptible when inoculated immediately after wounding, and no cankers developed in the orchard when 3‐day‐old wounds were inoculated. Additionally, no cankers resulted from inoculation of leaf scars at leaf drop. Actively growing, current‐season shoots were more susceptible than shoots that had set a terminal bud. The practical implications of these results are discussed as a basis for control of bacterial canker of pear.
Simulation studies on epidemics of wheat stripe rust (Puccinia striiformis) on slow‐rusting cultivars and analysis of effects of resistance components
Authors: LUO Y. , ZENG S. M.
Published: April 2007

Simulation studies were conducted to analyse the effects of components of slow‐rusting resistance to stripe rust (Puccinia striiformis) on wheat varieties using the Slow‐Rusting Epidemic Simulation Model (SRESM). Five components, infection efficiency (IE), sporulation capacity (SC), lesion expansion rate (LE), latent period (LP) and infectious period (IP) were studied for their importance in epidemics under various weather and pathogen inoculum conditions. Simulation outputs were analysed statistically. The LE, IE and SC were found to be the most important components. However, final disease was more strongly influenced by weather and initial disease. The Integrated Resistance Index (IRJ), which combines the effects of resistance components, was used to predict the effects of various combinations of components in different types of weather and at different levels of initial disease intensity. These predictions provide guidelines for plant breeders and are useful in selecting varieties for specific regions.
Variation in adult plant resistance to powdery mildew in spring oats under field and laboratory conditions
Authors: RODERICK H. W. , CLIFFORD B. C.
Published: April 2007

Ten oat genotypes were assessed for adult plant resistance (APR) to powdery mildew (Erysiphe graminis f.sp. avenae) in small field plots and on detached leaf segments in the laboratory using glasshouse‐grown plants. Significant genotype differences were observed in the field and on leaf segments for latent period, infection frequency and spore production, components used to assess APR. The genotype OM1711, which was selected because it expressed a higher level of mildew resistance than its most resistant parent, cv. Maldwyn, showed this transgressive resistance in both field and laboratory tests. By contrast, the genotype OM1387, also selected for high mildew resistance, only showed this enhancement in the field. It is concluded that quantitative assessment of mildew in detached leaves is not sufficiently precise to be used alone in selecting segregants for high levels of APR, and that field data are also needed.
Differentiation of Gaeumannomyces graminis from other turf‐grass fungi by amplification with primers from ribosomal internal transcribed spacers
Authors: GOODWIN P. H. , HSIANG T. , XUE B. G. , LIU H. W.
Published: April 2007

A region comprising the 5.8S RNA gene and internal transcribed spacers 1 and 2 of the take‐all patch fungus, Gaeumannomyces graminis var. avenae, was cloned and sequenced using primers from the flanking 17S and 26S ribosomal RNA genes. The sequenced region showed 99% similarity between the two G. graminis isolates, and 70–80% similarity between these two isolates and several other species of fungi. From the sequence, oligonucleotide primers were selected which permitted specific amplification of DNA from G. graminis vars. avenae and graminis using the polymerase chain reaction (PCR). The assay could detect DNA of G. graminis strains obtained from a wide variety of hosts, but did not amplify DNA from many other fungi, including the important turf‐grass root pathogens Magnaporthe poae and Leptosphaeria korrae. The primers also did not amplify DNA from G. graminis var. tritici, M. rhizophila or Phialophora graminicola. The PCR‐based assay shows promise as a diagnostic tool for the take‐all pathogen in turf‐grass pathology.
Mycoparasite‐like behaviour of the plant pathogen Pythium aphanidermatum in vitro
Authors: JONES E. E. , DEACON J. W.
Published: April 2007

Pythium aphanidermatum antagonized several other fungi after hyphal contact on films of water agar, recorded by video microscopy. It sometimes coiled round, penetrated and caused cytoplasmic coagulation of hyphae of the mycoparasites P. oligandrum, P. acanthophoron, P. mycoparasiticum and P. periplocum, but was not affected by them. It also coiled round, penetrated and coagulated P. ultimum, P. vexans, P. catenulatum, P. dissotocum and (infrequently) P. graminicola. It caused cytoplasmic coagulation of Fusarium oxysporum and Trichoderma aureoviride after contact, but without coiling. Six isolates of P. aphanidermatum behaved similarly, with a mode of action like that of the mycoparasite P. oligandrum but less rapid and consistent than this species. The results are discussed in relation to possible ecological roles of P. aphanidermatum.
Auxin, actin and growth of the Arabidopsis thaliana primary root
Authors: Rahman Abidur , Bannigan Alex , Sulaman Waheeda , Pechter Priit , Blancaflor Elison B. , Baskin Tobias I.
Published: April 2007

To understand how auxin regulates root growth, we quantified cell division and elemental elongation, and examined actin organization in the primary root of Arabidopsis thaliana. In treatments for 48 h that inhibited root elongation rate by 50%, we find that auxins and auxin‐transport inhibitors can be divided into two classes based on their effects on cell division, elongation and actin organization. Indole acetic acid (IAA), 1‐naphthalene acetic acid (NAA) and tri‐iodobenzoic acid (TIBA) inhibit root growth primarily through reducing the length of the growth zone rather than the maximal rate of elemental elongation and they do not reduce cell production rate. These three compounds have little effect on the extent of filamentous actin, as imaged in living cells or by chemical fixation and immuno‐cytochemistry, but tend to increase actin bundling. In contrast, 2,4‐dichlorophenoxy‐acetic acid (2,4‐D) and naphthylphthalamic acid (NPA) inhibit root growth primarily by reducing cell production rate. These compounds remove actin and slow down cytoplasmic streaming, but do not lead to mislocalization of the auxin‐efflux proteins, PIN1 or PIN2. The effects of 2,4‐D and NPA were mimicked by the actin inhibitor, latrunculin B. The effects of these compounds on actin were also elicited by a 2 h treatment at higher concentration but were not seen in two mutants, eir1‐1 and aux1‐7, with deficient auxin transport. Our results show that IAA regulates the size of the root elongation zone whereas 2,4‐D affects cell production and actin‐dependent processes; and, further, that elemental elongation and localization of PINs are appreciably independent of actin.
Cell division activity determines the magnitude of phosphate starvation responses in Arabidopsis
Authors: Lai Fan , Thacker Jennifer , Li Yuanyuan , Doerner Peter
Published: April 2007

Phosphate (Pi) is a major limiting factor for plant growth. Plants respond to limiting Pi supplies by inducing a suite of adaptive responses comprising altered growth behaviour, enhanced Pi acquisition and reduced Pi demand that together define a distinct physiological state. In Pi‐starved plants, continued root growth is required for Pi acquisition from new sources, yet meristem activity consumes Pi. Therefore, we analysed the relationship between organ growth, phosphate starvation‐responsive (PSR) gene expression and Pi content in Arabidopsis thaliana under growth‐promoting or inhibitory conditions. Induction of PSR gene expression after transfer of plants to Pi‐depleted conditions quantitatively reflects prior levels of Pi acquisition, and hence is sensitive to the balance of Pi supply and demand. When plants are Pi‐starved, enhanced root or shoot growth exacerbates, whereas growth inhibition suppresses, Pi starvation responses, suggesting that the magnitude of organ growth activity specifies the level of Pi demand. Inhibition of cell‐cycle activity, but not of cell expansion or cell growth, reduces Pi starvation‐responsive gene expression. Thus, the level of cell‐cycle activity specifies the magnitude of Pi demand in Pi‐starved plants. We propose that cell‐cycle activity is the ultimate arbiter for Pi demand in growing organs, and that other factors that influence levels of PSR gene expression do so by affecting growth through modulation of meristem activity.
Differential regulation of closely related R2R3‐MYB transcription factors controls flavonol accumulation in different parts of the Arabidopsis thaliana seedling
Authors: Stracke Ralf , Ishihara Hirofumi , Huep Gunnar , Barsch Aiko , Mehrtens Frank , Niehaus Karsten , Weisshaar Bernd
Published: April 2007

The genes MYB11, MYB12 and MYB111 share significant structural similarity and form subgroup 7 of the Arabidopsis thaliana R2R3‐MYB gene family. To determine the regulatory potential of these three transcription factors, we used a combination of genetic, functional genomics and metabolite analysis approaches. MYB11, MYB12 and MYB111 show a high degree of functional similarity and display very similar target gene specificity for several genes of flavonoid biosynthesis, including CHALCONE SYNTHASE, CHALCONE ISOMERASE, FLAVANONE 3‐HYDROXYLASE and FLAVONOL SYNTHASE1. Seedlings of the triple mutant myb11 myb12 myb111, which genetically lack a complete subgroup of R2R3‐MYB genes, do not form flavonols while the accumulation of anthocyanins is not affected. In developing seedlings, MYB11, MYB12 and MYB111 act in an additive manner due to their differential spatial activity; MYB12 controls flavonol biosynthesis mainly in the root, while MYB111 controls flavonol biosynthesis primarily in cotyledons. We identified and confirmed additional target genes of the R2R3‐MYB subgroup 7 factors, including the UDP‐glycosyltransferases UGT91A1 and UGT84A1, and we demonstrate that the accumulation of distinct and structurally identified flavonol glycosides in seedlings correlates with the expression domains of the different R2R3‐MYB factors. Therefore, we refer to these genes as PFG1–3 for ‘PRODUCTION OF FLAVONOL GLYCOSIDES’.
WRINKLED1 specifies the regulatory action of LEAFY COTYLEDON2 towards fatty acid metabolism during seed maturation in Arabidopsis
Authors: Baud Sébastien , Mendoza Monica Santos , To Alexandra , Harscoët Erwana , Lepiniec Loïc , Dubreucq Bertrand
Published: April 2007

The WRINKLED1 (WRI1) transcription factor has been shown to play a role of the utmost importance during oil accumulation in maturing seeds of Arabidopsis thaliana. However, little is known about the regulatory processes involved. In this paper, comprehensive functional analyses of three new mutants corresponding to null alleles of wri1 confirm that the induction of WRI1 is a prerequisite for fatty acid synthesis and is important for normal embryo development. The strong expression of WRI1 specifically detected at the onset of the maturation phase in oil‐accumulating tissues of A. thaliana seeds is fully consistent with this function. Complementation experiments carried out with various seed‐specific promoters emphasized the importance of a tight regulation of WRI1 expression for proper oil accumulation, raising the question of the factors controlling WRI1 transcription. Interestingly, molecular and genetic analyses using an inducible system demonstrated that WRI1 is a target of LEAFY COTYLEDON2 and is necessary for the regulatory action of LEC2 towards fatty acid metabolism. In addition to this, quantitative RT‐PCR experiments suggested that several genes encoding enzymes of late glycolysis, the fatty acid synthesis pathway, and the biotin and lipoic acid biosynthetic pathways are targets of WRI1. Taken together, these results indicate new relationships in the regulatory model for the control of oil synthesis in maturing A. thaliana seeds. In addition, they exemplify how metabolic and developmental processes affecting the developing embryo can be coordinated at the molecular level.
Prevalence and correlates of burden among caregivers of patients with bipolar disorder enrolled in the Systematic Treatment Enhancement Program for Bipolar Disorder
Authors: Perlick Deborah A , Rosenheck Robert A , Miklowitz David J , Chessick Cheryl , Wolff Nancy , Kaczynski Richard , Ostacher Michael , Patel Jayendra , Desai Rani ,   the STEP‐BD Family Experience Collaborative Study Group
Published: April 2007

Objectives: Caring for a relative with schizophrenia or dementia is associated with reports of high caregiver burden, symptoms of depression, poor physical health, negligence of the caregiver's own health needs, elevated health service use, low use of social supports, and financial strain. This study presents the design and preliminary data on the costs and consequences of caring for a relative or friend with bipolar disorder from the Family Experience Study, a longitudinal study of the primary caregivers to 500 patients enrolled in the Systematic Treatment Enhancement Program for Bipolar Disorder.

Methods: Subjects were primary caregivers of 500 patients with bipolar disorder diagnosed by the Mini International Neuropsychiatric Interview and the Affective Disorder Evaluation. Caregivers were evaluated within 1 month after patients entered Systematic Treatment Enhancement Program using measures of burden, coping, health/mental health, and use of resources and costs.

Results: Eighty‐nine percent, 52%, and 61% of caregivers, respectively, experienced moderate or higher burden in relation to patient problem behaviors, role dysfunction, or disruption of household routine. High burden caregivers reported more physical health problems, depressive symptoms, health risk behavior and health service use, and less social support than less burden caregivers. They also provided more financial support to their bipolar relative.

Conclusions: Burdens experienced by family caregivers of people with bipolar disorder are associated with problems in health, mental health, and cost. Psychosocial interventions targeting the strains of caregiving for a patient with bipolar disorder are needed.
The spectrum of substance abuse in bipolar disorder: reasons for use, sensation seeking and substance sensitivity
Authors: Bizzarri Jacopo V , Sbrana Alfredo , Rucci Paola , Ravani Laura , Massei Guido Jacopo , Gonnelli Chiara , Spagnolli Sabrina , Doria Maria Rosa , Raimondi Federica , Endicott Jean , Dell'Osso Liliana , Cassano Giovanni Battista
Published: April 2007

Objectives:  To examine the spectrum of alcohol and substance abuse, including reasons for use, in patients with bipolar I disorder, compared with patients with substance use disorder and healthy controls, with a specific focus on the relationship between substance use, substance sensitivity, other comorbid psychiatric symptoms and traits related to sensation seeking.

Methods:  This study included 104 patients with bipolar I disorder (BPD I), of whom 57 (54.8%) met DSM‐IV criteria for lifetime alcohol or substance use disorder (BPD + SUD), 35 patients with substance use disorder (SUD) and no psychiatric disorder and 50 healthy controls. Assessments included the Structured Clinical Interview for DSM‐IV Axis I Disorders (SCID) and the Structured Clinical Interview for the Spectrum of Substance Use (SCI‐SUBS).

Results:  Patients with BPD + SUD and SUD had significantly higher scores on the SCI‐SUBS domains of self‐medication, substance sensitivity and sensation seeking compared with patients with BPD and healthy controls. Reasons for substance use did not differ between patients with BPD + SUD and patients with SUD. Those most frequently cited were: improving mood; relieving tension; alleviating boredom; achieving/maintaining euphoria; and increasing energy.

Conclusions:  Recourse to substances is associated with increased mood and anxiety symptoms, substance sensitivity, and sensation seeking among patients with BPD + SUD and SUD. Substance sensitivity and sensation seeking traits should be investigated in all patients with BPD as possible factors associated with a development of SUD, in order to warn patients of the specific risks related to improper use of medications and substances.
Specificity of mood stabilizer action on neuronal growth cones
Authors: Shaltiel Galit , Dalton Emma C , Belmaker Robert H , Harwood Adrian J , Agam Galila
Published: April 2007

Objectives: Lithium, valproic acid (VPA) and carbamazepine (CBZ) are commonly used mood stabilizers, but their therapeutic mechanism is unclear. These drugs all cause the same morphological effects on postnatal rat neuronal dorsal root ganglia (DRG) growth cones via an inositol‐reversible mechanism. However, due to limitations in earlier analysis, the effects of combining drugs, drug specificity and inositol stereoisomer specificity are unknown. We devised an improved analytical method to address these issues.

Methods: Dorsal root ganglia explants were cultured individually and incubated with combinations of psychotropic drugs and inositol stereoisomers. We recorded axonal growth cone morphology and calculated growth cone area per a modified method described by Williams et al. (Nature2002;417: 292–295). Statistically significant changes in area were calculated using non‐parametric statistical testing.

Results: (i) Lithium and VPA showed an additive effect on growth cone spreading. (ii) Among eight additional psychotropic drugs to those previously tested, only imipramine and chlorpromazine altered DRG growth cone morphology. As this effect was not reversed bymyo‐inositol, it arises from a different mechanism to the mood stabilizers lithium, VPA and CBZ. (iii)Myo‐inositol, but notscyllo‐ orepi‐inositol, causes a significant reversal of the lithium effect on the growth cones spreading, consistent with the inositol depletion hypothesis.

Conclusions: These results show that lithium, VPA and CBZ are unique in causing altered neuronal morphology viamyo‐inositol depletion.
The occurrence of cavum septi pellucidi enlargement is increased in bipolar disorder patients
Authors: Kim Minue J , Lyoo In Kyoon , Dager Stephen R , Friedman Seth D , Chey Jeanyung , Hwang Jaeuk , Lee Yu‐Jin , Dunner David L , Renshaw Perry F
Published: April 2007

Objectives:  This study was conducted to evaluate the prevalence of cavum septi pellucidi (CSP) enlargement in patients with bipolar disorder (BD) and healthy comparison subjects.

Methods:  The occurrence of enlarged CSP in patients with BD (n = 41, age 35.4 ± 10.8 years) and healthy volunteers (n = 41, age 35.3 ± 10.0 years) was studied using magnetic resonance imaging. The length of the CSP was measured by counting the number of consecutive resliced coronal 0.5‐mm images in which the CSP was present. A CSP length ≥ 6 mm was a priori defined as abnormal enlargement of the CSP.

Results:  Bipolar subjects exhibited a significantly higher prevalence of abnormal CSP enlargement (8 of 41 subjects, 19.5%) than healthy comparison subjects (1 of 41 subjects, 2.4%) (logistic regression analysis: Wald statistic = 5.07, df = 1, p = 0.024). The prevalence of abnormally enlarged CSP was not significantly different between drug‐naïve and drug‐exposed bipolar subjects or when comparing bipolar I and II sub‐diagnoses. Bipolar subjects with abnormal CSP enlargement had a significantly earlier onset of BD than those without (14.3 ± 3.6 versus 20.1 ± 7.4 years, respectively).

Conclusions:  The current study is the first to report an increased prevalence of abnormally enlarged CSP in a well‐characterized bipolar population. Our finding that an abnormal enlargement of CSP, a neurodevelopmental abnormality, is associated with early onset of illness implicates early maturational processes as contributing to BD.