bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk factors for the recurrence of premature rupture of the membranes
Authors: Doody David , Patterson Matthew , Voigt Lynda , Mueller Beth
Published: November 2003

Premature rupture of the amniotic membranes (PROM) occurs in up to 20% of all births. Although many studies have examined risk factors for PROM and, in particular, preterm PROM (PPROM, if less than 37 weeks’ gestation), the aetiology of PROM recurrence has not been examined as closely. This study investigated factors that may increase the risk of PROM among women who have already experienced one PROM birth. Maternally linked Washington State birth certificates from 1984 to 1993 identified 208 women with consecutive PROM births. Controls were a random sample (n= 848) of women who had one birth on record complicated by PROM, but whose subsequent birth was not. Among women with a prior term PROM, increased risk for PROM recurrence (term PROM or PPROM) was associated with an intervening fetal death at less than 20 weeks' gestation (OR = 2.4, 1.3–4.5) and with parity of two or more (OR = 2.0, 1.3–3.4). None of the factors assessed significantly increased the risk of recurrence of PROM (term PROM or PPROM) among women with a prior PPROM. Other potential risk factors for PROM recurrence were evaluated within the two PROM groups (PPROM or term PROM at first birth) by stratifying among the cases according to gestational length at subsequent birth.
Factors associated with repetition of low birthweight: Missouri longitudinal study
Authors: Bakewell Janice , Stockbauer Joseph , Schramm Wayne
Published: November 2003

The tendency to repeat low birthweight (LBW < 2500 g) was studied in 182 285 linked first and second birth Missouri livebirths for 1978–90, of which 10 701 had first birth LBW. We examined the likelihood of LBW repetition by first birth birthweight, preterm delivery, and small‐for‐gestational‐age (SGA) status by race, and the odd ratios (ORs) of repeat LBW for risk factors such as smoking, in comparison with ORs of second birth LBW among women with normal‐weight first births. We found a strong tendency to repeat LBW (21%), especially following more extreme LBW first births. Adjusted ORs for repeat LBW were 10.1 for births that were preterm and SGA; 7.9 for preterm non‐SGA; and 6.3 for SGA term births. Significant ORs of LBW repetition were found for smoking (1.52 and 1.85 for smoking in second pregnancy only and both pregnancies, respectively), short interpregnancy interval (1.33), and advanced maternal age (1.17), but the ORs were generally lower than those for women with normal‐weight first births. Low pre‐pregnancy weight was a significant risk factor for LBW repetition.
The relationship of interpregnancy interval to infant birthweight and length of gestation among low‐risk women, Georgia
Authors: Adams Melissa , Delaney Kristin , Stupp Paul , McCarthy Brian , Rawlings James
Published: November 2003

To examine the association between interpregnancy interval and low birthweight (< 2500 g), preterm delivery (< 37 weeks’ gestation), and inadequate fetal growth, we studied a population‐based sample of 23 388 white and 4885 black women at low risk for adverse pregnancy outcomes who delivered their first and second infants in Georgia from 1980 to 1992. We used fetal death and livebirth certificates. The interpregnancy interval was the time from delivery to the woman’s next conception. For each pregnancy outcome, we stratified by race and used logistic regression to assess the association between interpregnancy interval and outcome, while controlling for confounders. Intervals <6 months were observed for 3.7% of white women and 7.0% of black women and intervals 48 months were seen for 16.8% of white women and 24.8% of black women. Results from logistic regression showed that, for both races, interpregnancy interval was associated with low birth‐weight and preterm delivery. Nearly all of the increased risk occurred in intervals < 6 months or 48 months. The magnitude of the increase in risk associated with these intervals ranged from modest to moderate and was similar for black and white women. Because short interpregnancy intervals are rare and are weak risk factors among low‐risk women, efforts to lengthen interpregnancy intervals are unlikely to reduce substantially their rates of adverse pregnancy outcomes.
Attempt and success rates for vaginal birth after Caesarean section in relation to complications of the previous pregnancy
Authors: Holt Victoria , Mueller Beth
Published: November 2003

The relationships between prior obstetrical complications and subsequent trial of labour and vaginal birth after Caesarean (VBAC) success likelihood were examined among a cohort of Washington State women with a first livebirth via Caesarean delivery and a second livebirth between 1987 and 1993 (n equals; 10 110). Overall, 64% of the cohort undertook a labour trial, and 62% of those who attempted VBAC delivery were successful, for an overall VBAC rate of 40%. Women with fetal macrosomia, cephalopelvic disproportion, prolonged labour, diabetes, or placental problems in the first pregnancy were less likely to undergo a labour trial in the second pregnancy than those without these factors, while women with prior induced labour, genital herpes, fetal distress, or breech presentation were more likely to attempt vaginal birth. Approximately half of women with prior macrosomia, labour problems, or chronic medical conditions who attempted VBAC succeeded, as did three‐quarters of women with prior breech presentation or placental conditions. Overall VBAC rates were around 33% for women with previous fetal macrosomia, labour problems, or chronic medical conditions, and 45–55% among those with herpes, fetal distress or breech presentation at the first birth. Trial of labour should especially be encouraged among women without prior labour problems.
The influence of maternal nutritional factors on intrauterine growth retardation in Brazil
Authors: Rondó Patricia H.C. , Abbott Rebecca , Rodrigues Laura C. , Tomkins Andrew M.
Published: November 2003

A case–control study of 712 Brazilian mother–baby pairs was performed to assess maternal nutritional factors, more specifically low or marginal concentrations of vitamin A, folate and iron, as risk factors for intrauterine growth retardation (IUGR). Newborns were classified as being IUGR according to the Lubchenco classification. The gestational age of the newborns was evaluated by the Capurro method. Vitamin A, folate, ferritin and haemoglobin were measured by high‐performance liquid chromatography, radioimmunoassay, immunoenzymetric assay and by the cyanmethaemoglobin method respectively. The relationship between maternal nutritional status and IUGR was investigated using stratification and logistic regression. According to the final logistic regression model, the risk factors for IUGR were: maternal body weight, per capita income, cigarette smoking, maternal weight gain, prior history of low birthweight, high maternal ferritin, beer intake and coffee intake. Specific interventions likely to have the major short‐term impact in this region are not directly related to nutritional factors, but to efforts to reduce or eliminate toxic exposures. Over the long term, improvement in maternal nutritional status and socioeconomic conditions would be expected to produce important benefits.
Pea early‐browning tobravirus
Authors: BOULTON R. E.
Published: November 2003

A disease of pea caused by pea early‐browning virus was first described in the Netherlands, and shortly afterwards was reported from England. The virus has since been reported from several other European countries, and also from North Africa. It can systemically infect crop legume species and the disease is locally important in pea in the Netherlands and England. The virus, a member of the Tobravirus genus, is transmitted through sandy or light‐textured soils by species of trichodorid nematodes, and also through seed of pea and faba bean. Seed transmission is the most probable means of virus spread, especially over long distances, to previously uninfested soils. Aspects of the disease including symptoms, soil and seed transmission, detection, resistance and control, and characteristics of the pathogen, are reviewed.
Effects of abiotic variables on the response of carnation cultivars to Fusarium oxysporum f.sp. dianthi
Authors: BEN‐YEPHET Y. , REUVEN M. , ZVEIBIL A. , SHTIENBERG D.
Published: November 2003

The effects of abiotic variables on the response of carnation cultivars to Fusarium oxysporum f.sp. dianthi (F.o. dianthi ) were examined in experiments conducted under semi‐controlled environments. The abiotic variables examined were solar radiation intensity, temperature and growth substrate. Temperature was not controlled, but differed markedly among experiments, thus, its effect was not determined quantitatively. Disease incidence and disease severity varied significantly among the experiments (due mainly to differences in temperature), among the solar radiation treatments and among the cultivars tested. The three‐way interaction term (i.e. cultivar × shade treatment × experiment) was highly significant (P < 0.001) when both disease incidence and disease severity were considered, indicating that no single variable was predominant in determining disease intensity. The effects of the growth substrate on disease progress was examined in plants grown in tuff or in tuff mixed with peat (1 : 1 and 1 : 3) substrates. The growth substrate had a potent effect on disease development in the less susceptible cultivars. Severe epidemics developed in all cultivars when they were grown in the tuff/peat mixture, although some were resistant when grown in tuff alone. These results led to the conclusion that the carnation response to F.o. dianthi is substantially influenced by the environmental conditions of the test.
The occurrence of Mycosphaerella graminicola, teleomorph of Septoria tritici in France
Authors: HALAMA P.
Published: November 2003

Pseudothecia of Mycosphaerella graminicola, the teleomorph of Septoria tritici, were observed on wheat debris in France for the first time during autumn 1994. The colonies and conidia, derived from ascospores isolated by micromanipulation, conform to previously published data.
Isozyme and RAPD‐PCR analyses of Fusarium avenaceum strains from Finland
Authors: YLI‐MATTILA T. , PAAVANEN S. , HANNUKKALA A. , PARIKKA P. , TAHVONEN R. , KARJALAINEN R.
Published: November 2003

Differences in isozyme and RAPD‐PCR polymorphisms amongst 33 isolates of Fusarium avenaceum were compared using native polyacrylamide gel electrophoresis and agarose gel electrophoresis. The isolates were collected from different regions of Finland. Amongst eight enzymes analysed clear isozyme polymorphism was detected in five enzymes which could be grouped into 20 different electrophoretic phenotypes and three main groups at the similarity level of 70% in unweighted pair group method with arithmetic average (UPGMA) analysis. RAPD‐PCR analysis differentiated all F. avenaceum strains from each other. The phenotypes resulting from RAPD‐PCR analysis were grouped into five main groups by UPGMA analysis at the similarity level of 55%. These main groups had several similarities with the main groups from isozyme analysis. RAPD‐PCR patterns of 16 isolates of Fusarium graminearumF. culmorumF. equisetiF. oxysporum and F. redolens were also studied and strains from each Fusarium species formed individual groups in UPGMA and principal components analyses. Thus, the extent of isozyme and RAPD‐PCR polymorphisms found in Fusarium strains potentially provides a method for identifying the fungi both at strain and species level.
Characterization of a strain of clover yellow vein potyvirus infecting borage (Borago officinalis L.) in Spain
Authors: LUIS‐ARTEAGA MARISOL , GARCÍA‐ARENAL FERNANDO , RODRÍGUEZ‐CEREZO EMILIO
Published: November 2003

A disease of borage (Borago officinalis) in Spain, characterized by severe mosaic and deformation of the leaves, was shown to be caused by a potyvirus. The borage‐infecting potyvirus was characterized biologically by the symptoms induced in 23 indicator species and was shown to be transmitted experimentally by the aphid Myzus persicae in a non‐persistent manner. In order to classify the borage‐infecting potyvirus we have cloned and sequenced the entire coat protein gene and 3′ non‐coding region of the viral RNA. By comparing this nucleotide sequence with those of other members of the Potyviridae, we can identify the Spanish borage‐infecting potyvirus as an isolate of clover yellow vein virus (CYVV), a virus so far only known to cause important diseases in forage legumes. This is the first record of CYVV in Spain and of CYVV infecting a natural host of the Boraginaceae.
Effects of the fungus Crinipellis perniciosa, causal agent of witches' broom disease, on cell and tissue cultures of cocoa (Theobroma cacao L.)
Authors: MUSE RADZALI B. , COLLIN HAMISH A. , ISAAC SUSAN , HARDWICK KEITH
Published: November 2003

The symptoms of witches' broom disease in cocoa, caused by the Basidiomycete fungus Crinipellis perniciosa, are pronounced swelling of the terminal and axillary buds followed in the long term by necrosis of this tissue. The direct effect of C. perniciosa on cocoa cells was examined under controlled conditions by growing primary and secondary phase cultures of the fungus separately and also with callus cultures and with cell suspensions. Both primary and secondary phase mycelium reduced growth of callus cultures by about 47% after one week compared with the controls. However, cell suspensions containing primary phase mycelium showed initial growth double that of the uninfected controls after 5 days, but then growth was reduced below that of the control and particularly when the primary phase became secondary phase mycelium. This change in fungal development coincided with the time that the cell culture reached the stationary growth stage. Cell cultures inoculated with stationary phase mycelium showed the same growth as the control after 5 days but then growth was reduced to 50% of the control after 19 days incubation and remained at this low level subsequently. The inhibitory effect of secondary phase mycelium was examined by incubating callus and cell suspensions with culture filtrate from liquid cultures of the secondary phase. Inclusion of 50% by volume of culture filtrate from the secondary phase in the growth medium for callus and cell suspensions, respectively, resulted in a reduction in growth of the plant tissue cultures. Addition of fungal culture filtrates also led to loss in potassium and loss of viability of cell suspensions and of isolated cells as represented by protoplasts. The necrotrophic mode of the secondary phase may be achieved through the production of phytotoxins acting on the host cell membrane.
Nature of resistance of seven melon lines to Sphaerotheca fuliginea
Authors: FLORIS E. , ALVAREZ J. M.
Published: November 2003

The nature of resistance of Sphaerotheca fuliginea Poll. race 1 was investigated in leaves of susceptible, moderately resistant and resistant genotypes of Cucumis melo. For this purpose three different tests were carried out. The first one was designed to assess whether resistance was caused by pre‐ or post‐infectional mechanisms, and the other two tests were focused to determine if any differences were present in the progression ratio of the disease, measured as the delaying time in conidiophore and conidia formation, among the different cultivars which were tested. The results showed that in the resistant controls (‘PMR5’ and ‘PI 124111’), the resistant reaction was probably due to pre‐infectional mechanisms, or at least very near to the moment of infection, while in the moderately resistant and resistant Spanish local cultivars it was clearly due to post‐infectional mechanisms characterized by an important delay in the growth and development of the fungus when compared with the susceptible cultivars. Suggestions are made for the development of more successful breeding programmes.
The early development of Erysiphe pisi on Pisum sativum L.
Authors: SMITH P. H. , FOSTER E. M. , BOYD L. A. , BROWN J. K. M.
Published: November 2003

Erysiphe pisi, the powdery mildew pathogen of Pisum sativum, followed a developmental sequence that allowed the identification of 10 distinct growth stages (GS) over 30 h following inoculation. The growth stages were ungerminated conidia (GS1), germinated conidia, having produced a germ tube (GS2), germlings where the germ tube had forked (GS3), germlings with a multi‐lobed germ tube (GS4), germlings with a single hypha (GS5), germlings with two (GS6 and 7) or three (GS8 and 9) hyphae, one of which may have formed from the appressorium (GS7 and 9), and germlings with abnormally long germ tubes (GS10), which did not develop hyphae. Conidia germinated rapidly, with a quarter of conidia producing germ tubes by 2 h after inoculation (hai). Most germlings produced multi‐lobed appressoria, which showed considerable variation in structure. Haustoria, although often difficult to visualize, were first seen 4 hai, and the first hyphae 14 hai, growing from the body of the conidium. Subsequent hyphae developed from both the body of the conidium and from the appressorium.
The effect of temperature on hatching and penetration of chickpea roots by Pratylenchus thornei
Authors: CASTILLO P. , TRAPERO‐CASAS J. L. , JIMENEZ‐DIAZ R. M.
Published: November 2003

Egg hatch of Pratylenchus thornei was influenced by temperature. It took place at all temperatures within the range 10–25°C and was optimal at 20°C. Root penetration increased steadily with increasing time of incubation up to the end of the experiment 11 days after inoculation. Temperature affected penetration rate in chickpea (Cicer arietinum) cultivars UC 27 and JG 62 but not in line P 2245, being significantly higher at 20–25°C than that at 15°C. At the end of the experiment, roots of line P 2245 held at 15°C contained more P. thornei than cultivars UC 27 and JG 62. No difference in percentage penetration among host genotypes was observed at 20 or 25°C. All migratory stages of P. thornei penetrated roots of chickpea from the first to 11th days after inoculation.
Fitting and testing spatio‐temporal stochastic models with application in plant epidemiology
Authors: GIBSON G. J. , AUSTIN E. J.
Published: November 2003

We propose and illustrate a likelihood‐based method for fitting spatio‐temporal stochastic models for the spread of a plant disease to experimental observations. The models considered are individual‐based, with members of the population occupying discrete sites on a two‐dimensional lattice. The disease is assumed to be characterized by presence/absence, and infection of susceptible individuals by infected individuals is represented as a stochastic process. The method described can be applied to estimate parameters in models of this kind when observations consisting of temporal sequences of disease maps are available. The use of measures of spatial aggregation as measured from simulated and real epidemics is proposed as a means of assessing the relative merits of alternative models for the spread of a disease. To illustrate the technique we fit and compare two models, which differ in the relationship between infective pressure and distance, to observations of an epidemic of citrus tristeza virus (CTV). It is demonstrated that a model in which this relationship is a power‐law is superior to one which uses a negative exponential and the importance of model choice for the design of control strategies is discussed briefly.
RAPID SEROLOGICAL DETECTION OF TOMATO SPOTTED WILT VIRUS IN INDIVIDUAL THRIPS BY SQUASH‐BLOT ASSAY FOR USE IN EPIDEMIOLOGICAL STUDIES
Authors: ARAMBURU J. , RIUDAVETS J. , ARNO J. , LAVIÑA A. , MORIONES E.
Published: November 2003

Squash blotting on nitrocellulose membranes was used to detect tomato spotted wilt virus (TSWV) in individual Frankliniella occidentalis adult thrips using a specific polyclonal antiserum. This method offers a simple and reliable procedure to test a large number of thrips and was less time‐consuming than alternative techniques available. A 95% agreement was found between the results of squash‐blot and plant transmission assay. Based on this agreement, this technique was used to study the relative number of viruliferous thrips in F. occidentalis field populations collected from a farm in Catalonia where TSWV causes important economic losses. The percentages of viruliferous individuals detected from a total of 1509 collected thrips increased from 0% to 2% in the different surveys conducted in the 1993 growing season. Squash‐blot proved to be a rapid and inexpensive technique to screen TSWV viruliferous thrips from field populations. The results obtained by this method could be used together with other epidemiological data to forecast TSWV‐induced diseases.
Effect of genotype unit number and spatial arrangement on severity of yellow rust in wheat cultivar mixtures
Authors: MUNDT C. C. , BROPHY L. S. , KOLAR S. C.
Published: November 2003

Pure stands of a yellow rust‐susceptible wheat cultivar, pure stands of a resistant cultivar, and a 1 : 1 random mixture of resistant and susceptible cultivars were compared to populations in which strips or hills of the cultivars were alternated to attain genotype units (units of the same host genotype) that were larger in area than that of a single wheat plant. These four host populations were grown in plots of different sizes in order also to alter the number of units per host population. The goal was to determine if increasing the number of genotype units in mixed populations of large genotype units improved disease control relative to pure‐line populations by increasing the amount of inoculum exchange among genotype units. Random mixtures of the two cultivars always provided better disease control than did alternating strips or hills. Evidence for an effect of genotype unit number on the efficacy of mixtures for rust control was found in only one of three experiments. Random mixtures of the two cultivars increased grain yield relative to the pure stand mean, but alternating strips did not.
Inoculum density and spatial pattern of Rhizoctonia solani in field plots of Solanum tuberosum: effects of cropping frequency
Authors: GILLIGAN C. A. , SIMONS S. A. , HIDE G.A.
Published: November 2003

Bait plants, comprising micropropagated and commercial seed tubers, were used to estimate the effects of rotation on the density and spatial pattern of inoculum of Rhizoctonia solani in large field plots of potatoes. Soilborne inoculum of R. solani produced economically significant levels of stem canker and its incidence and severity varied with rotation, with most disease in 2‐year and less in 4‐ and 6‐year rotations. The rates of loss of inoculum during intercrop periods differed amongst rotations with a rapid fall to low levels occurring after 1 year in a 6‐year rotation and after 2 years in a 4‐year rotation. Replenishment of inoculum to soil was rapid following the growth of a susceptible crop, with comparatively high levels of infection and disease, even in long rotations. Disease occurred in patches and the size of patches and the density of R. solani within patches differed with cropping frequency. The degree of spatial autocorrelation also differed amongst rotations but there was no evidence for any significant differences in the rate of change of spatial autocorrelation during intercrop periods in the three rotations.
Development of a PCR assay to detect Fusarium poae in wheat
Authors: PARRY D. W. , NICHOLSON P.
Published: November 2003

Random amplified polymorphic DNA assays were carried out on a range of isolates of F. poae to identify markers common to all isolates. Two fragments were isolated, cloned and used to probe Southern blots of DNA from F. poae and isolates from a range of wheat seed and stem base pathogens. One fragment, which hybridized preferentially to DNA of F. poae was partially sequenced and two pairs of primers (Fp8 F/R and Fp82 F/R) were generated for use in the polymerase chain reaction (PCR). Amplification of target DNA occurred following PCR of all isolates of F. poae but not from any of a range of other fungal species associated with diseases of cereal ears and seed. The primer pair Fp82 F/R was used to detect F. poae in extracts from wheat seed samples contaminated with Fusarium species. This system offers the potential to determine the presence of F. poae in wheat and avoid problems commonly associated with conventional diagnosis of the disease and isolation of the pathogen.
Development of empirical forecasting models for rice blast based on weather factors
Authors: CALVERO Jr S. B. , COAKLEY S. M. , TENG P. S.
Published: November 2003

Regression equations used as empirical models to predict rice blast caused by Pyricularia grisea on cv. Jinheung at Icheon, South Korea, and on cvs. IR50 and C22 at Cavinti, Philippines, were generated, using weather factors identified by the WINDOW PANE program to be highly correlated with disease. Consecutive days with RH≥80% (CDRH80), number of days with RH≥80% (NDRH80), consecutive days with precipitation, and number of days with precipitation ≥ 84 mm day−1 were important variables predicting blast at Icheon. Total precipitation, precipitation frequency, mean maximum and minimum temperatures, number of days with wind speed above 3.5 m s−1, CDRH80, and NDRH80 were important predictors of blast at Cavinti. The Allen’s predicted error sum of squares (PRESS) criterion and a cross‐validation procedure were used to evaluate the models using data that were not included in model development. Validation test showed that all models developed for the two sites, except the models predicting maximum lesion number and panicle blast incidence at Icheon, and panicle blast severity on IR50 at Cavinti, predicted blast reasonably well based on low PRESS values and close to zero average prediction errors. These models can be applied in actual rice production systems, but future validation is needed to further improve their predictive ability.
Resistance mechanisms of Cucumis melo var. agrestis against Trialeurodes vaporariorum and their use to control a closterovirus that causes a yellowing disease of melon
Authors: SORIA C. , SESE A. I. L. , GÓMEZ‐GUILLAMÓN M. L.
Published: November 2003

One of the yellowing diseases that affects melon (Cucumis melo) crops cultivated under plastic greenhouses in southern Europe is caused by a closterovirus transmitted by the greenhouse whitefly Trialeurodes vaporariorum. A Cucumis melo var. agrestis accession shows a certain level of resistance to that virus. Under free‐choice conditions, the reproduction of T. vaporariorum on this accession was significantly lower than on the susceptible control accession C. melo cv. ‘Bola de Oro’, and this suggests that T. vaporariorum prefers to colonize other accessions before C. melo var. agrestis. Under no‐choice conditions, we observed that T. vaporariorum reproduction on C. melo var. agrestis was less than on the susceptible controls. The results showed the participation of both antixenosis and antibiosis resistance mechanisms against T. vaporariorum in C. melo var. agrestis. It is difficult to cultivate melon completely free from T. vaporariorum and yellowing disease. However, success in breeding commercial melon cultivars which incorporate the antixenosis and antibiosis found in C. melo var. agrestis together with biological or chemical insect control, or a combination of these, would reduce the insect population and, therefore, the melon‐yellowing disease would occur later and in less severe form.
Effects of Ascochyta blight caused by Mycosphaerella pinodes on the translocation of carbohydrates and nitrogenous compounds from the leaf and hull to the seed of dried‐pea
Authors: GARRY G. , TIVOLI B. , JEUFFROY M. H. , CITHAREL J.
Published: November 2003

The effects of Ascochyta blight (caused by Mycosphaerella pinodes) on changes in dry weight and in water, carbohydrate, nitrogen and free amino acid contents were studied in the leaf, the hull and the seeds on the second fructifer node of pea (Pisum sativum). Pea plants were grown in a glasshouse and inoculated with various concentrations of conidia at the beginning of seed filling, with uninoculated plants as controls. Disease induced a premature water loss of hulls and leaves, accelerated seed desiccation and reduced seed weight. Biochemical analyses revealed a decline in the carbohydrate content and a lower nitrogen remobilization in diseased leaves and hulls. Thus, Ascochyta blight alters carbohydrate metabolism, protein remobilization and free amino acid translocation from these organs. Disease also reduced carbohydrate and nitrogen content in seeds and, in case of high disease severity, the carbohydrate/nitrogen ratio in the seeds was also affected (seed protein concentration increased and starch concentration decreased).
The effectiveness of postharvest hot water dipping on the control of grey and black moulds in sweet red pepper (Capsicum annuum)
Authors: FALLIK E. , GRINBERG S. , ALKALAI S. , LURIE S.
Published: November 2003

The effectiveness of hot water dipping on the control of grey mould, caused by Botrytis cinerea, and black mould, caused by Alternaria alternata on sweet red pepper quality was investigated. Dipping naturally infected or artificially inoculated fruit at 508C for 3 min completely inhibited, or significantly reduced, decay development caused by B. cinerea and A. alternata, respectively. Heat damage was observed on fruit dipped for 5 min at 50°C, or at 55°C for 1 min or longer. Damage appeared as cracks and pitting on the fruit surface. Spore germination and germ tube elongation in vitro was inversely related to the duration of exposure or to the range of temperature used. The ET50 for spore germination for B. cinerea was 3.2, 1.5 and 0.8 min, and for A. alternata 8.8, 4.2 and 1.4 min, at 45, 50 and 55°C, respectively. The ET50 for germ tube elongation for Botrytis was 2.6, 0.9 and 0.5 min, and for Alternaria, 7.2, 2.5 and 1.6 min, at 45, 50 and 55°C. The mode of action of hot water dips on decay of pepper appears to be by direct interaction with the fungi.
Vegetative compatibility of Fusarium oxysporum from sweet basil in Israel
Authors: KATAN T. , GAMLIEL A. , KATAN J.
Published: November 2003

Fusarium wilt and crown rot of sweet basil, caused by Fusarium oxysporum f.sp. basilici (F.o.ba.), is widespread in Israel. Affected plants show a variety of symptoms, including vascular wilt as well as crown rot, and masses of macroconidia on stem surfaces. We used vegetative compatibility to determine whether F.o.ba. isolates associated with various symptoms and sources are genetically related. All 119 isolates previously described as F.o.ba., and 42 additional F. oxysporum isolates which had not been tested for pathogenicity, belonged to a single vegetative compatibility group (VCG). The various symptoms are therefore induced by a single pathogenic form which appears to be a specific clone of F. oxysporum. The isolates of F.o.ba. from Israel were vegetatively compatible with eight isolates of F.o.ba. from Italy and the USA, but not with nonpathogenic isolates of F. oxysporum from basil, or with F.o. lycopersici or F.o. radicis‐lycopersici from tomato. We conclude that the population of F.o.ba. in Israel belongs to the common VCG of this pathogen described in the USA, and which includes American and Italian isolates.
Modern approaches to species concepts in downy mildews
Authors: HALL G. S.
Published: November 2003

Inadequate species definitions present a serious problem to the pathologist working in plant hygiene or quarantine which demands urgent attention. Species concepts in the downy mildews have not kept pace with developments in evolutionary and molecular biology, or with advances in ecological genetics, because the downy mildews are obligate biotrophs that are not easily cultured in the laboratory. Existing approaches to species concepts in this group (morphometric, Ga¨umann’s ‘biological species’ and Skalicý’s ‘eco–physio–phentic’ concepts) are examined and found to be inadequate and potentially misleading. The systematic treatment of the downy mildews is beginning to benefit from the application of modern methods of systematic analysis. The contribution and potential of ultrastructure, karyotyping, sterol and fatty acid composition, isoenzyme patterns, molecular biology, numerical methods, immunoassay and hypotheses of coevolution to the development of species concepts are reviewed and their wider application is seen as a priority. The application to the downy mildews of two widespread species concepts, the biological and phylogenetic concepts, is examined in the light of the information gained from modern methods of analysis, but neither is found adequate to describe species of downy mildews as they occur in nature. Modern methods can suggest phylogenetic relationships on the basis of statistical probabilities and may also detect microevolutionary change, but it is concluded that much more information is required about individual breeding systems, gene flow, ecology, phylogeny and distribution before informed decisions about the delimitation of most species can be made. Until patterns of genetic diversity can be established, a modified phylogenetic species concept may offer one interim solution to the problem of species definition in the downy mildews.
The origin of Phytophthora infestans populations present in Europe in the 1840s: a critical review of historical and scientific evidence
Authors: Andrivon D.
Published: November 2003

A critical review of available historical and scientific evidence related to the question of the origin of the first European populations of the potato late blight pathogen Phytophthora infestans is presented. It shows that the bases for the current theories of a direct introduction of the fungus into Europe and North America from either a Mexican or an Andean centre of origin and of diversity are questionable. An alternative theory, involving a three‐step process: (i) migration from central Mexico to South America several centuries ago; (ii) migration from South America to the US in 1841–1842, and (iii) migration to Europe from either South America, US or both in 1843–1844, is in good agreement with both the historical records and with the genetics and structure of current populations.
PCR‐based detection of Colletotrichum acutatum on strawberry
Authors: SREENIVASAPRASAD S. , SHARADA K. , BROWN A. E. , MILLS P. R.
Published: November 2003

An oligonucleotide primer (CaInt 2) was synthesized from the variable internal transcribed spacer (ITS) 1 region of ribosomal DNA (rDNA) from Colletotrichum acutatum. PCR with primers CaInt2 and ITS4 (from a conserved sequence of the rDNA) amplified a 490 bp fragment from several isolates of C. acutatum but not from other members of the genus Colletotrichum. Amplification of this fragment was achieved from 100 fg of fungal DNA. These primers amplified a fragment of the same size from DNA extracted from strawberry tissues infected by C. acutatum. Southern hybridization analysis confirmed the 490 bp fragment from C. acutatum DNA and infected strawberry to be identical. The species‐specific primer (CaInt2) developed in this work could be used for the accurate identification of C. acutatum and its detection on other host plants.
Pathogen behaviour and plant cell reactions in interactions between Alternaria species and leaves of host and nonhost plants
Authors: McROBERTS N. , LENNARD J. H.
Published: November 2003

The growth behaviour of several Alternaria species on leaf discs of host and nonhost plants was examined by u.v. microscopy. Specific patterns of development were found for the pathogens. Differences in development which correlated to host specificity, or which differentiated specialized pathogens from weak or opportunistic pathogens, were obvious only after attempted penetration. Thus, little variation was observed amongst different plants for individual Alternaria species in the rate of germination, in the extent of germ‐tube growth or in the frequency of appressorium production. However, plant responses to attempted penetration, which included the formation of callose‐containing papillae, callose deposition in the walls of attacked cells and their neighbours and cell necrosis, varied with specific pathogen–plant interactions. Callose deposition occurred at sites of both successful and unsuccessful penetrations and may, therefore, not be a determining factor in the plant–pathogen interactions examined. A biplot technique is used to illustrate the different degrees of host specificity apparent at pre‐ and post‐penetration stages of fungal development.
Resistance to bacterial wilt in tomato as discerned by spread of Pseudomonas (Burholderia) solanacearum in the stem tissues
Authors: PRIOR P. , BART S. , LECLERCQ S. , DARRASSE A. , ANAIS G.
Published: November 2003

Different criteria were compared for assessing bacterial wilt resistance in 13 tomato genotypes varying in disease susceptibility. Wilt severity and bacterial invasiveness at collar and midstem were compared in the field under cooler (March to May, 20–28°C) and warmer months (June to August, 23–29°C), which were unfavourable and favourable to wilt symptom expression, respectively. A model was proposed for determining resistance regardless of climatic conditions prevalent during field experimentation. This model was based on an estimate of bacterial invasiveness termed the colonization index. Using a qualitative imprint method we confirmed that the more resistant the genotype, the lower the bacterial colonization of the stem. The colonization index accounted both for wilted plants and for infected asymptomatic plants in which Pseudomonas solanacearum populations failed to produce wilt. The colonization index at midstem was the more useful indicator of resistance under favourable conditions. When environmental conditions were unfavourable to wilt, colonization index at collar level discerned resistant genotypes more clearly. The results formed the basis for a model for predicting the degree and stability of resistance in tomato.
The relationship between the amount of Verticillium dahliae in soil and the incidence of strawberry wilt as a basis for disease risk prediction
Authors: HARRIS D. C. , YANG J. R.
Published: November 2003

The incidence of wilt was recorded in runner and fruiting crops of 13 strawberry cultivars at 72 locations in southern England in 1989 and 1990, and soil samples from the sites were analysed for Verticillium dahliae. Linear regressions of wilt incidence on inoculum concentration in soil for runner crops of the susceptible cv. Elsanta in both years were significant whilst that for runner crops of the susceptible cv. Hapil in 1989 approached significance; the regression for cv. Elsanta fruiting crops in 1990 was not significant. The inclusion of sand content of soil in the regression model improved the fit for the cv. Hapil data but not for the cv. Elsanta data; neither clay nor silt content of soil significantly improved the fit of the models for any data set. There were insufficient data in either year for regression analysis for other cultivars, but the levels of wilt generally corresponded with the degree of soil infestation and broadly reflected known field resistance. The data were used to estimate an inoculum concentration which corresponds to 5% wilt incidence (IC5) for cv. Elsanta. It is suggested that this could be used as a yardstick for determining the risk of unacceptable levels of wilt in susceptible cultivars on the basis of pre‐planting soil analysis.  For the 44 sites where the cropping history over the 15 years prior to soil analysis was available there was no clear association between any crop and soil infestation levels at or above the IC5. However, V.  dahliae was more common at sites with a history of vegetatively propagated crops than at sites which had only supported crops grown from true seed.
Genetic variability of Colletotrichum lindemuthianum in wild populations of common bean
Authors: SICARD D. , BUCHET S. , MICHALAKIS Y. , NEEMA C.
Published: November 2003

The genetic structure of wild populations of Colletotrichum lindemuthianum was evaluated for virulence and molecular markers. Forty‐five isolates were collected from five wild common bean populations located in their South‐Andean centre of origin. The five pathogen populations were monomorphic in their ITS regions, but 45 polymorphic markers were identified using RAPDs. Polymorphism for virulence was also observed; 15 pathotypes were characterized on an international set of 12 differentials. A molecular variance analysis (AMOVA) showed that a very large part of the total genetic variation was within populations. Statistical analysis showed that there was a weak though significant differentiation among the five populations for the RAPD and virulence markers. A positive and significant correlation was found between geographic distance and the distances from RAPD and virulence data, suggesting migration between adjacent populations along the Argentinian transect. Our results suggest that the Andean wild isolates of C. lindemuthianum do not reflect all the putative diversity found in the isolates from cultivated common bean.
Effect of soil solarization on the control of Phytophthora root rot in avocado
Authors: LOPEZ‐HERRERA C. J. , PEREZ‐JIMENEZ R. M. , BASALLOTE‐UREBA M. J. , ZEA BONILLA T. , MELERO‐VARA J. M.
Published: November 2003

Phytophthora root rot is of paramount importance in avocado orchards of southern Spain. Soil solarization has been demonstrated to control the pathogen in infested areas from which infected trees had been removed. We aimed to determine whether soil solarization in established avocado orchards controls the disease. Soil solarization increased average maximum hourly soil temperatures by 6.5–6.9°C in unshaded areas of avocado orchards in coastal areas of southern Spain, depending on depth and year. The corresponding temperatures in shaded areas were c. 2–3°C lower. P. cinnamomi in soil, on infected avocado rootlets, and in a nutrient substrate buried at 30–60 cm depth was reduced to negligible amounts after 6–8 weeks of solarization in both unshaded and shaded locations of avocado orchards. P. cinnamomi could not be detected in avocado rootlets up to 14 months later, suggesting a long‐term effect. Soil solarization did not affect growth of the trees, and fruit yields were increased as compared with control plots. Following soil solarization for 3 weeks from mid‐July 1994, when maximum hourly temperatures reached 33–36°C, P. cinnamomi could not be recovered from a depth of up to 45 cm in unshaded areas or from a depth of up to 30 cm in shaded areas after the initial 10‐day period. The viability of inoculum of the pathogen buried at depths between 15 and 60 cm in bare soil was determined by sequential sampling in two solarization experiments starting 12 June and 4 July 1995, respectively. In the first experiment, P. cinnamomi could not be detected at any depth after 4–8 weeks of solarization in unshaded areas but could be recovered at all depths except 15 cm in shaded areas. In the second experiment, where temperatures were higher and the soil surface not shaded, P. cinnamomi could not be recovered after 2 weeks at 15 and 30 cm.
Pathogenicity of Rhynchosporium secalis isolates from Norway on 30 cultivars of barley
Authors: SALAMATI S. , TRONSMO A. M.
Published: November 2003

The pathogenic variability of the barley scald fungus, Rhynchosporium secalis, in central Norway was examined in 1994. The climate in this region is usually cold and wet during the growing season of spring barley. Leaf blotch is prevalent and causes significant yield losses. Forty‐two isolates of the fungus, from naturally infected spring barley in four counties, were differentiated into 32 pathotypes by the standard differential set for R. secalis. All pathotypes were complex and had virulence for nine to 22 differentials. The cultivar Osiris was resistant to all isolates tested. The cultivars C.I.8162, Hudson, Atlas 46 and C.I.3515 were resistant to the majority of the isolates. Several differentials with various resistance genes were susceptible to up to 100% of the isolates. Isolates were derived from local cultivars with no known resistance genes, suggesting that R. secalis populations in central Norway are characterized by a high degree of seemingly unnecessary pathogenicity. Because of the great variability and complexity of the pathotypes, traditional breeding methods using single major genes are not likely to be effective in central Norway.
Elimination of phytoplasma by stem culture from mulberry plants (Morus alba) with dwarf disease
Authors: DAI Q. , HE F.‐T. , LIU P.‐Y.
Published: November 2003

Stem culture in vitro was attempted for the elimination of mulberry dwarf phytoplasma. Stem segments, from mulberry plants (Morus alba) seriously infected with the phytoplasma, were cultured on Murashige and Skoog (MS) solid nutrient medium without phytohormones for 2–3 months. The tissue cultures, and regenerated plants grown under greenhouse conditions for 3 years, were tested by polymerase chain reaction (PCR) and 4,6‐diamidino‐2‐phenylindole (DAPI) staining for the presence of the phytoplasma, and also observed for mulberry dwarf symptoms. From 70% to 90% of regenerated plants were apparently freed from the phytoplasma since they remained PCR‐negative, DAPI‐negative and symptom‐free for as long as tested (3 years).
Genetic analysis of resistance to Puccinia striiformis in the wheat differential cultivars Heines VII, Heines Peko and Strubes Dickkopf
Authors: CALONNEC A. , JOHNSON R. , De VALLAVIEILLE‐POPE C.
Published: November 2003

One major gene for resistance to isolate WYR 85‐22 of race 6E0 of Puccinia striiformis was identified by genetic analysis of the differential cultivars Heines Peko, Strubes Dickkopf and Heines VII. This gene was different from Yr2Yr6 already identified in Heines Peko (Yr2Yr6) and Heines VII (Yr2), was allelic in the three cultivars and also to a gene expressed in the other differentials Reichersberg 42 (Yr7) and Clement (Yr9). In Heines Peko, Strubes Dickkopf and Heines VII, a minor gene was also postulated, which, it is proposed, gave only a low level of resistance by itself but strengthened the expression of the major gene when the latter was homozygous or heterozygous. The genetics of the resistance was analysed using six resistance classes and applying multidimensional analyses. The number of resistance genes was hypothesized using data from F3 families from crosses between the three differentials and the cultivar Heines Kolben, which is susceptible to this race.
Studies on the potential use of Pasteuria penetrans as a biocontrol agent of root‐knot nematodes (Meloidogyne spp.)
Authors: TZORTZAKAKIS E. A. , DE. R. CHANNER A. G. , GOWEN S. R. , AHMED R.
Published: November 2003

Some aspects of the interaction of the bacterial parasite Pasteuria penetrans and the root‐knot nematode (Meloidogyne spp.) were investigated in laboratory and pot experiments. The variable spore attachment on juveniles exposed to water suspensions of the bacterium is probably attributed to differential susceptibility of biotypes within a heterogeneous Meloidogyne population. The relationship between spore concentration and attachment level is not linear over a range of spore dosages, indicating that even at very high spore concentrations the number of spores capable of attachment may not be present in excess and it is difficult to ensure sufficient numbers of spores to ensure infection will attach to all nematodes. Attempts to apply the bacterium in conditions such as might occur in seedbeds did not suppress nematode multiplication after transplanting in nematode‐infested soil, indicating that the only effective application method is a thorough spore distribution in the planting sites. Two major constraints were revealed: high levels of spore attachment to juveniles does not always guarantee a significant reduction of egg laying and this is greatly influenced by the Meloidogyne biotype. Furthermore, the cumulative effect of the parasite in reducing Meloidogyne populations over several crop cycles was less than expected as the bacterium reduced intra‐specific competition for the food supply and the less damaged root enabled many nematodes to survive.