bluuebunny/crossref_metadata_2025_split huggingface dataset:
Further studies on turnip yellow mosaic tymovirus isolates from an endemic Australian Cardamine
Authors: GUY P. L. , GIBBS A. J. 
Published: April 2007

Native and introduced species of Cardamine and other brassicas were collected from various parts of south‐eastern Australia and tested for sap‐transmitted viruses. Isolates of turnip yellow mosaic virus (TYMV‐Cd) were obtained from a robust sward‐forming (SF) species, C. lilacina, that is an endemic species and restricted to the high glacial cirques of the Kosciusko alpine area. At two sites (Blue Lake and Club Lake) 22% of the plants were infected. An undescribed species of flightless pill beetle, Pedilophorus (Byrrhidae), was found on the C. lilacina SF plants. They preferred feeding on leaf discs infected with TYMV‐Cd rather than on virus‐free leaf discs and transmitted the virus for 48 h to seedlings of C. lilacina SF (2.5%) or Chinese cabbage (10%).The pattern of distribution of TYMV‐Cd and its close association with Pedilophorus suggested that it is not a recent migrant to the area. The possible time of its arrival is discussed.A carlavirus was isolated from up to 4% of three other native highland Cardamine species.
Some effects of canopy structure and microclimate on infection of tall and short wheats by Septoria nodorum
Authors: SCOTT P. R. , BENEDIKZ P. W. , ZONES H. G. , FORD M. A. 
Published: April 2007

The results of three kinds of field experiment were consistent with the hypothesis that the canopies of taller wheat varieties generate a less favourable microclimate for development of S. nodorum from standard inoculum. (1) Measurements of photosynthetic area per unit volume of space occupied by canopies showed that taller varieties had lower canopy densities than shorter varieties. (2) Less disease developed in artificially thinned canopies of tall and short varieties. (3) Less disease developed in plots raised on mounds and more developed in plots sunk in trenches, relative to plots at ground level.The results of three further kinds of field experiment were consistent with the hypothesis that reduced leaf surface wetness contributes to the tendency for taller varieties to be less infected by S. nodorum. (1) Continuous electrical measurement showed that leaf surface wetness (mainly dew) on two tall resistant varieties lasted for a shorter time than that on a short susceptible variety. (2) Instantaneous estimation of dew by weighing showed that less was deposited on taller and more resistant varieties than on shorter and more susceptible varieties. (3) For 10 sister lines from the same cross, selected only for their variation in height, there were correlations of duration of surface wetness with height (negative), amount of S. nodorum with height (negative), and amount of .V. nodorum with duration of surface wetness (positive). There was also genetic variation in surface wetness that was independent of height.Nevertheless, a microclitnatic effect is thought to be only one of several mechanisms that contribute to the tendency for taller varieties to be more resistant. In addition, there is much genetic variation in resistance that is independent of height.
The effect of powdery mildew (Erysiphe graminis f. sp. hordei) and leaf rust (Puccinia hordei) on spring barley in New Zealand. I. Epidemic development, green leaf area and yield
Authors: LIM L. G. , GAUNT R. E. 
Published: April 2007

Powdery mildew and leaf rust caused large yield losses in spring barley grown near Christchurch, New‐Zealand, in two seasons. Disease present during early growth stages was as damaging to yield as disease late in the season. Moderate leaf rust severities after anthesis were most damaging when combined with earlier mildew epidemics. Later growth did not compensate for reduced yield potential induced by early infection. This was attributed, at least in part, to an effect on leaf size, and therefore on green leaf area, at later growth stages. There was a closer relationship, by regression analysis, of yield to green leaf area than to disease severity in three cultivars.The three cultivars. which differed in yield potential and disease resistance, were not equally sensitive to disease. It is proposed that high yielding cultivars may be the most sensitive to yield constraint by disease.
A comparative study of the pathogenicity and epidemiology of strains of Pseudomonas syringae pv. tabaci that cause wildfire and angular leaf spot diseases of tobacco in Zimbabwe
Authors: DEALL M. W. , COLE J. S. 
Published: April 2007

The population dynamics of two strains of Pseudomonas syringae pv. tabaci that cause the foliar spot diseases of tobacco known as wildfire (WF) and angular leaf spot (ALS) were significantly different in leaves of a susceptible tobacco cultivar. After 48 h the population of WF strains changed abruptly from exponential growth to stationary phase, whereas there was a more gradual transition by the ALS strains. This resulted in smaller stationary‐phase populations for WF than for ALS. The decline of the WF population started soon after the stationary phase was reached, whereas the ALS stationary phase was relatively stable.The strains reacted differently to climatic factors. On plants inoculated and exposed to the weather at weekly intervals, WF lesions grew faster when vapour pressure deficits, maximum temperatures and radiation were low. Multiple regression analysis showed that over 70% of the variation in WF infection was accounted for by variation in VPD, radiation and mean temperature. Variation in ALS infection was less easily explained in relation to the weather variables measured.Plant age and stalk position had a differential effect on the pathogenicity of the two strains. Lower leaves of young plants (42 days) were most susceptible to WF and top leaves of older plants (84 days) were most susceptible to angular leaf spot. Differences in pathogenicity and occurrence in the field suggest that pathovar status should be considered for the ALS pathogen of tobacco.
Effects of temperature and leaf wetness on Pyrenophora teres growing on barley cv. Sonja
Authors: SHAW M. W. 
Published: April 2007

Conidia ofPyrenophora teresgerminated only in the presence of liquid water and at temperatures above 2°C. The speed with which germination occurred was inversely proportional to temperature measured from a base of 2°C, up to the maximum temperature tested of 21°C. Once conidia on leaves had been wetted, about 40% of all infections that would eventually occur were established within 100°C‐hours. Subsequent lesion extension was rapid, with area doubling times of about 1 day between 10 and 20°C.If conidia germinated, up to 80% formed successful infections on young, susceptible leaves. On older leaves fewer spores germinated and the proportion that then infected was smaller.The latent period, defined as the time before which sporulation did not occur under any wetness conditions, ranged from about 25 days at 5°C to 11 days at 20°C under dry conditions. Under continuously wet conditions it was about 20% shorter at all temperatures. Its inverse had a curvilinear relation to temperature.Spores were produced after one to several days of humidity above 95%. The precise period decreased with increasing temperature, but at 25°C spores never appeared. The drier a dead leaf was, the longer the pathogen in it look to produce spores.
Dicarboximide resistance in Botrytis cinerea in protected lettuce
Authors: WANG ZU‐NAN , COLEY‐SMITH J. R. , WAREING P. W. 
Published: April 2007

In surveys of protected lettuce crops in the Humberside area of the UK during 1984‐5, 47.3% ofBotrytis cinerea isolates were resistant to dicarboximides and 25% to benomyl. Dicarboximide‐resistant isolates obtained direct from the field had a moderate degree of resistance with ED50 values for mycelial growth on agar of 1.0‐2.4 μg/ml vinclozolin for all except two of 30 isolates.Isolates which were resistant to vinclozolin were also resistant to iprodione, myclozolin and procymidone. Thirty dicarboximide‐resistant isolates obtained direct from the field were capable of infecting cucumber cotyledons sprayed with field‐strength Ronilan (250 μg/ml vinclozolin) whereas sensitive strains were not. Strains showing different degrees of resistance to dicarboximides developed after incubation of sensitive and resistant strains on agar supplemented with vinclozolin. Some of these strains had ED50 values for mycelial growth on agar of more than 100 μg/ml vinclozolin. No highly resistant isolates were obtained direct from the field. Resistance to dicarboximides in field isolates was stable.
Effect of temperature on potato virus X infection in potato cultivars carrying different combinations of hypersensitivity genes
Authors: ADAMS SALLY E. , JONES R. A. C. , COUTTS R. H. A. 
Published: April 2007

In potato cultivars reacting non‐hypersensitively, systemic mosaic symptoms were obvious at 10‐20°C for potato virus X (PVX) isolate DX, and at 10 and 15°C for PVX isolate B: systemic movement was slowest at 10°C especially with DX. Viral antigen accumulation in non‐inoculated leaves was greatest at 15 and 20°C with B. but with DX accumulation was as great at 25°C, The highest viral antigen concentrations reached were less with B than with DX. No PVX was detected in plants grown at 30°C.In potato cultivars carrying gene Nx, necrotic local lesions appeared at 10‐25°C in DX‐inoculated lea ves within 8 days; systemic necrosis developed soon after at 15 and 20°C, but was very slow to appear or failed to develop at 10 and 25°C, Necrosis was more conspicuous when gene Nb was also present. Except at 10°C in the Nx:nb cultivar used, presence of Nx decreased accumulation of DX antigen.Although numerous necrotic lesions developed in B‐inoculated leaves at 10°C in the presence of gene Nb, very few formed at 15 and 20°C, and none at 25°C. In B‐inoculated leaves from plants at 15‐25°C, no new lesions were induced by temperature shock treatments and no starch lesion formation was detected. Gene Nb completely prevented movement of isolate B out of inoculated leaves at all temperatures regardless of whether infection was symptomless or necrotic local lesions developed, The concentration of B‐antigen was considerably decreased by Nb.It was possible to quantify the general effects of genes Nx and Nb on accumulation of DX‐ and B‐antigens: in the combination Nx:Nb the ineffective gene interacted with the effective gene to cause a greater depression of viral antigen accumulation than expected. Unlike hypersensitivity genes for tobacco mosaic virus in tomato and tobacco, Nx and Nb in potato did not lose their effectiveness with increasing temperature. Differences in virus accumulation and in temperature optima for multiplication between PVX strain groups may account for the lack of competitiveness shown by those belonging to group two.
Dieback and death of larch caused by Ceratocystis laricicola sp. nov. following attack by Ips cembrae
Authors: REDFERN D. B. , STOAKLEY J. T. , STEELE H. , MINTER D. W. 
Published: April 2007

Circumstantial and experimental evidence suggests that the bark beetle Ips cembrae acts as a vector for Ceratocystis laricicola sp. nov. which it introduces into larches during breeding attacks. The fungus kills bark and cambium, and invades the sapwood causing the formation of areas of ‘blue stain’ surrounded by dry wood. Multiple inoculations resulting from numerous beetle attacks may totally disrupt conduction causing dieback and death of whole trees. Attacks seem frequently to be associated with drought and other forms of stress. Trees damaged by I. cembrae and C. laricicola may be attacked subsequently by the woodwasp Urocerus gigas which introduces a sapwood decay fungus, Amylostereum chailletii.This is the first record of an association between I. cembrae and a species of Ceratocystis and the first record of dieback in larch caused by I. cembrae and C. laricicola. I. cembrae was introduced into Britain from mainland Europe and a similar association may occur there.
Sources of Verticillium fungicola on a commercial mushroom farm in England
Authors: WONG W.C. , PREECE T. F. 
Published: April 2007

From 1979 to 1981 Verticillium fungicola, a pathogen to Agaricus bisporus, was detected in 47 out of 485 samples of baled peat and in one out of 126 samples of bagged limestone arriving at an isolated mushroom farm in the UK. The pathogen was not detected in 875 samples of water, soil, mushroom spawn or spawned compost. Casing (a mixture of peat and limestone) prepared and used on the farm contained detectable V. fungicola in 25 out of 108 samples. The primary sources of V fungicola were thus the two constituents of casing, especially peat.Secondary sources of V. fungicola were numerous and included symptomless and diseased mushrooms, pickers and other staff, floors and doors and the principal pests (sciarid flies and mites).Viable airborne spores of V. fungicola were detected with an Andersen sampler in farm buildings at all stages in crop production. The spore load increased with the age of the crop. Few airborne spores were detected immediately outside affected buildings, and very few at the farm entrance 30 m away. There was no evidence that V. fungicola reached the farm from the surrounding air. despite substantial soil disturbance nearby.Selective media for V. fungicola are described.
Disinfection of pepper seed infected with different strains of capsicum mosaic virus by trisodium phosphate and dry heat treatment
Authors: RAST A. Th. B. , STIJGER C. C. M. M. 
Published: April 2007

Disinfection of pepper seed infected with capsicum mosaic virus (CaMV) by immersion in 100 g/1 Na3 P04 solution was compared with dry heat treatment at 76°C. The virus content of the seed varied with the CaMV strains used to infect the pepper cultivars and the time of harvest of seeds from infected plants. Immersion times in Na3PO4 had to be increased from 15 min to 2 h to obtain near‐complete virus inactivation; these treatments had no effects on germination.Heating seed in an oven at 76°C for 3 days following a waiting period of 3 months after harvest always eliminated all the virus present, but adversely affected germination. This resulted in delayed emergence and a reduction in the number of seedlings suitable for further raising. The viability of heat‐treated seeds also decreased with continued storage after treatment.There were inconsistent differences in germination of seed from healthy plants and plants infected with the CaMV strains P8 or P11. The possibility of internal seed infection and practical consequences are discussed.
Cane spot (Elsinoë veneta) in red raspberry: infection periods and fungicidal control
Authors: MUNRO J. M. , DOLAN A. , WILLIAMSON B. 
Published: April 2007

Dichlofluanid controlled cane spot (Elsinoë veneta) of raspberry cv. Mailing Jewel when applied before harvest in a four‐spray programme, but carbendazim, vinclozolin and iprodione were ineffective. Lesions predominated in the fruit‐bearing region of canes in a zone 46‐120 cm above soil level. Bait plants exposed for periods of 2 weeks in two infected plantations in north‐east Scotland developed lesions, after incubation for 4‐6 weeks, only on internodes which were the youngest at the time of exposure. Infection occurred in all periods from mid‐April to late July. The infection of bait plants was related to the distribution of lesions on canes in the spray trial.An isolate of E. veneta obtained from a plantation sprayed with carbendazim and vinclozolin was resistant when tested in vitro to carbendazim, benomyl and thiophanate‐methyl. This isolate and another MBC‐sensitive strain were both relatively insensitive to the dicarboximide fungicides iprodione and vinclozolin.
Pasture ecology of barley yellow dwarf viruses at Sandford, Tasmania
Authors: GUY P. L. 
Published: April 2007

Samples of cocksfoot (Dactylis glomerata), fescue (Festuca arundinacea), phalaris (Phalaris aquatica) and ryegrass (Lolium perenne) were collected every 4‐6 weeks for 2.5 years from two sets of replicated plots, one on a heavy soil and the other on a light soil 200 m away. Rhopalosiphum padi was the predominant aphid species; it was more frequent at the heavy soil site. Sitobion fragariae and Metopolophium dirhodum occurred infrequently during the last 12 months of the survey.Only PAV (57%), RPV (26%) and mixed infections (17%) of these barley yellow dwarf viruses were detected in the 4100 tillers sampled. Virus incidence increased over the sampling period and was consistently higher at the heavy soil site. RPV only became frequent during the last 12 months.Virus incidence was higher in fescue (21%) and ryegrass (27%), in which PAV predominated, than in cocksfoot (6%) and phalaris (7%), in which RPV finally predominated.
Opine utilization by Spanish isolates of Agrobacterium tumefaciens
Authors: LÓPEZ M. M. , GORRIS M. T. , MONTOJO A. M. 
Published: April 2007

Among 115 Spanish isolates of Agrobacterium tumefaciens from 13 hosts and 47 locations, biotypes 1, 2, and 3 were identified. Most isolates were of biotype 2. Biotype 3 isolates were obtained only from grapevine, and all were resistant to agrocin 84. Nopaline was utilized by 84% of isolates. Only three isolates did not utilize either octopine, nopaline or mannopinic acid.Isolates from fruit trees were mostly biotype 2 and utilized only nopaline; some isolates from a peach x almond hybrid utilized mannopinic acid. Rose and osier isolates were biotype 1 and utilized only nopaline. Most grapevine isolates were biotype 3, but varied widely in opine utilization.With one exception all isolates sensitive to agrocin 84 catabolized nopaline; no biotype 3 strains catabolized mannopinic acid and no biotype 1 or 2 strains catabolized octopine.
Peronosclerospora maydis found on maize, sweetcorn and plume sorghum in Far North Queensland
Authors: RAMSEY M. D. , JONES D. R. 
Published: April 2007

Symptoms of a downy mildew disease were recognized on maize growing in the Atherton Tableland and Lakeland Downs areas of Far North Queensland in 1985. Quarantine measures were invoked to prevent the spread of this potentially serious disease to other parts of Australia.The pathogen was identified as Peronosclerospora maydis in 1986 following examination of conidiophores with conidia and host range studies. An alternative host was strongly suspected and a survey near fields where the disease had been prevalent led to the identification of P. maydis on Sorghum plumosum, a grass indigenous to northern Australia. All downy mildew outbreaks on maize and sweetcorn in northern Australia since 1970 have been in areas where S. plumosum occurs. It seems likely that P. maydis has been present in Australia for many years.
Studies on the inheritance of resistance to metalaxyl in Phytophthora infestans
Authors: SHATTOCK R. C. 
Published: April 2007

Single‐oospore progeny from matings between field isolates of Phytophthora infestans either highly resistant or sensitive to metalaxyl were analysed for fungicide sensitivity in vitro, mating type and, in some cases, allozyme variation at the locus for glucosephosphate isomerase (GPI‐1.) In each cross the majority of first‐generation (F1) progeny showed intermediate sensitivity to metalaxyl. Frequency distributions were skewed towards sensitivity and a few progeny were either wholly sensitive or resistant phenotypes. Allozyme analysis of F1 progeny from a cross between parents of Dutch and Mexican origin showed that c. 10% were selfs of both parents and of parental phenotype for metalaxyl sensitivity. The selfs of the A2 but not the Al parent segregated for mating type. Two backcross generations to the metalaxyl‐resistant Dutch parent gave unexpected phenotypic frequency distributions and aberrant ratios for genotypes at the GPI‐I locus.Progeny of another backcross between an F1 isolate of intermediate sensitivity and its sensitive Egyptian parent gave a 1:1 ratio for sensitive: intermediate phenotypes. F2 progeny from a related sibmating between intermediate phenotypes segregated in a ratio close to 1:2:1 for sensitive: intermediate: resistant phenotypes. Segregation was also observed among sexual progeny of an intermediate self‐fertile isolate from the backcross generation but not among progeny of a resistant self‐fertile phenotype. Mating type segregated in both cases.These data are consistent with resistance to metalaxyl in P. infestans being governed by a single nuclear locus exhibiting incomplete dominance. This hypothesis is discussed in relation to the incidence of resistance to metalaxyl in natural populations of P. infestans.
Variation in the pine stem rust fungus Peridermium pini in the United Kingdom
Authors: GIBBS J. N. , ENGLAND N. , WOLSTENHOLME R. 
Published: April 2007

Peridermium pini aeciospores from lesions on Scots pine (Pinus sylvestris) in Scotland and in Thetford Forest, East Anglia, differed in terms of germ tube morphology and cytology. The former produced long aseptate germ tubes containing a pair of nuclei. The latter produced short septate germ tubes, each cell containing a single nucleus. One third of the ‘Scottish’ germ tubes ended in a vesicle. Nuclei could be counted in only a small proportion of ungerminated aeciospores. On average 83% of Scottish spores had two nuclei and 4% had one. The equivalent figures for Thetford spores were 66 and 20%. A small number of aeciospore samples from other parts of England resembled Scottish spores rather than Thetford spores in germ tube morphology and cytology.Both Scottish and Thetford spores proved capable of causing infection of wounded Scots pine shoots. In addition, some Thetford spores caused infection on leaf discs taken from certain Paeonia cultivars. From these results it is concluded that two distinct forms of Peridermium pini exist in the UK. The implications of this finding are discussed in relation to the history of pine stem rust in the country and the genetics and taxonomy of P. pini.
Identification of oat‐adapted isolates of cereal Septoria in the UK using a detached leaf technique
Authors: JOHNSTON H. W. , SCOTT P. R. 
Published: April 2007

Isolates of Septoria spp. from cereals were tested for their relative pathogenicity to detached seedling leaves of three cereal species. Each of 23 isolates showed unequivocal adaptation to either oats, or wheat, or barley. Five oat‐adapted isolates were from Prince Edward Island, Canada, where S. avenue is prevalent on oats; three were from the UK, where there are few oat crops and where adaptation to oats has not been reported.Oat‐adapted isolates tended to have pycnidiospores of above‐average length and could be referred to S. avenae. Wheat‐adapted and most barley‐adapted isolates had shorter spores and could be referred to S. nodorum. UV‐fluorescent pigment was produced on oxgall agar by all wheat‐adapted isolates, but only by a minority of oat‐adapted and barley‐adapted isolates.It is suggested that adaptation to cereal species is a more useful character than spore length for classifying isolates.
Parietaria mottle virus, a possible new ilarvirus from Parietaria officinalis (Urticaceae)
Authors: CACIAGLI P. , BOCCARDO G. , LOVISOLO O. 
Published: April 2007

A previously undescribed virus, probably a new member of the ilarvirus group, was isolated from Parietaria officinalis showing symptoms of yellow mosaic or mottling. This virus, for which the name parietaria mottle virus (ParMV) is proposed, differs in host range from other ilarviruses. ParMV was purified from Chenopodium quinoa by sap clarification with chloroform, and differential and sucrose density gradient centrifugation.Purified particles were quasi‐isometric to ovoid with diameters of about 24, 29 and 36 nm; no bacilliform particles were detected. Buoyant density in caesium chloride, determined on glutaraldehyde‐fixed virus, was 1.35 g/cm3.An antiserum to ParMV was obtained with a titre of 1:32 in agar gel double‐diffusion tests. ParMV did not react with eight other viruses or virus strains belonging to the ilarvirus group or to pelargonium zonate spot virus.Polyacrylamide gel electrophoresis indicated that ParMV contains a single major protein species of estimated molecular weight 24300 Da and four RNA species of estimated molecular weight 1 37, 1.19, 0.86 and 0.36 × 106 Da.