bluuebunny/crossref_metadata_2025_split huggingface dataset:
An assessment of fungicides for the control of wilt and die‐back caused by Phytophthora cinnamomi in container‐grown Chamaecyparis lawsoniana cv. Ellwoodii
Authors: SMITH PAULINE M. 
Published: February 2008

SUMMARYIn fungitoxicity tests against Phytophthora cinnamomi on Chamaecyparis lawsoniana cv. Ellwoodii, a drench of furalaxyl (1000 mg a.i./l) applied to the compost in which 1‐yr‐old plants were growing, 1 wk before they were inoculated with 650 000 zoospores, controlled disease for at least 12 months. With an inoculum dose of 650 zoospores/plant, furalaxyl at 500 mg a.i./l controlled disease even when inoculation was 12 wk after fungicide treatment.Aluminium tris (ethyl phosphonate) (2000 mg a.i./l) applied as a drench 1 wk before inoculation with 650 000 zoospores/plant did not prevent root infection but delayed foliar symptoms for 9 months: the same treatment, using etridiazole (500 mg a.i./l) only slightly reduced disease incidence.When applied as a single drench 2 days before inoculation, prothiocarb (2000 mg a.i./l) and cuprammonium compounds (200 mg a.i./l) were much less effective than furalaxyl (1200 mg a.i./l), sodium ethyl phosphonate (1500 mg a.i./l), aluminium tris (ethyl phosphonate) (1500 mg a.i./l) or etridiazole (500 mg a.i./l).However, a drench of furalaxyl at 1000 mg a.i./l, aluminium tris (ethyl phosphonate) at 2000 mg a.i./l or etridiazole at 500 mg'a.i./l did not eradicate P. cinnamomi from compost containing infected root debris. Pre‐planting drenching of the compost was ineffective.All fungicide treatments were non‐phototoxic to 1‐yr‐old C. lawsoniana cv. Ellwoodii.These results are of special relevance to the control of P. cinnamomi on container‐grown woody ornamentals.
Insect transmission of okra mosaic virus in the Ivory Coast
Authors: GIVORD L. , BOER L. DEN 
Published: February 2008

SUMMARYThe Ivory Coast and Nigerian strains of okra mosaic virus (OMV) were transmitted by the flea‐beetle Podagrica decolorata, a serious pest of okra in the southern Ivory Coast. The Ivory Coast strain was also transmitted by the orthopteran, Zonocerus variegatus. The Ivory Coast strain was acquired faster than it was inoculated by P. decolorata. When groups of five beetles were given acquisition and inoculation access periods of 24 and 48 h, respectively, 60% of the okra test plants were infected. OMV‐carrying P. decolorata remained infective for up to 6 days. The virus was readily detected in extracts of crushed beetles that had fed on infected plants for 20 h. The beetle was also able to transmit to and from plants of Hibiscus sabdariffa and Corchorus olitorius; as a food source it preferred C. olitorius to okra or H. sabdariffa. The beetle is active throughout the year, and presumably can spread OMV at any time between plants of these species. A considerable and unexplained decrease in frequency of transmission was observed in experiments done in the rainy season. The revised cryptogram of OMV is R/l:*/32:S/S:S/Ve/Cl.
I. Pathogenic variation in fungi and bacteria and mycorrhizal compatibility: The genetic architecture of aggressiveness in Ustilago maydis
Authors: BASSI F. G. A. , BURNETT J. H. 
Published: February 2008

ABSTRACTIsolates of Ustilago maydis (D.C.) Cda are known to differ in the degree to which they can parasitise maize and, as no differential reaction occurs between pathogen and host, these differences must be differences in aggressiveness.Inoculation of juvenile maize plants induced morphological changes which provided a means of assessing and distinguishing U. maydis isolates in respect of their aggressiveness. Thus it was possible to carry out a survey of the genetic architecture of aggressiveness in natural populations of the pathogen.The distribution of aggressiveness within a single gall suggested that selection had taken place over a number of generations in favour of genes or gene systems tending to increase aggressiveness. Diallele analyses of isolates from two natural populations revealed that aggressiveness had a low heritability and was determined by genes exhibiting mainly non‐allelic interaction.It has been proposed that horizontal resistance in host cultivars would have a more long lasting protective effect against disease. However, the genetic architecture of aggressiveness in U. maydis should enable the pathogen to respond rapidly to changes in host resistance and the skewed distribution found within a single gall tends to support this. Therefore, the use of higher levels of host resistance should rapidly select for higher aggressiveness in the pathogen.
I. Pathogenic variation in fungi and bacteria and mycorrhizal compatibility: Intraspecific variation in a mycorrhizal association
Authors: MASON P. A. 
Published: February 2008

ABSTRACTLaboratory studies with combinations of the fly agaric, Amanita muscaria (L. ex Fries) Hooker and birch (Betula pendula (Roth.)) suggest that the genetical control of mycorrhizal formation has features in common with the legume/Rhizobium symbiosis. There are at least four factors that can be genetically controlled by either the host or the fungus: (a) mycorrhizal formation; (b) the extent of mycorrhizal development; (c) the pattern of mycorrhizal branching, and (d) the shape and size of the host root system.
II. Cereal disease: the interplay between resistance and pathogenicity: Inheritance of pathogenicity in Gaeumannomyces graminis var. tritici
Authors: BLANCH P. A. 
Published: February 2008

ABSTRACTThe purpose of the research was to discover whether pathogenicity in G. graminis is under major gene or multiple gene control and how pathogenic variation is generated in the field. The shoot dry weight of infected wheat seedlings was used as a measure of pathogenicity.Crosses were made between isolates differing in pathogenicity using a weakly pathogenic auxotrophic mutant requiring para‐aminobenzoic acid for growth as one of the parental isolates in each cross. A nuclear marker was necessary since G. graminis is homothallic. The mutation was produced by irradiating macerated hyphal strands with ultra‐violet light.Analysis of the progeny indicated that pathogenicity is under multiple gene control and that most of the genotypic variation is additive. There is a possibility of non allelic interactive effects but the evidence is not conclusive.The possibility of heterokaryosis in G. graminis was investigated by comparing pathogenicity between hyphal tip cultures and internal cell cultures derived from individual field isolates. Some field isolates were shown to be heterogeneous. In addition, heterokaryotic hyphae were synthesised between the mutant isolate and its parental wild‐type isolate. These results showed that potentially G. graminis could grow as a heterokaryon although how widespread this is in nature is not clear.
III. Variation in plant viruses: Variation in ryegrass mosaic virus in relation to resistance
Authors: WILKINS P. W. 
Published: February 2008

ABSTRACTSome isolates of ryegrass mosaic virus are mild in all but a few plants, others are more severe. Infection with a severe isolate reduced the yield of a ryegrass population by 24% under field conditions and reduced survival following cold treatment by 85%. Field isolates from the short‐lived Italian ryegrasses are generally severe while those from the long‐lived late‐flowering perennial ryegrasses are generally mild. This variation appears to be adaptive in origin since in the case of perennial ryegrass proneness to infection by severe isolates would probably lead to the elimination of both host and virus whereas Italian ryegrass can escape infection readily by copious production of seed.
IV. Variation in fungicide tolerance: Variation in Erysiphe graminis f. sp. hordei in response to the fungicide ethirimol
Authors: HOLLOMON D. W. 
Published: February 2008

ABSTRACTThe genotypic variation of Erysiphe graminis f. sp. hordei was examined using ethirimol in an in vitro bioassay. ED50 values of 45 isolates from untreated crops ranged from 0·002 μg/ml‐1to 20μg/ml1.Less variation was encountered in isolates from ethirimol treated crops, where ED50 values ranged from 0·02 μg/ml‐1to 20μg/ml‐1. Crosses between isolates with intermediate levels of ethirimol sensitivity increased variation, and many progeny exceeded the sensitivity of either parent. The response of barley powdery mildew to ethirimol seems to be controlled by a complex genetic system, rather than by one or two major genes. Nevertheless, heritability was surprisingly high in two crosses analysed (0·596). Progeny virulent on the varieties Julia (vg) or Sultan (vas) were possibly more resistant to ethirimol than those with the alternative avirulent allele, but the differences were not significant (P= 0·05).
IV. Variation in fungicide tolerance: Comparisons between isolates of Erysiphe graminis f. sp. hordei tolerant and sensitive to the fungicide tridemorph
Authors: WALMSLEY‐WOODWARD DIANNE J. , LAWS F. , WHITTINGTON W. J. 
Published: February 2008

ABSTRACTForty‐five single pustule isolates of barley powdery mildew taken at random from tridemorph treated and untreated plants were maintained in culture on leaf segments of barley cv. Golden Promise placed on agar containing benzimidazole. In repeated assays for tridemorph tolerance over a 10 month period, tolerance was found in 25 of 36 isolates from treated plants, and remained stable in all but four of the isolates wherein tolerance was lost after varying lengths of time. A negative correlation was found between pathogenicity and tolerance. The germination of tolerant isolates was less depressed than the sensitive on treated seedlings, but no differences between isolates were found on untreated seedlings. Colony growth of all isolates was slower on treated than untreated seedlings. On plants of several cultivars kept in growth rooms, mildew progressed more rapidly on treated barley when tolerant isolates were used as inoculum. Visible disease symptoms spread most rapidly on isolated, untreated plants, and most slowly on isolated treated plants, irrespective of the isolate. Disease on treated plants progressed more rapidly when untreated plants were adjacent, suggesting that interactions take place between pathogen populations on treated and untreated plants.
Studies on Entomophthora in populations of Aphis fabae on field beans
Authors: WILDING N. , PERRY J. N. 
Published: February 2008

SUMMARYThe population of Aphis fabae on field beans at a site in Highfield, Rothamsted in 1973 reached its peak 1 wk earlier than that at an equivalent site in Mill Dam Close, Woburn, 29 km NW of Rothamsted. Epizootics of Entomophthora caused weekly maximum mortalities of adult apterae of 71% at Highfield and 67% at Mill Dam Close. These epizootics and the periodicity of Entomophthora conidia in the air closely paralleled the development of the aphid population. There was little evidence of a consistent relationship between Entomophthora infection and any of the weather factors considered. At both sites most mortality was caused by E. planchoniana though many aphids were killed by E. aphidis and E. obscura. E. fresenii and E. virulenta killed very few aphids. Most conidia in the air were of the E. aphidis‐type. Up to 44% of alatae emigrating from bean crops were infected with Entomophthora, confirming that aphid migration is an important means of distributing the fungi. Aphid numbers rose to more than 1600/plant at both sites, in spite of the action of Entomophthora, and would probably have been less had the fungi been more abundant earlier in the season.
Studies on the spread of Gaeumannomyces graminis var. tritici in wheat.
Authors: PREW R. D. 
Published: February 2008

SUMMARYThe autonomous spread of Gaeumannomyces graminis var. tritici from discrete sources of inoculum, consisting of naturally infected stubble and roots, was measured in three field experiments. Spread occurred from only half of the inoculum sources and when it did occur it averaged a distance of only 10 cm.
Studies on the spread of Gaeumannomyces graminis var. tritici in wheat.
Authors: PREW R. D. 
Published: February 2008

SUMMARYThe effect of cultivations on the spread of Gaeumannomyces graminis var. tritici from a line source of inoculum, consisting of naturally infected stubble and roots, was recorded in the field over 2 yr. With the aid of cultivations, spread in the first wheat crop occurred frequently to a distance of 0·9 m and occasionally to a distance of 2·5 m. However, the following wheat crop was uniformly infected, probably as a result of a rapid build‐up of background inoculum in the first wheat, so that any spread by cultivations was masked.
The influence of photoperiod on growth patterns of Erysiphe graminis f. sp. hordei
Authors: CARVER T. L. W. , WILLIAMS OLWEN 
Published: February 2008

SUMMARYDetached seedling leaf segments of five spring barley genotypes were inoculated with an isolate of barley mildew to which they possessed different levels of resistance. Segments of each host genotype were then incubated under either continuous light or treatments with 2, 4, 8 or 16 h darkness per 24 h cycle. Macroscopic observation showed that the latent period of infection was reduced slightly in treatments with at least 4 h darkness/24 h. Yellowing of detached segments occurred fastest under continuous light and slowest under a 16 h dark/8 h light cycle. Microscope observation of segments fixed 4·5 days after inoculation showed that as the length of the dark period increased, so the number of haustoria formed per colony also increased. This increase in haustorial production appeared to be associated with an accentuation in the synchrony of production of the secondary and tertiary haustorial generations. Varietal differences in susceptibility were also more marked in segments incubated under short days. It is concluded that under the conditions of temperature and light intensity used, a 16 h dark/8 h light system is most desirable for quantifying mildew resistance because it allows confident identification of distinct haustorial generations, accentuates differences in varietal susceptibility and delays chlorophyll degradation in detached barley leaves infected with mildew.
The effect of defoliation on yield of radish
Authors: JACKSON T. A. 
Published: February 2008

SUMMARYThe effects of artificially defoliating radish at different times during growth were examined in pot experiments. Hypocotyl yields were negative linear functions of the level of defoliation irrespective of the stage at which this occurred as the plants were unable to compensate for loss of foliage. Yield was proportional to leaf area duration and greatest losses in yield followed the earliest defoliations.
Promotion of cone and seed production on Sitka spruce by gibberellin application
Authors: TOMPSETT P. B. , FLETCHER A. M. , ARNOLD GILLIAN M. 
Published: February 2008

SUMMARYGibberellin mixtures were applied to large, mature scions of Sitka spruce, growing in the open at Wauchope Tree Bank in 1975, 1976 and 1977. Large increases in coning and seed production, and in the numbers of clones producing seed, occurred in the year after treatment. Cone and seed yields varied with the timing and concentration of hormone treatment, and were greatest when applications were made in the top two branch whorls on the tree. Clonal differences in seed production were observed among gibberellin‐treated branches. Seed quality, judged by seed weight and percentage germination, appeared normal. Promotion of male strobili was greater in lower branch whorls than in the top branch whorl on the tree.Ways in which these findings can be applied in breeding and seed production are discussed.
Comparative physiology of field‐grown tomatoes during ripening on the plant or retarded ripening in controlled atmospheres
Authors: GOODENOUGH P. W. , THOMAS T. H. 
Published: February 2008

SUMMARYTomato fruits of six cultivars were harvested at three different stages of maturity or were harvested when mature‐green and then stored in a modified gas atmosphere (2·5‐4% O2; 4% CO2) for 2 months. The fresh and stored fruits were analysed for their contents of sugars, organic acids and free amino acids, while proteins were separated by discontinuous electrophoresis on polyacrylamide gels. In general, the low molecular weight components decreased during storage. A comparison of mature‐green fruits before and after storage showed that although total protein was not decreased, a different electrophoretic pattern was obtained following controlled atmosphere (CA) storage. Thus, although controlled atmosphere storage repressed the loss of chlorophyll and synthesis of lycopene, carotenoids and xanthophylls, the biochemical parameters measured showed a controlled change towards the conditions exemplified by ripe fruits. This was not so marked in some cultivars as it was in others.
The production of toxins by Botrytis fabae in relation to growth of lesions on field bean leaves at different humidities
Authors: HARRISON J. G. 
Published: February 2008

SUMMARYFiltrate extracts from liquid cultures of B. fabae and extracts from spreading chocolate spot lesions contained at least two heat‐stable, light‐labile phytotoxic compounds. Lesions similar in appearance to those of chocolate spot developed after injection of fractions containing these compounds into healthy bean leaves. Of 15 plant species injected with an extract from lesions, Vicia faba appeared to be the most susceptible to damage.Evidence is presented to support the hypothesis that under conditions of low humidity the concentrations of toxic compounds in an infected leaf become high enough to kill healthy cells surrounding infected tissue. The dead tissue then dries out preventing further fungal growth and lesion spread. In saturated air, however, the toxic compounds diffuse throughout the lamina and become too dilute to kill uninfected tissue. Tissue does not become desiccated and the fungus continues to spread.
The disappearance of benomyl from mushroom casing
Authors: FLETCHER J. T. , CONNOLLY G. , MOUNTFIELD ELIZABETH I. , JACOBS L. 
Published: February 2008

SUMMARYThe failure of Benlate (50% benomyl) to control Mycogone perniciosa on mushroom farms where isolates of the organism were benomyl sensitive was investigated. A comparison was made of carbendazim levels, the major fungitoxic breakdown product of benomyl, in unsterilised casing, autoclaved casing and autoclaved casing mixed with a small proportion (1.7%) of casing previously treated with benomyl but from which all detectable levels of carbendazim had disappeared. Added benomyl was effective in controlling M. perniciosa in autoclaved casing, less effective in unamended casing and ineffective in the amended casing mixture. The recovery of carbendazim from these treatments was directly related to disease occurrence.Studies on farms where benomyl or other carbendazim generating fungicides had been used indicated that a lack of control of M. perniciosa was associated with the disappearance of fungicide from the casing before cropping began. This was not so on a farm where carbendazim generating fungicides had not been used before these investigations. Thiabendazole, a fungicide closely related to the carbendazim generators showed only a slight decline in concentration in casing capable of degrading benomyl.Bacteria isolated from the casing were examined in vitro for their ability to degrade benomyl. Five groups of bacteria were compared and three bacteria, Pseudomonas putida, Pseudomonas aeruginosa and an unidentified member of the Entero‐bacteriaceae were most able to degrade benomyl.
Genetic analysis of resistance to swede mildew
Authors: BRAIN P. J. , WHITTINGTON W. J. 
Published: February 2008

SUMMARYThe incidence of swede mildew (Erysiphe cruciferarum) was analysed on three occasions in five swede varieties Crifel, Doon Major, Harvester, Ne Plus Ultra and Ruta Øtofte and their F1 hybrids. Overall levels of infection were greater in Ne Plus Ultra and Harvester and least in Ruta Øtofte. Genetic analysis by the diallel method showed that initially resistance was recessive with Ruta Øtofte possessing most recessive genes but results from the final analysis showed partial dominance, with Ne Plus Ultra having most recessive and Harvester most dominant genes. The changing pattern of inheritance with time was due to variation in the rates of increase in disease incidence and diallel analyses of these rates, calculated by regression analyses over five observations, showed in almost entirely additive control. Although no variety was immune it was considered that except on soils of high pH or in the event of a marked change in the genetic composition of the pathogen the level of resistance in Ruta Øtofte was satisfactory.
Variation in germination and seedling emergence of sugar beet at sub‐optimal temperatures
Authors: BROWN S. J. 
Published: February 2008

SUMMARYPatterns of germination and seedling emergence at different temperatures were determined for a wide range of sugar beet accessions. There was good differentiation among seed lots and a close relationship between germination and emergence in temperature regimes of 20 h at 5 °C: 4 h at 7 °C, and constant 5 °C. Failure to germinate at temperatures between 5°C and 7 °C was more often associated with suppression of germination than with death of embryos. Results indicated that tests of germination at low temperatures would lead to more accurate predictions of field emergence than standard tests at 20 °C. Furthermore, tests at 20 °C may not give accurate estimates of potential viability.
Comparison of laboratory infection of aphids by Metarrhizium anisopliae and Verticillium lecanii
Authors: HALL R. A. 
Published: February 2008

SUMMARYThe pathogenicity of the only documented ‘aphid’ strain of Metarrhizium anisopliae for the aphid, Macrosiphoniella sanborni, was established by experimental infection. Its aphicidal potential was assessed by conducting parallel experiments with Verticillium lecanii, a fungus of proven efficacy in controlling aphids. The spore germination, growth and sporulation rates of M. anisopliae were slower than V. lecanii and were most likely the principal factors determining the higher LC., values in bioassay and slower propagation of this fungus amongst aphid populations. It is concluded that M. anisopliae, except perhaps in the salt marsh habitat from which it was originally isolated, would not prove as useful an agent as V. lecanii in biological control of aphids.
Properties of a carlavirus causing a latent infection of pepino (Solanum muricatum)
Authors: THOMAS WAYNE , MOHAMED N. A. , FRY MARGARET E. 
Published: February 2008

SUMMARYPepino (Solanum muricatum) cuttings imported from Chile contained a latent virus which was transmitted by inoculation of sap to Chenopodium quinoa but not to 21 other species. The virus was transmitted by the aphid, Myzus persicae. In C. quinoa sap, the virus lost infectivity when diluted between 10‐3 and 10‐4, heated for 10 min between 65 and 70 °C, or stored at room temperature for 4 to 6 days.The virus particles were straight or slightly flexuous filaments 660 to 680 nm long. Up to 15 mg virus per 100 g C. quinoa leaves was obtained by clarification with a mixture of chloroform and carbon tetrachloride. Purified preparations had Amax/Amin= 1.11, A260/A280= 1–30, A0.2601%= 2.8, and contained a single sedimenting component with a sedimentation coeficient of 149s and a buoyant density in CsCl of 1–318. The virus particles contained 5.5% of single‐stranded RNA of mol. wt 2.4×106 (estimated by gel electrophoresis of undenatured RNA) and sedimentation coefficient 38.5S, and a single polypeptide of mol. wt 33 000.The virus is distantly serologically related to potato S and carnation latent viruses and is considered a new member of the carlavirus group. The name pepino latent virus is proposed. The cryptogram for this virus is R/1: 2.4/5–5: E/E: S/Ve/Ap.