bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of water potential and temperature on the development of eyespot lesions in wheat
Authors: HIGGINS S. , FITT B. D. L.
Published: February 2008

Growth of Pseudocercosporella herpotrichoides on potato dextrose agar at water potentials from ‐0.5 to ‐6.9 MPa was optimal at 20°C. At 12 and 20°C, six isolates of P. herpotrichoides grew more rapidly at ‐0.5 to ‐2 MPa than at ‐6.9 MPa. Wheat plants inoculated with P. herpotrichoides and grown in columns of soil at either 15 or 20°C developed more severe eyespot lesions under a heavy watering regime than under medium or light watering regimes. P. herpotrichoides penetrated leaf sheaths of inoculated plants grown in compost more rapidly at 10°C night/15°C day temperatures than at 5/10°C; death of leaf sheaths was also more rapid and consequently there were fewer living infected leaf sheaths at 10/15°C than at 5/10°C. Irrigating for 5 wk before harvest increased the severity of eyespot lesions in a 1983 wheat crop.
Studies of the antagonistic activities of bacteria endemic to cereal seeds.
Authors: ADETUYI F. C. , CARTWRIGHT D. W.
Published: February 2008

The antagonistic activities in vitro of cereal seed‐coat isolates of Pseudomonas syringae and a member of the Erwinia herbicola group towards a wide range of plant pathogenic fungi were assessed quantitatively using a novel, agar‐based bioassay technique. When compared with the conventional streak bioassay technique, the new method, involving the use of concentric rings of bacterial inoculum, was found to have several advantages. Within 36 h of inoculation, isolates of both bacteria caused substantial, and at times complete, inhibition of the mycelial growth of almost all pathogens tested. Studies of the relationships between bacterial growth, the proximity of the bacterial ring to the fungal colony, and the levels of inhibition of mycelial growth, suggested that antagonism was primarily the result of the active production of antimycotic toxins by both bacteria, and indicated their potential as biological control agents for plant disease.
Viruses associated with chlorotic rosette and green rosette diseases of groundnut in Nigeria*
Authors: REDDY D. V. R. , MURANT A. F. , DUNCAN G. H. , ANSA O. A. , DEMSKI J. W. , KUHN C. W.
Published: February 2008

Groundnut (Arachis hypogaea) plants from Nigeria with chlorotic rosette disease contained a manually transmissible virus, considered to be a strain of groundnut rosette virus (GRV(C)). GRV(C) infected nine out of 32 species in three out of nine families. It caused local lesions without systemic infection in Chenopodium amaranticolor, C. murale and C. quinoa, and systemic symptoms in Glycine max, Nicotiana benthamiana, N. clevelandii and Phaseolus vulgaris as well as in groundnut. Some ‘rosette‐resistant’ groundnut lines were also infected. GRV(C) was transmitted by Aphis craccivora, but only from groundnut plants that were also infected with an aphid‐transmissible second virus, which was not manually transmissible and was considered to be groundnut rosette assistor virus (GRAV). Plants infected with GRAV contained isometric particles c. 25 nm in diameter which were detectable by immunosorbent electron microscopy on grids coated with antisera to several luteoviruses, especially with antisera to bean leaf roll, potato leafroll and beet western yellows viruses. No virus‐like particles were observed in extracts from plants infected with GRV(C) alone.

A single groundnut plant obtained from Nigeria with symptoms of green rosette contained luteovirus particles, presumed to be of GRAV, and yielded a manually transmissible virus that induced symptoms similar to those of GRV(C) in C. amaranticolor but gave only mild or symptomless infection of N. benthamiana and N. clevelandii. It was considered to be a strain of GRV and designated GRV(G).
The feasibility of producing inbred rather than F1 hybrid cultivars in Brussels sprouts: a preliminary genetical analysis and choice of material for inbreeding
Authors: SMITH B. M. , ROGERS W. J. , KEARSEY M. J.
Published: February 2008

The feasibility of producing commercially acceptable inbred lines of Brussels sprouts is investigated. Two experiments are described which examined the nature and extent of heterosis in this crop using the techniques of biometrical genetics. They indicate incomplete dominance for several production traits, lower F1 uniformity and the presence of inbreds that outyield some F1's. These results strongly suggest that recombinant inbred lines, possibly outyielding the better F1's could be produced. Five crosses were identified for inbreeding by SSD and 1000 lines are being produced from each. The principles upon which these crosses were identified are described.
Growth and sporulation of Oidium begoniae: development of a deterministic model
Authors: QUINN JAMES A. , JR. CHARLES C. POWELL
Published: February 2008

Growth and sporulation of Oidium begoniae (begonia powdery mildew) on detached leaves was observed daily under a stereomicroscope. A mathematical model of growth and sporulation was constructed based on the patterns observed. The essential components of the model are three genetically fixed components of colony growth and sporulation and six components which changed with environmental and physiological conditions. The genetically fixed components were: the ultimate number of germ tubes, the hyphal growth unit (HGU or mean length supporting one branch), and the diurnal periodicity of sporulation. These components were shown to have approximately the same values at 15 and 21 °C. Components which varied with temperature were: the latent periods of germination, branching and sporulation, the time taken to reach the ultimate germ tube number, and the number of conidiophores per HGU, The derived equations were tested against observed sporulation and resulted in highly significant correlations. Similar results were obtained with published observations for Erysiphe graminis f. sp. hordei. This colony‐level model can be used as units to construct models of disease progress and suggests that it is theoretically possible to model disease in the field from laboratory studies. The model can be used in computer simulations of colony growth as demonstrated by a computer program in the Appendix.
The colonisation of fallen apple leaves by Phytophthora syringae in relation to inoculum levels in orchard soil
Authors: HARRIS D. C.
Published: February 2008

Freshly abscissed apple leaves were rapidly infected after inoculation with zoospores of Phytophthora syringae. Mesophyll was extensively colonised within 4 days, sporangia and sex organs were formed within 9 days, but oospore maturation took several weeks. Oospores developed abundantly in leaves of all nine apple cvs tested.

The ability of P. syringae to colonise leaf tissue diminished rapidly as leaves senesced, was prevented if leaves were first killed by freezing or desiccation, but was unaffected by watersoaking leaves before inoculation.

Of nine soil samples from five apple orchards analysed for P. syringae by dilution and baiting, seven contained from 7–16 infective units/g, one contained significantly more at 34 units/g and one was even more infectious but unquantifiable. These differences of inoculum content of soils, which were only partially corroborated by successive baitings of bulk soil through leaf fall, are discussed in relation to the timing of leaf fall, the activity of P. syringae and rainfall.
Sampling potatoes for the incidence of tuber diseases and levels of inoculum
Authors: ADAMS M. J. , HIDE G. A. , LAPWOOD D. H.
Published: February 2008

In three years, between three and six seed stocks of cv. Pentland Crown were planted in field experiments. Seed tubers, stem bases and progeny tubers from the growing crop and tubers at harvest and after storage were sampled intensively and estimates of inoculum and disease made for five principal tuber diseases: the blemishes skin spot (Polyscytalum pustulans), silver scurf (Helminthosporium solani) and black scurf (Rhizoctonia solani) and bacterial soft rot (Erwinia carotovora).

The data were principally used to calculate sample variances after transformation of % values to logits. A variance of 0.010 was selected as giving acceptable accuracy for most purposes and to achieve such values substantial numbers of samples would have been needed. Five to ten 50‐tuber samples of seed tubers or 15–20 samples of a harvested or stored crop would have been required for assessing disease symptoms and similar numbers of samples for assessing gangrene potential by a standard damage test. The eye plug test for assessing inoculum of the three blemishing diseases used 15 or 20‐tuber samples and five such samples of seed or about ten from the growing crop would usually have been adequate. Variances were nearly always greater for black scurf assessments than for other blemishing diseases.

The data also illustrated changes in inoculum and disease levels during the season and in store. Their significance for understanding the epidemiology of the diseases and for storage disease forecasting is discussed.
Effects of three rates of aldicarb and of different degrees of resistance and tolerance in potato cultivars on yield and post‐harvest population densities of the potato cyst nematodes Globodera rostochiensis and G. pallida
Authors: TRUDGILL D. L. , MATHIAS P. L. , TONES S. J.
Published: February 2008

Three field experiments were made to determine the effectiveness of small‐plot trials in detecting differences between potato cultivars/clones in their tolerance of damage by potato cyst‐nematodes. A nematicide (aldicarb) was applied at three rates to decrease nematode damage. The largest rate of aldicarb increased tuber yields most but the relationship between yield response and nematicide rate was not linear. The yield increases of the cultivars and clones differed, indicating that they have different degrees of tolerance of potato cyst nematodes. The results were analysed in several ways and the untreated yield as a proportion of the treated provided the best means of expressing and comparing tolerance; but whichever method was used the tolerance rankings of the cultivars and clones were similar.

At two sites infested with Globodera rostochiensis, the rankings of the 10 cultivars and clones were similar but at a third site, heavily infested with G. pallida, they were different. Aldicarb decreased the nematode population density after harvest at the G. pallida site but was less effective at the G. rostochiensis sites, which were less heavily infested. Growing resistant or partially resistant potatoes usually prevented nematode increase, and the more resistant cultivars and clones decreased population densities markedly.
Seed survival and seasonal emergence in some species of Geranium, Ranunculus and Rumex
Authors: ROBERTS H. A. , BODDRELL JUNE E.
Published: February 2008

Seeds of 14 species were collected, usually in each of 2 or 3 yr, and mixed with the top 7.5 cm of sterilised soil confined in cylinders sunk in the ground outdoors and cultivated three times yearly. Seedling emergence was recorded for at least 3 and usually 5 yr. Most seedlings of Ranunculus bulbosus and Rumex acetosa appeared during the autumn of sowing, while the main emergence of Geranium pratense. Ranunculus acris, Rumex conglomeratus and R. maritimus was in the following spring. Emergence of G. pyrenaicum and G. robertianum took place throughout much of the year after sowing. Seeds of all these species were relatively short‐lived in cultivated soil, and few seedlings appeared after the second year.

Seed survival was greater in G. dissectum. G. molle, Rumex acetosella. Ranunculus sceleratus and especially R. repens, of which emergence in the fifth year after sowing amounted to 4% of the seeds sown. Emergence from the persistent seed bank was mainly from May to September for G. dissectum and G. molle and during autumn for Ranunculus flammula and R. sceleratus, while seedlings of Ranunculus repens and Rumex acetosella appeared sporadically over most of the year.
A simple model relating yield loss to weed density
Authors: COUSENS ROGER
Published: February 2008

A simple model is developed to describe crop yield loss as a function of weed density. The model, a rectangular hyperbola, has two agronomically meaningful parameters which together can be used as indices of competitiveness. Examples are given where the model is fitted to experiments from the literature. Seventeen other models are compared through application to 22 data sets. It was found that for the data available two‐parameter yield loss models were generally sufficient.

The hyperbolic model gave the best description of data, but this was only marginally better than three other models. This conclusion is discussed with reference to the popular sigmoidal model.
The effect of cultivation system and soil factors on the performance of herbicides against Alopecurus myosuroides
Authors: MOSS S. R.
Published: February 2008

Aspects of chemical and cultural control of Alopecurus myosuroides (blackgrass) in winter wheat were studied on a naturally‐occurring infestation over a 3‐yr period. In two experiments a comparison was made between ploughing and direct drilling, whilst in the third experiment direct drilling alone was used. Straw was spread and burnt in each year. Herbicide treatments were: chlortoluron and isoproturon in all three experiments; diclofop‐methyl and pendimethalin in two experiments; metoxuron, terbutryne, tri‐allate, carbetamide, propyzamide, chlorsulfuron + methabenthiazuron and trifluralin + linuron in one experiment. Herbicides were applied either pre‐emergence, early post‐emergence or late postemergence to separate sub‐plots. Surface soil (0–2.5 cm) samples were collected each year from unsprayed areas and used for soil analyses and for herbicide activity studies in pot experiments.

Ploughing resulted in much lower populations of A. myosuroides than direct drilling. Most herbicides gave much better control of A. myosuroides in ploughed than in direct drilled soil in field and pot experiments, regardless of application time. Diclofop‐methyl, applied early post‐emergence at 1.13 kg a.i./ha, was the only herbicide treatment in field experiments to achieve over 90% weed control in direct drilled soil. Differences in adsorption between soils given different cultivations, determined as Kd values for chlortoluron and isoproturon, were much greater than differences in organic matter.

The much greater adsorptive capacity of direct drilled soil, and consequently the poorer performance of all soil‐acting herbicides, was attributed to the concentration of burnt straw residues near the soil surface.
Potential for biological control of tent building species of ants associated with Phytophthora palmivora pod rot of cocoa in Papua New Guinea
Authors: MCGREGOR A. J. , MOXON J. E.
Published: February 2008

The tents of different ant species collected from young cocoa trees in their first or second year of bearing and free from visible pod rot, were tested for the presence of Phytopthtora palmivora by inoculating wounded cocoa pods with tent material.

Tents of all species harboured viable P. palmivora but those consisting mainly of soil were more frequently positive than plant debris‐type tents. Although Anoplolepis longipes, a dominant, ground nesting, non‐tent building species sometimes transported inocula in the laboratory, it did not significantly increase black pod infection in the field. Trees infested with the dominant debris tent building species, Technomyrmex albipes, however, had significantly more black pod than those infested with A. longipes or trees without ants. A. longipes forms dense populations and can exclude other dominant ants and some cocoa pests; its introduction may be a potentially economical method of reducing the transmission of P. palmivora in redeveloped cocoa in Papua New Guinea.
The relation between some growth parameters and yield components of rice as influenced by nitrogen level and genotype
Authors: RAHMAN M. S.
Published: February 2008

The effects of three levels of nitrogen (0, 2 and 4 g (NH4)2SO4 per pot) were evaluated in four rice varieties, differing in grain size, under flooded conditions in a tropical environment.

Addition of nitrogen increased plant height and leaf number on the main culm, and hastened flowering significantly in all varieties. It also increased the dry weights of leaf, and culm plus sheath at the maximum tillering stage, anthesis and harvest. The average dry weights of both leaf, and culm plus sheath increased significantly in all varieties until anthesis. Following anthesis, the dry weights of both leaf, and culm plus sheath of the large‐seeded varieties, Zhu Lian and PP6R, further increased mainly due to emergence of the late tillers, but decreased in the small‐seeded varieties, IR 747 and P3C26. During grain‐filling, vars Zhu Lian and PP6R accumulated dry matter more than the other two varieties and did not use their reserve starch present in the culm plus sheath, presumably because of the lack of demand. By contrast, current photosynthesis and ‘reserve’ contributed about 70% and 30%, respectively, of the grain yield in IR 747 and P3C26.

Addition of nitrogen increased grain yield significantly in all varieties. The yield increase in IR 747 and PP6R was essentially due to increase in grain number, but that in P3C26 and Zhu Lian was due to increases in both grain size and grain number, the latter having much greater influence. Neither the percentage of filled spikelets nor the 1000‐grain weight was influenced by nitrogen addition. It was concluded that grain number is the single most important yield component in rice. Path‐coefficient analysis indicated that in a breeding programme involving these four rice varieties, the cross between Zhu Lian and P3C26 would be most successful in an effort to combine high spikelet number and large grain size.
Increase in esterase activity during maturation of Malus pumila fruit
Authors: GOODENOUGH P. W. , RILEY T. E. W.
Published: February 2008

In a range of dessert cultivars of Malus pumila, the esterase in the fruit showed a rise in activity during the period of fresh weight gain. This was the case when activity was expressed on a protein or a fresh weight basis. Both fruit which matured at 100 days after anthesis, and fruit which matured later, showed a similar rate of increase. However, a cultivar used for processing rather than eating showed a much reduced rate of esterase increase.
The effects of nitrogen and sulphur nutrition on the response of Brussels sprout plants to infestation by the aphid Brevicoryne brassicae
Authors: KORITSAS V. M. , GARSED S. G.
Published: February 2008

The effects of two levels each of nitrogen and sulphur nutrition and of infestation by Brevicoryne brassicae on the growth of Brussels sprout plants were studied in factorial experiments.

All the plants receiving high nitrogen treatments grew more rapidly than those with low, but in infested plants the improvement in growth at the higher levels of nitrogen was offset by the increased size of aphid populations. Low sulphur nutrition increased the growth of plants receiving high nitrogen and of the aphids feeding on them. Leaf diffusive resistances and chlorophyll concentrations were greater with high nitrogen, but were significantly lowered by infestation in all nutrient treatments. Infestation decreased leaf total nitrogen concentration at the sites of feeding, but effects on soluble nitrogen were not significant. Removal of aphids 72 days after initial infestation did not cause marked plant recovery during the next 22 days.

It is concluded that the benefits of increased yield resulting from high nitrogen levels must be balanced against the greater potential for damage by aphids.
The distribution and abundance of predatory Coleoptera overwintering in field boundaries
Authors: SOTHERTON N. W.
Published: February 2008

Soil samples were taken over the period December ‐ February in 1981‐82 and in 1982‐83 from four types of field boundaries on farmland in Hampshire to estimate the distribution and abundance of overwintering polyphagous predatory Coleoptera. Supplementary data were obtained from surface searches in four types of field boundaries on farmland in Essex. Different species of predators occurred in significantly higher numbers in specific types of field boundaries but in Hampshire, hedge banks and shelterbelts were more attractive as overwintering sites than grass banks or grass strips for most species and in Essex a combined grass bank, ditch and hedge boundary was more suitable than other boundary types for three of the four species studied.
Effect of undersowing potatoes with grass on potato aphid numbers
Authors: McKINLAY R. G.
Published: February 2008

The numbers of the potato aphids, Macrosiphum euphorbiae and Myzus persicae, were counted on potatoes undersown and not undersown with perennial ryegrass in field experiments during 1980 and 1981. The numbers of aphids on potatoes undersown with grass were found generally to be smaller than the aphid numbers on potatoes not undersown with grass. Tuber yields were not significantly reduced by the undersowing of potatoes. The agronomic feasibility of undersowing potatoes for aphid control is discussed.
Infection of red raspberry styles and carpels by Botrytis cinerea and its possible role in post‐harvest grey mould
Authors: McNICOL R. J. , WILLIAMSON B. , DOLAN ALISON
Published: February 2008

The gynecium was selected for histological studies of infection of red raspberry (Rubus idaeus) flowers in the laboratory because it is one of several possible infection sites leading to fruit grey mould. Infection of emasculated flowers occurred when dry conidia were dusted on to receptive stigmas. The conidia germinated in the stigmatic fluid of both non‐pollinated flowers and flowers pollinated before inoculation, their germ tubes then penetrated the stigma and hyphae grew intercellularly through the transmitting tissues of the style to enter the carpel within 7 days. The possible roles of stylar infections and endophytic mycelium are discussed in the context of grey mould development.
The effect of magnesium ions on the solubility of polyhedral inclusion bodies and its possible role in the inactivation of the nuclear polyhedrosis virus of Spodoptera littoralis by the cotton leaf gland exudate
Authors: ELLEMAN C. J. , ENTWISTLE P. F.
Published: February 2008

Polyhedral inclusion bodies of Spodoptera littoralis nuclear polyhedrosis virus (NPV) treated with solutions of cotton leaf gland exudate (a process which has been shown to inactivate the NPV), exhibited a marked decrease in solubility in dilute alkali. This process is reversible with EDTA and can be simulated by MgCI2. The effect of magnesium ions on solubility did not involve the enzyme, alkaline protease. It is suggested that this decrease in solubility may be involved in the mechanism by which the cotton leaf inactivates the NPV. However, since MgCI2 alone could not be shown to inactivate NPV in vitro it must be assumed that other constituents of the leaf gland exudate also play a part.
Biological and biochemical properties of an isolate of cherry rasp leaf virus from red raspberry
Authors: JONES A. T. , MAYO M. A. , HENDERSON SUSAN J.
Published: February 2008

A mechanically transmissible virus obtained from symptomless plants of a red raspberry selection imported into Scotland from Quebec, Canada was indistinguishable serologically from a cherry isolate of cherry rasp leaf virus (CRLV). The raspberry isolate, CRLV‐R, was graft transmitted to several virus indicator species and cultivars of Rubus without inducing noticeable symptoms. In Chenopodium quinoa sap, CRLV‐R lost infectivity after dilution to 10‐5 or heating for 10 min at 60°C but was infective after 16 days (the longest period tested) at 18°, 4° or ‐ 15°C. The virus particles are isometric, c. 28 nm in diameter, and were purified with difficulty from infected C. murale and C. quinoa plants. The particles comprise two nucleoprotein components with sedimentation coefficients of 89 and 115 S and are prone to aggregate during purification. When centrifuged to equilibrium in CS2SO4 solution, purified virus preparations formed two major components with p= 1·28 and 1·36 g/cm3. Virus particles contained two RNA species which, when denatured in glyoxal and electrophoresed in agarose gels, had estimated mol. wt of 2·56 × 106 (RNA‐1) and 1·26 × 106 (RNA–2). Infectivity of CRLV‐R RNA was abolished by treatment with proteinase K, suggesting that the RNA is linked to protein necessary for infectivity; RNA molecules contained polyadenylate. In reticulocyte lysates, CRLV‐R RNA stimulated the incorporation of 3H‐leucine, mainly into two polypeptides of estimated mol. wt 200 000 and 102 000. When electrophoresed in polyacrylamide gels, protein obtained from CRLV‐R particles purified by centrifugation to equilibrium in Cs2SO4 separated into three bands with estimated mol. wt 26 000, 23 000 and 21 000.
An analysis of leaf growth in sugar beet.
Authors: MILFORD G. F. J. , POCOCK T. O. , RILEY JANET
Published: February 2008

The influence of season, and certain agronomic treatments (irrigation, nitrogen fertiliser, density of planting and sowing date) on leaf number were analysed in a series of sugar‐beet crops grown during the five seasons 1978‐82. Leaf appearance was a linear function of thermal time (accumulated temperature above 1°C) and could be described by four variables: a) the thermal duration of the seedling establishment phase, d′s; b) the thermal time interval between appearance of each of the early leaves, θe; c) the thermal duration of the early phase of leaf appearance, d'a, and d) the thermal time interval between the appearance of each of the later leaves, θ1. The progression of leaf death could also be described by a thermal time interval, θd.

There were only small differences in the number of leaves produced by the eleven crops grown during the five seasons. Such differences as appeared, were largely attributable to changes in d'a and θ1, which were interpreted as responses to increasing competition for mineral nutrients and assimilate at the shoot apex. θe was similar in all crops; 30°Cdays were needed between the appearance of each of the early leaves. Only the early leaves died. Each one was retained by the plant longer than its predecessor. Increasing soil moisture deficit under an unirrigated crop shortened θd and depriving crops of nitrogen lengthened it. It is concluded that small differences in the rates of leaf appearance did not greatly influence the rates at which leaf canopies expanded early in the season, but that the rates of leaf death influenced both the time at which the canopies reached their maximum sizes and the rates at which leaf areas subsequently declined.
An analysis of leaf growth in sugar beet.
Authors: MILFORD G. F. J. , POCOCK T. O. , RILEY JANET , MESSEM A. B.
Published: February 2008

The expansion and persistence of leaves of sugar beet (Beta vulgaris) were measured in a series of crops grown in five seasons between 1978‐82 to establish how their growth varied between seasons, was affected by certain agronomic treatments and contributed to changes in leaf area index. Thermal time (accumulated temperature above 3°C) rather than days from sowing was used as a basis for comparing growth in different seasons.

Leaf size depended on position on the stem and was influenced by sowing date, nitrogen fertiliser rate, plant population and the development of crop water stress. Changes in size were mostly associated with changes in the rates, rather than the duration, of expansion. When compared across seasons, the rate and duration of expansion of individual leaves were strongly negatively correlated so leaf size tended to be a more stable characteristic than either of its determining components. Nevertheless, final leaf areas varied by as much as 20% between seasons and this variation was attributable more to the temperatures experienced by leaves prior to unfolding and to the amounts of nitrogen present in the shoot at that time than to conditions during the main period of leaf expansion.
Preliminary laboratory tests with two species of entomophilic nematodes for control of Musca domestica in intensive animal units‡
Authors: RENN N. , BARSONf G. , RICHARDSON P. N.
Published: February 2008

Two species of entomophilic nematodes, Heterorhabditis heliothidis (NZ strain) and Steinernema feltiae (Agriotos strain) were tested in the laboratory against immature and adult stages of a strain (G) of Musca domestica with multiple insecticide‐resistance. Both species of nematodes killed larval stages of M. domestica on inoculated filter papers. S. feltiae was the most virulent parasite, and killed >90% of all larval stages at the two highest doses of 25 000 and 50 000 nematodes per 0·5 ml tap water. No puparia were parasitised by either species. There was no parasitism of the larval stages after exposure to chicken manure treated with nematodes. All adult flies were parasitised after they were exposed to bait‐pads previously inoculated with S. feltiae, 93.3% were parasitised by H. heliothidis.
Apple mosaic virus isolated from hop plants in Japan
Authors: SANO T. , SASAKI M. , SHIKATA E.
Published: February 2008

A strain of apple mosaic virus was isolated from hop plants in Japan. The virus was purified from young hop plants and back‐inoculated to virus‐free hop plants obtained by meristem tip culture. Inoculated plants developed chlorotic spots, ringspots and a band pattern accompanied by necrosis in the inoculated and systemically infected leaves. Shoot tips of infected plants sometimes became necrotic and these symptoms resembled those of a ring‐ and band‐pattern mosaiclike disease prevalent in hop gardens in Japan. Since apple mosaic virus was recovered from infected plants, it is likely that the virus was the causal agent of this disease.

Agar gel double diffusion tests and ELISA showed the hop virus to be serologically closely related to apple mosaic virus (ApMV), and distantly related to prunus necrotic ringspot virus (PNRSV).

The virus had a narrow host range, and infected only cucumber of 18 species of Cucurbitaceae, Chenopodiaceae, Leguminosae or Solanaceae inoculated. It produced chlorotic spots on the inoculated cotyledons of cucumber, but no systemic infection. By contrast, ApMV from apple and PNRSV from peach had wide host ranges and infected cucumber plants systemically.
The influence of cultivar and isolate on the susceptibility of red raspberry canes to Didymella applanata
Authors: PEPIN H. S. , WILLIAMSON B. , TOPHAM PAULINE B.
Published: February 2008

The internodes of young canes of a single red raspberry selection were inoculated in the field with 32 isolates of Didymella applanata from diverse localities throughout the British Isles. All isolates were pathogenic but differed in virulence estimated by lesion length; their origin and virulence were not related.

Four petioles on young canes of seven cultivars were inoculated in the glasshouse with 13 of the isolates. The axillary buds at treated nodes were shorter and the emergence of lateral shoots was substantially less than at non‐inoculated nodes in all seven cultivars. Although there were significant cultivar × isolate interactions, these were small in comparison to the effects of inoculation, cultivar and position of the treated node.

The cultivar × isolate interactions between eight cultivars and 14 isolates were also studied in the field by inoculation of petioles and the internodes of young canes. Joint regression analysis of bud and lesion lengths revealed significant cultivar × isolate interactions but no discontinuous variation in the expression of disease was found. A principal components analysis using % nodes infected, % reduction in bud length and % lateral shoot failure confirmed the relationship between these variates and gave three vectors. The first (83.3% of variation) named the ‘resistance’ vector described the relative resistance or susceptibility of cultivars, the second ‘tolerance’ vector (13.4%) described the variation due to relative tolerance or intolerance of these genotypes and the third a ‘bud response’ vector accounted for only 3.3% of the variation.
Relationships between seed weight and endosperm characteristics in carrot
Authors: GRAY D. , WARD J. A.
Published: February 2008

Carrot seed weight, over the range 0·37 to 3·77 mg, and endosperm volume were closely and linearly related to endosperm cell number, the relationships accounting for 77–85% and 84–94% of the variance in seed weight and endosperm volume, respectively. The relationships were similar for seeds of cvs Chantenay and Amsterdam, and for seeds from primary and secondary umbels but were affected by season of seed production through differences in cell volume.
Estimation of cold hardiness of Douglas‐fir and Engelmann spruce seedlings by differential thermal analysis of buds*
Authors: TINUS R. W. , BOURQUE J. E. , WALLNER S. J.
Published: February 2008

Low temperature freezing points of conifer buds were determined by differential thermal analysis and were compared to results obtained in whole plant freezing tests of the same seedlings. To obtain well‐defined, meaningful exotherms, it was necessary to nucleate buds externally. The low temperature exotherms for buds occurred at temperatures very close to the lowest which seedlings tolerate with no visible injury. Thus, for Engelmann spruce and Douglas‐fir, differential thermal analysis may provide a convenient prediction of containerised tree seedling hardiness.
A selective medium for isolating Rhizoctonia solani from soil
Authors: GANGOPADHYAY SAMIRAN , GROVER R. K.
Published: February 2008

Ko & Hora's (1971) selective medium (FM) for counting Rhizoctonia solani propagules from soil has been modified. FM medium minus gallic acid and fenaminosulf i.e. mineral antibiotic (MA) medium, was amended with inhibitors and fungicides at different concentrations. The modified medium consisting of MA + gallic acid (400 μg ml‐1) + fosetyl‐Al (250μgml‐1) was found most efficient in selective isolation of R. solani from soil even in the presence of Macrophomina phaseolina (Rhizoctonia bataticold) and other soil mycoflora.

This amended medium was effective in isolating R. solani from soil even when the number of propagules of M. phaseolina present was 10 times greater. The sensitivity of this medium was five times better than Ko & Hora's medium.
Stem canker (Rhizoctonia solani) of maincrop potatoes.
Authors: HIDE G. A. , READ P. J. , SANDISON JANET P.
Published: February 2008

In two years, potato plants were sampled at 1‐ or 2‐ weekly intervals from plots planted with seed tubers bearing sclerotia of Rhizoctonia solani (black scurf) and with seed without sclerotia either infested or not with cultures of R. solani at planting. Sprouted King Edward seed was used in 1981 and sprouted and non‐sprouted King Edward and Pentland Crown seed in 1982.

In both years 60–80% of shoots from seed with sclerotia and 90% of shoots from seed inoculated at planting were affected with stem canker. Most disease developed before shoots emerged although it gradually increased later when new shoots arising both from seed tubers or as branches on shoots with damaged apices (pruned shoots) became infected before they emerged. Sprouting seed tubers bearing sclerotia decreased the disease on both cultivars but with soil‐applied inoculum the disease was more severe on plants from sprouted than non‐sprouted seed.

Some stolons were infected by R. solani soon after they developed and incidence of infection later increased. Thirty to 50% of stolons were infected on plants from infected seed tubers and 60% on plants with soil‐applied inoculum. With both cultivars and sources of inoculum about 70% of the infected stolons had their apices killed (pruned).
Factors affecting the uptake of chlormequat into cereal leaves
Authors: BAKER E. A. , HUNT GRACE M.
Published: February 2008

The effects of site of application, growth environment, droplet size, and formulation adjuvants on the retention and uptake of 14C‐chlormequat by wheat cv. Avalon and barley cv. Sonja have been examined using solutions applied by a micro‐sprayer. Wheat plants retained a higher proportion of droplets on initial impaction than barley irrespective of growth stage, site of application or formulation. Leaf retention increased approximately two‐fold with increase in surfactant concentration (0·03·0–3% w/v) or decrease in droplet size (200‐125 μm) but declined markedly with age of leaf. Uptake, which was greater into wheat than barley, increased with increase in surfactant concentration, growth temperature and droplet size, with a combination of decrease in irradiance plus a rise in soil moisture, and after exposure to simulated dew. Droplet reflection increased and chlormequat uptake declined when the fungicide preparations Bavistin and Radar replaced Agral 90 in the spray mixtures. Droplets impacted more readily and spread more extensively over the damaged surfaces of field grown leaves. Both tissue combustion and autoradiography showed that chlormequat translocated readily only in immature tissues.
Grain aphid infestations of winter wheat variety trials, 1984
Authors: LOWE H. J. B. , ANGUS W. J.
Published: February 2008

Aphid infestations of wheat yield trials near Cambridge were assessed by shoot sampling and by breeder's scores. Both resistant and extremely susceptible cultivars were identified. Results from the two methods of assessing infestation were well correlated, indicating that the simpler scores could be used effectively for making selections.
The persistence of infectivity of conidia of the aphid pathogen Erynia neophidis on leaves in the field
Authors: BROBYN PATRICIA J. , WILDING N. , CLARK SUZANNE J.
Published: February 2008

Conidia of the aphid pathogen Erynia neophidis inoculated on to bean leaves in the field in 1980, 1981 and 1982, retained some infectivity for pea aphids for at least 14 days. Decline in infectivity occurred linearly with time. Inocula on leaves near the base of plants remained infective longer than those on leaves near the top and those on the abaxial surface remained infective for longer than those on the adaxial surface. Infectivity persisted longest in 1981 when conditions were coolest with least sun.
Spread of barley yellow dwarf virus and relative importance of local aphid vectors in central Washington
Authors: HALBERT SUSAN E. , PIKE K. S.
Published: February 2008

Data from bioassays of field collected aphids, barley indicator plants exposed to natural conditions, and various types of aphid traps were used to describe the spread of barley yellow dwarf virus (BYDV) in wheat and barley near Prosser, Washington. Bioassays were also used to assess the relative importance of local vector species.

Of alate aphids collected from grain in the 1982 and 1983 fall migration seasons, 3.4–14–5% transmitted BYDV. Data from concurrent and post‐migration assays of resident aphids (apterae and nymphs) reflected an increase in the proportion of infected plants in the field. Maximum increase in the percentage of viruliferous aphids occurred in late November and December of 1982 and November of 1983. The 1982 increase occurred after aphid flights had ceased for the year, suggesting active secondary spread. Collections in pitfall traps and infected trap plants from November to February confirmed aphid activity and virus spread.

Rhopalosiphum padi was the most important vector in central Washington in 1982 and 1983 because of its abundance and relative BYDV transmission efficiency. Metopolophium dirhodum was more winter‐hardy than R. padi and equal to R. padi in its efficiency as a vector; however, it was not as abundant as R. padi except during the mild winter of 1982–83, when it was a major contributor to secondary spread. Sitobion avenae may be important in years when it is abundant, but it was only a quarter as efficient as R. padi. Rhopalosiphum maidis was a much less efficient vector than R. padi and it only reached high populations in late autumn barley.
Deoxyradicinin and 3‐epideoxyradicinol production by the sunflower pathogen Alternaria helianthi
Authors: ROBESON DAVID J. , STROBEL GARY A.
Published: February 2008

The phytotoxic compound deoxyradicinin, a metabolite of Alternaria helianthi, was isolated from naturally infected leaves of sunflower (Helianthus annuus). The production of this toxin in liquid culture together with 3‐epideoxyradicinol is discussed. Production of deoxyradicinin by liquid cultures was observed to decrease after successive sub‐culture of the fungus on solid medium. All 10 accessions of Helianthus tested were sensitive to deoxyradicinin although some quantitative differences between lines were noted. Evidence is presented for the metabolism of deoxyradicinin by host leaf tissue.
A distinct strain of lucerne Australian latent virus in white clover in New Zealand
Authors: FORSTER R. L. S. , MORRIS‐KRSINICH B. A. M.
Published: February 2008

A strain of lucerne Australian latent virus (LALV) was widespread in Trifolium repens (white clover) in Northland, New Zealand, occurring in 20–100% of plants tested on 23 of 26 farms. Infected plants showed chlorotic line patterns or were symptomless. In agar gel double diffusion serological tests, white clover isolates of LALV differed from lucerne isolates by two or three twofold dilution steps of antisera. In mechanical inoculation tests, white clover isolates did not infect lucerne and lucerne isolates did not systemically infect white clover. White clover and lucerne isolates also differed in their reactions in some other hosts. Six LALV isolates from white clover were indistinguishable in double diffusion serological tests and by enzyme‐linked immunosorbent assay, although the isolates could be differentiated by some reactions in test plants. Purified LALV particles of lucerne and white clover isolates contained two nucleoprotein components and two RNA species of molecular weight 2.82 × 106 (8150 nucleotides) and 2.46 × 106 (7100 nucleotides) (estimated under denaturing conditions).
Some properties of an isolate of tobacco rattle virus from Northern Ireland
Authors: MILLS P. R.
Published: February 2008

A virus obtained from soil in which potato plants had shown severe spraing symptoms induced symptoms on indicator plants typical of tobacco rattle virus (TRY).

Purified virus preparations of a local‐lesion isolate contained particles of two modal lengths, 192 nm and 94 nm containing RNA molecules of mol. wt 2.4 × 106 and 1.23 × 106. Virus coat protein had a mol. wt of c. 21 500.

The virus was serologically distantly related to TRY (SYM) and pea early browning virus (PEBV) SP5, but did not react with TRY (CAM) or TRY (PRN) antisera. However, cDNA hybridisation indicated that the virus was more closely related to TRY (PRN) than either TRY (SYM) or PEBV (SP5).

The virus isolate has been designated TRY (NI).
Detection of maize rough dwarf virus by enzyme‐linked immunosorbent assay in plant hosts and in the planthopper vector
Authors: CACIAGLI P. , ROGGERO P. , LUISONI E.
Published: February 2008

SVPs were efficiently detected by ELISA in individual male and female insects. Females carried more virus per insect and per unit fresh weight, but no significant difference was detected between males and females in vector efficiency. Of insects positive in ELISA, 15–20% were unable to transmit the virus to host plants. Storage of viruliferous hoppers at‐20°C decreased the level of viral antigen detected by half in about 240 days.

Subviral particles (SVPs) of maize rough dwarf virus were detected in the planthopper vector Laodelphax striatellus and in maize and barley plants using double antibody sandwich ELISA. In purified preparations diluted in buffer, as little as 36 ng/ml of SVPs was detectable whereas after dilution in extracts of healthy frozen planthoppers the sensitivity was reduced to 50 ng/ml. Freezing the hoppers prior to extraction lowered to one third the background reading due to normal components. Neither the dissociated proteins of the SVP nor the viral double‐stranded RNA contributed to the ELISA readings.
Selection for Fusarium root rot resistance in red clover
Authors: RUFELT S.
Published: February 2008

Intercrossing red clover plants, selected for reaction to Fusarium root rot (F. avenaceum), produced progenies with lower root rot scores than the parental cultivar Hermes II. Eleven percent of the progenies had less than 2 mm root rot after two cycles of selection, compared to less than 1% in the parental cultivar. Root rot severity in two old local strains of red clover, as well as in two populations of wild red clover, was lower than in cv. Hermes II. This could indicate that a natural selection for root rot resistance can occur in red clover.
The influence of harvest maturity, calcium concentration and storage conditions on the keeping quality of Spartan apples grown in England
Authors: STOW J. , PERRING M. A. , JOHNSON D. S.
Published: February 2008

Spartan apples from several commercial orchards were stored in three successive years. The principal physiological disorders that developed were scald and core rowning. These disorders were minimised by picking at the end of September and storing in either 2% O2 or 2% CO2+ 2% O2 at 1.5°C. Fruit calcium concentrations were usually high enough to avoid flesh breakdown but could be increased without risk of skin damage by dipping in a 2% solution of calcium chloride.

It was concluded that storage of Spartan for up to 9 months is possible provided that fruit calcium concentrations are adequate and that picking date and storage conditions are optimised.
Variation in embryo size of inbred lines of carrot
Authors: DOWKER B. D. , GRAY D.
Published: February 2008

Mean embryo lengths and coefficients of variation (CVs) of embryo length of inbred carrot lines differed between years but not between the two sets of inbreds tested nor between male‐sterile and maintainer lines. Estimates of CVs were of similar magnitude to those previously obtained for experimental and commercial open‐pollinated seed lots, but estimates of mean embryo length were lower. Thus greater genetic uniformity did not lead to lower CVs of embryo size of the inbreds.
Genetic control of green curd colour in cauliflower
Authors: CRISP P. , ANGELL S. M.
Published: February 2008

A genetic model was fitted to observed curd colours in a segregating cauliflower population derived from crosses between white and green curded types. The model was of a gene (Wi wi) giving white dominant over yellow, and an independent codominant gene (gr1 gr2) for green‐ness.
Effects of bendiocarb and diflubenzuron on mushroom cropping
Authors: WHITE P. F.
Published: February 2008

When mixed into the casing or compost layers of a mushroom bed in the absence of pests, bendiocarb decreased yield and number of mushrooms according to concentration. The most severe effects were on mushroom number at the two highest rates used (100 and 1000 μg/g), and there were large increases in mushroom size. Effects of bendiocarb incorporation in the compost diminished with time, and there was partial compensation in yield and numbers at the fourth flush. The action of bendiocarb persisted when it was mixed into the casing.

Diflubenzuron showed some opposite effects at lower concentrations. When either mixed into, or drenched onto the casing at the commercial rate (30 μg/g), yield and size were both increased and the timing of the flushes was unaffected. At the two higher concentrations (180 and 1080 μg/g), reductions in yield and number and an increase in mushroom size were shown. However, these effects became more severe with time, especially those on mushroom number, possibly due to the accumulation of a toxic breakdown product.