bluuebunny/crossref_metadata_2025 huggingface dataset:
Serological relationship between cherry leaf roll, elm mosaic and golden elderberry viruses
Authors: JONES A. T. , MURANT A. F.
Published: February 2008

A virus obtained from plants of Sambucus canadensis imported from North America and another obtained from wild plants of Sambucus nigra growing in Perthshire, Scotland, were serologically identical to golden elderberry virus described from North America. They were serologically related to, but distinguishable from, cherry and rhubarb isolates of cherry leaf roll virus from Europe, and elm mosaic, another virus from North America.
Chemical treatment of soil to prevent transmission of tobacco rattle virus to potatoes by Trichodorus spp
Authors: COOPER J. I. , THOMAS P. R.
Published: February 2008

Of the chemicals tested in field experiments at two sites on sandy soil in Scotland, D‐D (dichloropropane‐dichloropropene) applied before planting at 200 or 400 Ib/acre (224 or 448 kg/ha) gave the best control of potato spraing disease caused by tobacco rattle virus (TRV); it almost eliminated the disease in the first year and greatly decreased the incidence in the second. Application in the autumn was more effective than in the spring.

Methomyl at 8 Ib/acre (9 kg/ha) and dazomet at 150 Ib/acre (168 kg/ha) greatly decreased the spread of TRV in the first year after treatment, but not in the second. These effects were closely related to the nematicidal effects of the chemicals on the nematode vectors (Trichodorus spp.), except that methomyl controlled virus spread more effectively than it killed Trichodorus. When data from plots treated with methomyl are excluded, spraing incidence was more closely correlated with the numbers of Trichodorus found in May than in September. In general, the infectivity of soil, estimated by infection of cucumber bait seedlings with TRV in pot tests, paralleled the incidence of spraing, but bait cucumber roots were infected more readily than potato tubers.

Application of D‐D at 200 Ib/acre (224 kg/ha) is probably worthwhile economically when potato cultivars that are susceptible and sensitive to TRV are to be grown on land infested with the virus.
Disk electrophoresis of proteins of Heterodera species and pathotypes of Heterodera rostochiensis
Authors: TRUDGILL D. L. , CARPENTER J. M.
Published: February 2008

The proteins extracted by aqueous buffer from the females of six Heterodera spp. were separated into bands by polyacrylamide gel electrophoresis and the patterns compared. Heterodera schachtii and H. trifolii, with lemonshaped cysts, had a similar pattern of bands, differing greatly from that of the round‐cyst nematodes H. virginiae and H. rostochiensis. Ten pathotype A populations of H. rostochiensis had similar patterns, distinguishable from those of twelve pathotype E populations by the absence of two bands and by the presence of another rarely found in pathotype E. Bands from pathotype B populations were indistinguishable from those of pathotype E. No consistent difference was detected between populations of the same pathotype. These results support the suggestion by Jones, Carpenter, Parrott, Stone & Trudgill (1970) that H. rostochiensis Woll. comprises two species.
Fireblight epidemic among Kentish apple orchards in 1969
Authors: GLASSCOCK H. H.
Published: February 2008

Evidence from field observations and orchard plans indicates that the fireblight epidemic among apples in 1969 followed a critical combination of weather conditions. There is little doubt that diseased hawthorns, situated entirely or mainly to the north‐west of the main lanes of infection, were the source of inoculum. Initial infection was confined to shoots. No blossom infection was seen at any time. Weather data from a nearby meteorological station point to distribution of inoculum having taken place on one of the days 6–10 July when strong winds, rainfall and hailstorms occurred. These days were followed immediately by temperatures above 18d̀C which are considered suitable for infection and for progress of the bacterium within the shoot tissues. The control measures advised were the removal and destruction of diseased parts, the disinfection of pruning implements, the protection of wounded surfaces against infection and the destruction of nearby diseased hawthorns.
Properties of inhibitors of plant virus infection occurring in the leaves of species in the Chenopodiales
Authors: SMOOKLER M. M.
Published: February 2008

Leaf extracts from twenty‐nine species of the Chenopodiales were shown to inhibit the infection of Phaseolus vulgaris by tobacco necrosis virus. The inhibitors were not lost on dialysis or by storage at ‐ 25 d̀C for 56 days. Partially dry lyophilized extracts kept at ‐ 25 d̀C for 2 years in unsealed screwtopped bottles retained inhibitory activity. The inhibitors in extracts of species of Beta, Halimione and Amaranthus were largely inactivated by heating for 10 min at 60–80 d̀C, but 80–100 d̀C was needed to inactivate those in sap of species of Chenopodium, Atriplex, Basella, Hablitzia, Salsola and Celosia. The extent of this inhibition of infection caused by unheated Chenopodium album sap depended on the virus‐host combination. With heated sap this dependence was changed.

The properties of inhibitors from extracts of Chenopodium amaranticolor, C. album, Atriplex nitens and Amaranthus caudatus were compared. Extracts made with water‐saturated phenol were not inhibitory and precipitation tests with 50% acetone, 50% ethanol and 2.5% trichloracetic acid suggested that the inhibitors are protein. Most inhibitory activity was precipitated from extracts by 70–90% saturated ammonium sulphate. Ion‐exchange column chromatography on CM‐Sephadex C‐25 showed that most inhibitory activity and protein was eluted by 0.4 M sodium acetate buffer. Disc electrophoresis indicated that several proteins occurred within the pooled inhibitory fractions. Gel filtration with Sephadex G‐200 suggested that the inhibitors have molecular weights of 25000–38000.

The four inhibitors are probably very similar, but not necessarily identical, basic proteins.
The microbiology of moist barley storage in unsealed silos
Authors: LACEY J.
Published: February 2008

The microflora of moist barley grain and whole‐crop barley silage stored in top‐unloading, unsealed concrete‐staved silos on six farms in England depended on the initial water content of the grain (23–58%), method of covering the grain, and the rate at which it was unloaded. Fungi and actinomycetes were fewest when the initial water content was more than 30%, and the grain was covered first with a layer of wilted grass, and then a plastic sheet. During unloading, the uppermost layer of grain remained in good condition provided 7.5 cm was removed daily.

With an inefficient top‐seal, the top grain heated and became mouldy, as it also did when unloading was slow. As the rate of unloading slowed, heating increased, and a characteristic succession of fungi and actinomycetes developed. With unloading at 7.5 cm/day or more, only yeasts, chiefly Endomycopsis chodatii Wickerham and Hansenula anomala (Hansen) H. & P. Sydow, were abundant, but at slightly slower rates of unloading Penicillium spp. also became common. Both these groups became less common as unloading was slowed further and were replaced, first by Absidia spp. and Mucor pusillus Lindt, then Aspergillus fumigatus Fres., Humicola lanuginosa (Griffon & Maublanc) Bunce, Micropolyspora faeni Cross, Maciver & Lacey, and Thermoactinomyces vulgaris Tsiklinsky as the heating increased. The number of spores (including bacterial cells) that could be removed from samples by blowing air ranged from 0.4–428 times 106/g dry weight of grain. Whole‐crop barley silage contained 2.9–132 times 106spores/g dry weight. Similar species were isolated from whole‐crop silage as from grain. Little moulding occurred deeper than 30 cm below surface of the grain.

Concentrations of airborne spores were estimated periodically during two seasons. There were always more airborne spores than is usual in outdoor air. Without disturbance the silos contained 106‐107 spores/m3 air, but when mouldy grain was unloaded concentrations increased to a maximum of 2860times106 spores/m3 air; more than half of these were bacteria and actinomycetes and a quarter Aspergillus flavus Link. Potentially pathogenic fungi and actinomycetes were frequent, particularly when they also occurred in the grain or capping materials for spontaneous heating. Some probably survived in dust deposits and were resuspended during unloading. Airborne spores were frequent around the silos when grain was unloaded and rolled. Workers should wear efficient dust respirators at these times and while inside silos.
The infection of potatoes by Phoma exigua
Authors: ENTWISTLE A. R.
Published: February 2008

The pathogenicities of Phoma exigua var. foveata and P. exigua var. exigua were compared by determining the relationship between incidence of infection of whole tubers or tuber pieces and various inoculum levels in soil. In natural soil var. foveata was more pathogenic than var. exigua, but in sterilized soil there were no clear differences between the two. Both varieties were isolated from some lesions derived from inoculum to which only one variety had been added indicating either natural contamination of soil or latent infection in tubers; the proportion of such lesions increased at the lower inoculum concentrations.

In studies where potato plants were grown in infested soils, the incidence of stem disease and tuber disease increased at increased inoculum concentrations of var. foveata; var. exigua was not added to the inoculum but was isolated from some lesions, the proportions of such lesions again increasing at lower inoculum concentrations. The infectivity of the infested soil, assessed by a tuber‐baiting method, declined soon after planting but increased prior to harvest.

Laboratory studies indicated that in natural soil the infectivity was highest after 2–3 months and lowest after 10 months incubation, but in sterilized soil infectivity was highest after 5 months and lowest after 7 months incubation.
Phenology and fungus‐nematode relations of corky root disease of Douglas‐fir
Authors: BLOOMBERG W. J. , SUTHERLAND JACK R.
Published: February 2008

Symptoms of corky root disease of Douglas‐fir seedlings include: (I) swollen tap‐ and lateral roots; (2) paucity of lateral roots; and (3) stunted shoot growth. In diseased roots, the primary cortex persisted and enlarged, but secondary vascular tissues, periderm, pericycle and endodermis were reduced. Cylindrocarpon destructans was the fungus most frequently isolated from cortical cells and symptoms were induced by massive inoculum of some isolates but not by dispersed inoculum nor by extracts from cultures. Whereas symptoms first appeared 2 months after seeds sown in May germinated, C. destructans was rarely isolated until 4 months after germination. Relatively more colonies of C. destructans were isolated from corky roots in the winter than in the summer, when Fusarium oxysporum or Mycelium radicis atrovirens were more abundant. Populations of the plant‐parasitic nematode Xiphinema bakeri on roots and in adhering soil were highest 2 months after germination and during the summer, correlating positively with the per cent of tap‐root affected and negatively with numbers of lateral roots.
Transpiration in potato plants infected with Verticillium spp
Authors: HARRISON J. A. C.
Published: February 2008

Potato plants (cv. King Edward) infected with Verticillium albo‐atrum and with V. dahliae transpired more slowly than healthy plants; this difference increased as the disease progressed. Diurnal fluctuations in transpiration were smaller in infected plants than in controls because infection markedly reduced water loss during the normal daytime peak period. Transpiration at night was unaffected by infection.

Both stomatal and cuticular transpiration of single, detached leaves were reduced by infection. A linear correlation was obtained between ‘water saturation deficit’ and transpiration rate in both diseased and healthy plants until the leaves wilted, suggesting that reductions in the stomatal rate are a consequence of the greater water deficits found in diseased plants, the differences in cuticular rates probably being due to anatomical differences between healthy and diseased leaves.

Close parallels between transpiration and water deficit indicate that in diseased plants water loss is largely determined by leaf water content. Thus wilting, commonly seen as a symptom of infection, is not the result of excessive water loss but follows a reduction in the supply of water to the leaves.

The author thanks Professor I. Isaac of this department and Dr G. C. Evans of the Botany School, Cambridge for their advice. The research was sponsored by the Potato Marketing Board.
The effect of temperature on eyespot (Cercosporella herpotrichoides) in wheat seedlings
Authors: SCOTT P. R.
Published: February 2008

When seedlings of the winter wheat cultivars Cappelle‐Desprez, Champlein and Hybrid 46 were artificially infected with mycelial inoculum of Cercosporella herpotrichoides Fron, the number of leaf sheaths penetrated by the pathogen increased with temperature over the range 6‐18oC. Rate of growth of the pathogen on agar also increased with temperature over this range. Temperature had little effect on differences between cultivars in number of leaf sheaths penetrated.
The relationship between the relative growth rates of the shoot system, number of tillers and mean tiller size in Lolium perenne
Authors: TROUGHTON ARTHUR
Published: February 2008

The relative growth rate of the shoot system of Lolium perenne may be considered as being made up of two components, the relative growth rate of the increase in the number of tillers and the relative growth rate of the mean tiller. These three relative growth rates were calculated for twenty‐two clones of Lolium perenne growing in twenty‐eight environments. Analyses of variance showed that differences in the environment were responsible for a greater amount of variation than either differences between clones or the interaction between clonal and environmental influences.

For each clone it was possible to calculate relationships between the relative growth rate of the shoot and its two components as they varied with the environments. The relationships held irrespective of the environmental factor(s) which altered to cause the difference in relative growth rates. In all clones an increase in the relative growth rate of the shoot was found to be due to an increase in the relative growth rates of both components. In seventeen clones the relationship between the increments of the two components was constant. In five of the clones an increase in the relative growth rate of the shoot at low values was due more to an increase in the relative growth rate of the number of tillers than to an increase in the relative growth rate of the mean tiller. At high values the opposite occurred.

These results are discussed in relation to the theory of ‘nutritive diversion’ and in relation to the proportion of lateral buds which produce tillers.
Uptake and distribution of macro‐nutrients in trees of Coffea arabica L. in Kenya as affected by seasonal climatic differences and the presence of fruits
Authors: CANNELL M. G. R. , KIMEU B. S.
Published: February 2008

Young to mature, conventionally managed, single‐stem, deblossomed and fruiting Arabica coffee trees growing in a fertile lateritic clay loam at Ruiru, were uprooted at 2‐ to 3‐monthly intervals between February 1967 and June 1968. Each was divided into ten parts which were dried, weighed, completely ground, and analysed for organic‐N, and total P, K, Ca and Mg.

Mature trees took up about 100 g N, 6 g P, 100 g K, 35 g Ca and 10 g Mg each per annum, of which 8‐29 % (depending on the element) would be removed in an average crop of fruits, and 50‐81 % returned to the soil in prunings and fallen leaves. About half the P and K in senescing leaves was returned to the tree.

N, K, Ca and Mg uptake by deblossomed trees was relatively rapid when they produced a large post‐drought ‘flush’ of shoot growth in February‐April 1967. Thereafter uptake kept pace with changes in dry weight, and the concentration of N, K, Ca and Mg in the tree parts changed relatively little. By contrast, P‐uptake was relatively rapid over the cool, dry season 1967 (June‐September), when the roots < 1 mm diameter grew rapidly, and during the subsequent Short Rains, but was slow during the hot, dry season 1968 (December‐March) when the surface 2‐3 ft of soil dried out. The concentration of P in the trees changed accordingly, especially in the branches. The flower buds took 39 % of the small total P‐uptake during the hot, dry season 1968.

Trees bearing a light or moderate crop of fruits absorbed all the minerals determined more rapidly than deblossomed trees. The fruits on heavily fruiting trees took 89,95,98 and 99 % of the net current increment in Mg, K, organic‐N and P, respectively, but only 39 % of the Ca. All leaves on the fruiting trees became rich in Ca, and most of their woody parts were depleted of P.

Mineral uptake in a coffee plantation is compared with that in plantations of other woody perennial crops, and some practical implications are noted in relation to soil and plant factors affecting the mineral nutrition of coffee in Kenya, with special reference to phosphates.
Aphanocladiutn album, a fungus inducing teliospore production in rusts
Authors: BIALI M. , DINOOR A. , ESHED N. , KENNETH R.
Published: February 2008

The hyphomycetous fungus Aphanocladiutn album can grow over and around uredia of the rusts Puccinia coronata, P. hordei, P. graminis f.sp. avenae and P. recondita f.sp. triticina when host plants are kept under very humid conditions, but not on such plants not infected with rusts; uredia are adversely affected and telia develop in their vicinity.

Plants inoculated with these rusts and with five isolates of A. album (one from a dead insect) showed: (1) much earlier development of telia on detached and non‐detached rusted leaves inoculated with A. album than on corresponding leaves not thus inoculated; (2) telial induction by A. album in some isolates of rust species which hitherto had rarely or never produced telia; (3) precocious telial formation, in comparison with controls, when A. album spores were sprayed on leaves as much as 3 days before and 9 days after rust inoculation, and occasionally after uredia had already matured. As affected leaves remained green until the whole leaf became moribund, senescence is apparently not the factor inducing telia formation.

The normal‐appearing teliospores of some isolates were induced to germinate, whereas others did not. Rhamnus palaestina inoculated with basidiospores of one isolate of A. album‐treated P. coronata f.sp. avenae produced pycnia and fertile aecia.

The importance of A. album as a working tool in rust research and as a possible means for biological control of rust epiphytotics is discussed.
Infection of cereals by cocksfoot mottle and phleum mottle viruses
Authors: BENIGNO D. A. , A'BROOK JOHN
Published: February 2008

Cocksfoot mottle (CFMV) and Phleum mottle (PMV) viruses are both transmitted by the Chrystomelid beetles Ouletna melanopa and O. lichenis. Both viruses are readily inoculated into some cereals but only CFMV has ever been found causing a natural infection, in one wheat crop. The apparent absence of these viruses from cereals in the field results from inefficient transmission by the vectors and the existence of symptomless tolerance in cereals to both viruses, especially after tillering. In cereals symptom expression is related to virus concentration, and both may be influenced by light intensity and ambient temperature. O. melanopa, which is potentially the most important vector of the viruses to cereals, moves to winter‐sown cereals only when the virus‐tolerant growth stage has been reached, and later to spring‐sown cereals when they too have commenced tillering. Whereas the spread of these viruses within grass crops is increased by cutting and grazing, cereal crops are neither cut nor commonly grazed.
Soil fumigation with methyl bromide: bromide accumulation by lettuce plants
Authors: KEMPTON R. J. , MAW G. A.
Published: February 2008

Lettuce plants grown in beds of soil previously fumigated with methyl bromide accumulated water‐extractable bromide, the amount present in the tissues depending on the concentration of inorganic bromide produced in the soil by the breakdown of the fumigant. Samples of lettuce plants from commercial nursery soils fumigated with methyl bromide at rates of 1–2 lb/ 100 ft2 (49–98 g/m2) gave rise to soil bromide levels of n‐6i/μg/g. The corresponding bromide concentrations in the plants ranged from i‐6 to io‐1 mg/g of dry tissue.

The bromide concentrations in whole lettuce plants grown in pots of soil supplemented with 0–5 mg/g inorganic bromide, as potassium bromide, ranged up to 100 mg/g of dry tissue. Bromide taken up from the soil by lettuce plants was located mainly in the outer leaves.

Lettuce was relatively insensitive to the presence of bromide in the soil; no phytotoxic symptoms were observed in plants growing in soils containing 5 mg/g inorganic bromide.

Implications in relation to possible tolerance limits for the bromide content of lettuce plants are discussed.
Water loss from cut grass with special reference to hay‐making
Authors: LESHEM Y. , THAINE R. , HARRIS C. E. , CANAWAY R. J.
Published: February 2008

Water loss from cut grass was studied to determine factors limiting the drying process.

An apparatus, used to measure water loss at 28±1°C from blotting paper and from leaves and stem internodes of cocksfoot, consisted of four channels in which air speed was controlled at 25–80 cm s‐1 and relative humidity at 7–68%.

The maximum rate of water loss from wet blotting paper was 10500 mg water dm‐2 h‐1 but from leaves and stem internodes supplied with water it was less than 250 mg dm‐2 h‐1. The rate of loss from both plant specimens and blotting paper was linearly related to the vapour pressure differences between the specimen and the surrounding air but was not increased when air speed was changed from 40 to 80 cm s‐1. Grass specimens supplied with water had lower rates of water loss than wet blotting paper because of tissue resistances which were calculated for (a) untreated leaf and stem specimens, (b) rubbed leaves, (c) cut leaves, (d) leaves exposed to steam for 60 s. Treatments (b)‐(d) greatly reduced tissue resistances.

The rates of drying of leaves and stem internodes not supplied with water changed only slightly in response to faster air speeds but were significantly increased by treatments (b), (c), (cs) (split stems), (d) and (e) (exposure to petroleum vapour for 60 s). The most effective treatments trebled the drying rates of leaves and increased the drying rates of stem internodes by 10 times. Reductions in relative humidity had little effect on drying rate following treatments (a), (b), (c) and (d), but when treatments (cs) and (e) were given, additional significant increases in drying rates were obtained when the relative humidity was reduced.

Grass specimens given the most effective treatments and dried under the most favourable conditions did not utilize the full drying capacity of the environment, for the rates of water loss from these specimens were at least three times lower than those from wet blotting paper. The results indicate that high rates of drying could be achieved at 28 oC or similar temperatures if practical treatments were developed to remove or greatly reduce the high resistance to water loss in cut grass.
Dilemmas in conservation for applied biologists
Authors: GUNN D. L.
Published: February 2008

Prevention of the use of DDT has been made the target of a powerful propaganda drive in certain prosperous countries because, it is stated, DDT is a danger to man and harms wild life. On the other hand, DDT is by far the most economical, effective and safe insecticide for many uses, particularly for protecting men from certain insect‐borne diseases and for enabling cotton to be grown in poor countries. Some risks can be reduced by eliminating those uses of DDT for which adequately safe, economical and effective substitutes exist, whether chemical or not; other risks can be reduced in other ways. The known risks to men are trivial, except when DDT concentrate is deliberately drunk, and the scare is made up of unknown risks ‐which could equally exist with any object or material, new or old. Risks to wild life have been greatly exaggerated and scares depending on falsehoods have become current. The postulated threat of progressive accumulation of DDT along a long food chain is not adequately supported by evidence, much of which has been misinterpreted.

Thus the main dilemma is how to balance the great and undoubted benefits of DDT to millions of men, women and children against harm to wild life, sometimes genuine and remediable and sometimes dubious.

People who campaign for banning have possibly failed to recognize this dilemma. On the other hand, they may have made a deliberate choice in favour of wild life. In that case, to be logical, they should also oppose all other means of preventing premature death of other people, which they might justify as a means of postponing over‐population. The use or abuse of DDT is a minor component in the rise of the worl's population.
A world‐wide survey of the microflora of Dactylis glomerata seed*
Authors: TULLOCH MARGARET , LEACH C. M.
Published: February 2008

The fungal microflora of orchard (cock's‐foot) grass seed(Dactylis glomerataL.) was determined for 140 samples obtained from thirteen countries. The microflora was assessed by visual examination of dry seed (20–50 x), by microscopic examination of centrifuged seed washings and by incubating seed on 2 % malt extract agar (MA) under a 10‐day regime of diurnal cycling of temperature (23‐9oC/i8‐3oC) and near‐ultraviolet radiation (12 h NUV/ 12 h dark). More than twenty‐five species of potentially pathogenic fungi and forty species of saprophytes were detected. The pathogens included anAscochytasp.,Botrytis cinerea, nine species ofDrechsleraincludingD. dactylitis(infested 23% of seed lots) andD. Useptatum(10% of seed lots), five speciesoiFusariumincludingF. avenaceum(5 % of seed lots),Lep‐tosphaeriasp.,Phleosporasp.,Phomasp.,Phomopsissp.,Pyrenochaetasp.,Rhizoctoniasp.,Rhynchophomasp.,Septoriasp. andStagonosporasp. Many more fungi were identified from seed plated on MA and exposed to NUV than by examination of seed washings or visual examination of dry seed. Several of the fungi that were detected are known to produce mycotoxins.
The transmission of cocksfoot mottle and phleum mottle viruses by Oulema melanopa and O. lichenis.
Authors: A'BROOK JOHN , BENIGNO D. A.
Published: February 2008

Oulema melanopa and O. lichenis both transmit cocksfoot mottle and phleum mottle viruses with similar efficiencies. The viruses were serologically dissimilar and did not cross‐protect against each other in barley. Both viruses were acquired after a few minutes feeding, but longer acquisition feeding periods increased both the efficiency of transmission and persistence in the vectors. Acquisition of either virus increased vector mortality whilst acquisition of both together did not. When both viruses were ingested, only one was transmitted. Each virus could be recovered from haemolymph and faeces, but regurgitation was not observed and could only be induced with the greatest difficulty. The results suggest possible circulative transmission of some beetle‐borne viruses.
The isolation and identification of parsley viruses occurring in Britain*
Authors: FROWD J. A. , TOMLINSON J. A.
Published: February 2008

Severe stunting of parsley plants, with leaf chlorosis and reddening was reported from four localities in Britain in 1968‐70. Affected plants were collected from thirteen sites in Bedfordshire, Buckinghamshire, Cheshire and Bristol, and five viruses (designated PV1‐PV5) were isolated from them. The viruses were distinguished by electron microscopy, host range and type of aphid transmission.

From diagnostic reactions in a range of host species and its transmission by Cavariella aegopodii Scop., the most frequently isolated virus (PV4) and the principal cause of the parsley disease was identified as carrot mottle virus (CMotV).

The other four viruses were infrequently isolated. PV1, PV2 and PV3 were transmitted in the non‐persistent manner by Myzus persicae Sulz. Each was purified and identified serologically as western celery mosaic virus, cucumber mosaic virus and broad bean wilt respectively. PV5 was not fully identified, but was transmitted by C. aegopodii in the presence of CMotV and had particles ca. 500 nm in length. Each of these viruses was re‐transmitted to parsley, but induced slight symptoms or none.
Bacterial canker of poplar
Authors: BURDEKIN D. A.
Published: February 2008

Bacterial canker is a serious disease of poplar and it is important for commercial planting to select those clones of poplar which show resistance to the disease. In inoculation tests, natural bacterial slime and a pure bacterial suspension gave similar extent of invasion. A study of the life‐cycle of the disease indicated the presence of inoculum and of potential infection courts throughout the growing season. It is suggested that the susceptibility of a poplar clone should be determined by assessment of both artificial inoculations and natural infection.
Uptake and distribution of the growth retardant, aminozide, in relation to control of latera shoot elongation in Chrysanthemum morifolium
Authors: DICKS J. W.
Published: February 2008

The uptake, stability and redistribution of the plant growth retardant, aminozide, in ‘pinched’ plants of Chrysanthemum morifolium Ramat. cv. Lemon Princess Anne were examined in relation to control of lateral shoot elongation.

Foliar uptake was most rapid over the first few hours, and was almost complete within 72 h. More of the available aminozide was taken up by the young lateral shoots than by older foliage on the main stem. The aminozide content of entire plants generally remained constant over several weeks, indicating that the compound was relatively stable within the plant.

The time scale and pattern of redistribution of foliar‐ and root‐applied aminozide suggests that the compound may be translocated in both phloem and xylem. Spray application to young lateral shoots was as effective in controlling their elongation as application to all aerial organs. Basipetal transport of aminozide from lateral shoots was slight. The results are discussed in relation to the site of action of the compound and to its application in commercial practice.
Germination of sclerotia of Botrytis tulipae, the cause of tulip fire
Authors: COLEY‐SMITH J. R. , JAVED Z. U. R.
Published: February 2008

Sclerotia of Botrytis tulipae (Lib) Lind. buried in field soil germinated mainly in winter and early spring to produce conidiophores and conidia and then decayed. Except when buried very late in the year sclerotia germinated and decayed in the season following burial.

In the laboratory, sclerotia from pure culture germinated in two ways. On sterile water‐agar they formed colourless mycelium but no conidiophores; the rate of germination was greatest at 25 d̀C. On unsterile filter paper and on soil they produced mainly conidiophores and conidia; the rate of germination was greatest at 5 d̀C and was enhanced by previous cold treatment. It was unaffected by soil‐moisture or pH.

Primary infections of tulips arose from sclerotia placed in the soil but only when they were close to the shoot tip or developing stem. It is suggested that, because of their limited survival, soil‐borne sclerotia are of importance only when tulips are planted in annual succession.
The purification and some properties of cocoa necrosis virus, a serotype of tomato black ring virus
Authors: KENTEN R. H.
Published: February 2008

Cocoa necrosis virus (CNV) was transmitted by sap inoculation to twelve of twenty‐one species tested. It was propagated and assayed in Phaseolus vulgaris. Sap from P. vulgaris was infective after dilution to 10‐3but not 10‐4, after 10 min at 60 d̀C but not 65 d̀C, and after 4 but not 7 days at 20–24 d̀C. Lyophilized sap from P. vulgaris was infective after 2 years in vacuo.

Virus was prepared by extracting infected leaves of P. vulgaris with 0.1 M phosphate (pH 7.5) containing 0.05 M ethylene diamine tetra‐acetate and 0.02 M thioglycollate. After clarification with n‐butanol, virus was purified by precipitation with polyethylene glycol and several cycles of differential centrifugation. Such preparations were very infective and contained numerous particles, 24–26 nm in diameter with a hexagonal profile, which sedimented as two components with sedimentation coefficients (Sd̀20,w) of 101 S and 129 S. The absorption spectra of both components with maximum and minimum absorption at 259 and 240 nm respectively were typical of nucleoproteins (101 S component, A 260/280 = 1.63; A 260/240 = 1.40:129 S component, A260/280 = 1.78; A260/240 = 1.58) and indicated nucleic acid contents of ca. 35% for the 129 S component and ca. 20% for the 101 S component; values calculated from the sedimentation coefficients were 41 and 30% respectively. Only the 129 S component seemed to be infective and was not more so when mixed with 101 S component. Both components contained a single protein subunit weighing ca. 60000 daltons.

Under certain conditions sap fractionated without butanol gave virus preparations containing empty protein shells (54 S) and small spherical particles (20–30 S) ca. 12 nm diameter.

CNV is a serotype of tomato blackring virus and is distantly related to Hungarian chrome mosaic virus.

The cryptogram of CNV is */*:*/(35–41):S/S:S/*.
Black leaf streak of bananas in Fiji
Authors: FIRMAN I. D.
Published: February 2008

Black leaf streak of bananas, caused by Mycosphaerella sp., prevented fruit of export quality forming and bunches maturing. Some infected leaves lived less than 50 days and were seldom retained until harvest. Maneb or benomyl applied in oil/water emulsions gave good control and benomyl was so effective that plants had ten leaves at harvest and some leaves survived for 245 days. Plants sprayed with maneb or benomyl flowered I month early. No benomyl residues were detected in the fruit exported to New Zealand.

The control of black leaf streak by sprays containing oil has caused other leaf diseases to become more prevalent and the ensuing complex disease situation is discussed.
Purification and properties of elderberry latent virus, one of four sap‐transmissible viruses obtained from American elder (Sambucus canadensis L.)
Authors: JONES A. T.
Published: February 2008

Cherry leaf roll, tomato black ring and two previously unrecorded viruses were transmitted to Chenopodium quinoa from Sambucus canadensis plants imported from the U.S.A. Of the two newly recognized viruses one, code‐named elderberry virus A, has filamentous particles about 650 times 15 nm; the other, named elderberry latent virus (ELV), was transmitted to several herbaceous species but remained symptomless in elder and most other hosts. In C. quinoa sap ELV lost infectivity after dilution to 10‐‐5 to 10‐‐6, 10 min at 85–90°C, and 7 days at 18°C. Infectivity of nucleic acid extracts was abolished by ribonuclease in 0.2 m sodium chloride. ELV was purified from C. quinoa leaf extracts that were clarified with chloroform, by precipitation at pH 5 and differential centrifugation. Purified preparations contained numerous isometric particles c. 30 nm in diameter and a few particles c. 17 nm in diameter. In 0.06 M phosphate buffer ELV sedimented as a major 112 S (calculated for infinite dilution) component and a 48 S minor component. ELV showed no serological relationship to twenty‐seven other isometric plant viruses. Its present cryptogram is R/I: *I*:S/S:S/*.
The carbohydrate and water balance of beans (Vicia faba) attacked by broomrape (Orobanche crenata)
Authors: WHITNEY P. J.
Published: February 2008

Orobanche crenata parasitizing beans maintained a slightly higher osmotic pressure than the bean roots, largely because of the higher concentration of sugars in the broomrape tissues. The sugar was withdrawn from the bean mainly as sucrose, which was hydrolysed to glucose and fructose by the Orobanche. These sugars were then rapidly translocated to the developing flower spike. As well as maintaining a high osmotic pressure this hydrolysis ensured a sucrose concentration gradient between host and parasite.

In the field, bean plants showed wilt symptoms at about the time that the Orobanche flower spikes emerged. It was found that the higher the level of infection the lower was the water content of the host. This fall in water content was not due to increased water loss by the bean shoots and it seemed unlikely that it was due to water removal by the parasite.

It was concluded that the death of the bean was due to desiccation brought about largely by the reduced ability of the carbohydrate‐starved roots to extract water from the soil.
Effect of awns and drought on the supply of photosynthate and its distribution within wheat ears
Authors: EVANS L. T. , BINGHAM J. , JACKSON P. , SUTHERLAND JENNIFER
Published: February 2008

The presence of awns doubled the net photosynthetic rate of wheat ears and also increased the proportion of 14CO2 assimilated by the ear that moved to the grain. The effect of water supply on photosynthesis and movement of assimilates was greater for leaves than ears, so that drought increased the proportion of assimilate contributed by ear photosynthesis to grain filling from 13% to 24% in the awnless ears, and from 34% to 43% in the awned ears.

14C assimilated by the ears was most important to the economy of the upper spikelets and to the distal florets in each spikelet, whereas flag leaf assimilate went mainly to the spikelets in the lower half of the ear, and to the proximal florets.

Awns increased grain yield in the dry but not in the irrigated treatment, despite the large contribution of awned ears to grain filling. Either the supply of assimilate did not limit grain yield when water supply was not limiting, or there were compensating disadvantages to awns. However, they did not seem to have any adverse effect on the development of the upper florets, nor did they reduce grain number per ear.
Influence of temperature on hatching of winter eggs of fruit‐tree red spider mite, Panonychus ulmi (Koch)
Authors: CRANHAM J. E.
Published: February 2008

The effects of the duration and degree of chilling, and the temperature of incubation, on hatching of winter eggs of Panonychus ulmi (Koch) were investigated. For chilling, 0°C and 5°C were more effective than — 5° and 9°, and the limits for the reaction were close to — 10° and 15°. As the chilling period was increased from 60 to 200 days, the percentage hatch on incubation at 21° increased, and the mean incubation time and its variance decreased. Before the maximum effect of chilling was achieved, percentage hatch on incubation at 9° and 15° was higher than at 21°; 27° was lethal to most winter eggs though not to summer eggs. After chilling, the later stages of diapause development could occur at temperatures from 0° to 21°) i.e. above and below the threshold temperature for morphogenesis, 6–7° in both winter and summer eggs. Diapause development cannot, therefore, be a unitary process. The significance of the results is discussed in relation to forecasting the time of hatch in the field, and to the phenological aspects of hatching in the spring.
Observations on the effects of mildew, Erysiphe graminis, on growth of spring and winter barley
Authors: BROOKS D. H.
Published: February 2008

In field plots, early and severe attacks of powdery mildew on spring barley plants greatly reduced the vigour, decreased the amount of root, the number of ear‐bearing tillers and the grain size. In less severe, or later attacks, mildew mainly affected the grain size.

On winter barley, where mildew attacked both in autumn and in spring, yield was decreased more than when only a spring attack occurred. The early attack retarded development of the root system, increased winter kill and decreased the number of ears reaching maturity.

Because early mildew attack affects yield, it is not always possible to correlate yield loss with intensity of mildew at any one growth stage of the crop.
Verticillium wilt of cacao in Uganda: the relationship between Verticillium dahliae and cacao roots
Authors: EMECHEBE A. M. , LEAKEY C. L. A. , BANAGE W. B.
Published: February 2008

Isolates of Verticillium dahliae Kleb. from wilted cacao (Theobroma cacao L.), cotton (Gossypium hirsutum L.), and okra (Abelmoschus esculentus Medik.) penetrated all regions of living cacao tap and lateral roots and progressed intracellularly from the epidermis to the xylem in 4–6 days. The hypocotyl and tissues of the unerupted lateral roots beneath the epidermis resisted invasion.

Host reactions included browning of extensively colonized cells, alteration (with apparent granulation) of the cytoplasm, and accumulation of materials in the lumina of endodermal cells. Resistance in the hypocotyl was associated with occasional thickening of inner tangential walls of colonized epidermal cells.

The fungus formed conidia, microsclerotia, and narrow and wide hyphae within root tissues. The narrow hyphae predominated at the front of mycelial invasion of tissues while the broad hyphae developed behind this front.

Limited studies under non‐sterile conditions indicated that the apparent host‐parasite interactions were similar to those observed with sterile roots and cultures of V. dahliae.
Factors' governing ingestion by the earthworm Lumbricus terrestris (L.), with special reference to apple leaves
Authors: WRIGHT M. A.
Published: February 2008

Captive worms fed little on fresh apple leaves, but did so readily after the leaves had been leached in water. This was due to their being soft and easy to fragment and not to loss of unpalatable substances during the leaching process. A simple apparatus to measure leaf texture is described. Worm feeding rates were similar for leaves of similar texture but of different phenolic content. Filter paper was accepted as food. The addition of leaf leachates to filter paper disks increased feeding rates, so did added bacterial cells. The part played by leaf micro‐organisms in the nutrition of worms and their effect on leaf texture is discussed. Unsoftened leaf material was readily eaten provided it was small enough to be swallowed whole. Leaves from various aromatic plants were eaten by starved worms, but rejected by well‐fed ones. Starved worms given aromatic leaf material together with apple leaf preferred the latter. Various unusual materials were eaten, but polyester foam was accepted only when coated with bacterial cells. Responses to chemical as well as to tactile stimuli seem to be involved.
The infection and perennation of the bitter rot fungus, Gloeosporium album, on apple leaves
Authors: TAN A. M. , BURCHILL R. T.
Published: February 2008

In the period from late spring to leaf‐fall (May‐November) Gloeosporium album Osterw. was regularly isolated from leaves of the apple variety Cox's Orange Pippin affected by the disorder called ‘Cox‐spot’. The fungus grew epiphytically on healthy apple leaves, producing a network of mycelium which developed sporulating pustules when in contact with damaged or moribund tissues.

Both the imperfect and perfect stages of the fungus were found on overwintered leaves; isolates from ascospores and conidia proved pathogenic on wood and fruit.
Effect of Ophiobolus graminis infection on the growth of wheat and barley
Authors: ASHER M. J. C.
Published: February 2008

Glasshouse experiments are reported, in which the development of young wheat and barley plants was examined following inoculation with Ophiobolus graminis (Sacc.) Sacc. The dry weight, leaf area, tiller number and water content of the shoot were reduced by infection. Reductions were equally severe in wheat and barley. The seminal root system of both was severely attacked and its growth retarded. Inoculated plants, however, translocated a greater proportion of their total assimilates to the root system and produced more adventitious roots than healthy plants. As a result there was an increase in both the number and proportion of healthy roots on these plants following the initial infection of their root systems. This effect was more pronounced in barley than in wheat. It is suggested that this may in part account for the reported relative tolerance of barley to take‐all attack under field conditions.
Water‐borne spore dispersal in coffee berry disease and its relation to control*
Authors: WALLER J.M.
Published: February 2008

Devices are described which were used to catch rain‐dispersed Colletotrichum conidia within and between coffee trees infected with coffee berry disease (CBD). The amount of CBD inoculum dispersed was related to the number of diseased and sporulating berries but not to the sporulating capacity of the fungus in maturing bark. Wet conditions encouraged spore production and dispersal, and spraying with fungicides prolonged sporulation of diseased berries.

The amount of pathogenic inoculum, subsequent disease development and crop losses were greatly increased by the presence of only a few diseased berries during growth of the young crop. Spore concentrations were greatest close to diseased berries, but most spores within trees were dispersed downwards through the canopy. Some spores were dispersed between trees by wind‐driven rain‐splash and vectors such as pickers.

Inoculum sources in tree tops are most important during CBD epidemics and disease can be restricted by removing or spraying the tops of multiple‐stem trees. Fungicide applied to tree tops effectively controls CBD, because spores dispersed during rain are accompanied by redistributed fungicide
Ecological studies on potato mop‐top virus in Scotland
Authors: Jones R. A. C. , HARRISON B. D.
Published: February 2008

Plants with symptoms of potato mop‐top virus (PMTV) occurred in many commercial seed stocks of Arran Pilot and Red Craig's Royal potato in Scotland, but their incidence rarely exceeded 5%. In nuclear stocks of seed potatoes, most varieties examined in 1967 and 1968 were infected at one or more locality, but infected plants did not occur in all clones or at all stages of propagation of any one variety. infection of nuclear stocks resulted both from propagation on virus‐infested land and from unwitting selection of infected plants to start new clones. PMTV was detected in farm soils ranging from light sands to heavy loams, in five Scottish counties. Soil was infested throughout the ploughed layer but the severity of infestation varied greatly within any one field; some sites of former potato clamps were heavily infested. PMTV was detected in field soil 12 years after potatoes were grown.

In glasshouse tests many British crop and wild plants were colonized by Spongospora subterranea. Within some families all species tested were moderate to good hosts. (Solanaceae, Chenopodiaceae and Cruciferae), in others, species differed greatly in susceptibility (Compositae and Umbelliferae), and in a few, species were poor hosts or were not infected (Caryophyllaceae and Gramineae). Of the British crop and weed species that were moderate to good zoosporangial hosts of S. subterranea, only Solanum nigrum, potato, spinach and sugar beet were hosts of vector‐borne PMTV. Potato probably survives between potato crops mainly in the resting spores of S. subterranea. PMTV was probably first brought to Europe with potatoes from South or Central America.