bluuebunny/crossref_metadata_2025 huggingface dataset:
Transmission of strains of raspberry ringspot and tomato black ring viruses by Longidorus elongatus (de Man)
Authors: TAYLOR C. E. , MURANT A. F.
Published: February 2008

Scottish isolates of raspberry ringspot (RRV) and tomato black ring viruses (TBRV) showing slight serological differences were associated in the field with the nematode Longidorus elongatus and were all transmitted equally efficiently by this species in laboratory experiments. Forms of both viruses from southern England and Germany that are distantly serologically related to the Scottish isolates were also transmitted experimentally by L. elongatus, although in the field they are associated with other Longidorus species. L. elongatus transmitted English isolates of RRV almost as efficiently as the Scottish isolates but it transmitted English and German isolates of TBRV only occasionally. Four isolates each of TBRV and RRV were detected by inoculating plants with extracts of nematodes; the results paralleled those of the vector studies.
Inhibition of tobacco mosaic virus infectivity by the fungus Thielaviopsis basicola (Berk. &Br.) Ferr
Authors: HARPAZ I. , BAR‐JOSEPH M. , SELA I.
Published: February 2008

The presence of an inhibitor of tobacco mosaic virus (TMV) infection was demonstrated in extracts of Nicotiana glutinosa infected with the fungus Thielaviopis basicola. The inhibitor was shown to spread systemically in the infected plant. It was found to be heat‐stable, but rapidly lost its activity upon dilution or dialysis. The inhibitor does not act directly on the virus and lacks the power to decrease infectivity of virus already present in the cells.

A similar inhibitor was extracted from the fungal body, differing only slightly from the one extracted from fungus‐infected plant tissue.
The effect of temperature on loose smut of wheat (Ustilago nuda)
Authors: DEAN W. M.
Published: February 2008

In experiments made in controlled‐temperature rooms on the wheat variety Kota, inoculated with two races of Ustilago nuda (Jens.) Rostr., maximum smut development occurred at 23 °C; at 20 ° and 15 °C the incidence and extent of smutting was reduced. An even greater reduction occurred when seedlings were grown at 6 °C for 2 months. No marked effect of temperature on mycelial development within the spike was observed until the ear emerged, when the mycelium in many of the ears of plants subjected to the lower temperatures failed to sporulate. The date of sowing in the field influenced disease development, presumably through the period of exposure to winter temperatures. Variety Little Club inoculated with race C3 showed a similar but less marked response to cold‐treatment.
The persistence in soil of the fungicidal seed dressings captan and thiram
Authors: GRIFFITH R. L. , MATTHEWS S.
Published: February 2008

The persistence in soil of captan and thiram was investigated by means of a technique in which the fungicidal content of soil was assayed by incubating plugs of soil containing fungicide on agar plates seeded with spores of Myrothecium verrucaria and measuring the diameter of the zone of fungal inhibition that was produced. When the fungicides were well distributed in soil they showed extremely low persistence, both fungicides having a half‐life of between 1 and 2 days. In contrast, when the fungicides were added to soil in the form of dressings on the surface of glass beads they persisted well in soil, little change from their initial concentration occurring even after 21 days.

These results suggest that captan and thiram persist far longer in soil when localized in high concentrations than when uniformly distributed through soil. If a glass bead is regarded as a reasonable simulation of a seed these results help to explain the effectiveness of these fungicides as seed dressings despite their apparently low persistence in soil.
Fungicidal activity and chemical constitution
Authors: BYRDE R. J. W. , FIELDGATE DIANA M. , JORDAN V. W. L. , WOODCOCK D. , CARTWRIGHT J.
Published: February 2008

Six 4‐(1‐phenylalkyl)‐, eight 4‐(1‐cyclohexylalkyl)‐, seven 4‐(1‐cyclo‐pentylalkyl)‐ and seven 4‐(1‐cyclobutylalkyl)‐2,6‐dinitrophenols, together with some derivatives, were tested against the powdery mildews of apple (caused by Podosphaera leucotricha) and blackcurrant (caused by Sphaerotheca mors‐uvae) in the greenhouse and in field trials, against rose mildew (caused by S. pannosa) in the field, and against Venturia inaequalis in spore germination tests. Highest activity in the greenhouse was shown by members of the cyclobutyl series with 4–6 carbon atoms in the alkyl group. No phytotoxicity on healthy foliage occurred with any compound in these series.
The nature of the microbial stimulus affecting sporophore formation in Agaricus bisporus (Lange) Sing
Authors: HAYES W. A. , RANDLE PHYLLIS E. , LAST F. T.
Published: February 2008

An apparatus is described in which pure cultures of Agaricus bisporus were maintained on composted media in filtered atmospheres free from (a) noxious concentrations of carbon dioxide, and (b) contaminating microorganisms. When grown on compost alone, cultures of A. bisporus did not produce sporophores. Their formation was however stimulated by a covering layer of an unsterilized mixture of peat and chalk (=‘casing’ soil). Autoclaving or fumigating ‘casing’ with propylene oxide decreased populations of contaminating bacteria and prevented sporophore formation.

Populations of micro‐organisms isolated from unsterile ‘casing’ contained bacteria which when added to pure cultures of A. bisporus stimulated fruit‐body formation. Numbers of these stimulators increased when cultured on a carbon‐free liquid medium exposed to atmospheres with ethanol, ethyl acetate and acetone or containing the volatile metabolites of A. bisporus. The ability to utilize these volatile chemicals was exploited in a selective technique for isolating sporophore stimulators where aqueous suspensions of mixed bacterial populations were exposed to atmospheres of these materials for 5 days, before aliquots were added to agar media subsequently gelled.

The stimulatory bacteria were identified as, or closely related to, Pseudomonas putida.
Properties of some defective strains of tobacco mosaic virus and their behaviour as affected by inhibitors during storage in sap
Authors: KASSANIS B. , Woods R. D.
Published: February 2008

From the type strain of tobacco mosaic virus, defective strains were isolated that produced chlorotic or ringspot type symptoms in tobacco and were difficult to transmit without carborundum in the inoculum. Their concentration was less than 0–1 μg/ml of sap instead of the usual 2 mg/ml with the type strain. Phenol extracts of infected leaves were a little more infective than extracts in buffer, whereas phenol extracts of leaves infected with type strain were very much less infective than extracts in buffer. Electron microscopy of infective sap rarely showed any virus particles, but preparations concentrated by ultracentrifugation contained virus particles, many of which were broken or seemed inadequately assembled.

Changing the ambient temperature at which infected plants were kept from 20 to 35°C did not increase the amount or improve the appearance of the virus. Some of the strains were inactivated during heating for 10 min between 70 and 80 °C.

Undiluted sap lost its infectivity in 3 days at 20 °C, as did the type strain when diluted to 0–1 μg/ml in sap from healthy leaves. This is because substances that inhibit infection were produced by microbes in the sap. The ability of sap from healthy leaves to inhibit infection increased by more than twenty‐five times when left 3 days at 20 °C. Infectivity of appropriate mixtures of type strain and aged sap was restored by diluting them in buffer. Sodium azide at 0·02% in sap prevented formation of the inhibitor. The infectivity of the defective strains increased when inoculated together with the type strain.
Chemical control of root disease of Douglas–fir seedlings in relation to fungus and nematode populations
Authors: BLOOMBERG W. J. , ORCHARD W. R.
Published: February 2008

Seed treatment with thiram reduced post–emergence damping–off, while fumigating forest nursery soils with methyl bromide or DD improved Douglas‐fir seedling emergence, shoot and root growth, and decreased the incidence of root disease.

At an old site, where corky root develops, the benefits from these fumigants were associated with fewer (a) Xiphinema bakeri and (b) isolates of Cylindrocarpon radicicola.

At a new site, decrease in Fusarium root rot and increase in shoot growth were related to reduction of populations of Paratylenchus and Pratylenchus, respectively. In unfumigated soils, Fusarium oxysporum was isolated from diseased and healthy roots.
The phenology of skin spot (Oospora pustulans Owen &Wakef.) and other fungal diseases of potato tubers
Authors: HIDE G. A. , HIRST J. M. , MUNDY E. J.
Published: February 2008

Underground stems and roots of the potato varieties King Edward and Majestic became more severely infected by Oospora pustulans (skin spot) as the growing season advanced. Tubers became infected at their initiation in June and July but the proportion of infected eyes usually increased during both the growth of the crop and bulk storage. Some buds on tubers in bulk stores died in December, but few were killed until after January, when attacks increased until by March about a quarter of Majestic eyes were usually dead. Boxing (chitting) not only prevented most eyes from dying but also prevented much skin spotting on tubers. At High Mowthorpe, Majestic seed unboxed or boxed in March yielded, respectively, 3 and 1 ton/acre less than seed boxed by January. Early boxing increased the yield of seed–sized tubers but did not affect the infection of progeny tubers. Dipping Majestic seed tubers in organo–mercurial fungicide and then boxing soon after lifting decreased their infection by O. pustulans; it also lessened infection on plants they produced and increased the yield of progeny seed–sized tubers. However, dipping, even in successive years, had little effect on the infection of progeny tubers by O. pustulans.

Rhizoctonia solani and Helminihosporum atrovirens became increasingly prevalent on tubers during growth after July and during bulk storage. H. atrovirens was decreased by early boxing or dipping tubers in fungicide. Verticillate conidiophores often grew on incubated tuber plugs but their prevalence was affected by past storage.

The results suggest that some of the benefit for chitting may be from disease control, it was not possible to measure the extent to which benefits from chitting depend on effects on disease or on the physiology of the tuber.
Infection of the flowers and seed of parsnip by Itersonilia pastinacae
Authors: CHANNON A. G.
Published: February 2008

Seeding parsnip plants on four commercial holdings in Essex showed not only the root cankers and leaf spots associated with infection by Itersonilia pastinacae, but also extensive lesions on the petioles and necrosis of the inflorescences. These last‐named symptoms were proved to be caused by I. pastinacae which could also be found on some of the seeds. Seed infection, though largely superficial, was sometimes more deep‐seated. It could be eliminated by soaking the seed in an aqueous suspension of 0·2% thiram at 30 °C for 24 h.

Heavily infected seed gave a low percentage of seedlings bearing cotyledon lesions: it is uncertain whether hypocotyl lesions, which also occurred, were caused directly by the fungus.

An outdoor test failed to show that infected seed gave rise ultimately to roots bearing Itersonilia cankers: the significance of this and other possible sources of infection is discussed.
The production by species of Allium of alkyl sulphides and their effect on germination of sclerotia of Sclerotium cepivorum Berk
Authors: COLEY‐SMITH J. R. , KING J. E.
Published: February 2008

A number of n‐propyl and allyl sulphides were shown to stimulate germination of sclerotia of Sclerotium cepivorum in soil. Several of these sulphides were evolved by chopped garlic cloves and onion bulbs, and by their extracts, as well as by distillates and condensates prepared from extracts. Sulphides produced by garlic were methyl and allyl compounds, whereas those of onion were methyl and n‐propyl derivatives. Few or no volatile sulphides were detected by gas chromatography of head spaces of intact Allium plants although it is considered that small quantities of sulphides may be produced from these plants in soil. The stimulatory activity of distillates and condensates appears to be entirely due to their alkyl sulphide content and that of extracts at least partially so.
Phytoalexin production by leaves of Pisum sativum in relation to senescence
Authors: BAILEY J. A.
Published: February 2008

A sterile culture nitrate of Penicillium expansum was shown to induce pisatin synthesis in pea leaf discs. The amount of pisatin produced by pea leaves was shown to decrease as they underwent senescence. N6‐benzyladenine delayed senescence, and at the same time maintained the production of pisatin at a high level. In darkness, leaf discs maintained on either benzyl‐adenine solution or distilled water produced greater amounts of pisatin than leaf discs which were not treated in this way. Benzyladenine also increased pisatin production by leaf discs kept in the light. The relevance of these results to disease resistance and possible mechanisms involved are discussed.
The stimulating effect of some fungicides on Glomerella cingulata in relation to the control of coffee berry disease
Authors: NUTMAN F. J. , ROBERTS F. M.
Published: February 2008

The non‐parasitic strain of Colletotrichum coffeanum Noack which colonizes the maturing wood of Coffea arabica produces its perfect stage (Glomerella cingulata) on the branches. Assessments of the relative abundance of this in relation to preceding rainfall have shown that for unsprayed branches, but rarely for sprayed ones, the correlation is negative and highly significant. Various fungicides stimulate G. cingulata greatly, and this stimulation persists for many months. One other saprophytic component of the micro–flora is similarly stimulated, but with two others all the fungicides used depress sporulation. It is suggested that when the main source of infection of coffee berries is the pathogenic conidia from the wood, the mechanism of long–term control by early–season sprays may lie partly in this stimulation of some fungal competitors of the pathogen.
Seasonal differences in the pattern of assimilate movement in branches of Coffea arabica L
Authors: CANNELL M. G. R. , HUXLEY P. A.
Published: February 2008

At Ruiru, Kenya, 14CO2 was fed to single leaves at different distances from the apex on branches of mature fruiting and non‐fruiting trees of Coffea arabica on six occasions from the Short Rains (November) 1966 to the Long Rains (April‐May) 1967. The location of 14C‐labelled assimilates in the treated branches was determined 26 h later by autoradiography. The direction of movement of labelled assimilates indicated large seasonal differences in the relative sink strengths of the shoot tip, fruit and trunk‐root systems.

On vegetative trees the sink strength of trunk‐roots was much smaller, as compared with the shoots, at the beginning of the Long Rains than at the end of the previous Short Rains or in the intervening dry season. Assimilate use by growing fruits did not alter the pattern of distribution of assimilates to the other sinks at the end of the Short Rains, but it did restrict assimilate movement to both shoot tips and trunk‐roots at the_ beginning of the Long Rains. In the dry season, virtually all assimilates were utilized by growing fruits when these were present. Vegetative secondary shoots provided assimilates to growing fruits and trunk‐roots at the end of the Short Rains and in the dry season. Some practical implications are noted.
Estimation of yield in wheat from measurements of photosynthesis and translocation in the field
Authors: LUPTON F. G. H.
Published: February 2008

The rate of photosynthesis of ears, flag leaves and second leaves of two varieties of wheat, and the proportion of synthesized carbohydrate translocated from them to the grain, were determined in the field using 14CO2. The relationship of rate of photosynthesis to changes in age and in incident radiation was expressed by parameters determining hyperbolic functions. These were combined with empirical equations describing the increase with age in the proportion of photosynthate stored in the grain, to form a mathematical model by which yield was determined from physiological parameters. This model gave estimates of yield in reasonable agreement with measured values.
Experiments with CCC on wheat: effects of spacing, nitrogen and irrigation
Authors: HUMPHRIES E. C. , BOND W.
Published: February 2008

In experiments with spring and winter wheat at Rothamsted and Woburn during 4 years CCC increased yield at close spacing (4 in) (10 cm) more than at usual spacing (8 in) (20 cm), but there was no interaction between spacing and yield.

Some experiments tested up to 2·4 cwt/acre (300 kg/ha) N to see whether yields continued to increase with more than usual amounts of N, when CCC prevented lodging. There was no evidence of this.

When a short dry spell occurred at ear emergence, yield of spring wheat was increased by 6 cwt/acre (750 kg/ha) by CCC and 10 cwt (1250 kg) by irrigation. CCC probably improves yield in these conditions because the larger root system it causes enables more ear‐bearing shoots to survive.

CCC increases yield in two ways, either by increasing ears or grain per ear. In an unlodged crop CCC usually makes the grains smaller, but by preventing lodging it can also increase size. Usually CCC decreases the leaf area per shoot. The flag leaf may be smaller, unchanged or larger than those of untreated plants. There was no obvious connexion between flag‐leaf area and grain yield; when CCC decreased flag‐leaf area duration by 25 %, grain yield was unchanged.

The results suggest that using CCC gives a more than even chance of a profitable yield increase.
A laboratory method for studying the biology and control of pests in mushroom compost
Authors: WYATT I. J.
Published: February 2008

A Petri dish technique, devised by Eger (1960, 1962) for studying mycelial growth through mushroom compost and casing material, has been modified for pest investigations. The method provides a sensitive test for phytotoxic and insecticidal action of applied chemicals, and experiments are described which indicate that thionazin is a suitable insecticide for use against Heteropeza pygmaea Winnertz (Dipt.: Cecidomyiidae). Examples are also given of the use of this method in the study of the biology and population dynamics of paedogenetic Cecidomyiidae.
Factors involved in resistance to blight (Phytophthora infestans (Mont.) de Bary) in potatoes and assessment of resistance using detached leaves
Authors: MALCOLMSON JEAN F.
Published: February 2008

In leaves of potatoes inoculated with Phytophthora infestans early in the growing season, more but smaller lesions with later onset of sporulation and fewer sporangia developed than on those inoculated later. None of these factors was uniform on detached leaves of all clones, so could not be used separately to forecast field resistance satisfactorily; when considered together, a reasonable prediction was feasible. With some clones, tests of detached leaflets gave a better indication of behaviour in the field than laboratory tests of whole plants.
Host/parasite relations up to the time of tuber initiation in potato plants infected with Verticillium spp
Authors: HARRISON J. A. C. , ISAAC I.
Published: February 2008

The growth pattern of potato plants, infected with V. albo‐atrum and V. dahliae, was studied, using growth‐analysis techniques, during the initial stages of development up to tuber initiation.

During the first 5–6 weeks of growth the morphology of the infected plants was not affected, but the distribution of dry weight materials between various plant organs and the growth rates of the whole plants were affected much sooner. In contrast to healthy plants, those infected exhibited lower specific leaf areas, higher leaf weight ratios and higher leaf area ratios, and, under dry conditions, lower relative growth rates and lower unit leaf rates. Thus during the incubation phase of the disease, although effects of infection are not immediately apparent, Verticillium pathogens have a considerable influence upon the development of the host.
Dew and the growth of the uredospore germ tube of Puccinia graminis on the wheat leaf
Authors: BURRAGE S. W.
Published: February 2008

Water droplets simulating dew, formed on wheat leaves held in a condensation chamber, appeared first on the leaf hairs and coalesced into lines along the ridges of the leaf surface in close proximity to the stomata. On leaves thus wetted, germ tubes from uredospores of Puccinia graminis showed a thigmotropic response, growing at right angles to the ridges: when they reached the stomatal region the penetration of the stoma may be further assisted by chemotropic or hydrotropic attraction.

Studies on plastic surfaces showed that germ‐tube growth took place only between and not within water droplets.
Inoculum sources for coffee berry disease*
Authors: GIBBS J. N.
Published: February 2008

Isolates of Colletotrichum spp. from coffee berries and bark in Kenya fell into four categories, distinguishable by their cultural characteristics on agar. Three of these proved non‐pathogenic; the fourth invariably infected both wounded and unwounded berries and caused coffee berry disease.

The sporulating capacity on bark of the various Colletotrichum strains showed peaks in the periods before both the long and the short rains. The pathogenic strain made up only a very small proportion of the whole Colletotrichum complex on the bark and its sporulating capacity never exceeded twenty spores/cm2/h. By contrast, a green berry with an active coffee berry disease lesion produced 5×104conidia/h and an infected ripe berry twice as many.

It is concluded that in any year, regardless of cropping pattern, diseased berries are likely to play an important role in the development of coffee berry disease.
Early‐season sprays for the control of coffee berry disease*
Authors: GRIFFITHS E. , GIBBS J. N.
Published: February 2008

Bock (1963) showed that in the years 1956‐60 early season sprays achieved good control of coffee berry disease (CBD) in East Rift areas of Kenya. In recent years, however, this spray programme has given erratic and often very poor results. In field experiments in 1966 yields of main (late) crop were increased from 151 to 652 kg/ha by early season sprays but in 1967 practically no control of the disease was achieved. Of the fungicides examined captafol was superior to copper; ‘Tuzet’, the best antisporulant, gave the poorest control. Analysis of the data indicates that this large seasonal variation depends on the very different inter‐relationships between rainfall, cropping pattern and timing of sprays which obtained in the 2 years.

The hypothesis that early‐season sprays achieve control of CBD mainly by reducing the sporulating capacity of the maturing bark is questioned. The view is put forward that the protectant action of these sprays has been underestimated.
Control of survival of Ophiobolus graminis between consecutive crops of winter wheat
Authors: SCOTT P. R.
Published: February 2008

Under a glasshouse crop of red clover, Ophiobolus graminis (Sacc.) Sacc. in artificially colonized straws survived for longer on the soil surface than when buried, and for much longer when suspended above the soil; survival in buried straws was somewhat more prolonged in fallow soil than under clover. In field experiments with consecutive crops of winter wheat, under‐sowing with red clover was not effective in reducing the incidence of take‐all, possibly because of above‐ground survival of the pathogen in unploughed straw. Early rotavation, however, significantly reduced disease incidence, probably because of enhanced microbial activity and competition for nitrogen in the well‐aerated compost of soil and stubble.
Investigations on chemical control of zebra disease in Agave hybrid no. 11648
Authors: PEREGRINE W. T. H.
Published: February 2008

In laboratory, greenhouse and field experiments, mancozeb and copper compounds controlled the leaf‐spot phase of zebra disease caused by Phytophthora arecae, one of the pathogens responsible for this serious disease in Tanzania's high‐yielding Agave hybrid no. 11648. As the copper compounds were phytotoxic, Dithane M‐45 (Mancozeb) is recommended as a protectant during the rainy season.
Effect of CCC and glycine betaine on growth and growth‐substance content of primary leaves of dwarf Frenchbean (Phaseolus vulgaris L.)
Authors: WHEELER A. W.
Published: February 2008

CCC (2‐chloroethyltrimethylammonium chloride) decreased growth of primary leaves and stem internodes above the hypocotyl of dwarf French bean, probably because it decreased the amount of auxin produced by interaction between tryptophan and phenolic esters in the primary leaves. Growth of leaves was less affected than that of stems, and the gibberellin content of the primary leaves, previously shown to be associated with their expansion, was unaffected by CCC. CCC delayed death of the primary leaves, the breakdown of chlorophyll, and the increase in auxin associated with death of bean leaves. CCC had less effect on the growth of leaf discs, probably because they are not sites of growth‐substance production. Glycine betaine, a quaternary ammonium compound similar to CCC, did not affect growth of bean plants, their metabolism of growth substances or the longevity of their primary leaves, but inhibited growth of leaf discs, probably directly.
Effect of plant population on the production and distribution of dry matter in maize
Authors: ALLISON J. C. S.
Published: February 2008

Grain and total dry weight of maize (Zea mays L.) at final harvest increased by about 50% and 30%, respectively, when the population was increased from 23000 to 48000 plants/ha, but did not increase further with population up to 74000/ha.

Between 6 and 10 weeks after sowing, crop growth rate (C) increased by about 40% with increase in leaf‐area index (L) from 2 to 5·5, despite a concomitant increase in moisture stress. Immediately after flowering, which occurred at 10–11 weeks, C increased up to the greatest L attained, 6·7, and would probably have reached a maximum, with L about 7, when nearly all the incident light would be intercepted by foliage. Later, the L at which C was maximal decreased, probably because the photosyhthetic efficiency of leaves decreased faster with time as L increased; 18 weeks after sowing, when L varied between 3 and 5·5, C was maximal when L was 5.

The proportion of grain in the dry matter accumulated after flowering increased from 73% when population was 23000/ha to 82% when it was 60000–74000/ha. Stem weight increased until 3–4 weeks after flowering, then remained constant when population was 23000/ha, but decreased in denser populations. The fraction of the ear consisting of grain increased with population.
The effects of superficial wax on leaf wettability
Authors: HOLLOWAY P. J.
Published: February 2008

Experiments are described which provide more information on the role played by superficial waxes in the natural water‐repellency of leaf surfaces. Contact angles of water were measured on a variety of leaf surfaces, before and after removal of wax, and on smooth films of the isolated superficial waxes. The differences in wettability of leaf surfaces are not wholly accounted for by differences which occur in the chemical and hydrophobic properties of their superficial waxes.

Waxes isolated from leaves exhibiting contact angles less than 90° are usually more hydrophobic than the leaf surface itself. On most leaves exhibiting angles greater than 90° wax is the dominant factor governing water‐repellency, the isolated wax normally making at least a 60 % contribution to the contact angle measured on the leaf surface. Additional factors, such as roughness, responsible for the occurrence of contact angles greater than 110° on certain leaf surfaces, reside in the wax layer. The hydrophobic properties of some leaves are unaffected by chloroform washing, revealing that superficial waxes play little part in their wettability.
Oxygen and the hatch of eggs and migration of larvae of Meloidogyne javanica
Authors: BAXTER R. I. , BLAKE C. D.
Published: February 2008

The percentage hatch of eggs of Meloidogyne javanica increased asymptotically as the oxygen concentration increased from 0·2 to 21%. Hatch was unaffected by suction pressures of less than pF 3·4 at any oxygen concentration but was decreased by higher suctions. Both the development of embryos and the migration of larvae approached a maximum at an oxygen concentration of about 15%. Hatching was not limited by the rate oxygen diffused through the gelatinous matrix of the egg sac nor was the concentration of oxygen at the surface of an egg sac significantly lower than that within an individual egg. The maximum rate of metabolism appeared to need an oxygen concentration within the egg greater than 10%.
Studies on plant growth‐regulating substances XXVIII. Halogen‐substituted benzoic acids
Authors: JAMES C. S. , WAIN R. L.
Published: February 2008

The plant growth‐regulating activities of chloro‐, bromo‐ and iodo‐isomers in 2,5‐, 2,3,5‐ and 2,3,6‐substituted benzoic acids were assessed in the wheat cylinder, pea segment and pea curvature tests. Their effects in the tomato‐leaf epinasty test were also investigated.

Replacing an ortho‐chloro atom by bromine had little or no effect on activity. An ortho‐iodo substituent, however, reduced activity in the 2,3,6‐substituted series and almost completely inhibited it in the 2,5‐ substituted series. This decreased activity of ortho‐iodo‐substituted isomers is visualized as being due to a steric inhibition of the attachment of the carboxyl group to its receptor unit prior to the initiation of the growth response.
Studies on plant growth‐regulating substances XXIX. The plant growth‐retarding properties of certain ammonium, phosphonium and sulphonium halides
Authors: KNIGHT B. E. A. , TAYLOR H. F. , WAIN R. L.
Published: February 2008

Wheat, pea and dwarf bean seedlings grown under controlled environmental conditions were used to assess the growth‐retardant activity of members of series of chloro‐substituted benzyl‐, trimethyl‐ and tri‐n‐butyl‐ ammonium bromides. The influence on activity of trialkyl groupings other than tri‐methyl and tri‐n‐butyl was also studied using compounds with the 4‐chloro‐benzyl ring structure. 3‐Chloro‐ and 4‐chloro‐benzyltributylammonium bromides were the most effective compounds. The activity was similar to that of 2,4‐dichlorobenzyltributylphosphonium bromide (Phosphon‐D) and they showed little phytotoxicity. A series of chlorophenoxymethyltributylammo‐nium and phosphonium salts were found to have lower activity than the corresponding chlorobenzyl derivatives. Allyldimethylsulphonium bromide retarded the growth of wheat seedlings but, like the aliphatic trimethylam‐monium bromides tested, it was only slightly active in the pea‐seedling test.

The results are considered in relation to the chemical structure of the compounds studied. In particular, the influence of chlorine substitution in the ring of benzyltributylammonium salts on their growth‐retardant activity is compared with the effect of similar substitution on the auxin activity of phenoxyacetic acids.
Growth and yield of six short varieties of spring wheat derived from Norin 10 and of two European varieties
Authors: THORNE GILLIAN N. , WELBANK P. J. , BLACKWOOD G. C.
Published: February 2008

Five short varieties of spring wheat derived from Norin 10: Lerma Rojo 64A (R), Penjamo 62 (P), Sonora 64 (S), Mexico 120 (M), and an unnamed selection obtained from Mexico (X), had grain yields equal to, or only slightly less than those of the taller European spring varieties Kloka (K) and Jufy I (J). Yields ranged from 500 to 580 g/m2 of dry matter. The short variety NBJ115 (N) was severely infected with yellow rust and yielded only 290 g/m2. Total dry weight (excluding roots) of the short varieties was less than of J and K; hence grain accounted for 49 % of the total for the short varieties and 42 % for J and K. Most of the short varieties had fewer ears than the tall ones because sowing difficulties and poor germination produced fewer plants. The relative yields of X, P, R and S seemed to be correlated with their plant and ear densities.

Leaf area duration after flowering (D), based either on total green area or on green area above the flag‐leaf node only, was less for the short varieties than for J and K. The apparent mean efficiency of this area in grain production (grain yield divided by D) was 50% greater for the short than for the tall varieties.

The height of the short varieties ranged from 43 cm (M) to 79 cm (N). K was 92 cm and J 97 cm tall. Differences in height depended on the lengths of the top four internodes and not on number of internodes. Main shoots of all varieties produced seven or eight leaves. All varieties initiated spikelets 45–48 days after sowing. The short varieties flowered 103 days and matured 155 days after sowing; J and K flowered and matured about 1 week earlier.
A survey of foliar diseases of spring barley in England and Wales in 1967
Authors: JAMES W. CLIVE
Published: February 2008

A total of 5,250 acres of spring barley was sampled in proportion to the barley acreage in each of eight regions. The percentage leaf area ‘affected’ by each disease was recorded for the first (flag) and second leaves at a growth stage when the grain was milky ripe. The operation was automated by punching the data directly on to computer paper tape and a programme was written to analyse the results. Mildew was found to be the most important disease, causing an average loss in yield of approximately 18 %, followed in descending order by brown rust 3%, leaf blotch 1 %, yellow rust 1 %, halo spot 1 %. The total loss due to foliar diseases was estimated to be 20–25% of the national barley yield. Diseases were more severe in the southern than northern regions, e.g. mildew severity was three times higher because of the greater popularity of mildew‐susceptible varieties, and the prevalence of weather more conducive to mildew development. Disease severity was not related to previous cropping, and in general the February‐sown crops had more mildew than the April‐sown crops.
Persistence and transmission of Alternaria dauci (Kühn) Groves & Skolko in the semi‐arid conditions of Israel*
Authors: NETZER D. , KENNETH R. G.
Published: February 2008

Daucus maximus, Ridolfia segetum and Caucalis tenella, members of the Umbelliferae, were found to be foliage hosts of naturally occurring Alternaria dauci in Israel. A. dauci was also isolated from Daucus maximus seed.

When infected cultivated carrot petioles were stored dry for 3 months, A. dauci retained its ability to spore, which was lost, however, in alternating wet and dry conditions, an effect paralleled by the loss of mycelial viability in similar soil storage tests. A. dauci colonizing moribund foliage stayed viable longer when the foliage was on the surface than when buried in soil at depths of 10 and 20 cm.

Viable thick‐walled hyphae of A. dauci were found in the inner pericarp layer of Japanese seeds from which infected seedlings developed.
The colonization by Cavariella aegopodii Scop, of carrot plants of different sizes
Authors: Dunn J. A.
Published: February 2008

During a study of the biology of Cavariella aegopodii Scop. (Dunn, 1965) aspects of the role of this aphid as a virus vector have been investigated each year by briefly exposing a succession of potted carrot plants in the field to the incoming winged forms of the aphid (Dunn & Kempton, 1966). Generally fifty plants of each of two different heights, within a range of 1–5 in, have been exposed simultaneously and when the alate C. aegopodii on these have been counted 3–4 days later, the aphid appeared always to have been differentially attracted to the larger plants. This seemed unlikely to be true, however, because as a crop young carrots suffer more severely from this pest than carrots which are a few weeks older, but for some years the aphid was not abundant enough for the situation to be investigated.
The distribution of Myzus persicae (Sulz.) on year‐round chrysanthemums
Authors: WYATT I. J.
Published: February 2008

Large varietal differences in the susceptibility of chrysanthemums to Myzus persicae (Sulz.) were confirmed. The cultivar B.G.A. Tuneful supported forty times as many aphids as Portrait. In the winter, aphids bred more slowly and stabilized at a lower density than in the summer, but retained the same characteristic varietal distribution patterns.

The unintentional introduction of the parasite Aphidius matricariae Hal. resulted in extermination of the aphid within 15 weeks. Mummies appeared in a series of distinct generations 17 days apart with a sevenfold increase between peaks. As this increase was at first not as rapid as that of the aphid, reduction of the pest population was not possible until the aphids had become self‐limiting. Thus, although elimination was achieved, it was not economically satisfactory on susceptible varieties. The modifications needed to employ A. matricariae for commercial biological control under glass are discussed.
The restriction of Cladosporium fulvum and Botrytis cinerea, attacking glasshouse tomatoes, by automatic humidity control
Authors: WINSPEAR K. W. , POSTLETHWAITE J. D. , COTTON R. F.
Published: February 2008

Decreasing periods of atmospheric humidity in excess of 90 and 75 % r.h. by automatic control decreased the incidence of C. fulvum and B. cinerea and sometimes increased tomato yields. The desired value of humidity was not always achieved but nevertheless environments which were both physically and biologically different were obtained with humidistats set at 90 and 75 % r.h. in glasshouses maintaining two temperature régimes–20 °C day and night, or 20 °C by day and 13 °C at night.

Less B. cinerea and C. fulvum occurred on tomatoes grown constantly at 20 °C than on those grown in conditions with lower night temperatures. In the latter regime the end‐of‐season incidence of C.fulvumvas decreased from 25.0% where humidity was not controlled to 2.8% and 0.0% where humidistats were set at 90 and 75 % r.h. In the same conditions the proportion of blemished fruit damaged by B. cinerea decreased from 2.6% to 1.6% and 0.2%.
Biochemical changes in French bean pods infected with Colletotrichum lindemuthianum*
Authors: SMITH I. M.
Published: February 2008

Infection of bean pods with Colletotrichum lindemuthianum leads to the appearance in diffusates of a range of fluorescent and phenolic compounds and of at least two inhibitory compounds. These compounds were found to be absent or in reduced concentration in control diffusates, although the inhibitors were frequently observed to appear at low concentrations without infection. Although sugars and amino acids were found to be released into diffusates, variation in the concentration of these stimulants was found to have little effect on spore germination. Evidence from solvent partition, spectrophotometry and chromatography suggests that the two inhibitors can be tentatively identified with inhibitors previously described from French bean, and both appear to be phenolic substances. It is suggested that inhibitor production may be regarded as part of a general change in aromatic biosynthesis following infection.
The effect of different virus isolates on the expression of tolerance to barley yellow dwarf virus in barley
Authors: JONES A. T. , CATHERALL P. L.
Published: February 2008

A barley variety of Ethiopian origin, with a single Mendelian gene con‐fering tolerance to barley yellow dwarf virus (BYDV), was equally tolerant to a number of isolates of the virus, whereas a susceptible European barley was more susceptible to isolates transmitted by Rhopalosiphum padi L. than to those transmitted by Macrosiphum (Sitobion) avenae (Fab). However, hybrids between these two varieties homozygous for the Ethiopian tolerance gene were more tolerant to ‘mild’ than to ‘severe’ isolates, irrespective of the vector specificity. The European variety was damaged more severely by all isolates when infected early than when infected late in its development, but the hybrids were damaged more severely by M. awraae‐transmitted isolates when infected late.

It is suggested that in susceptible plants the concentration, rather than the virulence, of the virus determines disease severity, whereas the reverse is true in plants possessing a gene which reduces virus multiplication. Virus concentration appears to determine the severity of R. padi‐transmitted isolates, while virulence determines the severity of M. avenae‐transmitted isolates. The latter would also seem to be adapted towards late infection.
Effects of population density on alienicolae of Aphis fabae Scop.
Authors: SHAW M. J. P.
Published: February 2008

A wide range of morphological differences, from apterae to alatae, and of differences in the behaviour of alatae were produced by isolating alatiform nymphs of Aphis fabae on successive days after their birth. Alatiform. nymphs isolated soon after birth developed into the extreme apterous form, whereas when kept in a crowd until shortly before their final ecdysis a large proportion became alatae that flew before depositing young (migrants). Alatiform nymphs isolated on successive days after birth developed either into alatae that flew after depositing nymphs (flyers) or did not fly (non‐flyers). Aphids thus show a continuous polymorphism, comparable to that of locusts, and possibly related to concentrations of juvenile hormone present in the aphid during larval development.
Contribution to the biology of the citrus bud mite, Aceria sheldoni (Ewing) (Acarina: Eriophyidae)*
Authors: STERNLICHT M.
Published: February 2008

In laboratory studies mites of Aceria sheldoni were reared on citrus fruit peels, beneath coloured cellophane hoods, to cater for their thigmotaxis and sensitivity to light of particular wave lengths. Hatching was most successful at 25°C and 98% r.h. but was reduced by low humidities (35–40% r.h.), when abnormal dwarf larvae emerged. The eggs hatched in 3–14 days; the length of a generation (egg to egg) was 12–33 days.

The threshold of embryonic development was 9 °C and that for completion of the life cycle, egg to egg, was 12.5 °C. The average number of eggs laid per female was six (4–8). It increased to twelve (5–19) if the mite, during its larval stages, had been fed on buds. The vitality of both the eggs and the mature mites was tested by exposure to extreme low and high temperatures (below 0 °C, 39 °C): 50% of mites died after 30 min at 30 °C; 50% died after 30 min at –15 °C or lower.
The control of Septoria on celery seed
Authors: MAUDE R. B.
Published: February 2008

In studies on the control of Septoria on celery seed, ¼ and 1 lb (113 and 454 g) samples of infected seed treated by the thiram‐soak method produced disease‐free seedlings under glass and disease‐free plants at maturity in the field. Hot‐water treatment of infected seeds, however, failed to give complete disease control in either situation. Thiram soaking was not harmful to seed germination and produced field crops of equal quality to those obtained from hot‐water‐treated seeds.

In N.A.A.S. extension trials a total of 18½ lb (8.3 kg) of celery seed was treated by the thiram‐soak method and effective disease control was obtained in crops raised from this seed throughout the country.
Resistance of tomatoes to late blight (Phytophthora infestans)
Authors: GÜNTHER ELISABETH , EGGERT DÖRTHE , GRÜMMER G.
Published: February 2008

Race T1 of Phytophthora infestans was first isolated in Central Europe. Tomato varieties carrying the dominant gene Ph were easily infected by T1 but showed a different degree of field resistance. In September 1967 more than 80% of all isolations from the experimental plots at Greifswald were determined as the aggressive race T1. This race was also isolated in a large screening test over several provinces of the GDR from potato and tomato fields where no plants carrying dominant resistance genes were present in the neighbourhood.

The fungus was able to pass from potato leaves or tubers to detached tomato leaves or intact tomato plants (cv. Fanal) without any reduction in sporulation.

The field‐resistant tomato variety Ružový Ker and the highly field‐resistant variety Atom were crossed. In F2 and subsequent generations, young plants were selected following inoculation of 14 mm leaf‐discs. Weak sporulations on the leaf‐discs were almost invariably correlated with a reduced level of infection of fruit in the field. Data from crosses of Atom with more or less susceptible varieties suggested the presence of incompletely dominant genes. It is concluded that at least two genes in the variety Atom control field resistance and the gene‐symbols Phf and Phf‐2 are proposed for them.
Methods of isolating the microflora of moulding, high ‐moisture barley in partially sealed silos
Authors: MULINGE S. K. , CHESTERS C. G. C.
Published: February 2008

Fungi were isolated on agar from barley stored at 18–44% moisture content in partially sealed silos by plating out whole, untreated grain as removed from the silos; surface‐washed whole grain; surface‐washed and then sodium hypochlorite‐sterilized whole grain; hypochlorite surface‐sterilized, dehusked grains cut vertically and plated with cut surfaces to the agar; husks washed several times after removal and plated as small groups. 5 mg aureomycin/100 ml agar was used to suppress bacterial growth. These methods are compared with others in common use.

The isolated species have been tabulated to illustrate the various combinations occurring in grains and in aggregates of husks.
Carnation Italian ringspot virus
Authors: HOLLINGS M. , STONE OLWEN M. , BOUTTELL GINA C.
Published: February 2008

Carnation Italian ringspot virus (CIRV) was obtained only twice in tests on several thousand carnations in Britain during 15 yr. The two isolates, from cultivars ‘Dusty Sim’ imported from Italy and ‘Orchid Beauty’ from the U.S.A., were indistinguishable serologically and in host reactions. CIRV was cultured in Nicotiana clevelandii and assayed in Chenopodium amaranti‐color; it was readily transmitted by leaf‐rubbing inoculation to 62 of 104 plant species tested. Virus‐free carnations were infected only by injecting purified preparations into the stem, and developed chlorotic spots and oval rings in the younger leaves. CIRV was eliminated from Nicotiana clevelandii plants grown for 8 weeks at 36°C. CIRV presents no threat to carnation growing in Britain.

In N. clevelandii sap, CIRV was infective at a dilution of 1/50000 to 1/100000, after heating 10 min at 85 °C (but not 90 °C), and after 16 weeks at 16 °C or 23 weeks at 2 °C. After freeze‐drying, the virus survived at least 7 yr storage under vacuum at room temperature. CIRV was still infective and antigenic after treatment for 30 min at 18 °C with ultraviolet radiation (750 μW/cm2), ultrasound, 2% formaldehyde or 0.2% tri‐sodium ortho‐phosphate (TSP). Infectivity was not wholly abolished in 30 min by 2% TSP. The virus was readily purified by overnight maceration of N. clevelandii leaves extracted in phosphate buffer + butanol, followed by differential centri‐fugation. Purified preparations contained abundant isometric particles c. 29 nm diameter, and like other serotypes of the tomato bushy stunt‐pelargonium leaf curl group, gave three or four specific bands in density‐gradient centri‐fugation. The bands corresponded to four Schlieren peaks in analytical centrifugation. Virus from the lower bands was usually less invasive in N. clevelandii than from the upper bands, although the material in the different bands contained similar amounts of nucleic acid. Only one antigenic component was found by Immunoelectrophoresis; different serotypes of the TBSV‐PLCV group differed widely in immunoelectrophoretic behaviour. The present cryptogram of CIRV is */*:*/*:S/S:S/*.