bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of a phytoalexin in controlling lesion development in leaves of Viciafaba after infection by Botrytis spp
Authors: DEVERALL B. J. , VESSEY J. C.
Published: February 2008

Phytoalexin extracted from infection droplets and diseased tissues behaved as an ether‐soluble acid, and was easily separated by solvent partition from other ether‐soluble substances.

The phytoalexin was formed in leaves by apparently healthy cells in advance of hyphae of either Botrytis fabae or B. cinerea, and in response to physical injury. Concentrations of phytoalexin around deep lesions caused by B. fabae were completely fungistatic. B. fabae caused apparent degradation of phytoalexin in lesions, and removed phytoalexin from solutions in vitro much more readily than did B. cinerea.

The lower sensitivity to the phytoalexin, and the possibly related greater ability to metabolize the phytoalexin, are major factors in the greater pathogenicity of B. fabae than of B. cinerea. The same properties largely explain the ability of B. fabae to cause the so‐called ‘aggressive’ phase of the chocolate‐spot disease under some conditions.
Studies of cereal nematode populations and cereal yields under continuous or intensive culture
Authors: GAIR R. , MATHIAS P. L. , HARVEY P. N.
Published: February 2008

In a field experiment on infested sandland from 1955 to 1967, numbers of Heterodera avenae increased only in 1957 and then decreased under both continuous and rotational spring oats (1955‐62) and subsequently under spring barley (1963‐67). Fluctuations in numbers of Pratylenchus neglectus and Trichodorus primitivus were recorded from 1963 to 1967. Cereal grain yields were generally unsatisfactory, but were consistently higher for cereals grown in rotation rather than continuously. Extra nitrogen fertilizer gave slightly improved yields with higher post‐cropping numbers of H. avenae.
The effect of sowing date and plant density on barley
Authors: KIRBY E. J. M.
Published: February 2008

Proctor and Maris Puma barleys were sown in October, early March, and late April at 50, 100, 200, 400 and 800 plants per m2and at low and high fertilizer levels.

Shoot dry matter and grain dry matter showed no significant response to density for the first two sowings, but increased with increasing density in the last sowing. In all sowings the ear number per m2rose with increasing density, and grain number per ear fell, and there were only small interactions between density and sowing date, but the effect on weight per grain differed markedly in the last sowing from that in the first two sowings. Nitrogen concentration per cent of dry matter in the grain and in the straw showed little response to density and the values for both grain and straw were highest in the last sowing. Nitrogen content per m2for both shoot and grain at first rose, and then fell with increasing density. The maximum amount of nitrogen per m2was found at about 100 plants per m2in the early sowings, and at 400 plants per m2in the last sowing. The nitrogen data indicated a loss of nitrogen from the plant at high densities.
Seasonal variations in the sporulating capacity of the fungus causing coffee berry disease
Authors: NUTMAN F. J. , ROBERTS F. M. , FREEMAN G. H.
Published: February 2008

Assessments of the sporulating capacity of Colletotrichum coffeanum Noack in coffee branches (defined as the number of conidia produced per cm2per hour under optimum conditions) have been made for 4 years on a number of different sites in Kenya. An annual rhythm is evident which is essentially similar on all sites and for all years. Early‐season and late‐season peaks are separated by a mid‐season trough. The change in sporulating capacity at any time is negatively correlated with wetness in the immediately preceding period, and daily rainfall can be used as a measure of wetness. The position of the peaks and their duration is defined by the timing of the onset and the duration of the monsoon rains, and is, therefore, subject to considerable variation.

It is suggested that the correct timing of control sprays might be related to the form of the annual curve of sporulating capacity, and be predictable from rainfall records.
Effects of spraying plants with suspensions of inert dusts*
Authors: EVELING D. W.
Published: February 2008

In an examination of possible harmful effects to plants caused by spraying leaves with inert dust suspensions it was shown that Stockalite (kaolin), talc, silica or Tiona W.D. (titanium oxide), suspended in water and sprayed on excised leaves of three species, significantly (P≯ 0·05) increased water loss and penetration of gaseous ammonia; these increases were not caused by soluble chemicals in the sprays, but depended on intimate contact of the dust particles with the epidermis. With a given dust, epidermal permeability increased with increasing concentration and with decreasing size of particles. The increased permeability persisted for at least 4 weeks and was unaltered by partial removal of deposits; deposits on bean leaves caused more visible damage in dry than in humid air. Water losses from sprayed adaxial and abaxial leaf surfaces were similar, but more was lost when deposits dried on turgid leaves than when they dried on flaccid ones.

Spraying potted Coleus plants with a Stockalite suspension increased transpiration and, in one test, decreased the fresh weight of the Coleus shoots.
Hollow heart and poor stands of peas (Pisum sativum L.)
Authors: HEYDECKER W. , KOHISTANI M. R.
Published: February 2008

Laboratory and field experiments on three seed lots of peas have shown that the incidence of the physiological disorder, hollow heart, depends largely on the seed environment. Seeds subjected to excessive watering showed little hollow heart: insufficient watering favoured hollow heart development.

Hollow heart did not directly affect germination and seedling growth but led to rotting of the cotyledons, thus predisposing seedlings to fungus infection.

Over‐watering and over‐firming of soil can severely affect pea stands irrespective of the incidence of hollow heart, and a seed lot susceptible to hollow heart is not necessarily the most susceptible to fungus infection and vice versa.
Persistent effects of seedling treatment on growth of sugar beet in pots
Authors: FRENCH S. A. W. , HUMPHRIES E. C.
Published: February 2008

Further evidence is provided that the environment of sugar‐beet seedlings, or growth substances applied to seedlings, continues to influence growth when the plants are later in other environments.

Sugar‐beet seeds were germinated at 20 °C in 8, 16 or 24 h photoperiods of constant light intensity, i.e. with different amounts of total radiation. When the seedlings had two leaves (15–18 days old) they were transferred to large pots in the glasshouse. Some seedlings were treated with (2‐chloroethyltrimethylammonium chloride) either sprayed on the leaves or applied to the soil, at different times.

The treatments affected areas of individual leaves throughout the growing period; plants raised in 24 h photoperiod had the largest leaves, and those in 8 h photoperiod the smallest. Consequently, 24 h plants had most dry matter and 8 h plants least. Plants given most radiation produced leaves fastest and CCC applied early increased the rate, but as the leaves were smaller, except late in 1967, and died sooner, the leaf area duration was less and so yields were less. CCC applied later did not affect leaf production. There was no interaction between amount of radiation and CCC treatment.

Twenty‐four hour plants had the greatest net assimilation rate (E) early. CCC decreasedEearly, but increased it later and more when sprayed on the leaves than when applied to the soil.

Some factor, possibly pot size, eventually restricted growth and probably diminished the effect of the treatments applied to the seedlings.
Resistance of rape (Brassica napus) to attack by the cabbage aphid (Brevicoryne brassicae L.)
Authors: DUNN J. A. , Kempton D. P. H.
Published: February 2008

Resistance to Brevicoryne brassicae L. attacks in a New Zealand variety of forage rape resulted from a combination of host non–preference and antibiosis. Using clonal plant material obtained from cuttings, only half the numbers of immigrant alate cabbage aphids that settled to reproduce on the susceptible rape were to be found on the resistant rape. The reproduction rate of these alates was about 12 % slower on the resistant plants than on the susceptibles and the young took about 13% longer to mature. Antibiosis then shortened the reproductive life of the apterae by one‐third, reduced their fecundity by nearly 50 % and caused 40% mortality in their progeny. The over‐all effect of this was considerable and under conditions specified in the text could result in the population on the resistant plants being about one‐eighth that on the susceptible plants in under 1 month. The resistant plants lost their resistance on flowering and became normally susceptible to cabbage aphid attack. With maturity, however, the B. brassicae‐resistant plants became slightly resistant to Myzus persicae.
Eggplant mosaic virus, and its relationship to Andean potato latent virus
Authors: GIBBS A. J. , HARRISON B. D.
Published: February 2008

Eggplant mosaic virus (EMV), obtained from Solanum melongena L. from Trinidad, is readily transmitted by inoculation of sap to several solanaceous and a few non‐solanaceous plant species. Purified preparations of EMV contain isometric particles 30 nm in diameter, and with sedimentation co efficients of either 111 or 53 S. The particles have thirty‐two major morphological subunits. EMV is closely serologically related to Andean potato latent virus and has a similar host range, but is more virulent. Also, whereas EMV accumulates fastest in Nicotiana clevelandii leaves at 20–24 °C, Andean potato latent virus accumulates fastest at 15 °C, and fails to attain a serologically detectable concentration at 24 °C. A few symptomatologically or serologically distinguishable strains of EMV were obtained. EMV has properties typical of viruses of the Andean potato latent subgroup of the turnip yellow mosaic group of viruses, and its present cryptogram is */*:*/*:S/S:S/Cl.
The location of raspberry ringspot and tomato black ring viruses in the nematode vector, Longidorus elongatus (de Man)
Authors: TAYLOR C. E. , ROBERTSON W. M.
Published: February 2008

Electron microscopy of thin sections of Longidorus elongatus (de Man) fed on plants infected with raspberry ringspot and tomato black ring viruses showed virus‐like particles in the lumen of the buccal capsule and in the space between the stylet and the guiding sheath. In sections of L. elongatus fed on plants infected with arabis mosaic virus, which it does not normally transmit, a few virus particles were seen in the buccal capsule but none was associated with the stylet guiding sheath. It is suggested that the association of virus particles with the cuticular guiding sheath is an explanation of the specificity of virus transmission evident in L. elongatus.
The control of fungal seed–borne diseases by means of a thiram seed soak
Authors: MAUDE R. B. , VIZOR ANN S. , SHURING CATRIONA G.
Published: February 2008

A method of soaking seeds in an 0·2% aqueous suspension of thiram for 24 h at 30 °C, which had previously been shown to eradicate infection by several fungi, was tested against a further thirteen seed‐borne pathogens. Eleven of these were completely controlled, one was almost completely controlled and one was not adequately controlled by the treatment.

The thiram soak treatment was much more effective than dust treatments with fungicides for the control of many internal fungal pathogens. It was also generally more effective and less damaging than hot‐water treatment.

The ways of applying the method commercially have been investigated and it is being adopted for the treatment of celery, brassicas and red beet.
Production of volatile alkyl sulphides by microbial degradation of synthetic alliin and alliin‐like compounds, in relation to germination of sclerotia of Sclerotium cepivorum Berk
Authors: KING J. E. , COLEY‐SMITH J. R.
Published: February 2008

Onion distillands proved more stimulatory than distillates towards germination of sclerotia of Sclerotium cepivorum. Synthetic allylcysteine and n‐propylcysteine and their sulphoxides stimulated germination of sclerotia when added to soil. Solutions of these compounds in the presence of unsterile soil produced gaseous alkyl mercaptans, sulphides and disulphides which were detected by gas‐liquid chromatography and which stimulated sclerotial germination when drawn through soil containing sclerotia. No volatile sulphides were detected above autoclaved solutions but the atmosphere over propyl and allylcysteines was slightly stimulatory although the corresponding autoclaved sulphoxides showed no such activity. The gases above all four solutions sterilized by membrane‐filtration were not stimulatory. Six common soil bacteria were shown to be capable of degrading the synthetic precursors, causing the evolution of appropriate volatile alkyl sulphides.
The effects of formalin, nabam, irrigation and nitrogen on Heterodera avenae Woll., Ophiobolus graminis Sacc. and the growth of spring wheat
Authors: WILLIAMS T. D.
Published: February 2008

In 1964, nabam (sodium ethylene bisdithiocarbamate), water and three amounts of nitrogen fertilizer were applied to spring wheat on soil treated and untreated with formalin. The experiment lasted for 3 years during which there were eight different formalin, no–formalin sequences. The nabam and irrigation treatments were discontinued when it was found they did not affect the principal pathogens present, the cereal cyst nematode Heterodera avenae and the take–all fungus Ophiobolus graminis. Formalin increased grain and straw yields in the year in which it was applied but led to increased H. avenae populations which adversely affected the succeeding crop. Formalin controlled O. graminis in the year it was applied except on land treated for the first time in 1966. H. avenae seemed to be the main check to growth until about June, and O. graminis later. At the end of the experiment, total grain yields and nematode soil populations were greatest in the plots treated with formalin each year and least in those never treated with formalin. Yield loss from either O. graminis or H. avenae alone could not be assessed because formalin usually controlled both during the season in which it was applied and both were present in untreated plots. However, in 1965, some comparisons of the effects of each pathogen were possible when one occurred in the presence of differing amounts of the other. A doubling of total grain yield over 3 years was accompanied by an eightfold increase in H. avenae in sequences of continuous formalin or formalin 1964 and 1965, whereas yield increases caused by extra nitrogen were not matched by such a big increase in H. avenae. This suggests that formalin might be affecting H. avenae through factors other than increased plant size and vigour, which in themselves would tend to encourage larger nematode populations. In the absence of formalin, H. avenae soil populations either fell or failed to increase.
Effect of seedling treatment on growth and yield of sugar beet in the field
Authors: HUMPHRIES E. C. , FRENCH S. A. W.
Published: February 2008

Sugar‐beet seeds were germinated (1) in a growth cabinet at 20°C lit continuously by fluorescent tubes (L), (2) in a cabinet at 20°C lit by fluorescent tubes for 16 h/day (S), (3) in a cage with glass roof and open sides with natural illumination (N), or (4) in the open ground (D). The seedlings from the cabinets and cage were transplanted to the field when they had two true leaves. Samples were taken on six occasions during growth, and leaf areas and dry weights determined.

There were no differences between treatments in total number of leaves produced or leaf area duration. Leaf area per plant increased fastest on L plants at first, but from mid‐June until end of July drilled plants had the largest leaf surface. From August onwards S plants had the largest area. Although treatment had little effect on growth of the tops, roots grew fastest throughout the season on the plants raised in growth cabinets and the final mean root dry weight of L and S plants was 39% greater than of N and D plants. Throughout the season L and S plants had a larger root:top ratio than plants raised in the cage or drilled directly in the field. The larger roots of plants raised in the cabinets evidently provided a larger sink for carbohydrate and increased the mean photosynthetic efficiency of the leaves over the whole season by 11 % and increased yield of roots by 6 tons/acre.
Studies on plant growth‐regulating substances. XXX. The plant growth‐regulating activity of substituted phenols
Authors: HARPER D. B. , WAIN R. L.
Published: February 2008

The growth‐regulating activity of a number of substituted monophenols and related compounds has been assessed in the wheat cylinder, pea segment, pea curvature and tomato‐leaf epinasty tests and the effect on activity of position, size and electronic nature of the substituents has been studied. The results indicate that, for high auxin activity, electron‐attracting substituents, having certain steric properties must be substituted in the 2‐ and 6‐positions. Furthermore, at least one of these ortho‐substituents must be capable of intramolecular bonding with the hydrogen of the phenolic hydroxyl group. Any substituent in the para‐position to the hydroxyl group leads to complete loss of activity and activity is reduced by meta‐substitution.

This new group of phenolic plant growth regulators is considered in relation to other synthetic auxins from the viewpoints of structural requirements for activity and current theories on mode of action.
Methods of investigating populations of the take‐all fungus(Ophiobolus graminis)in soil
Authors: HORNBY D.
Published: February 2008

Attempts to isolateOphiobolus graminisdirectly from infested soils failed, so host‐infection techniques were used to study soil‐borne populations of the fungus. Extracting organic debris from soils and grading it by wet sieving through standard meshes concentrated the fungus. Fractions were tested for infectivity either as layers in pots of sand or by packing into short lengths of polyvinyl chloride tubing, through which wheat seedlings were grown. Coarse debris (retained by 420 μ aperture sieves) was most infectious and usually caused lesions within 3 weeks; whole soil and especially fine debris (< 420 μ) caused fewer and less severe infections, which often became apparent only after 3 weeks. Slight infectivity of the sediment fractions was attributed to imperfect separation of debris. Soil sampled in crop or stubble rows caused more infections than soil from between rows.

Usually seedling infection was made manifest by root lesions and runner hyphae, but these symptoms were not always plain or conclusive. Many seedling roots that rotted when kept moist and in the light produced perithecia within 6 weeks. Although perithecia formed on some roots where neither lesions nor hyphae were found, they did not form on all diseased roots. More needs to be known about the factors influencing perithecial formation before it can be used as a reliable confirmatory test.
The behaviour of potato mop‐top virus in soil, and evidence for its transmission by Spongospora subterranea (Wallr.) Lagerh.
Authors: JONES R. A. C. , HARRISON B. D.
Published: February 2008

Potato mop‐top virus (PMTV) was best detected in field soils by air‐drying them for more than a week before remoistening and growing seedlings of Nicotiana tabacum or N. debneyi for a 6–10 week period. Infection of N. tabacum was assessed by inoculating sap from roots and shoots to Chenopodium amaranticolor. Similar inoculations from N. debneyi were far less convenient for detecting PMTV than recording leaf symptoms, but slightly more efficient.

Air‐dry soil retained PMTV infectivity for 9 months, when passed through a 50 μ sieve or when diluted with 103 but not 104 parts of steamed soil. Tobacco seedlings were not infected when their roots were steeped in PMTV‐containing tobacco sap. Infective soils contained Spongospora subterranea, spore balls of which resisted air‐drying for more than a year and passed a 50 μ sieve. Roots of susceptible seedlings were infected with PMTV when exposed to spore balls of S. subterranea taken from powdery scabs on PMTV‐infected potato tubers, or to suspensions obtained by steeping, in nutrient solution, roots infected with virus‐carrying cultures of S. subterranea. Plants in several families were hosts of S. subterranea, but probabilities of infection when exposed to spore balls differed greatly between families and only species of Solanaceae were good hosts. The ten species infected with PMTV when grown in infective soil or when exposed to spore balls of S. subterranea taken from PMTV‐infected potato tubers are all members of this family. PMTV seems to be carried internally in S. subterranea spore balls and survived in them for at least a year.

PMTV was transmitted by S. subterranea to Arran Pilot potato, causing yellow blotches in some leaves and spraing in many tubers. However, when newly infected with PMTV in the field, not all Arran Pilot tubers developed spraing. Also, although many spraing‐affected or symptomless but PMTV‐infected tubers carried PMTV‐containing spore balls of S. subterranea, powdery scabs were rarely found near the centres of the rings of primary spraing. PMTV became established in virus‐free soil when PMTV‐infected tubers carrying S. subterranea were planted as ‘seed’ but not when virus‐free tubers bearing powdery scabs were used. 5. subterranea seems the main, and possibly the only, vector of PMTV in the soils examined. S. subterranea did not transmit potato aucuba mosaic virus from potato to N. debneyi or Capsicum annuum.
Effects of soil fumigation on disease incidence, growth, and yield of spring wheat
Authors: EBBELS D. L.
Published: February 2008

Plots were fumigated with various amounts of D‐D or 85% dazomet dust and sown with spring wheat given various amounts of nitrogenous fertilizer. Dazomet increased yield and decreased take‐all disease in the first crop after application, but increased the disease in the second crop. Although D‐D increased take‐all slightly, it increased yield in 1966, but in 1967 it decreased yield and its use was associated with a severe ear deformity. Fumigation had little effect on eyespot, sharp eyespot, root browning (Fusarium spp.), or browning root rot (Pythium spp.), but decreased nematode damage where nematodes were numerous.
Hot‐water treatment of seed as a method for decreasing the incidence of certain cotton and flax seedling diseases
Authors: ABD‐EL‐REHIM M. A. , MICHAIL S. H. , ELAROSI H. , KHAIRY ENAYAT A.
Published: February 2008

Improved pathogen‐free seed germination and better seedling growth were obtained by hot‐water treatments at 60 °C for 10 min of seed of the cotton varieties Karnak and Ashmouni, and at 45 °C for 5 min of seed of the flax varieties Giza 4 and Baladi.

These treatments also reduced pre‐ and post‐emergence losses due to Rhizoctonia solani and Fusarium oxysporum f.sp. vasinfectum in cotton, and to F. oxysporum f.sp. lini in flax, and resulted in better growth of the surviving plants.
Growth of Pseudomonas phaseolicola in susceptible and in resistant bean plants
Authors: OMER M. E. H. , WOOD R. K. S.
Published: February 2008

Race 1 of Pseudomonas phaseolicola introduced into leaves of susceptible Canadian Wonder bean plants multiplied logarithmically for 3–5 days, reaching final populations about 105–106 times the original. In resistant Red Mexican, Race 1 multiplied less rapidly to give final populations about 102–103 times the original. Race 2 behaved in susceptible Red Mexican as did Race 1 in Canadian Wonder. Macroscopic symptoms appeared in leaves when bacterial numbers reached their maxima.

When introduced into the cotyledonary node Race 1 moved more rapidly upwards than downwards, and more rapidly and farther in Canadian Wonder than in Red Mexican. But even in Canadian Wonder the bacterium appeared only sporadically above the node of the first compound leaf. It could be isolated only rarely from chlorotic haloes around necrotic areas in leaves, or from chlorotic leaves not carrying lesions.

Fewer lesions developed and the bacteria multiplied less in older than in younger leaves.

Addition of glucose and casein hydrolysate to inocula of Race 1, separately or together, had little effect on growth in Canadian Wonder or Red Mexican, and the bacterium grew equally well in extracts of susceptible and of resistant plants.

Preinoculation of leaves with an avirulent race reduced the number of lesions caused by a virulent race inoculated later, and also reduced growth of this race in leaves of a susceptible variety.
The influence of darkness on the uptake and movement of diquat and paraquat in tomatoes, sugar beet and potatoes
Authors: BRIAN R. C.
Published: February 2008

Uptake of diquat and paraquat was doubled and occasionally quadrupled when tomatoes were darkened after treatment. The increase was not directly related to the duration of darkness because, after a time, uptake decreased. Three possible explanations for this decrease are considered, namely: diquat exudation from the leaves, downward movement into the roots and the complexing of diquat in plant tissue. Evidence was against exudation from leaves and downward movement into the roots.

Diquat activity also depends on its degree of movement in the plant but the possible influence of other factors is discussed when treatments are made in the afternoon or in the morning after a period of reduced light intensity.

In a CO2‐free atmosphere, uptake and activity increased in light and were comparable to those in darkness. Uptake is therefore not impeded by phyto‐toxic effects of diquat but possibly by the presence of a high concentration of solutes or by photosynthetic intermediates.
Sampling for aphids by traps and by crop inspection
Authors: HEATHCOTE G. D. , PALMER J. M. P. , TAYLOR L. R.
Published: February 2008

The catches of thirty aphid genera and species during 3 years in a suction trap at 40 ft and on a yellow cylindrical sticky trap at 5 ft at Rothamsted and Broom's Barn are tabulated. Suction‐trap catches were the more consistent but both were more effective at recording the first seasonal immigration of Myzuspersicae (Sulz.) and Aphis fabae Scop, than the British Sugar Corporation crop‐inspection scheme.

The catches show the differential attraction to yellow by different species, the effects of local vegetation, and the seasonal distribution of aphids that are crop pests or potential vectors of viruses.
Purification, serological relationships and some characteristics of plum line‐pattern virus
Authors: PAULSEN AVELINA Q. , FULTON R. W.
Published: February 2008

Plum line‐pattern virus (PLV) was purified by homogenizing inoculated leaves of Nicotiana megalosiphon in 0·02 M phosphate buffer, pH 8·0 (1·5 ml/g leaf), containing 0·02 M 2‐mercaptoethanol. The homogenate was centrifuged at low speed and the supernatant liquid was clarified by adjusting the pH to 4·8 with 0·1 M citric acid. The green coagulum was removed by centri‐fugation and the extract adjusted to pH 6·5. After concentrating the virus by high‐speed centrifugation, remaining host protein was precipitated with the gamma‐globulin fraction of antiserum to N. megalosiphon protein. Purification was completed with two cycles of high‐ and low‐speed centrifugation.

Purified PLV had an A260/A280 ratio of c. 1·7 and formed two zones when centrifuged in density gradients at pH 6·0–7·0. The virus was about 30 mμ in diameter in negatively stained preparations. The particles were easily disrupted. PLV was closely serologically related to cultures of plum line‐pattern virus from other areas, but no relationship was found to apple mosaic, Prunus necrotic ringspot or prune dwarf viruses, or to a plum line‐pattern virus from Denmark.
Effects of infection by Phytophthora injestans (Mont.) de Bary on the stomata of potato leaves
Authors: FARRELL G. M. , PREECE T. F. , WREN M. J.
Published: February 2008

Phytophthora injestans infection of potato leaves causes abnormal opening of the stomata in the tissue colonized by the fungus before sporangiophores emerge through them. The affected area, which may be up to 7 mm wide, extends from the necrotic tissue to within 1–2 mm of the advancing edge of the colonizing mycelium. These stomata open wider than those in uninfected parts of the leaf, and do not close in the dark, but closure can be induced experimentally by a high water deficit. Affected guard cells have an increased osmotic value, reduced starch content, and show degradation of the chloro‐plasts. No direct infection of the guard cells has been observed. Autoradiography of infected leaflets which had been exposed to 14CO2 in the light, showed that a zone of increased photosynthesis occurs in the region of wide‐open stomata.
Survival of the causal agents of ‘early‐dying disease’ (Verticillium wilt) of potatoes
Authors: HARRISON J. A. C. , ISAAC IVOR
Published: February 2008

Although the isolation of Verticillium albo‐atrum and V. dahliae from soil and dried moribund stems following infection of a potato crop proved extremely difficult, both fungi were equally capable of overwintering in these substrates and of inducing disease in a subsequently planted susceptible crop. In the absence of a susceptible crop some weed species became colonized.

The two species, however, appeared to differ in their capacity for survival both beneath a monocotyledonous crop and within the potato tubers. Colonization of the roots of wheat, barley, oats, rye and maize was observed with V. dahliae but not with V. albo‐atrum. The latter appeared to be capable of prolonged survival in the tubers, whereas V. dahliae did not remain viable in storage over winter. Consequently only tubers infected with V. albo‐atrum produced infected plants.

The presence of the fungi within the tubers affected neither dormancy nor the initial development of the sprouts. Some correlation was noted between tuber size, the percentage of tubers infected, the distribution of V. albo‐atrum within the tubers and the development of disease in plants subsequently grown from these tubers.
Inherited resistance of sugar beet to aphid colonization
Authors: Lowe H. J. B. , Russell G. E.
Published: February 2008

Results of glasshouse experiments have confirmed that inbred lines of sugar beet differ in each of three types of resistance to Myzus persicae Sulz. and Aphis fabae Scop., namely: resistance to settling, resistance to multiplication, and tolerance. Resistance to multiplication was not invariably associated with resistance to settling, although plants of some lines showed both forms of resistance. Plants that were resistant to settling of alatae were not always resistant to apterae of the same species, and there was not a close relationship between resistance to M. persicae and to A. fabae. The mechanisms involved in resistance to aphids in sugar beet are not understood.

Progenies of plants, selected for resistance to aphids from inbred lines, were often more resistant than progenies of unselected plants. Inheritance of each type of resistance is probably polygenic. The potential value of the different kinds of resistance, in reducing direct feeding damage and controlling the spread of virus yellows in the field, is discussed. The ultimate breeding objective is to produce commercial varieties in which appropriate kinds of resistance to aphids are combined with resistance to virus yellows. The use of such varieties would reduce the need to control aphids in the field by applications of chemicals.
The distribution of bait pellets for slug control
Authors: HUNTER P. J. , SYMONDS B. V.
Published: February 2008

Observations were made on the movement and mortality of Agriolimax reticulatus (Müller) on plots with various densities of metaldehyde and methiocarb pellets. The optimum density of pellets was found to lie between 25 and 100/m2 (pellets 20 and 10 cm apart). This confirmed an estimate derived from a theoretical model.
Influence of soil moisture on the performance of granular systemic insecticides applied to soil
Authors: ETHERIDGE P. , GRAHAM‐BRYCE I. J.
Published: February 2008

Control of aphids by the four systemic insecticides, dimethoate, disulfoton, menazon and phorate, applied as granules below seed potatoes at planting, was investigated under different soil moisture conditions. Results confirmed previous conclusions that dimethoate and menazon are more effective in wet than in dry soils, whereas disulfoton and phorate are equally effective in both. However, even with dimethoate and menazon effects of moisture were small and were probably the result of several different interacting factors.
Species and age specificity of malathion towards the locusts Schistocerca gregaria and Locusta migratoria
Authors: AHMED HAFIZ
Published: February 2008

The toxicity of malathion (2.5 % solution in kerosene) was determined by topical application to the hindwing base of mature adults of Schistocerca gregaria and Locusta migratoria migratorioides and of immature adults of S. gregaria. Mature adults of L. m. migrator ioides were slightly more resistant to malathion than those of S. gregaria. Immature adults of S. gregaria were approximately as susceptible as mature ones (at LD89 level) when the criterion for toxicity was taken as the ultimate death of the dosed insects, but the symptoms of poisoning developed earlier and more strongly in the immature insects.

Penetration of malathion was least in the mature L. m. migratorioides and highest in the immature S. gregaria. The higher rate of activation of malathion in the immature S. gregaria was, however, counterbalanced by a higher rate of hydrolysis.

The toxicity reflected the rate of accumulation of malathion and/or mala‐oxon inside the insect body.
The seasonal carry‐over of Botrytis tulipae (Lib.) Lind., the cause of tulip fire
Authors: PRICE D.
Published: February 2008

Damage done by Botrytis tulipae developed in a variety of ways after planting naturally and artificially inoculated bulbs, the fungus sometimes rapidly invading developing shoots, preventing their emergence. In other instances (a) leaves emerged above ground, but not before being severely infected (the traditional ‘primaries’), (b) leaves emerged uninfected but the flower stalks were attacked at a later stage causing mechanical weakness (and hence frequent snapping), or (c) leaves and flower stalks remained uninfected, with the development of B. tulipae being restricted to its spread from mother to daughter bulbs, which also occurred in (a) and (b).

More emerging shoots were infected when inoculated bulbs were grown at 10° and 15.5° than at 4 °C—an effect suggesting that greater numbers of foliar primaries would develop in mild winters.

The underground transmission of B. tulipae indicates the need for eradicating infections in the bulb, the primary sources of this pathogen.
Testing the viability of fungal sclerotia
Authors: COLEY‐SMITH J. R. , JAVED Z. U. R.
Published: February 2008

Simple methods for producing, handling and testing the viability of sclerotia were used on five fungi, three of which produced sclerotia freely in sand‐maizemeal cultures; the other two did not, and were grown on agar. After air drying, which did not affect viability, sclerotia were buried in the field in bags of nylon fabric. After recovery from soil they were surface‐sterilized with calcium hypochlorite and plated on a medium containing chloramphenicol and streptomycin sulphate. Some fungi, particularly those having basidiomycete affinities, are sensitive to high concentrations of chloramphenicol.
Alterations in peroxidase activity and peroxidase isozymes in virus‐infected plants
Authors: BATES D. C. , CHANT S. R.
Published: February 2008

Peroxidase activity and isozyme patterns were investigated in two leguminous species infected with viruses which produced either local necrotic or systemic chlorotic symptoms. Highest peroxidase activity was recorded when the hosts reacted to infection with necrotic local lesions. No new virus‐specific isozymes were found as a result of infection, but some isozymes, apparently associated with senescence, appeared earlier in extracts from leaves showing necrosis than in extracts from healthy leaves, or from infected leaves showing only very mild chlorosis. Increase in peroxidase activity was accompanied by alteration in isozyme pattern.
The relationship between growth rate and the expression of tolerance to barley yellow dwarf virus in barley
Authors: JONES A. T. , CATHERALL P. L.
Published: February 2008

Barley varieties were most tolerant to infection with barley yellow dwarf virus (BYDV) when they grew rapidly, whether the rate of growth was determined by manipulation of the environment or by the innate genetic constitution of the host. A specific, incompletely dominant gene conditioning a high level of tolerance to the virus in certain rapidly growing genotypes in which it occurred naturally, failed to do so when transferred to slower growing genotypes. However, reintroduction into genotypes capable of rapid growth led to full restoration of the gene's effectiveness. Virus‐free aphids recovered BYDV less readily from quick‐ than from slow‐growing genotypes, all homozygous for the tolerance gene.
Host status of some plants for Xiphinema diversicaudatum (Micol.) and their susceptibility to viruses transmitted by this species
Authors: THOMAS P. R.
Published: February 2008

Forty plant species were grown in pots containing viruliferous Xiphinema diversicaudatum (Micol.) for 15 wk to assess the host range of the nematode in relation to infection with arabis mosaic (AMV) and strawberry latent ring‐spot (SLRV) viruses. Host status for the nematode was determined mainly from changes in total populations, but the presence of eggs in the uteri of females and changes in the numbers of adults provided additional criteria. The nematode multiplied on relatively more woody perennials than on herbaceous crop plants or weeds. Chrysanthemum coronarium was the only plant on which numbers declined significantly below those on the controls.

Most plant species became infected with either AMV or SLRV. Neither virus was detected in eight out of thirteen species of trees and shrubs although four were good hosts for the nematode.

Galling or distortion of the terminal region of fine feeder roots, associated with X. diversicaudatum feeding, was seen on many of the experimental plants.
Effects of population density on alienicolae of Aphis fabae Scop.
Authors: SHAW M. J. P.
Published: February 2008

Apterae reared at different population densities produced alatae among their progeny, but not all these alatae behaved in the same way. Some flew before depositing nymphs (here called migrants), others flew after parturition (flyers) and some never flew (non‐flyers). The proportions of alatae, among the progeny from both uncrowded (‘U’) and crowded (‘C’) parents, that flew before depositing nymphs increased as the population density in which they were reared increased. Both crowded and uncrowded apterous parents produced similar numbers of larvae but, on average, ‘C’ apterae produced 17% more migrants. The proportions of migrants among alate progenies were closely correlated with the proportions of alatae among progenies.
Patterns of distribution of insects near a windbreak of tall trees
Authors: LEWIS T.
Published: February 2008

The distribution of shelter to leeward of a windbreak of tall trees was compared with the pattern of distribution of insects above and within a wheat crop.

The pattern for flying insects blown from elsewhere resembled the shelter profile, in contrast to insects originating in the windbreak, which accumulated immediately behind the trees, and those originating a few metres to windward, which accumulated in a zone between 1/2 and 1 H (10–20 m) to leeward. These patterns were more distinct in direct than in oblique incident winds.

The pattern of infestation of a breeding population of cereal thrips in the wheat resembled the distribution of airborne primary migrants 1–2 months earlier; the pattern of scatophagid flies on the crop also resembled that of airborne populations of other dung feeders originating slightly to windward of the trees.
Development of coffee berry disease in relation to the stage of berry growth*
Authors: MULINGE S. K.
Published: February 2008

The susceptibility of coffee berries to coffee berry disease (CBD) varies with the stage of berry development. It is well known that mature green berries are relatively resistant, while ripening berries are highly susceptible; however, differences in susceptibility of berries during early stages of development have not hitherto been examined in any detail.

Experiments were carried out at a medium‐altitude site (5200 ft) to examine the effect of inoculation, in the field, 4, 6, 10 and 14 weeks after flowering. The highest infection rates occurred when berries were inoculated 6 and 10 weeks after flowering when the berries were expanding rapidly. At 4 weeks, when berries were at the ‘pinhead’ stage, and at 14 weeks, when they were attaining full size, much lower rates were recorded. Comparable results have also been obtained at a high altitude (6000 ft) site.

In an experiment carried out on a long‐rains crop, flowering on 1 March, lesions regularly developed 2–4 weeks after inoculation, whereas in an experiment on a short rains crop, flowering at the end of October, symptom expression was apparently delayed. Possible reasons for this difference are discussed.
Ecology of fungi associated with moist stored barley grain
Authors: MULINGE S. K. , CHESTERS C. G. C.
Published: February 2008

A study of the ecology of fungi associated with moist stored barley grain was carried out on samples from a partially sealed silo in Cumberland. Samples were collected during harvest and after storage at high moisture content in a partially sealed silo. At harvest, the field fungi Alternaria, Fusarium, Cladosporium and Mucor spp. were dominant both in the husks and in the dehusked, surface‐sterilized grain but they were rapidly succeeded by the storage fungi: Aspergillus, Penicillium and Absidia spp. then constituted about 80 % of the initial invasion. At this stage internal grain infection rarely exceeded 5 % compared to 65–80 % infection in the husks. In subsequent months, there was a remarkable increase in invasion, mainly by Penicillium, Aspergillus and Absidia spp. and by yeasts, which appeared both in the husks and in dehusked grain. In the third month of storage, Penicillium cyclopium, P. roqueforti, Absidia corymbifera, Aspergillus candidus, A. terreus and yeasts became dominant. The thermophilous species Aspergillus fumigatus, A. terreus, Absidia corymbifera, Mucorpusillus and Dactylomyces crustaceus were isolated from husks and in dehusked grain incubated at 37 and 45 °C. Most grains were infected significantly by single genera.
The establishment of a new strain of tobacco mosaic virus resulting from the use of resistant varieties of tomato
Authors: PELHAM J. , FLETCHER J. T. , HAWKINS J. H.
Published: February 2008

Tomato varieties with monogenic resistance (tolerance) to tobacco mosaic virus (TMV) were used by British growers for the first time in 1966. Samples of TMV collected before 1966, and in 1967 and 1968, were tested for their ability to produce virus symptoms on a series of isogenic tomato differential hosts differing in three factors for TMV resistance. Samples collected before 1966 yielded only strain o of TMV, which was unable to overcome any of the three factors. Strain 1, able to infect the newly‐introduced resistant varieties, was found with increased frequency after 1966. It was found less frequently on nurseries which had resumed growing susceptible varieties, suggesting that in these it may be unable to compete successfully with strain o. The dangers of indiscriminate release of varieties protected from disease by only one gene are discussed.
Some effects of barley yellow dwarf virus on spring and winter cereals in glasshouse trials
Authors: DOODSON J. K. , SAUNDERS P. J. W.
Published: February 2008

The tolerance of spring and winter varieties of wheat, oats and barley to infection by barley yellow dwarf virus (BYDV) was examined in glasshouse tests. Severely affected plants were stunted and grain yields were considerably decreased because of decreases in both ear number and numbers and sizes of grains. Winter barley varieties were very susceptible and many were killed by BYDV infection. The winter wheat varieties were more widely tolerant than those of oats and barley.

Individual seedling symptoms, although correlated with reductions in yield, could not be relied upon for accurate classification of all varieties in order of their susceptibility to infection. Symptoms of seedling infection incorporated into an index of infection permit estimates to be made o eventual decreases in yield by applying the formula

DY = 1.4 × (SH+LA+LL)+18.

Thus decrease in grain yield (DY) can be related to decreases in height (SH) and leaf length (LL) and increases in leaf area discoloured (LA) in seedling plants infected with BYDV.
Plant and soil nematode population changes in wheat grown continuously in ploughed and in unploughed soil
Authors: CORBETT D. C. M. , WEBB R. M.
Published: February 2008

In general, more migratory plant‐parasitic nematodes are found in soil under cereals drilled after ploughing than in unploughed land drilled after being sprayed with weed‐killer; but some non‐parasitic nematodes are more numerous in the unploughed, herbicide‐sprayed soil.

Spraying a mixture of DDT, diazinon, chlordane and thionazin on the soil before drilling did not affect populations of soil nematodes.
Decline viruses of pawpaw (Carica papaya L.) in East Africa
Authors: KULKARNI H. Y.
Published: February 2008

Three viruses or virus strains were isolated from pawpaw showing field decline symptoms in Tanzania and Kenya, where they are of wide occurrence. Each virus caused a distinct type of local lesion in Chenopodium quinoa; a fourth type of local lesion was induced when transmission was from a source containing two of the three viruses. When re‐inoculated to pawpaw, alone or in combination, they caused stunting and decline symptoms similar to those observed in the field.

Two were recovered from pawpaw pollen; none was transmitted through seed or from fruit to fruit, nor was any vector found.

Purified preparations of the three viruses contained stiff rod‐shaped particles 750 times 12 nm.

Latex from pawpaw petiole and fruit totally inhibited sap transmission.
Weed plants as sources of cucumber mosaic virus
Authors: TOMLINSON J. A. , CARTER ANNE L. , DALE W. T. , SIMPSON CAROL J.
Published: February 2008

Severe yellowing and stunting was widespread in lettuce crops in Britain in 1968. Cucumber mosaic virus was consistently obtained from affected plants and from weeds which were prevalent in lettuce fields. Infection was most frequent in Stellaria media but also occurred, more or less commonly, in Senecio vulgaris, Urtica urens, Tripleurospermum maritimum ssp. inodorum, Capsella bursa‐pastoris, Lamium purpureum and Sonchus oleraceus. Most infected weeds were symptomless. Infected weeds were still common in January‐April 1969 and are considered to be a major overwintering source of the virus for aphid transmission to lettuce.
The quantitative estimation of the infection of bean seed with Pseudomonas phaseolicola (Burkh.) Dowson
Authors: TAYLOR J. D.
Published: February 2008

A routine laboratory method for the detection of Pseudomonas phaseolicola in bean seed is described. The method will detect low levels of seed‐borne infection and has been used in a statistical procedure (the most probable number method) to give an estimate of percentage infection. Infection in seeds harvested from heavily infected crops varied from 10 to 1%, compared with from 1% to less than 0.1% in commercial seed stocks. A high proportion of infected seeds failed to produce infected plants and this may account for the very low levels of primary infection reported in the field. Removal of seeds showing possible ‘symptoms’ of disease reduced, but did not eliminate, infection from seed stocks.