bluuebunny/crossref_metadata_2025 huggingface dataset:
Methods of reducing variability in the results of glass‐slide spore‐germination assays of fungitoxicity
Authors: FRICK E. L.
Published: February 2008

When conidial spores of Venturia inaequalis (Cooke) Wint. were germinated on glass, in distilled water only, very little variation was found, but addition of copper sulphate produced a marked variation, particularly between slides.

An examination of the standard cleaning technique showed its inadequacy to produce a chemically clean surface, but the introduction of a cleaning method based on permanganic acid led to a very marked decrease of the total variation.

When copper sulphate was applied as a deposit, with various wetting agents, to slides cleaned by this method, there was no appreciable reduction in the variation. When the wetting agent was applied with the spore suspension, however, a marked reduction was obtained, but the total variation was further reduced to an acceptable level only when the toxicant was applied in the nutrient solution in which the spores were suspended.

A modification of a commercial inverted microscope, to facilitate counting, is described.
Factors in testing fungicides against powdery mildews. I. A slide spore‐germination method of evaluating protectant fungicides
Authors: ZARACOVITIS C.
Published: February 2008

The germination of conidia of Erysiphe betae, E. graminis, E. horridula, E. martii, Oidium begoniae, an Oidium sp. from Crepis taraxacifolia and Uncinula necator was studied on dry uncoated glass slides and on dry slides with the following coatings: cellulose acetate (C.A.); the polyvinyl acetate derivative Gelva 7; nitrocellulose (collodion); and ethyl cellulose. Slides dusted with conidia were incubated at 21±1° C. in a saturated atmosphere in the dark. Germination over 85% and as high as 96±4% was obtained on slides coated with C.A. or Gelva 7. The germination on slides coated with collodion was lower and abnormal, the germ‐tubes growing away from the substrate.

The possibility of studying the toxicity of chemicals towards conidia of powdery mildew fungi by incorporating them into a C.A. layer used as a coating for glass slides was examined. ‘Dinocap’, a captan analogue and members of a homologous series of n‐alkyl fatty acids were used, with conidia of E. betae, E. horridula, E. martii and O. begoniae as test organisms. The results obtained demonstrated the potentialities of the method.
Ecological characteristics of nematode‐trapping Hyphomycetes
Authors: COOKE RODERIC C.
Published: February 2008

Conidial germination in sixteen nematode‐trapping Hyphomycete species in amended and unamended soil was studied. On the basis of the pattern of germination the fungi could be divided into two ecological groups: a sensitive group where conidia or germlings quickly gave rise to trapping organs and an insensitive group in which little trap formation occurred. The significance of this in relation to biological control of plant‐parasitic nematodes is discussed.
Observations on the effects of chlorine on the larvae of oysters (Ostrea edulis(L.)) and barnacles (Elminius modestus(Darwin))
Authors: WAUGH G. DUNCAN
Published: February 2008

The possibility that chlorine, which is used to prevent fouling of cooling‐water circuits in industrial plants, could be harmful to oyster larvae is considered. Oyster larvae have been exposed for varying periods to chlorine concentrations as high as 200 p.p.m.; in addition they have been subjected to a temperature shock of the order of a 10° C. rise above ambient. At chlorine concentrations normally encountered in industry (up to 10 p.p.m.) the larvae are unharmed and are capable of growing to the pre‐settlement stage. At concentrations of 20 p.p.m. a substantial proportion is still capable of survival and growth, but at concentrations of between 50 and 200 p.p.m. survival and growth is poor.

The nauplii ofElminius modestusare far more sensitive to chlorine and the majority are killed by concentrations as low as 2·0 p.p.m.

The implications of this work are discussed and the need for confirmatory field trials is emphasized, as is the possible side effect of chlorination and heating in reducing or destroying the food supply of the larvae.
The uncoupling of oxidative phosphorylation in pea shoot mitochondria by 3,5‐diiodo‐4‐hydroxybenzonitrile (ioxynil) and related compounds
Authors: KERR M. W. , WAIN R. L.
Published: February 2008

The effect of the new herbicide, ioxynil, and several related compounds, on the oxidative phosphorylation of respiring, isolated pea shoot particles has been studied. Ioxynil and its analogues were found to depress the uptake of inorganic phosphate and, to a lesser extent, of oxygen by the particles; the calculated P/O ratio was eventually reduced to zero. The effect of ioxynil was far greater than that of the well‐known uncoupling agent 2,4‐dinitrophenol and was similar in magnitude to that of the contact herbicide dinitro‐ortho‐cresol.
Inhibition of the ferricyanide‐Hill reaction of isolated bean leaf chloroplasts by 3,5‐diiodo‐4‐hydroxybenzonitrile (ioxynil) and related compounds
Authors: KERR M. W. , WAIN R. L.
Published: February 2008

The effect of ioxynil and several related compounds on the photoreduction of ferri‐cyanide by isolated bean leaf chloroplasts has been studied.

In general, a close correlation was found between the herbicidal activity of these compounds and their capacity to inhibit the photoreduction; ioxynil was highly active. The established weedkiller dinitro‐ortho‐cresol (DNC) which is a less potent contact herbicide than ioxynil, was also much less effective as an inhibitor for this reaction.
Aqueous formulations of pyrethrum for controlling phytophagous Arthropoda—an evaluation using bioassay techniques
Authors: YULE W. N.
Published: February 2008

Bioassay techniques were used to compare the toxicities of formulations of pyrethrum containing different amounts of surface‐active agents (mainly non‐ionic condensates of ethylene oxide) and synergists (Bucarpolate, piperonyl butoxide, S 421 and Sulfoxide). Phytophagous species of Arthropoda used in the tests were: Acyrtho‐siphon pisum Harris (Aphididae); Phaedon cochleariae F. (Chrysomelidae); Pieris brassicae L. (Pieridae); and Tetranychus telarius L. (Acarina, Tetranychidae).

The insects were dosed by spray tower, and the mite by dipping infested leaves. The LC50 pyrethrins with unsynergized formulations were: aphid (adult), 150 p.p.m.; beetle (adult), 50,910 p.p.m.; caterpillar (third instar), 325 p.p.m.; mite (adult) 1168 p.p.m. Formulations whose wetting powers were increased by adding surface‐active agents were more toxic to the aphid and caterpillar (LC50 of 20 and 50 p.p.m., respectively). Addition of piperonyl butoxide or Sulfoxide to formulations, at up to 8 times the concentration of pyrethrins, increased their potencies for the aphid, beetle and mite by factors of 7–10 times, but were ineffective with the caterpillar. Bucarpolate and S 421 were poor synergists.

A detailed study was made, using Acyrthosiphon pisum, of the synergizing effect of surface‐active agents on formulations of pyrethrum. Hypotheses for their modes of action suggest that toxicity is influenced by the fineness of dispersion of pyrethrum emulsions, and by the improved coverage and penetration of spray on insects, which results from increased wetting power.

The results of bioassay studies are interpreted to indicate that a formulation of pyrethrum synergized with both surface‐active agent and piperonyl butoxide would be a very effective aphicide, with some ovicidal and larvicidal properties, when applied to infested plants as a high‐volume spray.
Studies on plant cuticle
Authors: FERNANDES A. M. SILVA , BAKER E. A. , MARTIN J. T.
Published: February 2008

The isolation from plant tissues of cuticular waxes uncontaminated by cellular extractives is described. Surface waxes are removed by washing leaves and fruits with chloroform at room temperature; other solvents give lower yields of waxes, apparently because of selective solvent action.

A method is described for the quantitative fractionation of apple fruit and leaf waxes, and the levels and distribution of the wax components in the fruit and leaf cuticles are reported. Ursolic acid predominates in the apple fruitlet wax; esters and ursolic acid are the chief components of the wax of apple fruits in store. Ursolic acid also occurs in apple leaf wax; paraffins and esters are important constituents of blackcurrant and rose leaf waxes. The esters of apple, blackcurrant and rose leaf waxes contain long‐chain fatty and hydroxy‐fatty acids of the kind known to occur in apple fruit wax esters.

Recent literature on plant waxes is reviewed.
The effect of kinetin on infection of petunia and tomato leaves with tomato spotted‐wilt virus
Authors: SELMAN I. W.
Published: February 2008

Kinetin supplied to the lower surfaces of petunia leaf strips reduced the number and size of local lesions following mechanical inoculation of the upper surfaces with tomato spotted‐wilt virus' (TSWV). Glucose increased lesion production, but glucose with kinetin reduced it. Kinetin mixed with infective sap did not affect lesion production.

Lesions were increased with increasing water content of leaf strip and the regression equation for the relationship is given. Treatment with kinetin after inoculation reduced lesion production over a wide range of water contents, but was most effective at high values.

Kinetin inhibited virus multiplication in excised tomato leaflets only when supplied at the site of infection and caused some necrosis of veins and midribs. Treated leaflets took up more water than controls and uptake continued for 4 days.

Water uptake by kinetin‐treated petunia leaf strips was less than by controls but continued for 6 days with only slight discoloration of the veins.

It is suggested that the inhibitory effect of kinetin may be associated with a capacity to cause increased activity of ribonuclease in the tissues.
The effect of motley dwarf virus on yield of carrots and its transmission in the field by Cavariella aegopodiae Scop
Authors: WATSON MARION , SERJEANT E. P.
Published: February 2008

In 1959 and 1961, when the willow‐carrot aphid, Cavariella aegopodiae, infested carrots at Rothamsted and Woburn early and severely, crops were infected with motley dwarf virus in late May or early June and yielded about 6 tons of roots per acre. In 1962, when invasion was late and sparse, the crops remained almost uninfected and yielded 24–25 tons/acre. In 1960, when aphids invaded early but multiplied slowly, about 85% of carrots on unsprayed plots became infected in July and August, and the yield was 9.2 tons/acre. Spraying three times with Metasystox starting at an early stage of growth affected yield little in 1961, or in 1962, but increased yield by about 3 tonslacre in 1960.

Field‐plots experimentally infected in 1962 by aphids fed on infected plants in the glasshouse, lost II tons/acre from infection in early June, 8 tons/acre from infection in late June and 6 tons/acre from infection in July. Plots cultured with virus‐free aphids in early June yielded as much as control plots. Experimental infection did not affect yield in 1959 and 1961, when the crop became naturally infected before treatment.

The yields in different years were linearly related to the log. mean weekly numbers of C. aegopodiae caught on sticky traps near the sites, and the regression accounted for much of the variance in yield. The residuals of the log. mean weekly trap‐counts were negatively related to residual weekly rainfall in inches; I in. of rain above average approximately halved the increase in aphids. This may explain the failure of early invading aphids to become numerous at Woburn in 1960, when an inch of rain fell in three consecutive weeks in June.

Treating seed or seedlings with systemic insecticide did not prevent young plants from becoming infected when infective aphids were cultured on them 10–14 days after treatment.

Aphids taken from willow in the spring did not transmit motley dwarf to healthy carrots, but did so after they had fed on infected carrots. Aphids from wild umbellifers often transmitted motley dwarf to healthy carrots.
Persistence and identification of downy mildew Pseudoperonospora humuli (Miy. and Tak.) Wilson in hop rootstocks
Authors: COLEY‐SMITH J. R.
Published: February 2008

Evidence is presented which suggests that Pseudoperonospora humuli persists, in a high proportion of infected hop rootstocks, for at least 4 years in this country, and the grubbing of these rootstocks is recommended. Methods are described for diagnosis of downy mildew during the dormant season in the field and in the laboratory.
The weather and mass flights of Thysanoptera
Authors: LEWIS T.
Published: February 2008

Mass flights of Thysanoptera occur when temperatures rise above the take‐off threshold after migrants have accumulated on plants at temperatures too low for flight. Most species fly in sunny, settled weather with slight convection and a maximum temperature of at least 20°C.
The feeding, growth and reproduction of Aphis fabae Scop. on Viciu fuba under experimental conditions
Authors: BANKS C. J. , MACAULAY E. D. M.
Published: February 2008

The total amount of sap ingested by individual larvae and adult (apterous virgino‐parae) of Aphis fabae on field beans was estimated by adding the weights of honeydew excreted and of water lost by evaporation to increases in body weight during growth and to the weight of larvae born throughout the lives of the adult insects. The quantity of respiratory gases was ignored. Temperature and lighting were kept constant; air humidity was kept high to lessen evaporation, and air movements were eliminated. A machine was made to collect simultaneously the excreta of ten individual aphids to record their total daily excreta continuously from birth to death. Honeydew was also collected daily in mineral oil from other aphids of the same age on similar plants, to estimate the size of the droplets. The mean excretion rate was estimated from the product of the mean frequency of excretion and the mean size of the droplets. The reproductive rate, fecundity and length of reproductive and post‐reproductive life of the adult aphids were also recorded. The larva ingested about 3–5‐45 mg. of sap in a life of 7 days and the adult about 30 mg. during a reproductive life of 21 days; only about 10% was used for growth and reproduction.

The excretion of the adult rose to a maximum of 30–40 drops per day on the third day of adult life and then declined, apparently because of changes within the aphid itself, for when the insects were transferred to fresh plants the excretion continued to decrease. The rate of feeding, which is about equal to the rate of excretion, therefore also decreased as the insect aged but its rate of reproduction remained fairly steady for about 16 days. The swelling of the abdomen and the slight increase in weight during the post‐reproductive life of about 2 weeks suggested that, although excretion had stopped, small amounts of sap continued to be ingested. The aphids ingested about the same amount of sap on two varieties of field bean but were significantly more fecund on one than on the other, a difference probably attributable to differences in the quality of the sap of the two varieties.
‘Lyamungu dieback’ of arabica coffee in Tanganyika
Authors: BURDEKIN D. A.
Published: February 2008

The symptoms of Lyamungu dieback on foliage, branches and roots are described and compared with those of other diebacks of coffee; retention of the dead leaves is a distinguishing symptom. The severity of the disorder is related to the stage of maturity and size of the crop.

The degree of brown flecking of the xylem of the roots reflects the severity of the attack but is not determined by infection by Fusarium oxysporurn. The number and weight of secondary roots is reduced in the first year that the coffee is affected and further reduced if the trees survive into the succeeding year.

Lyamungu dieback has caused serious losses at the Coffee Research Station, Lyamungu, since 1956, and is randomly distributed on estates in northern Tanganyika.

The disorder is associated with heavy cropping and influenced by environment and cultural management. In experimental plots its effects were diminished by artificial shading (which reduced the crop) and by heavy nitrogenous manuring.
The influence of date of origin of the shoot and level of nitrogen on ear size in three perennial grasses
Authors: RYLE G. J. A.
Published: February 2008

In plants of S.24 ryegrass, S.215 meadow fescue and S.37 cocksfoot grown in the field, or with controlled nutrition in the glasshouse, ear size decreased the later the date of origin of the shoot between October and March, before flowering in late spring. The smaller ear size in shoots arising at successively later dates resulted from decreased numbers of primary branches in the ear, and also from the development of fewer florets on each branch. The decrease in number of primary branches was correlated with a decrease in number of unexpanded leaf primordia accumulated at the shoot apex before reproduction.

No effect of nitrogen on ear size was detected when nitrogen was added as ‘Nitro‐chalk’ to plants growing one yard apart in the field. In contrast, plants receiving the smaller rates of nitrogen in the glasshouse generally developed ears with fewer florets on each lateral branch. Lack of nitrogen also decreased the number of primary branches in ears of ryegrass and prevented many shoots of all three varieties from flowering.
Breeding for tolerance to beet yellows virus and beet mild yellowing virus in sugar beet: II. The response of breeding material to infection with different virus strains
Authors: RUSSELL G. E.
Published: February 2008

Isolates of beet yellows virus (BYV) and beet mild yellowing virus (BMYV) were collected from different parts of eastern England. Individual strains of BYV were isolated, from field plants infected with mixtures of strains, using a single lesion technique; all the strains thus isolated appeared to be closely related and there was complete cross‐protection between them. Individual strains of BYV produced symptoms of differing severity on sugar beet and other test plants, and caused different losses of sugar yield in sugar beet in the glasshouse and in the field.

Considerable differences in sodium contents of the roots, and in serological titres of leaf sap, were observed between plants infected with different BW strains. Simultaneous inoculation of two BYV strains, using Myzus persicae Sulz., usually resulted in a disease which was intermediate in severity between the diseases caused by the strains separately. However, in some experiments, simultaneous inoculation of BYV strains caused a more severe disease than was expected and in others a milder disease.

Differences between BMYV isolates were apparently very small in the field and under glass. Field experiments showed that inbred lines and experimental varieties, derived from plants selected for tolerance to BYV and BMYV, were more tolerant than the control varieties when subjected to many different infection treatments. Infection with BYV and BMYV reduced sugar yields and sugar contents and increased sodium and potassium contents of the root. Isolates of BMYV reduced the sugar contents, and increased the sodium contents, more than any strain of BYV. Simultaneous inoculation of BYV and BMYV produced more severe effects on sugar beet than either virus alone. The virus‐tolerant breeding material usually showed smaller reductions in root weight, sugar content and sugar yield than the control varieties, and smaller increases in sodium and potassium contents of the root. The results of experiments indicated that tolerance to one strain of BYV was associated with tolerance to a wide range of BYV strains. Much less is known about BMYV strains but the breeding material yielded well after infection with all the BMYV isolates against which they were tested. It seems unlikely that a rapid breakdown of tolerance would occur if virus‐tolerant sugar beet were widely grown in the field.
The association of split‐leaf blotch virus with nettlehead disease of hops
Authors: LEGG J. T. , ORMEROD P. J.
Published: February 2008

The distribution of two virus diseases, split‐leaf blotch and nettlehead, in hop plantations suggested that infection with split‐leaf blotch virus (SLBV) predisposed plants to nettlehead. Also in three field trials, the incidence of nettlehead disease was higher in plants (var. Fuggle) infected with SLBV than in healthy plants.

The symptoms shown by Fuggle plants infected with SLBV were unaffected by additional infection with hop line‐pattern virus (HLPV), but plants of the varieties College Cluster and Keyworth's Midseason infected with both viruses developed symptoms resembling nettlehead disease in some respects. Such affected plants did not, however, induce nettlehead in plants of the indicator variety Early Prolific to which they were grafted, and therefore nettlehead disease is not the result of dual infection with SLBV and HLPV.

Despite the field association of split‐leaf blotch and nettlehead symptoms, experimental data indicate that SLBV is not a component of the virus complex causing nettlehead disease.
Slug activity in relation to weather
Authors: WEBLEY D.
Published: February 2008

Multiple regression analysis was carried out on the effect of certain meteorological factors on the numbers of slugs attracted by metaldehyde and bran biscuits at Cardiff in the autumn months. By far the greatest reduction in the variance in numbers of slugs attracted each morning was achieved by taking out the effects of two factors: (1) the length of time the biscuits had been exposed, and (2) the average night air temperature. The percentage relative humidity considered alone had little effect on the variance. Regression coefficients, at each site, for factors (I) and (2) on slug numbers appeared to be in close agreement and it is suggested that these figures would serve as a measure of slug activity. Arion hortensis behaved differently from the other species studied, its day‐to‐day variation in numbers not being tied so closely to the meteorological factors examined.

Methods of assessing slug numbers in the field usually rely on the animals' activity. Barnes & Weil (1944) made direct counts on the slugs observable in half‐hourly periods, and Thomas (1944) based estimates of the number attracted to metaldehyde and bran biscuits overnight; Duthoit (1961) used baits of wheat seed in making weekly estimates. Measures of activity, however, may be less directly related to the actual population present than to day‐to‐day climatological variations. The aim of the work described below was to find if it was possible to arrive at more reproducible population estimates by using standard slug biscuits, and allowing for the effect of some of the meteorological variables.
Investigations on fungicides: X. The antifungal activity of 2‐deoxy‐D‐glucose
Authors: ATKIN R. K. , SPENCER D. M. , WAIN R. L.
Published: February 2008

The fungitoxicity of 2‐deoxy‐D‐glucose was examined in spore germination tests using Botrytis cinerea, B. fabae, Alternaria brassicicola, Aspergillus niger, Cladosporium cucumerinum, C. fulvum, Sclerotinia fructigena, Verticillium albo‐atrum and Glomerella cingulata. It proved to be toxic, at concentrations below 10 μg./ml., to all of these fungi except G. cingulata which was resistant to concentrations up to 2000 μg./ml. The effect of a‐deoxy‐D‐glucose on the mycelial growth of these fungi was assessed and again G. cingulata proved to be resistant to high concentrations of the compound, as also did A. niger.

The results are discussed in relation to the known inhibitory nature of 2‐deoxy‐D‐glucose in other systems.
The life‐history of the Indian meal‐moth, Plodia interpunctella (Hübner) (Lep. Phycitidae) in a warehouse in Britain and on different foods
Authors: WILLIAMS GWYNETH C.
Published: February 2008

In a population of Plodia interpunctella living on 4 tons of bagged American maize stored in a Nissen hut, fewer adults than expected emerged in the spring, as many pupae were killed by high temperatures close to the roof. In spite of this, a population of approximately eighteen adults gave rise 3 months later to 643 larvae. There were indications that the life cycle might be completed in 9 weeks, as a second generation of adults started to emerge within this period.

Larvae preferred bags stacked flat to those stacked upright. They tended to occur in the upper parts of stacks, to spin their cocoons in the necks of bags and to remain in their existing sites without showing any indication of migrating.

Of four food materials tested in laboratory studies, no. 3 N. Manitoba Tough wheat induced quickest development, followed by sultanas, American yellow corn and almonds. Of four types of wheat, Australian was more suitable than no. I N. Manitoba or U.S. Northern Spring; English wheat was the least suitable. Milo (N. American sorghum) was as good as no. I N. Manitoba and U.S. Northern Spring wheats, and Plate maize was comparable to English wheat. Groundnuts were less satisfactory and maize meal gave poorer results than any other food.

The main period of emergence of adults was short on those foods which induced the most rapid development but prolonged on those on which the development period was longer. The life cycle was unusually long in a proportion of individuals which were reared on American yellow corn, no. I N. Manitoba wheat and almonds. In these examples the fully grown larvae underwent a long period of rest within the cocoon, suggesting a facultative diapause. Mortality of pre‐adult stages appeared to be higher when the period of development was longer.
Population increase of Ditylenchus dipsaci (Kühn) in the narcissus and the spread of the nematode through the soil
Authors: WEBSTER J. M.
Published: February 2008

A bioassay technique, using forty onion seedlings per pot, was used to determine the soil population of the narcissus race of Ditylenchus dipsaci.

In experiments with narcissus, a progressive increase of D. dipsaci populations was shown, reaching a peak at the end of the growing season. This rise in population in May/June was associated with a rise in temperature. Increase in inoculum gave a significantly larger population in the foliage but not in the bulbs. Nematodes moved actively and were transported passively both up and down within the host plant. The presence of spikkels was associated with nematodes in the active intercalary meristem.

Migration from the plant into the soil and back into the plant, mostly via the base of the bulb, was continuous throughout the growing season and related to the population increase within the plant. Migration of nematodes from wetted dried leaf tissue continued over 60 days. Spread of the nematode through the soil was slow in the absence of external agencies, such as water run‐off and methods of cultivation.
Freshwater Fisheries Research: Introduction
Authors: Pentelow F. T. K.
Published: February 2008

It seems fortunate and appropriate that freshwater fisheries research should at this time be the subject of a symposium organized by the Association of Applied Biologists for this is a field where the line between pure and applied research cannot yet be drawn. Any research, whether it be undertaken solely with the object of advancing knowledge or in order to try to solve some immediately practical problem, is bound to ascertain and elucidate new facts and to produce results for which some practical application can almost immediately be seen. This, of course, arises because the study of freshwater fisheries is still comparatively new even in countries where they are vastly more important than they are here; we are all concerned with fundamental biology and cannot yet decide what is pure and what is applied research.
Dispersion and natural‐enemy action
Authors: FRANZ J. M.
Published: February 2008

Animal dispersion was defined by Wynne‐Edwards (1962) as ‘the placement of individuals and groups of individuals within the habitats they occupy, and the processes by which this is brought about’. This paper deals with a limited aspect of this theme, namely with the influence of the dispersion of host or enemy individuals on their mutual interaction. Obviously, there can only be a relation between feeding organisms and food, between killer and victim, if they coincide in space and in time. Thus, what first seemed to be a limited topic evolves as one of the basic chapters of relations among organisms, that ofcoincidence(cf. Thalenhorst, 1951). It seems to be impossible to deal with space coincidence here without mentioning time coincidence, too. Recognizing the tremendous amount of information available on this subject, I should like to give some examples only, first on enemy action without man's interference and secondly on human action which either favours or disrupts space coincidence of both groups of organisms. For the sake of brevity, the term host will be frequently used for host and prey together and examples will mostly refer to insects.
Sugar and fructosan accumulation in virus‐infected plants: rapid testing by circular‐paper chromatography
Authors: GOODMAN P. J. , WATSON M. A. , HILL A. R. C.
Published: February 2008

The effects of virus infection on the sugar and fructosan contents of plants were studied by circular‐paper chromatography. Fructose and glucose in sugar‐beet leaves were greatly increased, and sucrose slightly, by infection with beet yellows virus (BYV): sugar content was increased more by an avirulent than by a virulent strain. Yellow‐net virus decreased the sugar concentration, whereas yellow‐net mild yellows virus increased it. Sugar accumulated in leaves of magnesium‐deficient plants, which also showed symptoms resembling virus yellows.

Carrot motley dwarf virus increased fructose, glucose and sucrose concentrations in carrot leaves, but in petioles and roots sucrose increased while fructose and glucose decreased: more sugar accumulated in plants infected late than early. Applying menazon to the seed to control aphids increased the sucrose concentration of the roots.

Cereal yellow dwarf virus (CYDV) increased fructose, glucose, sucrose and four fructosans in leaves of oats, an avirulent strain more than a virulent one. Virulent strains of BYV and CYDV apparently decrease photosynthesis more than avirulent ones.
Studies of pelargonium leaf curl virus
Authors: HOLLINGS M. , STONE OLWEN M.
Published: February 2008

Pelargonium leaf curl virus (PLCV) was compared with nine other viruses with isometric particles: broad bean mottle, carnation mottle, carnation Italian ringspot (CIRV), cymbidium ringspot, raspberry ringspot, tobacco necrosis, tomato bushy stunt (TBSV), turnip crinkle and a virus from Trifolium repens.

PLCV was serologically related to CIRV and TBSV, although cross‐reactions between the latter two viruses occurred only with sera from rabbits given one more injection of antigen than usual. Considerable antigenic differences were found among seven isolates of PLCV, and between these isolates and CIRV and TBSV.

Cymbidium ringspot virus was serologically closely related to the virus from Trifolium repens, and both were similar but serologically unrelated to the PLCV‐CIRV‐TBSV group. No other serological relationships were found among the ten viruses. Serologically related viruses gave similar zones after centrifugation in sucrose density‐gradients and, usually similar sedimentation coefficients.

The different viruses infected twenty‐three to forty‐four out of sixty plant species tested. Carnation mottle and turnip crinkle viruses were not eliminated from plants grown at 37d̀C. for 4–6 weeks, whereas the other viruses usually were. The properties of the viruses in vitro were broadly similar.
The control of Alternaria species on leaves of sugar beet infected with yellowing viruses
Authors: RUSSELL G. E.
Published: February 2008

Spraying the foliage with copper or captan increased the sugar yield of beet plants inoculated with two yellowing viruses but did not increase the yield of uninoculated plants. The severity of leaf‐necrosis symptoms, resulting from virus‐inoculation, was decreased by spraying with fungicides. These results could be attributed to a partial control of Alternaria spp. which invariably attack the older leaves of beet plants infected with beet yellows virus (BYV) and beet mild yellowing virus (BMYV). Alternaria infection also apparently affected the processing quality of the roots by lowering the sugar content and increasing the sodium content. It seems, therefore, that Alternaria spp. may have caused much of the damage previously attributed directly to virus infection. Spraying virus‐infected plants with copper or captan caused smaller yield increases in an experimental, virus‐tolerant, variety than in a commercial variety. The virus‐tolerant variety showed a useful degree of inherited resistance to Alternaria and this gave yield increases comparable with those obtained by fungicide treatment of the commercial variety.

These preliminary experiments suggest that Alternaria‐induced necrosis is of considerable economic importance in beet crops infected with yellowing viruses. The losses due to the disease can be reduced by growing resistant varieties and by spraying with fungicides, although the need for further experimentation, using different strains of BYV and BMYV and also different fungicides, is emphasized.
Tomato leaf curl diseases in the Sudan and their relation to tobacco leaf curl
Authors: YASSIN A. M. , NOUR M. A.
Published: February 2008

The viruses causing two tomato leaf‐curl diseases, tomato leaf curl without vein thickening (TLCV) and tomato leaf curl with vein thickening (TVTV), were both transmissible (to tomato and other hosts) by the aleurodid Bemisia tabaci (=B. gossypiperda M. & L.) and by grafting, but not by mechanical inoculation of expressed sap. A third virus, which arrested growth of the shoot apices and caused a disease referred to as tomato condensed top (CT), was transmissible only by grafting and was not studied in detail.

Both TLCV and TVTV belong to the complex of tobacco leaf‐curl viruses described by other workers, but the different effects of the two and their failure to interfere with one another in plants suggest that they are not strains of one virus.

TLCV and TVTV were not transmissible to cotton nor was cotton leafcurl virus transmissible to tobacco, tomato or Datura stramonium L. Virus transmitted from okra with leaf curl caused leaf curl both in cotton and tobacco, suggesting that the okra was infected with a mixture of viruses or with a virus having a new combination of properties. TVTV was transmitted with difficulty to okra, causing vein thickening.
Studies on resistance and tolerance to cocoa viruses in Ghana
Authors: ATTAFUAH ALEX. , GLENDINNING D. K.
Published: February 2008

Cuttings from fifty T17 seedling trees derived from an open‐pollinated pod from the Iquitos selection no. 53 were each infested with fifty infective mealybugs (Planococcus njalensis) carrying either the severe New Juaben strain of cocoa swollen shoot virus or the Kpeve strain of cocoa mottle leaf virus.

All but forty‐seven out of 1000 cuttings treated with CSSV became infected. All Amelonado beans treated at the same time as these cuttings with thirty insects each became infected. There was no evidence of variation in susceptibility to infection with CSSV in the T17 progeny. The infected plants were scored for tolerance; one clone seemed more tolerant and five less tolerant than the remainder. Deposition of mixed pollen in the natural pollination is suggested as the cause of this variation in tolerance in the progeny. There was no evidence of rcsistance and tolerance being associated. Tolerance to CSSV was much higher in the T17 progeny than in Amelonado.

Transmission rates of CMLV were much lower than of CSSV both to the T17 cuttings and to the Amelonado beans, Conditions at the time of infestation clearly affected the transmission rates. No evidence of variation in susceptibility to infection with CMLV was found in the T17 progeny. Plants infected with CMLV were scored for tolerance in only one replicate; there was little evidence of variation and none of an association between resistance and tolerance.
The spread of yellows viruses in sugar beet
Authors: KERSHAW W. J. S.
Published: February 2008

In 1963 and 1964 single sugar‐beet plants (infectors) growing in commercial root crops were infected with either beet yellows virus (BYV), beet mild yellowing virus (BMYV), or both viruses, by viruliferous Myzus persicae (Sulz.). Virus‐free aphids were put on other beet plants. All the M. persicae were then removed, but in 1964 additional ones, either virus‐free or viruliferous, were put on half the plots. More plants subsequently became infected with yellows viruses in plots containing infectors than in those without.

In 1963 more virus spread from BYV than from BMYV infectors; in 1964 the reverse happened. Usually less of either virus spread from plants with dual infection than from those singly infected. In 1964 more virus spread in plots where additional viruliferous apterae of M. persicae were set free on infector plants than in others where the aphids were removed.

The greater spread of BYV than of BMYV in 1963 is attributed to transmission by Aphis fabae Scop., which was exceptionally abundant.

The greater spread of BMYV than of BYV in 1964 is attributed to differences in the virus‐vector relationships of the two viruses when transmitted by M. persicae only.
Influence of steam/air mixtures, when used for heating soil, on biological and chemical properties that affect seedling growth
Authors: DAWSON J. R. , JOHNSON R. A. H. , ADAMS P. , LAST F. T.
Published: February 2008

An apparatus for heating small quantities of soil with steam/air mixtures, at temperatures from 50 to 100d̀ C., is described.

Heating naturally infested soils at 60d̀ C. for 10–30 min. eliminated attack by Rhizoctonia solani Kuhn and pathogens causing brown root rot, so increasing survival and growth of lettuce and tomato seedlings respectively.

Growth in soils heated at temperatures above 80d̀ C. was often less, however, than in soils heated at 60–75d̀ C. Decreases were associated with relatively high soil concentrations of (1) soluble and exchangeable manganese and (2) nitrite. Amounts of ammonia were greatly increased at 52d̀ C., compared with the unheated controls, but those of manganese (water‐soluble and exchangeable) and nitrite were not significantly increased at temperatures less than 65d̀ C.

The damage done to lettuce by R. solani when inoculated to preheated soils usually increased with increasing treatment temperatures. Fewer seedlings survived in soils preheated at 60d̀ C. than in the unheated controls but usually more than in soils preheated at 100d̀ C.
The suppression of ascospore production to facilitate the control of apple scab (Venturia inaequalis (Cke.) Wint.)
Authors: BURCHILL R. T. , HUTTON K. E.
Published: February 2008

Using phenylmercuric chloride (PMC) as the experimental fungicide it has been shown that spraying trees once in autumn at 0.05% and again just before bud‐burst at 0.01% reduced scab infection on blossom truss leaves by over 99% in the following spring. In another orchard 0.01% PMC sprays in autumn and just before bud‐burst, followed by fungicide sprays in spring and early summer, gave complete control of scab. In a third orchard, which was subject to contamination by ascospores from non‐treated apple trees, infection was reduced by 56.9% by one autumn and one pre‐bud‐burst spray of 0.01% PMC without subsequent anti‐scab sprays.
Studies on the aphid, Cavariella aegopodii Scop
Authors: DUNN J. A.
Published: February 2008

The important aphid pest of carrots, Cavariella aegopodii Scop., overwintered in the egg stage on all the common willows (Salix spp.) found in the English Midlands, and showed no host preference between willows on the same site. The eggs were found more frequently on Salix alba and S. fragilis, however, probably because these trees, being larger and generally growing in less sheltered conditions than other species of willow, provide obvious targets for the migrating aphid. Neither eggs nor fundatrices were found on Salix babylonica.

The spring migration from willow to carrot started in May, reached its peak about the beginning of June and was over before July. April‐sown carrots were the most severely attacked and high, damaging aphid populations sometimes developed on these within 6–7 weeks from the onset of immigration.

The number of aphids on carrots declined in July when winged forms developed among the second and third alienicolae generations and dispersed. Some of these winged alienicolae flew to later‐sown carrots, where they did little colonizing but might have furthered the spread of motley dwarf virus.

Natural enemies did not check aphid multiplication: years of highest aphid numbers were those with low rainfall over the first half of the spring migration period.

Seasons when motley dwarf virus disease was most troublesome were those in which C. aegopodii apterae survived on overwintered carrot crops.
Some interactions of kinetin and temperature on tobacco leaves infected with tomato aucuba mosaic virus
Authors: DAFT M. J.
Published: February 2008

Kinetin stimulated production of tomato aucuba mosaic virus in detached tobacco leaves kept at 18 and 28°C., both in newly infected leaves and in those infected a week previously. Kinetin counteracted the ageing effect of exposing leaves at 28°C. In attached leaves kinetin either stimulated or inhibited virus synthesis, depending on the quantity applied and the age of the leaves. Kinetin increased fresh weights, soluble proteins and chlorophyll content of leaves.

In an individual comparison of leaves treated with kinetin and with water, infectivity of extracts and ribonuclease activity were correlated in leaves treated differently at the same temperature, but not otherwise.
The epidemiology of tomato mosaic VIII. Virus infection through tomato roots
Authors: BROADBENT L.
Published: February 2008

Only a small percentage of tomato plants became infected when grown in soil that contained TMV‐infected debris from a previous crop, whether they were set out into this soil or into a layer of partially sterilized soil overlying it. In one experiment, half the plants were infected when grown in sand containing infected tomato debris, and treating the sand–debris mixture with metham‐sodium greatly increased the proportion of plants infected. When shoots were separated from each other virus was not transmitted from adjacent infectors through roots of plants growing in uninfested soil.

When roots were inoculated with TMV, virus was detected in young shoots after periods varying from 3 weeks in seedlings to 6 months in older plants, the average periods being between 10 and 16 weeks. Virus was detected in the roots of many plants, but not in their shoots, when experiments ceased 4–6 months after root inoculation. Plants infected in their roots often showed severe fruit defects in the lower trusses several weeks before mosaic showed in the foliage.
Early‐season control of hop downy mildew, Pseudoperonospora humuli (Miy. and Tak.) Wilson, with streptomycin and protectant fungicides in severely infected plantings
Authors: COLEY‐SMITH J. R.
Published: February 2008

Applications of streptomycin sulphate or protectant fungicides reduced numbers of secondary infections in severely infected hop plantings. When primary infected shoots treated with streptomycin were left on plants for 3 weeks no significant increase in secondary disease resulted. Streptomycin, which was absorbed rapidly by hop plants, could not be detected in expressed shoot sap by early June and had no effect on crop yield or quality.
Effects of photoperiod in the glasshouse on the growth of leaves and tillers in three perennial grasses
Authors: RYLE G. J. A.
Published: February 2008

Leaf and tiller development in vegetative plants of S.37 cocksfoot (Dactylis glomerata L.), S.215 meadow fescue (Festuca pratensis Huds.) and S.24 perennial rye‐grass (Lolium perenne L.) were measured in photoperiods varied by extending a basic period of natural light with low‐intensity artificial illumination so that all plants received approximately the same amount of light each day. Increasing the photoperiod usually increased leaf length and sometimes leaf width, but decreased rate of production of leaves. However, the rate of production of new leaf surface increased with photoperiod. Increasing the photoperiod generally decreased the rate of tillering; thus, plants grown in long days had few tillers with large leaves and sheaths, in short days, plants developed more but smaller tillers.
Breeding for resistance to infection with yellowing viruses in sugar beet
Authors: RUSSELL G. E.
Published: February 2008

Differences in resistance to infection with beet yellows virus (BYV) and beet mild yellowing virus (BMYV) have been observed in virus‐tolerant sugar‐beet breeding material. The results of glasshouse virus‐susceptibility tests usually agreed well with those of field experiments in which plants were exposed to artificial, or natural, infestation with viruliferous aphids. Breeding lines and varieties, which showed resistance to BYV when Myzus persicae Sulz, was used as vector, generally showed a similar resistance to this virus when Aphis fabae Scop. was used. Varieties which were resistant to infection with one virus were not necessarily resistant to the other, although some showed resistance to both BYV and BMYV. Preliminary results suggest that resistance to infection may be controlled by recessive genes which occur widely in sugar‐beet cultivars. The mechanism of this form of resistance is not understood, but it does not appear to be closely associated with resistance to the aphid vectors of the viruses.

The observed differences in resistance to infection demonstrate the possibility of breeding a sugar‐beet variety in which two forms of resistance to virus yellows, tolerance and resistance to infection, are combined.
The influence of increased CO2 concentration and supplementary illumination on growth of tomato seedlings during the winter months
Authors: NEWTON PETER
Published: February 2008

During the period November to March a threefold increase in CO2 concentration had only a small effect on the growth rate of tomato seedlings, variety Eurocross B. Although net assimilation rates were increased, some inhibitory effects of increased CO2 concentration on leaf growth were found when the seedlings were very small. The increase in dry weight was equivalent to that made in a few days by plants grown with naturally occurring amounts of CO2. There was no increase in the rate of flower initiation. Using supplementary illumination for 17 hr. per day with high‐pressure mercury vapour lamps made it possible to produce in November‐December seedlings similar to those grown during March‐April with natural illumination.
Translocation of photosynthetic assimilates in wheat
Authors: LUPTON F. G. H.
Published: February 2008

When 14CO2 was supplied to three varieties of wheat in the field translocation of carbohydrates took place freely throughout young plants, but after the stems elongated the tillers became autotrophic.

The efficiency with which carbohydrate was translocated to the grain increased during the first 4 weeks after anthesis and then fell. Translocation from the glumes and flag leaves was almost entirely towards the grain; that from the second and third leaves was partly towards the grain and partly downward, with evidence of varietal differences in behaviour.