bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural changes in tea leaves during ‘orthodox’ black tea manufacture
Authors: SELVENDRAN R. R. , KING N. R.
Published: February 2008

Changes in fine structure of upper epidermal and palisade cells of fresh, withered, rolled, ‘fermented’ and ‘fired’ tea leaves have been studied. In the fresh immature leaves, the polyphenols are located mainly in the vacuoles of the first two to three layers of upper palisade cells. Loss of water during withering causes slight disorganization in the fine structure of the organelles. Rolling causes extensive disorganization of the organelles, membranes and cell walls. The chloroplast membranes, which are rich in lipoproteins, rupture and parts of it vesiculate. These controlled and defined changes in fine structure leading to cell death, characterized by cleavage of cell walls in certain areas, rupture of the membranes, organelles and their inclusions, followed by‘cramped plasmolysis’ of cellular contents, throw more light on the biochemical changes that take place during tea manufacture.
Association of cocksfoot mild mosaic and cocksfoot streak viruses in Dactylis glomerata and their simultaneous transmission by aphids
Authors: CHAMBERLAIN J. A. , CATHERALL P. L.
Published: February 2008

Macrosiphum (Sitobion) fragariae transmitted cocksfoot mild mosaic and cocksfoot streak viruses two to three times more frequently from plants in which they occurred together than from plants in which they occurred alone. In cells of doubly infected plants, particles of the two viruses commonly occurred in close association.
Factors affecting the control of seed‐borne Septoria nodorum by laboratory application of phenyl mercuric acetate to wheat seed
Authors: BATEMAN G. L.
Published: February 2008

The effects of distribution of fungicide between seeds and of post‐treatment storage on control of seed‐borne Septoria nodorum by phenyl mercuric acetate (PMA) were investigated. Uneven distributions of fungicide were obtained by mixing treated with untreated seed. Redistribution of PMA occurred during initial mixing of the seed and during storage; this increased the effectiveness of fungicide in the mixed seed batch when the application rate was moderately high (0–5 jug Hg/seed). Redistribution apparently occurred over the seed surfaces and from seed to seed rather than by penetration into the seeds. Penetration into the seed by PMA was relatively unimportant in controlling S. nodorum.
Glasshouse evaluation of systemic compounds, derivatives of dithiocarbamic acid and other fungicides for the control of clubroot
Authors: BUCZACKI S. T. , CADD S. E.
Published: February 2008

Seventy‐one fungicides were mixed with an artificially infested soil/peat mixture in which cabbage seedlings were subsequently grown in pots in a glasshouse. The incidence and severity of clubroot and any toxic effects on the plants were recorded. Carbendazim, chloraniformethan, maneb, ferbam, zinc N‐methyl dithiocarbamate, zinc diethanolamine dithiocarbamate and ziram were selected as suitable for further evaluation as they gave disease control as good as the standard calomel treatment and were of comparably low phototoxicity.
Field evaluations of systemic fungicides and derivatives of dithiocarbamic acid for the control of clubroot
Authors: BUCZACKI S. T. , CADD S. E. , OCKENDON J. G. , WHITE J. G.
Published: February 2008

Dipping the roots of cabbages in aqueous suspensions of benzimidazole‐derived systemic fungicides before transplanting gave yield increases comparable with, those obtained after similar treatment with 10% calomel suspensions. In conditions of moderate clubroot infection, 0–2 % suspensions gave adequate crop improvement, but on a site where disease development was more severe, 0–4 or 0–5 % concentrations were necessary for a comparable effect. In a preliminary study, good disease control and marked crop improvement were obtained when benzimidazole‐derived systemic fungicides were incorporated to a depth of 15 cm at doses equivalent to 100 or 250 mg/kg of treated soil. Further study on lower doses and on soil incorporation techniques would be required before any large‐scale use of an incorporation method could be contemplated.
The effect of formalin on potato cyst‐nematode, Heterodera rostochiensis
Authors: WHITEHEAD A. G.
Published: February 2008

Applying 5 ml of a 38% aqueous solution of formaldehyde to 1500 ml of sandy loam prevented potato cyst‐nematode, Heterodera rostochiensis, from increasing on the roots of Arran Banner potatoes planted in the soil and increased the weight of tubers produced. A comparable dosage applied to plots of sandy loam and sandy clay in winter did not prevent the nematode from multiplying on Pentland Crown potatoes but increased tuber yields. Smaller amounts of formalin had less effect on tuber yields and drenching dilute formalin solutions onto the soil was no more effective than incorporating undiluted formalin into the soil by rotavation 15 cm deep.
Relations of the semi‐persistent viruses, parsnip yellow fleck and anthriscus yellows, with their vector, Cav arietta aegopodii
Authors: ELNAGAR S. , MURANT A. F.
Published: February 2008

Studies were made of the relations of parsnip yellow fleck virus (PYFV) and its helper virus, anthriscus yellows (AYV), with their aphid vector, Cavariella aegopodii. Apterous insects were more efficient vectors than alates; apterous nymphs were as efficient as apterous adults. C. aegopodii never transmitted PYFV in the absence of AYV, but aphids carrying both viruses infected some test plants with one or other virus alone. C. aegopodii that fed first on a source of AYV and then on a source of PYFV transmitted both viruses to test plants, but aphids that fed on the sources in the reverse order transmitted only AYV. Test plants receiving some aphids from a source of AYV, and others from a source of PYFV, became infected only with AYV.

C. aegopodii acquired AYV or the AYV/PYFV complex from plants in a minimum acquisition access time (AAT) of 10–15 mm and inoculated the viruses to test plants in a minimum inoculation access time (IAT) of 2 min. Increasing either AAT or IAT, or both, to 1 h or longer increased the frequency of transmission of each virus. Starving the insects before the acquisition feed on AYV or AYV/PFYV sources did not affect transmission. Aphids already carrying AYV acquired PYFV from plants in a minimum AAT of only 2 min; they acquired and inoculated PYFV in a minimum total time of 12 min. The data suggest that AYV is confined to deeply lying tissues whereas PYFV is distributed throughout the leaf. C. aegopodii transmitted both PYFV and AYV in a semi‐persistent manner: the aphids retained both viruses for up to 4 days but lost them on moulting. Neither virus was passed to progeny of viruliferous adults. Earlier results suggesting that AYV is a persistent virus may have been caused by contamination of the AYV culture with carrot red leaf virus.
The role of the helper virus, anthriscus yellows, in the transmission of parsnip yellow fleck virus by the aphid Cavariella aegopodii
Authors: ELNAGAR S. , MURANT A. F.
Published: February 2008

Transmission of parsnip yellow fleck virus (PYFV) by the aphid Cavariella aegopodii occurs only when the aphids are also carrying the helper virus, anthriscus yellows (AYV). None of five other viruses tested was able to act as helper. In experiments in which aphids were allowed to feed through membranes on crude or treated extracts from infected plants, aphids already carrying AYV acquired PYFV, but virus‐free aphids failed to acquire either AYV or PYFV. PYFV was not transmitted by insects injected with haemolymph from aphids carrying both viruses, or with purified preparations of PYFV. PYFV was transmitted when AYV‐carrying aphids, except those whose stylets had been removed, were contaminated externally with PYFV preparations.

Ultraviolet irradiation of infected leaves did not prevent aphids from acquiring AYV, presumably because it is confined to deeply‐lying tissues. AYV‐carrying aphids could acquire PYFV from u.v.‐irradiated leaves after acquisition access times of 2 h but not after feeds of only 2 or 15 min (which are adequate on unirradiated leaves), suggesting that PYFV is present in all parts of the leaf. No ‘helper agent’ distinct from AYV itself was detected in these experiments or in experiments on minimum acquisition feeding time or maximum period of persistence in the aphid. U.v.‐inactivated PYFV competed with infective PYFV for retention sites in AYV‐carrying aphids, whereas AYV apparently did not. It is suggested that there is no helper agent for PYFV, other than AYV particles. The possibility that there is one for AYV is not excluded.
Effects of awns on the photosynthesis and yield of wheat, Triticum aestivum
Authors: OLUGBEMI L. B. , AUSTIN R. B. , BINGHAM J.
Published: February 2008

Two pairs of awned and awnless near‐isogenic lines of winter wheat were used in a field study in which canopy enclosure apparatus and carbon‐14 dosing were employed to assess the contribution of the awns to photosynthesis and grain yield. Awns contributed an average of 12‐2% to canopy gross photosynthesis but did not increase the net photosynthesis of the complete canopy. The presence of awns decreased photosynthesis in the remaining ear structures and in the flag and penultimate leaf laminae. Seven days after dosing during the phase of rapid grain filling, 80% of the carbon recovered was located in the grains. The awns intercepted 9% of the incident visible radiation when fully green, and senesced at similar rates as the ears and flag leaves.

In a second experiment the effect of awns on grain yield and its components was investigated in crosses segregating for height and presence of awns. Awns did not increase grain yields in either experiment. It appears that for British conditions in the absence of severe drought there is little advantage to be gained at present by breeding awned varieties of wheat.
The incidence of benomyl tolerance in Verticillium fungicola, Mycogone perniciosa and Hypomyces rosellus in mushroom crops
Authors: FLETCHER J. T. , YARHAM D. J.
Published: February 2008

Of the 229 isolates of Verticillium fungicola examined 63 % were found to show some benomyl tolerance and 53% were very tolerant having EDg, values in excess of 50 ppm. There was a tendency for the tolerant isolates to have a slower growth rate than the sensitive ones on unamended potato dextrose agar (PDA) and forty‐five isolates (19 %) showed growth stimulation at 5 ppm benomyl. No major differences were found in ten isolates of V. fungicola tested on benomyl, thiabendazole and thiophanate methyl agars or of twelve isolates compared on benomyl and carbendazim hydrochloride agars.

Tolerant isolates of V. fungicola and higher levels of crop loss were linked in the east and north of the country but not in the south‐east. Tolerance was not found in sixty‐six isolates of Mycogone perniciosa or twenty‐four of Hypomyces rosellus.

Benomyl was used on 89 % of the farms in the survey either applied to the casing (34%) or as a spray (55 %) or both (10%).
Use of X‐rays as a biological micro technique: an example investigating the reproductive development of cowpea (Vigna unguiculata)
Authors: ELY R. V. , MINCHIN F. R. , SUMMERFIELD R. J. , NDUNGURU B. J. , STEWART K. A.
Published: February 2008

A series of preliminary trials designed to investigate the potential of long wavelength X‐rays to examine very early stages of both vegetative and reproductive growth in cowpea have been completed. This technique should allow us to ‘pin‐point’ at what stage of development a lateral bud becomes reproductive and what anatomical features precede flower development or end in flower abortion.
Factors affecting the field infection of potato tubers of different cultivars by blight (Phytophthora infestans)
Authors: LAPWOOD D. H.
Published: February 2008

The relationships between rain and blight (Phytophthora infestans) were studied in unsprayed crops of cultivars differing widely in foliage and tuber susceptibility. The occasions when tubers were infected depended on rain and not cultivar, but numbers of tubers infected after rain was affected by the blight susceptibility of the cultivar. Infected tubers were first found when less than 5 % (BMS key) of the potato foliage was infected but few fresh infections occurred when 50–75% of the foliage had been destroyed. Some tubers were infected after 8 mm rain (tubers near the surface with even less) but large increases in numbers of tubers infected usually occurred only after 25 mm or more had increased soil moisture to above ‘field capacity’ around the tuber for at least 24 h.

The most susceptible cultivars Ulster Ensign and Arran Banner had all plants with some tuber blight, and some plants with all tubers affected and often many lesions per tuber. Cultivars of intermediate susceptibility, King Edward and Up‐to‐Date, had some plants without blighted tubers, many with a few and very few with all. The more resistant cultivars Majestic and Arran Viking had many plants without infected tubers and many lesions that aborted while still necrotic threads, so that the fungus did not spread. Most infections occurred through tuber eyes, lenticels or sometimes growth cracks. The distribution of blight lesions on tubers differed in the different seasons, for example, lenticels were most commonly infected on Arran Banner and Ulster Ensign and eyes on King Edward, Majestic and Arran Viking.

In late or slowly developing attacks, lesions on stems became more numerous and larger than in fast, early attacks and were prolific sources of spores on King Edward and Up‐to‐Date but not on Majestic and Arran Viking. Because much rain water runs down the stems of Up‐to‐Date and King Edward, stem lesions can provide an important source of inoculum for tubers.
Laboratory studies of potato tuber resistance to infection by Phytophthora infestans
Authors: WALMSLEY‐WOODWARD DIANNE J. , LEWIS B. G.
Published: February 2008

Eyes and lenticels on tubers of cvs King Edward, Record, Maris Peer and Majestic gradually became more resistant to infection by Phytophthora infestans as the growing season progressed. Lenticels of Record and Majestic, and eyes of Maris Peer and Majestic were more resistant than those of King Edward. Differences in resistance between cultivars were apparent at all concentrations of inoculum.
Some properties of grapevine Bulgarian latent virus
Authors: MARTELLI G. P. , GALLITELLI D. , ABRACHEVA P. , SAVINO V. , QUACQUARELLI A.
Published: February 2008

Grapevine Bulgarian latent virus (GBLV), obtained from symptomless vines grown in Bulgaria, was readily transmitted by inoculation of sap to a restricted range of hosts. The virus was re‐inoculated into virus‐free rooted cuttings and seedlings of several grapevine cultivars without inducing symptoms. Purified preparations of GBLV contained isometric particles c. 30 nm in diameter which sedimented as three components at52, c. 120 and 1275, respectively. The slow‐sedimenting component (T) contained non‐infective protein shells, whereas the two heavier classes of particles (J5X, B2) each contained one molecule of single‐stranded ribonucleic acid (RNA) with mol. wts of 2.1 and 2.2 times 106 daltons. The RNA content of B1 and B2 components were 39 and 41 % by particle weight respectively. The capsid was composed of one type of protein with a mol. wt of 54000. GBLV did not react with antisera to any of twenty‐eight viruses with isometric particles. Its present cryptogram is R/1: 2‐2/41 +2‐1/39:S/S:S/*.
Electron microscopy of cocksfoot streak virus and its differentiation from ryegrass mosaic virus in naturally infected Dactylis glomerata plants
Authors: CHAMBERLAIN J. A. , CATHERALL P. L.
Published: February 2008

The length and rigidity of some cocksfoot streak virus (CSV) particles were greater (1) in ammonium molybdate negative stain at pH 5 than at pH 8 and (2) when magnesium was added either directly to extracted plant sap or indirectly via increased plant uptake. Most CSV particles were flexuous and 750–760 run long in low concentrations of magnesium but many were rigid and 800–810 nm long in higher concentrations. In sodium phosphotungstate and ammonium molybdate at pH 5, frequency distributions of particle lengths from cocksfoot plants infected with both CSV and ryegrass mosaic virus (RMV) produced two modal peaks, one at less than 700 nm (RMV) and the other at more than 750 nm (CSV); in ammonium molybdate at pH 8, however, only one peak (at 725 nm) was resolved.

In ultrathin sections of CSV‐infected cocksfoot leaves, virus‐like particles were scattered or in bundles within the cytoplasm, or aligned in aggregates near the tonoplast. Some cells contained pinwheel inclusions, often with attached or associated laminar plates and occasionally with scroll‐like or circular tubes. These CSV‐induced inclusions were easily distinguished from those induced by RMV, even when both types occurred in the same cell.
Root and shoot development in peas
Authors: ALT‐KHAN S. T. , SNOAD B. , ARTHUR A. E.
Published: February 2008

The effects of temperature were studied on six root and shoot characters in pea (Pisum sativum) seedlings. The growth response of characters to13, 16 and 19 oC in seven genotypes was linear after 9 days from sowing with growth increasing with increase in temperatures. The response to accumulated heat units of 135 oC at these three temperatures was different with a peak in growth at 16 oC.

A regression analysis of genotype‐environment interactions indicated that JI181, one of the primitive forms, showed the least response to environmental change. A major portion of the genotype‐environment interaction was due to the heterogeneity of the regressions but the non‐linear or residual portion was also significant in many characters. The least variable character over all genotypes was the length of the root which was bearing laterals.
Chemical induction of mating abnormalities and spermatophore production in the Mediterranean flour moth, Ephestia kühniella
Authors: HONG TAN KENG
Published: February 2008

Hexamethyl‐melamine (hemel) when injected into male Ephestia kühniella induced mating aberrations expressed as permanent copulation, sterile mating and spontaneous production of spermatophore. Permanent copulation was not caused by blockage or an elongated spermatophore column but probably caused by failure of the male reproductive organs to completely transfer the spermatophore. Spontaneous spermatophore formation was induced by both cholinesterase inhibitors and nerve stimulants, the effect of the former being more pronounced. It was not caused by stress due to poisoning since DDT even at lethal doses did not induce a response. The results suggest involvement of the nervous system in spermatophore production during a normal mating.
Methods of measuring the prevalence of Phoma exigua on potatoes and in soil
Authors: HIDE G. A. , GRIFFITH R. L. , ADAMS M. J.
Published: February 2008

Methods are described for assessing inoculum of Phoma exigua by directly wounding potato test tubers and by inoculating soil into Arran Banner test tubers or slices.

Large samples of tubers were wounded by dropping onto perforated metal sheet or grading on farm riddles, but standardization was achieved by inflicting four uniform wounds with shaped brass teeth. Tubers were then incubated for 12 wk at 5 oC.

Soil samples to be tested were inoculated into crush wounds on surface‐sterilized test tubers or tuber slices which were incubated for 8 wk at 5 oC. Assessments were speeded by immersing wounded slices in a mixture of Agrimycin and isopropylphenyl carbamate (IPC) solutions before inoculating, and then incubating for 2–3 wk at 10 oC. Although the sensitivity of test tubers is limited by their latent infection, comparisons of the tests in 3–5 years showed that the test tuber methods were frequently more sensitive than direct wounding, especially when amounts of inoculum were small.
The effect of six systemic fungicides on halo spot disease of barley caused by Selenophoma donacis
Authors: BROKENSHIRE T. , COOKE B. M.
Published: February 2008

Six systemic fungicides were applied at growth stage 10 in a spring‐barley field trial, artificially inoculated with Selenophoma donacis at each of three growth stages. Barley cultivars used were Mazurka and Zephyr. The level of disease was significantly reduced by the application of chemicals, benomyl and thiophanate methyl giving the best control. Yield results did not reflect the control of disease although benomyl and thiophanate methyl applications gave slight increases in 1000 grain weight and mean yield per head. Three of the fungicides caused some phytotoxicity in cv. Zephyr and prevented grain formation.
Resistance genes in apple and biotypes of Dysaphis devecta
Authors: ALSTON F. H. , BRIGGS J. B.
Published: February 2008

Apple cultivars and young seedlings were repeatedly inoculated with Dysaphis devecta from six locations in South East England. Four genes governing resistance were associated with three aphid biotypes. The gene for resistance to biotypes 1 and 2 from Cox's Orange Pippin was given the symbol Sd1 while that from Northern Spy, for resistance to biotype 1 only, was designated Sd2. A single gene (Sd3) for resistance to biotype 3 was located in Malus robusta MAL 59/9 and M. zumi MAL 68/5. Worcester Pearmain, Cox, Mcintosh, Lane's Prince Albert and MAL 68/5, are heterozygous for a precursor gene Sdpr without which Sd1Sd2, and Sd3 are ineffective.
The effect of mixtures of rhizobium strains on the dry matter production of white clover grown in agar
Authors: MYTTON L. R. , FELICE J. de
Published: February 2008

The effects of mixtures of rhizobium strains on the dry matter production of S. 100 white clover were investigated by growing plants in tubes of agar with four pure strains known to give contrasts in yield effectiveness, and comparing the results with those produced by plants grown with mixtures of these strains, and with those of uninoculated plants receiving mineral nitrogen. It was found that some components of the mixtures influenced yield much more than others and these strains therefore appeared to be strong competitors. Ability to infect and capacities to fix nitrogen were shown to be mechanisms under separate genetic control; thus competitiveness and effectiveness were not necessarily linked.

Variation within groups of plants inoculated with the same rhizobium strain was generally greater than within the uninoculated control receiving mineral nitrogen. The amount of variation differed from strain to strain and was largest with the intermediately effective one. The plant genotype could modify the relative competitiveness of rhizobium strains and effective association of plant and rhizobium with a high affinity for each other under competitive situations could be built up by coincidental selection of plant and bacterium.
The flow of water into fruit trees. II. Water intake through a cut limb
Authors: BAXTER P. , WEST D.
Published: February 2008

Water was supplied to trees directly through cut limbs in order to bypass the relatively high root resistances to water flow. Addition of the reducing agents 8‐hydroxyquinoline citrate, sodium iso‐ascorbate or ascorbic acid singly or in combination significantly increased the time for which water could be supplied through a cut limb before xylem blockage reduced water inflow. Supply of water to apple trees through a cut limb increased fruit size compared with non‐irrigated control trees.

Application of water by this method also allowed detection of the presence of vascular blockages in trees affected by a root weevil (Leptopius squalidus).
Preferential feeding and damage to cultivars of Nigerian cassava by the variegated grasshopper (Zonocerus variegatus)
Authors: TERRY By E. R. , SCHAEFERS G. A. , GARBER M. J.
Published: February 2008

Large populations of Zonocerus variegatus invaded a cassava crop established during the dry season. The resultant damage was severe, certain cultivars being totally destroyed. The grasshoppers exhibited a statistically significant preference for certain cultivars the defoliation of which shifted attacks to less preferred ones. On a particular variety (Isunikankiyan), populations increased and persisted even after defoliation, probably due to
The development on potatoes of a glasshouse strain of Myzus persicae resistant to organophosphorous insecticides
Authors: DUNN J. A. , KEMPTON D. P. H.
Published: February 2008

When potato tubers infested with a strain of Myzus persicae resistant to organophosphorus insecticides were planted, the tops became heavily colonized despite a furrow‐application of disulfoton granules. The observation showed a more feasible way for resistant aphids of glasshouse origin to establish themselves in the field than by direct migration by alates.
Biochemical characterization of some additional mycelial cultures of basidiomycetes
Authors: TAYLOR J. B.
Published: February 2008

Twenty‐six biochemical tests were used to study cultures of basidiomycetes isolated from roots of fruit‐trees and other plants. The results enabled isolates to be placed into one of sixteen groups. Three of these groups were identified as Collybia drucei, Corticium utriculicum and Heteroporus biennis by matching their biochemical reactions with those of isolates from fruiting bodies of these fungi. This suggests that the other groups might also correspond to species. The three named fungi are indigenous, the first two not having been recorded elsewhere. Thus, root infections by these fungi may have originated from the indigenous fungal flora. Isolates of C. utriculicum and Stereum purpureum which were indistinguishable in culture were also separated using biochemical tests.
Variation in reaction to barley yellow dwarf virus in ryegrass and its inheritance
Authors: WILKINS P. W. , CATHERALL P. L.
Published: February 2008

Genotypes of Italian and perennial ryegrass differed greatly in their reaction to infection with barley yellow dwarf virus (BYDV). One genotype of perennial ryegrass appeared unaffected, whilst the yield and height of other genotypes were reduced. Progeny of the Italian ryegrass genotypes showed a similar degree of variation. Tolerance, assessed by the effect of the virus on yield, was inherited in a wholly additive manner. Symptoms were rare and their severity was under both additive and non‐additive genetic control and strongly correlated with increasing severity of reaction.

The utilization of the variation in BYDV reaction in breeding programmes may prove difficult because plants with the highest performance tended to suffer most from BYDV infection, and half‐sib progeny ranked in a different order of tolerance in the glasshouse from that of their respective parent genotypes in the field. It is suggested that the observed variation in BYDV response results from a readjustment in the balance of genotypically controlled and environmentally conditioned variation in plant growth.
The fungal flora of loganberries in relation to storage and spoilage
Authors: DAVIS R. P. , DENNIS C.
Published: February 2008

Botrytis cinerea, Cladosporium spp., Penicillium spp., Aureobasidium pullulans, Mucor mucedo, Phoma state of Didymella applanata, Cryptococcus laurentii var. laurentii, C. albidus var. albidus, Candida sake and Sporobolo‐myces roseus were consistently present on freshly harvested loganberries. Botrytis cinerea was the main spoilage organism with Mucor mucedo of minor importance. The importance of benomyl‐resistant strains of B. cinerea is discussed.
RNA and protein components of maize streak and cassava latent viruses
Authors: BOCK K. R. , GUTHRIE E. J. , MEREDITH GINA , BARKER H.
Published: February 2008

Polyacrylamide gel electrophoresis indicated that maize streak (MSV) and cassava latent (CLV) viruses each contain one species of protein and two of RNA. The estimated protein mol. wt is 28000 for MSV and 34000 for CLV. The mol. wts obtained for the two RNA species using formamide‐containing gels were the same for the two viruses: 17×108 and 1–3 × 106. It is suggested that the viruses have a two‐part genome and that the tendency of their nucleoprotein particles to form pairs favours the delivery of complete genomes to sites of infection.
Assessment of the potential for and development of organophosphorus resistance in field populations of Myzus persicae
Authors: BAKER J. P.
Published: February 2008

A survey of esterases in field populations of the peach‐potato aphid, Myzus persicae was made during the spring of 1975. Assay was by electrophoresis of single aphid homogenates, and the known association between the activity of an esterase and resistance to organophosphorus insecticide (OP) was used to infer resistance in field populations. The resistant variant replaced the susceptible in populations which had been treated with OP and another variant with threefold (approximately) more esterase activity appeared to be replacing the resistant variant in populations which have been treated twice with OP. The significance of this for control of M. persicae is discussed. Differences in resistance between aphids in different parts of the same field, and the widespread association of these esterase variants in favoured combinations with two electrophoretic variants at another locus have also been investigated.
Temperature sensitive phases during the germination of lettuce (Lactuca sativa) seeds
Authors: GRAY D.
Published: February 2008

Lettuce seeds cvs Hilde, Feltham King and Avoncrisp were subjected, at different phases during imbibition at 22°C, to a high temperature (33°C) inhibitory for germination, for periods ranging from 4 to 144 h, before returning them to 22°C.

The results showed, that the first 4h of imbibition and also the phase between the commencement of mitosis and the onset of radicle emergence were more sensitive to the effects of high temperature than other phases in the germination process. Short exposures (8–24 h) to 33°C commencing at the latter phase delayed germination by up to 4 days, and at the earlier by up to 8 days. Percentage germination was unaffectd except after prolonged exposures (> 48 h) from the beginning of imbibition, which reduced it.

Seedling emergence from moist sieved soil was both delayed and reduced when imbibing seeds were exposed for a short period from the beginning of imbibition to 33°C compared with seeds imbibing continuously at 19°C. Germination was delayed and not reduced when seed was exposed to 33°C at the phase between commencement of mitosis and the onset of radicle emergence.
The genetics of race specific resistance in lettuce (Lactuca sativa) to downy mildew (Bremia lactucae)
Authors: JOHNSON A. G. , CRUTE I. R. , GORDON P. L.
Published: February 2008

Data are presented on the segregation of resistance to five British races and two Dutch races of Bremia lactucae in the F2 progenies of crosses involving seven resistant and several susceptible lettuce cultivars. These data and also those previously published by other workers are considered in relation to the systematic model proposed by Crute & Johnson (1976) to explain the genetics of race specific resistance to B. lactucae in lettuce. It is shown that, with minor modifications, the model accommodates almost all of the previously published data and correctly predicts the new data, except for one set which cannot at present be interpreted.

It is concluded that genetic evidence exists for the presence, among various cultivars of lettuce, of at least four and possibly five different dominant resistance genes of major effect designated Dm2, Dm3, Dm4, Dm6 and Dm8; and of a pair of dominant genes with complementary effect designated Dm7/1 and Dm7/2. The resistance conferred by these genes is specified in relation to five British races, five Dutch, three Israeli and one United States race of the fungus. Resistance genotypes are proposed for cultivars Avoncrisp, Avondefiance, Calmar, Great Lakes 659, Kares, Meikoningen, Mildura, Proeftuins Blackpool, Solito, Valverde, Ventura and the USDA line PI 164937.
Effects of soil applications of benomyl and captan on the growth of onions and the occurrence of endophytic mycorrhizas and rhizosphere microbes
Authors: BERTOLDI M. de , GIOVANNETTI M. , GRISELLI M. , RAMBELLI A.
Published: February 2008

When grown for 6 months in the absence of pathogens, repeated soil applications of benomyl or captan significantly and similarly decreased growth of onion seedlings by 22–25% (diameter) and 31–34% (dry weight). The losses were associated with differing effects on soil microbes. Whereas captan had no effect on the occurrence of vesicular‐arbuscular mycorrhizas it appreciably decreased populations of rhizosphere fungi. In contrast benomyl inhibited mycorrhiza formation but had a relatively small effect on rhizosphere fungi.
A banana fruit spotting disorder in the Yemen Arab Republic
Authors: WALLER J. M. , HINDORF H.
Published: February 2008

A fruit spot of young bananas has recently become prevalent in the Yemen Arab Republic. The spots appear initially on fruit soon after they emerge from the bract, first as small water‐soaked lesions which subsequently become necrotic; the pericarp then splits and the whole fruit rots before maturity. The symptoms are unlike those of previously recorded banana diseases and pathogenic organisms were not consistently associated with the lesions. Possible etiology is discussed.
A technique for the examination of endosperm cells in cereal caryopses
Authors: RADLEY MARGARET
Published: February 2008

A method is described for preparing varnish replicas of cut surfaces of cereal endosperm.
Flight regulation in the green spruce aphid (Elatobium abietinum)
Authors: CARTER C. I. , COLE JANICE
Published: February 2008

In Britain the flight of alate parthenogenetic viviparae of Elatobium abietinum was found to occur only in early summer. Data for this study were extracted from suction trap catches and weather records obtained from meteorological stations adjacent to the traps.

The duration of the flight period increased with latitude. At 51° N 95 % of the trap catch was taken in 24 days and at 55° N in 32 days. A flight threshold temperature of 12–13°C was deduced from trap catches taken within the forest crop. Displacements in median flight days at various sites in Britain could be related to values of accumulated day‐degrees but not to differences in photoperiod. The median flight day can be predicted empirically by accumulating day‐degree values over 8°C from 1 January up to a total of 115 day‐degrees.

The implications of seasonal flight activity on crop reinvasion is discussed.
Effects of earthworms, nematodes, cultivations and host plants on Verticillium wilt of peach and cherry
Authors: NDUBIZU THOMAS O. C.
Published: February 2008

Verticillium dahliae but not V. albo‐atrum Berth was isolated from eight out of twenty‐one stone fruit orchards surveyed for Verticillium wilt disease in western New York. Wilt incidence was related to the cultivation of tomato or legumes as previous or inter‐crop with stone fruit trees. A limited cross species inoculation using isolates of V. albo‐atrum and V. dahliae from woody and herbaceous plants showed that peach and cherry were susceptible to both species. The effect of V. dahliae on growth of cherry seedlings in the presence of Tylenchorynchus claytoni, Pratylenchus penetrans and Meloidogyne hapla was compared. P. penetrans and M. hapla produced more severe growth reduction than T. claytoni. The adverse effect of Verticillium on the growth of cherry seedlings was greater acting together with any one of the three nematodes than acting alone. V. dahliae was shown to be capable of passage through earthworms without loss of infectivity.
Occurrence, purification and properties of narcissus tip necrosis virus
Authors: MOWAT W. P. , ASJES C. J. , BRUNT A. A.
Published: February 2008

Narcissus tip necrosis virus (NTNV), a previously undescribed virus, was detected in the Netherlands and the United Kingdom in plants of twenty‐one cultivars of trumpet, large‐cupped, small‐cupped, double, tazetta and poeticus narcissus. In some cultivars distinct leaf symptoms were sometimes associated with infection but in others infected plants remained symptomless and detection was dependent on serological tests. The virus was readily transmitted by manual inoculation to narcissus, but it failed to infect any of forty‐six other plant species from fourteen families. Up to 50 mg of virus/kg of tissue were obtained by differential centrifugation of narcissus leaf extracts previously clarified with either diethyl ether, n‐butanol or a mixture of n‐butanol and chloroform. The virus particles are isometric, c. 30 nm in diameter, have a sedimentation coefficient (s°20 w) Of 123 S a buoyant density of 1·356 g/cm3, migrate as a single component in polyacrylamide gel electrophoresis, and contain a single RNA species of mol. wt 1·6×106 and two major polypeptides of mol. wt 42000 and 39000. Although NTNV resembles tombusviruses it showed no serological relationship to the type member or six putative members of this group or to thirty‐four other viruses with isometric particles. Its present cryptogram is R/*:1.6/(18):S/S:S/*.
Partial purification and some properties of wineberry latent, a virus obtained from Rubus phoenicolasius
Authors: JONES A. T.
Published: February 2008

Wineberry latent virus (WLV) was obtained from a single symptomless plant of American wineberry (Rubus phoenicolasius) originally imported from the United States of America. On graft inoculation, WLV infected but induced no distinctive symptoms in several Rubus species including those used as indicators for known Rubus viruses. It was not seed‐borne in wineberry.

WLV was mechanically transmitted to several herbaceous species but induced local lesions in only a few; it was weakly systemic in some Chenopodium species. Infective C. quinoa sap lost infectivity after diluting to 10‐4, heating for 10 min at 70°C, and storage either for 8 days at 18°C or for 32 days at 4°C. Sap from infected plants contained flexuous filamentous particles c. 510°12 nm. WLV was partially purified by extracting infected C. quinoa leaves in 0·05 M tris‐HCl buffer (pH 7) containing 0·2% thio‐glycerol and 10% (v/v) chloroform and concentrating virus by precipitation with 7% (w/v) polyethylene glycol (PEG, mol. wt 6000) and 0·1 NaCl. The virus was then pelleted through a 30% (w/v) sucrose pad containing 7% PEG+0·1 M NaCl and finally sedimented through a sucrose density‐gradient. These preparations had A260/280 ratios of 1·26, contained end to end aggregates of WLV particles and formed a partly polydispersed peak in the analytical ultracentrifuge. WLV did not react with antisera to four potex‐viruses, or to apple chlorotic leaf spot or apple stem grooving viruses.
Nematode transmissibility of pseudo‐recombinant isolates of tomato black ring virus
Authors: HARRISON B. D. , MURANT A. F.
Published: February 2008

Pseudo‐recombinant isolates of tomato black ring virus (TBRV), containing RNA‐i of the potato bouquet serotype and RNA‐2 of the beet ring‐spot serotype, were transmitted by the nematode Longidorus elongatus, which also transmits the beet ringspot serotype but not the potato bouquet serotype. Transmissibility by L. elongatus was correlated with antigenic specificity of the virus particles, providing further evidence that nematode transmissibility depends on the structure of the virus coat protein. The distribution of genetic determinants for biological properties between the RNA‐1 and RNA‐2 of TBRV resembles that for raspberry ringspot virus.
Selecting for resistance to downy mildew of sugar beet
Authors: BROWN S. J.
Published: February 2008

Sugar beet seedlings were evaluated for resistance to downy mildew by exposing them to natural infection in a glasshouse maintained at a high relative humidity (c. 95–98%). Exposure to natural infection for at least 3 days was required for adequate infection levels which occurred in the majority of tests; failure in others was related to decreases in relative humidity during clear weather. Seedling disease symptoms were different from those of mature plants. In most instances there was adequate differentiation among seedlings in populations with low, but worthwhile, levels of variation for resistance. The application of the method in selection programmes for resistance is discussed.
Effects of soil density on yield and fertilizer requirement of sugar beet
Authors: JAGGARD K. W.
Published: February 2008

Three experiments (1971–3) on medium‐textured soils of low organic‐matter content examined the effects of soil density on seedling emergence and yield of sugar beet, and the interactions between soil density and the requirement for nitrogen (N) and phosphate (P2O5) fertilizers. Three soil densities were produced by rolling and harrowing, dutch harrowing twice, and power harrowing once; each was tested with 75, 150 and 225 kg ha‐1 N and 0, 100 and 200 kg ha‐1 P2O5.

Most seedlings emerged on the medium‐density treatment produced by dutch harrowing twice. The crop in the least dense soil treatment, produced by power harrowing once, consistently yielded slightly more sugar than the medium‐density treatment, which yielded significantly more than the most dense treatment. In dense soil, created by rolling and harrowing, there was a response to more fertilizer N than the less dense ones; the crop did not respond to phosphate fertilizer. Mechanical impedance, not toxic concentrations of ethylene in the soil atmosphere, appeared to be the cause of reduced yield on the dense soils; these reductions were considerable at dry soil bulk densities in excess of 1·5 g ml‐1.
Yield components and cultivar, sowing date and density in field beans (Viciafaba)
Authors: THOMPSON R. , TAYLOR H.
Published: February 2008

Delay in sowing the cultivars Ostlers (Viciafaba var. equina) and Herz Freya (V.faba var. minor) beyond late February depressed yield. Densities of at least sixty plants per m2 were required to ensure that yield was not limited by sowing rate.

Differences in yield in response to changes in density were reflected particularly in changes in numbers of pod‐bearing nodes per plant, but also to a lesser extent in numbers of pods per pod‐bearing node. The inherently larger seed weight of cv. Ostlers compared with cv. Herz Freya did not confer any yield advantage, differences in number of beans per pod and number of pods per pod‐bearing node tending to equalize the yield of the two cultivars. The most stable component of yield throughout was number of beans per pod, and the least stable was number of pod‐bearing nodes per plant.
Effects of Botrytis fabae infection and mechanical defoliation on seed yield of field beans (Vicia faba)
Authors: GRIFFITHS ELLIS , AMIN SUPAAD M.
Published: February 2008

Effects on seed yield of mechanical defoliation and inoculation with Botrytis fabae were compared using pot‐grown plants of Vicia faba (cv. Maris Beagle). Treatments, which were made at the end of flowering, were applied singly and in all combinations to leaves (a) below, (b) at, and (c) above the flowering nodes (i.e. 23 factorial).

Yield was unaffected by treatments applied to leaves below the flowering nodes. Removal of leaves at flowering nodes did not reduce the number of pods but yield was reduced because there were fewer and smaller seeds. Inoculation of this zone also reduced yield; pods were lost at some nodes but it could also be shown that, irrespective of pod loss, yield at individual nodes was reduced in proportion to the severity of infection on leaves at the same nodes. Removal of leaves above flowering nodes reduced yield almost to the same extent as removal of leaves at flowering nodes but inoculation resulted in only a small amount of infection and yield was not reduced significantly.

These results, taken in conjunction with recent studies on the physiology of the host plant, show that beans are exceptionally vulnerable to attack by B. fabae at the stage of flowering and early pod development. At later stages of development infection is unlikely to have a substantial effect on yield.
The use of garlic (Allium sativum) extracts to control foot rot of Phaseolus vulgaris caused by Fusarium solani f.sp. phaseoli
Authors: RUSSELL P. E. , MUSSA A. E. A.
Published: February 2008

Garlic extract, prepared as a juice from crushed garlic cloves inhibited the in‐vitro growth of Fusarium solani f.sp. phaseoli. Adequate in‐vivo control of foot rot of Phaseolus vulgaris cv. Seafarer was achieved by seed treatment with either the extract from crushed cloves or with an aqueous preparation of commercial lyophilized garlic powder.
Rubus host range, symptomatology and ultrastructural effects of a British isolate of black raspberry necrosis virus
Authors: JONES A. T. , ROBERTS I. M.
Published: February 2008

Scions from red raspberry (Rubus idaeus) plants naturally infected with an aphid‐ and sap‐transmissible virus, code‐named 52V, always induced apical necrosis in R. occidentals signifying the presence of black raspberry necrosis virus (BRNV), whereas plants free from 52V did not. These and other findings provide strong circumstantial evidence that 52V is an isolate of BRNV, the heat‐labile member of the pair of viruses that together cause raspberry veinbanding mosaic disease.

On grafting with R. idaeus scions containing a 52V culture of BRNV free from other detectable viruses, all of twenty‐two red raspberry cultivars and four other Rubus species were infected symptomlessly but apical necrosis developed in R. henryi and R. molaccanus.

Electron microscopy of thin sections of 52V‐infected Chenopodium quinoa, R. henryii and R. occidentalis showed areas of dead cells in the vascular tissue and leaf blade. Some of the cells adjacent to these areas had cell wall outgrowths and many of the plasmodesmata contained virus‐like particles c. 25 nm in diameter arranged in a single file.
Trapping, parasitism, and poisoning of nematodes by fungi
Authors: Godfrey B. E.
Published: February 2008

Naturally occurring toxins and nematode‐destroying fungi are the two major factors controlling soil nematode populations. Nematode‐destroying fungi fall into two groups ‐ hyphal forms, producing traps which capture nematodes, and endoparasitic forms, both common in natural soils. Nematode‐destroying fungi have been used in attempts to control levels of pathogenic nematodes in agricultural soils with limited success.
The dispersion of mononchid nematodes in the soil
Authors: Small R.
Published: February 2008

Previous research on the Mononchidae has centred on the taxonomy and geographical distribution of the group. Observations of cultures of Prionchulus punctatus, maintained in the laboratory, have demonstrated the presence of feeding aggregations. A study of the dispersion of the nematodes within the soil has confirmed that this behavioural pattern also occurs under natural conditions. The results of this study were presented.
Pepper veinal mottle virus associated with a streak diseaseof tomato in Nigeria
Authors: LADIPO J. L. , ROBERTS I. M.
Published: February 2008

A destructive streak disease of tomato (Lycopersicon esculentum) was observed on the University of Ife farm. The disease killed many plants and greatly diminished the quantity and quality of fruit produced by the other plants. A virus that is readily transmitted by mechanical inoculation, by the green peach aphid (Myzus persicae) and by grafting was isolated consistently from diseased plants. The virus was propagated in Nicotiana occidentalis and assayed in Physalis angulata. It was infective after dilution to io‐3 but not io‐4; after iomin at 55 but not 60oC; or after 5 days but not 7 days at 20–26oC. Electron microscope examination of sap from infected N. occidentalis leaves revealed flexuous rods with a modal length of about 780 nm. Based on the host range and symptomatology, particle morphology and size, properties in vitro and serology, the virus is shown to be related to, and possibly indistinguishable from, pepper veinal mottle virus.