bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acclimatisation in the green spruce aphid, Elatobium abietinum
Authors: PARRY W. H. 
Published: February 2008

SUMMARYThin layer chromatography separation of 80% ethanol extracts of adult Elatobium abietinum revealed the presence of the polyhydric alcohol mannitol in aphids overwintering outdoors but not in aphids kept permanently indoors at 15°C. After 3 days at 15°C no traces of mannitol were left in overwintering aphids. Mean freezing temperatures of outdoor, unfed instar I nymphs were about 4°C lower than those of unfed instar I nymphs produced at 15°C. Mean freezing temperatures of overwintering adults were considerably higher than those of unfed instar I nymphs and showed no changes associated with time at 15°C following transference indoors. Similarly, mean freezing temperatures of Sitka spruce needles transferred to 15°C did not change. It was concluded that, although freezing was mainly avoided by supercooling, the presence of mannitol lowered the true freezing temperature of aphid haemolymph and, consequently, the actual freezing temperatures of nymphs produced under cold conditions. However, the considerable increase in freezing point temperatures caused by imbibition of plant sap masked these acclimatisation changes in feeding aphids.
A yellow mosaic disease of horse chestnut (Aesculus spp.) caused by apple mosaic virus
Authors: SWEET J. B. , BARBARA D. J. 
Published: February 2008

SUMMARYA severe foliar yellow mosaic disease was observed in horse chestnut trees (Aesculus carnea and A. hippocastanum). Reactions in woody indicator plants grafted with diseased horse chestnut suggested the presence of an ilarvirus. Virus isolates obtained by mechanical inoculation of herbaceous test plants reacted with antisera to apple mosaic virus but not with antisera to its serotype prunus necrotic ringspot virus, or to prune dwarf virus. Yellow mosaic was induced in horse chestnut seedlings grafted with tissues from herbaceous hosts infected with horse chestnut isolates or with the European plum line pattern isolate of apple mosaic virus. Virus was detected by enzyme‐linked immunosorbent assay (ELISA) in embryo and endosperm of immature seed from infected trees but not in mature seed, or progeny seedlings.Strawberry latent ringspot virus was detected in one of six A. hippocastanum trees with a leaf vein yellows disease.
Effects of Pratylenchus penetrans on development of strawberry wilt caused by Verticillium dahliae
Authors: MCKINLEY R. T. , TALBOYS P. W. 
Published: February 2008

SUMMARYThe nematode Pratylenchus penetrans or the closely related P. fallax occurred in three out of four strawberry plantations infested with Verticillium dahliae surveyed in Kent. When plants of cv. Cambridge Vigour were inoculated with P. penetrans and V. dahliae together in field ‘micro‐plots’ the nematode increased the rate of wilt development except when the concentration of V. dahliae microsclerotia in the soil was very low. In a pot experiment, under conditions not conducive to symptom expression, the incidence of infection was increased by nematodes in Cambridge Favourite, Cambridge Vigour and Redgauntlet; the incidence was least in Red‐gauntlet, the most resistant cultivar. The nematode appeared to cause local changes in the root cortex which aided hyphal penetration of the adjacent tissues.Growth of strawberry plants in the absence of V. dahliae was not significantly affected even by large populations of the nematode, but growth was reduced by V. dahliae at all rates of inoculation in the field.Infection by Verticillium did not affect the total numbers of nematode per plant at the end of the experiments, although the number per g fresh weight was greater on the small amount of white root on severely diseased plants than on the larger amount on healthy or mildly diseased plants.
Resistance of cocoa to vascular‐streak dieback disease
Authors: PRIOR C. 
Published: February 2008

SUMMARYWater‐soluble exudates from young cocoa leaves markedly inhibited germination of spores of Oncobasidium theobromae in vitro, but there was no correlation between the inhibitory activity of a clone and its field resistance to vascular‐streak dieback. Germinating spores penetrated young leaves and the path of penetration was marked by the browning of adjacent epidermal and mesophyll cells. At the appearance of the earliest leaf symptoms the infections in the stem were confined to the vascular traces of that leaf, but spread subsequently into the secondary xylem. Clones varied in their ability to produce tyloses in response to wounding or infection and a ranking of 10 clones on tylose frequency correlated significantly with the ranking based on field resistance, but the variability was too great for this to be useful in resistance prediction. There was no significant difference in vessel size between resistant and susceptible clones. A highly significant correlation existed between vessel and branch cross‐sectional areas in six clones.
Additional phytoalexin‐like compounds in Ht‐gene resistance of corn to Helminthosporium turcicum
Authors: OBI I. U. 
Published: February 2008

SUMMARYFour additional compounds inhibitory to germination of Helminthosporium turcicum spores were isolated from lesion‐extracts of field‐grown Ht‐gene corn (Zea mays) lines which were inoculated with H. turcicum. The compounds were named phytoalexins A3, A4‐I, A4‐II and A5. A3, A4‐1 and A4‐1 showed over 99% inhibition of H. turcicum spores at 1 mg/ml of 10% ethanol and LD50 of about 600 μg/ml. A5 showed an LD50 of about 800 μg/ml of 10% ethanol. The ultraviolet, infrared, nuclear magnetic resonance, electron impact mass spectra and field desorption mass spectra showed that these compounds might be related to the previously described phytoalexins A1 and A2. They seem to have the following functional groups: aromatic ring, hydroxyl and/or phenolic groups, carbonyl groups, probably a carboxylic acid or ester type and a long aliphatic side chain.
Factors affecting the preclimacteric period of banana fruit bunches
Authors: MARRIOTT J. , NEW S. , DIXON E. A. , MARTIN K. J. 
Published: February 2008

SUMMARYPreclimacteric periods of banana fruits stored at 13.5d̀C were measured for bunches of several triploid cultivars including cv. Valery and a group of tetraploid clones; in the main experiment, measurements were made for about 450 bunches of 29 clones harvested mainly at weekly intervals over a period of 1 yr. A model was developed to partition the effects on preclimacteric period of the continous variables, bunch age and fruit girth at harvest and of clone difference, different agronomic treatments and harvesting dates. Preclimacteric period was well correlated with both bunch age and fruit girth, the relationship with either variable being approximately linear over the last 6 wk of bunch development. Very highly significant difference in preclimacteric period were observed between clones, difference between tetraploid clone being related in part to their diploid parentage. A small but highly significant increase in preclimacteric period was observed for bunch where the navel was removed early in bunch development compared to untreated bunch. very highly significant difference occurred between different harvesting dates but changes from the mean preclimacteric period occured mainly for bunches developing during periods when ambient temperature and bunch development rate changed rapidly and not for those developing during the warmest or coolest conditions.
The effect of cereal growth stages on the reproductive activity of Sitobion avenue and Metopolophium dirhodum
Authors: WATT A. D. 
Published: February 2008

SUMMARYApterous Sitobion avenae on oats were found to have a higher reproductive rate on the ears (5–95 nymphs per day) than on young leaves (3–78 nymphs per day), mature leaves (2–17 nymphs per day) or senescent leaves (2–08 nymphs per day). At each growth stage of the the host plant large aphids gave birth to more young than small aphids, but aphids of the same weight on different growth stages of the host plant had different reproductive rates. On wheat in the field S. avenae gave birth to more young on the ears but less on the leaves than Metopolophium dirhodum on the leaves.The suitability of ears to S. avenae changed through the flowering and ripening stages. During the latter part of the milky‐ripe stage the reproductive rate of S. avenae declined and its mortality increased. The consequences of the variations in reproduction and mortality are discussed in relation to the life history and population dynamics of S. avenae and the assessment of cereal varieties for aphid resistance.
Effects of temperature on development of Otiorrhynchus sulcatus (Coleoptera: Curculionidae)
Authors: STENSETH CHRISTIAN 
Published: February 2008

SUMMARYDevelopment of the black vine weevil, Otiorrhynchus sulcatus, was investigated at constant temperatures from 9 to 27 oC. Pre‐adult development was completed in 200 and 130 days at 15 and 24 oC, respectively. Eggs and larvae developed at 27 oC, but no pupation took place at this temperature. The developmental threshold temperatures for eggs, larvae + pre‐pupae and pupae were 6, 2–6 and 12 oC, respectively. Reproductive maturation of females took place at temperatures from 12 to 27 oC, but only a few females became reproductive at 12 oC. Most females at 12 oC, like those at 9 oC, had a short maturation feed, but the ovaries did not develop. The pre‐oviposition period was temperature dependent. The females showed a cyclic oviposition pattern with three peaks. The significance of soil temperatures for the phenology and distribution of O. sulcatus in Norway is discussed.
The competitive ability and symbiotic effectiveness of doubly labelled antibiotic resistant mutants of Rhizobium trifolii
Authors: BROMFIELD E. S. P. , JONES D. GARETH 
Published: February 2008

SUMMARYDoubly labelled mutants of Rhizobium trifolii, resistant to streptomycin and spectinomycin, were studied in respect of nodulating competitiveness and symbiotic effectiveness relative to the ‘wild‐type’ parent strains using Trifolium repens cv. S184 as the host plant.A combination of antibiotic resistance, differential absorption of congo‐red and the fluorescent antibody technique permitted the rapid differentiation of all Rhizobium strains used, either from mixed inocula or from nodules. The doubly labelled antibiotic resistant mutants were inferior in terms of competitive ability for nodulation with an ineffective strain compared with the ‘wild‐type’ parent strains. A rapid method for evaluating effective antibiotic resistant strains for nodulating competitiveness is suggested. All the mutants examined were also found to be less symbiotically effective than the respective ‘wild‐type’ strains although these differences generally did not reach statistical significance. The reduced symbiotic effectiveness of the antibiotic resistant mutants was associated with an increase in magnitude of the variances for shoot dry weights, relative to that shown by the parent strains. A possible explanation for this phenomenon is presented.
Yield losses in barley, wheat and potatoes associated with field populations of'large form‘ Longidorus leptocephalus
Authors: SYKES G. B. 
Published: February 2008

SUMMARYThree field experiments made during 1975‐77, in North and South Yorkshire, investigated the influence of ‘large form’Longidorus leptocephalus upon the yield of spring barley, winter wheat and second early potatoes. Longidorus populations ranged from undetectable levels to 2375/litre soil. At one site estimates of nematode numbers were made twice, and gave a close agreement between the ranking order of plots. Significant negative correlations between numbers of L. leptocephalus and yield suggested that this nematode impaired the yield of these crops. For each 200 LongidoruslX of soil the estimated reductions in yield were 0–25 t/ha of barley, 0–13 t/ha of wheat and 0–55 t/ha of potatoes.
Effects of Fusarium nivale and F. culmorum on the establishment of four species of pasture grass
Authors: HOLMES S. J.I. 
Published: February 2008

SUMMARYCocksfoot cv. Aberystwyth S 26 and timothy cv. Scots were found to be significantly more susceptible to pre‐emergence death caused by Fusarium nivale and F. culmorum than were either perennial ryegrass cv. Gremie, or Italian ryegrass cv. RvP. The extent to which each grass was affected by Fusarium at the pre‐emergence stage was markedly influenced by both the air temperature and the level of inoculum present in the soil at the time the seeds were sown. Under all conditions, however, cocksfoot and timothy suffered greater reductions in emergence when sown in soil containing either species of Fusarium than did the ryegrasses.Evidence is presented which suggests that the extreme susceptibility of cocksfoot and timothy to pre‐emergence damage is related to the slow germination of the former and the small seed size of the latter.In addition to their direct effects on seedling numbers both fungi reduced the vigour of those seedlings which did emerge, cocksfoot and timothy being particularly badly affected.
Shifts in host plant resistance to the cabbage aphid (Brevicoryne brassicae) exhibited by Brussels sprout plants
Authors: DODD G. D. , van EMDRN H. F. 
Published: February 2008

SUMMARYSeven cultivars of Brussels sprouts from different sources were tested for their relative degrees of resistance to the cabbage aphid (Brevicoryne brassicae) by estimating the Potential Increase Rate of aphid infestations. The cultivars Winter Harvest and Early Half Tall were selected as susceptible and resistant respectively and tested further. Glasshouse experiments indicated that the resistance of Winter Harvest to the aphids increased with age.These relative levels of resistance were confirmed by population counts in the field. Aphid numbers were initially significantly higher on Winter Harvest than on Early Half Tall although significance was lost as the season progressed at a time when the characteristics responsible for the resistance mechanism ceased to be distinguishable between the two cultivars.Analysis of the amino acid content of leaf tissues collected at monthly intervals through the aphid season enabled ‘risk rating’ predictions of aphid resistance to be made. These conformed with the shifts towards greater resistance as the plants aged noted in the glasshouse trials and endorsed the part played by amino acids in the mechanism of resistance. Total amino acid concentrations reached a peak during September and October then declined with generally lower levels of amino acids in Early Half Tall than Winter Harvest. This cultivar also possessed a greater concentration of those amino acids known to be favourable to B. brassicae although the difference between the two had diminished considerably by the end of September.Analyses of the mustard oil glycoside levels in mature glasshouse‐grown plants did not indicate a difference between the cultivars.
The life‐history of the eriophyid mite Aculus schlechtendali on apple in South‐east England
Authors: EASTERBROOK M. A. 
Published: February 2008

SUMMARYDuring 1975–77 the life‐history of Aculus schlechtendali was studied in apple orchards. The morphology of the mite and its development at a range of temperatures were studied in the laboratory.Deutogynes of A. schlechtendali hibernated mainly in small permanently dormant buds and under loose bark on spurs and around buds on 1‐yr shoots, and moved into fruit buds between the bud burst and pink but stages and into vegetative buds as the buds began to swell. Populations on leaves reached a peak in August and mite feeding at high density caused browning of the under surfaces. The return to hibernation sites began in July.The developmental stages of the mite are described. A generation took c. 39, 16 and 10 days at 10, 16 and 22 d̀C, respectively. Protogynes laid totals of 67–102 eggs at a rate of 1.7, 2.4 and 2.8 eggs/day at 10, 16 and 22 d̀C: deutogynes laid 21–47 eggs after hibernation at a rate of 1.3 and 1.6 eggs/day at 10 and 16 d̀C. The species was found only on cultivars and species in the genera Malus and Pyrus.
Fungi on red raspberry from lesions associated with feeding wounds of cane midge (Resseliella theobaldi)
Authors: WILLIAMSON B. , HARGREAVES A. J. 
Published: February 2008

SUMMARYTwo types of vascular lesion are described from the base of canes in plantations infested by raspberry cane midge (Resseliella theobaldi); (1) brown lobate lesions (‘patches’) confined to midge feeding areas, (2) brown lesions spreading proximally and distally from the point of infection (‘stripes’). Either or both types of lesion may be presented in individual canes. Isolations from (1) produced principally Fusarium avenaceum; isolations from tissues where (1) and (2) are contiguous gave Leptosphaeria coniothyrium and F. avenaceum; isolations from (2) arising from old cane stub wounds in the absence of midge gave L. coniothyrium.The important secondary role of fungi in the midge blight complex is confirmed, but the involvement of L. coniothyrium in the complex is unclear because it also infects stub wounds on midge‐infested canes.
The role of pigmentation in survival of the leaf spot fungus Cercospora beticola
Authors: LYNCH F. J. , GEOGHEGAN M. J. 
Published: February 2008

SUMMARYBoth germination and survival time of spores of a pigmented strain of Cercospora beticola were directly correlated with relative humidity. Pigmented cultures, under conditions of low water availability (15%) survived 242 days' continuous exposure to light (110 lx). The ability of various strains of the fungus to survive in soil was found to be influenced by pigmentation, rate of growth, inoculum ratio in the soil and the physiological state of the organism before exposure to the soil environment.
Annual ryegrass toxicity: parasitism of Lolium rigidum by a seedgall forming nematode (Anguina sp.)*
Authors: PRICE P. C. , FISHER J. M. , KERR A. 
Published: February 2008

SUMMARYInfection of annual ryegrass (Lolium rigidum) by Anguina sp. resulted in replacement of seeds by bottle‐shaped galls, each containing several hundred quiescent, second‐stage larvae. The biology of the nematodes, including the emergence of larvae from galls, survival in soil, and movement into and development within the host plant, has been examined. Larvae were not able to leave the galls during the dry summer, but emerged within soil 2–6 wk after normal autumn rains and following partial decay of the gall rind. Emergence took place over several months, and not all larvae emerged in any one year; they were able to survive over summer in soil both within and outside the galls.Under suitable moisture conditions, host plants were infested by larvae which climbed up the outer surfaces, became lodged within leaf sheaths, and then gradually moved towards the centre of the plant. Larvae which reached the central or axillary meristems prior to flowering were carried up with the elongating inflorescence, and attacked developing floret primordia. The nematodes developed rapidly to the adult stage, and eggs were being laid within galls by the time the inflorescence had emerged. Second‐stage larvae hatched quickly and were the only live stage remaining after the ryegrass had died.
The effects of flower removal on the seed yield of pigeonpeas (Cajanus cajan)
Authors: SHELDRAKE A. R. , NARAYANAN A. , VENKATARATNAM N. 
Published: February 2008

SUMMARYIn field experiments carried out at Hyderabad, India with early and mediumduration cultivars of Cajanus cajan sown at the normal time, in July, removal of all flowers and young pods for up to 5 wk had little or no effect on final yield. The flowering period of the deflowered plants was extended and their senescence delayed. The plants compensated for the loss of earlier‐formed flowers by setting pods from later‐formed flowers; there was relatively little effect of the deflowering treatments on the number of seeds per pod or weight per seed. The plants were also able to compensate for the repeated removal of all flowers and young pods from alternate nodes by setting more pods at the other nodes.The removal of flowers from pigeonpeas grown as a winter crop resulted in yield reductions roughly proportional to the length of the deflowering period, probably because maturation of these plants was delayed and occurred under increasingly unfavourable conditions as the weather became hotter.
Relationships between photosynthetic area and other growth attributes with grain yield in 6‐ and 2‐row barley genotypes
Authors: WILLIAMS R. H. , HAYES J. D. 
Published: February 2008

SUMMARYSix‐row and 2‐row barley genotypes were grown as individually spaced plants in the field, and estimates of area of green tissue and other characters were obtained at ear emergence and maturity. Positive correlations (P<0.01) were found within both 6‐ and 2‐row types between grain dry wt per main culm and grain number, mean date of ear emergence, area of green tissue above the flag‐leaf node, and dry wt of the third leaf below the ear (F‐2 leaf). This supports the hypothesis that the magnitude of assimilate supply prior to anthesis is a very important determinant of grain yield in barley, and the possible use of the F‐2 leaf as a criterion for selection of genotypes with a large photosynthetic capacity and grain yield is discussed.
The influence of plant age on resistance of radish to cabbage root fly egg‐laying
Authors: ELLIS P. R. , HARDMAN J. A. , CRISP P. , JOHNSON A. G. 
Published: February 2008

SUMMARYCabbage root fly (Delia brassicae) egg‐laying around radish plants ranging in age from newly emerged seedlings to plants with flowering shoots was studied in the field and laboratory. The attractiveness of radish changed with age, one peak in egg‐laying occurring just before plants were of marketable size and further peaks as they produced flowering shoots. The pattern of egg‐laying was similar for the six radish cultivars tested, both in the field and laboratory, irrespective of whether flies did or did not have a choice of plants of different ages. At any one age, there was no correlation between egg‐laying and plant size. Selection within radish cultivars for the extremes of the range of egg‐laying preference appeared to alter the cycle of attractiveness of different radish stocks to cabbage root fly, the response being influenced by environmental conditions.
Studies on the survival and transmission of Xanthomonas manihotis on cassava seed
Authors: PERSLEY G. J. 
Published: February 2008

SUMMARYCassava seed which had been stored at 5 oC and 60% r.h. for 2–51 months was assayed for the presence of Xanthomonas manihotis by a leaf‐infiltration technique, using as inoculum the supernatant from seeds soaked in sterile water at 30 oC for 2–4 h. The threshold of sensitivity of the assay method was 105 cells/ml. Twenty out of 50 samples yielded the pathogen. The infested seed had been in storage for 2–18 months. Bacteria reisolated from infiltrated leaves were identical to X. manihotis in cultural characteristics, phage type and pathogenicity. Surface sterilisation or hot air treatment for 24 h at 65oC or lower did not eliminate the pathogen from infested seed. Soaking of infested seed in hot water at 60 oC for 20 min reduced the number of bacteria to less than the minimum detectable level without appreciably reducing germination. Cassava bacterial blight was observed in 8‐wk‐old seedlings which had been planted during the dry season at a site where infection from outside sources was unlikely. It is postulated that a low percentage of successful seed transmissions of X. manihotis can occur under favourable environmental conditions.