bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of different aphid foods on Adalia bipunctata L. and Coccinella 7‐punctata L
Authors: BLACKMAN R. L. 
Published: February 2008

SUMMARYThe influence of different aphid foods on larval development and adult fecundity of Adalia bipunctata L. and Coccinella 7‐punctata L. was investigated. Certain aphids such as Myzus persicae Sulz. and Acyrthosiphon pisum Harris were suitable for both species. Megoura viciae Buckt., was toxic to A. bipunctata but not to C. 7‐punctata. Aphis fabae Scop., although a common natural prey of A. bipunctata, slowed larval development, partly because it was nutritionally unsuitable. Fecundity of adults fed on A. fabae was also reduced to less than half. Larvae and adults of C. 7‐punctata developed and reproduced as well on A. fabae as on other suitable aphids. C. 7‐punctata caught aphids more quickly than A. bipunctata. Larvae of both species given relatively unsuitable prey fed more slowly than normal and consumed less of each aphid. The toxic aphid M. viciae was rejected by A. bipunctata after a short period of feeding.
Detection of infection by Pseudomonas phaseolicola (Burkh.) Dowson in white‐seeded dwarf bean seed stocks
Authors: WHARTON A. L. 
Published: February 2008

SUMMARYSeeds of white‐seeded varieties of dwarf beans infected with Pseudomonas phaseolicola may show fluorescent areas in the testa under ultra‐violet light. Fluorescence is not visible in seed with dark‐coloured testas and is masked by coloured seed dressings. Bacterial infection is not the only cause of fluorescence in testas and the type and colour of the fluorescence cannot be used to diagnose infection. Of 542 fluorescing seeds examined 112 were infected by the pathogen, and only six infected seeds were found in 495 non‐fluorescing seeds from the same samples. It is estimated that in two seed stocks used for these experiments 64 and 68 % of infected seeds were of the fluorescent type.A 34 lb sample of seedstock has to be taken for examination to detect, with 95 % confidence, ten infected seeds in 1 cwt. The selection of all fluorescing seeds from such large samples effectively concentrates the infected seed into a sample small enough to be tested by bacteriological methods.Test seeds are examined bacteriologically by enrichment‐culture in nutrient broth. Ps. phaseolicola is identified in these cultures from the diagnostic symptoms of halo‐blight disease induced in bean seedlings inoculated with aliquots of the cultures.
Studies on the fungitoxicity of captan
Authors: RICHMOND D. V. , SOMERS E. 
Published: February 2008

SUMMARYThe cellular distribution of 35S after incubating labelled captan with Neurospora crassa conidia has been determined. Nearly all the 35S in the spores is bound to the water‐soluble and protein fractions. Thin‐layer chromatography of the hot‐water extract of spores has shown that 35S occurs largely in oxidized glutathione (GSSG) and in a product tentatively identified as a thiazolidine derivative of glutathione. It is suggested that this derivative, which only forms above pH 6·5, is produced by reaction between glutathione (GSH) and the thiocarbonyl chloride liberated on the decomposition of captan.Captan toxicity could not be completely reversed by pretreatment with thiols and disulphides capable of penetrating the cell membrane, confirming the previous hypothesis that fungitoxicity is due to irreversible changes following the oxidation of the protein thiols to disulphides.
Organic manuring for potato scab control and its relation to soil manganese
Authors: ROGERS P. F. 
Published: February 2008

SUMMARYThe suggestion that organic amendment of soil controls scab by reducing insoluble soil manganese to soluble forms toxic to Streptomyces scabies was investigated in pot and field experiments by assessing numbers of manganese‐reducing micro‐organisms in soil.Dried grass meal (2 tons/acre) gave significant control of scab but increases in soluble manganese were insufficient to account for this control. Populations of micro‐organisms in soil increased after adding grass meal but decreased again by the time tubers were initiated and scab infection began. The results suggest that manganese reduction could affect scab if soil contained easily reducible manganese, because dried grass meal increased the numbers of manganese‐reducing micro‐organisms.
Effects of sacbrood virus on adult honey‐bees
Authors: BAILEY L. , FERNANDO E. F. W. 
Published: February 2008

SUMMARYMuch sacbrood virus accumulates in the brains of infected bees, especially of drones, without causing symptoms. However, infected individuals fly earlier in life than healthy bees and most infected foragers fail to collect pollen, as do bees briefly anaesthetized with CO2. The few infected bees that gather pollen contaminate their loads with much sacbrood virus. Infection does not shorten the lives of drones, or of workers that have been deprived of pollen, but it much shortens the prolonged lives of workers that have eaten pollen. Infected workers, healthy workers deprived of pollen, and senile individuals are unable to maintain the usual metabolic rates of bees at temperatures below 35oC, or to resist chilling.
Influence of pea‐root exudates on germination of conidia and chlamydospores of physiologic races of Fusarium oxysporum f. pisi
Authors: WHALLEY W. M. , TAYLOR G. S. 
Published: February 2008

SUMMARYSterile root exudates from wilt susceptible and wilt resistant pea cultivars showed no differential effects on spore germination ofFusarium oxysporumSchl.f.pisi(Linf.) Snyd. & Hans, races 1 and 2 which could be correlated with the pathogenicity of a particular isolate to a given cultivar. Uniformly high percentages of germination were obtained with conidia of the two races in aseptic shake culture with exudates collected from resistant or susceptible plants of various ages. Chlamydospores of the two races incubated with exudates under sterile conditions germinated to uniformly high levels irrespective of exudate origin. Conidia and chlamydospores ofFusarium solani(Mart.) Sacc. f.pisi(Jones) Snyd. & Hans., used for comparative purposes, also germinated to high levels in the presence of exudate solutions of all cultivars.Non‐specific germination of the two races ofF. oxysporumf.pisioccurred in soil when the exudates were supplied to populations of chlamydospores via diffusion units. Germination was lower than that recorded under sterile conditions and was rapidly followed by germling lysis.
The role of weed hosts and the distribution and activity of vector nematodes in the ecology of tobacco rattle virus
Authors: COOPER J. I. , HARRISON B. D. 
Published: February 2008

SUMMARYAt a site in eastern Scotland, nine common species of arable weeds were infected with tobacco rattle virus (TRV), and some of these, notably Viola arvensis and Stellaria media, comprised an overwintering reservoir of the virus. TRV was seed‐borne both in naturally and in experimentally infected V. arvensis (2–10%), and occasionally in other weed species. In the glasshouse at 20 oC a naturally infective population of vector nematodes (Tricho‐dorus spp.) kept in soil free of plants retained its infectivity for 20 wk, although few Trichodorus survived for this period. In the field, the incidence of TRV infection in potato (spraing disease) in plots kept free of weeds for 1–5 years was 3–4 times that in weed‐infested plots but Trichodorus numbers did not differ appreciably between the two treatments. Presumably the virus is retained for long periods in its vectors and these feed on potato more frequently when other hosts are not available. Weeds are probably important in the long term as hosts of both TRV and its vectors, but in the short term weed control seems unlikely to prevent potato spraing because of the long persistence of TRV in vector populations.In the field, Trichodorus accumulated near the interface between topsoil and subsoil, and the incidence of spraing was greatest where the topsoil was shallowest. When cucumber seedlings were exposed to virus‐carrying Trichodorus, TRV reached a greater concentration in roots at 20 oC than at 24 oC, and the virus was not detected in roots at 29 oC. In a sandy soil, TRV was transmitted only when the water content exceeded 15%, and at least 30 % water was needed for maximum transmission. Annual records of rainfall and spraing disease suggest that spraing is most prevalent when the summer is wettest.TRV is not confined to cultivated land. Stabilized sand dunes supporting a pure stand of Ammophila armaria were colonized by Trichodorus pachyder‐mus, but TRV was detected only where the plant community had enlarged to include V. arvensis and other dicotyledons. In such situations, TRV may be introduced in the seed of V. arvensis, and the movement of soil by wind probably contributes to the dispersal of Trichodorus.
Long‐day effects on growth and flower initiation of tomato plants in low light
Authors: HURD R. G. 
Published: February 2008

SUMMARYYoung tomato plants (cv. Minibelle) were grown in plant growth cabinets in 575 kJ m‐2 (400–700 nm) daily radiation. Plants grown in an 8 h day were then compared with those in which 10% of the radiation was taken from the main 8 h light period and supplied over the next 8 h period. After 41 days from sowing the 16 h day plants had almost twice the dry weight of those in short days and a 55 % greater leaf area. Net assimilation rate, relative growth rate and relative leaf area growth rates were all greater in long days, although the differences in growth diminished with time. The long‐day treatment also increased the proportion of dry weight in the leaves, a function which is usually relatively stable in different environments.The beneficial effect of the long days may arise from a reduction in night respiration, or an increase in rate of photosynthesis through the observed increase in chlorophyll content.The 8 h light period resulted in flower initiation one or two nodes lower than the 16 h period so that the cultivar is a quantitative short‐day plant.
Cowpea mild mottle, a newly recognized virus infecting cowpeas (Vigna unguiculata) in Ghana
Authors: BRUNT A. A. , Kenten R. H. 
Published: February 2008

SUMMARYCowpea mild mottle virus (CMMV), a previously undescribed virus widespread in cowpeas (Vigna unguiculata) in the Eastern Region of Ghana, was seed‐borne in V. unguiculata, Phaseolus vulgaris and Glycine max, but was not transmitted by twelve aphid species including Aphis craccivora, A. fabae, Acyrthosiphon pisum and Myzus persicae. CMMV was transmitted by inoculation of sap to eleven of seventeen members of the Papilionaceae causing very severe diseases in G. max and Arachis hypogaea, and to ten of fifty‐one species within five of nineteen other families; it was best propagated in G. max and Nicotiana clevelandii, and assayed in Chenopodium quinoa. Sap from systemically infected G. max was infective after dilution to 10‐3 but not 10‐4, after 10 min at 65 °C but not at 70 °C, or after 4 days at 18 °C or 16 days at 2 °C. Lyophilized sap was infective after 3 years in vacuo.CMMV has straight to slightly flexuous, fragile filamentous particles, c. 13 × 650 nm which, in sap, are occasionally surrounded by a loose external spiral. About 5 mg of purified virus was obtained from 1 kg of leaf tissue of G. max or N. clevelandii by clarifying leaf extracts in 0.02 m borate buffer (pH 9.5) with chloroform, followed by two or three cycles of differential centrifugation, and density gradient centrifugation. Virus preparations had ultraviolet absorption spectra typical of a nucleoprotein containing c. 5 % nucleic acid, contained numerous particles without external spirals, which sedimented as a single component with a sedimentation coefficient (s°20, w) of 165 × 4S, and contained a single polypeptide species with a molecular weight of 32000–33000. CMMV showed a distant serological relationship to carnation latent virus, but not to ten other morphologically similar viruses; it thus seems to be a distinct member of the carlavirus group, and has the cryptogram: */*:*/(5):E/E:S/*.
The sowing of germinating vegetable seeds using a fluid drill
Authors: CURRAH I. E. , GRAY D. , THOMAS T. H. 
Published: February 2008

SUMMARYCarrot seeds which had been imbibed or germinated and were then sown in a gel extruded through standard coulters emerged five days earlier than dry seeds sown with a conventional drill and gave higher yields after 64 days although not after 77 days. There was no difference in mean time to emergence or in final plant stand between lettuces grown from dry seeds and those from seeds imbibed for 24 h and sown in a gel, but the duration of the emergence period of the latter was halved in one of the two experiments. Celery seeds, the light requirements of which had been satisfied during germination in optimum conditions in the laboratory before they were sown in the field in a gel, gave a 60% plant stand as compared with a stand of 2% from dry seeds.
Studies on the sensitivity of monogerm sugar beet germination to water
Authors: PERRY D. A. , HARRISON J. G. 
Published: February 2008

SUMMARYExcessive water in the substratum inhibited germination of monogerm sugar beet seed but it was not lethal, and other crop seeds tested were not as sensitive as beet. The inhibition was not evident in a pure oxygen atmosphere and was lessened when the fruit cap was removed. Although bacterial populations on fruits absorbed appreciable quantities of oxygen, differences between populations in optimum and excessive water were insufficient to account for the inhibition.Anatomical observations revealed the presence of a pore through the sclerified fruit wall at the point of attachment to the mother plant. Evidence indicated that the pore was the route for oxygen and water uptake to the seed, and theoretical calculations of gas flux suggested that oxygen supply would be insufficient to sustain germination when the pore was filled with water.
A strategy for evaluating the safety of organisms for biological weed control
Authors: WAPSHERE A. J. 
Published: February 2008

SUMMARYA strategy for establishing the specificity and safety of an organism as a biological weed control agent is described. A critical first step is to expose to its attack a small group of plants very closely related and exhibiting morphological and biochemical similarities to the weed. To prevent an erroneous negative result tests are also made on selected cultivated plants, including those closely related to the weed, those of which the associated insects and fungi are little known, those that have evolved apart from or been little exposed to the agent, those attacked by closely related organisms and those already recorded as hosts.The circumstances under which the strategy might fail to indicate safety are discussed, i.e. polyphagous organisms attacking plants irregularly distributed throughout many families, organisms highly specific to two alternate hosts, and those attacking two or three phylogenetically widely separated plant groups. The additional crop plant testing, included in the overall strategy to deal with such possible failures, is discussed.It is shown that the strategy would have included Sesamum tndicum in the list of plants challenged by the bug Teleonemia scrupulosa in biological testing for control of Lantana camara, thereby forewarning of the attack that was subsequently observed in Africa.
Evaluation of wheat cultivars for ability to retard development of stem rust
Authors: WILCOXSON ROY D. , SKOVMAND B. , ATIF A. H. 
Published: February 2008

SUMMARYThe ability of wheat cultivars (Triticum aestivum) to retard the development of stem rust, Puccinia graminis f.sp. tritici, was evaluated in hill plots for 3 yr at several locations in Minnesota, against single races and mixtures of races. The area under the disease progress curve was a convenient and reliable method for data summation, but the rate of disease development was not. When inoculated with single races (15B2, 32, 113 or 31) or with mixtures of races (11, 15, 15B2, 17, 32, 151), the cvs Exchange, Thatcher, McMurachy, Redman, Kenya 58, Frontana and Idaed retarded stem rust development more than Baart, Prelude and Marquis; Lee was intermediate. The methods and techniques reported should permit selection of cultivars capable of retarding the development of stem rust.
Host relations and distribution of a physiological and pathological variant of Pseudomonas morsprunorum
Authors: FREIGOUN S. O. , CROSSE J. E. 
Published: February 2008

SUMMARYIn a plot of sweet‐cherry trees (Primus avium), leaf spot infections caused by Pseudomonas morsprunorum were more abundant on the cv. Roundel than on the normally more susceptible cv. Napoleon. Roundel also supported significantly higher leaf surface populations of the pathogen. This reversal in the relative field susceptibility of the two cultivars was associated with the presence on the trees of a variant form of P. morsprunorum that differed from typical strains in colony structure, gelatinase activity and pathological characters. The variant strains were less infective through leaf scars but more invasive in bark parenchyma than typical strains, and in branch and leaf inoculations, they showed specialization for the cv. Roundel. This specialization was reflected in the distribution of variant and typical strains on Roundel and Napoleon trees in other localities. The significance of the variant in relation to disease epidemiology and cultivar resistance is discussed. The variant is designated race 2 to distinguish it from the typical, or race 1 cherry strains of P. morsprunorum.
Sugar concentration in sugar beet: varietal differences and the effects of soil type and planting density on the size of the root cells
Authors: MILFORD G. F. J. 
Published: February 2008

SUMMARYDifferences in beet weight and sugar concentration of four commercial varieties grown on two types of soil and at different planting density were related to changes in the numbers, sizes and sugar storage capacities of the storage root cells.Much of the variation in beet weight between varieties and soil type was attributable to differences in cell size, less to differences in their number. Differences in weight of beet grown at different densities were caused equally by changes in number of cells and their size. Variation in sugar concentration of the beet was, in all cases, determined more by differences in cell size than in their capacity tostore sugar, but the two factors were not wholly independent of each other.
Germination of Puccinia striiformis uredospores on leaves of adult winter wheat plants
Authors: RUSSELL G. E. 
Published: February 2008

SUMMARYIn experiments with intact adult winter wheat plants and detached leaves, higher percentages of Puccinia striiformis uredospores germinated on the adaxial leaf surface, particularly the distal parts, than on the abaxial surface. This is consistent with the observation that the distal parts of the adaxial leaf surface are those which are most susceptible to yellow rust.Higher percentages of uredospores germinated on leaves of some of the winter wheat varieties examined than on those of others. These varietal differences depended on the part of leaf and the race of P. Striiformis used for the comparisons. This suggests that the differences between varieties are partly race specific.
The geographical distribution of Xiphinema and Longidorus nematodes in the British Isles and Ireland
Authors: TAYLOR C. E. , BROWN D. J. F. 
Published: February 2008

SUMMARYThe distribution of Xiphinema and Longidorus species in the British Isles and Ireland were mapped by means of a computer programme from 5527 records. Longidorus caespiticola, L. elongatus, L. goodeyi and L. leptocephalus were found to be widespread among a wide range of vegetation types, particularly in grassland and arable crops; L. macrosoma and L. profundorum were recorded frequently in southern and central England, and L. attenuatus in East Anglia; L. vineacola was recorded once only in Eire. Paralongidorus maximus was recorded from two localities in eastern Scotland and one in southern England, on each occasion from intensively cultivated ground. Four species of Xiphinema were recorded but only X. diversicaudatum is widespread although apparently with a northerly limit in central Scotland; X. diversicaudatum was equally prevalent in arable crops, grassland and deciduous woodland; X. coxi and X. vuittenezi were recorded from a few scattered localities in England, and the few records for X. mediterraneum were all from Kent, south east England. All species were found in a wide range of soil types but mostly in light soils with a large sand fraction. Many of the species occurred together in mixed populations; L. caespiticola was most frequently associated with X. diversicaudatum and with L. leptocephalus and L. elongatus. X. diversicaudatum also was commonly found with L. goodeyi. Viruses were transmitted in laboratory bait tests in only eighteen of 325 soil samples containing X. diversicaudatum and four of 265 containing L. elongatus.
Effects of virus genotype and temperature on seed transmission of nepoviruses
Authors: HANADA K. , HARRISON B. D. 
Published: February 2008

SUMMARYTransmission of different nepoviruses through chickweed (Stellaria media) seed was differently affected by ambient temperature during seed production. Raspberry ringspot and tomato black ring (Scottish isolate) viruses were similarly and frequently transmitted at14, 18 and 22 oC, whereas arabis mosaic virus was transmitted most frequently at 14 oC, and strawberry latent ringspot and tomato black ring (German isolate) viruses at 22 oC. When infected by seed‐borne nepoviruses, seedlings of S. media and other species were symptomless at 15–25 oC, and the viruses were therefore detected by inoculating sap to Chenopodium quinoa indicator plants. However, typical symptoms of arabis mosaic and tomato black ring viruses were induced by growing Nicotiana tabacum, N. clevelandii and C. quinoa seedlings infected with seed‐borne virus at 33–37 oC during the third and fourth weeks after sowing, preceded and followed by periods at 15–25 oC. The proportion of N. tabacum seedlings developing symptoms was the same as that of untreated seedlings yielding sap‐transmissible virus.Seed transmissibility of pseudo‐recombinant isolates of raspberry ringspot and tomato black ring viruses, containing RNA‐i from one virus strain and RNA‐2 from another strain, depended greatly on the transmissibility of the strain contributing RNA‐i. The source of RNA‐2 had an additional but smaller influence. The satellite RNA (RNA‐3) of tomato black ring virus was seed‐transmitted in S. media and its occurrence in cultures did not affect the frequency of transmission of the virus. Results of testing the infectivity of extracts of seed from infected mother plants suggested that failure of seed transmission reflected failure to become established in the seed, not subsequent inactivation.Whereas seed transmissibility of raspberry ringspot virus is primarily dependent on information carried in RNA‐i, transmissibility by nematode vectors, another property of major ecological importance, is determined by RNA‐2. In the field, selection pressures presumably can act independently on the two parts of the genome but evidence was also obtained of selection for mutual compatibility of RNA‐i and RNA‐2.