bluuebunny/crossref_metadata_2025_split huggingface dataset:
East African strains of cowpea aphid‐borne mosaic virus
Authors: BOCK K. R. 
Published: February 2008

SUMMARYCowpea aphid‐borne mosaic virus (CAMV) was isolated for the first time in East Africa where three distinct strains, type, veinbanding and mild, were differentiated by host range and serology. The three strains infected 17/38, 18/37 and 10/35 legume species, and 11/21, 7/21 and 3/19 non‐legume species, respectively.The viruses were propagated in cowpea and assayed in Chenopodium amaranticolor. Isolates of all three strains had similar in vitro properties: dilution end point between 10‐3 and 10‐4; thermal inactivation point between 56 and 58 °C; longevity in vitro between 2 and 3 days. Infectivity of sap from frozen leaves was high after 4 wk but much less after 7 wk; infectivity was largely precipitated by 50% acetone but inactivated by 50% ethanol. High yields of virus were consistently obtained from cowpea by extracting systemically infected leaves in 0.5 m sodium citrate containing 1% mercaptoethanol (pH 8.1), and clarifying with 8.5 ml n‐butanol/100 ml sap. Virus preparations contained numerous unaggregated and aggregated virus particles c. 750 nm long and contained components with sedimentation coefficients (s°20, w) of 150S and 175S (presumably unaggregated and aggregated particles, respectively). CAMV is serologically distantly related to bean common mosaic virus, but not to bean yellow mosaic or eight other morphologically similar viruses. It is a typical but distinct member of the potato virus Y group.
Soil fumigation with methyl bromide: the uptake and distribution of inorganic bromide in tomato plants
Authors: KEMPTON R. J. , MAW G. A. 
Published: February 2008

SUMMARYTomato plants grown in soil previously fumigated with methyl bromide accumulated inorganic bromide in the foliage. The concentration present depended on the rate of application of methyl bromide to the soil and on the interval between, soil fumigation and planting, two factors determining the concentration in the soil of inorganic bromide arising from the breakdown of the fumigant.The concentration of bromide in the leaves decreased from the base to the tip of the plant, and increased with the age of the tissue.Bromide was accumulated in the fruit, but to a lesser extent than in the leaves. Mature fruit from plants grown in soil fumigated at the commercially applied rate of 1.5 lb/100 ft2 (73 g/m2) contained at the most 45 μg/g of fresh tissue, and generally not more than half this value. The concentration of bromide in fruit was related to the concentration of inorganic bromide present in the soil, but not to the state of ripeness or the position of the fruit on the plant.Similar results were obtained for leaves and fruit from plants grown in soil supplemented with inorganic bromide.
The early relative growth rates of six lettuce cultivars as affected by temperature
Authors: SCAIFE M. A. 
Published: February 2008

SUMMARYSix lettuce cultivars were grown to a dry weight of about 0.2 g per plant at four constant temperatures with high light intensity and ample nutrients. Relative growth rates (RGR) were sigmoidally related to temperature, averaging 0.11 g/g/day at 10 °C and 0.35 g/g/day at 22 °C. The cultivars Cobham Green and Avoncrisp had higher RGRs than the others, but the cultivar‐temperature interaction was not statistically significant. Temperature affected both components of RGR, i.e. net assimilation rate and leaf area ratio, about equally: the faster‐growing cultivars had higher net assimilation rates than the others. Growth rate predictions from the cabinet work agreed fairly well with observations made in the field.
Infection of cereal aphids by the fungus Entomophthora
Authors: DEAN G. J. W. , WILDING N. 
Published: February 2008

SUMMARYThree species of Entomophthora killed many Metopolophium dirhodum, M. festucae and Sitobion avenae on wheat at Harpenden, Hertfordshire, in 1971. Rainfall was low and aphid numbers were small in May and there was no Entomophthora infection. E. planchoniana first infected M. dirhodum early in June and the percentage of each aphid species infected increased during and after heavier rain in the first 2 weeks of June. M. dirhodum and S. avenae were most often infected by E. planchoniana, and the less common M. festucae mostly by E. aphidis and E. thaxteriana. Relative frequencies of E. aphidis and E. thaxteriana were largest before, and of E. planchoniana after, mid‐July. The largest percentages infected were 53% of M. dirhodum and 30% of S. avenae during the second half of July and 60% of M. festucae in late June. The percentages of old nymphs and apterous adults that were infected were similar and only about half those of infected alatae.
Effects of black scurf (Rhizoctonia solani) on potatoes
Authors: HIDE G. A. , HIRST J. M. , STEDMAN O. J. 
Published: February 2008

SUMMARYKing Edward and Majestic seed tubers, selected as ‘clean’ (macroscopically symptomless), moderate and severe according to the extent of black scurf, were planted in field experiments at Rothamsted between 1964 and 1968. Seed infection sometimes delayed plants emerging but did not affect final plant populations. Crops from severely diseased seed yielded, on average, 7% less than ‘clean’ tubers (King Edward 6–8% less and Majestic 0–20% less). Seed infection affected tuber size distribution; compared with ‘clean’ seed, severely infected King Edward seed yielded slightly more chats (< 1 ½ in, 3.8 cm) and 1.5 ton/acre (3.8 t/ha) less large tubers (2 ¼–3 ¼ in, 5.7–8.3 cm). The effects were similar with Majestic although differences were smaller. However, total yields from diseased stocks (unselected) seldom differed significantly from the ‘clean’ tubers selected from them. Crops from moderately and severely diseased seed had more Corticium on stems and black scurf on tubers and usually less Oospora pustulans than from ‘clean’ seed.
A comparison of some properties of four strains of cherry leaf roll virus
Authors: JONES A. T. 
Published: February 2008

SUMMARYThe elm mosaic and golden elderberry strains of cherry leaf roll virus (CLRV) and a strain from cherry and from rhubarb were very similar in their host range, symptomatology and properties in vitro. However, only the rhubarb isolate infected rhubarb systemically and only the golden elderberry isolate infected Sambucus nigra systemically. Purified preparations of all strains contained isometric particles which sedimented as two nucleoprotein components with sedimentation coefficients of about 115 S and 128 S. The elm mosaic strain was the least stable in vitro and was the most difficult to purify. In plant‐protection tests, one‐way protection occurred between tomato ringspot virus and each of the four CLRV strains. However, whereas the elm mosaic, golden elderberry and the cherry strains protected against one another, they did not protect against infection with the rhubarb strain.
Hollow heart of pea (Pisum sativum)
Authors: GANE A. J. , BIDDLE A. J. 
Published: February 2008

SUMMARYSamples of pea seed which had failed in the field were frequently found to be affected by hollow heart and it was noted that most of those affected by the disorder were triangular in cross‐section, rather than square. Seedlings from triangular seed were less vigorous and more readily killed in adverse conditions of soil and weather. Peas selected as of high vigour by the electro‐conductivity test showed differences in percentage hollow heart which were associated with differences in field losses. Laboratory tests showed that the proportion of seeds displaying symptoms varied according to the substrate used and that both the proportion showing symptoms and the germination capacity fluctuated during storage.
Some factors influencing spore germination and penetration of Alternaria longipes
Authors: NORSE D. 
Published: February 2008

SUMMARYThe ranges over which the germination of conidia of Alternaria longipes was > 50% were 10–35 °C on agar and 15–30 °C on tobacco leaf disks. Germination was optimal at 22.5 °C; so was germ‐tube growth, reaching c. 300 and 102 μm on agar and leaf disks respectively after 12 h. On average, 27% more conidia germinated and germ‐tubes were 62% longer on disks from leaves washed for 5 min under running water than on disks from unwashed leaves.At controlled saturation deficits germination after 8 h at 1.1 and 2.3 mb was 42.3 and 9.3% respectively and the rate of germ‐tube growth was < 0.8 μm/h, compared with 94.4% and 8.3 μm/h in standing water. These results, together with some field data, suggests that germination in the field is largely restricted to periods when free moisture is present on leaves. In Malawi, leaf temperatures and the duration of dew at night were adequate to allow germination and penetration in the absence of rain.Pollen, when applied with the inoculum, had little effect on the number of germinated conidia, but caused a c. tenfold increase in the number of successful penetrations.
Colonization of adult lettuce plants by Bremia lactucae
Authors: DIXON G. R. , TONKIN M. H. , DOODSON J. K. 
Published: February 2008

SUMMARYStudies were made of the infection by Bremia lactucae of a range of lettuce cultivars at the adult plant stage, under conditions of artificial and natural epidemic. The pathogen invaded at least the ten oldest leaves of many cultivars, the leaf area affected declining from the oldest to the youngest leaves. Two assessment methods were compared: (1) the percentage area infection on individual leaves and (2) the percentage area infection on the inverted basal area as a whole. Results from the two methods agreed closely under conditions of artificial inoculation and in a natural epidemic. It is concluded that both methods should be used for detailed studies, but method 1 restricted to the oldest five leaves. At least two assessment dates are required since on individual cultivars there were differences in the leaf area infected at various assessment dates. This is probably influenced by the cycle of growth and sporulation of B. lactucae and by the effects of invasion by secondary pathogens such as Botrytis cinerea.
The influence of the testa, damage and seed dressing on the emergence of groundnut (Arachis hypogea)
Authors: CARTER J. B. H. 
Published: February 2008

SUMMARYThe effects of damaging the testa and the application of seed dressings were examined in field trials on several short‐and long‐season cultivars of groundnut (Arachis hypogea) with differently‐pigmented testas at Samaru, Nigeria, in 1967. There was a high correlation between the number of seedlings which emerged in these trials and the resistance or susceptibility of the seed to invasion by the fungus Aspergillus flavus, as assessed by laboratory tests. When the testa was undamaged the emergence of white (susceptible) seed was only 50% while that of coloured (resistant) seed was between 95 and 98%. Damage to the testa by scratching greatly decreased emergence. The application of seed dressing increased the emergence of susceptible seed and also restored the emergence of scratched seeds to the level of undamaged seeds. The effect of the complete removal of the testa was not counteracted by seed dressing; naked seeds, with and without dressing, gave c. 10% emergence. The importance of pigment in the testa, the condition of the seed and the effects of seed dressing are discussed.
Effects of heat shock treatment on symptom development in tobacco leaves inoculated with potato mop‐top virus
Authors: JONES R. A. C. 
Published: February 2008

SUMMARYPMTV normally causes necrotic ringspot local lesions in Xanthi‐nc tobacco leaves at 15 °C but not at 22°. Dipping the leaves once in hot water at different intervals after inoculation induced necrotic reactions even at 22°. Successive concentric rings, one for each day of the interval between inoculation and treatment, were sometimes induced at 22°; these even formed in continuous lighting, suggesting an intrinsic diurnal rhythm. No lesions were induced at 22° by dipping inoculated leaves in ice‐cold water.Samsun tobacco inoculated with PMTV developed very few lesions at 15°. Many more were induced however, by dipping the leaves in hot water after inoculation.The results suggest some similarities between PMTV and TMV, and the two viruses have been reported as serologically related; but PMTV did not protect plants against TMV, for TMV challenge‐inoculations induced lesions within existing PMTV lesions.
Influence of rooting‐medium temperature on growth of Lycopersicon esculentum
Authors: COOPER A. J. 
Published: February 2008

SUMMARYThe influence of rooting‐medium temperatures (maintained constant for 54 days from sowing) on tomato seedling growth was exerted primarily on development during the first 2 weeks after sowing, when an optimum emerged at 25 °C. This influence was attributable to an effect of temperature on the partitioning of dry matter between root and shoot during a few days before and after the start of photosynthesis. The adverse effect of suboptimal (but not supra‐optimal) temperature was also associated with a reduction in the phosphorus content of the tissue, there being little effect on either nitrogen or potassium content.
Verticillium wilt of pea (Pisum sativum)
Authors: ISAAC IVOR , ROGERS W. G. 
Published: February 2008

SUMMARYA wilt disease of garden pea (Pisum sativum) caused by Verticillium dahliae is described and the range of pathogenicity of the isolate investigated. It is pathogenic to potato, sweet pea, antirrhinum and broad bean and isolates of V. dahliae from potato, lucerne and sweet pea and V. albo‐atrum from lucerne are pathogenic to pea.Since the most common disease symptoms, acropetal progression of chlorosis and necrosis of the leaves followed by premature defoliation are indistinguishable from natural senescence, it is probable that disease and senescence symptoms are confused in the field.The premature defoliation results in marked reduction in green leaf area, leaf dry weight and pod yield.
The influence of normal tillage and of non‐cultivation on Verticillium wilt of the hop
Authors: SEWELL G. W. F. , WILSON J. F. 
Published: February 2008

SUMMARYThe influence of a non‐cultivation (herbicide) regime on wilt incidence was compared with that of normal tillage in three observation trials on commercial hop farms. Non‐cultivation resulted, on average, in 28% wilt control when wilt incidence was high. When wilt incidence was low there was a tendency for more wilt to occur with non‐cultivation.The reduction in wilt under non‐cultivation was probably mainly due to the virtually complete eradication throughout the year of alternative weed host plants, but other possible influential factors were: (i) the absence of root severance which could result in increased inoculum potential, (ii) changes in the pattern of hop root distribution, and (iii) the inhibiting action of simazine on root growth in surface soil resulting in reduced contact between roots and surface‐borne inoculum.The lack of disease control with non‐cultivation when wilt incidence was low was attributed to differential effects of the treatments on nitrogen metabolism or availability.The factors contributing to disease control under non‐cultivation were considered to represent aspects of the process of sanitation, and the data were interpreted in terms of the sanitation ratio (sensu van der Plank). When wilt incidence was high the sanitation ratios at the three sites were similar.Modified cultural practices provide an important supplement to genetic resistance in the control of hop wilt. These practices (restricted use of nitrogen fertilizers and efficient sanitation with respect to the crop plant as well as to weeds) have proved economical and beneficial for hop culture in presence of wilt, under the threat of wilt, and in the absence of wilt.
Effects of cultural conditions on the mycelial growth of healthy and virus‐infected cultivated mushroom, Agaricus bisporus
Authors: LAST F. T. , HOLLINGS M. , STONE OLWEN M. 
Published: February 2008

SUMMARYThere was a significant inverse correlation (P= 0=001) between concentrations of mushroom viruses 1 and 2 in sporophores and amounts of mycelial growth on malt agar of isolates taken from them. Increasing virus concentrations decreased linear growth of one mushroom strain from 76 mm (healthy) to 35 mm (mildly infected) and 7 mm (severely infected) when incubated at 25°C for 3 wk.Mycelial growth rates of isolates from healthy and from virus‐infected mushrooms were compared on eleven agar media. All media clearly differentiated between healthy and severely infected isolates, but fewer separated healthy from mildly infected isolates. Those that did contained maltose, sucrose or starch as carbon source. Media containing peptone usually gave better differentiation than those with other sources of nitrogen, but the best differentiation was obtained with malt agar.Growing healthy and infected isolates on a range of media affected their subsequent growth on malt agar, the growth of some isolates apparently being changed permanently after 2 months on some of the different media. Whereas none of the infected isolates grew less rapidly after this treatment, the growth of some of the mildly infected isolates improved to such an extent that they could no longer be distinguished from healthy isolates.After heat‐treatment (1–6 wk at 33°C), mycelial growth rates of infected isolates were increased, but viruses 1 and 2 were not always eliminated unless the heat‐treatment was begun immediately after subculture.Mycelial growth rate and colony characters are not infallible criteria of the presence or absence of virus, a feature of particular significance when checking the health of mushroom spawn.
The photosynthetic activity of the developing hop cone
Authors: PEAT W. E. , THOMAS G. G. 
Published: February 2008

SUMMARYCarbon dioxide exchange of the developing hop cone was measured in field and laboratory experiments. Older cones showed a clear response of CO2 exchange to light intensity, indicating photosynthetic activity, but this rarely exceeded respiratory loss. Cones therefore made little photosynthetic contribution to their growth. Young cones showed no response of CO2 exchange to light intensity and therefore possessed negligible photosynthetic activity. The initiation of photosynthesis was sudden and coincided with the onset of rapid cone growth and with the response of water loss to light intensity. It is suggested that the maturation of stomata is linked with the initiation of gas exchange.
Incidence and control of Colletotrichum musae on bananas in the Windward Islands
Authors: GRIFFEE P. J. , BURDEN O. J. 
Published: February 2008

SUMMARY Colletotrichum musae was isolated from banana hands I wk after bunch emergence and in subsequent weeks both from fingers and from crown tissue. Other fungi including Fusarium semitectum and Nigrospora sphaerica were also isolated. Four pre‐harvest sprays of benomyl, each at 1000μg/ml, controlled these fungi on unripe fruit, but unsprayed bunches covered with polyethylene showed rather increased infection rates.Latent infections of C. musae giving lesions on ripe fruit were also largely controlled by the above sprays, but crown rot appearing at this stage was not reduced. One post‐harvest benomyl dip at 250 μg/ml however effectively controlled crown, wound and latent infections. For this reason and also because of the demonstrated risk of benomyl‐resistant isolates of C. musae resulting from pre‐harvest treatment, it is suggested that pre‐harvest spraying is unnecessary.
A virus causing ringspot of Passiflora edulis in the Ivory Coast
Authors: WIJS J. J. De 
Published: February 2008

SUMMARYA mechanically transmissible virus causing leaf mottling and ringspotting of Passiflora edulis var. flavicarpa in the Ivory Coast is described. Its particles are flexuous rods 810–830 nm long and 15 nm wide. It infects mainly species of Passifloraceae and Leguminosae; Passiflora foetida is a good diagnostic host. Aphis gossypii and Aphis spiraecola transmit the virus after brief acquisition feeds. Seed transmission was not detected. In crude sap of P. edulis, infectivity was lost after 10 min at 65–70 °C, 12–14 days at 24 °C or dilution to 10‐7. A purification method is described, using Triton‐X‐100 as clarifying agent. The virus is serologically related but not identical to passionfruit woodiness virus from Queensland. The virus seems to belong to the potato virus Y group and has the cryptogram */*:*/(6):E/E:S/Ap. It is designated passionfruit ringspot virus.
Nematodes associated with forest and woodland trees in Scotland
Authors: BOAG B. 
Published: February 2008

SUMMARYA survey of the nematode genera associated with trees in Scotland showed that Tylenchus sensu lato, Aphelenchoides, Tylencholaimus, Trichodorus, Helicotylenchus, Rotylenchus, Criconemoides s.l., Hemicriconemoides, Tylencho‐rhynchus, Pratylenchus and Paratylenchus s.l. were commonly found in soil samples collected from around the roots of coniferous and deciduous trees. Only Criconemoides s.l. appeared to have a significant preference for deciduous woods.The presence of undergrowth in woods and forests was associated with significantly greater numbers of plant‐parasitic nematodes.Measurements of abiotic factors indicated that, in mineral soils, pH affected the incidence of most genera, but soil type, moisture content and altitude had little effect.
Heritability of bulb shape in some north European onion varieties
Authors: DOWKER B. D. , FENNELL J. F. M. 
Published: February 2008

SUMMARYHeritabilities for shape index (the ratio of bulb height to diameter), based on parent—offspring regressions, were calculated for north European onion cultivars and inbred lines derived from them. Heritability estimates of 0·46 and 0·47 respectively were obtained for the two groups, S0 parent bulbs giving S1 progenies, and S1 parent bulbs giving S2 progenies.Within each offspring progeny, the regression of bulb shape index on loge bulb weight was significant. The regressions were used to estimate the mean shape indices of the progenies at the same mean bulb weight as their parents, and a series of ‘corrected’ progeny shape means thus obtained. Recalculation of the heritabilities using these ‘corrected’ progeny means gave increased estimates (0·78 and 0·84).By using this regression approach, the breeder can achieve high heritabilities when selecting for a specific mean shape index.
Some factors affecting the efficiency of water‐traps for capturing cabbage root flies
Authors: FINCH S. , SKINNER G. 
Published: February 2008

SUMMARYSeveral factors influencing the efficiency of water‐traps in capturing cabbage root flies were studied at Wellesbourne in 1971 and 1972. In both the laboratory and field, approximately twice as many flies were caught in fluorescent as in non‐fluorescent yellow traps. Depending upon trap density, addition of a source of the attractant allylisothiocyanate (ANCS) increased the numbers of females captured by approximately twofold in fluorescent traps and from two‐ to sevenfold in non‐fluorescent traps. Traps were equally efficient irrespective of whether the ANCS was renewed every 2, 3, 4 or 5 days. On the first day of trapping, the number of flies caught per unit area was linearly related to the square root of the number of traps in that area. On the following days the rate was probably in equilibrium with the combined effect of immigration and the rate of development of responsive flies in the trapping zone. Most males were caught 30 cm above the soil surface and most females at soil level. Traps 120 cm above the soil surface caught few flies.Populations of marked flies were released into large field cages containing both a section of hedgerow and a plot of cauliflowers. Even after a week, only 81 % of the males and 55 % of the females had been recaptured from the most responsive of these captive populations. Furthermore, only 30 % of females were recaptured when they were more than 8 days old, the age at which most probably enter the new host‐crop.