bluuebunny/crossref_metadata_2025 huggingface dataset:
Restricted distribution of potato leafroll virus antigen in resistant potato genotypes and its effect on transmission of the virus by aphids
Authors: BARKER H. , HARRISON B. D.
Published: February 2008

Enzyme‐linked immunosorbent assay was used to measure the concentration of potato leafroll virus (PLRV) antigen in different parts of field‐grown secondarily infected plants of three potato genotypes known to differ in resistance to infection. The antigen concentration in leaves of cv. Maris Piper (susceptible) was 10–30 times greater than that in cv. Pentland Crown or G 7445(1), a breeder's line (both resistant). Differences between genotypes in antigen concentration were smaller in petioles and tubers (5–10‐fold) and in above‐ground stems (about 4‐fold), and were least in below‐ground stems, stolons and roots (about 2‐fold). PLRV antigen, detected by fluorescent antibody staining of tissue sections, was confined to phloem companion cells. In Pentland Crown, the decrease in PLRV antigen concentration in leaf mid‐veins and petioles, relative to that in Maris Piper, was proportional to the decrease in number of PLRV‐containing companion cells; this decrease was greater in the external phloem than in the internal phloem. The spread of PLRV infection within the phloem system seems to be impaired in the resistant genotypes.

Green peach aphids (Myzuspersicae) acquired < 2800 pg PLRV/aphid when fed for 4 days on infected field‐grown Maris Piper plants and < 58% of such aphids transmitted the virus to Physalis floridana test plants. In contrast, aphids fed on infected Pentland Crown plants acquired <120 pg PLRV/aphid and <3% transmitted the virus to P. floridana. The ease with which M. persicae acquired and transmitted PLRV from field‐grown Maris Piper plants decreased greatly after the end of June without a proportionate drop in PLRV concentration. Spread of PLRV in potato crops should be substantially decreased by growing cultivars in which the virus multiplies to only a limited extent.
An alternative method of flax retting during dry weather
Authors: SHARMA H. S. S.
Published: February 2008

During exceptionally dry and hot weather undesiccated flax (Linum usitatissi‐murri) and flax desiccated with glyphosate that was pulled and laid on the ground to dew‐ret, retted 1–2 wk before flax that was desiccated and left as a standing crop. This was because dew‐retted flax was colonised by fungi faster than that left standing. Cladosporium herbarum, Epicocum nigrum and yeast, including Aureoba‐sidium pullulans, appeared first; they were followed by Alternaria alternata, Fusarium culmorum and Phoma, Mucor and Rhizopus species. The standing crop retted more slowly despite the presence of greater concentrations of cell‐wall degrading enzymes. However, the fibres of flax retted as a standing crop retained more of their strength than those of flax retted on the ground. Thus dew‐retting provides means of retting when the weather is dry and hot.
Radiation absorption and growth of Viciafaba under shade at two densities
Authors: KASIM K. , DENNETT M. D.
Published: February 2008

Faba beans were grown under various shading treatments at densities of 20 and 60 plants m‐2. The amount of PAR absorbed by each treatment was estimated from measured leaf area index. The conversion factor (E, g MJ‐1) relating dry matter production to absorbed PAR increased as shading increased. Application or removal of shade changed E rapidly, though there was some evidence for an increased value of ɛ persisting after removal of shade. Differences in dry matter production between the two years were due to as much to differences in ɛ as to changes in the amount of light absorbed. Increased plant density increased PAR absorbed but hardly affected e.
Changes in peel pigmentation during ripening of mango fruit (Mangifera indica var. Tommy Atkins)
Authors: MEDLICOTT A. P. , BHOGAL MOHINDER , REYNOLDS S. B.
Published: February 2008

The pigments in the peel of Tommy Atkins mango were analysed at six stages during ripening at 22 oC. The loss of green colour and the development of yellow colouration was associated with an almost complete loss of chlorophyll and an increase in carotenoids. Anthocyanin content showed a slight decrease during ripening. An ultrastructural study showed plastids in green fruit with a well developed grana network system. On ripening the chloroplasts underwent extensive disorganisation which was associated with the development of large osmiophilic globules.
A rain tower and wind tunnel for studying the dispersal of plant pathogens by rain and wind
Authors: FITT B. D. L. , WALKLATE P. J. , MCCARTNEY H. A. , BAINBRIDGE A. , CREIGHTON N. F. , HIRST J. M. , LACEY M. E. , LEGG B. J.
Published: February 2008

The rain tower/wind tunnel complex at Rothamsted consists of a rain tower (height 11 m, cross‐section 1 m2) linked to the upwind end of a wind tunnel (length 12 m, cross‐section 1 m2), which may be operated in either an open or a closed configuration. At the top of the rain tower, water drops with diameters of 2.5 to 5 mm are produced by a drop generator, which can be fitted with different nozzles. Simulated rain with a drop diameter of 1 to 3 mm is produced at a rate of 8 to 12 mm h‐1 by a rain generator with an area of 52 × 67 cm. The rain tower may be operated in conjunction with the wind tunnel in an open configuration. The windspeed can be decreased from a maximum of 8 m s‐1 by decreasing the speed of the fan. The wind tunnel has its own internal lighting. When the wind tunnel is in a closed configuration, temperature and humidity can be controlled in the range 12 oC (62–80% r.h.) to 35 oC (22–50% r.h.). Data presented illustrate the use of this rain tower/wind tunnel complex to study dispersal of plant pathogen spores by rain‐splash or wind.
A comparison of methods of seed tuber inoculation for assessing the susceptibility of potato cultivars to blackleg (Erwinia carotovora subsp. atroseptica) in the field
Authors: LAPWOOD D. H. , READ P. J.
Published: February 2008

Experiments were done with the aim of developing a reliable method for assessing the susceptibility of potato cultivars to blackleg caused by Erwinia carotovora subsp. atroseptica, in the field. Over four years seed tubers were either stab‐inoculated at the heel‐end prior to planting, vacuum infiltrated with bacteria just after harvest or vacuum infiltrated prior to sprouting and after ‘cutting’ or ‘pricking’.

Stab inoculation produced fewer diseased plants but generally a greater range of symptoms than vacuum infiltration. Vacuum infiltrated ‘cut’ seed gave most disease whereas infiltration at harvest and infiltration of ‘pricked’ seed gave similar disease incidence. The cultivar Maris Piper was more resistant than Desiree in 1981 and 1982, and Pentland Javelin than Ulster Sceptre in 1983 and 1984, largely irrespective of the inoculation treatment. Irrigation improved yields but did not affect disease symptoms.

In further field experiments over three years, each with a minimum of 20 cultivars, seed tubers were sliced just before planting at a standard distance from the apex and inoculated by applying a pad impregnated with inoculum. Differences were shown between cultivars and it is suggested that the method could be adapted for testing for blackleg susceptibility under controlled environment conditions.
Purification and properties of lucerne Australian symptomless virus, a new virus infecting lucerne in Australia
Authors: REMAH A. , JONES A. T. , MITCHELL M. J.
Published: February 2008

A virus with isometric particles c. 26–28 nm in diameter isolated from naturally infected lucerne (Medicago sativa) in Australia and reported there to be a strain of lucerne Australian latent virus (LALV), is shown to be a distinct virus. The virus, called lucerne Australian symptomless (LASV), was mechanically transmitted to 10 of 22 plant species inoculated, but only induced symptoms in three Chenopodium species and Gomphrena globosa. Virus particles occurred in relatively low concentrations in plant sap, and the virus could not be reliably maintained in culture by serial transmission to plants during winter (October‐April). During the summer, sap of infected C. quinoa remained infective after diluting 10‐2 but not 10‐3, after heating for 10 min at 50 but not 55 oC and after storage for 24 days (the longest period tested) at 20, 4 and ‐15 oC. LASV was seed‐borne to 6% of C. quinoa seedlings. Partially purified preparations of virus particles contained one nucleoprotein component with a sedimentation coefficient of c. BOS. Particles contained two polypeptide species of estimated mol. wts 26 000 and 40 000, and two ssRNA species which, when denatured in glyoxal, had apparent mol. wts of 2–5 times 106 and 1–4 times 106. The infectivity of virus RNA was abolished by incubation with proteinase K. Purified particles of LASV reacted with homologous antiserum (gel diffusion titre 1:256) but not with antiserum to LALV or to 13 other plant viruses with isometric particles including arracacha B (AVB), broad bean wilt, rubus Chinese seed‐borne (RCSV) and strawberry latent ringspot (SLRV) viruses, and five comoviruses.

These properties distinguish LASV from LALV and from all recognised nepoviruses and comoviruses. Its closest affinities are with SLRV, RCSV and possibly AVB; these viruses may comprise a distinct virus group or nepovirus subgroup.
Inheritance of resistance to yellow rust (Phragmidium rubi‐idaei) in red raspberry
Authors: ANTHONY VIVIENNE M. , WILLIAMSON: B. , JENNINGS D. L. , SHATTOCK R. C.
Published: February 2008

The inheritance of resistance in red raspberry (Rubus idaeus) to yellow rust (Phragmidium rubi‐idaei) was studied in a diallel cross among the cultivars Boyne, Meeker, Mailing Jewel, Glen Prosen and Glen Clova. The progenies and clonally propagated parents were exposed initially in a rust‐infected plantation where the incidence and severity of infection was assessed at the telial stage. The following spring leaves on new canes of the same plants were inoculated with urediniospores in a glasshouse at 18 ± 2 °C. The latent period and number of uredinia per cm2 of abaxial leaf surface were determined 13 and 18 days after inoculation. Cv. Boyne developed only chlorotic flecking on inoculated leaves in the glasshouse and no sporulation was observed. It is postulated that this reaction was determined by a major gene which is designated Yr. Some of the other parents showed incomplete resistance of the slow rusting type, and segregants of Boyne selfed that were susceptible also showed low levels of rust, which suggests that Boyne carries both major‐ and minor‐gene resistance. Diallel analyses of both the field and glasshouse data from the susceptible segregates indicated that the degree of incomplete resistance present was determined predominantly by additive gene action, though small but significant non‐additive effects also occurred: cv. Meeker was the most resistant parent and contributed the most resistance to the progenies.

The Meeker progenies also segregated for gene H, which determines cane hairiness and is known to be associated with resistance to other diseases. Segregants without hairs (genotypes hh) were found to be the more resistant to rust.
The capture efficiency of the Dietrick vacuum insect net for aphids on grasses and cereals
Authors: HAND S. C.
Published: February 2008

The capture efficiency of the Dietrick vacuum insect net (D‐vac) for cereal aphids on grasses and cereals was investigated in the field and laboratory. Capture efficiency varied between different aphid species and instars and different plant species, age and density. Numerous other factors probably also affect its capture efficiency. Despite this variability, the D‐vac is suitable for determining population structure of aphids and for detecting alatae. It may also remain the only method to obtain some quantitative measurements of populations of insects at low densities.
Epidemics of take‐all during 16 years of continuous spring barley
Authors: HORNBY D. , HENDEN D. R.
Published: February 2008

In 1969 spring barley was the third consecutive cereal crop following a mixed rotation, which included cereals, on a sandy‐loam at Woburn, Beds. The incidence (42%) of roots with take‐all was approximately eight times greater than in any of the next 11 crops of an ensuing spring barley monoculture. Until 1981 it was assumed that the peak of take‐all in 1969 represented the terminal phase of the epidemic that preceded take‐all decline and that the subsequent low level of take‐all was a consequence of take‐all decline. In 1981 a secondary outbreak of take‐all infected 12% of roots and in the next two years 16% and 27.5% of roots were infected, but in 1984 the disease resumed a very low incidence (0.6% of roots infected) which characterised most of the 1970s.

The most probable number of infectious fragments per 150 cm3 of soil was determined by bioassay on 115 occasions. The maximum recorded was 36.5 in June 1969 and the most recorded in the secondary outbreak was 29.7 in July 1983. From early 1971 to mid‐1981 the numbers were always under five and mostly less than one per 150 cm3. Soil collected in mid‐August 1969 after harvest was most infectious (50 roots infected per 190 cm3 of soil) in bioassays and thereafter until mid‐1981 there were never more than 6.5 infected roots per 190 cm3 of bioassay soil. Soil infectivity in the second epidemic never matched that of the first, peaking at 23 roots infected in 190 cm3 of soil in early July, 1983.

Take‐all on a silty clay loam, 13 km to the east at Silsoe, was prevalent in a third spring barley in 1973. Its decline to very little in a seventh crop in 1977, was interrupted in 1975 by a slight, temporary recovery also recorded at Woburn. Although changes in cultivars, nitrogen rates and sowing dates may have accounted for some of the changes in disease it is suggested that the polyetic epidemic that began in spring barley monoculture at Woburn in the late 1970s and entered its terminal phase in 1983 was weather‐determined and reflected a general, long‐term, trend in the UK and Ireland.
Serological and biological characterisation of isolates of barley yellow dwarf virus in Sweden in 1983
Authors: EWEIDA M.
Published: February 2008

In 1983, cereal plants showing symptoms of barley yellow dwarf virus (BYDV), collected from 15 localities in Sweden, were tested for BYDV using enzyme‐linked immunosorbent assay (ELISA). Antisera against two Swedish isolates of BYDV were used, a mild isolate (27/77) transmitted specifically by Sitobion avenae and a severe one (39/78) transmitted mainly by Rhopalosiphum padi. No virus was detected in 57 of 607 plants of oats and barley tested. Of the 550 plants in which virus was detected, 366 were infected with viruses similar to isolate 27/77, 116 with viruses similar to 39/78 and the remaining 68 reacted strongly with both antisera. When tested, the latter isolates were shown to be mixtures.

Thirty‐nine selected samples were also tested with antisera against the USA isolates RPV, RMV, MAV and PAV, and for transmission by S. avenae and R. padi. Twenty‐six of these samples were transmitted specifically by S. avenae, one was transmitted only by R. padi and the remaining 12 samples were shown to be infected with a mixture of an S. avenae‐specific isolate and one transmitted mainly by R. padi. Antisera against PAV and MAV each detected all isolates tested and the results were very similar to those with the antisera to the 39/78 and 27/77 isolates, respectively. None of the field isolates reacted with antisera against RMV or RPV.

It was concluded that 1983 was an epidemic year for BYDV in Sweden and that isolates specifically transmitted by S. avenae predominated. Symptoms of infection by these isolates on oat plants ranged from mild to severe.
Immunity from raspberry vein chlorosis virus in raspberry and its potential for control of the virus through plant breeding
Authors: JENNNINGS D. L. , JONES A. T.
Published: February 2008

The apparent immunity of five cultivars of red raspberry and two of black raspberry from graft inoculation with raspberry vein chlorosis virus (RVCV) was established or confirmed. The segregations obtained from selfs and crosses with infectible cultivars of four of the red raspberry cultivars and the black raspberry cultivar Cumberland indicated that the apparent immunity was not determined by a single major gene. The range in severity of the symptoms expressed in the segregates suggested either that sensitivity to infection is under separate genetic control, or that immunity and sensitivity are opposite expressions of a character which varies continuously rather than discontinuously. Nevertheless, although the precise mechanism of immunity remains unclear, the high proportion of immune segregates obtained in crosses indicated that breeding for immunity from RVCV is feasible and offers the best prospect for control of the virus.
Apparatus for determining oxygen in small gas samples
Authors: BANKS NIGEL H.
Published: February 2008

A simple modification to an electronic O2 analyser is described which enables accurate determination of O2 in small gas samples. The response to O2 concentration is linear over the range 0–21% by volume and as little as 0.07 μl of O2 can be detected. Analysis of a 25 μl sample takes 25 s.
Observations on the number of cereal aphids on the soil in relation to aphid density in winter wheat
Authors: SOPP P. I. , SUNDERLAND K. D. , COOMBES D. S.
Published: February 2008

The numbers of cereal aphids on the soil surface was assessed by soil samples and by counting the numbers captured in pitfall traps. A relationship was found by both methods between the density of aphids on the plants and the numbers of aphids on the soil. This relationship indicated that a higher proportion of the aphid population was on the soil surface at the lower densities on the plant. Reasons for this relationship are suggested and discussed.
Bacterial soft rot of tomato in plastic greenhouses in Crete
Authors: MALATHRAKIS N.E. , GOUMAS D.E.
Published: February 2008

During recent years a new disease has been noticed on tomatoes grown in Polythene greenhouses in Crete. Early symptoms are yellowing of the lower leaves, and a yellow brown discoloration of the pith and stem xylem. As leaves wilt and die there is progressive yellowing towards the top of the plants. A progressive disintegration of the cortical tissues follows which results in a soft rot and a longitudinal splitting of the stem running mainly upwards. Soft rot of the fruits rarely appears. Severely infected plants may wilt and die, but other less affected plants often survive and yield normally. Very vigorous plants grown under humid conditions are more susceptible. Often more than 20% of the plants are infected. Isolations were made from stem (xylem, cortex and pith), from leaf xylem and from fruits of infected tomato plants collected throughout the island from 1979 to 1985. Bacteria of the genus Erwinia and Pseudomonas were consistently isolated. On the basis of physiological and biochemical characters of 49 representative pathogenic isolates, 22 were identified as Erwinia carotovora subsp. carotovora, 10 as Erwinia carotovora subsp. atroseptica, four as Pseudomonas viridiflava and 13 as Pseudomonas fluorescens biotype I. All disease symptoms were reproduced when artificial inoculations were made with the above isolates in the laboratory (20°C and 100% r.h.) on 3–4 week tomato plants and in a commercial greenhouse on 4–5 months tomato plants. Bacteria used for inoculations were reisolated. Results indicated that the disease symptoms as described may be caused by four different bacteria species.
The influence of mixed cropping on the control of potato bacterial wilt (Pseudomonas solanacearum)
Authors: AUTRIQUE A. , POTTS M. J.
Published: February 2008

Experiments with bacterial wilt (Pseudomonas solanacearum) race 3 showed that the practice of intercropping potato with maize or haricot beans markedly reduced the incidence and rate of disease development in the potato crop. This reduction in disease was considered to be an effect of the increased distances between individual potato plants, their spatial arrangement and the presence between potato plants of root systems of other plant species, all of which resulted in a reduction in plant‐to‐plant transmission, via the roots. The lower potato plant population associated with intercropping resulted in a slower rate of inoculum build‐up in the soil and the presence of an intercrop further markedly reduced the inoculum build‐up. Where farmers retain tubers for seed, but where roguing of diseased plants is not practised, the isolation of plants through intercropping was considered to facilitate an efficient selection of healthy tubers.
Properties of a new strain of tobacco streak virus from Clematis vitalba (Ranunculaceae)
Authors: RANA G. L. , KRAJAČIĆ M. , ŠTEFANAC ZLATA , PLEŠE NADA , RUBINO LUISA , MILIČIĆ D.
Published: February 2008

A distinct strain of tobacco streak virus (TS V/Cle), isolated in Yugoslavia from wild Clematis vitalba showing chlorotic spots or yellow netting of the leaves and from many symptomless shrubs, is described.

TSV/Cle was seed transmitted in C. vitalba (70%), and in the experimental hosts Chenopodium quinoa (80%), Nicotiana benthamiana and N. megalosiphon. It was also detected in the pollen of infected C. quinoa. Purified virus preparations mostly contained quasi‐spherical particles measuring 24–26 × 28, 26–28 × 28–30 and 28–31 × 32–36 mn, and sedimented in sucrose density gradient and analytical centrifugation as three components with sedimentation coefficients of 76S, 87S and 98S. The virus contained a single polypeptide species of mol. wt of c. 25 000. Unfractionated TSV/Cle preparations contained four RNA species with mol. wts, estimated by gel electrophoresis in agarose, of 1.1 × 106, 0.9 × 106, 0.7 × 106 and 0.3 × 106. In comparative experiments, TSV/Cle differed from four reference strains of TSV (TSV/B, TSV/HF, TSV/RN, and TSV/Ro) in host range and in symptoms induced in some common hosts. In agar gel double diffusion tests it was more closely related to TSV/B and TSV/M (SDI = 5) than to TSV/HF (SDI = 7), TSV/RN (SDI = 7) or TSV/Ro (SDI = 5–8). Immunoelectrophoresis experiments clearly distinguished TSV/Cle from the reference strains. TSV/Cle strain was detected in C. vitalba plants from distant and climatically different regions in Yugoslavia.
Effects of 2,4‐D butyl vapour on the growth of six crop species
Authors: BREEZE V. G. , WEST CAROLINE J.
Published: February 2008

Six species of crop plants (tomato, lettuce, clover, cabbage, sunflower and field bean) were exposed to concentrations of 2,4‐D butyl in the range 3–50 ng/litre, for 3.5 h, using an air‐flow system. Symptoms of phytotoxicity were recorded during the following 4 wk, after which the plants were harvested. Sunflower and field bean were found to be most sensitive, with tomato, lettuce and cabbage less affected and clover least sensitive, on the basis of weight. Small tomato plants were more sensitive than ones approximately twice the weight. A 50% reduction in dry weight was caused by a 3.5h exposure to less than 3 ng/litre 2,4‐D butyl for sunflower, compared with over 50 ng/litre for clover. The ranking of sensitivities did not agree with reports based on liquid doses of 2,4‐D, especially for field bean, which was found to be more sensitive than previously thought.
Germination and effect of reduced humidity on expression of pathogenicity in Verticillium lecanii against the glasshouse whitefly Trialeurodes vaporariorum
Authors: DRUMMOND J. , HEALE J. B. , GILLESPIE A. T.
Published: February 2008

Fifteen isolates of the entomopathogenic fungus Verticillium lecanii, from various hosts and locations, were bioassayed in the laboratory at 19 ± 1°C and > 95% r.h. against fourth instar scales of Trialeurodes vaporariorum. Highly pathogenic isolates generally originated from whitefly; however, there was no correlation between conidiospore size or germination rate on agar, and pathogenicity. LT50 values ranged from 5.7 to > 9 days and LC50 (7 days) from 1.3 × 105 to 4.2 × 107 spores/ml. The effect of periods in low humidity (70% r.h.) following 16 or 96 h at > 95% r.h. after immersion of whitefly scales on tomato leaf discs in a suspension of 1 × 106 spores/ml, was compared for five isolates. Progressively longer periods at 70% r.h. following 16 h at > 95% r.h., reduced significantly (P < 0.001) the pathogenicity of all isolates. In these conditions isolate A was least affected by low‐humidity transfer. The high pathogenicity of isolate A was associated with its more rapid development on the host cuticle during the first 16 h in high humidity. When inoculated whitefly scales were transferred to 70% r.h. after a preliminary 96 h incubation in high humidity, all five isolates achieved a higher level of pathogenicity compared with their transfer to low humidity after 16 h high humidity. Thus the screening of V. lecanii isolates in limiting humidity conditions provided a more critical assessment of their pathogenicity and of their potential success in whitefly control relevant to the glasshouse environment.
A column elutriator for extracting cyst nematodes and other small invertebrates from soil samples
Authors: WINFIELD A. L. , ENFIELD M. A. , FOREMAN J. H.
Published: February 2008

A column soil elutriator (the Wye Washer) for extracting cyst nematodes and other small invertebrates from soil samples is described. Laboratory tests have shown the new equipment to achieve extraction rates equal to or better than existing techniques and to offer operational advantages also. Soil in quantities of up to 1 kg may be processed without drying or subsampling, the equipment can be left unattended once set to work, and can be used to extract a range of target organisms. There is only one working part (a valve) and no electrical parts, but water use and price is high. The Wye Washer is now used in the advisory entomology laboratory at Wye as the standard equipment for extracting cysts of Heterodera and Globodera, for eggs of cabbage root fly (Delia radicum) and for cocoons of black currant leaf midge (Dasineura tetensi).
The effect of inoculating flowers and developing fruits with Botrytis cinerea on post‐harvest grey mould of red raspberry
Authors: WILLIAMSON B. , McNICOL R. J. , DOLAN ALISON
Published: February 2008

Raspberry flowers were inoculated in the glasshouse and field with dry conidia of Botrytis cinerea and the fruits derived from them subjected to post‐harvest rot tests at c. 20°C and high humidity. Apparently healthy fully‐ripe picked fruits derived from inoculated flowers developed grey mould faster than those from non‐inoculated flowers in all tests.

In the glasshouse experiments, fruits from inoculated tightly closed flower buds rotted more slowly than those from inoculated open flowers or those at later developmental stages. Fruits from inoculated whole flowers rotted more rapidly than those from emasculated flowers; the addition of pollen to emasculated flowers had little effect on post‐harvest grey mould.

In the dry summer of 1984 no fruits in the field from inoculated whole flowers rotted before ripening, but in the wet season of 1985 pre‐harvest grey mould was common and the surviving healthy fruits rotted in c. 1 day after picking.

Only minor differences were detected in host susceptibility to post‐harvest grey mould in both glasshouse and field tests, the ranking of genotypes varied depending on whether or not flowers had been inoculated. The susceptibility of pistils of 40 Rubus genotypes to infection was examined 7 and 28 days after inoculation of stigmas with dry conidia. Conidia germinated on the stigmas and produced hyphae which grew through transmitting tissues of the styles to infect carpels symptomlessly in 17 red raspberries, one blackberry, two Rubus spp. and one hybrid. No germination occurred on stigmas of cv. Carnival and New York Selection 817.
The invertebrate population and response to pesticide treatment of two permanent and two temporary pastures
Authors: CLEMENTS R. O. , BENTLEY B. R. , NUTTALL R. M.
Published: February 2008

During 1979 and 1980 the herbage yields of two permanent pastures and two temporary swards were compared. All four swards received 250 kg N/ha per yr. The invertebrate population of all four swards was studied. Pot‐worms (Enchytraeidae) and some species with long life cycles, e.g. wireworms (Agriotes spp.) were more numerous in the permanent swards, but aerial species were more numerous in the temporary swards. A range of pesticide treatments was applied. At one temporary sward site, application of the broad‐spectrum pesticide aldicarb increased total annual yield of herbage by 16% in 1979 and 33% in 1980. Insecticide application at the same site resulted in no increase in herbage yield in 1979 and 12% yield increase in 1980. At the other three sites no significant increases in total annual yield were recorded in either year, but there were significant responses at one harvest or more at every site.
Effects of ethylene and acetylene on mango fruit ripening
Authors: MEDLICOTT A. P. , SIGRIST J. M. M. , REYNOLDS S. B. , THOMPSON A. K.
Published: February 2008

Mangoes (var. Tommy Atkins) were exposed to ethylene and acetylene over a range of concentrations at high humidity for 24 h at 25°C, then ripened in air alone. Ripeness was assessed after 4 and 8 days by analysis of texture, colour development, soluble solids and acid contents.

Ethylene in air at concentrations of 0.01 ml litre‐1 and above or acetylene at 1.0 ml litre‐1 were found to initiate ripening. Treatment with 0.01 ml litre‐1 acetylene resulted in limited softening but had no effect on the other ripening changes analysed. Individual ripening processes responded differently to treatment: texture changes were most rapidly affected, while the rate of acidity losses was often reduced in ethylene treated fruits. Acetylene‐treated fruits at concentrations of 0.01 and 0.1 ml litre‐1 showed delayed ripening when compared to those treated with either 1.0 ml litre‐1 acetylene or ethylene. Increased acetylene concentrations of 2.0 ml litre‐1 gave a similar response to 1.0 ml litre‐1, although in some instances there were indications of inhibitory effects.
The effect of temperature on the rate of sprout growth and development within stored onion bulbs
Authors: BREWSTER J. L.
Published: February 2008

In order to understand better the effects of storage temperature on the time to visible sprouting in stored onions, sprout growth was measured by regularly dissecting samples from bulbs stored at 1, 10, 15 or 25°C for 243 days. The dry‐weight of the shoot or sprout within stored onion bulbs increased exponentially with time. The rate of increase of sprout dry weight, as well as the rate of leaf initiation by the shoot apex was faster at 17° than at 10 or 25°C, and almost zero at 1°C. The rate of loss of dry weight from storage tissue was similar at 17°C and 25°C but slower at 10°C and slower still at 1°C.
Dangers in testing statistical hypotheses
Authors: COUSENS ROGER , MARSHALL CHARLES
Published: February 2008

Most experiments are intended for the estimation of the size of effects rather than for the testing of a hypothesis of whether or not an effect occurs. Hypothesis testing is often inapplicable, is over‐used and is likely to lead to misinterpretations of results. The two types of error possible in hypothesis testing are discussed. Whereas Type I error is usually examined as a matter of course, Type II error is almost always ignored. Investigations in which zero differences are important should recognise the possibility of Type II error in their interpretation. A nonsignificant result should not be interpreted as evidence of a lack of effect. Statistical significance is not synonymous with economic or scientific importance. The importance of choosing the most appropriate design is emphasised and some suggestions are made as to how important sources of error can be avoided.
Field screening for resistance to barley net blotch
Authors: SKOU J. P. , HAAHR V.
Published: February 2008

Inoculation with barley net blotch from infested straw debris was compared with that from diseased plants after sowing infected grains. The straw debris had a high, uniform inoculation potential which gave an early, continuing infection and easily reproducible results that were effective for screening barley cultivars in the field for resistance against a natural population of the pathogen. Further, it minimises an eventual influence from other leaf pathogens coming from the surroundings.

Irrigation was decisive for the success of the method ‐ especially in the initial phase. Ten m separation with an immune crop was insufficient to completely prevent infection in the uninoculated plots.

The tested 25 cvs were differentiated in six categories of resistant and susceptible on the basis of disease development and final level of attack. None of them was free of symptoms. The most resistant cvs kept a constant, low level of attack during the whole growing season, whereas the most susceptible cvs showed an early and rapidly increasing attack. Intermediate cvs were characterised with more or less slow increase of the attack. The size and proportion of the brown necrotic spots and the surrounding yellow halo varied greatly from one cultivar to the other.

The grain yield reduction was due solely to an effect on the thousand grain weight which decreased linearly with the squared point score for net blotch. Further, the disease affected the quality of the grains as less nitrogen was transported from straw to grain in the severely diseased plants.
The importance of understanding host plant phenology in the biological control of Acacia longifolia*
Authors: DENNILL G. B.
Published: February 2008

In order to assess the effect of an introduced gall wasp on the weed Acacia longifolia, it was necessary to study the vegetative growth and reproductive potential of uninfested trees. The growth of branches on uninfested trees was studied over one year. The results yielded a growth phenology which is notably different from the growth phenology of A. longifolia described by Milton (1980). Milton (1980) observed no flushing, but a gradual increase and decline in growth during spring and late summer, respectively. The present study showed distinct flushing, and a marked lack of growth during spring. Examination of the effect of reproduction on the vegetative growth of A. longifolia explains the disparity. A. longifolia reproduces during spring. Comparison of phyllode addition during spring with pod production for three successive years at one site, and for two years at another, shows that phyllode addition is low during years of high pod production, and vice versa. Between trees, phyllode addition is also inversely related to pod production within a reproductive season. Because the present growth phenology was done in a year of high pod production, growth during spring was negligible, in contrast with Milton's (1980) phenology which was done in a year of low pod production and high phyllode addition. Depending on the year in which the plant was studied, its reproductive potential and vegetative growth could have been under‐ or overestimated by as much as 62% and 90%, respectively. This study shows that the phenology of weeds with an annual cycle needs to be examined for at least two years in order not to under‐ or overestimate their reproductive or growth potential. This is especially important when assessing the efficacy of biological control agents.
Effects of osmotic priming and ageing on the germination and emergence of carrot and leek seed
Authors: DEARMAN JANE , BROCKLEHURST P. A. , DREW R. L. K.
Published: February 2008

Carrot and leek seed was osmotically primed in polyethylene glycol solution (273 g/kg water and 342 g/kg water respectively) for 10, 14 or 17 days before accelerated ageing for 0, 24, 48, 72 or 96 h. Priming reduced the germination time compared with non‐primed seed. Accelerated ageing increased germination and emergence times and decreased percentage germination and emergence to a greater extent for the primed seeds than for non‐primed seeds in both species.

Primed and dried but non‐aged seed from both species was stored at 10°C for 12 months. There was no loss of viability and improvements in germination time due to priming were maintained throughout the storage period for all the priming treatments in leek, and for the 10 and 14 day priming treatments in carrot. Carrot seed primed for 17 days lost some viability after 12 months storage compared with non‐stored seed.
Measurement of fluorescence intensity in microscope preparations using a photodiode detector
Authors: COLE ROSEMARY A. , MORGAN A. , LANCASHIRE B.
Published: February 2008

The development of a photodiode detector to measure fluorescence intensity in biological samples is described and the circuit is given for the amplication of the signal.
Virus content of leaves of cassava infected by African cassava mosaic virus
Authors: FARGETTE D. , THOUVENEL J‐C. , FAUQUET C.
Published: February 2008

African cassava mosaic virus (ACMV) was detected in cassava leaves by ELISA. Some normal constituents of cassava leaves interfered with virus detection but leaf extracts of Nicotiana benthamiana did not. The symptom pattern was determined early in the growth of a leaf and subsequently changed little. ACMV was found only in the yellow or yellow green areas of the mosaic pattern. Virus content of the leaves increased with increasing symptom intensity, but decreased with leaf age and ACMV was not detected in mature leaves. Most whiteflies were found on young growing cassava leaves and the number decreased progressively with leaf age. This distribution will aid both the acquisition and inoculation of the virus.
Studies on watercress chlorotic leaf spot virus and on the control of the fungus vector (Spongospora subterranea) with zinc
Authors: TOMLINSON J. A. , HUNT J.
Published: February 2008

Watercress chlorotic leaf spot virus (WCLV) caused a yellow leaf spot disease of watercress at Pickering, Yorkshire. The virus was mechanically transmitted to and maintained in Chenopodium quinoa, C. amaranticolor and Petunia hybrida in which it caused systemic symptoms. It could not be mechanically transmitted, however, from infected C. quinoa to Chrysanthemum, Gynura aurantia, potato, tomato, watercress or nine other species of Cruciferae.

WCLV could be partially‐purified after extraction in weak (0.05–0.1 M) but not strong (0.5 M) phosphate or tris/HCl buffer after clarification with diethyl ether and acidification to pH 3.9–4.0. Preparations were non‐infective if treated with 5% (vlv) ethanol or n‐butanol or if stored at — 12°C for 1 day or heated for 10 min at 54°C. Preparations were non‐infective after treatment with RNase or proteinase K but not after treatment with DNase.

The virus was present in roots of diseased watercress plants which also contained the watercress crook root disease fungus Spongospora subterranea f. sp. nasturtii. Tests showed that WCLV was transmitted by S. subterranea zoospores and that it persisted in the resting spores of the fungus.

The crook root disease was controlled by adding 0.3–0.5 μg Zn/ml to the inlet water supply to the crop. The water that had flowed through the crop contained 0.05–0.10 μg Zn/ml. Although this increased the zinc content of the watercress from 8–9 in untreated beds to 16–48 μg Zn/g in treated beds, this was below the tolerance recommended by the Food Standards Committee.

A method is described of obtaining accurate dilutions of solutions of zinc sulphate (20% w/v ZnSO4.H2O) in the water supplying the crop using solutions of the red dye Ariavit Amaranth.
Storage of samples infected with lettuce or cucumber mosaic viruses prior to testing by ELISA
Authors: WARD C. M. , WALKEY D. G. A. , PHELPS KATHLEEN
Published: February 2008

Methods of processing and storing lettuce mosaic and cucumber mosaic virus infected tissues prior to ELISA have been examined. Virus antigen detection was highest in samples homogenised in phosphate inoculation buffer (1% K2HPO4, 0.1% Na2SO3) and stored at either — 20°C or — 196°C. Detection was poor in samples homogenised in phosphate buffered saline prior to storage and in samples of all treatments stored at 4°C. Freeze‐dried leaf segments retained a high concentration of antigen, as did freeze‐dried homogenates of samples prepared in inoculation buffer.

Higher levels of antigen were detected in samples stored as whole leaves at 4°C for 24 h before processing, than in samples stored as leaf segments during this period.
Partial purification of hatching activity for Globodera rostochiensis from potato root diffusate
Authors: ATKINSON H. J. , FOWLER M. , ISAAC R. E.
Published: February 2008

The potential of several chromatographic methods for isolating hatching factors for potato cyst nematodes from potato root diffusate was investigated using a bioassay based on emergence of juveniles from cysts. Gel filtration provided an overall estimate of molecular weight of 437 Da for the hatching activity and ion exchange chromatography indicated that at least 60% of the recovered activity was anionic in nature.

Material less polar than the hatching activity could be removed by passing potato root diffusate through a reversed‐phase Sep‐Pak C18 cartridge and the elutant showed 83.3 ± 4.4% (mean of 32 cysts) of the initial hatching activity. High performance liquid chromatography (HPLC) with a reversed phase, C18 column and gradient elution (0–80% CH3OH in water) confirmed that much of the hatching activity was polar and that it was not retained by this method of separation. A weak anion exchange resin achieved slight retention of much of the hatching activity and an ion pairing reagent lowered the polarity sufficiently to allow some retention in subsequent reversed phase HPLC on a CIS column. Both ion exchange and ion pairing HPLC suggested that hatching activity was not chromatographed as a single compound and indicated that fractions able to influence the nucleolus of the nucleus within the dorsal pharyngeal gland cell did not always show hatching activity.
Inhibition of degreening in the peel of bananas ripened at tropical temperatures
Authors: SEYMOUR G. B. , JOHN P. , THOMPSON A. K.
Published: February 2008

An investigation was undertaken to examine the roles of ethylene, oxygen and carbon dioxide in the failure of bananas to degreen at high temperature. Also a comparison was made of the response of bananas and plantains to storage at high temperature.

Bananas produced more ethylene at temperatures where they failed to degreen than at those where they turned fully yellow, and supplying high levels of exogenous ethylene to bananas ripening at high temperature did not induce the development of a yellow peel. Isolated peel tissue held, in the presence of ethylene, at 20 or 35°C failed to develop a yellow colouration at 35°C in air or 80% oxygen, while all detached peel tissue held at 20°C degreened. However, when atmospheres were enriched with carbon dioxide degreening of detached peel was suppressed at both 20 and 35°C. In contrast to bananas, plantain fruit degreened more rapidly at 35°C than at 20°C. The way in which high temperatures may inhibit degreening in bananas is discussed.
The importance of technique in establishing biocontrol agents — the moth Carposina autologa on Hakea sericea
Authors: DENNILL G. B.
Published: February 2008

The seed attacking moth Carposina autologa was released in South Africa for control of the weed Hakea sericea but established poorly. Altering the release method such that it corresponded more closely to natural infestation and better training and supervision of field workers resulted in a 111 % increase in success of a subsequent release.
Some continuing uncertainties in knowledge of herbicide behaviour in the soil
Authors: HANCE R. J.
Published: February 2008

Recent developments concerned with the variability in the performance of soil‐ applied herbicides are reviewed with particular reference to phytotoxicity and to factors controlling persistence. It remains questionable that measurements of adsorption and herbicide concentration in the soil solution can adequately predict the phytoxicity of a herbicide in the soil. This is because such an approach ignores the spatial distribution of the herbicide and the parts of the plant through which a herbicide can be taken up. It also ignores the influence of climatic factors on persistence, uptake and plant response. In a general way persistence and the factors which control it are understood but detailed, reliable, quantitative analyses of the phenomena are not yet available. Much remains to be done before the interactions of the soil microflora with its environment and consequent effects on herbicides can be defined. There are still opportunities to improve the precision of use of soil‐applied herbicides based on better comprehension of the processes involved in the expression and duration of phytotoxicity.
Host ranges, symptoms and amino acid compositions of eight potexviruses
Authors: SHORT MARGARET N. , DAVIES JEFFREY W.
Published: February 2008

The host ranges, symptom expression and coat protein compositions of eight definitive potexviruses are described and compared. Only limited host range similarity was observed: clover yellow mosaic virus and white clover mosaic virus shared 11 of the 28 host species tested; foxtail mosaic virus and narcissus mosaic virus infected monocotyledons; barrel cactus virus and viola mottle virus had narrow host ranges but had eight of the host species in common. Amino acid analyses of coat proteins showed some similarity among the viruses tested, but little correlation with the different host range types. There was more variation of structurally important amino acids such as lysine, arginine, leucine and proline than might have been expected, but high alanine and low tyrosine, tryptophan, cysteine and methionine were typical of plant virus coat proteins.
The use of water traps for cranefly monitoring: an assessment of operator efficiency
Authors: BLACKSHAW R. P.
Published: February 2008

SUMMARY

Unskilled operators used water traps to monitor cranefly populations in 48 grassland sites in the summer of 1984. For each trap operated the numbers of males and females were recorded and these counts were checked in the laboratory to give estimates of operator error. Operators also recorded the amount of time they spent implementing the scheme. The probability of reporting a correct count for male craneflies was 0.796 and for females 0.846. There was a greater tendency for the male counts to be under‐rather than overestimated, and vice versa for females. Generally, the number of errors made was not related to either the number of craneflies taken or the rate at which they were sorted. Average times were calculated for different aspects of the monitoring system: 37 min for setting up four water traps; 40 min per field per week for servicing traps excluding handling craneflies; 18 flies/min sorting rate. Overall, the mean time spent implementing the scheme in one field was 209 min. It was concluded that operator error can be as important as predictive error in the implementation of a forecasting scheme and that it cannot be assumed that any monitoring system operates with complete accuracy.