bluuebunny/crossref_metadata_2025 huggingface dataset:
Concentration of virus and ultrastructural changes in oats at various stages of barley yellow dwarf virus infection
Authors: EWEIDA M. , OXELFELT P. , TOMENIUS K.
Published: February 2008

Enzyme‐linked immunosorbent assay was used to monitor the concentration of barley yellow dwarf virus (BYDV) in roots and leaves of oats inoculated at the 1 ‐ 2 leaf stage and at the 4 ‐ 5 leaf stage, respectively. Virus was detectable 20 h after inoculation in the roots and after 48 h in the leaves of plants inoculated at the 1 ‐ 2 leaf stage. The virus concentration reached a plateau in the roots after 7–8 days, and was 3–4 times higher than in the leaves. In plants inoculated at the 4 ‐ 5 leaf stage virus was detectable in roots and leaves after 3 and 5 days, respectively. The concentration reached a maximum after 10 days in the roots and after 18 days in the leaves; the concentration in the leaves was 2–3 times higher than in the roots.

Virus was readily detectable in seeds from infected plants, both fresh and old dried seeds. However, seed transmission could not be demonstrated.

Virus‐like particles were first observed in phloem cells of roots 4 days after inoculation, but no ultrastructural changes were detected at this stage. After 5–6 days, disintegrated nuclei and virus‐induced vesicles were observed in many cells and abnormal production of callose was found after 10 days. Necrotic phloem cells were observed from day 13, shortly after the appearance of external symptoms.
Methods and strategies for detecting Solanum tuberosum dihaploids in interspecific crosses with S. phureja
Authors: CALIGARI P. D. S. , POWELL W. , LIDDELL K. , MAINE M. J. DE , SWAN G. E. L.
Published: February 2008

The frequency of dihaploid production following the interspecific pollination of Solanum tuberosum clones with Solanum phureja has been investigated. Seventeen hybrid combinations were tested and the crosses differed significantly in the number of seed produced, the proportions that were viable and the proportions that were dihaploid. The overall frequency of dihaploid production was 62%. The dominant embryo spot marker of the pollinator (IVP 48) in conjunction with seed diameter was used to classify the seed samples. Number of days taken to germinate was also recorded. It was therefore possible to examine retrospectively the effect of selecting sub‐sets of the seed based on the presence or absence of the embryo spot, seed size and germination time. A seed selection system based on the absence of the embryo spot in conjunction with seed greater than 1.25 mm in diameter resulted in 93.6% of the potential dihaploids being identified.
The fate of Datura ferox seeds in the soil as affected by cultivation, depth of burial and degree of maturity
Authors: BALLARÉ C. L. , SCOPEL L. , GHERSA C. M. , SÁNCHEZ R. A.
Published: February 2008

Seeds of Datura ferox were collected in soybean fields, grouped into four categories according to the degree of fruit maturity and placed just level with the soil surface or buried to a depth of 7 or 15 cm. Seed survival after 8 months was c. 30% when the seeds were left on the soil surface, but between 40 and 90% when the seeds were buried. The riper seeds were the more persistent. A similar pattern was observed after 20 months. Seedling emergence was negatively related with the degree of seed maturity and depth of burial, but it was never great enough to explain seed losses.

In another experiment seeds from ripe capsules were superficially sown and the soil was: (0) left undisturbed, (1) cultivated in late winter or (2) cultivated in late winter and late spring. In all cases there was a small flush of seedlings at the beginning of the first spring; other flushes occurred only after soil cultivation and were larger during the second spring than during the first. In the plots cultivated twice a year (2) the seedlings that emerged in the first spring represented c. 4% of the initial seed bank. Survival after 20 months was about 25% in all treatments. In an arable field under soybean cropping the seedling flushes during the spring months were related to the pattern of soil cultivation. The seedlings that emerged after crop drilling represented c. 18% of the seed bank (estimated before drilling). Implications for weed management are discussed.
The effects of soil conditions, soil sterilisation and seed treatmen on the emergence of cabbage in controlled temperature cabinets and the field
Authors: WHITE J. G.
Published: February 2008

Previous cropping history of the soil and the changes that occurred in soil moisture content and temperature were the major factors determining the emergence of cabbage seedlings from pathogen‐free seeds. Seedling losses caused by soil‐borne pathogens could be high but these losses were prevented by seed treatment with metalaxyl or soil sterilisation with methyl bromide prior to sowing. The beneficial effects of metalaxyl and methyl bromide treatments were confirmed in field experiments involving repeated sowings of cabbage seeds.

In experiments with sterilised soil and cabbage seed infected with Alternaria brassicicola emergence at – 0·2 bars soil moisture potential was reduced by 7·8–23.5% at 5, 10, 20, and 25°C. In the field, losses due to A. brassicicola were greatest when the soil became capped after sowing.

The results show that recently developed fungicides may facilitate emergence under conditions extremely favourable for seed‐ and soil‐borne pathogens. For maximum benefit, selection of seed treatments should be based on knowledge of the range of pathogens likely to reduce emergence.
Time of sowing and temperature effects on the flowering of Stylosanthes guianensis
Authors: TRONGKONGSIN K. , HUMPHREYS L. R.
Published: February 2008

Seedlings of Stylosanthes guianensis var. guianensis cv. Cook and of two selections of S. guianensis var. pauciflora (CIAT 1280 and CIAT 1062) were grown at day/night temperatures of 20°/25°, 30°/25°, and 35°/30°C in a naturally‐lit glasshouse at latitude 27°30'S. Sowings were made in decreasing daylength at 30‐day intervals from 22 January to 21 May.

Cv. Cook and the CIAT 1280 selection did not flower fully if sown after 22 January and the CIAT 1062 selection did not flower if sown after 22 March. This is interpreted as a long‐short day flowering response. Usually, flowers were initiated earlier and at a lower node at 25†/20°C than at the warmer temperatures. At 25†/20°C the first flowers to appear were produced predominantly at the terminal apex of the main stem in cv. Cook and the CIAT 1062 selection, but not in the CIAT 1280 selection. At the two warmer temperatures first flowers were more commonly produced at the terminal apex of primary, secondary and tertiary branches. There were more inflorescences per plant on earlier than later sown plants when measured 21 days from appearance of the first flower and the most inflorescences were produced by cv. Cook at 25†/20°C, by selection CIAT 1062 at 30°/25°C, and by CIAT 1280 at 35°/30°C.
Purification and particle properties of groundnut rosette assistor virus and production of a specific antiserum*
Authors: RAJESHWARI R. , MURANT A. F.
Published: February 2008

Purified preparations of the luteovirus, groundnut rosette assistor virus (GRAV), were made by treatment of groundnut leaf extracts with cellulase, followed by sucrose density gradient centrifugation. Yields of virus particles were about 0·5‐1·0 mg/kg leaf material. The preparations contained isometric particles c. 28 nm in diameter with a sedimentation coefficient (s20, w) of 115 S, a buoyant density in Cs2SO4 of 1·34 g/cm3, and A260/A280 of 1·86. The particles contained a single species of nucleic acid (presumably RNA), of mol. wt 2·09 × 106and with no detectable polyadenylate sequence, and a single protein species, of mol. wt 24 × 103. An antiserum produced in a rabbit had a titre of 1/256 in gel diffusion tests and detected GRAV in leaf extracts by ELISA. GRAV particles reacted in F(ab')2‐ELISA and immunosorbent electron microscopy (ISEM) tests with antisera to bean leaf roll, potato leafroll and tobacco necrotic dwarf luteoviruses, but did not react with antisera to carrot red leaf luteovirus.
The effect of cherry leaf roll virus infection on the performance of birch pollen and studies on virus replication in germinating pollen
Authors: MASSALSKI THE LATE P. R. , COOPER J. I. , HELLEN C. U. T. , EDWARDS M. L.
Published: February 2008

The rates of germ tube elongation in vitro of pollen from cherry leaf roll virus (CLRV)‐infected birch (Betula pendula) did not differ significantly from those of pollen from virus‐free trees. Differences in percentage germination of pollen collected from trees at different sites were significant but percentages of germination of pollen from virus‐infected and virus‐free trees did not differ greatly from one another. In vivo, pollen from infected trees germinated on healthy and CLRV‐infected stigmas and callose plugs formed in both types of tissues.

However, the extent of callose plug formation was greater in the pollen tubes of virus‐free grains germinating in infected stigmas than in reciprocal crosses. CLRV coat antigen was detected by ELISA in stigmatic tissue, from healthy trees, on which virus‐carrying pollen grains had germinated.

Using fluorescein isothiocyanate conjugated to CLRV‐specific γ‐globulin, viral coat antigen was detected throughout germ tubes from virus‐carrying but not virus‐free pollen germinating in vitro. Protoplasts released following Driselase digestion of pollen germ tubes from virus‐infected trees contained CLRV antigen detectable by ELISA. During germination of virus‐infected pollen there was little synthesis of viral coat protein or nucleic acid but, following inoculation with purified virus particles, protoplasts made from healthy germinating pollen produced increasing amounts of CLRV‐specific antigen implying that CLRV replicated in this system.
Monoclonal antibodies to the soya bean cyst nematode, Heterodera glycines
Authors: ATKINSON H. J. , HARRIS P. D. , HALK E. J. , NOVITSKI C. , LEIGHTON‐SANDS J. , NOLAN P. , FOX P. C.
Published: February 2008

In order to identify proteinaceous secretions involved in feeding of the soya bean cyst nematode, Heterodera glycines, over 1800 monoclonal antibodies (MAbs) were raised in four experiments using extracts of second stage juveniles and adult females as the immunogens. A rapid, indirect immunofluorescent screening procedure is described that enabled the antigens for 100 MAbs/day to be localised in juveniles. A similar immunofluorescent screening procedure for adult females was less successful due to the masking of the fluorophore by autofluorescence; additional approaches, including enzyme linked immunosorbent assays (ELISA), were necessary to aid in the screening process. The immunosuppressive drug, cyclophosphamide, had an effect on the range of antibodies obtained in two experiments. One was designed to favour antibodies specific to the hatched rather than the unhatched juvenile, whereas the second aimed to select those for the anterior rather than the posterior part of the adult female.

A large number of MAbs showed well defined specificities and numbers are given in parentheses for those that recognised the following potential sites of secretion into the plant: the subventral pharyngeal glands (84), the dorsal pharyngeal gland (5), the amphidial pouches (10) and the excretory system (15). These MAbs will aid further work to define the role of nematode secretions in host invasion and the feeding process of this cyst nematode.
Biocontrol of British bracken: the potential of two moths from Southern Africa
Authors: LAWTON J. H. , RASHBROOK V. K. , COMPTON S. G.
Published: February 2008

The spread of bracken is a major problem in upland areas of Britain. We have investigated biological methods as an alterative to traditional forms of weed control. Details are given of the life histories of two potential candidates for introduction as biocontrol agents, the Southern African mothsConservula cinisignaandPanotimasp. nearangularis.Results indicate that these species are highly host specific and potentially very destructive to bracken.
Nitrate concentration and nitrate reductase activity in the leaves of three legumes and three cereals*
Authors: NAMBIAR P. T. C. , REGO T. J. , RAO B. SRINIVASA
Published: February 2008

Nitrate concentration and nitrate reductase activity (NRA) were studied in the leaves of soybean (Glycine max), groundnut (Arachis hypogaea and cowpea (Vigna unguiculata) and sorghum (Sorghum bicolor), pearl millet (Pennisetum americanum) and maize (Zea mays) at three nitrogen fertiliser levels in two field experiments.

Higher nitrate concentrations were detected in the leaves of groundnut, cowpea and pearl millet than in sorghum and maize. Nitrate content in the leaves and leaf NRA were not related across crop species, nor was a generalised pattern of leaf NRA and leaf nitrate observed within legumes or within cereals. Nitrogen application resulted in higher nitrate availability in the leaves, with varied leaf NRA.
The germination and emergence of seeds of winter oilseed rape stored and sown in admixture with pelleted methiocarb
Authors: ELLIS R. H. , DOLMAN G. F. S.
Published: February 2008

The possibility that pellets of the molluscicide Draza (a.i. methiocarb) might reduce field emergence of seeds of winter oilseed rape (Brassica napus, cv. Jet Neuf) when sown admixed, laboratory germination when stored admixed, or field emergence when both stored and sown admixed was the subject of three separate investigations. Admixture at sowing did not influence the emergence of five seed lots (P > 0·05). Neither did admixture influence loss in germination or change in moisture content during 2 months' storage of one lot in four different regimes (P > 0·05). Field emergence following 2 months' storage in paper bags was not influenced by admixture (P > 0·05), whereas a 12% reduction in field emergence resulting from storage in admixture within polyethylene bags was detected (P < 0·05). Thus short‐term storage within paper sacks of winter oilseed rape seeds in admixture with slug pellets containing methiocarb did not damage the seeds. The emergence of five seed lots differed considerably within and between field sowings. Tentative advice on the calculation of sowing rates for different seed lots of winter oilseed rape is provided to account for this variation.
Variation in growth of overwintered stolons of contrasting white clover populations in response to temperature, photoperiod and spring environment
Authors: EAGLES C. F. , OTHMAN O. B.
Published: February 2008

The response of overwintered stolons of nine contrasting white clover populations to temperature, photoperiod and natural conditions was studied in six environments during the spring. Rate of leaf appearance, leaflet length, petiole length, stolon internode length, dry matter distribution within the plant and total dry weight were measured on 15 plants of each population/environment combination.

Most characters, except leaf size and proportion of dry matter allocated to leaf, responded positively to temperature in the range 10 – 20°C. A positive effect of photoperiod extension was also found for all characters except rate of leaf appearance, internode length and distribution of dry matter to leaf.

Population differences in response to environment were found which were related to both leaf size classification and origin.

Stolon dry weight was positively correlated with leaf length, petiole length and stolon internode length in most environments. The relationships between the eight characters were often complex and canonical variate analysis provided a convenient way to discriminate between the populations based on all eight characters.
Growth, light interception and disease in field bean (Vicia faba): the effect of late infection by Ascochyta fabae
Authors: MADEIRA ANA C. , CLARK J. A. , ROSSALL S.
Published: February 2008

Growth and light interception were measured in field beans (Vicia faba) infected by Ascochyta fabae under field conditions. Despite late infection, disease reduced the leaf area index and the dry matter production of the crop. The main effect was due to a decrease of leaf area duration, which resulted in shorter duration of growth and lower final dry weights. The reduction in seed yield was significant, representing a decrease of 15% compared with a prophylactic fungicide treatment. The data are consistent with a small reduction in light use efficiency, but the observed differences were not significant during the period of crop growth.
The effect of tiller removal and tiller defoliation on competition between the main shoot and tillers of spring barley
Authors: GU J. , MARSHALL C.
Published: February 2008

In glasshouse and field experiments the source‐sink relations of the main shoot of plants of spring barley were modified by tiller removal and tiller defoliation. Decreasing competition by tiller removal promoted the growth of the residual main shoot and its component parts, and the earlier tillers were removed the greater was the effect. Stem dry weight was increased four‐fold in the glasshouse by early tiller removal and was doubled in the field experiment. The grain yield of the main shoot ear was increased by 26 – 30% by tiller removal compared with tillering control plants and this was due to larger grains in all spikelet positions. On the other hand increasing competition by regular tiller defoliation had relatively little effect on the growth and development of the main shoot in the glasshouse study, but in the field the main shoot grain yield was reduced by 10% compared with the control. The main effect of tiller defoliation was on the development of tillers. In the glasshouse tillers survived repeated defoliation, continued to be produced, and the majority produced grain but with fewer and smaller grains per ear than in control plants. Tiller growth was supported by the import of assimilate from the main shoot and this was accompanied by an increase in the photosynthetic rate of the main shoot leaves. In the field all defoliated tillers died within 4 wk. These responses are discussed in terms of the physiological interrelations between the main shoot and tillers.
Serological comparison of an Australian isolate of capsicum mosaic virus with capsicum tobamovirus isolates from Europe and America
Authors: PARES R. D.
Published: February 2008

A New South Wales isolate (Ca) of capsicum mosaic virus was tested against antisera to it and capsicum tobamovirus isolates from the Netherlands (P8, P11), USA (SL), Argentina (FO) and Sicily (PM). The comparison demonstrated that the four viruses Ca, P8, PM and SL are closely related to each other, forming a series of decreasing relationship to Ca in the above order. FO was related to these but insufficiently to be considered part of the group, and P11 was only slightly related to the others. The literature on serology of tobamoviruses in Capsicum spp. was collated and it is suggested that isolates from Sicily (pepper mild mottle), Australia (capsicum mosaic), The Netherlands (P8, P14) and USA (SL) be considered as strains of a virus distinct from both tobacco mosaic and tomato mosaic viruses and that these isolates all be referred to in future as strains of pepper mild mottle virus.
Alfalfa mosaic virus isolates from lucerne in South Australia: biological variability and antigenic similarity
Authors: HAJIMORAD M. R. , FRANCKI R. I. B.
Published: February 2008

Alfalfa mosaic virus (AMV) was isolated from lucerne (Medicago sativa) plants with a variety of disease symptoms in eight of 13 sites in South Australia indicating that the virus is widespread in the state. The host ranges and symptomatology of the virus isolates varied considerably. Twelve selected local lesion isolates were shown to be distinct when mechanically inoculated to a range of plant species and cultivars. However, agar‐gel diffusion and enzyme‐linked immunoassay tests with polyclonal antisera prepared against glutaraldehyde‐fixed virus preparations of the five most readily distinguishable AMV isolates, failed to reveal significant antigenic differences between the 12 virus isolates. This indicates that serological tests with polyclonal antisera can detect a wide range of AMV variants but would be unlikely to differentiate between strains. The wide host range and variability of AMV precluded the grouping of isolates into strains of the virus.
Use of the cell wall‐less alga Dunaliella bioculata in herbicide screening tests
Authors: FELIX H. R. , CHOLLET R. , HARR J.
Published: February 2008

An assay was developed using Dunaliella bioculata, a cell wall‐less, unicellular alga with two flagella, to determine whether it could supplement a programme of herbicide screening. Growth was monitored by measuring the optical density of the culture. Additional information was obtained by microscopic examination; lysis of cells, loss of flagella, immobilisation, and bleaching could be readily seen. Comparing 24 commercial herbicides with an untreated check, 20 compounds clearly affected D. bioculata. The assay with D. bioculata can be used as a primary indicator of mode of action; as an example, all members of the chemical class of dinitroanilines affected movement and shape of D. bioculata, probably by influencing microtubule structure.
Pre‐harvest retting of flax: effects of water stress on uptake and efficacy of glyphosate
Authors: HARVEY B. M. R. , CROTHERS S. H.
Published: February 2008

The effects of water stress on the uptake, translocation and efficacy of glyphosate in flax were investigated in relation to pre‐harvest retting.

Glyphosate (applied at a rate equivalent to 1.44 kg a.e. ha‐1 at 0, 10, 20 or 30 days after the start of flowering) caused little desiccation of flax grown in pots under restricted watering. Glyphosate application to well‐watered plants caused the moisture content to decline from an initial value of 70 – 80% to approximately 40% at 3 wk after spraying.

Glyphosate was applied 2 wk after the mid‐point of flowering to flax grown in soil with moisture contents of 35, 31, 26, 22, 16 or 12%. Soil moisture levels (16% and 12%) which restricted evapotranspiration also reduced the efficacy of glyphosate but did not affect uptake of 14C‐glyphosate. Translocation of 14C‐glyphosate out of treated leaves was reduced only in the most severely stressed plants (12% soil moisture). Experiments with young plants (4 wk old) confirmed that water stress slightly reduced downward translocation of glyphosate.

When the herbicide was applied to young plants under conditions which minimised differences in translocation, 10.8 μg glyphosate was sufficient to desiccate unstressed plants but 108 μg had little effect on stressed plants. This indicates that, in addition to any reduction in translocation which occurs during drought, water stress may reduce the susceptibility of flax to glyphosate. Thus only relief of plant water stress by irrigation is likely to improve response of the flax crop to glyphosate.
Harvesting and bedding practices in relation to grey mould of strawberries
Authors: SUTTON J. C. , JAMES T. D. W. , DALE A.
Published: February 2008

Relationships of cultural and harvesting practices in strawberries to epidemics of grey mould, caused by Botrytis cinerea, were examined in field plots in 1983 ‐ 84 and 1984 ‐ 85. The strawberries were grown in matted rows or solid beds and harvested by hand or by machine. Foliage cut by the machine was removed by hand‐raking. Potential sporulation of B. cinerea on dead strawberry leaves, the principal inoculum source, was estimated by quantifying sporulation on samples of the leaves incubated in humidity chambers.

During May, the incidence and density of sporulation, and total spore production per unit area of strawberry bed, usually were lower in plots harvested by machine in the preceding year than in those harvested by hand. Machine harvesting in the preceding year also suppressed incidence of grey mould on the fruits in June. Potential sporulation on dead leaves was usually less in solid beds than in matted rows in 1984 but not in 1985. Bed type usually did not affect incidence of grey mould fruit rot. No relationship was found between dry weights of dead leaves from sampling quadrats and potential sporulation on the leaves. It was postulated that the long‐term impact of machine harvesting on grey mould epidemics was related to removal of the majority of the foliage and berries from the plots during harvesting operations.
The prevalence of pathogens in honey bee (Apis mellifera) colonies infested with the parasitic mite Varroa jacobsoni
Authors: BALL B. V. , ALLEN M. F.
Published: February 2008

The prevalence of nine honey bee viruses in samples of dead adult bees from Apis mellifera colonies in the Netherlands and Germany infested with the parasitic mite Varroa jacobsoni was compared with virus incidence in uninfested colonies in Britain. In colonies with low mite populations the viruses present and their incidence during the year were similar to the results obtained from British colonies. However, in marked contrast with findings in Britain, acute paralysis virus (APV) was the primary cause of adult bee mortality in German honey bee colonies severely infested with V. jacobsoni. Dead brood from unsealed and sealed infested cells from German colonies with high mite populations also contained much APV.

The evidence suggests that V. jacobsoni activates APV replication in adult bees by its feeding behaviour and transmits virus from adult honey bees to pupae. In addition, adult bees, in which APV is multiplying, transmit the virus to unsealed brood in the larval food.
The serological relationships and some other properties of isolates of broad bean wilt virus from faba bean and pea in China
Authors: XU Z. G. , COCKBAIN A. J. , WOODS R. D. , GOVIER D. A.
Published: February 2008

An isolate (N15) of broad bean wilt virus (BB W V) from faba bean in China was compared with some other isolates and strains including the nasturtium ringspot strain (NRSV, BBWV serotype I), parsley virus 3 (PV3, serotype I) and BBWV isolate PV131 (serotype II).

In host range studies, N15 infected 12 of 14 species, including soybean and spinach. It was purified from Chenopodium quinoa and pea by a method that yielded up to 8mg/100g tissue. By the same method, NRSV yielded up to 4mg/100 g. Purified preparations of N15 and NRSV contained isometric particles c. 26 nm in diameter which sedimented as three components, N15 at 62, 93 and 117 S, and NRSV at 60, 91 and 116 S.

In immunodiffusion tests using antisera to N15 and NRSV, N15 was distinguishable from NRSV but indistinguishable from PV131. In ISEM tests, many more particles of N15 and NRSV were trapped by homologous than by heterologous antiserum; in decoration tests, much antibody attached to homologous particles but none to heterologous particles. In DAS ELISA using N15 antiserum, N15 and six other Chinese faba bean or pea isolates, and a Chinese spinach isolate, were readily detected and were indistinguishable from each other and from PV131; unlike NRSV and PV3, none of the Chinese isolates, nor PV131, was detected using NRSV antiserum. These results indicate that the Chinese isolates belong to BBWV serotype II group.
Inheritance of insensitivity to tobacco rattle virus in potatoes
Authors: DALE M. F. B. , SOLOMON R. M.
Published: February 2008

The sensitivity of 20 genotypes from each of 13 progenies of parental potato clones was assessed using recently developed glasshouse testing procedures. Significant heritable differences between the progenies with respect to their degree of sensitivity to TRV were observed. Significant general and specific combining abilities were also demonstrated. The results are discussed in relation to modes of inheritance of this trait. The results indicate that though a major gene for TRV insensitivity may be operating this does not explain all the observed variation and it is suggested that there is also a system inherited in a polygenic manner that can confer good levels of insensitivity to TRV.
Effects of combining priming and plant growth regulator treatments on the synchronisation of carrot seed germination
Authors: PILL W. G. , FINCH‐SAVAGE W. E.
Published: February 2008

Osmotic priming of carrot seeds for 2 wk in polyethylene glycol (PEG, — 10 MPa) at 15 °C led to more rapid and synchronous germination at 20 °C compared to untreated seeds. These responses were enhanced by a 24 h pre‐priming soak in water or a change of solution after the first 24 h of priming to remove leachate. The inclusion of 200 mg litre‐1N‐substituted phthalimide in the pre‐priming soak and/or in the PEG further enhanced the results of priming. Leachate removal combined with phthalimide inclusion gave 79% and 86% germination from seeds of two carrot cultivars during the first day in 20°C water following priming. In contrast, cumulative germination of untreated seeds of the same cultivars was 18% and 61% respectively after 3 days in 20°C water. Seeds primed in PEG containing 200 mg phthalimide litre‐1with the solution replaced after the first 24 h germinated earlier and more synchronously than untreated seeds over a range of germination temperatures (5, 10, 15, or 20°C), but the effects of priming were most marked at 5°C.
A system for studying the effects of naturally‐occurring subzero temperatures on winter barley
Authors: HETHERINGTON P. R. , STEWART W. S.
Published: February 2008

Thermostatically‐controlled, electrical soil heating cables were used to examine the effects of subzero temperatures on winter barley growing in plots outdoors. Plants in plots without heating cables were exposed to naturally‐occurring subzero temperatures (unheated), while those in corresponding plots with the cables (heated) were protected from such temperatures. Measurements of soil, plant and air temperatures in heated and unheated plots showed that the system can, at least with the temperatures encountered during the measurement periods, prevent plant temperature from falling below the temperature set on the thermostat. A field experiment involving different cultivars and sowing dates showed that subzero temperatures experienced did not significantly affect individual plant grain yield or the number of fertile ears produced per plant. However, small, but statistically significant, effects of naturally‐occurring subzero temperatures were found in relation to the number of grains per ear, thousand grain weight and harvest index. The nature of these effects varied, and were dependent upon cultivar and/or sowing date. Subzero temperatures were also responsible for reducing the numbers of established plants in late‐sown plots through soil heaving. Possible uses of the soil heating cable system for temperature‐related studies in the Gramineae are discussed.
A rapid method for the prediction of germinability of French beans*
Authors: PANDEY D. K.
Published: February 2008

Sun‐dried French bean seeds, moisture content 10 ± 0·8%, aged at ambient temperature for 2 months, 1, 2, 3 and 4 yr were incubated in hot water at 58 × 1°C for 30 min. Buffering capacity of incubation water (IWBC) due to solutes leaked out into hot water was highly correlated with electrolyte leakage into single seed steep water. The IWBC was examined for its ability to predict seed quality of ageing stocks. The technique does not require any instrument. Thus it may prove useful as a rapid, simple, inexpensive and highly predictive vigour test.
The effect of powdery mildew (Erysiphe graminis f.sp. avenae) on yield, yield components and grain quality of spring oats
Authors: RODERICK H. W. , JONES I. T.
Published: February 2008

Yield components and grain quality were investigated on eight cultivars of spring oats with known differences in adult plant resistance to mildew and with different fungicide treatments. Losses in grain yield caused by mildew could be accounted for mainly by reductions in numbers of fertile panicles and thousand grain weights. The proportion of grain yield to total biomass, (harvest index) was also reduced. There were no effects of treatment on the concentration of fatty acids in the grain, the proportions of the component fatty acids, the percentage content of grain protein or the specific weights. However, correlation analysis of the data revealed that percentage protein contents and specific weights were negatively correlated with levels of mildew. There were significant genetic differences between cultivars in all of the yield and quality characteristics but no fungicide treatment/cultivar interactions.
Effects of ammonium‐N on development and infectivity of the take‐all fungus
Authors: COTTERILL P. J. , SIVASITHAMPARAM K.
Published: February 2008

Effects of applications of a mixture of ammonium sulphate and mono‐ammonium phosphate and of ammonium nitrate on the incidence of take‐all disease of wheat (caused by Gaeumannomyces graminis var. tritici) and on subsequent inoculum levels were studied in field and glasshouse experiments. In a field experiment in Western Australia, on a sandy soil at pH 5·4, nitrogen applications had no detectable effect on disease severity at anthesis, but ammonium sulphate treatment increased the number of propagules of the pathogen in the soil. In a pot experiment, in which seed was sown in the field experiment soils, disease was greater in soil from plots treated with ammonium sulphate and least in soil from the nil‐nitrogen plots, reflecting the respective inoculum levels in the field plot. However, treatment of the soils of lower inoculum with ammonium sulphate and ammonium nitrate during this pot experiment decreased disease. A second pot experiment confirmed the effectiveness of ammonium sulphate and ammonium nitrate in reducing take‐all at lower inoculum levels, and their ineffectiveness at higher inoculum levels.
Production and use of cDNA clones from arabis mosaic virus
Authors: JELKMANN W. , MAISS E. , BREYEL E. , CASPER R.
Published: February 2008

Arabis mosaic virus (AMV) genomic RNAs were converted to dsDNA and cloned into bacterial plasmids. Insert sizes of cDNA clones ranged from 0·2 to 3·2 kbp. Restriction enzyme mapping identified clones representing at least 90% of the RNA‐2 genome. A 0·9 kbp clone specific to RNA‐1 was also identified. Northern blot hybridisations of AMV RNAs with clones from either RNA‐1 or RNA‐2 showed no cross reactions. The sensitivity of virus detection in dot hybridisation was 15 pg of purified genomic RNA and 40 pg of purified virus particles. The possibility of using cDNA clones for the detection of AMV in strawberry sap was demonstrated. Two AMV dsRNAs corresponding to genomic RNAs in size were isolated from infected cucumber plants and reacted in hybridisation experiments.
Relationships among strains of bean common mosaic virus and blackeye cowpea mosaic virus ‐ members of the potyvirus group
Authors: LANA ALLAN FEMI , LOHUIS H. , BOS L. , DIJKSTRA JEANNE
Published: February 2008

In host‐range studies, bean common mosaic virus strains (BCMV‐NL1, ‐NL3 and ‐NY 15) usually induced distinct systemic symptoms in susceptible bean cultivars and latent infection in several Vigna genotypes (except NY15 which gave mosaic symptoms in the latter), while blackeye cowpea mosaic virus (B1CMV‐W) caused distinct systemic symptoms in several Vigna genotypes and only weak systemic symptoms in a few bean genotypes only. Biologically, B1CMV‐W was closest to BCMV‐NY15 and less close to ‐NL1. When using antisera to the three BCMV strains and five strains of B1CMV (including a strain originally considered cowpea aphid‐borne mosaic virus CAMV‐Mor) in SDS‐immunodiffusion and ELISA, BCMV‐NL1 and ‐NY15 were found to be closely related to each other and to BICMV‐Fla, ‐NR and ‐W, and less closely to BICMV‐Ind and ‐Mor. Serological relationships of BCMV‐NL1 and ‐NY15 to BCMV‐ NL3 were more distant, which is in line with the biological distinction of NL3 in causing temperature‐independent necrosis in bean cultivars with the necrosis gene I. PAGE analysis of coat proteins revealed that the three strains of BCMV and B1 CMV‐W have similar but non‐identical molecular masses. Although molecular hybridisation may further elucidate quantitative relationships between potyvir‐uses, variation within and among the potyviruses may continue to pose problems in their classification and identification.
Seed‐borne cucumber mosaic virus infection of narrow‐leafed lupin (Lupinus angustifolius) in Western Australia
Authors: JONES R. A. C.
Published: February 2008

In 1986 in Western Australia, cucumber mosaic virus (CMV) infection was widespread in breeders' selections of narrow‐leafed lupin (Lupinus angustifolius), and in collections of lupin cvs and wild L. angustifolius lines. When seed of some of these selections and cvs was sown, seed‐borne CMV was detected in seedlings. Infection of F1 progenies was traced to use of infected parent plants. CMV was also widespread in 25 seed crops of the new lupin cv. Wandoo but not in 42 seed crops of the new cv. Danja. When samples of the seed sown in 1986 were tested, CMV was detected in 3 ‐ 34% of seedlings of cv. Wandoo but in none of cv. Danja. Following intensive roguing of symptom‐bearing plants in the 1986 seed crop of new lupin cv. Gungurru, the level of seedling infection with CMV in seed samples after harvest was 0·1‐0·2%. CMV was detected in 6 ‐ 8%, 0·6‐5% and 0 ‐ 18% of seedlings from seed samples of established lupin cvs Chittick, Yandee and Illyarrie respectively. Highest levels of seed transmission were in seed from crops grown in high rainfall areas.

When a sample of cv. Wandoo seed was graded for size by sieving, CMV was detected in seedlings grown from seed in all grades, but the smallest grade contained the highest level of infection. When seed was collected from pods at different positions on plants in a CMV‐infected crop of cv. Illyarrie, seed from primary pods transmitted the virus to seedlings at a 3% rate, seed from first order lateral pods at 8% while seed from second and third order lateral pods transmitted at 13%. Examination of CMV‐infected lupin crops indicated that seed‐infected plants competed poorly and tended to be shaded out in dense crops but to survive in sparse crops. In 1987 during drought conditions after seeding, plant mortality was greater with seed‐infected seedlings than with healthy seedlings despite wide plant spacing.

An isolate of CMV from subterranean clover (Trifolium subterraneum) induced severer symptoms in lupins than four isolates from lupin; only the subterranean clover isolate prevented seed production. In tests at one lupin breeding site, CMV was found in 15 species of weeds and volunteer legumes. Fumaria officinalis, Stachys arvensis and volunteer lupins were most frequently infected.
Production and some characteristics of monoclonal antibodies against beet necrotic yellow vein virus
Authors: TORRANCE L. , PEAD M. T. , BUXTON G.
Published: February 2008

Four rat monoclonal antibodies (MAbs) specific for beet necrotic yellow vein virus (BNYVV) were produced. In indirect ELISA, all four MAbs reacted strongly with BNYVV infected plant leaf extracts (19 isolates from eight countries) but they did not react with beet soil‐borne virus (BSBV), an unnamed rod‐shaped soil‐borne beet virus isolate (86 ‐ 109) from Sweden or barley stripe mosaic virus (BSMV). However, two of the MAbs, MAFF 6 and MAFF 7 did not detect BNYVV in ELISA of infected sugar beet roots whereas MAbs MAFF 8 and MAFF 9 did detect virus in root extracts.

In electro‐blot immunoassay (EBIA), MAFF 6 and MAFF 7 readily detected BNYVV coat protein from leaf extracts whereas MAFF 8 and MAFF 9 reacted only weakly. None of the MAbs reacted with BSBV, 86 ‐ 109, BSMV or plum pox virus in EBIA. MAFF 6 coated BNYVV particles which were trapped from infected leaf or root sap on to electron microscope grids by polyclonal antibodies. MAFF 6 was partially purified from tissue culture supernatant fluid by cation exchange chromatography and the preparation used to coat microtitre plates and successfully trap BNYVV in ELISA of leaf sap extracts.
Levels and components of resistance to Amphorophora idaei in raspberry cultivars containing different resistance genes
Authors: BIRCH A. N. E. , JONES A. T.
Published: February 2008

Levels and components of resistance to Amphorophora idaei in raspberry cultivars containing different A. idaei resistance genes were studied under infestation tunnel, glasshouse and laboratory conditions. Each test consistently ranked raspberry cultivars, with increasing levels of resistance in the order, non‐resistant (cv. Mailing Jewel), resistant cultivars containing minor genes, major gene A1, gene A10 (red raspberry) and gene A10 (black raspberry) respectively. Resistance was expressed in three different ways; decreased alatae settling and feeding, decreased apterae settling and decreased aphid fecundity and rate of nymphal development.

Following exposure to a large population of alatae, significantly fewer aphids settled on A1, A10 and to a lesser extent, minor gene‐containing cultivars, compared to cv. Mailing Jewel. More alatae settled on the top than the bottom zone of non‐resistant, minor gene resistant and two of four A1‐containing cultivars; alatae settling was low on all zones of A10‐containing raspberries. Aphid fecundity and nymph development patterns on different cultivars and resistance classes were similar to those found for alatae settling. After 7 days reproduction more than 30% of the nymphs developed to third or fourth instar on cv. Mailing Jewel, whilst on minor gene and major gene‐containing cultivars the total number of nymphs and the proportion of later instars decreased. On resistant cultivars the nymphs were found mainly on the middle and bottom leaf zones, compared to cv. Mailing Jewel. A rapid (48 h) screening test using floating leaflets was developed and, on the basis of apterae settling, ranked cultivars reliably; it was particularly effective in distinguishing moderate and strong resistance to strain 1 A. idaei.

Gene A1‐containing cultivars bred in England were much more resistant to strain 1 A. idaei than those bred in Scotland. Possible reasons for this difference are discussed, in relation to modified screening procedures and to the control of the viruses transmitted by this aphid vector.
Field studies of leaf development and expansion in the leek (Allium porrum)
Authors: HAY R. K. M. , BROWN JANETTE R.
Published: February 2008

An analysis of leek leaf development and expansion was carried out over three seasons using field‐grown plants of three varieties which were directly sown at different dates or transplanted from controlled conditions. In all cases, successive leaves appeared (tip visible) at equal intervals of accumulated temperature. Detailed analysis of a single sowing in 1985 showed that the regularity of leaf appearance was a consequence of the coordinated response to accumulated temperature of leaf initiation (plastochron 100°C days > 0°C) and leaf blade and sheath extension. For each successive leaf, an additional 32°C days were required between initiation and appearance to allow for the linear increase in ‘sheath’ height, giving a phyllochron of 132°C days. Direct measurement of leaf extension before and after leaf appearance, and of the length of the leaf extension zone, confirmed that the rate of leaf extension, in terms of accumulated tempeature, was constant, and independent of leaf number. However, there were differences between seasons and between varieties in the responses of leaf appearance, leaf extension and ‘sheath’ length to accumulated temperature. It was concluded that the simple ontogenetic increase in leaf dimensions, which was a feature of all the crops studied, was a consequence of the progressive increase in the duration of leaf expansion.
Some characteristics of monoclonal antibodies to a British M A V‐like isolate of barley yellow dwarf virus
Authors: PEAD M. T. , TORRANCE L.
Published: February 2008

Rat monoclonal antibodies (MAbs) specific for a British F (MAV‐like) isolate of barley yellow dwarf virus (BYDV) were produced and studied. In indirect ELISA using an antiserum to BYDV‐F to trap virus from infected sap, the MAbs were shown to be specific for MAV‐like isolates of BYDV from Britain, USA and Sweden but, in this test, they did not detect PAV‐, RPV‐, SGV‐ or RMV‐ like isolates of BYDV. In similar tests using homologous antisera to trap the viruses, the MAbs did not detect BYDV‐PAV or ‐RPV or two other luteoviruses (potato leafroll and beet western yellows). One of the MAbs (MAFF 2) was partially purified from ascitic fluid, and used successfully in ELISA as a coating antibody and when conjugated to the enzyme alkaline phosphatase. Also, MAFF 2 successfully trapped BYDV‐F particles when used to coat electron microscope grids. In indirect ELISA using three MAbs (MAFF 2, MAC 91 and MAC 92) it was possible to type the three major strain groups of BYDV, viz. MAV, PAV and RPV‐like strains from Britain, USA and Europe.
Identification of an isolate of bean common mosaic virus from the Transvaal and Natal
Authors: EDINGTON B. R. , WHITLOCK V. H.
Published: February 2008

The BCMV isolates most common in the Transvaal and Natal were identified from field collected samples. The isolates belong to pathogenicity group V, to which the recessive gene bcl2confers resistance.
Characteristics of the population build‐up of the Russian wheat aphid Diuraphis noxia and the effect on wheat yield in the eastern Orange Free State
Authors: AALBERSBERG Y. K. , WESTHUIZEN M. C. VAN DER , HEWITT P. H.
Published: February 2008

Diuraphis noxia infestations were monitored in early winter and winter wheat during 1983–1985. The aphid population increase was logarithmic in all three years and on both cultivars 100 % infestation levels were recorded. The period of exponential increase in both percentage infestation and in the number of D. noxia per stem took place when the plants had reached the stem elongation stage. The mean number recorded at peak population levels was 150–160 aphids per stem. During the period of plant senescence numbers dropped rapidly. Large reductions in yield were recorded on all infested plants. Single‐plant data showed that yield reductions in the early winter cv. Betta were related to the duration of infestation. Relative to sprayed controls, reduction in kernel mass ranged from 25–80% and in 1000‐kernel mass from 15–45%. However, the yield reductions of the faster‐growing cv. Flamink, appeared to be dependent on the number of aphids per plant during the later growth stages and not the duration of infestation.
Stem canker (Rhizoctonia solani) on five early and seven maincrop potato cultivars I. Infection of shoots, stolons and tubers
Authors: HIDE G. A. , READ P. J. , FIRMAGER JANET P. , HALL SHARON M.
Published: February 2008

In 1983 and 1984, potato seed tubers of five early and seven maincrop cultivars were inoculated with cultures of Rhizoctonia soluni during planting to simulate severe seed infection. Shoot and stolon infection was assessed in June‐August and black scurf on tubers recorded after harvest in October.

Almost all shoots of all cultivars had stem canker in both years and disease on shoots, stolons and tubers was more severe in 1984 than in 1983. In 1983 similar amounts of disease developed on all early cultivars and between 11% (Ulster Sceptre) and 32% (Maris Peer) shoots were pruned off. Maris Peer had a stem canker score lower than other cultivars in 1984 but more than half the shoots were pruned off. Shoot pruning on Estima, Ulster Prince and Ulster Sceptre was more common on plants from sprouted than non‐sprouted seed. Between 30 and 50% of stolons were pruned off. After harvest in 1985, black scurf was least prevalent on Arran Comet and Maris Peer tubers and in 1984 on Arran Comet and Estima tubers from non‐sprouted seed.

Of the maincrop cultivars, King Edward plants from sprouted seed had many shoots pruned off in both years. Shoot pruning was also prevalent on Maris Piper and Pentland Squire plants from non‐sprouted seed. Record had fewest pruned shoots and stolons and the lowest stem canker score. The disease was more severe on Pentland Crown and Maris Piper plants from non‐sprouted than sprouted seed. Black scurf was most common on Cara and King Edward tubers in 1983 and on King Edward and Record tubers in 1984.

In both years few shoots but many tubers were infected on plants from non‐inoculated seed and the significance of this is discussed.