bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of nitrogen nutrition on the concentration of viruses, phospholipids and galactolipids of barley leaves infected with barley stripe mosaic virus (BSMV)
Authors: ÁDÁM A. , GÁBORJÁNYI R. , TOBIAS I. , KIRÁLY Z.
Published: February 2008

The effect of infection of barley with barley stripe mosaic virus on the chlorophyll, phospholipid and galactolipid content was examined in plants grown in sand culture with a range of nitrogen concentrations. The systemic yellowing and mosaic symptoms of infection were associated with a reduction in the chlorophyll and galactolipid content and an increase in the phospholipid content of leaves. The effects of the virus were not reversed by high nitrogen.

The effects of virus infection are interpreted as a stress‐induced phenomenon and the effects compared with those brought about by other stresses.
The interactions of potato cyst nematodes and Verticillium dahliae on early and maincrop potato cultivars
Authors: EVANS K.
Published: February 2008

The effects of potato cyst nematodes (Globodera rostochiensis and G. pallida) on the growth of early and later maturing potato cultivars, with or without the H, resistance gene, were compared in pot experiments and the effects of introducing Verticillium dahliae into the system were studied. The influence of the nematodes on root function and structural integrity was inferred from their effects on calcium and water uptake. Early maturing cultivars were less tolerant of nematode attack than later maturing ones, and those with the H1 resistance gene were more tolerant of G. rostochiensis than G. pallida. When V. dahliae was introduced, Verticillium wilt symptoms appeared much earlier on the early than the maincrop cultivars. Also, Maris Anchor (first early) died before Maris Peer (second early) and death of both when infected by nematodes and fungus was much earlier than uninfected control plants or plants infected with G. rostochiensis only. Maris Peer infected by both organisms snowed symptoms much more severe than when infected by either organism alone, whereas Maris Anchor was almost as severely affected by V. dahliae alone as both organisms together. Pentland Javelin (first early) developed Verticillium wilt symptoms several weeks later than other cultivars and the addition of nematodes failed to increase the severity of the symptoms. These differences in cultivar susceptibility to the combination of nematodes and fungus may be due to the nematodes causing different degrees of trauma in the roots of the three cultivars: measuring calcium uptake per unit water uptake showed that nematodes dramatically increase calcium uptake but that the proportional change is least in Pentland Javelin. If this is a reflection of less damage by nematodes to the endodermis of this cultivar, it may explain the greater resistance of its roots to penetration by V. dahliae.
The consequences, for malting quality, of Hordeum laevigatum as a source of mildew resistance in barley breeding
Authors: SWANSTON J. S.
Published: February 2008

Barley cultivars which include Hordeum laevigatum in their pedigree, have harder endosperms, higher β‐glucan and lower α‐amylase levels than do other cultivars of poor malting quality. Good malting cultivars are characterised by high hot water extracts, soft endosperms, low β‐glucan and high α‐amylase levels. Introgressions of exotic genes for mildew resistance, into breeding populations, may be accompanied by factors adversely affecting malting quality.
The efficiency of visual selection in early generations of a potato breeding programme
Authors: BROWN J. , CALIGARI P. D. S. , MACKAY G. R. , SWAN G. E. L.
Published: February 2008

The efficiency of visual selection in the early generations of a potato breeding programme is examined. Tubers from 571 potato genotypes were scored by four breeders after being grown, from true seed, in a glasshouse and in the field for three consecutive years. The four breeders were in good agreement as to which clones would be selected in any environment. The association between breeders was greatest when the clones were grown in plots in the field. All correlations of breeders' preferences between different environments were significantly greater than zero, but only accounted for a small percentage of the total variation. Selection in both the glasshouse and first clonal year produced a desirable response. However, such selection carried a high cost in terms of losing clones with commercial potential. Comparison of a random sample of clones with ones from the same crosses which had been selected, indicated that selection in the glasshouse and first clonal year was at best random with some suggestion, however, of a negative effect.
The repeatability of progeny means in the early generations of a potato breeding programme
Authors: BROWN J. , CALIGARI P. D. S. , MACKAY G. R.
Published: February 2008

The progenies from eight crosses between potato clones were examined. The clones were grown as seedlings in a glasshouse and subsequently from tubers in the field at two sites in two consecutive years. At harvest, all the clones were visually assessed by four breeders using a 1–9 scale of increasing desirability. Although there was a formally significant interaction between progenies and environments, the rank of the mean of a cross remained relatively consistent over different growing conditions. It is suggested, therefore, that progeny evaluation by breeders' visual preference can be used to identify the crosses with the highest potential of producing commercial cultivars.
Desiccation and storage studies on Dipterocarpm seeds
Authors: TOMPSETT P. B.
Published: February 2008

The relationship of seed moisture content (fresh weight basis) to germination, and the effect on viability of various storage conditions were examined for five species of the tropical forest tree genus Dipterocarpus. It was shown that seeds fall into two groups with regard to desiccation tolerance. Firstly, D. obtusifolius and D. turbinatus cannot be dried below about 45% moisture content without damage; a sigmoid curve was found to fit the relationship between germination and moisture content for the latter species. Secondly, D. intricatus, D. tuberculatus and D. alatus can be safely dried to 10%, 12% and 17% moisture contents respectively, but desiccation to near 7% moisture content reduced viability by at least a half. Storage studies showed that seed of D. intricatus and D. tuberculatus possessed increased longevity as moisture contents were reduced within the range 6–20%. It was concluded that seeds in the first group are ‘recalcitrant’ and that those in the second group are ‘orthodox’ in their storage physiology, according to the categories described by Roberts (1973).

Wide differences between species in seed desiccation rates were observed. In 15% relative humidity D. intricatus dried to 7% moisture content within a week, whilst D. obtusifolius retained 30% moisture content even after 5 wk; other species had intermediate desiccation rates. Seed size and structure may partly account for the differences observed.

Correlations were observed between seed storage physiology and other factors which were investigated. ‘Orthodox’ seeds had quicker desiccation rates, were derived from drier habitats, and had smaller embryos than those of ‘recalcitrant’ seeds.

‘Orthodox’ seeds, with the possible exception of D. alatus, should be kept at 0–3°C with about 12% moisture content in the short term and, provided less than 10% germination is lost on freezing, at‐18°C with about 8% moisture content in the long term. ‘Recalcitrant’ seeds should be stored in ventilated containers at 21°C and with moisture contents above 45–50%.
The germination and the forces required to penetrate seed layers of different seedlots of three cultivars of crisp lettuce
Authors: WURR D. C. E. , FELLOWS JANE R. , DREW R. L. K.
Published: February 2008

Using 24 commercial seedlots of the lettuce cvs Ithaca, Pennlake and Saladin, the percentage germination at a range of temperatures from 20 to 35°C, and the forces required to penetrate the pericarp, the endosperm and the embryo were measured. Percentage germination declined with increasing temperature in all seedlots but there were particularly large differences between seedlots of the same cultivar at 30.0 and 32.5°C.

The force required to penetrate the pericarp was on average more than twice that required to penetrate the endosperm. It is concluded that in commercial cultivars of crisp lettuce the strength of the pericarp plays a much greater role than that of the endosperm in determining germination.

In all three cultivars there were significant positive correlations between seed weight and the force required to penetrate the whole seed. However only in cv. Pennlake were there significant correlations between germination at high temperature and seed penetration forces.
Gel formulations for the treatment of pruning wounds.
Authors: CLIFFORD D. R. , GENDLE P. , HOLGATE M. E.
Published: February 2008

Gels incorporating carbendazim and triadimefon were prepared from sodium alginate, a xanthan gum or an esterified alginic acid and evaluated as wound treatments on apple and plum trees. Fungicide movement and persistence were similar with sodium alginate and xanthan gels but movement was reduced and persistence increased with the esterified material. Callus tissue formation was not inhibited by any formulation. Adding acid to fungicides to form salts had little effect on fungicide movement or persistence and caused unacceptable phytotoxicity.

Thiophanate‐methyl or thiabendazole were not superior to carbendazim, nor imazalil to triadimefon, for protection against Nectria galligena and Chondroster‐eum purpureum respectively.

Sealants containing octhilinone, carbendazim plus captan, or mercuric oxide quickly established sufficient fungicide in the wood to eradicate N. galligena but possibly insufficient to protect adequately against C. purpureum.

Gel formulations are valid alternatives to sealants as fresh wound pathogen treatments but fungicide persistence is insufficient for them to be recommended for treatment against mature wound pathogens.
Factors affecting competition of three strains of rhizobia nodulating groundnut, Arachis hypogaea*
Authors: NAMBIAR P. T. C. , ANJAIAH V. , RAO B. SRINIVASA
Published: February 2008

The nitrogen (N2) fixing ability of three strains of rhizobia (NC 92, NC 43.3, and TAL 176) was compared in groundnut cv. Robut 33–1. The competitiveness of these strains in pot culture in a sand‐vermiculite medium and with native rhizobia in the field was also investigated. In pot culture, NC 43.3 formed more nodules than TAL 176 and NC 92. Nodules formed by NC 43.3 and NC 92 fixed more N2 (as measured by total N content in the plants at 42 days after sowing) than nodules formed by TAL 176. TAL 176 was a poor competitor compared with NC 92, NC 43.3, or with native rhizobia in the field. NC 92 when mixed with NC 43.3 (106 cells seed‐1 of each strain) formed only 21% of the nodules, but when independently inoculated in the soil containing native rhizobia, the two‐strains formed similar percentages of nodules. Thirty percent of the nodules in two strain combinations of NC 43.3 and NC 92 showed double occupancy. Strain NC 43.3 formed nodules earlier than NC 92 and TAL 176 and this may be one of the factors responsible for its better N2‐fixation and competitiveness. Nodules formed earlier by one strain (NC 92 or TAL 176) were found to have no effect on the subsequent nodulation by the other (TAL 176 or NC 92) strain. Although NC 92 and NC 43.3 were equally competitive with native rhizobia in the field and NC 43.3 fixed more N2 than NC 92 in pot culture, earlier experiments indicated that only inoculation with NC 92 increased pod yield in field trials.
Control of contamination of potatoes with air‐borne Erwinia carotovora by foliar application of copper oxychloride
Authors: ELPHINSTONE J. G. , PÉROMBELON M. C. M.
Published: February 2008

In field experiments in 1983 and 1984, micropropagated plants of cv. Désirée planted in soil tested and found free of erwinias became contaminated with airborne erwinias, mostly E. carotovora pv. carotovora, in September when rain was more abundant, but not earlier. Control of contamination of progeny tubers harvested in September and October was achieved by spraying plants with copper oxychloride (‘Cuprokylt’; 5 g litre‐1) twice weekly from June or July but not from August nor by weekly or fortnightly treatments from June. Bactericidal activity of copper in the effective spray regimes was not expressed on the leaves or in the soil and contamination was similar in the sprayed and unsprayed treatments. In contrast, multiplication of erwinias in senescent leaves on the soil surface (leaf debris) was inhibited in the sprayed treatment but not in the unsprayed treatment and population numbers of c. 103 cells g‐1 fresh weight were detected. It is suggested that fewer erwinias would be washed from leaf debris by rain in the sprayed than in the unsprayed treatment to contaminate the progeny tubers.
The use of insecticides to control maize rough dwarf virus (MRDV) in maize*
Authors: ANTIGNUS Y. , KLEIN M. , OVADIA S.
Published: February 2008

Insecticides were screened in the laboratory for fast action against the delphacid planthopper, Laodelphax striatellus, the vector of maize rough dwarf virus (MRDV) in Israel. In these tests the synthetic pyrethroids were more efficient than oxydemeton‐methyl or endosulfan giving 50% mortality after 5 h compared to 10% in the non‐pyrethroid insecticides. Selected insecticides were then tested in maize fields for their effect on disease spread and crop yield. The synthetic pyrethroids cypermethrin, fluvalinate and biphenthrin reduced MRDV incidence by 22–59% and disease was less severe in the treated plots. Total crop yield (stems, leaves, ears) was 28% higher in the biphenthrin‐and fluvalinate‐treated plots than in untreated plots.
Purification and some properties of a new strain of cowpea mild mottle virus in Israel*
Authors: ANTIGNUS Y. , COHEN S.
Published: February 2008

The virus responsible for tomato pale chlorosis disease in Israel was purified from Nicotiana glutinosa plants. Purified virus contained a single stranded RN A of mol. wt 2.5 × 106 and a single coat protein subunit of mol. wt 31 000. Enzyme‐linked immunosorbent assay and an immunoelectron microscopy decoration test demonstrated a serological relationship with cowpea mild mottle virus (CMMV). Based on the present study and previously reported data the virus was identified as a new strain of CMMV designated CMMV/I.
Honeydew production and sap ingestion by the cereal aphids Rhopalosiphum padi and Metopolophium dirhodum on seedlings of resistant and susceptible wheat species
Authors: SPILLER N. J. , LLEWELLYN M.
Published: February 2008

Measurements of the frequency and rate of honeydew excretion by Rhopalosiphum padi and Metopolophium dirhodum, feeding on seedlings of resistant and susceptible wheat (Triticum monococcum and T. aestivum) were used to estimate the quantity of sap ingested over 24 h. Ingestion was significantly reduced on the more resistant T. monococcum and for M. dirhodum this may be due in part to a reduction in the success of phloem location.
The integration of host resistance with fungicides in the control of oat powdery mildew
Authors: JONES I. T. , RODERICK H. W. , CLIFFORD B. C.
Published: February 2008

Treatment of seed with the systemic fungicides triadimenol plus fuberidazole as Baytan significantly decreased powdery mildew in field experiments involving eight oat cultivars differing widely in their resistance to the disease. This was so up to growth stage G.S. 61 (Zadoks) even in a year of high mildew incidence, although the effect diminished after flowering.

Significant (P≥ 0.001) interactions between fungicide treatments and cultivars occurred in each of three years at nearly all assessment times. In years of high mildew incidence (1983 and 1984), susceptible cultivars developed similar levels of mildew in seed‐treated and untreated plots by about flowering time, although cultivars with adult plant resistance (APR) had significantly less mildew when seed‐treated than when left untreated. Later, as the APR was fully expressed and the fungicide effectiveness was declining, similar mildew levels were recorded on treated and untreated plots. Untreated APR cultivars generally had less mildew than treated susceptible cultivars and in a year of late and light mildew, APR alone provided good protection. Seed treatments combined with foliar sprays of tridemorph as Calixin almost completely controlled mildew except on very susceptible cultivars late in the season in high mildew years.

Over all cultivars, seed treatment gave yield advantages of 5.3% (1983) and 6.6% (1984) but in 1982, a year of low mildew, the response was small.

The possible influence of integrated host resistance and fungicides in stabilising the pathogen population at economically unimportant levels and the environmental benefit of using host resistance to minimise fungicide usage is discussed.
Effects of delaying fungicide treatment and of curing and chlorpropham on the incidence of skin spot on stored potato tubers
Authors: HIDE G. A. , CAYLEY G. R.
Published: February 2008

Potato tubers wounded with pin pricks and inoculated with Polyscytalum pustulans were not treated or treated with fungicide on the following day or after holding them in dry or damp conditions at 5, 10 or 15°C for periods up to 21 days. Tubers were then stored in damp conditions at 5°C and skin spot assessed after 24 wk. Disease was progressively decreased on untreated tubers by increasing the holding time and temperature in dry, but not damp conditions. Curing at 15°C for 14 days in dry conditions decreased the incidence of skin spot from 70% prick wounds infected to 4% but in damp conditions to only 53%. Fungicides controlled disease best when applied the day after inoculation, and more disease developed on tubers treated after holding in damp rather than dry conditions.

Incidence of skin spot in store on naturally infected tubers increased the later they were harvested. Carbendazim controlled the disease when applied immediately after harvest or up to 2 wk later and efficacy was greater after early than late harvest.

More skin spots developed on inoculated tubers stored at 5 than at 10°C but applying the sprout suppressant chlorpropham (CIPC) increased the number and size of spots, especially on tubers stored at 10°C. The disease was increased most by CIPC applied 2 days after inoculation; treatment after 5 but not after 10 wk also increased it. CIPC also slightly increased skin spot on tubers previously treated with carbendazim.

These experiments with naturally infected or inoculated tubers showed that skin spot in store can be decreased by early harvesting, by curing in dry conditions and by applying fungicide to tubers soon after harvest. They also indicated that when tubers are harvested damp, the disease can be controlled by drying or, if fungicides cannot be applied immediately, the tubers should be kept cool before treatment.
Effects of seed treatment with a plant growth regulator on growth and tillering in spring barley (Hordeum distichum) cv. Triumph
Authors: WOODWARD E. J. , MARSHALL C.
Published: February 2008

Doses of the growth retardant, Terpal, were applied to seeds of spring barley. Germination was delayed as the concentration and duration of exposure to Terpal increased. Tiller bud outgrowth was promoted in treated seedlings and at maturity the total tiller production and number of ear‐bearing tillers per plant was increased by the Terpal treatment. The yield of the main shoot was similar in both control and treated plants but the mean ear weight of the tillers was reduced in the latter, and thus there was no overall effect of the treatment on yield. Observations on vegetative plants showed that Terpal also reduced the growth of successive main shoot leaves and the elongation and dry weight of the seminal root system. The results are discussed in terms of an early modification in the distribution of resources during establishment that favour the outgrowth of tiller buds at the expense of the initial development of the main shoot and root system. It is proposed that seed treatment is a viable alternative to foliar spraying particularly in arid regions.
Elimination of stem pitting and corky bark diseases from grapevine by fragmented shoot apex culture
Authors: BARLASS M.
Published: February 2008

Fragmented shoot apex culture of grapevine has been shown to regenerate plants free from the graft‐transmissible diseases stem pitting (legno riccio) and corky bark. The efficiency of elimination of the disease agents following 2 years of indexing based on 66 plants of three varieties was 100%.
Further studies relating chlorogenic acid concentration in carrots to carrot fly damage
Authors: COLE ROSEMARY A. , PHELPS KATHLEEN , ELLIS P. R. , HARDMAN J. A. , ROLLASON S. A.
Published: February 2008

The effects of first generation carrot fly larval damage on chlorogenic acid concentration in carrots was investigated in a field experiment at Wellesbourne in 1985. In a separate experiment carrots grown in the absence of a resident population of carrot fly were also analysed for chlorogenic acid; these carrots maintained low concentrations of chlorogenic acid through the summer and autumn until low ground temperatures occurred from November to January. The relationship between chlorogenic acid concentration and damage by the first generation of carrot fly was described by a similar model to the one derived previously for late‐generation damage but without the cultivar dependence. This may have been because first generation damage takes place in mid‐summer when soil temperature is not sufficiently low for differential chlorogenic acid production by carrot cultivars. The model supports the hypothesis that carrot fly damage increases chlorogenic acid production which subsequently encourages further attack. The increase in acid production due to the low winter temperature may be the mechanism which, in turn, induced a differential cultivar response in carrots harvested during the winter.
The effects of Pythium sylvaticum, seed‐borne pathogens and seed treatments on the emergence of brassica seedlots of high vigour
Authors: WHITE J. G. , HO R. K.
Published: February 2008

The emergence from brassica seedlots designated by seed merchants as being of high vigour was measured in sterilised soil and in sterilised soil re‐inoculated with Pythium sylvaticum. The mean emergence level of 93·9% in the former compared favourably with the known mean total viability of the seedlots (97·7%). However, P. sylvaticum reduced emergence of 10 out of 16 untreated seedlots. The majority of seedlots gave > 75% emergence but in three cases emergence was reduced by 32·5–40·0%. The effects were not related directly to time taken to emerge, nor were the seedlots most affected those with high levels of infection. A compound seed treatment containing metalaxyl, fenpropimorph and gamma‐HCH restored high emergence levels.
Degradation of pectic substances in green flax fibre by Erwinia carotovora
Authors: MORVAN ODILE , JAUNEAU ALAIN , MORVAN CLAUDINE , DEMARTY MAURICE , RIPOLL CAMILLE
Published: February 2008

In this paper, we report that Erwinia carotovora can perform controlled biological pectinolysis of green flax fibre. The degradation of pectic substances is considered a key step during this process and is estimated by determining the cation exchange capacity (CEC). A CEC characteristic of a ‘good retting degree’, is reached after 20 h incubation, whatever the tested temperature and initial pectate lyase activity of the bacterial culture. Similar results are obtained after only 4 h, at a temperature of 45°C and the pectate lyase activity is greater than 2 nmol ml‐1 min‐1. The linear relationship between the CEC and the weight loss of green fibre which is established, allows us to estimate an equivalent weight of 1000 g eq‐1 for the solubilised polymers.
Identification and characterisation of a newly described potyvirus in West Africa: Asystasia mottle virus
Authors: THOUVENEL J.‐C. , FAUQUET C. , FARGETTE D.
Published: February 2008

Asystasia mottle virus (AsMV) was detected serologically in samples of Asystasia gangetica with mottle symptoms, from several areas of tropical West Africa. It infected 12 species systemically and induced local lesions in a further four.

The virus lost infectivity after dilution to 10‐4, after 10 min at 75 °C and after 3 days at 27°C. Purified virus had an A260/A280 ratio of c. 1·2 and a protein subunit mol. wt of c. 33 000. Particles were c. 750 nm long and cytoplasmic inclusions typical of potyviruses were seen in ultrathin sections of infected leaves. The antiserum prepared had a titre of 1/1024 in microprecipitin tests but purified virus failed to react with 31 antisera to known potyviruses.

The virus was transmitted in the non‐persistent manner by Aphis spiraecola but only very infrequently. On the basis of these properties, AsMV is considered to be a new member of the potyvirus group.
Studies on the growth and development of Oxalis latifolia
Authors: MARSHALL G. , GITARI J. N.
Published: February 2008

The growth and development of Oxalis latifolia was assessed on outdoor‐grown potted plants raised from bulbs. Three main phases of growth appeared to be correlated with major physiological developments in the aerial and subterranean organs. Establishment (weeks 1 – 5) was characterised by a slow gain in plant dry weight accompanied by high relative growth rate (RGR) values for individual plant organs. The second phase of growth (weeks 6 – 12) was reproductive, as stolons grew and initiated bulbils at the apices. Bulbils had the capacity to produce their own shoot system and ultimately some primary bulbils supported secondary bulbils. Dry matter accumulation was in the order: bulbils > peduncles > leaves > petioles > stolons = roots > parent bulb. The RGR of individual plant organs declined together with the net assimilation (NAR) rates and the leaf area ratio of the shoots during the reproductive phase and beyond into the senescence phase (week 13 onwards). The results are discussed in relation to the problem of achieving weed control via cultural and herbicide treatments.
A rapid non‐destructive technique for screening carrot seedlings for resistance to carrot fly damage
Authors: COLE ROSEMARY A. , ROLLASON S. A. , MORGAN A. , GILCHRIST J. , BAKER S. A. , SPRINGER P.
Published: February 2008

A technique based on fluorescence of carrot root tissues has been devised to enable large numbers of accessions to be screened for resistance to carrot fly using an epi‐fluorescence microscope. The technique is non‐destructive, and has been partly automated to assess at least 400 seedlings/hour. A data‐capture and handling package provides prompt summarising and print‐out of the results.
Competition between grass and clover in spring as affected by nitrogen fertiliser
Authors: WOLEDGE JANE
Published: February 2008

Detailed measurements of irrigated ryegrass/white clover swards growing without interruption, with or without nitrogen fertiliser in spring, showed that the relative growth rate of clover was as great as that of grass, in the + N sward, and considerably greater than grass, in the – N sward. Clover leaves were not overtopped by grass leaves. Indeed, in both swards, clover had a greater proportion of its leaf lamina area in the upper, well lit, layers of the canopy than grass did. Consequently, clover had a greater mean rate of leaf photosynthesis in situ in the sward than grass. Clover's advantage in photosynthetic rate per leaf area was offset to some extent by its smaller ratio of leaf area to total above‐ground dry weight than grass.

The consequences of these results for our understanding of competition between grass and clover in mixed swards are discussed.
Effects of temperature and water potential on the germination of muskmelon cultivars
Authors: DUNLAP J. R.
Published: February 2008

The rate and final germination of four muskmelon cultivars (Cucumis melo) were examined in response to incubation temperatures of 20, 26 and 32°C. Germination was also characterised at 26°C pr 32°C over a range of water potentials from 0 to ‐ 1000 kPa achieved with solutions of polyethylene glycol. The germination of one cultivar, TAM‐Uvalde, was consistently slower at 20°C than at 26°C or 32°C. The other three cultivars, Perlita, TAM‐Dew and Greenflesh, were inhibited by incubation at 32°C. However, the germination responses of cvs Perlita, TAM‐Dew and Greenflesh at 26°C or 32°C improved as water potentials were reduced from 0 to – 200 or – 400 kPa. Cv. TAM‐Uvalde was extremely sensitive to water stress and failed to germinate at water potentials below – 600 kPa when incubated at 26°C. The inhibition of germination at low water potentials was partially reversed in all cultivars by increasing the incubation temperature from 26°C to 32°C. It is suggested that the inhibition of germination at 0 kPa (distilled water) was due to a seed coat‐mediated barrier to oxygen that could be reversed by removal of the seed coat or exposure to an oxygen‐enriched atmosphere.
Causes of uneven desiccation of flax by glyphosate: poor penetration of the canopy and variable spray deposition
Authors: HARVEY B. M. R. , CROTHERS S. H.
Published: February 2008

Flax (Linum usitatissimum) cv. Hera was grown at densities of c. 2000, 1500 and 1000 plants m‐2sprayed with glyphosate (1·44 kg a.e. ha‐1) and red dye (1·5%).

Dye deposition was measured and the mean total was 402, 503 and 602 μg per plant or 691, 761 and 761 μg g‐1DW for high, intermediate and low densities respectively. Variation between plants was large and significant differences were found only in deposition on the lower stem, this being about two‐fold higher for plants grown at 1000 m‐2than 2000 m‐2. However spray penetration through the crop canopy was poor and only c. 4% of the total deposit was intercepted by the lower stem. There was no detectable dye deposition on the lower stem of some plants in stands of all densities.

The minimum deposits of glyphosate required for desiccation were assessed by applying precise doses, using a microsyringe, to plants grown under controlled environmental conditions. A total dose of 40 μg applied to the capsules, the upper stem plus leaves and the lower stem in the approximate ratio found for dye deposition on field grown plants, was required for successful desiccation. The minimum amount of glyphosate deposited in the field experiment, calculated assuming a linear relationship between dye and glyphosate deposition, was only 5 μg per plant.

Position of application was also important. Application of 6 μg glyphosate to the lower stem caused desiccation of the whole plant whereas in applications to the upper stem and leaves 64 μg was required to have a similar effect.

These experiments indicate that uneven desiccation of flax crops can be accounted for by both lack of uniformity of spray deposition and poor penetration of spray through the canopy to the lower stem, where glyphosate would be most active.
A glasshouse test to assess the sensitivity of potato cultivars to tobacco rattle virus
Authors: DALE M. F. B. , SOLOMON R. M.
Published: February 2008

The sensitivity to tobacco rattle virus of nine potato cultivars and 24 potato clones from the potato breeding programme at SCRI was assessed in a glasshouse pot test and in field trials for two consecutive years. The results and analyses presented indicate that the pot test gives an accurate and reliable estimate of sensitivity to tobacco rattle virus. Methods of assessing severity of expression of disease symptoms were examined. The advantages of such a glasshouse pot test and its application are discussed.
Prediction of the coefficient of variation of carrot embryo length from a germination test
Authors: GRAY D. , GENT LOUISE J.
Published: February 2008

The value of the International Seed Testing Association (ISTA) germination test in estimating levels of variation in embryo length between carrot seed lots was examined.

For the two groups of seed lots used, the coefficient of variation (c.v.) of embryo length ranged from 16 to 50%. The c.v. of embryo length was negatively correlated with the numbers of normal seedlings counted after 7 days of germination at 20°C, rs= ‐ 0·72 D.F. 12 and ‐ 0·82, D.F. 15 for the two groups of seed lots used. Provided the relationship between these two characters is established for each laboratory, it is likely to be useful in identifying seed lots of potentially low c.v. of embryo length.
Quantitative and qualitative aspects in the production of a nuclear polyhedrosis virus in Spodoptera exigua larvae
Authors: SMITS P. H. , VLAK J. M.
Published: February 2008

Spodoptera exigua nuclear polyhedrosis virus was produced in late fourth instar S. exigua larvae, reared on semi‐artificial diet. A maximum amount of virus, 1–2 × 109 polyhedra/larva, was produced in individually‐reared larvae after 7 days of incubation, with an inoculum of 7–5 × 104 polyhedra/cm2 diet surface.

Virus yield was slightly reduced to 9 × 108 polyhedra/larva when production was carried out in groups of 400 and 600 larvae per container. Biological activity of virus harvested from living larvae and from dead cadavers was similar. Microbial contaminants, predominantly bacteria, in the virus product numbered 1–6% of the number of polyhedra. Tests for the presence of vertebrate‐pathogenic bacteria in the virus product were all negative.
Soybean leaf pubescence affects aphid vector transmission and field spread of soybean mosaic virus
Authors: GUNASINGHE U. B. , IRWIN M. E. , KAMPMEIER G. E.
Published: February 2008

A study was undertaken to determine the influence of trichome density on the spread of non‐persistently transmitted plant viruses by aphid vectors. A system using soybean plants and soybean mosaic virus (SMV) tested the hypothesis that greater leaf trichome density inhibits probing activity of vector species, leading to reduced virus spread and retarded virus epidemics under field conditions.

Probing activity of three important aphid vectors of SMV, Myzus persicae, Rhopalosiphum maidis, and Aphis citricola, was affected by the density of soybean leaf trichomes. Less pubescent and glabrous isolines elicited greater probing activity than did densely pubescent isolines. Among the parameters considered, probe duration was found to be species specific, whereas the following traits were consistent among species for the denser isolines: reduced numbers of probes, greater length of time to first probe, and less time spent probing. Laboratory transmission of soybean mosaic virus was reduced in the more densely pubescent isolines by the vector species tested.

Field spread of SMV was negatively correlated with density of pubescence. In our system, we found that denser leaf pubescence retards field epidemics of non‐persistently transmitted plant viruses.
Reactions of white cabbage (Brassica oleracea var. capitata) to four different strains of turnip mosaic virus
Authors: WALKEY D. G. A. , PINK D. A. C.
Published: February 2008

TuMV strains isolated in the UK, Germany, Denmark and Greece have been shown to be biologically distinct by host range studies. The effects of the four strains on symptoms, yield and storage performance of four cultivars of white cabbage were assessed in gauze house experiments. Three of the cultivars, Decema Extra, Vitala and Winter White III, were known to have high levels of resistance to the UK strain and the fourth, cv. Polinius, is known to be highly susceptible. The resistance to the UK strain previously observed in the three ‘resistant cultivars’ was generally effective against the other three strains; however, the level of resistance was virus strain dependent and variable for the symptoms of external necrosis, internal necrosis and yield depression. The UK strain caused the highest level of external necrosis and the German strain the highest internal necrosis. These two strains generally caused greater yield reductions than the Danish or Greek strains. Virus infection had no effect upon the incidence of the pepper‐spot necrosis disorder. Breeding strategies for handling the observed resistance are discussed.
Purification and some properties of oat golden stripe virus
Authors: ADAMS M. J. , JONES P. , SWABY A. G.
Published: February 2008

Oat golden stripe virus (OGSV) was maintained in oats by mechanical inoculation and purified by extraction of leaves in borate buffer, two cycles of centrifugation through sucrose cushions and isopycnic centrifugation in CsCl. An antiserum with a titre of 1/1024 in precipitin tests was prepared. Particle length distribution was bimodal with median values, respectively, of 150 and 300 nm from dip preparations. Measurements from immunosorbent electron microscopy (ISEM) and purified preparations showed that the particles had partially degraded during these procedures. The virus sedimented as two components of 168 S and 218 S and had a buoyant density of 1321 g cm‐3.

Four isolates of OGSV reacted with the antiserum. Antiserum to members and possible members of the furovirus group were tested in ISEM decoration tests and in ELISA. OGSV was related to soil‐borne wheat mosaic virus but not to beet necrotic yellow vein virus, hypochoeris mosaic virus or potato mop‐top virus.
Ourmia melon virus, a virus from Iran with novel properties
Authors: LISA VITTORIA , MILNE R. G. , ACCOTTO G. P. , BOCCARDO G. , CACIAGLI P. , PARVIZY R.
Published: February 2008

A virus associated with a mosaic disease in melons in the Ourmia district in northern Iran was mechanically transmissible to a wide range of test plants but was not transmitted using aphids, the whitefly Trialeurodes vaporariorum or the mite Tetranychus urticae. Its rather stable particles somewhat resembled those of both geminiviruses and alfalfa mosaic virus; they were 18·5 nm in mean width, parallel‐sided, and of several discrete lengths, 30 nm and 37 nm being the shortest and commonest lengths. Both ends of all particles were sharply triangular in profile. The particles contained linear single‐stranded RNA of three sizes, estimated as 0·91,0·35 and 0·32, all × 106 molecular weight, and two coat proteins of 26·3 and 23·3 × 103 estimated molecular weight. The virus, named Ourmia melon virus, appears to be the first described representative of a new virus group.
Relationship between inoculum density and vector phenology on the incidence of potato virus Y in tobacco
Authors: GRAY STEWART M. , LAMPERT E. P.
Published: February 2008

The epidemiology of potato virus Y (PVY) in the tobacco crop, Nicotiana tabacum, was examined in the context of the seasonal abundance of aphid vectors, rate of disease progress, and disease gradient from a known virus source. The spring potato crop, Solanum tuberosum, was suspected of being the main source of inoculum; therefore, varying numbers of infected potato plants were used as the inoculum source in different test plots.

A 3‐wk lag phase was present in all disease progress curves prior to an exponential increase in disease incidence. The relatively low numbers of aphid vectors, primarily transient species, alighting on the crop during the lag phase were responsible for the primary spread of PVY from potato to tobacco. The arrival of large numbers of colonising aphid vectors, Myzus persicae, presumably from the harvested potatoes, coincided with the exponential increase in PVY incidence in tobacco.

The initial number of potato plants infected with PVY was positively correlated with the final disease incidence, rate of disease progress, and the magnitude of radial dispersion of PVY into the tobacco. Aphid vector pressure was not a significant variable in the differences in spatial and temporal characteristics of PVY epidemics among test plots.
Shelf‐life of stored asparagus is strongly related to post‐harvest accumulated heat units
Authors: KING GRAEME A. , HENDERSON KATE G. , LILL ROSS E.
Published: February 2008

The effect of delay between harvest and hydrocooling, and of regimes of simulated air transport temperatures, on shelf‐life of fresh asparagus were quantified. Shelf‐life was strongly negatively correlated with the accumulated heat units experienced between harvest and post‐transport handling. A 2‐h delay in hydrocooling after harvest was similar to a 0.5°C higher temperature during a 2‐day transit period in effect on shelf‐life. It is essential for maximum shelf‐life that asparagus be kept cold from the completion of hydrocooling until sale.
Gibberellin, daylength and temperature effects on floral and vegetative development in white clover
Authors: NORRIS I. B.
Published: February 2008

The effects of gibberellin A3 (GA3) application on five white clover populations was assessed in both glasshouse and controlled environments. Daylength, temperature and GA3 interactions were also examined.

Gibberellin A3 did not induce vegetative plants to flower when daylength and temperature requirements were not met. In flowering plants, GA3 increased the number of reproductive buds per stolon and peduncle length, but did not affect other floral characters.

Gibberellin A3 depressed total stolon numbers, but increased the number of nodes per stolon, internode length, leaf area and petiole length.
The effect of Drechslera teres seed infection on spring barley seedling growth
Authors: DEADMAN M. L. , COOKE B. M.
Published: February 2008

Barley seedlings (cv. Beatrice) emerging from seed infected with Drechslera teres were sorted into healthy seedlings, those with leaf sheath lesions and those with leaf blade lesions. Leaf area, plant height and total weight were reduced relative to healthy plants; leaf emergence also appeared to be delayed.
Initiation at the flowering stage of postharvest Botrytis stem‐end rot in normal and non‐ripening tomato fruits
Authors: LAVY‐MEIR GILA , BARKAI‐GOLAN RIVKA , KOPELIOVITCH E.
Published: February 2008

Flowers of a normal tomato cultivar and of the two non‐ripening mutants rin and nor, were sprayed with a Botrytis cinerea spore suspension. Stem‐end infection developed in 84–100% of the harvested fruits of these sprayed flowers when held in high r.h. In both nor and rin fruits, rot development remained restricted to the stem‐end area and fruit shoulders, whereas in the normal fruit decay spread rapidly from the stem‐end over the entire fruit. Spraying the flowers with iprodione prior to spore inoculation resulted in decreased incidence of decay and suppressed hyphal growth and sporulation in all types of fruits. The results indicate that floral organs serve as a pathway for B. cinerea stem‐end initiation in both the normal and the mutant fruit and suggest that this mode of penetration is not related to the marked resistance to infection attributed to the mutant fruits.
The inhibitory effects of the molluscicide metaldehyde on feeding, locomotion and faecal elimination of three pest species of terrestrial slug
Authors: WEDGWOOD MARILYN A. , BAILEY STUART E. R.
Published: February 2008

Single meals on maize flour pellets containing 0, 0·5, 1, 2, 4, 6, and 8% metaldehyde were analysed in Arion hortensis (agg), Deroceras reticulatum and Deroceras caruanae, by attaching the pellets to a mechanical transducer from which signals were ultimately fed into a BBC microcomputer for on‐line analysis. Post‐feeding tests were used to investigate toxic effects of metaldehyde and the recovery of slugs was examined daily for 7 days. Bite rates were slightly lower and more irregular on metaldehyde meals especially in A. hortensis. The meal length and number of bites per meal were markedly inhibited by metaldehyde and inversely proportional to the concentration. The size of the bites was also reduced, by about 30%, in meals on 6% pellets compared with 0%. Clear symptoms of poisoning became evident during the meal or normally in the 16‐min test period immediately afterwards. In these tests slugs which fed on metaldehyde pellets showed a disruption of their ability to right themselves (after being placed on their side), less activity and a reduced probability of accepting a ‘dummy’ pellet containing no metaldehyde. It is hypothesised that feeding is prematurely terminated primarily because of the toxic effects of the metaldehyde and that aversion also acts to terminate the meal early, by decreasing the probability of continuing to feed as the meal proceeds. At higher concentrations of metaldehyde aversion may be more important than the toxic effects in ending the meal. Faecal elimination is delayed after metaldehyde meals and this contributes to mortality. The estimated lethal doses were about 0·2 mg/g body weight of slug in Deroceras spp. A. hortensis was less susceptible. To increase the likelihood of a lethal dose being ingested the inhibition of feeding needs to be overcome, at least partly, and the results presented indicate the need for a bait formulation which reduces the rate of absorption of the molluscicide from the gut.
Storage diseases of carrots in East Anglia 1978 – 82, and the effects of some pre‐ and post‐harvest factors
Authors: GEESON J. D. , BROWNE K. M. , EVERSON HELEN P.
Published: February 2008

In a survey of nine carrot crops stored during four seasons 1978 – 82, the major causes of wastage were spreading soft rots caused by Botrytis cinerea and Rhizoctonia carotae; rots caused by Sclerotinia sclerotiorum, Mycocentrospora acerina and Stemphylium radicinum were only of secondary importance. Storage weight losses were lower and roots remained turgid for up to 40 wk in an ice‐bank‐cooled store at 0·5 °C, 97 – 98% r.h., whereas carrots in conventionally‐cooled stores at 2 – 2.5 °C, 90 – 95% r.h. became flaccid after a few months. In some crops, losses due to fungal spoilage were also lower in the ice‐bank store. In two seasons' losses, mostly due to B. cinerea, were similar in hand‐ and machine‐harvested roots; pre‐storage washing of carrots grown on mineral soils increased the incidence of Botrytis rots, and reduced rotting by R. carotae, but had no effect on spoilage of roots from peat soils. Post‐harvest fungicide treatment with benomyl or iprodione (0·5 g/litre a.i.) effectively reduced rotting by B. cinerea and S. sclerotiorum, but not by R. carotae. The recoveries of sound carrots after 23 – 29 wk storage were consistently highest (mostly > 80%) from fungicide‐dipped roots stored under ice‐bank conditions, but recoveries from all treatments were lower and more erratic after 35 – 40 wk because of increased fungal spoilage. The practical applications of long‐term ice‐bank storage of UK‐grown carrots are discussed.
Trialling techniques in the breeding and prediction of recombinant inbred lines in onions (Allium cepa)
Authors: WERNER C. P. , DOWKER B. D. , DeSOUZA D. C. , CROWTHER T. C. , HOROBIN J. F. , KEARSEY M. J.
Published: February 2008

An outline is given of a novel breeding scheme for onions to produce highly vigorous, good quality inbred lines adapted for autumn‐sowing in the UK. The scheme involves the production of advanced generation inbred lines in the absence of selection, by single seed descent, starting with 1500 F2 plants from a Japanese × European cross. Concurrently a genetical analysis designed to predict the range of recombinant inbred lines derivable from this cross has been conducted using triple test cross (TTC) and basic generation (BG) families. Four trials are described, the results of which are used to define trialling techniques for the TTC and BG material which enable genetical predictions to be applied to direct‐drilled onions at commercial spacings. The ranking of genotypes for important agronomic characters remains unchanged whether they are grown as transplanted spaced single plants or direct‐drilled, however interactions may occur if pre‐chitted seed is used.