bluuebunny/crossref_metadata_2025 huggingface dataset:
A new method for disease‐loss studies used to estimate effects of Pyrenophom teres and Rhynchosporium secalis on winter barley yields
Authors: SHAW M. W. , ROYLE D. J.
Published: February 2008

SUMMARY

It may be argued that the basic task of yield‐loss studies is to estimate the rate at which a given amount of disease causes a crop to lose yield at each instant during the growing season. This loss rate function can be estimated from detailed data on sets of epidemics and the yields resulting from them in otherwise similar crops. Under certain circumstances, the calculations reduce to regression of yield on integrals of functions of developmental time and disease. Thermal time may form a suitable approximation to developmental time.

The technique was tested using 30 plots 12m × 4 m of winter barley cv. Sonja, in which epidemics of Pyrenophora teres and Rhynchosporium secalis developed. An equation describing loss rate due to P. teres throughout the season and R. secalis in spring was successfully developed. The loss rate due to P. teres was greatest later in the season, and disproportionately severe at low disease levels. On the basis of this experiment the proposed technique compares well with alternatives.
The effect of cultivar used as host for Polymyxa gmminis on the multiplication and transmission of barley yellow mosaic virus (BaYMV)
Authors: ADAMS M. J. , JONES P. , SWABY A.G.
Published: February 2008

A viruliferous isolate of the fungal vector Polymyxa graminis was grown on roots of barley cultivars immune or susceptible to barley yellow mosaic virus (BaYMV). Zoospores or resting spores of the vector produced on different cultivars were then inoculated to a virus‐susceptible test cultivar. Although the vector established in all treatments, transmission of BaYMV was rare and usually nil from immune cultivars; amounts of virus detected serologically in their roots were very low, thus showing that resistance was to virus multiplication. If immune cultivars decrease the virus content of vector populations in the field, this would have important implications for disease control.
Virus diseases of subterranean clover
Authors: JOHNSTONE G. R. , McLEAN G. D.
Published: February 2008

Subterranean clover (Trifolium subterraneum) is grown as a pasture legume in several temperate regions of the world where the soils are acidic and infertile, and the rainfall is winter dominant and less than 600 mm annually. It is particularly important in southern Australia where more than 16 million ha have been sown with this species as the pasture legume component.

Nine viruses have been recorded infecting subterranean clover in the field. These are alfalfa mosaic, bean yellow mosaic (pea mosaic), beet western yellows, clover yellow vein, cucumber mosaic, pea enation mosaic, soybean dwarf (subterranean clover red leaf), subterranean clover mottle and white clover mosaic. In addition there is an important problem referred to as subterranean clover stunt that was assumed to be caused by a virus but whose aetiology is still unknown. The importance of these diseases is reviewed and details on their epidemiologies are outlined together with details on progress towards their control and some comments on matters worthy of attention in the future. Reference is also made to several exotic viruses known to infect subterranean clover experimentally that could possible cause problems if introduced into Australia.
The decimal code for the growth stages of cereals, with illustrations
Authors: TOTTMAN D. R.
Published: February 2008

The decimal code for the growth stages of cereals, devised by Zadoks, Chang & Konzak (1974), is reproduced with stylised drawings of selected stages of wheat, barley and oat plants. Expanded definitions of some of the descriptive phrases are designed to assist the application of the code to agrochemical research, development and use in the UK.
Gel formulations for the treatment of pruning wounds.
Authors: CLIFFORD D. R. , GENDLE P. , HOLGATE M. E.
Published: February 2008

A mixture of carbendazim and triadimefon in an aqueous gel formed from sodium alginate is an alternative to conventional sealants for the treatment of pruning wounds on apple and plum trees. Patterns of movement and persistence of fungicides after application of the gels during dormancy or the growing season are reported. Callus tissue formation is not impaired and treatment does not affect the natural microbial population of the wood. Persistence of fungicides within the wood is insufficient for the formulation to be suitable for a mature wound pathogen treatment but this easily prepared formulation can protect wounds for as long as they are vulnerable to attack by the fresh wound pathogens Nectria galligena and Chondrostereum purpureum.
Laboratory observations on the effect of humidity on the persistence of infectivity of conidia of the aphid pathogen Erynia neoaphidis
Authors: BROBYN PATRICIA J. , WILDING N. , CLARK SUZANNE J.
Published: February 2008

Conidia of the aphid pathogen Erynia neoaphidis on detached bean leaves and glass coverslips maintained at 20°C and at humidities from 40 to 100% r.h. lost their infectivity for pea aphids at a rate dependent on the humidity. Infectivity declined most rapidly in inocula kept on leaves at 70% r.h. and persisted longest in those at 40 and 50% r. h. That of inocula on coverslips declined most rapidly at 77% r.h. and persisted longest in those kept at 40% r.h. Even after 21 days a little infectivity was retained by conidia stored at 50% r.h. on leaves and 40% r.h. on coverslips.
Standard descriptions of growth stages of annual dicotyledonous weeds
Authors: LUTMAN P. J. W. , TUCKER G. G. , BROAD HILARY
Published: February 2008

Fifteen growth stages of annual dicotyledonous weeds are described and illustrated, showing the progression from emergence to senescence. These stages have been agreed following widespread consultation amongst the member organisations of the British Crop Protection Council. Stages are defined in terms of leaf number, plant size and floral development. They are intended for use in the field by farmers, growers and their technical advisers, on herbicide labels and in advisory publications. They are also of value in research, aiding the description of weeds in field and glasshouse experiments.
Improving the biological efficacy of small droplets of permethrin by the addition of silicon‐based surfactants
Authors: ADAMS A. J. , FENLON J. S. , PALMER ANNE
Published: February 2008

Oil‐soluble and oil‐dispersible silicon‐based, non‐ionic surfactants were incorporated in two oil‐based formulations of permethrin. At the optimal concentration of surfactant, 40 μm droplets of the insecticide were twice as effective against whitefly (Trialeurodes vaporariorum) larvae as droplets without surfactant. The addition of a surfactant to a formulation containing 10 g/litre permethrin resulted in a spray mixture which was at least as effective as the same formulation containing 100 g/litre permethrin without surfactant. These improvements in efficacy were not attributable to droplet spread or perimeter on the leaf surface, or to differences in the surface tension of the mixtures. The implications of these results for ultra‐low volume spraying are discussed. A statistical model based on the zero‐cell of the Poisson distribution is described and used to analyse the bioassay results.
Factors affecting the production and motility of zoospores of Polymyxa graminis and their transmission of barley yellow mosaic virus (BaYMV)
Authors: ADAMS M. J. , SWABY A. G.
Published: February 2008

Cultures of Polymyxa graminis were maintained in roots of barley plants grown in sand at different temperatures using Wisconsin soil temperature tanks. At 17 – 20°C, the minimum time from inoculation with cystosori to the production of zoospores from the inoculated roots was 2 – 3 wk. At 11 – 20°C many zoospores were produced but the incubation period was longer at the lower temperatures. Above 20°C little fungal development occurred.

The duration of motility of zoospores ranged from c. 1 h to > 24 h. Bovine serum albumen (BSA) prolonged motility but glycine and glucose had no effect or, at higher concentrations, were toxic. Zoospores were rapidly immobilised by zinc ions in solution at or above 10μg/ml.

In some experiments BSA added to the zoospore suspension greatly increased transmission of barley yellow mosaic virus (BaYMV) while glucose, glycine and ovalbumen decreased it. When seedlings were incubated with zoospore suspensions for 24 h at different temperatures, BaYMV transmission was high (> 60%) at 10, 15 and 20°C but there was little at 5 or 25°C. In experiments to determine the time taken for zoospore penetration, seedlings were incubated in suspension for different periods of time and then rinsed in zinc sulphate solution to kill free zoospores. Between 3 and 3·5 h was needed for zoospores to establish infection. Transmission occurred equally to plants of various ages between 3 days and 7·5 wk.
The effect of triadimenol on the cytology and growth of sensitive and resistant strains of Ustilago avenue
Authors: HIPPE SIGRUN , GIESEN ULRIKE
Published: February 2008

Two triazole resistant mutants of Ustilago avenae and a wild type strain were treated with different concentrations of the fungicide triadimenol in liquid cultures. Growth rates were measured and the morphology of the sporidia examined by light and electron microscopy. After treatment with 1 – 10 μg ml‐1 for 4 days wild type sporidia increased in growth rate, changed from budding to filamentous growth and had considerably thicker cell walls. Their cytoplasm also showed strong degeneration and damage to the cell organelles. The resistant strains were not influenced under these conditions but under longer exposure (14 days) to higher fungicide concentrations (50 to 200 μg ml‐1) similar changes to growth rates, morphology and cell wall thickness also occurred. However, cell disruption only occurred at 200 to 250 μg triadimenol ml‐1 and there were differences in cell wall thickening. One resistant strain (r13) never showed thickening, while in the other (r8), the wall consisted of two distinct layers. The implications of these results are discussed in relation to possible resistance mechanisms.
Bacterial blight of kiwifruit
Authors: YOUNG J. M. , CHEESMUR G. J. , WELHAM F. V. , HENSHALL W. R.
Published: February 2008

Bacterial blight of kiwifruit (Actinidia deliciosa) is caused by Pseudomonas viridiflava. Symptoms are rot of floral buds and flowers, and spots on leaves. Buds and flowers nearest the ground are most likely to be affected. Isolations made from healthy buds, flowers and leaves suggest that the pathogen is an epiphyte on vines throughout the year. Disease incidence fluctuates between seasons, and varies between orchards. A relationship between disease incidence and rainfall in spring is indicated.
A field screening method to evaluate rice breeding lines for resistance to the hoja blanca virus
Authors: ZEIGLER R. S. , RUBIANO M. , PINEDA A.
Published: February 2008

A method is presented for rearing large colonies of viruliferous Sogatodes oryzicola, vector of the rice hoja blanca virus (RHBV). These colonies were used for field screening up to 10 000 rice breeding lines per season for resistance to RHBV. Uniform infection of check varieties in the field indicated that the method was adequate. Field release of vectors when plants were 14 days old resulted in satisfactory disease incidence, after 21 days, to distinguish lines segregating for resistance from lines uniformly resistant or susceptible. Various sources of resistance identified earlier continued to be resistant under the screening conditions. Progeny of lines identified as non‐segregating resistant continued as non‐segregating resistant. Resistant plants from lines segregating for resistance produced progeny lines that were segregating and non‐segregating. Ratios of resistant to susceptible plants in F1 progeny of three‐way crosses were consistent with earlier observations that RHBV resistance is a dominant character. The susceptibility of the commercial checks indicates that rice production in RHBV areas of tropical Latin America continues to be at risk from the virus. Virus‐resistant commercial cultivars resulting from this method should be available in 2 years.
Light quality effects on the appearance of tillers of different order in wheat (Triticum aestivum)
Authors: CASAL J. J.
Published: February 2008

Plants of Triticum aestivum cvs Norkin Pan 70, La Paz Inta, Buck Cencerro and Buck Cimarron were grown outdoors in individual pots with two sowing dates and irradiated at the end of the day either with red or far‐red light. In red‐treated plants the number of tillers was close to the potential calculated from the number of leaves on the main shoot but far‐red treated plants produced less tillers. The magnitude of the effect was larger for secondary and tertiary than primary tillers. Thus, the proportion of primary to secondary and tertiary tillers was larger in FR‐treated plants. Leaf sheath and lamina were longer under FR in the second sowing date, possibly due to warmer nights. These responses were greatly affected by the genotype. Significant differences in ear number were not found but in one of the sowing dates red‐light‐treated plants showed a lower grain number and yield than those treated with far‐red.
Field assessments of resistance to the aphids Sitobion avenae and Metopolophium dirhodum in old and modern spring‐sown wheats
Authors: SOTHERTON N. W. , LEE G.
Published: February 2008

Three ancient varieties of wheat and two modern spring‐sown cultivars were investigated in the field to assess their resistance to the cereal aphids Sitobion avenae and Metopolophium dirhodum; the monitoring of natural populations and detailed observations using clip‐cages were both undertaken.

The ancient variety Einkorn showed both antixenotic and antibiotic resistance to S. avenae, and antibiotic resistance to M. dirhodum. The resistance to S. avenae was greater than that to M. dirhodum.

The value of Einkorn as a component of a resistance‐breeding programme is discussed with reference to its agronomic and genetic characteristics and with reference to the pest status of cereal aphids.
Some effects of temperature during seed development on carrot (Daucus carota) seed growth and quality
Authors: GRAY D. , STECKEL JOYCE R. A. , DEARMAN JANE , BROCKLEHURST P. A.
Published: February 2008

The growth and development of carrot seeds cv. Chantenay Red‐cored Royal Chantenay at day/night temperatures of 20/10°C, 25/15°C and 30/20°C and subsequent seed performance were examined in 1984 and 1985.

An increase in temperature from 20/10°C to 30/20°C reduced mean weight per seed by 20% in 1984 and by 13% in 1985. There were no effects of temperature on endosperm + embryo weight, or on endosperm cell number but the weight of pericarp decreased with an increase in temperature. Seeds grown at the highest temperature had the largest embryos and the highest nitrogen, DNA and rRNA content; they germinated and emerged earlier, and gave higher percentage seedling emergence than those grown at the lowest temperature. There were no effects of temperature during seed growth on the rate of imbibition of water by seeds during the germination process.
Substituted benzoic and picolinic acids as foliar sprays against potato common scab
Authors: McINTOSH A. H. , BATEMAN G. L. , CHAMBERLAIN K.
Published: February 2008

Glasshouse tests on potato cv. Arran Banner measured the effects of single early foliar sprays of 18 substituted benzoic and two dichloropicolinic acids on the severity of common scab, caused by soil‐borne Streptomyces scabies.

The monosubstituted benzoic acids tested (25 mM) did not affect scab. However, anti‐scab action was shown by some 2,5‐disubstituted acids. Decreases in scab severity were about 35% from 1·6 mM 5‐bromo‐2‐chloro‐ and 2,5‐dimethylbenzoic acids, and over 50% from 1·6 mM 2,5‐dichloro‐, 2,5‐dibromo‐ and 5‐chloro‐2‐nitrobenzoic acids and from 0·05 mM 3,6‐dichloropicolinic acid (clopyralid), which is structurally similar to 2,5‐dichlorobenzoic acid.

None of the spray treatments affected yield or shape of tubers. No visible effects on foliage were caused by two of the benzoic acids active against scab (5‐chloro‐2‐nitro‐ and 2,5‐dimethyl‐), but the other active acids caused some distortion.

In tests of the six dichlorobenzoic acids against S. scabies in culture, the 2,5‐isomer (which was the most effective against the disease in plants) was one of the least toxic. With other 2,5‐disubstituted benzoic acids, it probably decreased scab indirectly by altering the response of the host to infection.
Studies on the transmission of velvet tobacco mottle virus by the mirid, Cyrtopeltis nicotianae
Authors: GIBB KAREN S. , RANDLES J. W.
Published: February 2008

The minimum acquisition period of velvet tobacco mottle virus (VTMoV) by its mirid vector Cyrtopeltis nicotianae was about 1 min, with an increase in the rate of transmission (i.e. proportion of test plants infected) for acquisition periods up to 1000 min. Pre‐acquisition starvation periods up to 18 h did not affect the rate of transmission. After an acquisition access period of 2 days, the minimum inoculation period was between 1 and 2 h and the rate of transmission increased with increasing inoculation time; when the acquisition access period was 1 h, or if vectors were fasted for 16 h after the 2 day acquisition, the rate of transmission was significantly lower. When mirids were transferred sequentially each day to a healthy plant after a 24 h acquisition feed, they transmitted intermittently for up to 10 days. Up to 50% of mirids transmitted after a moult and this was not due to the mirids probing the shed cuticles or exudates of infective insects. Mirids transmitted after a moult, following acquisition periods of 10, 100 or 1000 min.

C. nicotianae transmitted solanum nodiflorum mottle virus (SNMV), sowbane mosaic virus (SoMV) and southern bean mosaic virus (SBMV), but not subterranean clover mottle virus (SCMoV), lucerne transient streak virus (LTSV), tobacco ringspot virus (TRSV), galinsoga mosaic virus (GMV), nor nicotiana velutina mosaic virus (NVMV). Tomato bushy stunt virus (TBSV) was transmitted to 1/58 test plants.
Electronic recording of plant penetration by the cereal aphids Rhopalosiphum padi and Metopolophium dirhodum on resistant and susceptible wheat seedlings
Authors: SPILLER N. J.
Published: February 2008

Plant penetration by the aphids Rhopalosiphum padi and Metopolophium dirhodum was monitored using an electronic recording method. Recordings over 3 h showed that phloem ingestion was reduced on resistant wheat, when compared with a more susceptible species, but this trend was reversed when results from longer (12 h) experiments were used. Plant penetration by M. dirhodum was reduced by attachment to the electronic system, but the behaviour of R. padi was relatively unaffected. The results are discussed in relation to prospects for using electronic methods as a screening procedure.
Observations on the pathogenicity of Pasteuria penetrans, a parasite of root‐knot nematodes
Authors: DAVIES K. G. , KERRY B. R. , FLYNN C. A.
Published: February 2008

A simple test was used to determine whether or not Pasteuria penetrans spores would attach to 17 species of nematodes. All susceptible individuals had spores attached to their cuticles after 24 h of gentle agitation in suspensions containing 105spores/ml. Spores of P. penetrans from six populations of Meloidogyne only adhered to species of Meloidogyne and they adhered in greatest numbers to the species from which they had been originally isolated. Sonication of spores from infected females increased attachment but the effect was dependent on pH and whether the test was conducted in tap or distilled water. Invasion of tomato roots was reduced by up to 86% when, rather than using healthy juveniles, second‐stage juveniles bearing 15 or more spores were added to soil at high densities (1000 or 3000/plant); at low densities (500/plant) invasion was not significantly affected. The rate of development of M. incognita juveniles infected with P. penetrans was slower than that of healthy juveniles. The numbers of second‐generation of M. incognita were reduced by 82–93% when juveniles encumbered with 1–15 spores were added to soil instead of those bearing no spores. Pasteuria penetrans populations differed in their aggressiveness and when juveniles encumbered with the same number of spores from two populations were added to soil there were differences in the numbers of females that became infected. The implications of these results for the development of P. penetrans as a biological control agent are discussed.
Seasonal variation of morphological characters and growth in contrasting white clover populations
Authors: EAGLES C. F. , OTHMAN O. B.
Published: February 2008

The seasonal growth potential of contrasting white clover populations differing in leaf size and geographical origin was studied during the year in a cool glasshouse in the absence of freeze damage.

A Mediterranean population showed superior growth to all other populations during the cooler months of late autumn, winter and spring when it also had longer leaflets, petioles and internodes. In contrast, large leaf types of north European origin grew faster and had longer leaflets, petioles and internodes than the Mediterranean type during summer. A hybrid between these contrasting types showed an intermediate response with more uniform growth and expression of these morphological characters throughout the year.

The exploitation of this out‐of‐season growth potential by hybridisation of Mediterranean and north European genotypes followed by selection is discussed in the context of recent introductions of ecotypes from the Swiss Alps in which desirable combinations of good spring growth and winter hardiness have been identified.
Transmission of pangola stunt virus by Sogatella kolophon
Authors: GREBER R. S. , GOWANLOCK D. H. , HICKS S. , TEAKLE D. S.
Published: February 2008

A fijivirus causing minor enations, stunting, leaf notching, seed head deformity and excess tillering of Digitaria spp. was transmitted from naturally infected Digitaria ciliaris to D. ciliaris, D. decumbens and Urochloa panicoides by the planthopper Sogatella kolophon; 40–70% of insects transmitted after an incubation period of 15–21 days, and continued to transmit for up to 30 more days until death. Symptoms developed in test plants 30–50 days after inoculation. Sogatella longifurcifera failed to transmit the virus under similar conditions. Virus particles were present in roots, stems and leaves of infected plants, and particles were found in regular arrays and random aggregates in fat body cells of transmitting insects. Viroplasm and tubular structures were associated with these particles. Extracts from infective insects contained 10‐segment dsRNA when analysed by polyacrylamide gel electrophoresis. Virus survives over winter in planthoppers and D. ciliaris seedlings in frost‐free areas of coastal Queensland, but infected plants have debilitated root systems and compete poorly with healthy plants.
The assessment of the tolerance of partially resistant potato clones to damage by the potato cyst nematode Globodera pallida at different sites and in different years
Authors: DALE M. F. B. , PHILLIPS M. S. , AYRES R. M. , HANCOCK M. , HOLLIDAY M. , MACKAY G. R. , TONES S. J.
Published: February 2008

A range of potato cultivars and clones was grown at three sites infested with Globodera pallida in each of four years (1983 – 1986). Comparison of yields from nematicide treated plots with those of untreated plots provided estimates of yield losses due to G. pallida. The proportional yield losses were calculated for each genotype at each site as a measure of nematode tolerance. There were significant differences between genotypes with regard to tolerance of damage by G. pallida. There were also significant interactions between the different genotypes and the sites and years, but the interactions between years and genotypes represented only a small proportion of the observed variation. The interactions between sites and years indicate that not all of the genotypes behaved consistently between sites and years. The extent of yield losses caused by the nematodes varied significantly between sites. The implications of these results are discussed in relation to potato breeding programmes and assessing resistance and tolerance to G. pallida.
Genotypic responses of scab‐resistant apple cultivars/selections to two strains of Erwinia amylovora and the inheritance of resistance to fire blight
Authors: KORBAN S. S. , RIES S. M. , KLOPMEYER M. J. , MORRISEY J. F. , HATTERMANN D. R.
Published: February 2008

Apple cultivars and selections were tested for resistance to two strains of Erwinia amylovora following shoot tip inoculation in the greenhouse. Cv. Liberty was resistant to strain Ea 273, and Priscilla, Delicious and Coop 17 were highly resistant to strain Apple # 1. A significant genotype x strain interaction was obtained suggesting a differential host × pathogen interaction.

Segregation of seedlings derived from 16 controlled crosses after fire blight inoculation indicated that resistance to fire blight is quantitatively controlled with evidence for presence of dominant additive gene effects.
Biocontrol of Rhizoctonia crown and root rot of sugar beet by binucleate Rhizoctonia spp. and Laetisaria arvalis
Authors: HERR LEONARD J.
Published: February 2008

Two isolates of Laetisaria arvalis and 10 of binucleate Rhizoctonia spp. (BNR) from the Ohio sugar beet production area, were tested in the greenhouse and field for biocontrol of Rhizoctonia crown and root rot of sugar beet, caused by Rhizoctonia solani anastomosis group 2, type 2. L. arvalis was ineffective in standard greenhouse tests, and the single isolate used in the field was generally ineffective. Seven of 10 BNR isolates effectively controlled crown and root rot in greenhouse tests. Delayed application of biocontrol agents to plants 5 – 10 wk old was generally more effective than applications made at planting. A BNR isolate significantly reduced % plant loss and disease ratings and increased yield in a 1985 field test as compared with the control infested with R. solani alone. Two BNR isolates were effective in a 1986 field test and increased yields c. 22% in comparison to a L. arvalis treatment, which did not differ from the R. solani‐infested control. The Ohio binucleate Rhizoctonia isolates appear to have considerable potential as applied biocontrol agents and may play a role in the natural ecology of R. solani in the sugar beet production area of Ohio.
The inhibition of potato sprout growth by light.
Authors: MCGEE E. , BOOTH R. H. , JARVIS M. C. , DUNCAN H. J.
Published: February 2008

The effect of light intensity on sprout growth in seed potato tubers (Solanum tuberosum) was examined using diffuse daylight in Peru and diffuse artificial light at Glasgow. Mean temperatures below 20 °C produced strong sprout growth that was inhibited by both daylight and artificial light, at visible irradiances above 0.01 Wm‐2. The percentage inhibition of sprout growth increased linearly with the logarithm of the irradiance, 50% inhibition being at 0.04 ‐ 0.1 Wm‐2 provided that the temperature was suitable for substantial sprout growth in the absence of light.

Cultivar and temperature had very little effect on the 50% inhibition point. At high irradiances growth inhibition was up to 95%, but the sprout length was never reduced to zero; short, robust green sprouts remained. Sprout numbers were increased by daylight, but not by artificial light. Diffuse daylight also reduced the total weight loss from seed tubers during a storage season of 180 days. At mean temperatures above 20 °C., sprout growth in the absence of light was much reduced and the effect of light on sprout elongation was less obvious.
The inhibition of potato sprout growth by light.
Authors: MCGEE E. , BOOTH R. H. , JARVIS M. C. , DUNCAN H. J.
Published: February 2008

In an experiment with eight potato cultivars at Huancayo, Peru, storage of seed tubers in a prototype diffuse‐daylight store resulted in a mean 17% increase in the yield of the subsequent crop, and in more rapid emergence of six of the cultivars after planting, as compared with seed stored in darkness. The dark‐stored seed had very long sprouts that had to be removed at planting.

In two experiments at Glasgow, Scotland, seed tubers of four cultivars were stored at a range of temperatures in darkness and artificial light. At the time of planting, some of the light‐stored tubers were desprouted as well as the dark‐stored ones, so that the effect of desprouting could be distinguished from any direct effect of storage in darkness. Desprouting consistently delayed emergence and senescence of the crop and in most cases reduced its yield. In 1983 the yield reduction was greatest in the first early cV. Home Guard after storage at high temperature (22 °C), when it was associated with low stem numbers and incomplete emergence. In 1984 after light storage at still higher temperature (22/33 °C) and desprouting, this cV. behaved similarly, but the corresponding dark‐stored treatment yielded heavily after greatly delayed haulm senescence. CV. Desiree and, in 1984, cV. King Edward retained some apical dominance after storage at the lower temperatures and in some cases responded to desprouting with a small yield increase.

In general desprouting after high‐temperature storage reduced yields more than could readily be explained on the basis of the physiological age being reset to zero at planting.
Chemical retting of flax using chelating compounds
Authors: SHARMA H. S. SHEKHAR.
Published: February 2008

A wide range of concentrations of ethylenediaminetetra acetic acid (EDTA) was tested as a retting agent at a range of temperatures, pHs and stem: liquor ratios. Treatment of stems at 2 and 3 g/litre at 40 °C in a liquor ratio of 1:10 at pH 11 produced the finest and strongest fibre. Dried‐green stem retted slightly better than the glyphosate‐desiccated stem and after multiple retting with EDTA, Trilon TB and diethyltriaminepenta acetic acid (DTPA), the dried‐green stem produced the finest fibre. Trilon TB and DTPA retted better than EDTA and produced a high yield of fibres. The fluidity of fibres scutched from the dried‐green stem was lower than the fluidity of the fibres from glyphosate‐desiccated stem.
Studies on the biology and control of cavity spot of carrots
Authors: WHITE J. G.
Published: February 2008

Using a selective medium of corn meal agar with pimaricin and rifamycin, isolations from asymptomatic periderm of carrots grown on experimental plots or in commercial crops most frequently yielded the fast‐growing species Pythium intermedium, P. sylvaticum or P. ultimum. In contrast isolations from cavity spot lesions mostly produced the slow‐growing species P. violae and P. sulcatum. Following treatment of crops with metalaxyl + mancozeb, few isolations from asymptomatic periderm produced Pythium spp. and generally there was a reduction in the number of cavities. Treatment had little or no effect on size distribution of cavities. Cavity spot incidence was significantly less at higher pH values, fields of pH 8·0 and above producing carrots with little or no disease.
Variation in the sensitivity to metalaxyl of Pythium spp. isolated from carrot and other sources
Authors: WHITE J. G. , STANGHELLINI M. E. , AYOUBI L. M.
Published: February 2008

Over a 3‐yr period 261 isolates of 17 species of Pythium were tested for sensitivity to metalaxyl at concentrations of 5, 50 or 100 μ/ml. A wide range of responses was observed, from isolates where growth ceased at 5 μg/ml to those where growth at 100 μg/ml was similar to that of the untreated controls. In further tests isolates of 11 different species had ED50's < 1 μg/ml. A lower sensitivity was detected in isolates of six Pythium spp. where values in the range 1–10 μg/ml were obtained.

This lower sensitivity was not related to previous known use of metalaxyl. Three isolates of Pythium dissotocum from sites where the fungicide had been used repeatedly had ED50's > 100 μg/ml and were considered resistant. The resistance was stable over a 2‐yr period and isolates were cross‐resistant to furalaxyl, benalaxyl, ofurace, cyprofuram and oxadixyl. Increasing concentrations of metalaxyl reduced or prevented the production of zoospores by four species of Pythium, although when zoospores were produced, this was followed by the normal processes of encystment and germination. Culturing P. dissotocum on different sub‐lethal concentrations of metalaxyl for 18 wk did not induce a high level of resistance to the fungicide.
The ploidy of plants obtained from anther culture of cauliflowers (Brassica oleracea var. botrytis)
Authors: OCKENDON D. J.
Published: February 2008

Anther culture of four cultivars of autumn cauliflower gave embryo yields of 100 embryos (per 100 anthers cultured) for one cultivar, eight embryos for a second cultivar, and almost zero for the two other cultivars. From 986 embryos which were grown on, 418 plants were regenerated. The ploidy of the regenerants was assessed by measuring guard cell lengths, pollen size, and by chromosome counts at meiosis. Only 1% of the regenerants were haploid, 41% diploid, 5% triploid and 53% tetraploid. One octoploid plant was also found. The results are discussed in relation to equivalent results for Brussels sprouts, and the use of anther culture in the breediing of cauliflowers.
Light‐induced postharvest regreening of pummelo fruit*
Authors: SAKS YOLANTA , WAKS YEHOSHUA , WEISS BATIA , FRANCK ANDRE , CHALUTZ EDO
Published: February 2008

Regreening was observed and measured in harvested pummelo fruit stored in the light. At temperatures of 22 ‐ 28°C, regular daylight was sufficient for regreening to occur. The addition of continuous fluorescent light intensified the process. Pre‐stored fruit held in darkness at 11°C and non‐stored fruit responded to both light conditions in a similar manner. Electron microscopy has shown that globular chromoplasts revert to chloroplasts during regreening. The similarities between regreening processes in preharvest and postharvest fruits are discussed.
Influence of post‐flowering temperature on seed development, and subsequent performance of crisp lettuce
Authors: GRAY D. , WURR D. C. E. , WARD J. A. , FELLOWS JANE R.
Published: February 2008

Crisp lettuce plants cv. Saladin were grown from the time they started flowering, at 20/10°C (16 h day, 8 h night), 25/15°C and 30/20°C in glasshouses on two occasions in 1985.

Yields of seed increased from, on average, 15 g to 27 g and then fell to 20 g per plant with progressive increases in temperature. The number of mature florets per plant increased with temperature but the number of seeds per mature floret was lower at 20/10°C and 30/20°C than at 25/15°C. An increase in temperature reduced mean seed weight by up to 45%, seed volume by 15%, cell numerical volume density (Nv) by 27% and the number of cells per seed by 39%. Percentage seed germination reached a maximum early in seed development at the stage when the pappus appeared through the involucral bracts. Differences in percentage germination and vigour of seeds (slope test) from different temperatures were accounted for largely by the effects on mean seed weight. However, when germinated at 30°C seeds produced at 30/20°C germinated more readily than those produced at 25/15°C or 20/10°C. Seed vigour gradually increased with an increase in the length of storage after harvest, reaching a maximum after 260 days. In general, seeds produced at 25/15°C exhibited a greater variation in numbers of seeds per floret, Nv, seed weight, times of seedling emergence, seedling and mature head weight than seeds produced at lower or higher temperatures.
A study of the optimum drying conditions for cabbage seed following selection on the basis of a newly‐emerged radicle
Authors: FINCH‐SAVAGE W. E. , McKEE J. M. T.
Published: February 2008

A series of experiments were carried out to study the effects of different drying regimes on the survival of newly‐germinated (radicle emerged 0·5‐1·5 mm through the seed coat) cabbage seeds and to establish a treatment for reducing the moisture content of these germinated seeds. A preliminary surface‐drying step proved necessary to avoid seed agglutination during the main drying stage. Of the drying regimes compared both viability and vigour were most effectively maintained in air, conditioned to between 20 and 30°C and with 80% r.h., flowing through the seeds at 0·25 m s‐1. Under these conditions, the viability and vigour of newly‐germinated seed was maintained during drying to an equilibrium moisture content of c. 14%. At this moisture content further radicle growth was prevented and seeds remained free‐flowing and separate for sowing or for further treatment.
Control of potato gangrene by thiabendazole in relation to time of harvest after haulm destruction and site of production
Authors: CARNEGIE S. F. , HIDE G. A. , RUTHVEN A. D. , LINDSAY D. A. , ADAMS M. J.
Published: February 2008

The efficiency of thiabendazole in controlling gangrene on potato tubers harvested on different dates was assessed over two years in Scotland (East Craigs) and England (Rothamsted). At East Craigs the incidence of gangrene on wounded and cold‐stored tubers was greater than on those tubers kept at ambient store temperatures and graded in January, but the assessments were correlated. The incidence of gangrene increased with delay in harvest after haulm destruction although the pattern differed with year and site. Dipping tubers in thiabendazole or sodium hypochlorite almost eliminated gangrene on all harvest dates at Rothamsted but at East Craigs the incidence of gangrene on dipped tubers was much greater and tended to increase the longer the interval between haulm destruction and harvest. Furthermore, dipping tubers in thiabendazole was much more effective than spraying even though the fungicide residues were twice as large with the latter treatment. All 43 isolates of Phoma foveata collected in Scotland were sensitive to thiabendazole in agar plate tests. The results are discussed in relation to disease development at each of the sites.
Narcissus late season yellows potyvirus: symptoms, properties and serological detection
Authors: MOWAT W. P. , DUNCAN G. H. , DAWSON SHEILA
Published: February 2008

Narcissus late season yellows virus (NLSYV) was obtained, apparently unmixed with other viruses, in selected naturally infected narcissus plants. The virus was not transmitted by manual inoculation to any of the 12 herbaceous species tested but was transmitted by Myzus persicae to virus‐tested narcissus plants, which then developed symptoms characteristic of late season yellows. Typically, symptoms develop late in the growing season but their expression is unreliable. NLSYV particles, which measured c. 750 ± 12 nm, were purified from fresh leaf extracts of narcissus in 0·3 m sodium citrate containing 10 mm sodium EDTA and 10 mm sodium DIECA by differential centrifugation followed by clarification with diethyl ether, gel filtration and isopycnic banding in caesium sulphate. Using antibodies from antisera prepared to virus particles, NLSYV was detected by ELISA in 14 of the 18 cultivars examined and nine seemed totally infected. Detection of the virus by immunosorbent electron microscopy was as sensitive as by ELISA but neither test detected all infections. The virus was detected by ELISA only in samples collected after flowering and capsid antigen concentration was greatest in the distal region of leaves. The reliability of detection depended on the cultivar. Immuno‐electron microscopy tests confirmed the occurrence of a distinct potyvirus, presumably narcissus degeneration, in narcissus cv. Grand Soleil d'Or, failed to detect any virus other than NLSYV in narcissus plants affected by white streak disease, and showed that NLSYV is related to three of five other potyviruses tested.
The effect of partially resistant potato clones and aldicarb on the multiplication of the potato cyst nematode Globodera pallida in field trials
Authors: PHILLIPS M. S. , DALE M. F. B. , GREEN D. I. , HANCOCK M. , HOLLIDAY M. , LACEY C. N. D. , TONES S. J.
Published: February 2008

Potato cultivars with different degrees of resistance to Globodera pallida (PCN) were trialled at three infested sites in 1983, 1984 and 1985. These trials were primarily intended to assess the effects of PCN damage on the yield of tubers and consequently the sites chosen had high initial population densities of G. pallida. The population density of G. pallida was determined from samples taken both pre‐planting and post‐harvest and results showed that there were significant differences between the clones in the nematode multiplication rates. Although actual rates of multiplication varied between sites the relative differences between clones were maintained across sites. Under the susceptible control cultivars the populations generally increased even in the presence of nematicide. The partially resistant clones gave best control, as measured by nematode multiplication, at the sites with the highest initial population densities but gave good control at all sites when treated with nematicide irrespective of initial population density. The role of partial resistance in integrated control systems and the effectiveness of nematicides against G. pallida is discussed.
A survey of insect parasitic nematodes in Northern Ireland
Authors: BLACKSHAW R. P.
Published: February 2008

A survey of insect parasitic nematodes was carried out in Northern Ireland between November 1986 and June 1987. A total of 1093 soils were examined using Galleria mellonella larvae as bait. Nematodes were recovered from 41 of these soils. The rate of recovery declined from February onwards and possible reasons for this are discussed. Clay and clay loam types accounted for 56·1% of the survey samples but only 9·8% of the recovered nematode populations. Loams comprised 39·6% of samples and 85·4% of nematodes, indicating a greater likelihood of recovering insect parasitic nematodes from lighter soils. The nematodes were also recovered from peat soils (4·3% of samples and 4·9% of nematodes). All the recovered isolates were Neoaplectana bibionis.
A photographic technique for investigating the splashing of water drops on leaves
Authors: MACDONALD O. C. , McCARTNEY H. A.
Published: February 2008

The formation of splash from water drops falling onto bean leaves was investigated by multiple exposure flash photography. A relatively simple technique was developed which recorded up to four images at 2 ms intervals, of a splash on one photograph. The images were recorded on colour reversal film, and the flash sequence was colour coded to aid the interpretion of the superimposed images. Analysis of the photographs allowed measurement of the initial speed and angle of ejection of different sized splash droplets. Droplets were ejected at speeds of up to about 10 m s‐1although most speeds were less than about 3 m s‐1, and small droplets tended to travel faster than large ones. Droplets were ejected at all angles but the majority were ejected almost horizontally; there was little correlation between droplet size and angle of ejection. Deposition patterns estimated from calculated droplet trajectories compared well with measured ones.
Systemic infection of black currant flowers by Botrytis cinerea and its possible involvement in premature abscission of fruits
Authors: McNICOL R. J. , WILLIAMSON B.
Published: February 2008

Emasculated flowers of several black currant cultivars were pollinated and then inoculated with dry conidia of Botrytis cinerea in the field and glasshouse. The infection of pistils was examined by U.V. fluorescence microscopy and the incidence of premature flower abscission recorded. Conidia germinated in the stigmatic fluid in all cultivars and hyphae spread symptomlessly throughout the style to infect the pericarp and ovules.

Of six cultivars inoculated in the field, cv. Ojebyn was the most, and cv. Ben More the least resistant to flower shedding. Natural infection of stigmas by B. cinerea was common in the field and a high proportion of apparently healthy non‐inoculated flowers which abscissed were found to contain infected ovules. Fewer flowers abscissed if inoculations were made 6 days after pollination. Symptomless or latent infection of black currant flowers by B. cinerea may be a contributory cause of premature abscission of developing fruits, or ‘running‐off’, recorded in these experiments.
Stem canker (Rhizoctonia solani) on five early and seven maincrop potato cultivars. II Effects on growth and yield
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 solani during planting in field experiments to simulate severe seed infection. The size of foliage was assessed during June‐August and tuber yields recorded during growth and at harvest in October.

Stem canker delayed shoot emergence, decreased the number and length of stems and caused increased variation in stem length; these effects were greatest with Maris Peer and Arran Comet (early cultivars) and King Edward and Pentland Squire (maincrop cultivars). Total weight of foliage was decreased, especially with earlies, dry matter of stems increased and the proportion of foliage on lateral stems increased.

With the early cultivars, tuber yield from sprouted Maris Peer seed 11 wk after planting in 1983 was decreased by 24%, and 13 wk after planting in 1984 yields were decreased by 42% (Maris Peer), 40% (Ulster Sceptre), 34% (Estima), 30% (Arran Comet) and 17% (Ulster Prince) with sprouted seed and by 20, 29, 53, 39 and 28% respectively with non‐sprouted seed. Decrease in total yield at harvest in October averaged 13% with sprouted seed and 10% with non‐sprouted seed. In all cultivars the weight of small tubers was decreased and with Estima the weight of large tubers was increased.

Tuber bulking was also delayed with all maincrop cultivars and at harvest yields from sprouted King Edward seed were decreased by 13% in 1983 and by 16% (sprouted seed) and 23% (non‐sprouted seed) in 1984; yields of Pentland Squire were decreased by 5, 16 and 21% respectively. Yield losses with other cultivars ranged from 5–13% with sprouted seed and 0–16% with non‐sprouted seed. The yields of small tubers were decreased with all cultivars and yields of large tubers were increased with Pentland Squire, Pentland Crown and Cara.
Inheritance of adult plant resistance to powdery mildew in swedes
Authors: BRADSHAW J. E. , GEMMELL DOROTHY J. , WILLIAMSON CYNTHIA J.
Published: February 2008

A complete diallel set of crosses, including selfs, was produced from 11 inbred lines of swedes and assessed for adult plant resistance to powdery mildew in a replicated field trial. The plants were inoculated with powdery mildew spores on 23 July 1987. Traces of mildew were visible on 3 August. By 14 September the most susceptible inbred line had 95% of its leaf area infected, whereas the three most resistant lines derived from cvs Bangholm Dima (two lines) and Bangholm Magres (one line) had only 5%. Resistance was controlled by partially recessive genes. There was no evidence of maternal effects. The implications for breeding inbred and F1 hybrid swede cultivars are discussed.