bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of temperature on light enhanced glycoalkaloid synthesis in potato
Authors: PERCIVAL G C , HARRISON J A C , DIXON G R
Published: February 2008

The influence of temperature on total glycoalkaloid (TGA) synthesis in tubers exposed to light (250 jumol m“2 s”2 PAR, Photosynthetically Active Radiation) or dark environments for 96 h was examined in three potato cultivars. Following 96 h light or dark the tubers were stored without light at 5°C or 24°C and TGA concentrations monitored over the subsequent 30 and 90 days. Exposure to light and cultivar were found to be major factors influencing TGA concentrations; temperature had no significant effect. TGA content in illuminated tubers of cvs ‘Pentland Hawk’ and ‘Kerrs Pink’ were significantly higher (P < 0.01) compared with tubers placed in the dark. TGA concentrations in cv. ‘Desiree’ increased significantly only following exposure to light at low temperatures (P < 0.05).

Removal of tubers from storage at 5°C and immediate illumination at 24°C altered the ratio of glycoalkaloids in cvs ‘Pentland Hawk’ and ‘Kerrs Pink’. Regardless of cultivar and storage temperature TGA concentrations were higher at the end of the storage period compared with initial TGA concentrations. During storage TGA concentrations fluctuated widely and gradual accumulation of glycoalkaloids with time was rarely demonstrated except in cv. ‘Desiree’. Tubers stored at 24°C accumulated higher TGA concentrations than those stored at 5°C in cv. ‘Kerrs Pink’ but not in cvs ‘Pentland Hawk’ and ‘Desiree’. Tubers of cv. ‘Kerrs Pink’ exposed to light prior to storage accumulated glycoalkaloids more rapidly than unexposed tubers during storage at 24°C and occasionally at 5°C. Light enhanced glycoalkaloids are not degraded over time.
Transmission of the mycoparasite Coniothyrium minitans by collembolan Folsomia Candida (Collembola: Entomobryidae) and glasshouse sciarid Bradysia sp. (Diptera: Sciaridae)
Authors: WHIPPS J M , BUDGE S P
Published: February 2008

Folsomia Candida was maintained on potato dextrose agar (PDA) plates precolonised by the mycoparasite Coniothyrium minitans for 3 yr but the sciarid Bradysia sp. survived for a maximum of only three generations. Collembolans and sciarid larvae from these cultures were able to transmit C. minitans to uninoculated PDA plates through the survival of spores in faecal pellets. Adult and larval sciarids also transmitted C. minitans from PDA culture to uninoculated PDA plates by contamination on the cuticle. In soil and sand both sciarids and collembolans were able to transmit C. minitans from C. m/m'tans‐inoculated to uninoculated sclerotia of Sclerotinia sclerotiorum. Inoculation of sclerotia with C. minitans enabled greater populations of larger collembolans to develop. In the glasshouse where C. minitans had been applied to the soil, one adult sciarid and four collembolans out of 70 and 101 insects collected respectively yielded C. minitans on placement onto PDA + Aureomycin.
The effectivity of Tilletiopsis albescens in biocontrol of powdery mildew
Authors: KNUDSEN INGE M B , SKOU J P
Published: February 2008

Tilletiopsis albescens grows well on powdery mildew fungi inoculated on barley or cucumber leaves and causes collapse of the colonies. Application of ballistospores or cut mycelium was equally effective for biocontrol, and the effectiveness tended to increase exponentially with the concentration of germinating units (conidia and cut mycelium) applied. Seventy percent relative humidity or more is required for effective biocontrol. Two applications of T. albescens in the period from 3 days before to 3 days after inoculation with powdery mildew were more effective than one. Applications before inoculation or 7 days after inoculation with powdery mildew had little effect. T. albescens followed the powdery mildew as it was disseminated to uninoculated leaves, but this did not result in an effective biocontrol. The potential for using T. albescens for biocontrol of powdery mildews is discussed.
Flower and nectar attributes of pepper (Capsicum annuum L.) plants in relation to their attractiveness to honeybees (Apis mellifera L.)
Authors: RABINOWITCH H D , FAHN A , MEIR TAL , LENSKY Y
Published: February 2008

Flower morphology, nectary structure, nectar traits and rates of honeybee foraging on pepper plants were studied. The nectary appears as swellings on the basal part of the ovary. The nectariferous cells are smaller and denser than the neighbouring parenchyma. Stomata are present in the nectary epidermis, but do not appear on the other parts of the ovary epidermis. Seven pepper breeding lines were grown near a bee yard in Rehovot. Five to six fold differences in nectar volume were found between the extreme genotypes. Nectar volumes were higher during noon and afternoon hours, as compared with morning hours. High correlation coefficients between nectar volume and sugar concentration were found. These were significant for the four high nectar yielding genotypes, ranging between r = 0.65 to r = 0.94. Male‐fertile flowers produced more nectar and higher sugar concentration than sterile ones. Skewed distribution was observed in nectar volume of F2 populations, but relatively low heritability values were calculated.

Pepper nectar contains fructose and glucose only. The former occupies 52–82 % of the total sugar content. Pepper genotypes varied in frequency of honeybee visits and significant correlation between sugar quantity and number of honeybee visits per flower was evident. Fertile pepper flowers are not very attractive to honeybees and male‐sterile flowers are even less so. The considerable variation in nectar characteristics can be exploited to increase attractiveness to honeybees, thus facilitating bee pollination in commercial production of F1hybrid seeds and improve fruit quality.
Fungicidal control of damping‐off and seedling root rot in Brassica species caused by Rhizoctonia solani in the growth chamber*
Authors: KATARIA H R , VERMA P R , RAKOW G
Published: February 2008

Eight fungicides (benodanil, carboxin, cyproconazole, fenpropimorph, fur‐mecyclox, iprodione, pencycuron and tolclofos‐methyl) were evaluated, under growth chamber conditions, as seed treatments against pre‐emergence damping‐off and post‐emergence seedling root rot in six Brassica species. Five cultivars of B. rapa, four cultivars of B. juncea, four cultivars of B. napus and one cultivar/ strain from each of B. carinata, B. nigra and B. oleracea were grown in soilless mix infested with an isolate of Rhizoctonia solani AG‐2‐1. B. nigra and B. juncea were considerably less susceptible to R. solani than the four other species. Cyproconazole at 0.05‐0.1 g a.i./kg seed and the other fungicides at 2–4 g a.i./ kg seed provided almost complete control of pre‐emergence damping‐off in most Brassica species and their cultivars. Their efficacy varied against the post‐emergence seedling root rot. Furmecyclox, iprodione, tolclofos‐methyl and pencycuron consistently gave good control of seedling root rot in all Brassica species and their cultivars. Benodanil and fenpropimorph provided moderate control, and carboxin and cyproconazole gave poor control against root rot. Efficacy of carboxin, cyproconazole, benodanil and fenopropimorph against seedling root rot varied significantly (P ≤ 0.05) among cultivars within a Brassica species.
Fungi and Gram‐negative bacteria as soilborne minor pathogens of goat's rue (Galega orientalis Lam.)
Authors: VALKONEN JARI P T , von HEIROTH WIPATORN , SAVELA MERVI‐LEENA
Published: February 2008

Fungi and Gram‐negative bacteria were isolated from inside the roots of field‐grown goat's rue (Galega orientalis). Fungi were isolated from three plants out of a total of 45 tested. Two multinuclear Rhizoctonia solani isolates were identified to the anastomosis group 5 (R. solani AG‐5‐Gal) using pairings with known AG test cultures. One fungal isolate was identified to Phoma chrysanthemicola. Gram‐negative bacteria were isolated from three plants out of 25 tested. They were identified using classical methods, the BIOLOG identification system based on the utilisation of 95 different carbon sources, and the MIDI system for the analysis of whole cell fatty acids. The two latter systems were computer‐associated and utilised an extensive reference library of isolates. One bacterial isolate was identified as Enterobacter agglomerans and two isolates as Pseudomonas marginalis.

R. solani AG‐5‐Gal reduced the emergence of Lupinus luteus, L. polyphyllus and french bean (Phaseolus vulgaris) and the growth of broad bean (Viciafaba), L. luteus and french bean, but did not cause obvious damage in goat's rue and pea (Pisum sativum). However, R. solani AG‐5‐Gal was re‐isolated from the roots of all the test plant species following inoculation. P. chrysanthemicola reduced the emergence of L. polyphyllus and the growth of goat's rue, french bean and broad bean, and it was re‐isolated from all of the test plant species (except for french bean) following inoculation.

All the bacteria reduced the emergence of french bean, but not that of goat's rue and pea, when applied to the soil. When the roots were dipped into bacterial suspension, all the bacteria damaged french bean and L. polyphyllus. Additionally, P. marginalis JV3 damaged goat's rue and red clover. The pathogenicity of the fungi and bacteria were not changed when they were double‐inoculated in pairs, except for R. solani AG‐5‐Gal and P. marginalis JV2 which reduced the emergence of goat's rue when inoculated together but not when inoculated separately.
The peel of plantain and cooking banana fruits
Authors: BURDON J N , MOORE K G , WAINWRIGHT H
Published: February 2008

The peel of the plantain and cooking banana fruit protects the edible pulp from the surrounding environment. The peel of those cultivars examined contained 85–90% water and between 28 and 60 mg dry weight cm‐2 surface area. The ratio of fruit pulp to peel fresh weights differed between cultivars (1.18‐2.28). The surface area of the fruit can be determined from the fresh weight using regression equations for individual cultivars or for all cultivars combined. The stomatal density was generally higher at the fruit tips than at the mid region. Significant differences in stomatal length and density were identified between cultivars although no trends existed between plantains and cooking bananas. There was little difference in the quantity of epicuticular wax on plantains whereas there were differing amounts on cooking bananas. Differences in wax composition between cultivars and for wax extracted with hot or cold chloroform were identified. Removal of the epicuticular wax with chloroform accelerated the rate of weight loss. The use of hot chloroform increased both the amount of wax removed and also the rate of weight loss. The effect of removing the epicuticular wax on water loss is discussed and illustrated with scanning electron micrographs.
Genetic variation in populations of the terrestrial planarian Artioposthia triangulata (Dendy), and evidence for passive dispersal in Northern Ireland
Authors: STEWART VALERIE I , BLACKSHAW R P
Published: February 2008

Genetic variation in 12 populations of the terrestrial planarian Artioposthia triangulata from Northern Ireland and one in the Republic of Ireland were assessed using starch‐gel electrophoresis. Seven enzymes ‐ adenylate kinase, aspartate aminotransferase, enolase, malate dehydrogenase, phosphoglucose isomerase, phosphomannose isomerase and superoxide dismutase ‐ provided consistent, resolved stains. Coefficients of genetic identity were similar for all comparisons suggesting that the populations did not belong to distinct taxa. There was no relationship between genetic distance and geographic distance for populations, thus confirming the role of passive dispersal in the spread of A. triangulata. Average percentage polymorphic loci and mean heterozygosities were higher in the east of the Province (41.4% and 0.240), than the west (37.5% and 0.185) suggesting that the planarian had spread westwards after an initial colonisation in the east.
A comparison of sampling methods for bibionid larvae (Diptera: Bibionidae) in grassland
Authors: BLACKSHAW R. P. , D'ARCY‐BURT S.
Published: February 2008

Three extraction methods were compared for the recovery of bibionid larvae from grassland soil samples. Only wet‐sieving followed by flotation in a saturated salt solution yielded bibionids. No larvae were recovered either with modified Tullgren funnels or by slow immersion of soil cores into a saturated salt solution. The efficiency with which larval bibionid populations can be estimated is poor. Generally, smaller cores yielded more larvae per volume of soil. Most bibionids were found in the top 4 cm of soil. It is concluded that 10 cm diameter and 6–8 cm deep soil cores are an acceptable compromise between efficiency and sampling effort but sample size will largely be determined by the resources available for processing of samples.
Susceptibility of western flower thrips, Frankliniella occidentalis (Pergande) to fumigation with methyl bromide
Authors: MACDONALD O. C.
Published: February 2008

All life stages of the western flower thrips (Frankliniella occidentalis Pergande) were tested for their response to the fumigant methyl bromide and dose response curves were established. Pseudo‐pupae were the most tolerant stage with a calculated LD99 of 53.1 mg litre“1 h at 15oC with a gas concentration of 13.5 mg litre”1, but no survivors were found in any test above a concentration time product of 40 mg litre“1 h. Standard 4 h fumigations achieving a CTP of 54 mg litre”1 h that are used to control other pests are therefore likely to give very high levels of control of western flower thrips.
Epidemiological studies on the stunt disease of highbush blueberry
Authors: TOZZP D C MAESO , RAMSDELL D. C. , TABOADA O. , LEE I ‐M , DAVIS R. E.
Published: February 2008

Population levels of Scaphytopius spp., possible sharpnosed leafhopper vectors of blueberry stunt disease (BBSD), were monitored during 1989,1990 and 1991, using yellow sticky traps and a D‐Vac power aspirator. Scaphytopius magdalensis (Prov.), S. frontalis (Van D.) and 5. acutus (Say) had two population peaks, one after the petal fall stage and a larger second peak in late Summer to early Autumn. Healthy cv. Bluecrop highbush blueberry (Vaccinium corymbosum L.) plants were placed under stunt‐diseased bushes in the field for 2‐wk periods during 1989 and 1990. These plants and some of the leafhoppers trapped during 1990 and 1991 were tested for mycoplasma‐like organism (MLO) infection with a DNA probe that detected BBSD‐associated MLO. The percentage of plants and the number of Scaphytopius spp. that were MLO‐positive tended to follow the same bimodal distribution found in the population studies. BBSD transmission tests were performed with Scaphytopius spp. collected from the field. Stunt‐related MLO transmission was achieved with S. magdalensis, S. acutus and 5. frontalis.
Multiplication and distribution of iris severe mosaic virus in secondarily‐infected iris bulbs after stress induced by heat and wounding
Authors: VLUGT CORNELIA I M VAN DER , LOHUIS HENDRICUS , DIJKSTRA JEANNE , MARQUART ARNOUD , GOLDBACH ROB W. , BOONEKAMP PIET M.
Published: February 2008

In freshly‐lifted iris bulbs infected with iris severe mosaic virus (ISMV), virus was not always detected in the basal plate and rarely in bulb scale tissue. After exposing the bulbs to stress (wounding or high‐temperature treatment) the sensitivity of virus detection was enhanced. The improved detection of viral antigen after local stress (wounding) coincided with an increase of viral RNA synthesis. When general stress (high‐temperature treatment) was applied, the virus could be reliably detected in the basal plate, and usually in vascular bundles and surrounding tissue. Virus was detected in the upper part of the bulb scale when such tissues were detached from the basal plate. Thus, virus must have been present in the scales in localised spots, albeit at a very low concentration, and multiplication is likely to be the main factor involved in the improved sensitivity of viral detection. The distribution of ISMV in the bulb after local or general stress treatment is discussed.
Characterisation and serology of virus‐like particles associated with faba bean necrotic yellows
Authors: KATUL UNA , VETTEN H. J. , MAISS E. , MAKKOUK K. M. , LESEMANN D‐E , CASPER R.
Published: February 2008

A disease showing chlorosis, leaf rolling and stunting in Vicia faba and other legumes was observed in West Asia and North Africa during 1987–1988. The putative causal agent could not be transmitted mechanically, but could be transmitted by aphids, most efficiently by Acyrthosiphon pisum, in the persistent manner. Further studies revealed isometric virus‐like particles (VLPs) closely associated with the disease, although their infectivity could not be demonstrated by membrane feeding. These particles, measuring c. 18 nm in diameter and containing a capsid protein of about 22 kDa and ssDNA of about 1 kb, are hereafter designated faba bean necrotic yellows virus (FBNYV). A high proportion of circular nucleic acid molecules of about 0.9 kb were visualised by electron microscopy. Hybridisation analysis of cloned viral DNA suggests that the circular genome is larger than 1 kb and consists of several components of similar size. An antiserum produced against FBNYV was used in ELISA, immunoelectron microscopy (IEM) and Western blot experiments for virus detection in aphids and field samples and for serological comparison with other viruses. Weak heterologous reactions between FBNYV and subterranean clover stunt virus (SCSV) were detected in IEM, but could not be confirmed in ELISA or Western blots. No serological relationship to banana bunchy top virus (BBTV) was detected. Using a direct tissue blot immunoassay (TBIA), FBNYV was detected in vascular tissue of infected faba bean leaves and stems.
A model of the competitive relationships between R. cochinchinensis and Z. mays
Authors: BRIDGEMOHAN PURAN , McDAVID CHARLES R.
Published: February 2008

An understanding of the competitive relationship between weed and crop can be used in assessing what physiological aspects of the association can be exploited in the control of the weed. Field and greenhouse studies were conducted with Z. mays L. and Rottboellia cochinchinensis (Lour.) W D Clayton using a modified replacement series model in which the overall weed crop density in each treatment was maintained as a constant, but the proportion of the two species varied. The results indicated that the crop had greater competitive ability (Kmr) than the weed even at increasing weed densities. Under field conditions, the values of the Plant Relative Yield (PRY) indicated that severe specific competition was occurring and suggested that some environmental factor was limiting, while the Relative Yield Total (RYT) suggest that either the crop and the weed were exploiting the resources in mutual antagonism or that allelopathy was occurring. The limiting environmental factor that both species exploited in mutual antagonism in the field was light under conditions of adequate soil moisture and nutrients.
Inbred line versus Ft hybrid breeding in swedes (Brassica napus L. var. napobrassica Peterm)
Authors: BRADSHAW J. E. , WILSON R. N.
Published: February 2008

In 1989 seven F[hybrid swedes were produced in polythene tunnels. The female parent was an inbred line derived from cv. Ruta 0tofte, and made self‐incompatible with an S‐allele introduced by backcrossing. Three more hybrids were produced in 1990 in a similar way with an inbred line from cv. Criffel as female parent. In trials in Dundee over the period 1990 to 1992, better parent heterosis for dry matter yield in the hybrids ranged from 1.9% to 19.2%. There was no such heterosis for dry matter percentage nor for mildew resistance.

The highest yielding hybrid was the one between the Criffel line and an inbred line from cv. Magres. It averaged 9.9% heterosis over the two years 1991 and 1992, outyielded seven commercial cultivars, but had a lower yield (12.3 t/ha) than an F6 line SS5 (13.3 t/ha) derived from the cross between the Criffel and Magres lines by pedigree inbreeding with selection.

It is concluded that high yielding heterotic F/s should be the starting point rather than the finishing point of swede breeding programmes, and that research into breeding methods should concentrate on improving the efficiency of pedigree inbreeding following hybridisations, rather than on ways of producing Fj hybrids.
Comparative studies of light leafspot (Pyrenopeziza brassicae) epidemics on the growth and yield of winter oilseed rape
Authors: JEFFERY D C , JENKINS P D , JONES D GARETH
Published: February 2008

Comparisons of epidemics of light leafspot of differing duration and time of initiation were made in two experiments using a single cultivar of Brassica napus. Fungicide was applied before introduction of disease to prevent infection or some time after inoculation to stop further disease development. In the first experiment, substantial reductions in green leaf area and total plant dry‐matter were found at flowering when disease was introduced in the autumn or in January. Plant dry weight at maturity was also greatly reduced in these treatments. The detrimental effect of an epidemic initiated in the autumn was avoided to a large extent if fungicide application began in February. Epidemics initiated in March had only small effects on final dry‐matter yield. Seed yield was negatively correlated with the length of the epidemic. In a second experiment, early epidemics initiated in the autumn were halted after different time intervals. Commencing fungicide application even as early as December failed to prevent some loss of dry weight at flowering. At maturity, however, dry weight and seed yield were reduced significantly when fungicide application was delayed until February. Failure to control the disease resulted in a 46% loss of seed yield.
Amplification of plasmid DNA to detect plant pathogenic mycoplasmalike organisms
Authors: GOODWIN P H , XUE B G , KUSKE C R , SEARS M K
Published: February 2008

The polymerase chain reaction (PCR) was employed to develop a specific assay for plant pathogenic mycoplasmalike organisms (MLOs). A cloned fragment of a plasmid from a severe strain of western aster yellows (AY)‐MLO was sequenced to identify oligonucleotide primers for PCR. Amplified DNA fragments of the predicted size were obtained from DNA extracted from plants and insects infected with pear decline MLO, beet leafhopper‐transmitted virescence agent, elm yellows MLO and several AY‐MLO strains. No amplification occurred from healthy leafhopper or plant DNA. The PCR‐based assay was over 500 times more sensitive than a _tilized_tion‐based assay which _tilized a cloned AY plasmid fragment as a probe. With the PCR‐based assay, MLOs could be detected using DNA samples of leafhoppers that were only crushed and boiled in buffer. Amplification of the target DNA was confirmed by digestion of the PCR product with Mbo I which yielded predicted sized fragments for all MLO strains except Bradford AY and eastern AY. Sequencing the PCR product from elm yellows and eastern AY‐MLOs revealed greater than 90% homology, and the failure to restrict the PCR product with Mbo I was due to a single base change in the restriction endonuclease site. The ability of the assay to detect a wide range of MLOs with minimal sample preparation and high sensitivity will be useful in epidemiological studies of MLO‐caused diseases.
Effect of dinitroaniline herbicides on rhizobia, nodulation and N2(C2H2) fixation of four groundnut cultivars
Authors: DURGESHA M
Published: February 2008

Field, greenhouse and laboratory investigations were conducted to determine the effect of four dinitroaniline herbicides on rhizobia, nodulation and nitrogen fixation of four groundnut cultivars. Benefin, dinitramine and nitralin used at recommended levels decreased nodule dry weight, nitrogenase activity and total nitrogen of groundnut tops and pod yield in three cultivars Kadiri 71‐1, Kadiri‐2, ICGS‐11 and not for a fourth cultivar, Kadiri‐3 of groundnut (Arachis hypogaea L.), but fluchloralin used at the recommended level increased the nodulation rate, nitrogenase activity and total nitrogen of groundnut tops and pod yield compared to untreated plants. Studies were conducted in vitro to determine the relative toxicity of the herbicides on four Rhizobium strains isolated from the nodules of four cultivars of groundnut. It was found that various strains of rhizobia differ in their sensitivity to different rates of the herbicides tested. Carbon dioxide exchange rate (CER) of all the cultivars which received herbicide treatment was measured at different time intervals to determine the relationship between photosynthesis and inhibition of nodulation. The lack of adverse effect on the CER of four cultivars when treated at recommended concentrations indicated that nitrogen fixation was affected in cultivars Kadiri 71‐1, Kadiri‐2 and ICGS‐11 due to inhibition of nodulation.
Biochemical and bioassay analysis of resistance of potato (Solanum tuberosum L.) cultivars to attack by the slug Deroceras reticulatum (Muller)
Authors: JOHNSTON K A , PEARCE R S
Published: February 2008

A method is described for using young field slugs Deroceras reticulatum (Muller) in a bioassay study of biochemical resistance of potato (Solanum tuberosum L.) cultivars to slugs. Tuber parts or an artificial diet were provided as food sources. Comparisons were made of feeding, survival and weight gain between the susceptible cultivar Maris Piper and the resistant cultivar Pentland Dell. Biochemical analyses were made of these two cultivars and the resistant cultivars Stormont Enterprise and Majestic. Comparisons of tuber sections and peelings as food sources indicated factors affecting growth were located in the surface layers of the tubers. Phenolics and glycoalkaloids were concentrated in the surface layers but the amounts were similar in the susceptible and resistant cultivars and the bioassays indicated that neither acting alone could explain resistance. The amounts and distribution of free amino acids also did not correlate with resistance although when supplied in the artificial diet they partly inhibited feeding. Proteinaceous inhibitors of slug gut proteolytic enzymes were present throughout the tubers but were not concentrated in the surface layers and the amounts were similar in the different cultivars thus they too did not explain the difference in susceptibility between the cultivars. Bioassays using acetone extracts (low molecular weight substances) and acetone powders (high molecular weight substances) either alone or in combination indicated that the resistant cultivar Pentland Dell contained a high molecular weight substance which together with a low molecular weight substance from either the same cultivar or the susceptible Maris Piper could confer resistance. Bioassays using protein extracts supplied in the presence or absence of chlorogenic acid indicated that this mechanism could comprise enzymic oxidation of phenolics. Assays of phenolase confirmed this since activity was highest in the outer layers of the tubers and was highest in the three resistant cultivars. Thus the chief resistance factor identified was high phenolase activity acting rapidly on phenolics when the slug first bites the tuber surface. The quantity of phenolics per se did not control the resistance. Thus while phenolics must be available, resistance is compatible with low blackening on cutting the tuber.
In vivo use of extracts from Ocimum gratissimum and Cymbopogon citratus against Phytophthora palmivora causing blackpod disease of cocoa
Authors: AWUAH R T
Published: February 2008

Crude steam distillate from Ocimum gratissimum sprayed onto infection courts on detached cocoa pods moments after inoculation with Phytophthora palmivora completely inhibited the pathogen and blackpod lesion development on 75% of the infection courts. Disease suppression obtained with the extract was comparable to that obtained with a 2% Kocide 101 suspension. In the field, the O. gratissimum extract also suppressed lesion development although to a significantly lower (P = 0.05) extent in comparison with Kocide 101. Blackpod lesion expansion rates of 3.80, 3.56, 2.71 and 0.78 cm/day, respectively, were associated with pods treated in the field with C. citratus extract, tap water, O. gratissimum extract and 2% Kocide 101. The extract from Cymbopogon citratus was also ineffective on detached pods. Sporangia of P. palmivora from sporu‐lating blackpod lesions on both detached and non‐detached pods lost their infectivity within 1 h of treatment with the O. gratissimum extract. This effect was superior to that obtained with Kocide 101. Fungitoxicity of the extract on pods, however, was lost within 3 h of application. Thus, despite its in vivo effectiveness as an eradicant, the O. gratissimum extract, in its present form, has limited utility as a protectant fungicide.
Incidence of potato virus Y infection in seed and ware tubers of the potato cv. Record
Authors: BARKER HUGH
Published: February 2008

The incidence of potato virus Y (PVY) infection was assessed in samples of potato tubers, cv. Record, taken from Scottish seed stocks and English ware crops grown from some of these seed stocks. PVY was readily detected by ELISA of tuber sprouts. PVY‐infected tubers were found in 10 seed stocks of 84 tested. The mean level of virus infection was 0.23%, 0.76% and 0.56% in Super Elite, Elite and AA stocks respectively. In 46 commercial ware crops grown from some of these seed stocks, a substantial proportion of the harvested tubers in all but one of the crops were infected with PVY, the mean percentage of infected tubers was 58.5%. Ware crops grown from seven seed stocks in which PVY had been detected (mean 6.2% infection in seed) contained a mean of 70% infected tubers, compared with 56% infection in crops grown from 39 stocks in which PVY was not detected in the seed tubers. The predominant PVY strain detected in the ware crops was the veinal necrosis strain (PVYvn).
A field evaluation of different criteria for determiningthe need to treat winter wheat against the grain aphid Sitobion avenae and the rose‐grain aphid Metopolophium dirhodum
Authors: OAKLEY J N , WALTERS K F A
Published: February 2008

The economics of control of grain aphid (Sitobion avenae) and rose‐grain aphid (Metopolophium dirhodum) were investigated in a series of experiments carried out across England in 1988 and 1989. Sprays of pirimicarb or dimethoate were applied at three growth stages and yield effects measured. Aphid infestations were determined by a range of different methods, to evaluate the value of each for decision making.

Aphids overwintered in crops in mild conditions in both seasons, resulting in early population build‐up and decline in many cases. Aphicide sprays applied during the booting stage increased average yields by 0.26 t/ha. Profitability of the treatment strategies considered was not greatly enhanced by selective spray application related to aphid assessment at this stage. Delaying decision making to the flowering or grain‐filling stages resulted in reduced profitability. A poor correlation between aphid numbers and crop yield response to sprays was found. This was shown to be due to differences in subsequent aphid population development and in aphicide efficacy. Grain quality was affected only by high aphid infestations which caused large yield reductions.
Predicting leatherjacket population frequencies in Northern Ireland
Authors: BLACKSHAW R P , PERRY J N
Published: February 2008

Annual surveys of leatherjacket (Tipula spp. larvae) were made in Northern Ireland to provide warning of the likelihood of damage to spring sown cereals after grass. A climate‐based multiple regression model was developed to estimate mean annual populations. Ades distributions were fitted to the annual data of leatherjacket counts to provide common estimates of parameters r and r. These values were then held constant to provide yearly estimates of A, the third parameter. The relationship between A and the sample mean was established so that a frequency distribution could be generated for any estimated mean population density. The ability of these models to predict leatherjacket frequency distributions was validated by using weather data for 1985–1988 to predict the number of fields with populations in excess of thresholds of 0.5,0.75 and 1 times 105ha‐1. It is concluded that the predictions were of sufficient accuracy to substitute for the annual leatherjacket survey.
Evaluation of fungicides applied to soil to control naturally‐occurring take‐all using a balanced‐incomplete‐block design and very small plots
Authors: BATEMAN G L , HORNBY D , PAYNE R W , NICHOLLS P H
Published: February 2008

Six sterol biosynthesis‐inhibiting fungicides representing several combinations of properties were applied to soil to control naturally‐occurring take‐all (caused by Gaeumannomyces graminis var. tritici) in winter wheat in field experiments in two successive years. The average take‐all severity category was never more than moderate in the different clay‐loam and sandy loam sites used in each year. At each site in each year there were six treatments and an untreated control in an arrangement based on a balanced‐incomplete‐block design for six treatments in 10 blocks each with three treatments. Each block had three treated plots and a control plot and was paired with the complementary block of three treatments (plus control) to form a complete replicate, of which there were 30 per site.

Take‐all assessments in June or July showed that after incorporation into the seed bed (at 2 kg ha“1and sometimes at 1 kg ha”1) in autumn, two non‐volatile, strongly lipophilic compounds, nuarimol and triadimenol, with good intrinsic toxicity to the take‐all fungus and slow rates of degradation, partially controlled take‐all. However, another compound, flutriafol, with similar properties to nuarimol and triadimenol, controlled take‐all less. Two slightly volatile, strongly lipophilic compounds, flusilazole and penconazole, with good intrinsic activity, were less effective (at 2 kg ha‐1). A volatile, less lipophilic compound, PP 969, with less intrinsic activity, also partially controlled take‐all, but only after application as a drench in the spring (2 kg ha‐1). The most effective treatments were generally more effective the greater the level of disease (as indicated by assessments of disease in control plots), especially in spring assessments of disease.

Although flutriafol did not perform as expected, it still seems reasonable to conclude that the requirements for a soil‐applied fungicide to control take‐all are likely to be: (i) good intrinsic fungitoxicity, (ii) some mobility in soil water (i.e. not strongly lipophilic), and (iii) season‐long persistence.
Properties of cocksfoot streak and cocksfoot cryptic, two viruses infecting cocksfoot (Dactylis glomerata) in Scotland
Authors: TORRANCE LESLEY , JONES A T , DUNCAN G H
Published: February 2008

A Scottish isolate of cocksfoot streak virus (CSV‐S) was found to have flexuous filamentous particles which, in sap of infected cocksfoot plants, had a modal length of 712 nm. It was transmitted from infected to healthy cocksfoot plants in a non‐persistent manner by Myzus persicae and by mechanical inoculation of infective sap extracts containing an anti‐oxidant. Apart from cocksfoot, mechanical inoculation of infective sap succeeded in infecting only four of 22 plant species tested. The infectivity of sap extracts containing 0.2% thioglycerol was lost after heating for 10 min at 55oC but not 50oC, storage at room temperature for 48 but not 24 hours, and after diluting 10‐2to 10‐3. Highly purified preparations of CSV‐S particles sedimented as a single component with a sedimentation coefficient of 139S and had a buoyant density in rubidium bromide of 1.31 g/cm3. Virus particles were composed of one protein and one ssRNA species with estimated Mr of 31 000 and 3.2 times 106respectively. In ELISA, an antiserum prepared to CSV‐S detected the virus in all aerial parts of infected cocksfoot plants and, when present in the ratio of 1 infected leaf: 1000 healthy leaves. Both CSV‐S‐infected and ‐uninfected cocksfoot also contained a previously undescribed virus with isometric particles c. 30 nm in diameter. This virus, named cocksfoot cryptic virus (CCV), was seed‐borne in two cvs of cocksfoot tested and its particles contained two dsRNA species of estimated Mr of 1.14 times 106and 1.27 times 106. Despite the fact that particles of CSV‐S were largely free from CCV particles following exclusion chromatography on agarose beads prior to immunisation, immunoelectron microscopy (IEM) showed that the antiserum prepared to CSV‐S also contained some antibodies to CCV. Evidence from IEM suggested a possible distant serological relationship of CCV to ryegrass and beet (BCV 1 or BCV 2, or both) cryptoviruses, all members of sub‐group A of crypto viruses.
The effects of osmotic pre‐sowing treatment on laboratory germination in a range of wild flower species
Authors: TALLOWIN J R B , ROOK A J , BROOKMAN S K E
Published: February 2008

Sown seed of many wild flower species have slow or delayed germination which can allow unsown and undesirable species to colonise a prepared site. Ideally all seed sown should germinate immediately. Priming seed in an inert osmoticum can improve synchronisation and speed of germination. The objective of this study was to assess the efficacy of priming on a selection of 60 wild flower species from a total of 21 different families. The majority of the species selected were common constituents of commercial seed mixtures. Seeds were primed in the light at 15CC for 14 days in a polyethylene glycol ‘6000’ solution giving an osmotic potential of either ‐10 or ‐15 bars. Priming had a highly significant effect on speed of germination reducing the median germination time by 2.8 ± 0.27 days in the ‐10 bar treatment and 1.6 ± 0.27 days in the ‐15 bar treatment. At the species level, 28 species had significantly reduced median germination times following priming. Priming significantly enhanced the final germination percentage in 15 species and significantly reduced it in eight species, with the adverse effect being more pronounced at ‐15 bars than at ‐10 bars. Non‐hierarchical cluster analysis showed no clear patterns in response to priming either in relation to the comparative ecology or the plant family of the species tested, with the possible exception of the Leguminosae species. Only one out of six members of this family showed any enhancement in germination rate or percentage.

The study demonstrates that a priming treatment could improve speed of germination, in a wide range of commonly sown semi‐natural grassland species.
Analysis of potential sources of variation in tissue culture derived celery plants
Authors: DONOVAN ANNE , COLLIN HAMISH A , ISAAC SUSAN , MORTIMER A MARTIN
Published: February 2008

Somaclonal variation derived from tissue culture is a potential source of variation that can be used in crop improvement programmes. The characteristics of this variation are first shown in the regenerant generation and their heritability is then confirmed by examination of the progeny. There would be savings of time, space and labour if this variation could be detected in vitro using easily assessed visual cues. The aim of this study was to relate variation in the source of explant and the morphology of the newly initiated callus to the characteristics of the regenerant plant, of which the most important was resistance to leaf spot disease caused by Septoria apiicola. Associations were investigated by isolating four stem explants from each of 564 surface sterile seedlings, var. Celebrity, on a callus initiation medium (MS medium, 30 g litre‘1sucrose, 0.5 mg litre’12,4‐D, 0.6 mg litre‘1kinetin) and assessing the morphology and colour of the callus. After this initial culture (8 wk), each callus was transferred to a regeneration medium (MS medium, 30 g litre“1sucrose). Plantlets were regenerated from many of the callus cultures and these were transferred to the glasshouse. When all of the surviving regenerant plants (276) were mature, leaf shape, amount and composition of the essential oils and resistance to late blight were assessed. Statistical analysis revealed that the character of the newly initiated callus (width, height, colour, organogenesis) showed poor correlation with all aspects of the regenerated plant measured. However, it was shown that increased variation resulted from different seedlings more than from plants derived from within seedlings or within callus.
The detection of salivary enzymes of phytophagous Hemiptera: a compilation of methods
Authors: MADHUSUDHAN V V , TAYLOR G S , MILES P W
Published: February 2008

The role of Hemipteran saliva and salivary enzymes is central to an understanding of the etiology of damage that these insects cause to plants. The dilute nature of the salivary secretions and the minute quantities in which they are often obtainable have made analysis and detection of salivary components very difficult. Such investigations in this laboratory have led us to formalise the techniques involved and we believe that the compilation of these methods presented herein may be useful to other research workers in this area. Methods are described for acid and alkaline phosphatase, esterase, /S‐glucosidase, carbohydrases, invertase, amylase, proteinase, pectinase, cellulase, catalase, peroxidase, catechol oxidase, superoxide dismutase and ascorbic oxidase.
Influence of fluctuating temperatures and interrupted periods of plant surface wetness on infection of bean leaves by ascospores of Sclerotinia sclerotiorum
Authors: PHILLIPS A J L
Published: February 2008

In artificial inoculations of bean leaves (Phaseolus vulgaris), the minimum period of plant surface wetness (PSW) required for the start of infection was temperature dependent. Infection was most rapid at 20–25oC and no infection occurred at 5oC or 27oC. In experiments conducted in a glasshouse or controlled environment chamber, the influence of fluctuating temperatures was taken into account by calculating degree hours (oh) of PSW. A continuous period of PSW was not necessary for successful infection. Successive short periods of PSW were not strictly additive. A dry period following a wet period delayed the start of infection for longer than the duration of the dry period. The length of the delay depended on the preceding oh PSW and on the duration of the dry period. From this information, a model was constructed to predict when first infections could be expected. This model was tested in small plot field experiments in two seasons. The date on which infection was first noticed coincided closely with the date on which oh PSW first exceeded 1200. The use of this model in disease control is discussed.
Characteristics of resistance in rice to rice hoja blanca virus (RHBV) and its vector, Tagosodes orizicolus (Muir)
Authors: ZEIGLER R S , PANTOJA A , DUQUE M C , WEBER G
Published: February 2008

This paper characterises resistance to rice hoja blanca virus (RHBV) which is transmitted by the planthopper Tagosodes orizicolus (Muir). Resistance is expressed as decreased proportion of plants infected compared to susceptible lines, although severity of symptom expression is similar in both types. This resistance is not due to differences in vector feeding behaviour. Vectors reared eight generations on resistant plants showed no increased ability to transmit to resistant lines or decreased ability to transmit to susceptible ones. Longevity of vectors was similar when reared either on virus‐resistant or susceptible plants. Incubation period of the virus in resistant plants are significantly longer than in susceptible plants. Resistance increased with plant age in resistant and susceptible cultivars. Increased virus dosage, as determined by increased number of viru‐liferous vectors per inoculated plant, caused an increase in transmission to both resistant and susceptible cultivars. However, the ranking of resistant and susceptible remained the same across the experimental range of dosage and plant age. It is concluded that the resistance studied is to virus infection and there is little risk of “breakdown” occurring as a result of genetic or behavioural changes in the vector population. This will permit the use of economic thresholds to planthopper feeding damage with little risk of RHBV epidemic outbreak.
Effects of beet cryptic virus infection on sugar beet in field trials
Authors: XIE W S , ANTONIW J F , WHITE R F , JOLLIFFE T H
Published: February 2008

The effects of beet cryptic virus (BCV) infection on sugar beet crops were investigated in field trials in 1990. Two sugar beet breeding stock lines were screened for infection by BCV. Seed lots containing different proportions of seed infected with BCV1 & 2 were obtained by crossing the stock lines and used in field trials at five different sites. Five characteristics of the infected plants were assessed. BCV infection appeared to have no significant effects on the sugar beet crop at four locations which suffered from drought stress but significant effects were found at one site where the crop was grown on grade 1 land with good moisture retention properties. Root yield and sugar yield were reduced by up to 17% and 20%, respectively, by BCV infection.
The effects of control on the biomass, carbohydrate content and bud reserves of bracken (Pteridium aquilinum (L.) Kuhn), and an evaluation of a bracken growth model
Authors: PAKEMAN R J , MARRS R H
Published: February 2008

This paper examines the initial effects of bracken control on frond numbers and biomass, and the biomass, carbohydrate reserves and bud densities of bracken stands cut once per year, twice per year, subject to a single application of asulam or left untreated. The seasonal dynamics of these parameters are displayed; carbohydrate and biomass are both removed from the rhizome system to produce frond tissue, and are replenished at the end of the growing season. Asulam application reduced densities of both active and dormant buds, and both frond biomass and density. It did not significantly reduce rhizome biomass or carbohydrate reserves in the two years after treatment. Cutting, either once or twice per year reduced both rhizome biomass and rhizome carbohydrate reserves, as well as bud densities, though the latter were reduced in proportion to biomass. Cutting twice a year reduced the production of fronds, both in numbers and biomass. The collected data were used to evaluate a model of bracken growth, and subsequently to improve estimates of some of the model parameters. The model simulations of control treatments were compared to field data. The effects of cutting once per year and spraying with asulam were predicted accurately, but the bracken stand was more resilient to cutting twice per year than would be expected from model predictions. The combination of cutting and spraying is discussed as a potential tool in land management and the deficiencies of the model are discussed in relation to the need for future research into the biology of bracken.