bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transmission of tomato leaf curl geminiviruses by Bemisia tabaci: effects of virus isolate and vector biotype
Authors: McGRATH P F. , HARRISON B D. 
Published: February 2008

SUMMARYCultures of Bemisia tabaci from Ivory Coast (IC), Pakistan (PK) and USA (US B‐type) were compared for the frequency with which they transmitted three tomato geminivirus isolates: Indian tomato leaf curl virus from Bangalore (ITmLCV), and tomato yellow leaf curl viruses from Nigeria (TYLCV‐Nig) and Senegal (TYLCV‐Sen). Frequency of transmission from tomato to tomato depended both on the whitefly culture and the virus isolate. US B‐type and IC whiteflies transmitted TYLCV‐Sen more frequently than ITmLCV whereas PK whiteflies transmitted ITmLCV more frequently than TYLCV‐Sen. US B‐type whiteflies transmitted both viruses four to nine times more frequently than IC whiteflies. TYLCV‐Nig was transmitted rarely by US B‐type and not at all by IC whiteflies.Previous work indicates that the geminivirus coat protein controls vector transmissibility. The differential adaptation of TYLCV‐Sen to transmission by US B‐type whiteflies and of ITmLCV to PK whiteflies was associated with a large difference in epitope profile of the coat proteins of the two viruses. Also, the readily transmissible TYLCV‐Sen differed appreciably in epitope profile from the poorly transmissible TYLCV‐Nig, which reached a consistently greater concentration in source tissues but lacked epitope 18. However, the lack of epitope 18 in ITmLCV did not prevent its transmission by US B‐type whiteflies. Differences in frequency and specificity of geminivirus transmission by whitefly cultures from different countries therefore were associated with differences among epitope profiles of the coat proteins of the viruses, but the structural features of the proteins that control transmission remain to be determined.
A two parameter model for prediction of crop loss by weed competition from early observations of relative leaf area of the weeds
Authors: KROPFF M J. , LOTZ L A P. , WEAVER S E. , BOS H J. , WALLINGA J. , MIGO T. 
Published: February 2008

SUMMARYThe recently introduced empirical model for early prediction of crop loss by weed competition based on the relative leaf area of the weeds shortly after crop emergence (Kropff & Spitters, 1991), assumes a maximum yield loss of 100% at high weed infestations. This is biologically not realistic. If weeds have a shorter life cycle than the crop, when they emerge much later than the crop or when they are unable to overtop the crop, maximum yield loss at high weed infestations is expected to be less than 100%. A two parameter model is introduced in this paper that accounts for a variable maximum crop yield loss by weed competition. The parameters are the “relative damage coefficient”q, and a parameter that describes the maximum yield loss caused by the weeds (m). The one and two parameter models were evaluated with data on the effects of weeds on rice, sugarbeet and tomato.Both models were able to describe the data on the effect of different weed densities and periods between crop and weed emergence fairly well. The introduction of the second parameter resulted in a significantly better description of observed data in five out of nine datasets. The value of the parameter q depends on the time of observation of the relative leaf area. The change in the value of q in time could be estimated from the difference in relative growth rate of the species. The accuracy of this estimation is strongly determined by the variability in the relative growth rate of the leaf area of single plants. Possibilities for scientific and practical application of the model are discussed.
The effect of modifying the glucosinolate content of leaves of oilseed rape (Brassica napus ssp. oleifera) on its interaction with specialist and generalist pests
Authors: GIAMOUSTARIS A. , MITHEN R. 
Published: February 2008

SUMMARYTwenty eight Brassica napus lines were developed which had contrasting leaf glucosinolate profiles to those found in commercial oilseed rape cultivars. The lines varied both in the total amount of aliphatic glucosinolates and in the ratio of different side chain structures. The lines were used in field experiments to assess the manner by which glucosinolates mediate the interactions between Brasssica and specialist pests (Psylliodes chrysocephala and Pieris rapae) and generalist pests (pigeons and slugs). Increases in the level of glucosinolates resulted in greater damage by adult flea beetles (P. chrysocephala) and a greater incidence of Pieris rapae larvae, but reduced the extent of grazing by pigeons and slugs. Decreasing the side chain length of aliphatic glucosinolates and reducing the extent of hydroxylation of butenyl glucosinolates increased the extent of adult flea beetle feeding. The implications of modifying the glucosinolate content of the leaves of oilseed rape and the role of these secondary metabolites in plant/herbivore interactions are discussed.
Movement of apterous Sitobion avenae (Homoptera: Aphididae) in response to leaf disturbances caused by wind and rain
Authors: MANN J A. , TATCHELL G M. , DUPUCH M J. , HARRINGTON R. , CLARK S J. , McCARTNEY H A. 
Published: February 2008

SUMMARYThe effect of wind and rain on initiation of dispersal and subsequent distances moved by apterous Sitobion avenae was quantified in five laboratory experiments. Wind duration and type (steady and gusting), rain duration and intensity, and a combination of wind and rain were investigated. With increased duration of wind there was an increase in the average distance aphids moved. There was less movement when aphids were exposed to gentle gusting, than to steady wind or strong gusting. With increased duration of rain there was an increase in the proportion of aphids lost from plants. Under heavy rain, the proportion of aphids off the release plant, the distance moved by them and the proportion of aphids lost, was greater than for drizzle or light rain. When wind and rain were compared, rain had the greater impact on aphid dispersal. It was concluded that leaf disturbances caused by strong gusts of wind or large rain droplets are of considerable importance in the initiation of aphid dispersal, but that wetness alone is not.
The movement and distribution of citrus tristeza virus and citrus exocortis viroid in citrus seedlings1
Authors: GAFNY R. , MOGILNER N. , NITZAN Y. , BEN‐SHALOM J. , BAR‐JOSEPH M. 
Published: February 2008

SUMMARYThe systemic movement of citrus tristeza virus (CTV) in sour orange (Citrus aurantium) seedlings and of citrus exocortis viroid (CEVd) in Etrog citron (C. medica) seedlings was studied. The movement of the two pathogens was analysed by detection in sections of roots and stems at different time intervals. Both pathogens were detected initially in the basal parts and the roots and subsequently spread to the shoot. CTV and CEVd moved in young citrus seedlings at similar rates. The findings are consistent with long distance phloem transport of the virus and the viroid. The practical implications of the pattern of systemic movement for diagnosis of infected trees are discussed.
Characterisation and serological relationships of strains of Kashmir bee virus
Authors: ALLEN M F. , BALL B V. 
Published: February 2008

SUMMARYIsolates of novel strains of Kashmir bee virus (KBV) were obtained from field‐collected dead adults of Apis mellifera from honey bee colonies in Canada and Spain. They differed from other strains of KBV in their tendency to aggregate in dilute buffer solution and in containing only three proteins when analysed by SDS‐polyacrylamide gel electrophoresis compared with five proteins resolved in the type strain of KBV from Apis cerana in India and six proteins in KBV strains from South Australia and New Zealand. Immunodiffusion tests and Western blotting studies indicated that the five virus isolates were serologically related and all were related to acute paralysis virus (APV). The world distribution of KBV strains and their apparent relationship with APV are discussed.
Biology of the hop cyst nematode Heterodera humuli
Authors: MENDE N VON , McNAMARA D G. 
Published: February 2008

SUMMARY Heterodera humuli inhibited plant growth in pot experiments when the nematode population exceeded 500 eggs g‐1 of soil; below this density there was evidence of stimulated growth. The development of H. humuli was tested on seven hop cultivars. No differences were found in the numbers of newly produced cysts on different cultivars but the sizes of the cysts differed significantly. The biggest cysts were found on a wild hop and the smallest on the cultivar ‘OR/55’. The nematode and the fungus, alone or in combination, did not affect the bine length of cvs Northdown or Target. The growth of nematode infested plants of a wilt susceptible hop cultivar was significantly reduced when the plant pathogenic fungus Verticillium albo‐atrum was also present. Verticillium did not significantly influence the reproduction of H. humuli under either laboratory or field conditions although hatching of juveniles in the field was delayed by two weeks and more juveniles were found in the soil during late summer around the roots of fungus infected plants in the field.
The effect of temperature on leaf appearance and canopy establishment in fibre hemp (Cannabis sativa L.)
Authors: WERF H M G VAN DER , BROUWER K. , WIJLHUIZEN M. , WITHAGEN J C M. 
Published: February 2008

SUMMARYThe effects of temperature on the development and growth of hemp (Cannabis sativa L.) have never been quantified. Therefore, to establish the effect of temperature on leaf appearance and canopy establishment of fibre hemp under controlled and field conditions, plants were grown in growth chambers at 11 regimes with average temperatures between 10°C and 28°C, and three cultivars were sown in the field in March, April and May in 1990, 1991 and 1992. In the field, thermal time (base 0°C) between sowing and emergence ranged from 68°Cd to 109.5°Cd (average 88.3°Cd). Rates of leaf appearance and stem elongation increased linearly with temperature between 10°C and 28°C. The base temperature for leaf appearance was 5.7°C from the growth chamber experiments and 1°C from the field experiments. In the field, the base temperature for the relationship between light interception by the canopy and thermal time was 2.5°C, and thermal time, calculated at the appropriate base temperature, accounted for about 98% of the variance in the number of leaves and for 98.6% of the variance in the proportion of light intercepted by the canopy. Days from emergence accounted for less of the variance in both parameters than thermal time. Interception of 90% of light was attained on average at 465°Cd (base 0°C) after emergence. It is concluded that thermal time is a simple and accurate tool to describe leaf appearance and light interception in fibre hemp.
Surface movement rates of the New Zealand flatwormArtioposthia triangulata: potential for spread by active migration
Authors: MATHER JANICE G. , CHRISTENSEN OLE M. 
Published: February 2008

SUMMARYMovement rates for the surface activity of the New Zealand flatwormArtioposthia triangulata(Dendy) (Tricladida: Terricola) were estimated under semi‐field conditions in the Faroe Islands. The distance travelled during 10 consecutive 1‐minute periods per individual was measured from mucus trails left behind as the flatworms moved over black plastic sheeting sprayed with fine droplets of water. Adult specimens were found to crawl at rates of up to 28 cm min‐1(almost 17m h‐1), whereas juveniles crawled at rates of between 3 and 4cm min‐1(approximately 2m h‐1). This study provides the first data concerning the potential for species spread by active migration.
Development of black dot disease (Colletotrichum coccodes (Wallr.) Hughes) and its effects on the growth and yield of potato plants
Authors: READ P. J. , HIDE G. A. 
Published: February 2008

SummarySeed tubers of cvs Désirée and Pentland Crown with different severities of black dot were planted in 1988 and 1989 at Rothamsted in fields in 4– or 7‐course rotations, respectively. Tubers treated with prochloraz (1988) or imazalil (1989) were planted in some plots, and in others Colletotrichum coccodes inoculum was added to the soil at planting. In further experiments at Mepal, Cambridgeshire in 1989 and 1990 and at Rothamsted in 1990 on sites where potatoes had not been grown for more than 15 years, large amounts of inoculum were added to the soil around disease‐free seed tubers of two (1989) or three (1990) cultivars at planting. In all experiments plants were sampled during the season and the effects of treatments on disease development, growth and yield were recorded.Disease on roots, stem bases and tubers was found early in the season and was more severe on Désirée than on Pentland Crown plants from fields in 4– or 7‐course rotations. Severity increased throughout the season and with increasing amounts of disease on the seed tubers, especially with Desiree. Disease was also found on plants from disease‐free tubers and was more severe in 1988 than 1989. At harvest, black dot on tubers was significantly more severe from severely affected than from disease‐free seed, and was most severe where inoculum, especially large amounts, had been added at planting. Fungicide treatment decreased disease early in the season but had no effect on tuber infection at harvest. In 1989 the weight loss of seed tubers during sprouting increased with increasing amounts of black dot, but the disease had little effect on plant size through the season. At harvest the yield of ware tubers (>50 mm) decreased with severe disease but total tuber yields were not significantly affected. However, at harvest in 1988 severely affected seed yielded significantly less than healthy seed.Plants grown from mini‐tubers were free from disease on sites where potatoes had not been grown for at least 15 years. Inoculum applied at planting caused severe disease on all cultivars in both years, whereas disease was slight on uninoculated plants. Inoculated plants senesced early at Mepal in 1990, but there were no significant differences in total tuber yield in any experiment. However, yields of ware tubers (>50 mm) were sometimes decreased and the total tuber number per plant increased.
Isolation and characterisation of a new Venezuelan strain of cassava common mosaic virus
Authors: MARYS EDGLORIS , IZAGUIRRE‐MAYORAL MARÍA LUISA 
Published: February 2008

SummaryA new strain of cassava common mosaic virus, designated CsCMV‐ve, was isolated from cassava (Manihot esculenta Crantz) plants growing in Venezuela. The 520 nm long semi‐flexuous virus particles sedimented in sucrose gradients as one component and contained a single coat protein molecule of c. 28 kDa, and a ssRNA of c. 2.1 times 106. A single dsRNA species of c. 4.2 times 106kDA was isolated from virus‐infected cassava leaves. In double antibody sandwich enzyme‐linked immunosorbent assay, CsCMV‐ve reacted strongly with antisera to CsCMV and potato virus X, but not with those to other typical members of the potexvirus group. Ultrastructural studies of CsCMV‐ve infected cells showed the presence of large bundles of inclusion bodies in the cytoplasm, a proliferation of the rough endoplasmic reticulum, and large crystals in the peroxisomes. CsCMV‐ve in crude buffered sap or in purified preparations was not mechanically transmitted to known hosts of the Chaya and Brazilian strains of CsCMV. Isolated virus RNA also failed to infect a range of test‐plant species. This is the first report of the presence of CsCMV in Venezuela.
Towards genetic based insect resistance in strawberry using the Cowpea trypsin inhibitor gene
Authors: GRAHAM J. , McNICOL R. J. , GREIG K. 
Published: February 2008

SummaryAn efficient shoot regeneration system has been developed involving organo‐genesis from stem tissue of the strawberry cultivars Melody, Rhapsody and Symphony. Regeneration also occurred in the presence of antibiotics. The system was shown to be suitable for transformation using the GUS:Intron marker gene construct. Histological analysis using the substrate 5‐bromo‐4‐chloro‐3‐indolyl B‐D‐glucuronide (X‐Gluc) and the polymerase chain reaction (PCR) using specific primers permitted the identification of transformants.Inoculations were then carried out using the Cowpea protease trypsin inhibitor (CpTi) gene construct. A simple visual assay technique was developed to identify those plants expressing CpTi, allowing them to be selected for further analysis. Trypsin acts on the substrate α‐N‐benzoyl‐DL‐arginine‐p‐nitroanilide (BAPNA) to produce p‐nitroaniline (p‐na). Trypsin inhibition CpTi was easily detected as a reduction in or elimination of yellow colour development which occurred as the hydrolysis of BAPNA to pna proceeded (Preiser, Schmitz, Maestracci & Crane, 1975). The polymerase chain reaction (PCR) was used to confirm the presence of the gene sequence.
Prolonged aerated hydration for improvement of seed quality in Brassica oleracea L.
Authors: THORNTON J. M. , POWELL A. A. 
Published: February 2008

SummarySeeds of cauliflower cv. Hipop and Brussels sprouts cv. Asmer Aries were aged at 20% moisture content for 24 h; all seeds retained a germination of over 70% after ageing although the mean germination time increased. Prolonged aerated hydration for up to 32 h at 20°C followed drying resulted in improved performance of both unaged and aged cauliflower seeds and aged Brussels sprouts. Thus, all seed showed reductions in the mean germination time to the extent that after 32 h hydration the aged cauliflower seeds performed as well as high quality unaged seed. The improvement of aged seeds was also revealed an increase in germination after the controlled deterioration test following up to 24 h (cauliflower) or 32 h (Brussels sprouts) aerated hydration. This increase was indicative of a decrease in the extent of deterioration present after aerated hydration. Deleterious effects of prolonged hydration were observed in Brussels sprouts after 32 h although these may be explained desiccation injury after treatment since radicle emergence had occurred during hydration. The improvements in seed performance may be explained the activation of metabolic repair occurring during the early part of the hydration period therereducing the extent of deterioration that has been sustained during ageing, with further improvements due to the advancement of the germination process.
Interactions between diurnal temperature fluctuations and salinity on expansion growth and water status of young tomato plants
Authors: McCALL D. , ATHERTON J. G. 
Published: February 2008

SummaryExpansion growth is limited if the difference between day and night temperature (DIF) is negative. Growth is also limited high salinity. Expansion growth of tomato seedlings was studied under day/night temperatures of 16/24°C and 24/16°C, and nutrient solution salinities of 3 and 15 mS cm‐1 to ascertain whether interactions exist between the two stress forms. Water status was also studied in order to assess possible mechanisms of growth retardation. A significant interaction between DIF and salinity was found for all recorded growth variables. Hypocotyl length, plant height, leaf area and fresh and dry weight were lower at negative DIF than at positive, the reduction being greater at low salinity than at high. Increased salinity also reduced growth, more so at positive DIF than at negative. Growth reduction at negative DIF was accompanied increased shoot water and osmotic potentials. Pressure potential was unaffected DIF. Growth reduction at high salinity was accompanied reduced water and osmotic potentials. Pre‐dawn pressure potential was increased at high salinity, whereas no effect of salinity on pressure potential at midday was found. The differences in effects on water status between the two stress forms may suggest differing mechanisms of growth retardation.
Detection of groundnut rosette umbravirus infections with radioactive and non‐radioactive probes to its satellite RNA
Authors: BLOK V. C. , ZIEGLER A. , SCOTT K. , DANGORA D. B. , ROBINSON D. J. , MURANT A. F. 
Published: February 2008

SummaryA cloned cDNA copy of the satellite RNA of groundnut rosette virus (GRV), labelled with either 32P or digoxigenin, was used as a probe to detect the satellite RNA in infected leaves. The test was successfully applied to N. benthamiana and to groundnuts, infected with isolates of GRV from East and West Africa and with isolates which cause different types of symptom in groundnuts, including one which is almost symptomless. Although the probe did not react with extracts from plants infected with GRV isolates from which the satellite RNA had been artificially eliminated, all naturally occurring GRV isolates contain the satellite RNA. The test therefore provides a reliable indicator of infection by GRV.
Control of Western flower thrips (Frankliniella occidentalis Pergande) pupae in compost
Authors: Helyer Neil L. , Brobyn Patricia J. , Richardson Paul N. , Edmondson Rodney N. 
Published: February 2008

SummaryWestern flower thrips (Frankliniella occidentalis) develops from an active larval stage through to a non‐feeding, almost immobile, pre‐pupal and pupal stage. This generally occurs in the compost or soil below the plant on which the larvae fed. Control of thrips at this stage in their development offers a chance of utilising pathogens or pesticides not suitable for use in an integrated control programme aimed at adult and larval stages. Trials were done with F. occidentalis pupae and pre‐pupae in a soil/peat based compost using 11 pesticides, three fungal pathogens and four species of insect parasitic nematodes. The pesticides malathion and chlorpyrifos‐methyl gave the most promising result with 97.5% and 96.5% control, respectively. The fungal pathogen Metarhizium anisopliae proved better when applied as a pre‐pupation rather than as a post‐pupation treatment (74.5% : 26.6% control). The insect parasitic nematode Steinernema carpocapsae gave 76.6% control when applied at 25 times 104 nematodes litre‐1 of compost. The results are discussed in relation to control of thrips in glasshouses.
A greenhouse assay to screen sunflower for resistance to Alternaria helianthi
Authors: Kong G A. , Kochman J K. , Brown J F. 
Published: February 2008

SummaryA greenhouse assay to screen sunflower for resistance to Alternaria helianthi is described. A comparison of conditions led to the following standard conditions being recommended. The first or second pair of leaves of seedling plants at the V8 growth stage are inoculated using inoculum grown on sunflower leaf extract agar for 5–10 days at an inoculum density of 1–2 spores cm2 of leaf tissue. A 48 h dew period should be applied to plants covered by a plastic tent. A dew period temperature of 26/26°C night/day and a post‐dew period temperature relative to that experienced under local growing conditions should be applied. Lesions are measured 7 days after inoculation, and mean lesion size per plant is calculated. Mean lesion size of lines being tested is expressed as a proportion of the mean lesion size of a susceptible standard included in each screening experiment.