bluuebunny/crossref_metadata_2025_split huggingface dataset:
Residual effect of chlorhexidine gluconate in 4‐day plaque regrowth crossover trials, and its implications for study design
Authors: Newcombe R.G. , Addy M. , McKeown S. 
Published: July 2006

SummaryThe efficacy of oral hygiene agents in preventing the accumulation of plaque from a zero baseline is conveniently evaluated in the 4‐day plaque regrowth model. In many studies a panel of volunteers has been used to compare several agents according to a highly efficient Latin square based crossover design. Often chlorhexidine gluconate is included as a positive control; there is concern that the effect of this potent agent might persist for longer than the 3‐day washout period often employed. To test this hypothesis of residual effect, we put together the evidence relating to possible carryover from 12 studies. The residual effect of chlorhexidine differs from that of an inert rinse such as saline or water. Consequently, a longer washout period, such as 10 days, is preferable. Studies omitting chlorhexidine are worth considering. Designs should be balanced for residual effects, at least from the preceding treatment period; several useful designs with this property are presented.
Growth and phenotype of potato plants expressing an antisense gene of P‐protein of glycine decarboxylase under control of a promoter with preference for the mesophyll
Authors: WINZER T , HEINEKE D , BAUWE H 
Published: July 2006

SummaryA cDNA encoding P‐protein of glycine decarboxylase was expressed in antisense orientation in leaves of potato (Solanum tuberosum cv. Solara) under control of the promoter of a P‐protein gene of glycine decarboxylase from Flaveria pringlei. This promoter targets gene expression preferentially to the leaf mesophyll cells. In two of the transgenic lines, mitochondria oxidise glycine only with extremely low rates. Phenotypically, these transgenic lines were only marginally different from wild type plants under ambient carbon dioxide concentrations and indistinguishable from wild type plants when grown under 800 ppm carbon dioxide. When grown in ambient carbon dioxide, transgenic plants accumulated high amounts of glycine during the light period followed by nearly complete degradation in the following night.
Carbon allocation and sugar status in individual cells of barley leaves affects expression of Sucrose: Fructan 6‐Fructosyltransferase gene
Authors: KOROLEVA O A , TOMOS A D , FARRAR J F , GALLAGHER J , POLLOCK C J 
Published: July 2006

SummaryHeterogeneity of function in plant tissues requires precise regulation of metabolic systems controlling resource allocation at the level of single cells. Differential distribution of metabolites between epidermis, mesophyll and parenchymatous bundle sheath (PBS) cells has already been demonstrated in barley (Hordeum vulgare L.) source leaves and partitioning of sugars in barley leaves has been proven to be highly cell‐type specific. Carbohydrate metabolism of barley leaves induced to accumulate sucrose and fructans was investigated further at the individual cell level, using single cell sampling and analysis techniques. A novel approach using reverse transcription followed by polymerase chain reaction (RT‐PCR) was used to analyse expression of the enzyme Sucrose: Fructan 6‐Fructosyltransferase (6‐SFT) in individual cells of barley leaves. Accumulation of sucrose and the synthesis of fructans were induced by reducing export of sugars from leaves (root cooling), by increasing photosynthesis (high photon fluence rates), or by supplying sugars exogenously. In all cases there was a positive qualitative correlation between the presence of 6‐SFT transcripts and accumulation of fructan and sucrose in both mesophyll and PBS cells.
Potential for manipulating carbon metabolism in wheat
Authors: SPARKS C A , CASTLEDEN C K , WEST J , HABASH D Z , MADGWICK P J , PAUL M J , NOCTOR G , HARRISON J , WU R , WILKINSON J , QUICK W P , PARRY M A J , FOYER C H , MIFLIN B J 
Published: July 2006

SummaryThe transformation of wheat opens up opportunities for manipulation of key steps in plant metabolic pathways. Attempts to alter the expression of sucrose phosphate synthase (SPS) and glycine decarboxylase (GDC) in wheat leaves have been made.Using a maize SPS gene under the control of either a constitutive promoter (in p35SMSPS) or a green tissue specific promoter (in pRGMSPS), transformation of wheat (Triticum aestivum L. cv. Cadenza) led to the production of 22 independent transformed lines that contained the SPS transgene. Expression of the transgene, analysed by RT‐PCR, revealed that the transcript was present in nine of the 12 p35SMSPS plants and six of the 10 pRGMSPS plants. The maize SPS protein could not, however, be detected in any of these lines.The expression of GDC, and in particular that of the P subunit, has been shown to be altered in plant species with the intermediate C3/C4 photosynthetic phenotype. Attempts have been made to make similar changes in the expression of GDC in wheat leaves by transforming them with full length cDNA sequences for the P subunit of GDC in the sense and antisense orientation. More than 70 transformed lines were produced. Of these, 11 contained the gene in the sense, and 31 in the antisense, orientation, as determined by PCR. Results with Tt generation plants suggested that the activity of GDC had been reduced in some lines transformed with antisense constructs. However, there was no evidence for the expression of the sense constructs. GDC mRNA could not be detected by RT‐PCR in any of the 10 lines produced in the sense transformation experiments.Taken together, these results demonstrate the effectiveness of the technology to deliver large numbers of transgenic wheat plants. However, clearly this alone is not sufficient to guarantee the correct expression of the transgenes at sufficient levels to establish the presence of the gene product.
The role of cytosolic glutamine synthetase in wheat
Authors: HABASH D Z , MASSIAH A J , RONG H L , WALLSGROVE R M , LEIGH R A 
Published: July 2006

SummaryThe role of glutamine synthetase (GS; EC 6.3.1.2) was studied in wheat. GS isoforms were separated by HPLC and the two major leaf isoforms (cytosolic GS1 and chloroplastic GS2) were found to change in content and activity throughout plant development. GS2 dominated activity in green, rapidly photosynthesising leaves compared to GS1 which was a minor component. GS2 remained the main isoform in flag leaves at the early stages of grain filling but GS1 activity increased as the leaves aged. During senescence, there was a decrease in total GS activity which resulted largely from the loss of GS2 and thus GS 1 became a greater contributor to total GS activity. The changes in the activities of the GS isoforms were mirrored by the changes in GS proteins measured by western blotting. The changes in GS during plant development reflect major transitions in metabolism from a photosynthetic leaf (high GS2 activity) towards a senescencing leaf (relatively high GS1 activity). It is likely that, during leaf maturation and subsequently senescence, GS1 is central for the efficient reassimilation of ammonium released from catabolic reactions when photosynthesis has declined and remobilisation of nitrogen is occurring. Preliminary analysis of transgenic wheat lines with increased GS1 activity in leaves showed that they develop an enhanced capacity to accumulate nitrogen in the plant, mainly in the grain, and this is accompanied by increases in root and grain dry matter. The possibility that the manipulation of GS may provide a means of enhancing nitrogen use in wheat is discussed.
Variation in the harvest index of tropical maize: evaluation of recent evidence from Mexico and Malawi
Authors: HAY RKM , GILBERT RA 
Published: July 2006

SummaryIn temperate zones, the potential grain yield of wheat has increased during the twentieth century owing to progressive increases in the harvest index of new varieties, which are principally associated with reduction in plant stature. Crop biomass has not increased substantially. In contrast, the potential grain yield of maize in the USA has increased owing to progressive increases in biomass, principally associated with selection for grain yield at higher population density. Harvest index was already around 0.5 for recommended varieties in 1930, and has not increased significantly since. However, for both crops, the harvest index of a given variety has proved to be a highly‐heritable character, except under severe stress.Less is known about the physiology of tropical maize. This paper reviews evidence from Mexico and Malawi that tropical maize can respond to selection for reduced stature following the same pattern as temperate wheat, but, under other circumstances, the magnitude of harvest index is not highly heritable, varying inconsistently with season, management and environment. It is proposed that these differences arise out of the unique vulnerability of the grain‐setting process around flowering. The plasticity of harvest index under long, favourable conditions, however, remains to be explained, although it is probably also related to the events around grain setting. Nevertheless, to the subsistence farmer, higher harvest index may not be a high priority in crop improvement, because of the need for large quantities of high‐quality stover.
The rate of transport through a phosphate translocator affects delayed luminescence induction: an experiment and a theoretical model
Authors: KHUZNETSOVA S , BOGRACHEVA T , HEDLEY C , TULESHOVA A , KUKUSHKIN A 
Published: July 2006

SummaryDelayed luminescence (DL) induction curves were studied in leaves from a mutant pea line containing mutations at both the r and rb loci, compared with leaves from wild type plants. Genes at the r and rb loci encode starch branching enzyme and ADP ‐ glucose pyrophosphorylase, respectively. The presence of mutations at both loci, previously known to reduce the starch content in the dry mature seed by 75%, have been shown to lower the starch level in leaves by at least 20%. During induction, the half‐time for the DL intensity decrease from maximum to steady state in the mutant was 1.5 ± 0.2 times longer than for the wild type. It is proposed that the prolongation of the induction period in leaves from the mutant plants is caused by a lack of inorganic phosphate (Pi) restricting the rate of ATP synthesis at the beginning of induction. The reduced Pi would be compensated by triose flow from the chloroplast, via the triose phosphate translocator, being exchanged for Pi from the cytosol. Analysis of our theoretical photosynthesis model confirmed that a decrease in the rate of Pi released from the Calvin cycle could lead to a prolongation of the induction period.
Using plant analysis to predict yield losses caused by sulphur deficiency
Authors: BLAKE‐KALFF MECHTELD M A , ZHAO FANG‐JIE , HAWKESFORD MALCOLM J , McGRATH STEVE P 
Published: July 2006

SummaryYield losses in agricultural crops as a result of sulphur deficiency are increasing in the UK, because of the decrease in sulphur dioxide emissions and changes in fertiliser practices. Therefore, there is a need for a reliable and practical diagnostic indicator to predict early in the growing season whether it is necessary to apply S fertiliser, but also to avoid the application of fertiliser when not necessary. A successful diagnostic indicator should be reliable and stable throughout plant development, but also easily measured with great accuracy and as little effort as possible. In this paper the difficulties and problems with currently used diagnostic tests for S deficiency, such as total S, sulphate or the N:S ratio, will be discussed. A more reliable and practical indicator of S deficiency is the malate: sulphate peak area ratio which is at present being developed for use by commercial laboratories and their customers.
The impact of the aphids Tuberolachnus salignus and Pterocomma salicis on willow trees
Authors: COLLINS C MATILDA , ROSADO RUI G , LEATHER SIMON R 
Published: July 2006

SummaryThe effect of two species of stem‐feeding aphid on the yield, phenology and water‐use of soil‐grown and hydroponic‐cultured willow were investigated. The effects of Pterocomma salicis were less marked than those of Tuberolachnus salignus. The latter reduced not only the above and below‐ground growth of trees made during and subsequent to infestation, but also altered the mass of previously developed woody tissue. The negative effects of T. salignus on the shoots and roots of established and establishing trees were drastic and were both quantitative and qualitative. They were also observed to reduce the survival of infested trees. P. salicis had negative effects on the growth of roots and shoots during infestation, but the influence of this species did not persist nor did it influence previous growth.
The roles of ascospores and conidia of Pyrenopeziza brassicae in light leaf spot epidemics on winter oilseed rape (Brassica napus) in the UK
Authors: GILLES T , FITT B D L , McCARTNEY H A , PAPASTAMATI K , STEED J M 
Published: July 2006

SummaryAscospores of Pyrenopeziza brassicae were produced in apothecia (cup‐shaped ascomata) on oilseed rape debris. The conidia, which were morphologically identical to the ascospores, were produced in acervular conidiomata was greater than for lesions caused by ascospores. In June 2000, on the ground under a crop with light on the surface of living oilseed rape tissues. Ascospores were more infective than conidia on oilseed rape leaves. The proportion of lesions caused by conidia located on leaf veins leaf spot, numbers of petioles with apothecia decreased with increasing distance into the crop from the edge of pathways. Air‐borne ascospores of P. brassicae were first collected above debris of oilseed rape affected with light leaf spot on 5 October 1998 and 18 September 1999,12 or 23 days, respectively, after the debris had been exposed outdoors. P. brassicae conidia were first observed on leaves of winter oilseed rape on 6 January 1999 and 15 February 2000, respectively, after plots had been inoculated with debris in November 1998 and October 1999. In 1991/92, numbers of ascospores above a naturally infected crop were small from January to April and increased in June and July. P. brassicae conidia were first observed in February and the percentage plants with leaves, stems or pods with light leaf spot increased greatly in May and June. In 1992/93, in a crop inoculated with debris, numbers of airborne ascospores were small from October to January and increased from April to June. P. brassicae conidia were first observed on leaves in late November and light leaf spot was seen on stems and pods in March and June 1993, respectively.
A new disease in Tabernaemontana associated with Tobacco mild green mosaic virus
Authors: COHEN J , ROSNER A , KAGAN S , LAMPEL M , MASLENIN L , ZEIDAN M , GERA A 
Published: July 2006

SummaryConspicuous viral symptoms were seen on Tabernaemontana divaricata, a member of the family Apocynaceae, grown in a commercial nursery, in Israel. The symptoms varied widely and included chlorotic ringspots and banding, oak‐leaf patterns and mosaic. At the end of the winter, large yellow spots, which later became necrotic, appeared on fully expanded leaves. The necrotic zones later fell out, leaving “shot holes”. Preliminary analysis suggested that the disease was associated with a tobamovirus. Particles typical of a tobamovirus were observed by electron microscopy only in samples taken from symptomatic leaves. Apartial segment of the 5′‐terminus of the viral RNA, which comprised of 533 bp was cloned and sequenced. Comparison of the predicted amino acid sequence with those of other tobamoviruses revealed 94% identity with Tobacco mild green mosaic virus (TMGMV) genome. Primers specific to the coat protein (CP) gene of TMGMV used in a reverse transcription‐polymerase chain reaction assay (RT‐PCR) gave an expected amplification product of 455 bp. The amino acid composition of the cloned CP gene, which shows a complete identity to that of TMGMV, confirmed the identity of TMGMV infecting Tabernaemontana. Polyclonal antibodies prepared against the virus and used in double antibody sandwich enzyme‐linked immunosorbent assay (DAS‐ELISA) enabled specific detection of the virus in crude sap extracted from T. divaricata and mechanically inoculated indicator plants. This is the first report of TMGMV infection in Tabernaemontana and the first incidence of the virus in Israel.
Virus infection stimulates phyto‐oestrogen production in pasture legume plants growing in grazed swards
Authors: JONES R A C , FERRIS D G 
Published: July 2006

SummaryFour field experiments were sown with AMV‐infected or healthy seed of burr medic (Medicago polymorpha) and grazed by sheep; two were sown with cv. Circle Valley and two with cv. Santiago. Seed‐infected plants acted as primary sources for virus spread by naturally occurring aphids. Insecticides and admixture with annual ryegrass (Lolium rigidum), a non‐host of AMV, suppressed virus spread to different extents in the plots sown with infected seed. Effects of the different amounts of virus spread obtained on overall concentration of the oestrogenic compound coumestrol (dihydroxycoumestan) in dry stems and pods, and on seed production were measured in the medic. With cv. Santiago, stem and pod coumestrol concentration values for plots sown with healthy seed were significantly smaller than those for all plots sown with infected seed regardless of whether they were sprayed. With cv. Circle Valley, the coumestrol values for stems from plots sown with healthy seed were significantly smaller than those for unsprayed plots sown with infected seed but not than those for sprayed plots or ones with grass admixtures, and there were no significant differences with pods. There was always a significant positive relationship between concentration of coumestrol in medic stems and percentage AMV infection of swards; this was also so with pods in two experiments. A linear model best fitted this relationship with cv. Circle Valley but a logarithmic model did so with cv Santiago. In glasshouse grown plants, the coumestrol content of dried medic shoots was increased 11 (cv. Circle Valley) and five (cv. Santiago) times by AMV infection. AMV increased mean coumestrol concentrations up to 256 ppm (field) and 237 ppm (glasshouse) in stems and 223 ppm in pods (field). Sowing healthy seed in new pasture swards was an effective strategy for minimising coumestrol accumulation in burr medic swards. Two, but not single, applications of a newer generation pyrethroid insecticide to swards in which AMV was spreading significantly diminished coumestrol accumulation but applying organophosphorus insecticide twice and carbamate insecticide repeatedly did not. Medic seed yields and individual seed weights were sometimes significantly increased by the treatments, suppression of AMV spread by regular carbamate sprays being sufficient to increase seed yield by 55%.
Molecular characterisation of Onion yellow dwarf virus (OYDV) infecting garlic (Allium sativum L.) in Israel: Thermotherapy inhibits virus elimination by meristem tip culture
Authors: SHIBOLETH Y M , GAL‐ON A , KOCH M , RABINOWITCH H D , SALOMON R 
Published: July 2006

SummaryGarlic (cv. Shani) was tested using single step RT‐PCR and digoxygenin (DIG) labelled dot‐blot for a number of viruses. Following sequence analysis it was shown that at least three different polymorphs of the potyvirus Onion yellow dwarf virus (OYDV) infect the same plant simultaneously, together with the potyvirus Leek yellow stripe virus (LYSV), the carlavirus Garlic common latent virus (GCLV) and a multitude of allexiviruses (Shallot virus X (ShVX) related viruses]. Several garlic plants free of all the viruses tested were obtained through meristem‐tip culture. Plants infected with single viruses or with different combinations of viruses were similarly obtained. Meristem‐tip culture was confirmed as a satisfactory method of virus eradication, while thermotherapy treatment given to mother plantlets before meristem excision was found to specifically antagonise OYDV eradication. This work uses molecular methods for the first time to examine the effectiveness of meristem‐tip culture for the eradication of multiple viruses from garlic.
Modelling crop physiology for integrated decision making
Authors: DAY W 
Published: July 2006

SummaryCrop modelling has had a mixed press over the years, driven as much by the community's expectations as by the targets identified by modellers. This short review gives a personal perspective on the scope and value of models of crop processes and performance, in the context of the increasing demand to make predictions about the best course of action for farmers. The goal for these predictions can range from the best rate or timing for a pesticide spray to the likely pressure on the farming community if predicted levels of climate change are realised. The primary conclusion is that a clear statement of objectives is the most important precursor to the use of models of crop processes or systems.
Effects of hot water treatments and storage temperatures on the ripening and the use of electrical impedance as an index for assessing post‐harvest changes in mango fruits
Authors: NYANJAGE M O , WAINWRIGHT H , BISHOP C F H 
Published: July 2006

SummaryThe effects of hot water treatment and storage temperature (4°C, 13°C or 22°C) on the quality and impedance of outer and inner mesocarp of mango were assessed in two experiments during storage, impedance being a potential non‐destructive measure of tissue damage following heat treatment. Fruits were subjected to equivalent heat units at 36.5°C for 60 min plus 46.5°C for 43 min or 46.5°C for 90 min by hot water treatments (hwt) on the assumption of cumulative heat effects and a base temperature of 12–13°C. Fruit reflectance decreased whereas chroma and hue angle increased over storage time and also with increase in storage temperature. The yellow colour increased with a rise in storage temperature in hot water treated mangoes. Soluble solids content of mangoes held at 22°C was highest at 5 days of storage but decreased subsequently over storage time. Impedance of all fruits decreased with increase in frequency, storage temperature and time in store. The impedance of hwt mangoes was lower than that of non‐hwt fruits 8 h after immersion, but recovered almost to control levels on day 5 at 4°C or 13°C, but decreased gradually after 5 days at 13°C. Impedance of all mangoes stored at 22°C decreased continuously during storage. Impedance was higher in the inner mesocarp than outer pulp. Impedance of hwt fruits was poorly correlated with soluble solid content and chroma but well correlated with reflectance of fruit pulp at 22°C. Changes in impedance of mangoes are discussed in relation to physiological and biochemical changes that occur during heat treatment and storage.
Disease spread patterns of Banana streak virus in farmers, fields in Uganda
Authors: KUBIRIBA J , LEGG J P , TUSHEMEREIRWE W , ADIPALA E 
Published: July 2006

SummaryThree surveys were conducted to establish the disease spread patterns of Banana streak virus (BSV) in farmers, fields in Uganda. Transects were traced both across the fields and from infection foci within a field. BSV incidence in adjacent quadrats was also determined to quantify statistically the spatial relationships of infected plants in the fields. Severity assessment along transects across fields revealed clusters of plants with moderate to high severity and clusters of plants with no BSV or low severity. Symptom severity decreased away from foci of infection (b=−0.014; P=0.0081). Observed frequency of infected quadrat counts differed from corresponding expected frequency of infected quadrat counts (Poisson, s distribution, x2; P<0.01). BSV– infected plants, therefore, were aggregated in well‐established fields. Aggregation of infected plants in farmers, fields and the decrease of severity away from infection foci suggest the likely involvement of a slow moving vector in BSV transmission.