bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationships of wheat quality with climate and nitrogen application in regions of England (1974–1993)
Authors: SMITH G P , GOODING M J
Published: February 2008

Region x year means for crude protein concentration (CP) and Hagberg falling number (HFN) from the Home Grown Cereals Authority (HGCA) surveys were modelled using mean daily temperature, rainfall and nitrogen application. A model accounting for 78.6% of the variation in CP incorporated positive coefficients for mean daily temperature (25 June to 15 July), nitrogen applied to the crop, and early summer rainfall (28 May to 8 July), and a negative coefficient for spring rainfall (5 March – 27 May). For CP there was no statistical evidence that fitting one regression for all regions was significantly worse than fitting individual lines for each of the 10 regions. A model describing 67.1% of the variation in HFN incorporated a negative coefficient for August rainfall and positive coefficients for mean June temperature, mean August temperature and nitrogen applied to the crop. There was statistical evidence that fitting separate lines for certain regions was justified.
Radiation interception and modelling as an alternative to destructive samples in crop growth measurements
Authors: WILLIAMS J H , RAO R C NAGESWARA , DOUGBEDJI F. , TALWAR H S
Published: February 2008

Growth analysis presently uses destructive samples to detect temporal variations in biomass. The destructive nature of the measurements, their cost, and statistical considerations limit the application of growth studies in many domains of crop science. In contrast radiation interception data are cheap and easy to obtain without destruction of experimental material. Biomass may be modelled as the product of cumulative radiation intercepted by the crop [ΣI] and a radiation use efficiency coefficient [e]. Therefore, in theory, an alternative to destructive samples is provided by measurement of I at intervals during growth and e. The success of this approach depends on the validity of the value of e and its constancy through time. With measurement of I at intervals the mean radiation use efficiency [Σ] can be estimated from the seasonal ΣI and the final harvest data. The Σ can then be used with the time series data for ΣI to estimate the biomass for that plot for any date. To test this approach model‐derived biomass data were compared with data from destructive samples at seven dates for six groundnut germplasm lines grown in water limiting and fully irrigated conditions. The model‐derived data was consistently less than destructively obtained data when the plants were small. This bias was an artifact of the interception measurement technique used not being accurate for small plants. Once plants were tall enough for fractional interception to be measured without substantial error, the nondestructive method effectively described the growth of the well‐watered crops. For the drought treatments, it was less effective. However, by dealing with the phases of growth separately, good correlation between the two methods was achieved. An important assumption in the method is that the final harvest biomass is a realistic reflection of the preceding growth, since the model method forces the estimates of growth to that point. In one germplasm line this assumption was not valid and the model‐based method did not match the sampled biomass data.
Influence of wheat and oat cultivars on the development of the cereal aphid parasitoid Aphidius rhopalosiphi and the generalist aphid parasitoid Ephedrus plagiator
Authors: FUENTES‐CONTRERAS J E , POWELL W. , WADHAMS L J , PICKETT J A , NIEMEYER H M
Published: February 2008

The effects of three wheat cultivars and two oat cultivars on the development of the cereal aphid parasitoid Aphidius rhopalosiphi De Steph. and the generalist aphid parasitoid Ephedrus plagiator (Nees) (Hymenoptera: Braconidae) were evaluated in the laboratory. The level of hydroxamic acids, a family of secondary metabolites that can affect the mean relative growth rate of cereal aphids in cereals, were measured in the different cultivars. The parasitoids were reared in Sitobion avenae (F.) (Homoptera: Aphididae), using plants grown under greenhouse conditions. A. rhopalosiphi showed a longer developmental time on wheat relative to oat cultivars. This effect was accounted for by a significant increase in the time from oviposition to pupation (mummy formation), while the duration of the pupal stage remained constant between treatments. No further effects were observed in other variables evaluating A. rhopalosiphi performance, such as adult longevity, adult body weight and secondary sex ratio. The generalist E. plagiator did not show significant differences in any of the variables analysed, both between cultivars and cereal species. Hydroxamic acids levels correlated negatively with mean relative growth rates of S. avenae, but positively with the observed developmental time of A. rhopalosiphi. The results are discussed in terms of tritrophic effects and the development of breeding programmes trying to improve plant resistance to aphids.
Observations on the maintenance and measurement of soil water in simple pot experiments and its effects on seed‐borne Fusarium culmorum seedling blight of winter wheat
Authors: HARE M C , PARRY D W
Published: February 2008

A simple method for maintaining and measuring soil water and the relationship between soil water and seed‐borne Fusarium culmorum seedling blight of wheat was investigated under controlled environmental conditions to develop reproducible assay conditions for epidemiological studies and the testing of fungicide seed treatments. For reproducibility, soil matric potential (ψm) was used to define soil water, and a range of watering regimes were tested. Treatments were watered to either a maximum ψm or to maintain a mean ψm in order to establish which parameter best described the effect that soil water had on the incidence of disease symptoms. The severity of disease symptoms was closely related to the mean soil water status and not the maximum ψm value. Watering intervals, ranging from three times a day to once every three days, did not affect this relationship. The percentage of seedlings showing symptoms after emergence (i.e. localised or extensive necrotic lesions) was inversely related to the mean ψm. With increasing soil dryness (mean ψm from ‐0.14 MPa to ‐0.17 MPa) the percentage of seedlings with post‐emergence symptoms decreased from 50% to 20%. However, as the mean ψm changed from ‐0.14 MPa to ‐0.17 MPa the percentage of seedlings dying before emergence increased from 25% to 55% in direct proportion to ψm. Overall the incidence of infection as indicated by the total number of seedlings showing symptoms either before or after emergence remained relatively constant, and was not significantly related to mean ψm.
Transmission of tomato spotted wilt virus by Frankliniella occidentalism median acquisition and inoculation access period
Authors: WIJKAMP I. , WETERING F VAN DE , GOLDBACH R. , PETERS D.
Published: February 2008

To quantify the transmission of tomato spotted wilt virus (TSWV) by Frankliniella occidentalis, the median acquisition access period (AAP50) and median inoculation access period (IAP50) were determined. These parameters were established using transmission rates obtained after AAPs and in IAPs which both ranged from 5 to 2560 min. An AAP50 of 106 min was found when larvae acquired virus from TSWV‐infected Impatiens plants. IAP50s of 58 or 137 min, respectively, were calculated when petunia or Datura stramonium leaf disks were used to test the inoculation efficiency of viruliferous thrips. The virus could successfully be acquired or inoculated in periods of 5 min. Transmission reached an optimum after an AAP of 21.3 h (AAPopt) and in an IAP of 42.7 h (IAPopt). These results show that TSWV can be acquired and transmitted efficiently by F. occidentalis in short feeding periods.
Resolution of natural hatching factors for golden potato cyst nematode, Globodera rostochiensis
Authors: DEVINE K J , BYRNE J. , MAHER N. , JONES P W
Published: February 2008

The hatching responses of Globodera rostochiensis (golden potato cyst nematode) to purified and partially‐purified preparations of natural (including the potato glycoalkaloids solanine and α‐chaconine) and artificial hatching factors (HFs) were bimodal. At least 10 HFs, mostly anionic, were resolved from potato root leachate by a combination of gel permeation and ion‐exchange chromatography. Whereas potato roots were the principal source of HFs, haulm leachate also contained such chemicals. Root leachate from aseptically‐grown potato plants lacked several HFs which were present in conventionally‐produced leachate.
Control of Chenopodium album by soil application of Ascochyta caulina under greenhouse conditions
Authors: KEMPENAAR C. , WANNINGEN R. , SCHEEPENS P C
Published: February 2008

Effects of soil application of Ascochyta caulina spores on seedlings of Chenopodium album and five cultivated plant species were investigated under greenhouse conditions as a part of a study on biological control of C. album.

Application of A. caulina spores to soils resulted in disease development on C. album and to a lesser degree on Spinacia oleracea seedlings, but not on Beta vulgaris subspecies vulgaris, Zea mays, Triticum aestivum and Pisum sativum seedlings. Affected C. album seedlings had an abnormal olive‐green colour or necrotic spots on cotyledons and hypocotyls, and were stunted or died. Affected S. oleracea seedlings were pale in colour or had necrotic spots on the cotyledons, but did not die. Time courses of disease incidence and of mortality of C. album could be described by a monomolecular model. Effects of spore density, sowing depth, soil water content, soil type and time of sowing on disease development were examined. Disease incidence and mortality were influenced by spore density, soil water content and soil type, but not by sowing depth. Spores in a moist soil maintained infectivity at least 2 wk. Spore densities of 109 to 1010 spores m‐2 were required for 50% mortality of emerged C. album plants.

Aspects of the development of A. caulina into a soil‐applied mycoherbicide are discussed.
Removal trapping to controlArtioposthia triangulata
Authors: BLACKSHAW R P , MOORE J P , ALSTON R.
Published: February 2008

Removal trapping was used to try and reduce numbers of the predatory planarianArtioposthia triangulatain polythene tunnels on a nursery and a grass field. Ten months of trapping in the tunnels failed to have any impact upon flatworm numbers but weekly catches reduced over a period of 12 weeks' trapping in grassland. The calculated residual population in the grassland (40 ha‐1) was small in comparison with that estimated from formalin sampling (940 × 1288 ha‐1). A separate field study examined the effect of trap density on catch by spacing traps at 2.5, 5, 10 and 20 m intervals. This showed that the numbers of planarians caught was inversely related to the logarithm of trap spacing. It is concluded that removal trapping is too demanding of resources to be a viable control option for this pest in commercial and agricultural situations.
Phytotoxin production by Alternaria linicola and phytoalexin production by the linseed host
Authors: EVANS N. , MCROBERTS N. , HILL R A , MARSHALL G.
Published: February 2008

Alternaria linicola produced a wide range of secondary metabolites when grown in a defined culture medium. Reverse phase chromatography fractions produced disease‐like symptoms on linseed cultivars and a range of non‐host species indicating the presence of phytotoxic components. Characterised via thin layer chromatography, these included the non‐host specific phytotoxins tenuazonic acid, alternariol monomethyl ether, tentoxin and two destruxin‐type compounds (which closely resembled destruxin A and destruxin B). The identity of four of the compounds was confirmed by two dimensional thin layer chromatography and proton nuclear magnetic resonance spectroscopy. In a second experiment, Linum leaf material infected with conidia of A. linicola and blastospores of Melampsora lini was extracted using a facilitated diffusion extraction technique. The resultant extracts contained a number of compounds which were fungitoxic to Cladosporium cladospiroides and, to a lesser extent, Alternaria brassicicola. One such compound corresponded to the phytoalexin coniferyl alcohol. Quantitative differences in the amount of the fungitoxic compounds produced between the inoculated and uninoculated resistant and susceptible host genotype combinations suggested that the production of fungitoxic compounds was greater in response to attempted colonisation. On this basis it is proposed that phytoalexin production is a component of the resistance reaction. The results from these investigations are discussed in relation to recent research on the ecology of the pathogen and the possible roles of phytotoxin production by the pathogen and phytoalexin production by the host on disease development.
Effects of foliar applications of fungicides during plant growth on grain development and grain germinability in spring barley
Authors: COCHRANE M P.
Published: February 2008

In 1990 and 1991 grain samples of spring barley were obtained from plots in which fungal diseases were controlled until ear emergence using fungicide sprays, and from comparable plots which had received no fungicide applications. The grain was stored at 10oC, and tested for germination at intervals during storage. Grain from plots treated with fungicide consistently exhibited more dormancy than grain from untreated plots. In 1992, grain development was monitored from anthesis to harvest‐ripeness in treated and untreated plots of cvs Blenheim, Camargue and Tyne. In cvs Blenheim and Camargue, grains in fungicide‐treated plots had a greater dry weight at harvest‐ripeness, and dehydrated later in development than grains in untreated plots. Neither of these differences was observed in cv. Tyne. Possible interpretations of the effects of fungicide treatment of the parent plant on the physiology of the grain are discussed.
Effect of tannin content of faba bean (Vicia faba) seed on seed vigour, germination and field emergence
Authors: KANTAR F. , PILBEAM C J. , HEBBLETHWAITE P D.
Published: February 2008

Differences in seed vigour of zero‐ and high‐tannin faba beans were investigated using 25 seed lots of 12 cultivars following earlier reports of poor emergence in the zero‐tannin types. Field emergence ranged from 54–96% indicating differences in seed vigour between cultivars all having high laboratory germination (>91%). Seed from zero‐tannin accessions with poor emergence had a higher incidence of testa and cotyledon cracking, a smaller percentage of hard seeds, more rapid water uptake, a lower percentage of vital staining of cotyledons and a greater leaching of solutes than high‐tannin types. Nevertheless, variation in these characteristics existed between cultivars and lines of both types. Seeds with more cracks in the seed coat and fewer hard seeds imbibed water more rapidly and consequently showed lower levels of vital staining and more cracks in the abaxial surface of the cotyledons. Slower imbibition in polyethylene glycol lessened the incidence of these deleterious characteristics and may provide a practical resolution to the problem of poor field emergence in zero‐tannin lines of faba bean with low seed vigour.
The Biology of the Tospoviruses
Authors: MUMFORD R A. , BARKER I. , WOOD K R.
Published: February 2008

The tospoviruses are a diverse, cosmopolitan and economically important genus of plant viruses. In the recent past, interest in the tospoviruses has been rekindled with the resurgence and expansion of tomato spotted wilt virus and the appearance of new tospoviruses, including impatiens necrotic spot. This renewed interest in the tospoviruses, accompanied with the many recent advances in plant virology techniques, particularly those utilising molecular biology, have resulted in a rapid growth of our understanding of these viruses. This paper provides a review of the tospoviruses, encompassing all the major aspects of their biology, including the recent changes in the classification of the genus and current knowledge on molecular biology, vector relations, control and diagnosis.
The separation of Liriomyza huidobrensis (Diptera: Agromyzidae) from related indigenous and non‐indigenous species encountered in the United Kingdom using cellulose acetate electrophoresis
Authors: COLLINS DOMINIQUE W.
Published: February 2008

The non‐indigenous pest leaf miner Liriomyza huidobrensis and its close relatives L. bryoniae and L. strigata belong to a natural group. These species can be separated from one another by means of protein electrophoresis on a cellulose acetate membrane. The protocol for this diagnostic assay involves staining for two enzymes, glucose‐6‐phosphate dehydrogenase (G6PDH) and leucine‐glycine peptidase (PEP). Other leaf miner species that might also be found under glass, Chromatomyia syngenesiae, C. horticola and the non‐indigenous L. trifolii and L. sativae, are clearly distinguishable from the L. huidobrensis group of species by this assay. The effect of parasitism on L. huidobrensis by Dacnusa sibirica was investigated and shown unlikely to cause misidentification of the leaf miner host. Results obtained from practical use of the assay to identify unknown specimens from ports and nurseries are compared with those obtained from flies kept in laboratory culture and used during development of the assay. No new variation was found for G6PDH. New PEP variation was found for both L. huidobrensis and L. bryoniae but this did not affect the integrity of the assay. A biochemical key to these agromyzid leaf miners is presented.
Density dependence in cereal aphid populations
Authors: MAUDSLEY M J. , MACKENZIE A. , THACKER J I. , DIXON A F G.
Published: February 2008

Long sequences of data on the incidence of cereal aphids from five European countries were analysed for evidence of density dependent processes occurring between years. Using a randomisation test (Pollard, Lakhani & Rotheray, 1987), density dependence was revealed in all (16) population censuses of Metopolo‐phium dirhodum, 60% of Rhopalosiphum padi censuses (10 of 17) but only 25% of Sitobion avenae population censuses (4 of 16). Correcting for density independent effects of weather revealed the existence of significant direct density dependence in some populations censuses where it was previously undetected. The implications of density dependence in cereal aphid populations are considered.
Transformation of blueberry without antibiotic selection
Authors: GRAHAM J. , GREIG K. , McNICOL R J.
Published: February 2008

Transformation of the blueberry cultivar North Country (Vaccinium corymbosum×V. angustifolium) was achieved using the disarmed Agrobacterium tumefaciens isolate LBA4404, containing a binary vector with an intron‐containing β‐glucuronidase (GUS) marker gene. Plant regeneration was carried out in the absence of antibiotics due to their toxicity to blueberry explants. Agrobacterium contamination was controlled by dipping the explants in antibiotics and rinsing in sterile distilled water. Once regeneration had been achieved, the plantlets were placed on to medium containing the antibiotic ticaricillin at 250 mg litre‐1 to control and try to eliminate any remaining Agrobacterium. Selection of regenerating explants expressing GUS was achieved by growing the plant material for 2 days on a medium containing 4‐methyl umbelliferyl glucuronide (MUG), and examining the medium under UV light to detect fluorescent activity. From the 19 explants showing signs of regeneration, seven produced fluorescent patches on MUG medium. From the selected explants, five plantlets were found to express the GUS gene as detected by fluorometric and histochemical analysis. PCR was used to confirm the presence of the GUS and/or NPTII marker genes after 2 years in culture. Bacterial contamination isolated from plant material (which appeared free of contamination) was examined for GUS activity and analysed using PCR with GUS and NPTII specific primers, but no positive results were obtained.
Common cabbage resistance mechanisms against the diamondback moth: still an open book?
Authors: VERKERK R H J. , WRIGHT D J.
Published: February 2008

Despite the extensive research on host plant resistance of Brassica oleracea L. var. capitata (common cabbage) against Plutella xylostella L. (diamondback moth), knowledge of the resistance mechanisms involved remains incomplete. While robust evidence exists for the physical (antixenosis) mechanisms believed to cause resistance in glossy‐leaved breeding lines, the one mechanism proposed in the literature to date (polar leaf extracts causing antibiosis) at best only explains a part of the resistance observed in two partially‐resistant normal‐bloom breeding lines in the field and the evidence is suggestive rather than direct.

Evidence from other host plant resistance studies involving P. xylostella is discussed and the other possible mechanisms are considered with the aim of providing a context for further investigations on host plant resistance mechanisms against P. xylostella.
Impact of density of Aphis craccivora (Aphididae) on growth and yield of susceptible and resistant cowpea cultivars
Authors: ANNAN I BILLY , SCHAEFERS GEORGE A , TINGEY WARD M
Published: February 2008

Impact of initial density of cowpea aphid Aphis craccivora Koch (Aphididae) at infestation on the growth and yield of aphid‐susceptible cowpea cultivar ICV‐1 and aphid‐resistant cultivar ICV‐12, was investigated. Plants at the seedling, flowering and podding stages of development were infested with five aphid densities consisting of 0, 2, 5, 10 and. 20 aphids per plant and maintained for 22 days. Extended leaf heights of plants and aphid counts were recorded at 7, 12, 17 and 22 days after infestation. Two crop growth parameters (biomass duration and leaf area duration), and two plant yield parameters (number of pods per plant and number of seeds per pod) were recorded. Due to the occurrence of parthenogenesis and changes in population dynamics during infestations, aphid densities were converted into cumulative cowpea aphid‐days, to facilitate data analyses and interpretation. ANOVA indicated that there was significant (P=s 0.05) difference in aphid‐day accumulations between the two cultivars when infested at the seedling stage. Accumulations on cv. ICV‐1 were greater than on cv. ICV‐12. However, no such differences between the cultivars were detected when plants were infested at flowering and podding stages. Therefore, the seedling stage was used for comparisons of the impact of cowpea aphid‐days on the growth and yield parameters of the two cultivars. At the 95% confidence intervals, ICV‐12 plants were consistently taller than ICV‐1 plants. Infested ICV‐1 seedlings showed stunting and other growth deformities which were not observed on ICV‐12 plants. Regression analyses revealed substantial reductions in the growth and yield parameters of ICV‐1 relative to ICV‐12. Overall, cowpea aphid‐days provided a convenient and reliable method for studying the aphid population dynamics and the subsequent impact on plant growth and yield performance.
Inoculum sources of Fusarium oxysporum f.sp. asparagi in asparagus production
Authors: BLOK WIM J , BOLLEN GERRIT J
Published: February 2008

Fusarium oxysporum f.sp. asparagi (Foa) incites crown and root rot of asparagus which causes early decline of asparagus plantings. The aim of the present study was to identify the main inoculum sources of the pathogen in the Netherlands.

As has been reported for foreign seed lots, Dutch seed lots can be infested with Foa at low levels. We found that seed infestation occurs mainly during the seed harvesting process through infested soil adhering to fallen berries.

Soil samples from 59 fields without a history of asparagus growing and differing in their distance from asparagus plantings were tested for infestation with Foa, using a bioassay with asparagus as a bait plant. A high correlation was found between the incidence of infestation and proximity to asparagus fields; Foa was found in 69% of the samples from fresh fields in an asparagus production centre, and in only 6% of the samples from fields at a distance of 1 km and more from asparagus fields and outside a production centre.

To evaluate planting material as an inoculum source of Foa, 49 lots of one‐year‐old crowns from 23 nurseries were collected and rated for disease symptoms. Infestation was found to be common with only two lots free of symptomatic plants. Most of the lots had more than 75% of symptomatic plants. Although most of the plants were infested, they showed only slight root rot symptoms. The procedure for production of Foa‐free planting material is discussed.

Persistence and infestation of asparagus root residues in former asparagus fields was assessed by retrieving the residues from eight former asparagus fields with an asparagus‐free period of one to 25 years, and three fields with a standing asparagus crop. Even after an asparagus‐free period of 25 yr asparagus root residues were retrieved from soil, although at low levels. Mean population densities of Fusarium spp. declined from 2 times 106 to 1 times 105 colony forming units g_1 air‐dry root tissue during the first 10 years and were still > 104 c.f.u. g“1 air‐dry root tissue 20 to 25 yr after asparagus produced was stopped. The population was dominated by F. oxysporum. Eighty‐three of the 112 isolates (74%) of F. oxysporum belonged to the forma specialis asparagi. The proportion of Foa in the population did not decrease in time. It was concluded that persistence of Foa in asparagus root residues is a major reason for its long‐term survival.
Comparison between woody indexing and a rapid hybridisation assay for the diagnosis of little cherry disease in cherry trees*
Authors: EASTWELL K C , BERNARDY M G , LI T S C
Published: February 2008

Sweet cherry (Prunus avium) and sour cherry (Prunus cerasus) trees from orchards in the Kootenay and Okanagan Valleys of British Columbia, Canada were assayed for the presence of little cherry disease by three different methods: Northern blot analysis of double‐stranded RNA, woody indexing for fruit symptoms on sweet cherry cv. Lambert, and woody indexing for foliar symptoms on cv. Canindex 1. Results of the three methods were in agreement for 85% of the samples. Of the 78 orchard trees tested, double‐stranded RNA isolated from 48 trees hybridised with a radiolabeled cloned probe specific for little cherry disease. When the 48 trees were tested by woody indexing, buds from 41 trees induced fruit symptoms on cv. Lambert, but only 32 yielded foliar symptoms on cv. Canindex 1 under the conditions of the experiment. Of the 30 orchard trees that did not yield a positive response to the Northern blot analysis, 26 samples were negative on cv. Lambert and 26 were negative on cv. Canindex 1. Northern blot analysis of the 78 cv. Lambert indicator trees revealed that there was an absolute correlation between the presence of little cherry disease‐associated double‐stranded RNA and the development of typical little cherry disease symptoms on the indicator trees. Reliability of woody indexing of orchard samples was impaired by poor transmission of the disease from the inoculating bud to the indicator tree. Woody indexing with cv. Canindex 1 was particularly prone to a large number of apparently erroneous negative results. Of the three protocols used, diagnosis of little cherry disease by Northern blot analysis was found to be the most reliable and offered a greatly accelerated means of diagnosis.
A review of the pre‐oviposition behaviour of small cabbage white butterfly, Pieris rapae(lepidoptera: Pieridae)
Authors: HERN ALAN , EDWARDS‐JONES GARETH , MCKINLAY RODERICK G
Published: February 2008

This paper reviews the literature concerning the ovipositional behaviour of Pieris rapae (small cabbage white butterfly) and where appropriate considers results from studies involving other butterflies. The paper considers searching behaviour, stimuli utilised in host plant finding and identification and concludes with a general section on the role of learning and prior experience in ovipositional behaviour.
Development of an apparatus and protocol for the efficient isolation of bacteria and yeasts that attach to Botrytis cinerea germlings
Authors: COOK DARRYL W M , LONG PETER G , GANESH SIVA , NEILSON HUGH F
Published: February 2008

An apparatus and protocol for the efficient and consistent isolation of bacteria and yeasts with the ability to attach to germlings of Botrytis cinerea is described. The study focused on minimising microbial contamination by bacteria or yeasts which do not attach to the pathogen B. cinerea but which interact with materials used in the equipment and would otherwise be isolated along with target microbes. After development, the assay reduced the contamination rate to 1–2 cells per 100 added and this was found to be a satisfactory level for the selection of microbial attachers to fungal hyphae. One or more phenotypes of microbes that adhered to B. cinerea germlings were found in 97% of the 70 samples collected from phylloplane washings and processed using this assay.
Control of the mushroom pests Lycoriella auripila (Diptera: Sciaridae) and Megaselia halterata (Diptera: Phoridae) by Steinernema feltiae (Nematoda: Steinernematidae) in field experiments
Authors: SCHEEPMAKER J W A , GEELS F P , SMITS P H , GRIENSVEN L J L D VAN
Published: February 2008

The nematode Steinernema feltiae (Nematoda: Steinemematidae) was tested for its ability to control two main mushroom pests i.e. the sciarid Lycoriella auripila (Diptera: Sciaridae) and the phorid Megaselia halterata (Diptera: Phoridae) in growing‐rooms filled with spawned compost. A clear difference between female and male sciarid control was observed. A nematode application 1 day after casing preceded by an application 1 day before casing on the compost caused an almost complete control (97%) of the F1‐generation of female sciarids. The F2‐generation of females was similarly controlled (95%) by an application 7 days after casing. A dosage of 1 × 106nematodes m‐2was found to be equally effective as higher dosages. Diflubenzuron remained active throughout entire the cropping period with high sciarid mortality rates varying from 72% to 99%.

Phorid control was variable and seemed to depend on the presence of sciarids. In one occasion the control rate of F2‐generation phorid larvae was 75% and was possibly caused by the presence of new infective juvenile nematodes recycled in F2‐generation sciarid larvae. Diflubenzuron did not significantly reduce phorid numbers.
Mycocentrospora acerina in carrots; Effects of crop rotation on disease incidence
Authors: HERMANSEN ARNE , AMUNDSEN TERJE , TAKSDAL GUDMUND , DRAGLAND STEINAR , SYNNEVÅG GRY , FLØNES MONS , SUNDHEIM LEIF
Published: February 2008

Four experimental sites located in different climatic regions in Norway were inoculated with Mycocentrospora acerina in 1985. In 1986, crop rotation experiments including carrot, barley, grass, red clover, onion and potato, were established at these sites. Incidence of M. acerina on the foliage and the roots of carrots after storage were recorded in 1989/90 and 1994/95.

The 3 yr rotation only slightly reduced the inoculum of M. acerina in the soil. Red clover and grass were the most effective crops in reducing the inoculum, potato and barley were less effective, and onion had no effect on the inoculum. Differences in M. acerina infection on carrots between 3, 6 and 8 yr of rotation with barley and grass were not statistically significant.
Production of phytotoxic spore germination liquids by Alternaria brassicae and A. brassicicola and their effect on species of the family Brassicaceae
Authors: COOKE D E L , JENKINS P D , LEWIS D M
Published: February 2008

Experiments assessed the susceptibility of Brassica spp. and non‐Brassica spp. in the family Brassicaceae to infection by Alternaria brassicae and A. brassicicola, and determined the sensitivity of the host species to spore germination liquids (SGLs) produced by the pathogens on B. napus leaves. There was a wide range of sensitivity to the pathogens. Brassica spp. were generally more susceptible, and some non‐Brassica spp. (Barbarea vulgaris and Capsella bursa‐pastoris) were immune to A. brassicicola. Measurable damage was caused by SGLs but with significant variation between host species. Non‐hosts and weak hosts also showed necrosis. It was concluded that, in the case of both pathogens, the toxic factors in these SGLs were host‐selective. Selectivity in toxin production was also demonstrated in relation to the host surface or growing medium in which spores germinated. A substantial amount of toxin was produced on all Brassicaceae tested but not on unrelated species (Triticum aestivum, Pisum sativum and Lycopersicon esculentum). Neither pathogen produced measurable amounts of toxin when cultured in Czapek (Dox) broth.
A novel method for detection of viable zoospores of Pythium in irrigation water
Authors: WAKEHAM A J , PETTITT T R , WHITE J G
Published: February 2008

A membrane filtration test has been developed for the detection of viable zoospores of Pythium species. Zoospore suspensions were filtered through 5 (m nitrocellulose membranes and the membranes incubated overnight in 0.07 m glucose, rifamycin (30 mg litre‐1) and pimaricin (100 mg litre‐1). Zoospore germlings were detected using a polyclonal antiserum, raised to mycelial surface washings of five Pythium spp., and visualised with Sigma fast red. The assay gave positive results for all Pythium spp. tested and also to zoospores of Phytophthora cryptogea. Of 10 fungal species isolated from commercial irrigation water, two were detected by the polyclonal antiserum in ELISA tests but only one produced detectable zoospore germlings. The latter isolate was later identified as a Pythium sp. Irrigation water samples collected from commercial UK nurseries yielded zoospores of both Pythium and Phytophthora spp. which, using the assay, were positively identified. Results indicated greater sensitivity than was seen with conventional plating methods. This is a test which could be adapted for on‐site use in commercial nurseries.
Role of a novel type of double infection in the geminivirus‐induced epidemic of severe cassava mosaic in Uganda
Authors: HARRISON B D , ZHOU X. , OTIM‐NAPE G W , LIU Y. , ROBINSON D J
Published: February 2008

To study the cause of the current epidemic of severe mosaic in Ugandan cassava, PCR analysis was used to detect and identify African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV) and the recently reported recombinant geminivirus (UgV), which is derived from ACMV and EACMV, in leaf extracts from cassava plants grown from cuttings in the glasshouse at Dundee. The cuttings were collected from plants showing symptoms of different severities and growing at different sites in Uganda inside, at the periphery of, and outside, the area affected by the epidemic. ACMV occurred throughout the nine districts sampled but UgV was detected only in the area affected by the epidemic. EACMV was not found in Uganda. Most plants containing ACMV alone expressed mild or moderate mosaic, whereas very severe mosaic developed in most plants containing UgV plus ACMV and a few of those containing UgV only. Very severe mosaic in cassava from southern Sudan was likewise associated with co‐infection by UgV and ACMV. The very severe disease was reproduced by graft‐inoculating geminivirus‐free cassava with UgV plus ACMV; plants inoculated with either UgV or ACMV developed severe or moderate symptoms, respectively. Unlike ACMV, Malawian EACMV did not enhance the severity of symptoms induced by UgV. However, a very severely affected plant from Ukerewe Island, Tanzania, contained ACMV and EACMV but not UgV. UgV attained a much greater concentration in cassava than did ACMV but the opposite occurred in Nicotiana benthamiana. In neither host was total virus antigen concentration affected by co‐infection.

Factors affecting the genesis, selection and spread of UgV are discussed. The evidence indicates that UgV is probably of relatively recent origin, that such variants do not appear often, and that the current epidemic has resulted from the rapid spread of UgV to infect plants and to invade regions in which ACMV already occurred. The novel type of virus complex so produced, consisting of an interspecific recombinant virus (UgV) and one of its parents (ACMV), typically has even more severe effects than UgV alone.
Aetiology of tobacco leaf curl in southern Africa
Authors: PAXIMADIS M. , REY M E C
Published: February 2008

Symptom variability of tobacco leaf curl disease has been reported by numerous researchers worldwide. It has been suggested that the different types of leaf curl may be caused by more than one geminivirus strain (McClean, 1940; Osaki & Inouye, 1981), although no evidence exists to support this hypothesis. Previously, several tobacco plants exhibiting a range of leaf curl symptoms were collected from South Africa and Zimbabwe and grouped according to symptomology (Paximadis, Dusterwald, Duyver & Rey, 1997). Three classes (I, II & III) of leaf curl were distinguished, and class I leaf curl from South Africa was shown not to be associated with a geminivirus infection, but was consistently associated with 12 double‐stranded RNA species, now believed to be of phytoreovirus origin. In this study, symptom descriptions of class II and III leaf curl have been reported, and, triple‐antibody sandwich ELISAs, dot‐blot hybridisation analysis, PCR, double‐stranded RNA analysis and seed‐transmission experiments were employed to screen class II and III tobacco plants for geminiviruses or other possible causal agents. Class II leaf curl symptoms were shown not to be associated with a geminivirus infection or with any double‐stranded RNA species. Class II leaf curl symptoms were however transmitted through seed. Class III leaf curl plants tested negative for double‐stranded RNA, but tested positive in PCR, dot‐blot hybridisation and ELISAs for geminiviruses. It is suggested that ‘tobacco leaf curl’ is not a single disease but rather a wide collection of symptoms incited by different agents, and should therefore be described as a disease complex or syndrome.
Influences of compost and casing layer depths on the mechanical properties of mushrooms
Authors: NOBLE R. , RAMA T. , MILES S. , BURTON K S. , STEPHENS T M. , REED J N.
Published: February 2008

The mushroom growing bed consists of an underlying compost which is covered with casing (a peat and chalk or lime mixture) to induce fruit‐body formation. The influences of the depths of the compost and casing layers on the mushroom texture, susceptibility to bruising, and ease of detachment from the growing bed surface were investigated. Textural properties were determined on cubes of cap tissue and detachment torque was determined by using an instrumented rotating suction cup which was lowered on to the caps. The proportion of mushrooms which detached at the base from the bed surface was recorded, since this is an important parameter for an automatic (robotic) harvesting system. Shallow casing resulted in mushrooms that were firmer and less likely to deform plastically, but that showed greater discolouration after a standard bruising treatment. Shallower casing also increased the proportion of mushrooms that detached at the base. Increasing the depth of compost produced firmer mushrooms, significantly increased the detachment torque and reduced the proportion of mushrooms detached at the base. The proportion of mushrooms that detached at the base correlated negatively with the plastic deformation of cap tissue. A positive correlation was found between mushroom dry matter content and tissue firmness.
The morphology of bracken (Pteridium aquilinum (L.) Kuhn) in the North York Moors—a comparison of the mature stand and the interface with heather (Calluna vulgaris (L.) Hull) 2. The rhizome
Authors: WHITEHEAD S J. , DIGBY J.
Published: February 2008

The rhizome system of mature bracken (Pteridium aquilinum (L.) Kuhn) contains large reserves of both biomass (mean 8.63 kg m˜2 fr. wt) and buds (mean 565 m‐2) which are largely responsible for both its persistence and its often rapid rates of vegetative encroachment. Within areas such as the North York Moors the spread of bracken into areas previously dominated by heather and grass is considered undesirable because of reduced land value in terms of both agriculture and ecological diversity.

In this paper we describe the morphology of bracken rhizome within a mature bracken stand, and at advancing and stationary stand margins where bracken‐heather interfaces occur. Stationary margins, i.e. those where bracken is not encroaching into heather at a significant rate, often have morphological characteristics intermediate to those of a mature stand and an advancing margin. In the mature stand rhizome biomass is dominated by carbohydrate‐storing long shoots which comprise 63% of the total fresh weight, whilst the majority of rhizome buds (89% of all active and 86% of all dormant buds) are found on frond‐bearing short shoots. At the margins of a bracken stand the proportion of rhizome which is composed of long shoots is even greater, and that of short shoots small relative to that in the mature stand. More transitional shoots are also found at the stand margins. Hence close to the margin a greater proportion of fronds is found on transitional rhizome than is the case in more mature parts of the stand.

The majority of buds on all types of rhizome are in a dormant state. The proportion of buds which are active is, however, greater on long and transitional shoots than on short shoots. Hence, a larger proportion of buds are active close to the margin where the rhizome is composed less of short shoots than is the case further into a mature stand.

The differences in the morphology of bracken in a mature stand and at the stand margins which are identified here support the idea of controlling bracken at stand margins in preference to the spraying of large areas of dense, mature bracken. Morphological differences include an increased proportion of active buds, greater frequency of fronds per unit rhizome biomass, reduced biomass reserves. Improved conditions for the re‐invasion and re‐establishment of alternative vegetation are also available at stand margins in comparison with the centre of a dense bracken stand.
Callus tissue of Solanum tuberosum L. cultured in the presence of the pyrethroid deltamethrin
Authors: FIDALGO F. , SANTOS I. , SALEMA R.
Published: February 2008

The effect of Decis (deltamethrin as active ingredient) on callus tissue of Solanum tuberosum L. cv. Désirée was studied. Decis is an agrochemical currently used on field grown potato plants to control the Colorado beetle, a potato pest. Deltamethrin added to the culture medium interferes with the behaviour of callus tissue. After 5 h of culture, the level of total proteins was higher in treated tissue than in the control, and SDS‐PAGE showed that deltamethrin promoted the increase of some soluble proteins. After 24 h and 14 days of culture, the level of total proteins became similar in both treated and control material. This similarity between control and treated tissues, after 14 days of culture, occurred as a result of the treatment with deltamethrin which caused a decrease of soluble proteins, but an increase in insoluble proteins whereas the opposite was observed for control callus. SDS‐PAGE of both soluble and insoluble proteins showed that only quantitative dissimilarities occurred. This longer treatment also increased the chlorophyll content. Ultrastructural study of the cells revealed that tissue callus cultured for 14 days in the presence of deltamethrin had plastids containing a more developed membranous system, with a higher number of grana and with more compartments than in control cells. Deltamethrin also promoted the abundance of vesicles associated with dictyosomes.

This response of the callus tissue to Decis added to the callus medium parallels the behaviour of potato plants treated with this agrochemical under field conditions (Fidalgo, Santos & Salema, 1993).
Variation and inheritance of resistance to cypress aphid, Cinara cupressi Buckton in Cupressus lusitanica Miller
Authors: KAMUNYA S M , DAY R K , CHAGALA E. , OLNG'OTIE P S
Published: February 2008

Cupressus lusitanicaseedlings from open‐pollinated seeds of 18 families were inoculated with day‐old first instarCinara cupressi.Aphid survival was used to determine the genetic basis and inheritance of resistance to the insect. There was marked variation in aphid survival both between and within families. An individual‐tree narrow‐sense heritability of 0.76 ± 0.30 shows strong additive genetic control which could allow effective selection and breeding for resistance. Resistant parents produced resistant progeny while susceptible parents produced susceptible progeny. There were notable exceptions as some susceptible parents produced highly resistant progeny, indicating that they had acquired pollen from resistant neighbours. Recovery of aphid damaged trees is evident implying that care should be taken in selecting for resistance. The strong additive variance and potentially high heritability indicate that one cycle of selection may yield a resistant population, while intraspecific crossing may give better results. Implications of the results in aC. lusitanicabreeding programme are discussed.
Diversity among the coat proteins of luteoviruses associated with chickpea stunt disease in India†
Authors: NAIDU R A , MAYO M A , REDDY S V , JOLLY C A , TORRANCE L.
Published: February 2008

Chickpea stunt is an important virus disease of chickpea in the Indian subcontinent which is thought to be caused by infection with a luteovirus. Samples of diseased chickpea plants were collected from different chickpea growing regions of India and analysed with a panel of monoclonal antibodies to potato leafroll, beet western yellows and barley yellow dwarf (RPV strain) luteoviruses. The results suggested that more than one luteovirus was present in chickpea crops near ICRISAT Asia Center, Hyderabad. Aphid transmission tests resulted in the separation of two distinct isolates from these samples. One of them (isolate L) was more efficiently transmitted by Myzus persicae than the other (isolate IC). Nucleotide sequence analysis of DNA obtained by reverse transcription‐polymerase chain reaction (RT/PCR) amplification revealed that the amino acid sequence of the coat protein of isolate L was 94% identical to that of beet western yellows virus, whereas the coat protein sequence of isolate IC was 82% identical to that of isolate L and 80% identical or less to those of the coat protein of other luteoviruses. Using newly designed “universal luteovirus primers”, a minor sequence variant of isolate IC, which was 96% identical to it in part of the coat protein gene, was detected in the same location during the next season. Only isolate IC could be detected in samples from other locations by either serological or nucleotide sequence analysis.
Studies on inheritance of resistance and allelic relationships for strain 2 of pigeonpea sterility mosaic pathogen
Authors: SRINIVAS T. , REDDY M V , JAIN K C , REDDY M S S
Published: February 2008

Inheritance of resistance and allelic relationships were studied in three resistant pigeonpea sources for strain 2 of sterility mosaic pathogen. The resistant genotypes (ICP 7035, ICP 7349 and ICP 8850) were crossed with susceptible genotypes (BDN1 and LRG30) to determine the inheritance of resistance. The resistant and susceptible genotypes were also crossed among themselves to obtain information on their allelic relationships. Parents, F1 and F2 generations were sown in pots and screened using infector‐hedge technique. Observations in parents, F1 and F2 generations, indicated dominance of resistance in certain crosses and the dominance of susceptibility in others. Disease reaction appeared to be governed by two independent non‐allelic genes, with at least three multiple alleles, at one of the loci.