bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of cover crops, weeds and plant debris on development ofMycocentrospora acerinain caraway
Authors: EVENHUIS A. , VERDAM B. 
Published: February 2008

SummaryThis paper reports on the search for inoculum sources ofMycocentrospora acerinaon caraway (Carum carviL.). Obvious suspects are cover crops of biennial caraway and preceding crops of annual caraway. Other suspects are weeds in or alongside the field. Finally, survival structures of the fungus, chlamydospore chains, packed in plant debris or naked, are suspected.M. acerinais able to infect many plant species, including cover crops of caraway such as spinach for seed production and peas. However, the agronomical suitability of a crop to serve as a cover crop of biennial caraway proved to be a more important factor in determining caraway yield than the susceptibility of the cover crop toM. acerina.This finding was corroborated by the fact that spinach and peas as preceding crops had no significant effects onM. acerinadevelopment in spring caraway sown the next year. Dill, barley and four weed species were found as new hosts ofM. acerina.The role of weed hosts, susceptible crops and plant debris in the survival of the fungus in years without caraway is discussed. Caraway sown on soil containing infested caraway straw, infested debris of other plant species or chlamydospores grown in pure culture, became infected byM. acerina.Only high inoculum densities of chlamydospores in the soil caused severe damping‐off of caraway seedlings. The opportunity for disease management by agronomical means is quite limited.
Ipomoea crinkle leaf curl caused by a whitefly‐transmitted gemini‐like virus
Authors: COHEN J. , MILGRAM M. , ANTIGNUS Y. , PEARLSMAN M. , LACHMAN O. , LOEBENSTEIN G. 
Published: February 2008

SummaryA whitefly‐transmitted infectious agent, associated with geminate particles, induced distinct symptoms on several Ipomoea species, but not on I. batatas cv. Georgia Jet. The virus was transmitted by Bemisia argentifolii in a persistent manner and by grafting, but not mechanically. No transmission to species outside Ipomoea was obtained. Extracts from infected Ipomoea plants hybridised with a bean yellow mosaic virus riboprobe and a tomato yellow leaf curl virus riboprobe, although not so strongly as hybridisation of these riboprobes with extracts from plants infected with the homologous viruses. Based on host range, we consider this virus to be distinct from sweet potato leaf curl virus reported from the Far East, and propose it be named “Ipomoea crinkle leaf curl virus” (ICLCV).
Quantifying the impact of polyphagous invertebrate predators in controlling cereal aphids and in preventing wheat yield and quality reductions
Authors: HOLLAND JOHN M , THOMAS S R 
Published: February 2008

SummaryExclusion barriers were used to manipulate numbers of polyphagous invertebrate predators so that their impact on cereal aphids and consequently wheat yield and quality could be examined. Experiments were conducted within the framework of the LINK Integrated Farming Systems Project which allowed comparisons to be made between the integrated and conventional farming systems under examination on a study farm in Hampshire, UK. Only in 1995 were the numbers of aphids per tiller, the aphid peak and rate of increase to the peak significantly greater in the exclusion areas where the density of polyphagous predators had been reduced. The maximum increase in aphids as a result of excluding polyphagous predators was 31%, which was equivalent to 130 aphid days. However, the polyphagous predators did not reduce the number of tillers infested. The relatively low impact of polyphagous predators was attributed to the aphid population phenology and greater effects may have been found had aphids infested the crops earlier in their development. Sowing date was shown to govern the time over which a crop may be susceptible to yield loss from aphids, with later‐drilled crops being more susceptible to late‐summer aphid infestations.Aphid numbers rarely affected grain yield but were found to be related to some grain quality parameters, but reducing polyphagous predators had no direct impact on grain yield or quality even where the aphid burden increased.The peak period of activity and density differed between the species of Carabidae, Staphylinidae and Araneae consequently influencing their relationship with the aphids. Some negative correlations were found between these groups of polyphagous predators and aphids. Species composition and abundance differed between fields thereby influencing the level of aphid predation. The exclusion barriers were most effective at reducing numbers of Carabidae although numbers of Staphylinidae and Araneae were also reduced. The consequences for Integrated Crop Management are discussed.
Inheritance of components of partial resistance of barley to Rhynchosporium secalis with particular reference to race specificity
Authors: KARI ANDREAS G. , GRIFFITHS ELLIS 
Published: February 2008

SummarySix spring barley cultivars with no known genes for resistance to specific virulences but varying in partial resistance to Rhynchosporium secalis, were crossed in all combinations (6 × 6 diallel including reciprocals). In addition to seeds from naturally selfed plants, seeds of all parent cultivars were also produced by artificial selfing (emasculation followed by pollination using pollen from the same cultivar). This ensured comparability between seeds of parents and F1. Both sets of parents, F1 and F2 families were grown in the field as single spaced plants and inoculated at Zadoks growth stage 49 with spore suspensions (2 × 106 spores ml‐1) of three races (pathotypes) of R. secalis (Zadoks, Chang & Konzak, 1974). Components of partial resistance, incubation period (ICP), infection frequency (IF) and spore production per lesion (SP/L) were assessed on each plant.There were highly significant differences for all three components of partial resistance in both sets of parent cultivars but rank order in both sets was similar as evidenced by correlation coefficients, r= 0.96 for ICP and IF and r= 0.87 for SP/L. All three components of partial resistance were strongly correlated with NIAB (National Institute of Agricultural Botany, Cambridge, UK) resistance ratings.Means of F1 and F2 families were correlated with mid‐parent values for ICP and IF but not SP/L. No difference in aggressiveness was found between races but for each component of partial resistance there was a significant interaction between race and parent cultivar (artificial selfs) and, for IF and ICP, a significant interaction between race and F1 family. There was no evidence of interaction between parent (natural selfs) and race nor between race and F2 family.Examination of genetic control of resistance showed evidence of strong additive effects (combining ability) in both F1 and F2 for ICP and IF but not for SP/L. There was no evidence for maternal or reciprocal differences, but there was evidence for dominance effects although their nature differed between components of partial resistance and between F1 and F2 generations. In the F1, but not the F2 generation, several elements of dominance (direction, distribution of dominant genes between parent cultivars, specific combining ability) showed for ICP or IF (but not SP/L) significant interaction with race.
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) 1. The fronds
Authors: WHITEHEAD S J. , DIGBY J. 
Published: February 2008

SummaryThe encroachment of bracken (Pteridium aquilinum (L.) Kuhn) into areas previously dominated by heather represents a threat to the ecology, agricultural economy and landscape value of many UK upland areas, including the moorland of the North York Moors National Park.The morphology of bracken, within a mature stand and at several bracken‐heather interfaces, has been studied at a number of sites within the National Park. Differences have been found in the frond growth of bracken in a mature stand, at stationary stand margins, and at advancing stand margins where bracken is encroaching into heather.Frequency of fronds present on bracken rhizome growing at a stationary stand margin close to the interface with heather (1–2 m behind the boundary) are approximately the same as those found within a mature stand. At advancing margins (again 1–2 m behind the boundary), maximum frond densities were often found to exceed those present in either a mature stand or at a stationary margin. Frond numbers decline rapidly at the stand margins as distance from the stand increases. This is especially true where the front is stationary and bracken is not encroaching into heather at a significant rate. Maximum frond heights in a mature stand consistently exceed those at stand margins (even 1–2 m into the stand) and are greater at stationary margins than at advancing margins.Outlying fronds at the edges of bracken stands are generally present in greater numbers, and further into the area dominated by heather, where the margin is advancing. Heights of outlying fronds fall as distance from the bracken stand increases, as does stipe length. Fronds at the edges of bracken stands emerge each spring before those further into the stand and are therefore particularly vulnerable to frost damage. Outlying fronds are not, however, the first to emerge. Early emerging fronds reach their maximum height and eventually become senescent before later emerging fronds. Whilst most fronds emerge before the end of June a few fronds continue to emerge throughout the summer.Frond densities close to the edges of bracken stands (1–2 m into the stand) are comparable to those in a mature stand. At advancing stand margins frond densities generally exceed those in a mature stand, suggesting that a large number of potential entry points for foliage‐applied herbicides are available for bracken control at the stand margins. The ratio of potential uptake points to biomass of rhizome is also greatest at the edges of the stand, and the canopy 1–2 m into the stand is usually almost completely closed. It is possible therefore, the efficacy of herbicides could be improved by the use of small scale applications, using tractors or hand‐held sprayers, close to the margins of bracken stands.
The influence of nitrogen fertiliser on the population development of the cereal aphids Sitobion avenae (F.) and Metopolophium dirhodum (Wlk.) on field grown winter wheat
Authors: DUFFIELD S J , BRYSON R J , YOUNG J E B , SYLVESTER‐BRADLEY R. , SCOTT R K 
Published: February 2008

Summary.The effect of nitrogen fertiliser on populations of the cereal aphidsSitobion avenaeandMetopolophium dirhodumon winter wheat was investigated in a three year field experiment. Naturally occurring aphid populations were monitored on three nitrogen treatments; none, nitrogen application using Canopy Management guidelines (130–210 kg ha‐1) and conventional practice (190 kg ha‐1). Inoculations of laboratory rearedS. avenaewere used to enhance field populations on half the plots.Natural populations ofM. dirhodumremained below the current UK spray threshold level of two‐thirds of shoots infested at the start of flowering, or five aphids per shoot in all years, whilst populations ofS. avenaeexceeded the threshold in all years.The response of the two species to nitrogen differed. Significantly higher populations ofM. dirhodumwere recorded in both treatments which received nitrogen in all years, whilst the response ofS. avenaevaried between years. In 1994 and 1995 when environmental conditions favoured aphid development, higher populations were recorded in the two treatments which received nitrogen. In 1993 when high rainfall created unfavourable conditions, higher populations were recorded in the plots receiving no nitrogen.Differences in peak density and cumulative aphid index ofS. avenaeresulted from differences in the rate of population increase between ear emergence and peak density on the different treatments. Populations prior to ear emergence were higher in the plots which received nitrogen but the differences were not statistically significant. There was no evidence of a difference in the timing of population decline in the different treatments.In 1993 higher levels of infection by entomopathogenic fungi were observed in all treatments. Significantly higher levels of infection were recorded in the treatments receiving nitrogen, which may have accounted for the lowerS. avenaepopulations recorded. It is possible that the larger canopies recorded in these treatments produced conditions which favoured infection by fungi, thereby limiting aphid population growth.The results indicate that application of nitrogen increases natural populations ofM. dirhodum, and under favourable conditions, populations ofS. avenae.However, in suboptimal climatic conditions, the application of nitrogen fertiliser can lead to lower populations of 5.avenae.The data also suggest that there is no consistent difference between a conventional and Canopy Managed approach to nitrogen fertiliser use in terms of the risk of infestation by cereal aphids.
Detection and relationships of cotton leaf curl virus and allied whitefly‐transmitted geminiviruses occurring in Pakistan
Authors: HARRISON B D , LIU Y L , KHALID S. , HAMEED S. , OTIM‐NAPE G W , ROBINSON D J 
Published: February 2008

Summary.A stock culture of cotton leaf curl virus from Pakistan (CLCuV‐PK), was transmitted by whiteflies (Bemisia tabaci) to seven plant species, including French bean, okra, tobacco and tomato, and caused vein thickening and leaf curl symptoms. It was readily detected in triple antibody sandwich ELISA (TAS‐ELIS A) by 11 out of 31 monoclonal antibodies raised against the particles of three other geminiviruses: African cassava mosaic, Indian cassava mosaic and okra leaf curl viruses. Reaction strength was enhanced when the tissue extraction fluid contained sodium sulphite. Minor variations in epitope profile were found among virus isolates from cotton (Gossypium hirsutum) collected from different districts in Pakistan over a 5‐year period. These epitope profiles were distinguishable from that of cotton leaf curl virus from G. barbadense in southern India but indistinguishable from the profiles of viruses causing yellow vein disease of okra in India or Pakistan, or leaf curl of okra {Abelmoschus esculentus), Hibiscus tiliaceus, radish or sunflower in Pakistan, suggesting that these plants are putative natural hosts of CLCuV‐PK. The viruses in cotton, and in okra with leaf curl or yellow vein symptoms, were also detected by PCR with three pairs of CLCuV‐PK‐specific primers.Five additional whitefly‐transmitted geminiviruses were found among isolates from 11 other naturally‐infected species in Pakistan, and were distinguished by their epitope profiles. These viruses were associated, respectively, with tobacco leaf curl, squash yellow blotch, tomato yellow leaf curl, watermelon leaf crinkle and soybean yellow mosaic diseases. The first four of these viruses were detected readily by PCR with geminivirus general primers but only weakly, if at all, with two pairs of CLCuV‐PK‐specific primers. Pakistani crops are infected with a range of distinguishable but relatively closely related whitefly‐transmitted geminiviruses, some of which resemble those found in India.
Novel resistances to four potyviruses in tuber‐bearing potato species, and temperature‐sensitive expression of hypersensitive resistance to potato virus Y
Authors: VALKONEN J P T 
Published: February 2008

Summary.Novel potyvirus resistance specificities were found in eight tested wild potato species (clones): hypersensitive resistance (HR) to potato Y potyvirus (PVY) strain groups PVYO in Solanum megistacrolobum and S. polyadenium and PVYN in S. stoloniferum; HR to potato V potyvirus (PW) in S. maglia, S. polyadenium, S. stoloniferum, S. sparsipilum and S. sucrense, HR to potato A potyvirus (PVA) strain group 1 in S. sucrense, and extreme resistance (ER) to PVA in S. polyadenium. S. commersonii and S. stoloniferum expressed HR to tobacco etch potyvirus (TEV) which has not been reported previously in potato species. The studied clone of S. stoloniferum expressed HR to all potyviruses and potyvirus strains tested. The clone of S. stoloniferum (2n = 48; nuclear DNA content (2C) = 3.6 pg) and S. chacoense (2n = 24; 2C=1.9 pg) were crossed and one hybrid (2n = 36; 2C = 2.9 pg) was obtained. The hybrid expressed HR to all tested potyviruses except PVA, which indicated that HR to PVA was controlled by a gene which is different from the genes (or gene) controlling HR to PVYO, PVYN, PVV and TEV in S. stoloniferum. On the other hand, S. chacoense and the hybrid expressed ER to cucumber mosaic cucumovirus (CMV), whereas S. stoloniferum was susceptible to CMV. All tested wild species and the six tested potato cultivars (S. tuberosum subsp. tuberosum) expressed HR to PVV. Expression of HR following infection with PVYN induced systemic acquired resistance (SAR) in S. chacoense. HR to PVYN in S. sparsipilum and S. sucrense and to PVYO in potato cv. Pito was efficiently expressed at lower temperatures (16/18°C) indicated by the development of distinct necrotic lesions and/or vein necrosis in inoculated leaves, whereas the HR was rendered less effective at higher temperatures (19/24°C) which was indicated by the development of systemic infection with leaf‐drop and mosaic symptoms.
Classification as a first step in the interpretation of temporal and spatial variation of crop yield
Authors: LARK R M , STAFFORD J V 
Published: February 2008

Summary.Automated pattern recognition by multivariate clustering is proposed as a tool for interpreting the temporal and spatial variation of crop yield. A trial showed that some general patterns of season‐to‐season variation could be identified and related to soil variability. Such a procedure would be a useful first step in the investigation of sources of yield variation, leading to interpretation and (possibly) spatial variation of inputs.
A morphological study of flower initiation and development in strawberry (Fragaria x ananassa) using cryo‐scanning electron microscopy
Authors: TAYLOR D R , ATKEY P T , WICKENDEN M F , CRISP C M 
Published: February 2008

Summary.The morphological changes in the apex of strawberry (Fragaria x ananassa) cv. Elsanta during flower initiation and early development were studied by means of apical dissections and cryo‐scanning electron microscopy. Characteristic stages of development were recorded from the earliest discernible evidence of floral initiation until anthesis. The results are discussed in relation to previous studies of floral development in strawberry.
Modelling the predicted geographic and economic response of UK cropping systems to climate change scenarios: the case of potatoes
Authors: DAVIES A. , JENKINS T. , PIKE A. , SHAO J. , CARSON I. , POLLOCK C J , PARRY M L 
Published: February 2008

Summary.Geographical changes in suitability in England and Wales for the cultivation of potatoes under a climate change scenario were predicted for the years 2023 and 2065 by integrating a climate database (1951‐80) with climate‐driven crop growth models. Initially, model outputs were produced as point values (meteorological site locations) of predicted potential yields for current crop production. The model outputs were validated statistically using actual crop yield figures collated from bibliographic analysis. The most suitable model was run again incorporating projected temperature and precipitation changes for 2023 and 2065. These outputs were then used to predict possible economic changes to farm profitability and general market trends. Results indicated that, although yields may rise, gross margins for maincrop and especially early potatoes may also rise due to shifts in production, to a fall in overall potato output and to price increases.
Counting by weighing and its effect on seed testing procedures
Authors: RIDOUT M S , SUNTHERALINGAM NALYNI 
Published: February 2008

Summary.Counting by weighing is an approximate procedure for obtaining a given number of items based on an estimate of how much the items will weigh. The procedure can be considerably faster than exact counting. We show how the effects of counting by weighing can be assessed, using a particular problem in seed testing for illustration. We find that using counting by weighing in place of exact counting has little effect on the outcome of the seed test provided that the coefficient of variation of the individual seed weights is not too large, and provided a sufficiently large initial sample is used to estimate mean seed weight.
Neem seed oil inhibits aphid transmission of potato virus Y to pepper*
Authors: LOWERY D T , EASTWELL K C , SMIRLE M J 
Published: February 2008

SummaryTransmission of potato vims Y to sweet pepper by the green peach aphid, Myzus persicae (Sulzer), was inhibited by foliar applications of 1.0% or 2.0% neem seed oil to infected source plants or to uninfected recipient plants. Neem seed oil interfered with virus acquisition and inoculation in a manner comparable to that of a commercial horticultural oil, while an oil‐free neem seed extract did not reduce rates of transmission compared with controls. The finding that neem seed oil inhibits virus transmission, while oil‐free neem seed extract does not, suggests that the presence of the oil rather than biologically active limonoids such as azadirachtin interfere with virus transmission. None of the treatments affected rates of infection when potato virus Y was transmitted mechanically, or the resulting virus titre and symptom expression. In addition to direct control of insect pests, formulated neem oils may help reduce or delay the spread of non‐persistent plant viruses.
Effects of temperature, cultivar and isolate on the incubation period of white leaf spot (Mycosphaerella capsellae) on oilseed rape {Brassica napus)
Authors: INMAN A J , FITT B D L , WELHAM S J , EVANS R L , MURRAY D A 
Published: February 2008

SummaryWhen leaves of oilseed rape (cv. Cobra) were inoculated with conidial suspensions of Mycosphaerella capsellae (white leaf spot) and incubated in controlled environments, the lag period from inoculation to the appearance of the first lesions decreased, and the total number of lesions produced increased, as temperature increased from 5oC to 20oC, although differences between 15oC and 20oC were small. With incubation period estimated as the time from inoculation until 5%, 50% or 95% of the lesions were produced, there was a linear relationship between l/(incubation period in days) and temperature over the range 5oC to 20oC, from which values at intermediate temperatures could be estimated. Summed mean daily temperatures from inoculation to the production of 5% of the lesions were estimated as 115–130 degree‐days in the controlled environment experiments at 5oC to 20oC. When pods or leaves of plants in oilseed rape crops (cv. Cobra or cv. Libravo) were inoculated with conidial suspensions of M. capsellae on five occasions from January to October, with variable temperatures during the incubation period, degree‐days until the first appearance of lesions were in the range 115–230. The numbers of white leaf spot lesions cm‐2 which developed on inoculated leaves differed greatly between nine oilseed rape cultivars, with most on cv. Tapidor and fewest on cv. Libravo, but the incubation period differed little between cultivars. Similarly, the number of lesions which developed differed between four M. capsellae isolates from different regions but the incubation period did not.