bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of different external nitrate concentrations on growth of Phaseolus vulgaris cv. Seafarer at chilling temperatures
Authors: ANDREWS M. , LOVE B. G. , SPRENT J. I.
Published: February 2008

The effects of different applied nitrate concentrations (1 to 50 mol m3) on growth of Phaseolus vulgaris cv. Seafarer at temperatures around 15°C was examined. Total plant dry weight and carbon content decreased sharply with increased applied nitrate 1 to 10 mol m‐3 then decreased slightly with further increases in applied N. Total plant reduced ‐N content increased sharply with increased applied nitrate concentration from 1 to 5 mol m‐3, changed little with increased applied nitrate from 5 to 25 mol m‐3, then increased when applied nitrate was increased from 25 to 50 mol m‐3. Nitrate concentration in all tissues increased sharply with applied nitrate increased from 1 to 10 mol m3 and showed a further increase at 50 mol m3 applied nitrate.

Fresh weight to dry weight ratio for all leaves and specific leaf area for all secondary leaves increased sharply with applied nitrate concentration from 1 to 5 mol m‐3 then decreased with applied nitrate 25 to 50 mol m3 Secondary leaf chlorophyll concentration decreased sharply when applied nitrate increased from 1 to 5 mol m‐3 but increased with applied nitrate from 25 to 50 mol m‐3. Initially, the rate of leaf extension was greater at 20 mol m‐3 applied nitrate than 1 mol m‐3 applied nitrate.

It is proposed that decreased growth with increased applied nitrate in the range 1 to 10 mol m‐3 is due to increased leaf damage caused by a greater rate of leaf expansion.
A procedure for isolating Pyrenochaeta terrestris from onion roots
Authors: AWUAH R. T. , LORBEER J. W.
Published: February 2008

Surface sterilised stelar tissues from onion roots exhibiting typical pink root symptoms were plated on water agar and incubated under cool white fluorescent light (CWFL) for 12 h day‐1 at 20°C. After 4–5 days, the plates were examined with the 10† objective of a compound microscope and tissues producing conidia of Fusarium spp. were discarded. Sub‐cultures of isolates suspected to be Pyrenochaeta terrestris, grown from Fusarium‐negative tissues, were transferred to chloroamphenicol‐amended (500 ppm) corn‐meal (CCMA) agar plates and incubated at 24°C under CWFL for a further 10–14 days. Cultures with setose pycnidia were identified as P. terrestris. Plates were again scanned for conidia of Fusarium spp., and cultures negative for Fusarium spp., but not producing pycnidia, were suspected to be P. terrestris. These were compared with known isolates on CCMA. On this medium growth of P. terrestris was slow, producing appressed, pinkish colonies which were circular with a smooth margin. All isolates of P. terrestris isolated by the procedure caused pink root of onion when tested, whereas none of the Fusarium spp. isolated produced the disease. However, a mixed inoculums of P. terrestris and Fusariurn solani produced typical pink root symptoms.
The overwintering of cereal aphids on Gramineae in southern England, 1977–1980
Authors: HAND S. C.
Published: February 2008

Cereal aphids were sampled monthly on graminaceous host plants on farmland in Hampshire, UK from September 1977 to April 1980. Sitobion avenae overwintered anholocyclically on most types of Gramineae, particularly seedling grass crops and small‐grain cereals. S. fragariae was probably mainly holocyclic on Rubus spp. Large summer populations of Metopolophium dirhodum were probably derived from holocyclic colonies on roses. M. festucae (subsp. cerealium) appeared to overwinter only anholocyclically, and was found mainly on mature grass crops and grasses in hedgerows. Rhopalosiphum padi was the most numerous species in autumn and overwintered anholocyclically in all three winters studied. R. insertum and R. maidis were rare and did not appear to survive the winter anholocyclically on graminaceous hosts.
Validation of models that predict the peak density of grain aphid (Sitobion avenue) and yield loss in winter wheat
Authors: CARTER N. , ENTWISTLE J. C. , DIXON A. F. G. , PAYNE J. M.
Published: February 2008

Aphid counts and yield results from a three‐year field trial of the effectiveness of insecticides applied at various growth stages of winter wheat, were used to test the accuracy of the predictions of the Entwistle and Dixon (1986, 1987) models for forecasting aphid damage and population growth. In general, the peak aphid populations of Sitobion avenae and damage were not accurately predicted but the spray recommendations, which would have resulted from the predictions, would have been correct in each of the three years; one outbreak and two non‐outbreak years. In particular the effectiveness of early spraying was over‐estimated because the persistence of the effect of insecticides was over‐estimated. It is recommended that further work be done on the rate of development of aphid populations following application of insecticides.
Survival of Alternaria brassicae and Alternaria brassicicola on crop debris of oilseed rape and cabbage
Authors: HUMPHERSON‐JONES F. M.
Published: February 2008

Alternaria brassicae and A. brassicicola lesions present on infected leaves of oilseed rape and cabbage placed outdoors on soil produced viable spores for as long as leaf tissues remained intact. For oilseed rape this was up to 8 wk and for cabbage up to 12 wk. On leaves exposed in November and January spore concentrations decreased with time but on leaves exposed between April and June spore concentrations increased up to 9‐fold in the first 4–6 wk and then declined. On stem sections of seed plants of oilseed rape and cabbage similarly placed on the soil, the fungi produced viable spores for up to 23 wk with spore concentrations increasing up to 11‐fold in the first 6–8 wk after harvest. These results indicate that infected debris of brassica crops remaining on the ground after harvest may provide a source of dark leaf spot infection which may be implicated in the spread of the disease within and between crops.
Preparation and evaluation of dehydrated mycological media from West African raw materials
Authors: AWUAH R. T.
Published: February 2008

Twelve culture media powders prepared from local raw materials were evaluated for their mycological utility using Nigrospora oryzae as the initial test organism. Radial growth of N. oryzae was greater (P < 0.05) on media from pigeon pea, soybean and ripe plantain than on Oxoid potato‐dextrose agar (PDA) control. Two other media supported radial growth comparable to potato‐dextrose agar. More conidia were produced on the ripe plantain medium (44/microscope field) than on PDA (3.4/microscope field). In an additional test, Fusarium oxysporum f. sp. cubense, Aspergillus niger, Curvularia lunata and Choanephora cucurbitarum grew and sporulated well on selected media. Local media were inexpensive and easy to produce but tended to be characterised by reduced clarity and presence of particles after autoclaving and jelling.
Changes in relative abundance of two potato cyst nematode species Globodera rostochiensis and G. pallida in one generation
Authors: MARSHALL J. W.
Published: February 2008

Changes in relative abundance of the two potato cyst nematode species Globodera rostochiensis and Globodera pallida were studied during the 1983/84 season at two different population levels in small pots in the glasshouse and at a single population density on plants grown outdoors in 2 litre terylene cloth bags.

In both environments G. rostochiensis was the more successful species. Although the ratio of the two species changed and G. pallida was at a lower level at the end of the experiment it was never eliminated. However, when the number of G. pallida in the mixture was small it did better than expected and demonstrated a frequency dependent response.
The inheritance of floral characters in white clover (Trifolium repens)
Authors: HILL J. , NORRIS I. B. , MICHAELSON‐YEATES T. P. T.
Published: February 2008

A diallel cross was carried out among seven varieties of white clover to investigate the inheritance of some of those characters which affect potential seed yield. Peduncle length and number of seeds/floret have low narrow‐sense heritabilities, while peduncle length displays the added complications of heterozygosity and non‐allelic interactions. Consequently, improvements in these characters will be difficult. Seed number m‐2 is a composite character which apparently exhibits heterozygosity. Higher seed yields will therefore be obtained by selection for its component characters, particularly floret number and floral density, both of which are apparently inherited in a comparatively straightforward manner. These results are discussed in the context of improving the potential seed yield of white clover.
Variability in response of potato cultivars to micropropagation.: In vitro performance
Authors: CALIGARI P. D. S. , POWELL W.
Published: February 2008

The variation in response of 23 cultivars to temperature and sucrose level was investigated for in vitro shoot cultures of potato. It was found that both temperature and sucrose level had a significant effect but in terms of the interactions with cultivars that temperature was the more important. The means and components of variation for the different treatments were examined to reveal the potential for selecting a treatment combination giving optimal expression of the characters measured to assess growth of the micropropagated plantlets. In the case of rapid multiplication systems, a high mean response for number of usable nodes combined with a low cultivar component of variation (i.e. a high response uniformly over cultivars) would be desirable. This combination of character expressions was generally achieved, in the present study, when cultures were raised at 20°C with 3% sucrose in the medium.
Variability in response of potato cultivars to micropropagation
Authors: POWELL W. , BROWN J. , CALIGARI P. D. S.
Published: February 2008

The field performance of 23 cultivars exposed to various tissue culture regimes was evaluated in the presence of appropriate controls. There were significant differences between cultivars but more importantly there were significant interactions between cultivar and treatments. The largest interaction effect was consistently clones x field vs micropropagated seed tubers and was found to be highly significant (P < 0.001) for all variates examined. In general, there was little agreement between the performance of cultivars when grown from explant‐derived seed tubers and when they were grown from field‐produced seed. This study demonstrates the potential problems associated with the phenotypic selection of tissue culture derived material in a potato breeding programme.
Respiratory changes in yam storage tissue (Dioscorea spp.) infested with Meloidogyne incognita using a novel technique for measuring oxygen uptake
Authors: FAWOLE B. , EVANS A. A. F.
Published: February 2008

A simple, novel application is described which measures the oxygen uptake in respiring tissues using an electrochemical gas sensor to monitor volume concentration changes in ambient oxygen with output to a chart recorder. Oxygen uptake by white yam, Dioscorea rotundata cvs Nwopoko and Obioturugo; and yellow yam, D. cayenensis (cv. Ukom Manu) which were heavily infected with root‐knot nematode, was significantly higher than in the non‐infected tissue. However, the rate of oxygen uptake in D. rotundata was significantly higher than in D. cayenensis.
The effects of gibberellin A3 on white clover during floral development
Authors: NORRIS I. B.
Published: February 2008

The effects of gibberellin A3 (GA3) application on the white clover variety Olwen were assessed in the field. Timing of application in relation to developmental stage was also examined.

Gibberellin A3 at a concentration of 100 mg litre‐1 increased the number of reproductive buds per stolon, the peduncle length and the number of seeds per head. Application at flower bud emergence or at the beginning of peduncle extension gave the greatest increase in these characters.

Gibberellin A3 also increased the number of nodes per stolon, stolon length and petiole length.
Effects of seed‐bed conditions on slug numbers and damage to winter wheat in a clay soil
Authors: GLEN D. M. , MILSOM N. F. , WILTSHIRE C. W.
Published: February 2008

In a field experiment three levels of consolidation were combined with three seed‐bed tilths, to produce nine different types of seed‐bed. The soil properties of each combination of tilth and consolidation were measured and effects on the numbers and biomass of slugs in the top 10 cm of soil and on damage to wheat seeds and seedlings were assessed. Eight species of slug were present, with three species predominating (Deroceras reticulatum, Arion distinctus and Arion subfuscus). Between 3% and 33% of seeds and seedlings were killed by slugs (recorded at Growth Stage 12). Contrary to expectation, most damage occurred on consolidated seed‐beds of fine or medium tilth, least on loose seed‐beds of the same texture; intermediate damage occurred on cloddy seed‐beds, where consolidation had little effect. The level of damage occurring on different types of seed‐bed was directly related to the biomass of slugs in the top 10 crn of soil, and was inversely related to depth of sowing and the percentage of fine soil in the seed‐bed. These three factors together accounted for 94–97% of the variance in slug damage. Consolidation was associated with increased slug damage probably because of its effects on these three factors: slug biomass was greater and seed was at shallower depth in consolidated than loose seed‐beds and consolidation, whether before or after drilling, failed to break down clods of soil into finer particles. This is the first experimental evidence in the field of the effects of seedbed conditions on slug numbers and damage to winter wheat and represents a significant step towards forecasting and avoiding slug damage in this crop.
Sampling techniques, spatial distribution and cultural control of millet spike worm, Raghuva albipunctella (Noctuidae: Lepidoptera)
Authors: GAHUKAR R. T.
Published: February 2008

Spike washing and direct count methods were equally effective for sampling eggs and young larvae of millet spike worm, Raghuva albipunctella (Noctuidae: Lepidoptera) in Senegal, but spike washing is a more economical method. Most eggs (70%) were laid on emerging millet spikes and the spike apex was the preferred oviposition site. Most larvae pupated 10–30 cm from millet hills. The maximum number of pupae was found in the upper layer (< 10 cm) in loamy soil and deeper (20–30 cm) in sandy soil. Ploughing fields after millet harvest reduced the population of spike worm pupae significantly, but may prove impracticable or socially unacceptable to farmers.
Effects of the paedogenetic mushroom cecid, Heteropeza pygmaea (Diptera:Cecidomyiidae) on cropping of the cultivated mushroom (Agaricus bisporus)
Authors: WHITE P. F.
Published: February 2008

When introduced into a mushroom crop at rates of 2, 20 or 200 larvae/tray (0.56 m2), the mushroom cecid, Heteropeza pygmaea, caused significant reductions in both yield and number of mushrooms in relation to the infestation level. The reductions were greater when the larvae were introduced at spawning rather than at casing. The yield and number of infested (unmarketable) mushrooms increased significantly in relation to the initial infestation level.

Just two H. pygmaea larvae, introduced at spawning, resulted in cecid populations that caused a 12% loss in total yield in addition to a 7% loss due to spoilage. Loss assessment in the future, therefore, should take into account both yield suppression and spoilage.

There was little effect of cecid infestation on flush timing and mushroom size was only affected in the fourth flush, when a significant reduction (27%) was shown at the highest infestation rate at spawning.
A field study of the relationship between pre‐planting density of Globodera pallida and the growth and yield of two potato cultivars of differing tolerance
Authors: TRUDGILL D. L. , MARSHALL B. , PHILLIPS M.
Published: February 2008

Non‐resistant but tolerant cv. Cara and non‐resistant but relatively intolerant cv. Pentland Dell were grown in split plots encompassing a range of population densities of potato cyst nematode, Globodera pallida. Light interception and its efficiency of conversion were estimated by regular ground cover measurements and plant harvests. It was concluded that increasing levels of infestation with G. pallida only slightly decreased the efficiency of utilisation of intercepted radiation. Heavy infestation of G. pallida initially decreased the top growth and light interception of both cultivars by similar proportions, but in later harvests, this adverse effect markedly decreased for Cara whereas it slightly increased for Pentland Dell. This difference was due to the heavily infested Cara eventually achieving and maintaining 100% ground cover whereas the equivalent Pentland Dell never exceeded 75% ground cover. Consequently, final tuber yields were decreased much more for Pentland Dell than for Cara though the decreases in tuber yield were less than those for top growth. The importance of nematode effects on top growth, and hence on light interception, with regard to both yield losses and tolerance differences, were clearly demonstrated. Both linear and logarithmic models were used to describe the relationship between the initial population density of G. pallida and yield, and the implications of differences in tolerance on the parameters in the logarithmic model are discussed.
Investigation of the relationship between seed leachate conductivity and the germination of Brassica seed
Authors: THORNTON JANET M. , POWELL ALISON A. , MATTHEWS S.
Published: February 2008

Large differences in the leachate conductivities of single seeds after 24 h soaking were observed in five Brussels sprout cultivars. Within each cultivar non‐germinable seeds tended to have higher conductivities than germinable seeds, but the conductivity above which seeds failed to germinate varied between cultivars. No conductivity reading or partition value could therefore be considered as an absolute boundary between germinable and non‐germinable seeds to allow the prediction of seed germination for all seed lots of the same species. However, the mean conductivity for each sample was significantly correlated with germination (r = 0.83, P < 0.05) and was clearly higher for samples with lower germinations. Differences in the partition values for the five cultivars may have been attributable to the natural age of the seeds. Seeds of Asmer Aries artificially aged rapidly at 20% moisture content for up to 48 h at 45° C showed increasing leachate conductivity with increased time of ageing (r = 0.97, P < 0.01) and decreased germination (r = ‐ 0.88, P < 0.05). Again however the values for germinable and non‐germinable seeds of different artificial ages varied. Leakage from seeds was limited by the testa in the first 6 h of imbibition. Solute leakage from embryos of the five cultivars was therefore greater than those for intact seeds but a clear separation of germinable and non‐germinable seeds was still not possible from the conductivity readings. The implications of the observed increases in conductivity with increased seed age and decreased germination for the development of a rapid vigour test for small seeded vegetables in conjunction with controlled deterioration are discussed.
The response of an autumn‐sown determinate faba bean to different plant distributions
Authors: PILBEAM C. J. , HEBBLETHWAITE P. D. , RICKETTS H. E.
Published: February 2008

The response of an autumn‐sown determinate selection, 858, to different plant distribution patterns was examined in field trials during the two seasons 1985/86 and 1986/87 at the University of Nottingham. Plants were sown at two densities (20 and 40 plants per m2) and at three different row widths (11.9, 23.8 and 47.6 cm) in the autumn of each season.

Plant numbers and combined yields were greater in 1986/87 than in 1985/86. Grain yield was unaffected by differences in inter‐row spacing and this was ascribed to the early attainment of complete ground cover even when plants were grown in widely spaced rows. Yield was most strongly correlated with seed numbers per m2.

An examination of yield on a per plant basis suggested that narrow inter‐row spacings were more productive at low plant densities, while yield per plant was greater at higher densities if the crop was grown on wider inter‐row spacings. It was concluded that autumn‐sown determinate forms of faba bean were able to compensate for large changes in plant distribution and consequently yield was unaffected.
Inhibition of degreening in the peel of bananas ripened at tropical temperatures.
Authors: BLACKBOURN H. D. , JEGER M. J. , JOHN P. , THOMPSON A. K.
Published: February 2008

Changes in the plastid ultrastructure as revealed by thin‐section electron‐microscopy, chlorophyll a/b ratio, and the polypeptides of the thylakoid chlorophyll‐protein complexes have been examined during the degreening of bananas (Musa AAA Group, Cavendish Subgroup) and plantains (Musa AAB Group, Plantain Subgroup) ripened at 20°C and 35°C. In bananas, where degreening is inhibited at temperatures above 24°C, ripening at the higher temperature results in a retention of thylakoid membranes, a relatively delayed breakdown in chlorophyll b, and a reduced dismantling of pigment‐protein complexes. By contrast, in plantains, where degreening is complete within 4 days at both 20°C and 35°C, thylakoid membranes and their associated pigment‐protein complexes are lost, and there is a rapid increase in chlorophyll a/b ratios at both ripening temperatures. It is suggested that the retention of thylakoid membranes is an important factor in the failure of Cavendish bananas to degreen when ripened at tropical temperatures, and that the degreening problem may be related to the comparatively high chlorophyll b content of the preclimacteric fruit.
Assessing the risk of primary infection of cereals by barley yellow dwarf virus in autumn in the Rennes basin of France
Authors: GILLET H. , DEDRYVER C. A. , ROBERT Y. , GAMON AGNES , PIERRE J. S.
Published: February 2008

In the Rennes basin, Rhopalosiphum padi is anholocyclic and represents more than 90% of suction trap catches of potential vectors of barley yellow dwarf virus (BYDV) during autumn. From 1983 to 1987 the possibility of predicting the risk of BYDV infection of batches of barley test seedlings (sampling units) exposed each week from September to December near a 12.2 m high suction trap was investigated. Three kinds of variables were checked as possible predictors: weekly mean or maximum temperatures; weekly catches of R. padi (including or excluding males); and percentage of sampling units infested by aphids.

Three contrasting examples were observed: during the first three years (1983–1985), infection was high and its change with time followed temperature, aphid catches and plant infestation changes; in 1986, high numbers of aphids caught and a high proportion of plants infested resulted in only low infection and in 1987, both infestation and infection were very low.

Simple linear regression analysis showed that the more reliable predictors of infection were the proportion of infested plants and to a lesser extent the numbers of trapped aphids. Multiple linear regressions including either of the three groups of ‘predicting’ variables did not result in any improvement in the prediction.

At a practical level, the use of counts of aphid catches would seem a better compromise between accuracy and consistency of prediction and ease of gathering data than that of plant infestation but any significant improvement of the prediction should be sought in an early estimate of the amount of virus available to aphids before they colonise the plants.
Injury to oilseed rape caused by mirid bugs (Lygus) (Heteroptera: Miridae) and its effect on seed production
Authors: BUTTS R. A. , LAMB R. J.
Published: February 2008

Injury by Lygus spp. to oilseed rape, Brassica napus L. and Brassica campestris L., was assessed based on laboratory and field studies in Alberta, Canada. The visible injuries consisted of lesions on the surfaces of stems, buds, flowers and pods similar to those described for other crops. They caused buds and flowers to abscise and seeds to collapse, and reduced the weight of healthy seeds produced per pod. The plants compensated for bud loss so that no net reduction in the number of pods occurred. However, in some situations the damage to buds resulted in a reduced seed yield that increased with the amount of injury. The plants also compensated for flower loss so that no net reduction in the number of pods occurred, but seed yield declined as injury increased. Plants did not compensate for seeds that collapsed as a result of lygus feeding. The feeding activity of lygus bugs reduced seed yield in oilseed rape.
Epidemiology of Cladosporium allii and Cladosporium allii‐cepae, leaf blotch pathogens of leek and onion.
Authors: JORDAN MARY M. , BURCHILL R. T. , MAUDE R. B.
Published: February 2008

Conidia of Cladosporium allii and C. allii‐cepae germinated over the temperature range 2–30°C on agar with optimal responses at 15–20°C (C. allii) and 20°C (C. allii‐cepae). Conidia of both fungi germinated in water and at c. 100% relative humidity (r.h.) but not at lower humidities on leaf and glass slide surfaces. Germination was more rapid when spores were applied dry to agar or leaves than when applied in water or nutrient solution. More lesions developed when conidia of C. allii‐cepae were deposited dry on onion leaf discs or leaf surfaces than when they were applied suspended in water. Conidia of both fungi required 18–20 h at c. 100% r.h. to germinate and infect when applied dry to leaves. Damaging the leaves or the addition of nutrients to the leaf surface increased the incidence of infection by C. allii‐cepae compared to controls. Inoculated onion bait plants placed out‐of‐doors developed infection after at least 17 h at c. 100% r.h. or with leaf wetness. Similar conditions were necessary for infection of bait plants exposed in onion and leek crops infected by C. allii‐cepae and C. allii respectively. Disease development and spread of infection occurred at different rates over the same period in two different cultivars of leeks, with spore concentrations increasing in proportion to disease. Spore numbers in the air fell considerably when infected leeks were ploughed under.
Plant parasitic nematodes associated with the roots of wind toppled trees at the Royal Botanic Gardens, Kew
Authors: HOOPER D. J. , WEBB R. M. , FLYNN CORINNA
Published: February 2008

Root and soil samples from 21 trees blown down in Kew Gardens during the gales of October 1987 yielded 29 species of plant parasitic nematodes. Pratylenchus crenatus, P. thornei and P. penetrans were the only endoparasitic nematodes found. The common occurrence of P. crenatus and the root ectoparasitic nematodes, such as Merlinius microdorus, Paratrichodorus pachydermus and Rotylenchus robustus reflected the predominantly sandy nature of most of the soil samples. Species rarely recorded in Britain included Hemicriconemoides pseudobrachyurum, Paralongidorus maximus and Xiphinema pseudocoxi, all of which may be introductions.
Strategies for control of eyespot (Pseudocercosporella herpotrichoides) in UK winter wheat and winter barley
Authors: FITT B. D. L. , GOULDS A. , HOLLINS T. W. , JONES D. R.
Published: February 2008

This review considers strategies for control of eyespot (Pseudocercosporella herpotrichoides) in winter wheat and winter barley in the UK. Varietal resistance to eyespot may take the form of direct resistance to the growth of the pathogen in the stem base or of indirect tolerance to eyespot through resistance to lodging. The French variety Cappelle‐Desprez has been a source of resistance for most UK wheat varieties and a new source of resistance in wild goat grass has been discovered recently. Use of fungicides for control of eyespot increased rapidly after the introduction of the highly effective MBC fungicides in the 1970s, but has decreased recently because UK populations of P. herpotrichoides are now predominantly resistant to MBC fungicides and alternative fungicides are more expensive. Historically, cultural methods, especially crop rotation, have been important in the control of eyespot. The importance of cultural control of eyespot is now increasing because more non‐cereal break crops are being grown and fungicide use is declining.
Inheritance of resistance to groundnut rosette virus in groundnut (Arachis hypogaea L.)
Authors: NIGAM S. N. , BOCK K. R.
Published: February 2008

A method of field screening groundnut seedlings for resistance to groundnut rosette virus (GRV), by means of which over 97% incidence was induced in rows of susceptible test plants, was developed at Chitedze Research Station in Malawi. Two GRV‐resistant Virginia cultivars (RG 1 and RMP 40) were crossed with three susceptible cultivars, one from each of the Spanish (JL 24), Valencia (ICGM 48) and Virginia (Mani Pintar) botanical groups. Twelve F1 reciprocal crosses and their F2 and backcross generations were produced and the material screened in nurseries in 1985/86 and 1986/87. Seedlings raised from plants which did not become infected in the field were inoculated in the glasshouse in order to eliminate susceptible escapees.

The numbers of diseased and healthy individuals in each population were subjected to χ2 tests. In the majority of the F2 populations a good fit was obtained for a ratio of one resistant to 15 susceptible plants, a ratio to be expected if resistance to GRV were determined by a pair of independent complementary recessive genes. This was further supported by data from backcross generations.
The use of the polymerase chain reaction (PCR) for the detection of bean yellow mosaic virus in gladiolus
Authors: VUNSH RON , ROSNER ARIE , STEIN ADINA
Published: February 2008

A method is described for the improved detection of bean yellow mosaic virus (BYMV) in gladioli leaves. Specific sequences of BYMV RNA, present in total RNA extracts of infected plants were detected following amplification by the polymerase chain reaction (PCR). The viral RNA was initially reverse‐transcribed into cDNA, then specific sequences were amplified by PCR using specific oligonucleotides as primers. Detectable amounts of virus RNA in BYMV‐infected plant tissue by PCR were approximately three to four orders of magnitude lower as compared with those detectable by ELISA and molecular hybridisation. Combining PCR with molecular hybridisation (using a 32P‐labelled transcript of viral sequences as a probe), further increased the sensitivity of this method to a gain of four to five orders of magnitude as compared with direct molecular hybridisation, and enabled the detection of up to single picogram quantities of the virus.
Further properties of wineberry latent virus and evidence for its possible involvement in calico disease
Authors: JONES A. T. , MITCHELL M. J. , McGAVIN W. J. , ROBERTS I. M.
Published: February 2008

The flexuous filamentous particles of wineberry latent virus (WLV) were found to measure 620. 12 nm and not 510. 12 nm as previously reported. Analysis of dsRNA from infected plants detected a major species of c. 5.7. 106 mol. wt and minor species of lower mol. wt. Purified virus particles formed a major and a minor buoyant density component in solutions of caesium salts with densities of 1.26 and 1.25 g cm‐3 in Cs2SO4 and 1.30 and 1.29 g cm‐3 in CsCl. The particles contained a single nucleic acid species, presumably single stranded RNA, and a single polypeptide of estimated mol. wt 2.78. 106 and 31 000 respectively. In indirect ELISA, purified particles of WLV and particles in plant sap failed to react specifically with antiserum to nine carlaviruses, 12 potexviruses, three capilloviruses or apple chlorotic leafspot closterovirus, nor was WLV found to react with several of these antisera in immunosorbent electron microscopy or immunoblots. In Marion and Olallie blackberry, WLV in mixture with raspberry bushy dwarf virus (RBDV), but not RBDV alone, induced veinal line‐pattern symptoms resembling those of calico disease reported from the USA.
Field trials using single potato plants as whole plots, with and without nematicide treatment, to assess tolerance of attack by Globodera rostochiensis
Authors: EVANS K. , RUSSELL M. D.
Published: February 2008

It is important to assess the tolerance of new potato cultivars with partial resistance to potato cyst nematode attack. The experiments described here are intended to quantify tolerance adequately using a minimum of resources. When test plants were spaced widely in the field trials it was also possible to estimate their resistance levels but standard plant spacing allowed roots of neighbouring plants to encroach on a test plant's root space and to interfere with attempts to assay resistance. Standard plant spacing did, however, give more realistic yields per plant and competition from neighbouring plants was standardised by surrounding each test plant by four identical guard plants (cv. Désirée). Regressions of yield on severity of nematode attack were drawn when nematode infestation varied naturally across the trial site or when different levels of attack were created by applying nematicide at a range of dose rates. Cara was the most tolerant cultivar tested, with a complete spectrum of tolerance shown by other cultivars/clones. Some clones with a high degree of resistance were intolerant and it is precisely these that this type of test seeks to identify.
Effect of seed depth on slug damage to winter wheat
Authors: GLEN D. M. , MILSOM N. F. , WILTSHIRE C. W.
Published: February 2008

In a field experiment drilled at two depths on three dates in autumn 1988, with or without methiocarb pellets broadcast on the soil surface immediately after drilling, 26% of seeds of winter wheat sown at c. 20 mm depth were killed by slugs compared with only 9% of seeds sown at c. 40 mm. The protection from slug damage provided by this additional 20 mm of depth was comparable with that provided by methiocarb pellets. The effects of seed depth and pellet application did not interact and were consistent on all drilling dates. Thus, fewest seeds and seedlings were killed where methiocarb pellets were broadcast on a seed‐bed with seeds sown at 40 mm depth. Intermediate damage was recorded where seeds were sown at 40 mm depth without pellets, or where pellets were broadcast on seeds sown at 20 mm depth. Most seeds and seedlings were killed where seeds were sown at 20 mm depth without pellets. Sublethal damage to seedlings was not affected by sowing depth but was reduced where pellets were broadcast immediately after sowing.
Observations on the distribution of leather jackets in Northern Ireland
Authors: BLACKSHAW R. P.
Published: February 2008

A map of the geographic distribution of leather jackets across five counties of Northern Ireland was produced from annual survey data. Climatic data were used to develop a multiple regression model explaining variation in the mean annual survey population for the years 1970–1984. Predicted populations for 1985–1988 compared favourably with observed counts. Both negative binomial and Adès distributions were successfully fitted to the frequency distribution of leatherjacket field populations from 1969–1986. It is concluded that the distribution of populations in the Province is not random and factors influencing mean leatherjacket numbers differ from those reported for other regions. The multiple regression model is proposed as a substitute for an annual survey of leatherjacket populations in Northern Ireland and it is suggested that the Adès family of distributions may enable it to be extended to predict leatherjacket frequency distributions each year.
A comparison of vector population indices for forecasting barley yellow dwarf virus in autumn sown cereal crops
Authors: KENDALL D. A. , CHINN N. E.
Published: February 2008

Two approaches based on the concept of a vector population index are considered as possible deterministic elements for an empirical forecast of barley yellow dwarf virus (BYDV) in autumn sown cereals. The first, an aerial vector index, is a further elaboration of the infectivity index proposed by Plumb, Lennon & Gutteridge (1981), which assumes that virus damage is a function of the number of infective migrant alatae of the two main aphid vectors, Rhopalosiphum padi L. and Sitobion avenae F., integrated over time from crop planting or emergence. The new formulation, however, excludes holocyclic alate morphs (i.e. males and gynoparae) of the former species, which, although generally abundant in autumn, are nevertheless perceived as relatively unimportant virus vectors since they colonise only the alternative woody host, Prunus padus (the bird‐cherry tree). The second approach, a crop vector index, is a more fundamental departure which argues that field populations of viruliferous aphids, both alatae and apterae, which have already colonised cereals, may be a better criterion of potential virus spread than the density of aerial migrant vectors. This index retains a similar integral form, but evaluates crop exposure to BYDV as accumulated infectious aphid‐days. A method is described whereby this function can be derived from irregular or infrequent aphid samples in the crop. Both methods, unlike Plumb's (1976) original concept, produced indices which were significantly related to subsequent virus infection and yield loss in winter barley at Long Ashton (S.W. England, UK), 1978–1986. The best models were obtained with the crop vector index, fitted to observed virus infection by generalised linear regression using a complementary log‐log link function, or to observed yield loss by simple linear regression using a log transformation of yield (r = 0.84 in each case; compared with r‐values > 0.65 for the aerial vector index, and > 0.35 for Plumb's (1976) index). However, the residual errors and hence confidence limits of these fitted regressions were too large for predicting damage that was significantly less than a reasonable economic damage threshold for BYDV control.

Analyses of the separate components of each index showed a good general relationship between aphid infectivity and the severity of crop infection, confirming the epidemiological importance of this factor. The functional expressions of aphid density, however, were not significant. This evident weakness in the models, and alternative approaches to BYDV forecasting are discussed.
Pre‐harvest retting of flax with glyphosate: effects of novel methods of spray application on penetration of the canopy and uniformity of deposition
Authors: HARVEY B. M. R. , WATSON S. , BAILIE J. E. , SAUNDERS A. , McMORDIE I.
Published: February 2008

Four methods of spray application were compared in 1986 with the recommended method of glyphosate application for pre‐harvest retting of flax (Linum usitatissimum). Sampling individual plants immediately after application of glyphosate and dye demonstrated that spray penetration through the crop canopy, measured as dye deposition on the lower stem as a percentage of total deposition per plant, was the same for all methods of application. None of the methods of application improved the uniformity of dye deposition.

The following year, effects of deseeding prior to spraying and of using an air‐assisted sprayer were investigated. Deseeding increased dye deposition on the lower stem but did not improve the efficacy of glyphosate. Application with an air‐assisted sprayer increased the proportion of spray deposited on the lower stem but not the absolute amount deposited or the efficacy of glyphosate. Dye deposition on individual plants varied greatly for all methods of application and, when glyphosate was applied using the same methods, undesiccated plants occurred in all plots.

Considerable improvements in spray penetration and uniformity of spray deposition appear necessary for successful pre‐harvest retting of flax with glyphosate.
The influence of climatic conditions around the time of spraying isoproturon on the subsequent injury to barley
Authors: BLAIR A. M. , MARTIN T. D.
Published: February 2008

Winter barley cv. Igri was grown in pots, either outside under cover, in a glasshouse or under controlled conditions and treated post‐emergence with isoproturon. There was a linear relationship between the subsequent weight of plants treated with 2.5 kg a.i./ha and either evaporation from a water surface between 2–7 days post spraying or cumulative temperature between sowing and spraying. The relationship between subsequent weight of plants treated to the foliage only with 5 kg a.i./ha and cumulative temperature between sowing and spraying varied between years 1984–86. The post spraying environment had the major influence on subsequent activity of isoproturon at 2.5 kg a.i./ha applied overall to barley under controlled conditions. There was a greater reduction in CO2 exchange in plants grown after treatment under high compared to low relative humidity. When isoproturon at 5 kg a.i./ha was applied to barley plants with wet foliage, plants were slower to recover their initial rate of photosynthesis when kept wet for 24 h as compared with 11 h or when allowed to dry after treatment. Photosynthesis was decreased to a lesser extent under the same post spray conditions by 2.5 than by 5 kg a.i./ha and reduction was greater and recovery of photosynthesis slower in plants grown inside compared to outside.
Physiological responses of mangoes cv. Kensington Pride to gamma irradiation treatment as affected by fruit maturity and ripeness
Authors: BOAG T. S. , JOHNSON G. I. , IZARD M. , MURRAY C. , FITZSIMMONS K. C.
Published: February 2008

An investigation was undertaken to examine responses of mangoes cv. Kensington Pride to irradiation treatment.

Gamma irradiation of preclimacteric fruit increased fruit respiration immediately after treatment, delayed the time to attain the climacteric respiratory peak and reduced the magnitude of this peak rate. Fruit softening was unaffected whereas skin colour development was strongly inhibited by irradiation treatment. Inhibition of skin degreening was half‐maximal at a dose of 200 Gy. Exposure to ethylene failed to reverse this inhibition. Less mature fruit were more strongly affected by irradiation treatment. Fruit which were partially ripe and in their climacteric rise at time of treatment were largely unaffected by irradiation. These results are discussed in terms of the utility of irradiation technology for commercial disinfestation.
Components of resistance to the sorghum midge, Contarinia sorghicola
Authors: SHARMA H. C. , VIDYASAGAR P. , LEUSCHNER K.
Published: February 2008

Studies were conducted on components of resistance to sorghum midge on four resistant (DJ 6514, AF 28, TAM 2566 and IS 15107) and two susceptible cultivars (CSH 1 and Swarna). Data were recorded on the numbers of eggs, larvae, emerged adults and grain damage in panicles of different genotypes infested with 60 midge females/panicle under no‐choice conditions. The size of floral parts (glume, lemma, palea, lodicule, stigma, style, ovary and anther), rate of grain development and tannin content of grain were measured. The lengths of glume gl and 82, lemma L1 and L2, palea, lodicule, anther, style and stigma were positively associated with susceptibility to sorghum midge. Rate of grain development (between 3rd and 7th day after anthesis) was negatively associated with susceptibility to sorghum. Tannin content of grain was also negatively correlated with midge susceptibility, although there were distinct exceptions (e.g. DJ 6514 is highly resistant bur has a low tannin content).
Development of a technique to study seedling emergence in response to moisture deficit in the field —The seed bed environment*
Authors: SOMAN P.
Published: February 2008

The ability of crops of sorghum (Sorghum bicolor (L.) Moench) to establish in farmers' fields depends largely on its capacity to germinate and emerge under limited soil moisture conditions. Studies on germination under moisture stress have been previously conducted using osmotic media which do not wholly reproduce the conditions of the seed bed in the field. Hence the need for a field screening technique. A line source irrigation system was used to provide five moisture regimes ranging from ‐0.08 MPa to ‐0.92 MPa. The drying rate of the soil and the soil temperature depended largely on incident radiation, and the relationship between the moisture content and daily soil temperature and daily radiation was consistant. Total porosity of the seed bed, derived from bulk density measurements and particle density ranged from 43.8% to 45.3%, which would allow sufficient aeration when as in the experiments conducted here, water content was low (> 0.14 g/g). Under these seed bed conditions the pattern of response of emergence to the moisture gradient was linear or curvilinear. Genotypic differences existed for emergence and its response to water level. The field method developed is useful for identifying genotypes able to germinate and emerge under conditions of low seed bed moisture.
The influence of seed quality and pregermination treatment on cauliflower and cabbage transplant production and field growth
Authors: FINCH‐SAVAGE W. E. , McKEE J. M. T.
Published: February 2008

Seedling emergence and subsequent growth from untreated seeds and selected‐germinated seeds which had been dried before sowing (low‐moisture‐content germinated (LMCG) seeds) were compared in cellular trays in a glasshouse and in the field following transplanting. Three seed lots of different quality of the same cultivar were used for cabbage and cauliflower. In all cases, seedling emergence was greater, earlier and more uniform from LMCG seed than that from untreated seeds. LMCG seed effectively eliminated the differences due to seed quality shown by untreated seeds at emergence suggesting an improvement in seed vigour as well as viability from the selection treatment. Higher quality seed and LMCG cauliflower seed led to larger curd weights and therefore an increase in marketable yield at harvest compared to that from lower quality seeds. However, differences in transplant uniformity due to seed quality and seed treatment had little impact of agronomic significance following transplanting.
Monitoring populations of the carrot fly, Psila rosae, with sticky and water traps
Authors: COLLIER ROSEMARY H. , FINCH S. , EMMETT B.J. , BLOOD‐SMYTH JENNIE
Published: February 2008

The relative, effectiveness of Rebell®, small cylinder, large cylinder, windmill and water traps, the five types of trap used currently for monitoring populations of the carrot fly, Psila rosae, was assessed in nine field experiments, three in south west Lancashire, four in the Fens (Suffolk, Norfolk, Cambridgeshire), one in East Suffolk and one at Wellesbourne, Warwickshire. Regression analysis of the numbers of flies caught on each type of trap against the numbers caught on the Rebell® trap indicated that each trap samples a constant proportion of the fly population relative to the other traps. Therefore, provided the fly population was sufficiently large for insects to be caught on the least effective traps, any of the five traps would monitor adequately fluctuations in carrot fly populations. However, the Rebell® trap caught 4–17 times as many flies/trap and 5–7 times as many flieshnit area of trap as any of the other traps tested.

Operators considered the Rebell® trap to be the easiest to use. However, it was more expensive than any of the other traps tested.