bluuebunny/crossref_metadata_2025 huggingface dataset:
Overwintering of Venturia inaequalis, the causal agent of apple scab, on different cultivars
Authors: JEGER M. J. , SWAIT A. A. J. , BUTT D. J.
Published: February 2008

A maturation index summarising pseudothecial development of Venturia inaequalis was devised. The index demonstrated differences in overwintering on 10 apple cultivars and the crab apple Malus toringo in experiments over two winters. At about the green cluster stage, when there is a high proportion of susceptible foliage, there were 50–100 fold differences in the yield of ascospores from these hosts, due mainly to different rates of pseudothecial maturation. These rates were shown to be independent of cultivar differences in colony numbers on leaves in the previous autumn.

Cultivar differences in the timing of fruit bud development were independent of differences in the overwintering of V. inaequalis. These findings confirm the importance of considering cultivar identity in apple scab management.
Tolerance in Botrytis squamosa to iprodione
Authors: PRESLY A. H. , MAUDE R. B.
Published: February 2008

Cultures of B. squamosa when grown in concentrations from 4–2500 μg/ml of iprodione in agar, produced iprodione‐insensitive isolates distributed at random over the concentration range. Thirty of the 37 isolates when subsequently transferred to fungicide‐free agar were slower growing than the parent cultures. Similar results were obtained with single spore and multispore isolates. Iprodione insensitivity occurred in cultures derived from benomyl tolerant and sensitive field isolates. Insensitive isolates grown on agar, containing 500 μg/ml iprodione, did not revert to sensitivity after several cultural cycles on fungicide‐free agar. Spores of iprodione insensitive isolates generally proved less infective than spores from sensitives isolates when sprayed onto untreated onion leaves. In general, protectant sprays of iprodione did not enhance the infectivity of insensitive isolates. Inoculation of glasshouse and field raised plants indicated that although selected aggressive iprodione‐insensitive isolates, from treatments with low and high concentrations of the fungicide, readily infected onion leaves, they were less capable of sporulation than the sensitive parent forms of the fungus.

Iprodione‐insensitive isolates were cross‐tolerant to the chloronitrobenzene fungicides quintozene and tecnazene and to the dichloroaniline fungicide dicloran.
The effect of prunus necrotic ringspot virus on field‐grown roses
Authors: THOMAS B. J.
Published: February 2008

The effect of prunus necrotic ringspot virus (PNRSV; cherry serotype) on field‐grown maiden rose bushes cv. Fragrant Cloud was assessed in two trials during 1979 and 1980. PNRSV delayed the onset of flowering, reduced the size and number of blooms and increased the proportion of deformed flowers but had no effect on flower pigmentation or scent. Autumnal leaf‐fall was generally earlier in diseased bushes, which lacked vigour and re‐established less readily after transplanting. Although all healthy plants conformed to the British Standards Institution specifications for maiden bush roses, c. half of diseased plants were sub‐standard because the total diameter of the shoots produced at the bud union was less than 20 mm.

The significance of these results is discussed in relation to the commercial production of field‐grown rose bushes in the UK.
The development and yield of autumn‐ and spring‐sown barley in south east Scotland
Authors: RUSSELL G. , ELLIS R. P. , BROWN J. , MILBOURN G. M. , HAYTER A. M.
Published: February 2008

As part of a study of the relationship between plant development and grain yield, winter and spring barleys were sown in the autumn and spring. Apical development and leaf area development were monitored and the final yield was partitioned into grain weight and grain number. The photosynthetically active radiation (PAR) absorbed was calculated.

The main differences found were between sowings rather than between genotypes within sowings. The autumn sowing outyielded the spring sowing because the grains were heavier, although the autumn sowing tended to have fewer grains m‐2. In the autumn sowing the rate of initiation of spikelet primordia was slower, due to the lower temperatures encountered, but the initiation phase lasted longer and a larger proportion of primordia survived. However, the increased proportions of tillers to mainstem reduced the mean number of grains/ear.

The numbers of grains m‐2 and the yield were related to the PAR absorbed. In this analysis the earlier anthesis of the autumn‐sown plants could be seen to be reducing the PAR absorbed and consequently the grains m‐2.
Effect of osmotic potential on the growth of Gaeumannomyces graminis and Phialophora spp.
Authors: WONG P. T. W.
Published: February 2008

The linear growth of 10 isolates each of Gaeumannomyces graminis var. graminis, G. graminis var. tritici and Phialophora graminicola and five isolates each of G. graminis var. avenae and a lobed‐hyphopodiate Phialophora sp. was studied on osmotically adjusted agar at 20 °C. While most isolates of G. graminis var. avenae ceased growing at osmotic potentials of ‐60 bars (1 bar = 105 Pa), six out of 10 isolates of G. graminis var. tritici grew at that potential. The growth of all isolates of G. graminis var. tritici and var. avenae ceased at ‐70 bars. In contrast, four out of 10 isolates of P. graminicola grew at ‐70 bars, but all stopped growing at ‐80 bars. Most of the isolates of G. graminis var. graminis and the lobed‐hyphopodiate Phialophora sp. grew at ‐70 bars while three out of 10 isolates of G. graminis var. graminis and one out of five isolates of the lobed‐hyphopodiate Phialophora sp. were capable of growth at ‐80 bars. None of the fungi grew at ‐90 bars.

Detailed studies of the growth of two or three isolates each of the five fungi at 10, 20, 30 and 35 °C were carried out on osmotic agar controlled by the addition of either sodium chloride or potassium chloride. In general, similar reductions in growth occurred with decreasing osmotic potential regardless of the solute used. At 10 and 20 °C., all three isolates of P. graminicola showed optimal growth at about ‐5 bars while the other fungi grew fastest at ‐12middot; bars. At 30 °C., one isolate of the lobed hyphopodiate Phialophora sp. and two isolates each of P. graminicola, G. graminis var. tritici and G. graminis var. avenae grew optimally at osmotic potentials of ‐10 to ‐15 bars. The other isolate of the Phialophora sp. and two isolates of G. graminis var. graminis studied grew optimally at the highest potential (‐1·2 bars). However, at 35 °C the last three fungi exhibited optimal growth at osmotic potentials of‐10 to ‐20 bars. The ecological significance of these results is discussed in relation to cross‐protection against the take‐all fungi by the avirulent fungi.
The response of tomato seedling roots to infection by Verticillium albo‐atrum or Fusarium oxysporum f. sp. lycopersici
Authors: HUTSON R. A. , SMITH I. M.
Published: February 2008

The response of seedling roots of near‐isogenic tomato varieties to infection by Verticillium albo‐atrum or Fusarium oxysporum f. sp. lycopersici was investigated. Studies of the infection of seedling roots not artificially damaged indicated that there was an extra‐vascular expression of resistance towards V. albo‐atrum but not to F. oxysporum. Roots of resistant tomato seedlings infected by V. albo‐atrum contained the fungus in the epidermis and outer cortex while susceptible roots became heavily colonised. Observations made by transmission electron microscopy showed that the fungus appeared to be abnormal in growth and appearance in the epidermal and cortical cells of resistant seedling roots but normal in susceptible roots. Two preformed antifungal terpenoids were detected in seedling roots in greater amounts in resistant that in susceptible varieties. The possible mechanisms of seedling root resistance to vascular wilts are discussed.
Susceptibility of tobacco blue mould (Peronospora hyoscyami) to metalaxyl
Authors: JOHNSON G. I. , SHEPHERD R. K.
Published: February 2008

The lethal dose (LC50) of metalaxyl for a wild isolate of Peronospora hyoscyami f. sp. tabacina was determined using a bioassay. Infection levels were recorded using 5‐wk‐old tobacco seedlings that had been treated with foliar sprays of metalaxyl (Ridomil®) 24 h prior to inoculation. Plants were maintained in a controlled environment cabinet. LC50 estimates determined by probit analysis of the data from three independent experiments ranged between 0–46 and 0–58 μg/ml. Pooling the results for all three experiments, probit analysis gave a slope of 8·733 (S.E. 0·805) with an LC50 of 0·51 μg/ml (95% fiducial limits 0·45, 0·57). This determination will be useful as a guide to future monitoring of P. hyoscyami for resistance to metalaxyl.
Further studies on a spiroplasma isolated from coconut palms in Jamaica
Authors: EDEN‐GREEN S. J. , ARCHER D. B. , TULLY J. G. , WATERS HENRY
Published: February 2008

The pathogenicity of a spiroplasma isolated from coconut palms was tested by (1) transmission experiments to palms and other plants susceptible to infection by mycoplasmas, using the suspected vector of lethal yellowing, Myndus crudus, and vectors of the agents of other yellows diseases and (2) enzyme‐linked immunosorbent assay (ELISA) to detect spiroplasma antigens in diseased palm tissues. Results of both these tests were negative and, as earlier attempts to repeat the isolations from lethal yellowing diseased palms had also been unsucessful, it was concluded that this organism was not the causal agent of lethal yellowing disease. Further analysis by serological tests and by polyacrylamide gel electrophoresis (PAGE) of spiroplasma proteins confirmed that the coconut isolates were related to members of the Spiroplasma citri serogroup but were distinct from other strains tested.
Influence of the soil conditioner cellulose xanthate on the activity and persistence of nine acetanilide herbicides
Authors: WALKER A. , ROBERTS H. A. , BROWN P. A. , BOND W.
Published: February 2008

Applications of cellulose xanthate equivalent to 25 kg cellulose/ha increased the numbers of weed seedlings by up to 23% compared with untreated controls. With propachlor and prynachlor, weed control was poorer in the presence of cellulose xanthate and analyses of soil samples demonstrated that the rate of herbicide loss from the soil was enhanced. Although the soil conditioner increased the rate of loss of some other acetanilide herbicides, weed control was not greatly affected. The results suggest that interactions between cellulose xanthate and acetanilide herbicides are only important with those compounds which are normally of very short persistence.
An analysis of the seasonal variation in the dry seed yields of eleven cultivars of Phaseolus vulgaris
Authors: ANDREWS D. J. , HARDWICK R. C. , HARDAKER J. M.
Published: February 2008

Nine determinate and two indeterminate‐bush dry seed cultivars of P. vulgaris were grown in trials for four successive years. Mean annual yield of air dry seed (15% moisture content) varied between 222 and 398 g/m2. Most of the annual variation in yield was accounted for by differences in the quantity of nitrogen fertiliser applied and in the duration of bright sunshine during August. The annual mean harvest date varied between 20 September and 9 October. There was a significant negative correlation between the mean harvest date and the number of Ontario heat units accumulated between 20 May and 20 July.

There were significant interactions between genotype and environment for both yield and harvest date; joint regression analysis of the interactions showed that five of the cultivars, which had previously been identified as cold tolerant in laboratory tests, all showed greater stability of yield and of maturity date than standard navy bean types. Environmental variation in the yield components of the cold tolerant selections tended to be compensatory, while that of the standard navy beans was additive in its effects on yield.
Effects of adding plant nutrients to the gel carrier used for fluid drilling germinating lettuce and onion seeds
Authors: FINCH‐SAVAGE W. E. , COX C. J.
Published: February 2008

Fluid drilled germinating lettuce seeds gave earlier production of larger heads than dry sown natural seeds. The addition of sodium phosphate to the gel with germinating seeds increased seedling growth rate which further advanced maturity and increased head weight. Sodium, ammonium and potassium phosphate added to the gel increased seedling dry weight of onions compared to the germinating seed control which produced larger seedlings than dry seed. However, these early improvements in onion seedling size diminished with time.
Fusarium oxysporum f. sp. fatshederae, a new forma specialis causing wilt of x Fatskedera lizei
Authors: TRIOLO E. , LORENZINI G.
Published: February 2008

A Fusarium oxysporum sensu Snyder & Hansen was pathogenic in the vascular tissue and caused a severe wilt and dieback of ×Fatshedera lizei, Fatsia japonica and Hedera helix.

The fungus appeared nonpathogenic on plants of 29 species in numerous genera.

Benomyl soil drenches were effective in preventing infection.

A new forma specialis, Fusarium oxysporum f. sp. fatshederae, f. sp. nov. is proposed for this pathogen.
Serological detection of ryegrass mosaic virus and ryegrass seed‐borne virus
Authors: CHESTER IRENE B. , HILL S. A. , WRIGHT DAPHNE M.
Published: February 2008

Ryegrass mosaic virus (RMV) was reliably detected in both perennial (S24) and Italian (S22) ryegrass, by enzyme‐linked immunosorbent assay (ELISA) when plants had been infected for 8 wk. ELISA detected more infections in field‐grown perennial ryegrass cv. Premo than either visual assessment or electron microscopy. However, with plants of Italian ryegrass cultivars only recently infected with RMV, positive reactions were more difficult to separate from the reactions of RMV‐free plants, which varied considerably with cultivar, some giving high absorbance values. Immunosorbent electron microscopy showed that the RMV antiserum also contained antibodies to ryegrass seed‐borne virus (RGSV), suggesting that these high values were caused by RGSV infection in the material tested.
Comparison of nucleic acid hybridisation and other tests for detecting tobacco rattle virus in narcissus plants and potato tubers
Authors: HARRISON B. D. , ROBINSON D. J. , MOWAT W. P. , DUNCAN G. H.
Published: February 2008

All isolates of tobacco rattle virus (TRV) found in naturally infected narcissus leaves produced nucleoprotein particles, mostly in large concentrations but, because of antigenic diversity, less than half of the isolates were identified by immunosorbent electron microscopy (ISEM) and still fewer by enzyme‐linked immunosorbent assay. All were identified by a nucleic acid hybridisation test in which DNA complementary to RNA‐1 of strain PRN of TRV was allowed to react with nucleic acid extracted from leaf tissue.

Spraing‐affected tubers in some potato stocks yielded only NM isolates of TRV. These isolates do not produce virus particles and they were therefore not detected by ISEM. The infectivity of nucleic acid extracts from recently harvested tubers with spraing symptoms was much greater than that of extracts prepared from tubers after 8 months' storage. In other potato stocks, some spraing‐affected tubers contained NM isolates and the rest contained particle‐producing isolates (M isolates) of TRV. The infectivity of sap and of nucleic acid, extracted 7 months after harvest from tubers infected with M isolates, was much greater than that of nucleic acid extracted from comparable tubers infected with NM isolates. TRV was detected by nucleic acid hybridisation in extracts of almost all tubers containing either M or NM isolates, even when the tubers were not tested until 7–8 months after harvest. The probable sequence of events occurring after tubers are infected with TRV is outlined, and it is suggested that the virus will rarely become established in fields as a result of planting infected tubers.
Inheritance and sources of resistance to bacterial speck of tomato caused by Pseudomonas syringae pv. tomato
Authors: FALLIK E. , BASHAN Y. , OKON Y. , CAHANER A. , KEDAR N.
Published: February 2008

Inheritance of resistance to bacterial speck of tomato was determined by analysing F1 F2 and backcross progenies of crosses involving a susceptible (VF‐198) and a resistant cultivar (Rehovot‐13). The results fit the hypothesis that resistance is controlled by a single dominant gene in interaction with minor genes. Cultivar susceptibility to Pseudomonas syringae pv. tomato was tested under greenhouse conditions under high inoculum pressure using infested tomato seeds together with infested soils and spray‐inoculated wounded plants. Of 21 species, cultivars and lines, Rehovot‐13, Ontario 7710 and Lycopersiconpimpinellifolium P.I. 126927 were found to be resistant to the pathogen. VF‐198 and Tropic‐VF were the most susceptible. Extra Marmande, Saladette, Acc.339944–3 and the wild type Lycopersicon esculentum var. cerasiforme were moderately resistant.
Uptake and distribution of nitrogen in wheat plants supplied with different amounts of nitrogen after stem elongation
Authors: PEREZ PILAR , MARTINEZ‐CARRASCO R. , PUENTE L. SANCHEZ DE LA
Published: February 2008

The uptake of nitrogen and its distribution between shoots and between organs within shoots in wheat (Triticum aestivum) was studied from the start of stem elongation to 28 days after anthesis in a glasshouse experiment with eight nitrogen levels between 0·1 and 12·8 mequiv./litre.

There was no net uptake of nitrogen in plants supplied with 0·8 mequiv./litre or less; with more nitrogen the absorption increased linearly. Twenty to 44% of the total plant nitrogen was absorbed after anthesis, this fraction increasing with nutrient supply. The nitrogen allotted to the main shoot decreased until the onset of anthesis and increased thereafter at the expense of the tillers, except with 12·8 mequiv./litre, where nitrogen percentage in the main shoot decreased also after anthesis. Raising nitrogen supply increased the proportion of plant nitrogen recovered in the tillers.

Nitrogen accumulated in the ear after emergence and by the 28th day after anthesis it contained between 52% and 73% of the total plant nitrogen. The ear of the main shoot had a higher proportion of shoot nitrogen than that of the tillers. The fraction of ear nitrogen supplied by retranslocation decreased from almost 100% with 0·8 mequiv. N/litre or less to nil with 12·8 mequiv./litre. Increasing nitrogen application decreased the fraction of total nitrogen allocated to the ear.
Factors determining the microflora of stored barley grain
Authors: HILL R. A. , LACEY J.
Published: February 2008

Colonisation of barley grain has been studied during storage at different water contents and with and without restriction of the air supply to simulate conditions in unsealed silos. Grain stored with a water activity >0·9 aw (20% water content) heated spontaneously when aeration was unrestricted, the maximum temperature attained increasing with aw to 58 °C at 1·0 aw (39% water content). The presence of many unripe grains increased the tendency to heat at a given mean water content. Although heating was prevented by sheeting to restrict the air supply, it could occur subsequently when the sheeting was removed. Both heating and restriction of the air supply were associated with increased carbon dioxide (to >25%) and decreased oxygen concentrations (to <5%). Germination of grain after 6·9 months storage was correlated with aw; germination levels approaching 100% were retained only at about 0·7 aw (13·5% water content). Colonisation by Aspergillus species was correlated with aw and temperature and similar correlations with Penicillium species were also found, with P. verrucosum var. cyclopium abundant at 0·85‐0·90 aw (17·20% water content) and P. piceum, P. funiculosum and P. capsulatum at 0·90‐0·95 aw (20–25% water content). In sealed containers P. roquefortii occurred at 1·00 aw (39% water content) and P. hordei at 0·90‐0·92 aw (20–22% water content). Spores of fungi and actinomycetes formed during spontaneous heating of grain survived 6 months sealed storage although Absidia corymbifera and Micropolyspora faeni may have declined in numbers. Fungicides applied to the ripening grain had only limited effect on the colonisation of the grain during storage.
Resistance reactions of Cucumis melo to inoculation with Pseudoperonospora cubensis
Authors: REUVENI R.
Published: February 2008

Reactions of several cultivars and breeding lines of melons to artificial inoculation at the seedling stage with a local isolate of Pseudoperonospora cubensis were compared under growth chamber and field conditions. Four different reactions were distinguishable: highly susceptible, susceptible, partially resistant and resistant. The differences in the reactions were more clear‐cut under growth chamber conditions. Selection for resistance could be carried out at the seedling stage using sporangia production and lesion size, shape, colour and number as criteria. Under growth chamber conditions, plants of resistant lines had minimal sporangia production and circular or angular lesions 1–2 cm in diameter which became necrotic within 5 days after inoculation.
Interactions between seed priming treatments and nine seed lots of carrot, celery and onion. II. Seedling emergence and plant growth
Authors: BROCKLEHURST P. A. , DEARMAN JANE
Published: February 2008

Samples of three seed lots of each of three cultivars of carrot, celery and onion were primed in polyethylene glycol solution for two weeks at 15 °C. Seedling emergence was recorded in the field for carrot and onion and in the glasshouse for celery. Compared to the untreated control, priming increased the percentage seedling emergence in certain poorly‐emerging seed lots of carrot and celery, but had no effect on onion. Mean emergence times were reduced by priming in all seed lots, by 3–5, 5–8 and 3–9 days in carrot, celery and onion respectively. The largest effects occurred in the slowest‐emerging seed lots. There were significant interactions between priming and seed lots within cultivars in carrot and celery and between priming and cultivars in celery and onion. Priming generally reduced the spread of emergence times, but the effects were not statistically significant in carrot.

Drying back the primed seeds had no effect on percentage emergence in onion, but reduced it (compared to primed seed which had not been dried‐back) in certain carrot and celery seed lots. Primed and dried‐back seeds emerged later than primed seeds, by up to 1·5, 2·6 and 2·6 days in carrot, celery and onion respectively. The spread of emergence times was generally larger for primed and dried‐back seeds than for primed seeds, but the differences were not always statistically significant.

Plant fresh weights were recorded 9, 7 and 12 wk after sowing for carrot, celery and onion, respectively. In each species, mean plant weight was inversely related to seedling emergence time; thus plants grown from primed seed were always heavier than the controls, by up to 33%, 182% and 47% in carrot, celery and onion respectively.
The effect of barley yellow dwarf virus on field populations of the cereal aphids, Sitobion avenae and Metopolophium dirhodum
Authors: AJAYI BY OLUPOMI , DEWAR A. M.
Published: February 2008

The numbers of cereal aphids, especially Metopolophium dirhodum in 1979, and Sitobion avenae in 1980, were significantly increased on BYDV infected wheat and oats in 1979, and wheat, barley and oats in 1980.

The differences were probably caused by attraction of alates of each species to virus infected plants which had changed colour as a result of their infection. Significantly more alates of M. dirhodum were found on virus infected oats in 1979, and of S. avenae on oats and barley in 1980, although not on wheat in either year. probably because the colour contrast in wheat was less intense than in the other crops.

Flight chamber experiments with alates of both species confirmed their visual attraction to virus‐infected leaves. The interaction between virus, vector and host plants is discussed with reference to the ecology of virus spread.
A comparison of inoculation methods for determining potato cultivar reaction to black leg
Authors: HOSSAIN M. , LOGAN C.
Published: February 2008

Two methods of inoculating tubers, one by dipping them in an aqueous suspension of Erwinia carotovora subsp. atroseptica, the other by inserting the end of a wooden toothpick charged with undiluted bacteria into the rose‐end near a sprout, were compared over two years for their ability to produce black leg and for their effect on plant growth and yield on a number of cultivars chosen because of expected differences in susceptibility. Although both methods produced a similar rank order for cultivar reaction, the more consistent results were obtained using the toothpick method, clear differences in black leg incidence and yield being evident between the susceptible cultivars Ulster Sceptre and Maris Bard and the more resistant Pentland cultivars. As some cultivars appear more tolerant to black leg than others, yield may be as important a criterion as disease incidence when assessing overall cultivar performance.

The inoculation of the base and middle of stems and the infiltration of the bacterium into tubers were also investigated as alternative methods for assessing cultivar susceptibility.
The effect of Erwinia carotovora subsp. atroseptica (blackleg) on potato plants. I. Growth and yield of different cultivars
Authors: LAPWOOD D. H. , LEGG PHILIPPA R.
Published: February 2008

The effect of planting seed tubers inoculated either near the stolon attachment (heel end), among the eyes at the apex (rose end) or mid‐way along the tuber with Erwinia carotovora subsp. atroseptica, was assessed in terms of growth of the plant, disease symptoms and yield. Invariably rose‐end inoculation had the greatest and heel‐end the least effect in decreasing yield when compared with uninoculated plants. Cultivars Majestic and King Edward were the most susceptible, Pentland Crown showed some resistance to invasion of stems (blackleg) although plant vigour, expressed in terms of plant height and stem number was affected and Maris Piper was the most resistant.
The effect of Erwinia carotovora subsp. atroseptica (blackleg) on potato plants. II. Compensatory growth
Authors: ADAMS M. J. , LAPWOOD D. H.
Published: February 2008

In field experiments in 1981 and 1982, uninoculated seed tubers (cv. Désirée) and those inoculated with Erwinia carotovora subsp. atroseptica at the rose (apical) or heel (stolon attachment) ends were planted at normal (35 cm) or double spacing; in additional plots, inoculated and uninoculated tubers were planted alternately.

Inoculation, especially at the rose end, decreased plant height and sometimes resulted in blackleg symptoms. Individual plant yields were recorded at the end of the season. In plots of uniform seed type at normal spacing, inoculation decreased total yield compared with uninoculated by 12–13% (heel‐end inoculation) or 26–40% (rose‐end inoculation). At double spacing, yields increased compared with normal spacing by 44–58% (uninoculated or heel‐end inoculation) or 30–39% (rose‐end inoculation). When rose‐end‐inoculated and uninoculated seed tubers were planted alternately, inoculated plants yielded less and uninoculated plants more than in plots planted throughout with the same seed treatment. The abilities of inoculated and uninoculated plants to compensate for weak or missing neighbours were combined using equations to predict the yields of crops with different proportions of diseased or missing plants.
Improved methods for the purification and detection of cocoa swollen shoot virus
Authors: ADOMAKO D. , LESEMANN D.‐E. , PAUL H. L. , OWUSU G. K.
Published: February 2008

The extraction of cocoa swollen shoot virus (CSSV) from cocoa leaves with pectinase, purification from the concentrated extracts by filtration through Celite and Sepharose 2B, and concentration of the virus by isopycnic CsCl centrifugation are described. The pectinase and Celite treatments effectively removed mucilage and particulate host plant materials, and enhanced the release of virus particles, Isopycnic CsCl centrifugation resulted in 10–100‐fold concentration of particles, but with apparent loss of infectivity.

After extraction with pectinase, CSSV particles were regularly seen by electron microscopy in sap. Immunosorbent electron microscopy (ISEM) considerably enhanced the detection of CSSV in sap. The particles were bacilliform or bullet‐shaped and of various lengths. The common dimensions were 142 × 27 nm.
The influence of straw disposal and cultivation regime on the population dynamics ofBromus sterilis
Authors: FROUD‐WILLIAMS R. J.
Published: February 2008

The effects of straw‐burning and cultivation regime upon the population dynamics of a naturally‐occurring infestation of Bromus sterilis were investigated over a period of 11 months. Both grain and straw of the original crop were seriously contaminated with seeds of this species.

An initial population of 12 635 seeds m‐2 declined by 85% between July and late August in uncultivated stubble without straw‐burning, but only 44% of seeds gave rise to seedlings. A further 10% had produced seedlings by late December and another 5% emerged between February and April. By April no viable seed remained.

Straw‐burning destroyed 97% of the ungerminated seeds on the soil surface and reduced seedling numbers by 94%. However, those seedlings which did survive formed many tillers and produced considerable quantities of seed.

Shallow cultivation reduced the seed population by 34% and in April there were 47% fewer seedlings on these plots than on direct drilled ones. Ploughing to a depth of 20 cm eradicated the weed; and although buried seeds germinated, they failed to emerge.

Seedlings emerging in spring failed to flower before harvest. Detailed laboratory investigation showed that although B. sterilis does not have a pronounced requirement for vernalisation, chilling did accelerate flowering, while long‐day photoperiods were required for panicle extension. Only germinated seeds responded to the vernalisation stimulus.
The genetical control of incomplete forms of resistance to Erysiphe graminis in spring barley
Authors: ASHER M. J. C. , THOMAS W. T. B. , THOMAS C. E.
Published: February 2008

Eight spring barley lines exhibiting incomplete resistance to powdery mildew in field trials were crossed and back‐crossed to a common susceptible parent to produce the basic generations (P1 P2, F1 F2, B2 B2) required for a genetical investigation. By means of joint scaling tests, disease assessments on adult plants in a field trial were used to estimate the genetic parameters contributing to resistance. Lines with major genes, which appeared partially resistant due to the presence of corresponding virulence, were characterised by the presence of a significant dominance component in the analysis. Partially resistant lines which either lacked identifiable major genes or with major genes that were ineffective in the trial, but with good background resistance, could also be distinguished. Significant additive and epistatic effects were detected in all crosses. The prospect of enhancing partial resistance through hybridisation and selection is discussed.
The effect of gibberellins on the storage life of plantains
Authors: GEORGE J. B. , MARRIOTT J.
Published: February 2008

Dipping plantain fruits in gibberellins (GA4/7 or GA3) delayed the ripening of individual fruits by approximately 50%, the two treatments being equally effective. Measurement of the preclimacteric period (PCP) by increased respiration showed that plantain fruits vacuum infiltrated with GA4/7 (10‐5 M) gave an extension of 37% in the PCP under high humidity. No effect was observed at low humidity. The use of gibberellins on plantain storage is discussed.
Effects of temperature, light, nitrate and pre chilling on seed germination of grassland plants
Authors: WILLIAMS E. D.
Published: February 2008

The effects of factorial combinations of alternating (20/10 oC) and constant temperature (20 oC), of light (intermittent) and dark, and of distilled water and nitrate on the germination of a range of species of indigenous grassland were investigated in 1979, and in 1980 when the effects of pre‐chilling were also studied.

Species differed greatly in their response to the eight sets of environmental conditions in 1979. With the exception of Lolium perenne ssp. perenne and Cynosurus cristatus, only a small percentage of seeds of most species was able to germinate in constant temperature in the dark. However, when light was supplied there was moderate germination of Anthoxanthum odoratum, Cerastium fontanum ssp. glabrescens, Festuca rubra, Holcus lanatus and Poa trivialis. Alternating temperature greatly increased the germination of most species and nitrate further increased germination of Agrostis capillaris, Deschampsia caespitosa, H. lanatus, Poa annua and P. trivialis. In alternating temperatures, light increased germination of these species even more than did nitrate. A. capillaris, D. caespitosa and P. annua required all three factors for maximum germination, and another 7% of seeds of A. capillaris also required gibberellic acid. Germination responses following sequential application of factors often differed from those resulting from simultaneous treatment: in particular, the germination of Ranunculus species was greatly enhanced.

Although seeds of the species tested in 1980 were more germinable than those of the same species in 1979, they responded similarly to the different factors. Light increased the germination of both Taraxacum officinale and Plantago lanceolata in constant but not in alternating temperature, while nitrate was much more stimulatory to the latter species. About half the seeds of P. lanceolata were dormant. Pre‐chilling at 4oC for 7 days increased subsequent germination of all species when followed by constant temperature, except of A. capillaris in the dark and C. cristatus (already maximal) in the light. When followed by alternating temperature in the dark, pre‐chilling greatly decreased germination of A. capillaris. In the light, where germination of most species was maximal, there was little effect of pre‐chilling. Longer durations (21 and 42 days) of chilling of older seed gave similar results to the 7 day pre‐chilling.
Evidence that maize wallaby ear disease is caused by an insect toxin
Authors: OFORI F. A. , FRANCKI R. I. B.
Published: February 2008

Colonies of the leafhopper Cicadulina bimaculata were established from single male and female insects raised from surface sterilised eggs and shown to be free of leafhopper A virus (LAV). Insects from these colonies were as capable of inducing maize wallaby ear disease (MWED) in maize seedlings as those with LAV indicating that the virus is not involved in the etiology of MWED.

Maize seedlings colonised by C. bimaculata in glasshouse trials developed initial MWED symptoms within 6–8 days of infestation. The symptoms intensified thereafter and many plants died after more than 16 days' exposure, even after the insects were killed with insecticide. However, when freed from the insects before symptoms became very severe, plants recovered and assumed normal growth. These observations support the view that MWED is caused by an insect toxin.
Aerated‐steam treatment for control of Alter nana tenuis on lobelia seed
Authors: HALL T. J. , TAYLOR G. S.
Published: February 2008

Alternaria tenuis may cause severe seedling blight, damping‐off and leaf spotting of the bedding plant lobelia. Disease transmission from seed naturally and artificially infected by A. tenuis was demonstrated and the pathogenicity of four isolates established. Soaking of lobelia seed in 0–2% thiram suspension at 30 oC for 12 h adversely affected the rate of germination and did not consistently reduce infection to acceptable levels. Treatment with aerated steam at 50–51 oC for 15–20 min reduced seed infection to undetectable or insignificant levels and caused only slight damage to the seed. In glasshouse trials seed treated with aerated steam performed significantly better than seed soaked in thiram suspension both in terms of germination and foliage production.
Production and characteristics of antisera to Spiroplasma citri and clover phyllody‐associated antigens derived from plants
Authors: CLARK M. F. , BARBARA D. J. , DAVIES D. L.
Published: February 2008

Antisera were produced to clover phyllody‐ and Spiroplasma citri‐associated antigens partially purified from infected Vinca rosea plants. Separate antisera were made to ‘membrane fraction’ (MF) preparations comprising the resuspended pellet obtained by high speed centrifugation, and to ‘soluble fraction’ (SA) preparations, comprising the supernatant from high speed centrifugation concentrated by freeze‐drying.

All antisera showed considerable activity against normal plant antigens but after cross‐absorption with extracts of healthy plants the MF antisera were used in F(ab')2based ELISA tests to detect S. citri‐ or clover phyllody‐associated antigens in infected plants. The ‘clover phyllody’ antiserum also reacted specifically with extracts of clover plants with phyllody, and with naturally‐infected strawberry plants showing symptoms of green petal disease. Both the ‘clover phyllody’ and S. citri antisera were specific for their respective homologous antigens. No cross‐reactions were observed in heterologous tests or between either antiserum and extracts of V. rosea infected with various MLOs obtained from different host plants.
Hydrangea mosaic virus, a new ilarvirus from Hydrangea macrophylla (Saxifragaceae)
Authors: THOMAS B. J. , BARTON R. J. , TUSZYNSKI ANNA
Published: February 2008

A previously unrecognised virus isolated from Hydrangea macrophylla with chlorotic mosaic leaf symptoms in West Sussex was named hydrangea mosaic virus (HydMV). HydMV was mechanically transmitted without difficulty to four of 16 species from three of five families, and was seed transmitted in Chenopodium quinoa, but was not aphid transmitted.

Although relatively unstable in vitro, HydMV was purified by clarifying leaf extracts by emulsification with chloroform and acidification with citric acid, followed by differential centrifugation and sucrose density gradient centrifugation. Purified virus incompletely separated on sucrose density gradients into three components (T. M and B) with sedimentation coefficients (so20w) of 86, 97, and 105 S respectively, but all particles had buoyant densities in caesium chloride of 1.37 g/cm3. Virus contained a single polypeptide species (mol. wt 26.4 times 103), appeared quasiisometric to ovoid or elliptical, and measured c. 28 times 30 (T), 30 times 30 (M) or 30 times 32–38 nm (B). Single‐stranded RNA species or mol. wt 1–25, 1–08, 0–83, 0–36 and 0–27 (RNA‐1 to 5 respectively) were obtained from virus preparations but mixtures containing RNA‐1 to 3 plus either RNA‐4 + 5 or the coat protein, were infective.

These properties suggest that HydMV has affinities with ilarviruses, but it showed no serological relationship to any of six ilarviruses or 42 other viruses.
Bromide residues in transplanted brassicas following methyl bromide treatment of seedbed and field
Authors: WHITE J. G. , HUNT J.
Published: February 2008

Methyl bromide applied to brassica seedbeds resulted in bromide concentrations in cabbage, cauliflower and Brussels sprout transplants of 389‐4‐2082‐3 mg/kg fresh tissue. When the transplants were grown to maturity on untreated field plots bromide concentrations in the plants fell to levels similar to those occurring naturally. Treatment with methyl bromide of both seedbeds and field plots resulted in plant bromide concentrations in cabbage plants of 211‐4 mg/kg, a level in excess of the proposed maximum residue limit of 100 mg/kg fresh matter. Bromide concentrations in the edible portions of cauliflower were between 24‐8 and 96‐0 mg/kg and those in Brussels sprouts between 49‐3 and 121‐3 mg/kg.
Transmission of Fusarium solani var. coeruleum and F. sulphureum from seed potatoes to progeny tubers in the field
Authors: ADAMS M. J. , LAPWOOD D. H.
Published: February 2008

In experiments in three years, seed tubers were inoculated before planting with either Fusarium solani var. coeruleum or F. sulphureum to initiate a rot, or were contaminated by dipping in soil slurries containing spore suspensions of one or other of the pathogens. Transmission to progeny tubers was tested by uniformly wounding and incubating tubers and by dilution plating of soil samples.

In two years, transmission of F. sulphureum was greater from highly contaminated than from rotting seed and was greater on cv. Pentland Crown than on cvs Desiree and Maris Piper. F. solani var. coeruleum appeared to be transmitted most readily from rotting seed and Maris Piper was the cultivar most extensively contaminated. In experiments with different harvest dates, transmission of both fungi from highly contaminated seed could be detected by late June or mid‐July. More progeny tuber wounds rotted in F. sulphureum than in F. solani var. coeruleum plots and in one year, F. sulphureum caused more rots on cv. Record than on cv. Maris Piper.

These differences between the pathogens may be related to their differing abilities to sporulate underground on the surface of seed tubers and on stem bases.
The effect of Rhizobium inoculation and nitrogen fertiliser on nitrogen fixation and seed yield of dry beans (Phaseolus vulgaris)
Authors: TAYLOR J. D. , DAY J. M. , DUDLEY C. L.
Published: February 2008

The potential benefit to be derived from seed inoculation of Phaseolus vulgaris beans with effective strains of Rhizobium phaseoli, was investigated in field experiments over three years on a site low in soil nitrogen and lacking indigenous effective strains of R. phaseoli.

Inoculation with R. phaseoli (strain RCR 3644) produced significant increases in nodulation, nitrogenase activity and plant growth in all experiments. In trials in 1978 and 1979, with cv. Seafarer, inoculation, in the absence of nitrogen fertiliser doubled seed yields. In 1978, the seed yields from inoculated beans without nitrogen fertiliser (1–6 t/ha) were not significantly different from those obtained with uninoculated beans receiving the optimum nitrogen fertiliser treatment of 120 kg N/ha (1–75 t/ha). In 1979, with lower rainfall favouring more efficient utilisation of nitrogen fertiliser, inoculation gave seed yields (1–88 t/ha) equivalent to those obtained with 60 kg N/ha (1–70 t/ha) but significantly less than with 120 kg N/ha (2–88 t/ha). More precise estimates from nitrogen response curves showed that inoculation supplied the fertiliser equivalent of 105 and 70 kg N/ha in 1978 and 1979 respectively. In both years, significant benefits were also obtained by the combination of inoculation and nitrogen fertiliser.

In a separate experiment in 1979, with four R. phaseoli strains inoculated onto eight bean cultivars, three were highly effective nitrogen fixers on all cultivars. Two strains (RCR 3644 and NVRS 963A) each increased mean yields, in the absence of nitrogen fertiliser, from 1–39 t/ha uninoculated to c. 2–5 t/ha inoculated whilst strain RCR 3622 was outstanding with a mean yield of 3‐0 t/ha. An analysis of the nitrogen content of seed showed that gains from nitrogen fixation were 37–57 kg N/ha/growing cycle for the combination RCR 3644 with cv. Seafarer. However, 106 kg N/ha/growing cycle was recorded for the combination RCR 3622 and cv. Aurora.
A satellite‐like nucleic acid of arabis mosaic virus associated with hop nettlehead disease
Authors: DAVIES D. L. , CLARK M. F.
Published: February 2008

An isolate of arabis mosaic virus (AMV) from a hop plant with symptoms of nettlehead disease induced unusually severe symptoms when transmitted to Chenopodium quinoa. This isolate, called AMV‐Ta, yielded particle preparations in which up to 80% of the nucleic acids consisted of a species of low molecular weight (SNA), estimated to be about 75 000 daltons by polyacrylamide gel (PAG) electrophoresis.

An isolate free of detectable S‐NA (AMV‐To) was derived from AMV‐Ta by inoculating plants with the two high molecular weight genomic RNA species of AMV (2–8 times 106 and 1–3 times 106 daltons; Murant, 1981) separated from S‐NA by PAG electrophoresis. This isolate induced much milder symptoms in C. quinoa. Hop seedlings inoculated with AMV‐Ta, either mechanically or by nematodes, developed characteristic nettlehead symptoms. Hop seedlings similarly inoculated with AMV‐To remained free of nettlehead symptoms.

Two species of S‐NA associated with hop nettlehead isolates of AMV were detected at two sites in Kent, and two West Midlands sites. At both sites in Kent and at one of the West Midlands sites, the occurrence of the S‐NA species was closely correlated with the incidence of nettlehead symptoms. At the other site in the West Midlands, the occurrence of nettlehead symptoms was too erratic to allow positive correlation of SNA with symptom development.

Our results show that S‐NA plays an active part in symptom production in experimentally inoculated plants of both hops and C. quinoa. In addition, the close correlation between the occurrence of AMV with additional nucleic acid species, and the incidence of nettlehead symptoms in commercially grown hops, suggests a role for S‐NA in the aetiology of this disease.
Efficacy of avermectins against a plant parasitic nematode
Authors: WRIGHT D. J. , BIRTLE A. J. , CORPS A. E. , DYBAS R. A.
Published: February 2008

Avermectins (AVM) B1a/1b and B2a‐23‐one rapidly impaired the locomotor activity of Meioidogyne incognita second stage juveniles. On agar plates, concentrations as low as 0–0003 μg AVM B2a‐23‐one cm‐3 significantly reduced the number of juveniles in cucumber roots and the proportion of juveniles which developed to a saccate stage. The effects of AVM on hatching and movement of nematodes appeared to be at least partly reversible.
Effect of the nematicide oxamyl on the multiplication of Globodera rostochiensis and G. pallida and on the haulm growth and yield of six potato cultivars with different levels of resistance and tolerance
Authors: TRUDGILL D. L. , HOLLIDAY J. M. , MATHIAS P. L. , FRENCH N. , MACKINTOSH G. M. , TONES S. J.
Published: February 2008

The effect of a pre‐planting application of oxamyl on the yields of six potato cultivars was studied in co‐operative field trials in 1981. Two sites were ‘uninfested’ with potato cyst nematodes (PCN), two were lightly infested (<25 eggs/g soil) and six were moderately to heavily infested (three with Globodera rostochiensis and three with G. pallida). At the uninfested and lightly infested sites oxamyl had little effect on mid‐season haulm weights or on final tuber yields. At sites moderately to heavily infested with G. rostochiensis the haulm growth of all cultivars tended to be increased by a similar amount on plots treated with oxamyl, Pentland Dell being least responsive. Yield was increased by different amounts, the increases being least for cvs Cara and Maris Piper and most for Corsair and Pentland Dell. At the sites moderately to heavily infested with G. pallida Cara was again tolerant, its yield being increased little by oxamyl compared with the other cultivars. Maris Piper gave the largest yield increase.

Final populations of PCN on non‐resistant cultivars were reduced by oxamyl at some sites but not at others. Resistant cultivars also decreased the final numbers of PCN at most sites. Two cultivars derived from Solanum vernei with different degrees of resistance, appeared to be almost equally effective in controlling G. rostochiensis and G. pallida.