bluuebunny/crossref_metadata_2025 huggingface dataset:
The distribution and persistence of iprodione applied by thermal fogging in a glasshouse tomato crop
Authors: MORGAN WALTER M.
Published: February 2008

Deposits collected on filter paper after application of a ready‐to‐fog formulation of iprodione and the residues of iprodione washed from tomato leaves after fog and HV spray application were analysed by gas‐liquid‐chromatography. Relatively heavy deposits were found close to the fogging machine but the deposit became lighter with increasing distance from the machine and in positions lateral to the stream of fog. The deposit collected within the leaf canopy was considerably lighter than that collected above the plants. Residues of iprodione on plants treated with HV sprays were always considerably higher than on fogged plants given a comparable rate of application. After repeated treatment, a substantial build‐up of residue was found, but the amount on fogged plants was approximately half that on plants treated with HV sprays. There was a good correlation between the residue found on plants at six positions within the glasshouses and the incidence of infection from artificial inoculations of Botrytis cinerea on petioles.
Natural distribution, spread, and variation, in the tobacco mosaic virus infecting Nicotiana glauca in Australia
Authors: RANDLES J. W. , PALUKAITIS PETER , DAVIES C.
Published: February 2008

Nicotiana glauca is a naturalised introduced species widely distributed in Australia. A survey of stands in the central zone of its recorded distribution has shown that a type of tobacco mosaic virus which characteristically induces a bright yellow mosaic symptom (TMV‐Y) is commonly associated with N. glauca throughout this zone. Surveys of a natural community of N. glauca less than 5 yr old, and in an experimental block, showed that TMV‐Y could spread at a rate, and in a pattern, which could not be explained by contact transmission alone, and which indicated that an airborne vector was probably involved in transmission. These results together have led to the conclusion that the common association of TMV‐Y with N. glauca is due to spread of the virus by an unknown vector(s). Seed transmission of TMV‐Y in N. glauca has not been detected.

Molecular hybridisation analysis has shown that all but one of the TMV‐Y isolates studied were related to TMV‐U2, and that the isolate which was unrelated to U2, was partially related to TMV‐U1, TMV‐U5, and tomato mosaic virus. Selected isolates which showed a close relationship to TMV‐U2, also showed a close relationship to TMV‐U5, a distant relationship to TMV‐U1, and tomato mosaic, and very little or no relationship with three other tobamoviruses (sunn‐hemp mosaic virus, odontoglossum ringspot virus, and cucumber virus 4). These results show that the Australian TMV‐Y isolates are similar to the TMV isolated from N. glauca in California.
Effects of decreasing the number of grains in ears of cvs Hobbit and Maris Huntsman winter wheat
Authors: RADLEY M. E. , THORNE G. N.
Published: February 2008

At 6 days after anthesis, grain numbers in ears of Maris Huntsman and Hobbit winter wheat growing in the field were decreased either by removing the two lower grains in each spikelet (degraining) or by removing the top half of the ear (halving). At maturity, degraining increased the dry weight of the third grains in each spikelet of Maris Huntsman by 11% and of Hobbit by 40%, compared with third grains in intact ears. Halving increased the mean dry weight of all the grains in the lower six spikelets of the ear slightly less; it increased the number of grains in Hobbit but not in Maris Huntsman. The responses to halving in Hobbit were greater with additional nitrogen fertiliser.

At 28 days after anthesis in both varieties, degraining increased grain dry weight and the amount of water, reducing sugar, amino acids and total nitrogen in third grains. Effects of halving on these properties of the two lower grains of each spikelet were much less or nil. The increases in nitrogen content of grains at 28 days and at maturity caused by degraining or halving were relatively greater than the increases in dry weight and were similar in the two varieties.
Experimental studies on the responses of European siricid woodwasps to host trees
Authors: SPRADBERY J. P. , KIRK A. A.
Published: February 2008

A study was made of the oviposition responses of the siricid woodwasps, Sirex noctilio, S. juvencus, S. cyaneus and Urocerus gigas to experimentally debilitated spruce and pine trees. Treatments included felled, fire‐burned, logged and girdled trees which were treated at intervals before bioassay with cages siricid females. In comparable treatments, S. noctilio showed a distinct preference for pines although it was quite successful on spruce while the other siricid species displayed a preference for spruce. The Sirex species successfully attacked more recently treated material although U. gigas showed a preference for timber in a more advanced state of debility. All species showed preferences for girdled trees although other treatments were also favoured by the different siricid species. Overall, the siricids preferred the area above the girdle irrespective of tree species and there was a higher rate of eggs above the girdle in treated spruce trees. A wide range of moisture content in the timber appeared to have no effect on drilling activity or the successful development of eggs. The response of a wild population of S. juvencus to the treated spruce is also described. The results are discussed in relation to the ecology of Siricidae in Europe and the establishment of S. noctilio in Australia. It is suggested that of the species studied, only S. noctilio poses a serious threat to the living pine stands of Australia.
Disease progress of non‐specialised fungal pathogens in intraspecific mixed stands of cereal cultivars. I. Models
Authors: JEGER M. J. , GRIFFITHS ELLIS , JONES D. GARETH
Published: February 2008

Two mathematical models are presented which describe progress of disease, caused by an unspecialised pathogen, in pure and mixed stands of cereal cultivars. One is a simple, discrete model utilising the parameters infection frequency (lesions/spore) and sporulation rate (spores/lesion/event) on each cultivar. The model predicts that, in most circumstances, the amount of disease in mixtures will be equal to or less than the arithmetic mean of the component pure stands. An increase in disease is only predicted in situations where the ranking of cultivars with respect to infection frequency and sporulation rate is opposed. In the other model differential equations are proposed. Solutions of these equations indicate that disease amelioration can usually be expected in such mixtures, confirming the conclusions of the discrete model and that disease levels will deviate around the geometric, rather than arithmetic, mean of the pure stands. However the advantages of this model lie in wider generality and conceptual, rather than practical, utility.
Disease progress of non‐specialised fungal pathogens in intraspecific mixed stands of cereal cultivars. II. Field experiments
Authors: JEGER M. J. , JONES D. GARETH , GRIFFITHS ELLIS
Published: February 2008

Epidemic development of Septoria nodorum was examined in pure stands and mixtures of two spring wheat cultivars, Kolibri and Maris Butler. In mixtures, disease development was reduced almost to that of the more resistant pure stand (Maris Butler). Disease levels, however, were low and no significant differences in grain yield per head were demonstrated. Disease development was further investigated for the host‐pathogen combinations winter wheat/S. nodorum and winter barley/Rhynchosporium secalis. With both combinations the mixed stands again reduced disease levels to almost that of the more resistant pure stands. In general, mixed stands were more effective against R. secalis, although, with S. nodorum, disease levels were low. The yield response in mixed stands differed for the host cultivars and was not significantly changed by the presence of disease. The complexity of analysing such situations and the implications of these findings for mixtures of cultivars differing in resistance to non‐specialised pathogens are discussed.
The effect of minimum cultivation on the incidence of take‐all down the root profile of winter wheat
Authors: PREW R. D.
Published: February 2008

The effects of direct drilling, shallow cultivation and ploughing on the infection of winter wheat roots by the take‐all fungus (Gaeumannomyces graminis var. tritici) were studied on three field sites over a number of years. All three soil types were categorised by Cannell, Davies, Mackney & Pidgeon (1978) as suitable for sequential direct drilling. The results show that a smaller proportion of roots was infected at depth in the direct‐drilled plots in May/June. However by July these differences had all but disappeared and an estimate of infection in the top 7 cm of the roots (approximately equivalent to traditional hand sampling for take‐all) gave a reliable comparison of the total take‐all on plants grown under these different cultivation systems.
Epidemiology of vascular‐streak dieback of cocoa
Authors: KEANE P. J.
Published: February 2008

Inoculation studies provided further evidence that Oncobasidium theobromae is the cause of vascular‐streak dieback of cocoa and that the fungus can penetrate undamaged, soft leaves. Spores are forcibly ejected from basidia at night and dispersed by wind. They are rapidly killed by exposure to normal day‐time conditions and require free water for germination. Spore dispersal is probably very limited under plantation conditions and disease spread occurs along a steep gradient into new plantings. Disease increase in young plantations was found to occur at a rate of 0.31 per unit per month; in one block 100% of seedlings were infected and 55% were killed within 33 months of planting. The disease was most damaging in seedlings younger than 18 months old, although there was evidence that it also caused substantial yield loss in mature susceptible cocoa. Sporophore production and infection rate were correlated with rainfall incidence. The unusual grographical distribution of the disease and aspects of its control are discussed.
Properties of spinach yellow mottle, a distinctive strain of tobacco rattle virus
Authors: KURPPA A. , JONES A. T. , HARRISON B. D. , BAILISS K. W.
Published: February 2008

A virus (isolate SYM) obtained from spinach plants in England with a severe yellow mottle disease induced symptoms resembling those of tobacco rattle virus (TRV) in several indicator species but caused systemic necrosis in Chenopodium amaranticolor and C. quinoa. It was transmitted to bait plants grown in soil containing the nematode Trichodorus primitivus.

Purified virus preparations contained rod‐shaped particles that were predominantly of four modal lengths: 188 nm (L particles), 101 nm (S particles), 57 nm and 48 nm (together called VS particles), containing RNA with mol. wts of 2.4, 1.5, 0.7 and 0.6 million, respectively. L particles (s°20= 300 S) and S particles (230 S) greatly outnumbered VS particles (c. 150 S). All particles contained a single polypeptide species with estimated mol wt of 24 700, slightly larger than those previously reported for tobraviruses. Purified L particles were infective but both L and S particles were needed to induce the production of virus nucleoprotein particles. VS particles were not infective and apparently had no qualitative or quantitative effect on infection by L or by L plus S particles. S particles carried determinants for serological specificity and ability to invade C. amaranticolor systemically.

Isolate SYM produced pseudo‐recombinants with isolate PRN of TRV. Also, isolates CAM, OR and PRN of TRV, and isolate SYM, were found to be distantly related by three kinds of serological test. No relationship was detected between these isolates and pea early‐browning virus in gel‐diffusion precipitin tests or electron microscope serological tests, but a distant relationship between isolate SYM and pea early‐browning virus was found by micro‐precipitin tests. Isolate SYM therefore has closer affinities with TRV than with pea early‐browning virus and is considered to be a distinctive strain of TRV.
The expression of resistance to powdery mildew infection in winter wheat cultivars. I. Seedling resistance
Authors: BENNETT FIONA G. A.
Published: February 2008

Detached seedling leaf tests were used to assign 18 winter wheat cultivars to three wheat mildew resistance (WMR) groups on the basis of identified race‐specific resistance characters. The same cultivars were exposed in mobile seedling nurseries from 1976 to 1979. Infection by mildew populations containing matching pathogenicity characters was used to recognise background seedling resistance in three cultivars: Maris Freeman, Maris Huntsman and Sentry. The value of background seedling resistance is discussed.
The expression of resistance to powdery mildew infection in winter wheat cultivars. II. Adult plant resistance
Authors: BENNETT FIONA G. A.
Published: February 2008

Resistance to powdery mildew infection was compared in 18 winter wheat cultivars under field conditions in three seasons, 1977 to 1979. In each year, natural infection occurred from populations of Erysiphe graminis f. sp. tritici containing host‐specific pathogenicity characters matching identified cultivar resistance.

Leaves, ears and stems were assessed separately. The expression of resistance in leaves appeared to be independent of that in ears. There were few consistent differences between cultivars in stem infection. Resistance in adult leaves did not necessarily correspond with that in seedling leaves; resistance in ears did not appear to be correlated with plant height.

Quantitative differences between cultivars having the same identified resistance characters occurred in both leaves and ears; Flinor, Avalon and Bounty were most resistant on leaves whereas Iona, Wizard and Bounty were most resistant on ears. Differences in background resistance were considered to be responsible for these observations.
Breeding of nodulated red clover (Trifolium pratense) for high yield
Authors: NUTMAN P. S. , RILEY JANET
Published: February 2008

The symbiotic effectiveness of four cultivars of red clover were compared and breeding programmes undertaken to increase nitrogen fixation and yield of agar‐ and pot‐grown plants. Programme I used the moderately effective Rhizobium trifolii strain 0403 and Programme II the highly effective strain 5. Aggregate scores of plant size (leaf area) were chosen as the criterion of selection. All cultivars, inoculated with strain 0403, differed in time of initial nodulation and in dry matter yield and three differed in leaf area. None differed in nodule number or N‐content. Dry matter and leaf area were highly correlated. Diallel crosses among highly effective selections in Programme 1 gave progeny yields that exceeded those of crosses between modal selections by averages of 6% in the first generation, 5% in the second generation and 23% in the third generation. Yields of the high cross category exceeded those of the original cultivar by an average of 9% in the second generation and by 25–101% in the third generation. Effects on leaf area were similar. Highly effective progeny tended to nodulate earlier and have more nodules than the remainder but differences were very small. Crosses between cultivars were generally more effective than those within cultivars, indicating heterotic effects. Similar results for yield were obtained in Programme II. The average increase in yield of crosses of third‐generation material between highly effective selections compared with cv. S123 was 63%. The modal crosses were intermediate. In each Programme and generation there were large differences between parents within each cross category.
A model relating yield to individual plant area for predicting growth compensation in Central African field tobacco*
Authors: WIXLEY R. A. J. , SHAW M. J. P.
Published: February 2008

A model based on the concept of the circle of influence of a plant is used to estimate the relationship between yield and area/plant for tobacco crops with gaps in stand. The model predicts the average yield of plants in any configuration that includes missing plants and is used to predict the economic consequences of loss in stand from pest or other damage.
Losses in the conservation and utilisation of grass and forage crops*
Authors: WILKINSON J. M.
Published: February 2008

Losses occur during the conservation of forage crops as a result of plant respiration post‐cutting and post‐harvest; as a result of fermentation, surface deterioration, and (in the case of wet crops) effluent production whilst in store. Further losses occur when conserved forages are given to ruminants; the largest being that of undigested material voided in faeces. Losses during conservation and utilisation can be reduced by minimising the period of field drying and using chemical additives to improve preservation or digestibility.
Inhibition of seed germination and development of tomato plants in soil infested with Pseudomonas tomato
Authors: BASHAN Y. , OKON Y.
Published: February 2008

Infestation of sterilised or natural soil with Pseudomonas tomato at inoculum concentrations of 102 to 109 propagules/ml inhibited germination of seeds and caused damping‐off of tomato cv. VF‐198, susceptible to bacterial speck. Infestation with saprophytic P. fluorescens at an inoculum concentration of 109 propagules/ml did not cause any damage. Germination of seeds of tomato cv. Rehovot‐13, resistant to P. tomato, was not affected in P. tomato‐infested natural soil, but was inhibited when tested in P. tomato‐infested, sterilised soil. Tomato plants which were symptomless from sowing to the flowering stage when growing in infested soil had 20–30% less foliage than plants growing in uninfested soil.
Studies on rose mosaic disease in field‐grown roses produced in the United Kingdom
Authors: THOMAS B. J.
Published: February 2008

Arabis mosaic virus (AMV) and prunus necrotic ringspot virus (PNRSV), separately or together, caused in field‐grown roses the range of symptoms recognised as rose mosaic disease. PNRSV infection alone generally induced chlorotic line patterns, ring‐spots or mottles in the leaves at some time during the growing season; AMV plus PNRSV normally caused chlorotic vein‐banding. However, during prolonged periods of high temperatures (c. 21 °C or more) vein banding occurred in some roses infected only with PNRSV.

Isolates of PNRSV from rose had particles which were similar in shape, protein mol. wt, density and sedimentation coefficients to previously described isolates of PNRSV from cherry, plum and rose; all were cherry serotypes.

In graft‐inoculated roses, apple serotypes of PNRSV induced stunting and chlorosis, puckering and distortion of leaves, which closely resembled symptoms associated with rose mosaic in the USA and chlorotic mottle rose mosaic in New Zealand.

To avoid possible confusion in using the name rose mosaic it is suggested that the virus(es) present in roses should be named.
Rapid indexing of the sunblotch disease of avocados using a complementary DNA probe to avocado sunblotch viroid
Authors: PALUKAITIS PETER , RAKOWSKI ANDREW G. , ALEXANDER DONALD McE. , SYMONS ROBERT H.
Published: February 2008

A routine procedure has been established for the sensitive and specific detection of avocado sunblotch viroid in partially purified nucleic acid extracts of avocado leaves by hybridisation analysis with 32P‐complementary DNA prepared against the purified viroid. Avocado sunblotch viroid was shown to be present in 12 avocado trees that had indexed positive in a biological test for sunblotch disease but was absent from 10 trees that indexed negative. The complete correlation between sunblotch disease and the presence of viroid indicates that the complementary DNA hybridisation assay procedure can be used for the indexing of sunblotch disease. The overall procedure of leaf extraction and hybridisation analysis can be completed in 5 days and is to be compared with up to 2 yr required for indexing by biological methods.

The level of avocado sunblotch viroid in partially purified nucleic acid extracts of a number of different sources of sunblotch infected avocado leaves was found to vary 10 000‐fold from 0.2% to 2 × 10‐5% by weight. The lower limit of detectability of the viroid by the hybridisation assay is considered to be about 10‐5% by weight; this is at least 103 times more sensitive than the detection of the viroid by polyacrylamide gel electrophoresis of the leaf nucleic acid extracts followed by staining.
Application of rapid biochemical methods for detecting avocado sunblotch disease
Authors: ALLEN R. N. , DALE J. L.
Published: February 2008

The method of Palukaitis & Symons (1980) for extracting low molecular weight ribonucleic acids from plant tissue was improved by CF‐11‐cellulose chromatography and further simplified for use in routine biochemical indexing for avocado sunblotch viroid (ASBV). Extracts were prepared routinely at 10 g dry weight equivalents (DWE) of tissue per ml; more concentrated than previously possible with many avocado cultivars. Conditions for assaying extracts of ASBV were standardised and the lower limits for detection determined as 80–230 ng ASBV/g DWE of tissue for polyacrylamide gel electrophoresis (PAGE) and 1 ng/g DWE of tissue for complementary DNA (cDNA) probe assays. The concentration of ASBV in a single infected tree varied from 5 to 5000 ng/g DWE between branches, but only to a minor degree between mature leaves and young blossoms within branches.

Six independent sources of sunblotch disease were examined and all proved positive for ASBV by PAGE. The ASBV extracted from five of these sources hybridised with cDNA prepared from the sixth or standard source (Hass/SB‐1), with hybridisation values ranging from 43% to 89%. In a survey of 76 trees intended for propagation in Australia, all of 17 trees previously accepted as healthy on the basis of graft transmission tests were negative for ASBV by PAGE and had cDNA hybridisation values ranging from 1.8% to 12.1%. Amongst 59 trees apparently free of sunblotch symptoms but not previously indexed, only one tree was positive for ASBV by both PAGE and cDNA probe assay. The other 58 trees were negative by PAGE but had hybridisation values ranging from 1.0% to 42.8%. Forty‐nine trees had values consistent with known healthy trees (<12% hybridisation), while the results of the remaining nine trees will require confirmation by additional tests before a conclusion about ASBV is made.

The cDNA probe assay successfully detected ASBV in avocado seedlings graft inoculated with Hass/SB‐1, 1–2 months before symptoms were displayed but not until 6 months after inoculation. Methods for improving the cDNA probe assay still further are discussed.
Rooted leaf cuttings as an aid in screening for resistance to Plasmodiophora brassicae
Authors: WILLIAMSON CYNTHIA J.
Published: February 2008

Rooted leaf cuttings were used to screen a range of genotypes and cultivars from Brassica spp. and Raphanus sativus for resistance to Plasmodiophora brassicae. The optimum conditions for obtaining equivalent disease incidence and disease severity on leaf cuttings and on seedlings were investigated.

In the method used leaves were cut near the base of the petiole before the lamina was fully expanded. They were kept in a mist propagator for 6 to 18 days and then transferred to a clubroot test bench and individually inoculated with a suspension of resting spores. There was an optimum period for each cultivar between cutting and inoculation which gave the maximum incidence of infection: c. 15 days for Doon Major (swede); 10–15 days for Civasto (stubble turnip) and Giant Rape (forage rape); c. 22 days for Maris Kestrel (marrow stem kale) and c. 10 days for Slobolt (fodder radish). Gall size on rooted leaf cuttings gave a quantitative measure of disease severity equivalent to that on seedlings in tests using the European Clubroot Differential host set, the five above‐mentioned cultivars and four swede cultivars. There was little callus production except on some B. campestris hosts and on cuttings with shoot tissue; microscopic examination was used to confirm the presence or absence of infection in galls.

Hormone rooting powder did not increase the rate of root production in two cultivars of forage rape. Root development was less extensive in B. campestris than in B. oleracea or B. napus. Apparently normal shoots developed on 96% of leaf cuttings (inoculated and uninoculated) in which a fragment of axillary bud tissue was included. The results are discussed in relation to screening for resistance in whole plants and in tissue culture.
The consistency of the resistance of eight carrot cultivars to carrot fly attack at several centres in Europe
Authors: ELLIS P. R. , HARDMAN J. A.
Published: February 2008

Eight carrot cultivars representing the range of resistance to carrot fly damage as assessed in England were grown at 12 sites in five European countries in 1977 and in 1978. The trials provided evidence of agreement with the findings in England for both years in the ranking of cultivars with respect to their resistance to carrot fly damage. The Nantes cultivar Clause's Sytan Original was the most resistant cultivar tested. Consistent results were obtained from sites where carrots were assessed at harvest and carrot fly attack was severe. A significant interaction between sites and cultivars was largely due to sites where carrots were stored prior to assessment.
Perennation in woody fruit plants and its relationship to carbohydrate turnover
Authors: PRIESTLEY C. A.
Published: February 2008

Carbohydrates constitute the principal reserves in temperate woody fruit plants and are depleted during winter, particularly around the time of bud‐break before new growth makes good the losses. Movement of reserves between underground and aerial parts occurs during winter. All perennial parts show alternate depletion and replenishment but root extremities may undergo irreversible depletion and die. Interconversions between soluble carbohydrates and polysaccharides indicate a balance between degradation and synthesis. High growth potential is associated with high starch/starch + sugar ratio.
Some observations in west Wales on the relationships between numbers of alate aphids and weather
Authors: A'BROOK JOHN
Published: February 2008

Some preliminary associations are reported between monthly totals of cereal aphids (Metopolophium dirhodum, Rhopalosiphum insertum, R. padi and Sitobion avenae) caught in suction traps and weather data. Catches at 1.2 and 12.2 m during the summer and autumn flight peaks from 1969 to 1979 were compared with combinations of prior monthly totals of rainfall and accumulated day‐degree temperatures. The best models fitting these results are reported and proposed for testing against future data. The possible relevance of these models, for forecasting whether measures for the control of barley yellow dwarf virus in autumn‐sown cereals are necessary in any year, are discussed.
Association of Phytophthora palmivora bark canker and insect damage in cocoa in Papua New Guinea
Authors: PRIOR C. , SMITH E. S. C.
Published: February 2008

Bark canker caused by the fungus Phytophthora palmivora has caused the death of many cocoa trees over 15 years old in Papua New Guinea in recent years. Cankers are significantly associated with channels made by the larvae of bark‐damaging insects, which provide the major entry point for the pathogen. The combination of canker and insect damage may limit the economic life of cocoa to less than 15 years in affected areas.
Forecasting barley mildew development in West Scotland
Authors: CHANNON A. G.
Published: February 2008

Observations on plots of spring barley cv. Golden Promise during May‐July 1973–79 showed that escalation of mildew commenced in mid‐June 1976, in late June in 1973 and 1974, in early July in 1978 and 1979, and failed to develop in 1975 and 1977. By mid‐July there was 40% infection in 1976, and 13–21% infection in 1973, 1974, 1978 and 1979. Less than 2% mildew occurred in 1975 and 1977.

Using as a basis the method of mildew forecasting formulated by Polley & King (1973), it was found that once mildew was established in the crop there was moderately good association between the incidence of high mildew risk according to the Polley weather criteria and the major peaks of spore concentration above the crops. It was not possible to correlate these two features during May and early June each year because of a lack of inoculum, but it is considered that the failure of mildew to develop during the entire growing seasons of 1975 and 1977, in spite of frequent high risk periods, was due in part to low atmospheric humidity during the early part of the season. The relative number of accumulated Polley factors satisfied on days when the relative humidity approx. 1 m above ground was 78% or more (at 0900 GMT) during the period mid‐May to mid‐June, separated the low mildew years of 1975 and 1977 from the moderate ones of 1973, 1974, 1978 and 1979, and the severe mildew year of 1976. This procedure may provide a practical means of forecasting the level of mildew build‐up during the later growth stages of the barley crop.
Resistance of cocoa to swollen‐shoot virus in Ghana. I. Field trials
Authors: LEGG J. T. , LOCKWOOD G.
Published: February 2008

In Ghana, field resistance to cocoa swollen‐shoot virus (CSSV) in young, bearing trees was assessed by monitoring natural spread by mealybug vectors from adjacent graft‐inoculated line sources. Apparent rates of virus spread were estimated by regressing proportions of infected trees on time from inoculation. In some hybrids between parents derived from Upper Amazonian material, spread was only 25–40% that in currently recommended varieties. This resistance is the most effective, feasible measure to reduce economic losses and the resistant hybrids could be made available quickly for large scale use.

The results from trials in which virus spread most rapidly were the easiest to interpret. Spread of CSSV is erratic, necessitating large experiments, and in trials with equal replication the largest plots gave the greatest precision. Neighbouring plot adjustment proved unsatisfactory as it improved precision but appeared to reduce accuracy.
Resistance of cocoa to swollen‐shoot virus in Ghana. II. Assessment of seed inoculation experiments
Authors: LOCKWOOD G.
Published: February 2008

Differences in amounts of infection following seed inoculation, by the mealybug vector (Planococcoides njalensis (Laing)) of cocoa swollen‐shoot virus were used as a short‐term test of virus resistance in a range of cocoa progenies. The test results were highly correlated with virus resistance as measured in field trials. The best assessment of seed inoculation experiments allowed for progeny‐dependent variation in the latent period of the virus. Experiments in which estimates of progeny means varied significantly with replicate sometimes gave poor agreement with known field performance.
The effect of cereal growth stage and feeding site on the reproductive activity of the bird‐cherry aphid, Rhopalosiphum padi
Authors: LEATHER S. R. , DIXON A. F. G.
Published: February 2008

Apterous Rhopalosiphum padi on the first leaf of cereal plants, developed faster and were more fecund at seedling to stem extension of barley, at tillering to earing of oats and at stem extension and earing of wheat. Feeding site on a mature plant also affected the rate of development and fecundity of the aphids; the largest and most fecund developed on the stems of oat and wheat plants. The consequences of these variations in reproductive performance are discussed in relation to the population dynamics of R. padi and its possible pest status in Britain.
The effect of iprodione on seed germination and seedling emergence in onion
Authors: ENTWISTLE A. R. , BROCKLEHURST P. A. , JONES T. G.
Published: February 2008

Iprodione seed treatment at 100 g a.i./kg seed had little effect on final emergence in peat‐based compost at 60% moisture content (wet weight basis) but caused up to 1.5 days' delay in the time to 50% of the final emergence (t50). The effect was independent of initial seed viability, the conditions and duration of seed storage after treatment and germination temperature. Raising the compost moisture content to 70% resulted in a 9% reduction in final emergence and a 3 day increase in t50.

Iprodione had a greater effect in a filter paper test, reducing final emergence by up to 24% and increasing t50; the effects were again independent of initial seed viability and storage conditions.
The reactions of some Brussels sprout F1 hybrids and inbreds to cauliflower mosaic and turnip mosaic viruses
Authors: TOMLINSON J. A. , WARD C. M.
Published: February 2008

Virus infection of Brussels sprout crops was widespread in Britain in 1974–76. Infected plants contained mostly cauliflower mosaic (CaMV) and turnip mosaic (TuMV) viruses but occasionally broccoli necrotic yellows virus (BNYV) was also found. The most seriously affected cultivar was the F1 hybrid cv. Fasolt. Other hybrids including cvs Achilles, Citadel and King Arthur were more tolerant of infection.

A key was developed for assessing the reactions of various F1 hybrids and their parent inbred lines to CaMV + TuMV. Tests showed that the mean symptom severity of hybrids was usually less than the mean symptom severity of the parent inbreds, indicating that resistance to infection is partially dominant.

The reactions of infected inbreds grown in winter under glasshouse conditions (15–18°C) were closely correlated with those of plants grown in the field. Thus, rapid selection of virus‐tolerant inbreds can be made under glasshouse conditions.
Responses of cow pea (Vigna unguiculata) varieties and their hybrids to variation in day and night temperature regimes
Authors: DOTO A. L. , WHITTINGTON W. J.
Published: February 2008

The effects of each of four contrasting combinations of two day (30, 26°C) and two night (24, 19°C) temperatures were studied on four cowpea varieties and their F1 hybrids. Early vegetative development was enhanced by the higher day, higher night temperature and flowering occurred first in plants receiving this treatment. The hybrids showed marked heterosis for leaf area but not for time to flowering. The ten genotypes studied showed correlated responses to increases in night temperature and differed in the degree of their response. The extent of the response (or stability) of varieties was often determined by the character values in the environment with the highest yield and heterotic hybrids were the least stable. Grain yield was highest in the lower day temperature environments but there was variation between genotypes in whether this occurred at the lower or higher night temperature. The pattern of responses shown by hybrids agreed with those of their parents indicating that stability was an inherited character. The results confirmed and extended those in earlier studies and emphasised the importance of a greater understanding of the nature of responses to the environment in selecting new varieties.
The cytokinin activities of 6‐α‐alkylbenzyloxypurines
Authors: WILCOX E. J. , SELBY C. , WAIN R. L.
Published: February 2008

The homologous series of 6‐α‐n‐alkylbenzyloxypurines with alkyl groups (—(CH2)nCH3) from n = 0 to n = 11 have been prepared and examined in three tests for cytokinin activity. The parent benzyloxypurine was also included in the tests.

Substituting methyl (n = 0) into the methylene group of 6‐benzyloxypurine removed activity almost completely; thereafter, increasing the size of the alkyl group (n = 1–5) gave compounds which were active in all tests, the butyl (n = 3) and pentyl (n = 4) derivatives being more active than 6‐benzyloxypurine itself. Activity then fell as the series was ascended; the higher homologues (n = 8–11) being completely inactive.

The results are discussed in relation to steric and other considerations.
Post‐harvest treatments for the control of Phytophthora syringae storage rot of apples
Authors: EDNEY K. L. , CHAMBERS D. A.
Published: February 2008

Oospores of Phytophthora syringae germinating at 10 and 15°C under artificial light formed one or more sporangia, which yielded zoospores. Furalaxyl and metalaxyl demonstrated eradicant action against infections occurring on zoospore‐inoculated apples. Control was obtained at 10°C when treatment was delayed 5–11 days after inoculation.

Storage in 5% CO2+ 3% O2 and 0% CO2+ 2% O2 reduced rotting compared with storage in air.
Decreased severity of potato common scab after foliar sprays of 3,5 ‐dichlorophenoxyacetic acid, a possible antipathogenic agent
Authors: MCINTOSH BY A. H. , BATEMAN G. L. , CHAMBERLAIN K. , DAWSON G. W. , BURRELL M. M.
Published: February 2008

Glasshouse tests on the potato cultivars Majestic and Maris Bard measured the effects of single early foliar sprays of ring‐substituted phenoxyacetic acids (0.9 × 10–3 M) on the incidence of potato common scab, caused by soil‐borne Streptomyces scabies.

The most effective compound was 3,5‐dichlorophenoxyacetic acid (3,5‐D), which decreased scab by about 90%; its action was preventative, early sprays being more effective than late However, it slightly decreased yield, and increased the number of tubers per plant and the proportion of deformed tubers. The trichloro‐ and tetrachloro‐ acids containing the 3,5‐dichloro‐ group also decreased scab, though to lesser extents; the most active of these was the 2,3,4,5‐tetrachloro‐ acid, which had the same side effects as 3,5‐D. The herbicide 2,4‐D almost halved scab incidence, but seriously decreased yield. Other acids tested had little or no effect on scab.

In tests against S. scabies in culture, 3,5‐D was no more toxic than other disubstituted acids which were inactive, or weakly active, against the disease in vivo.

3,5‐D may be an ‘antipathogenic agent’, preventing scab development by altering tuber metabolism.
Use of Clq enzyme‐linked immunosorbent assay to detect plant viruses and their serologically different strains
Authors: TORRANCE BY L.
Published: February 2008

Clq was prepared from bovine serum using a simple method involving repeated dialysis at low ionic strength in the presence of chelating agents (yield c. 3 mg/100 ml serum). It was viable when stored at ‐18°C for up to 2 months, and at 4°C for at least 10 wk in a storage buffer containing 10% sucrose. When used in Clq ELISA this test was as sensitive as the direct double antibody sandwich form of ELISA (direct ELISA) in detecting purified potato virus Y (PVY), with a limit of detection in both methods of c. 15 ng/ml, and slightly more sensitive in detecting purified cocksfoot mild mosaic virus (CMMV), with limits of detection of c. 15 ng/ml and c. 15–60 ng/ml respectively.

Using an antiserum to one strain of each virus, Clq ELISA readily detected strains of PVY, CMMV, Andean potato latent virus (APLV) and barley yellow dwarf virus (BYDV). This included detection of APLV‐Hu by APLV‐Caj antibodies and CMMV(G) by PMV(S) antibodies, neither of which system gives detection in direct ELISA. Clq ELISA was therefore less specific than direct ELISA in detecting serologically different virus strains.

Virus detection by Clq ELISA was inhibited when sap of tobacco, Nicotiana clevelandii and Setaria italica was used at low dilution. Inhibition by N. clevelandii sap was alleviated by using increased concentrations of virus specific antibody to detect APLV and plum pox virus. Also, extracting APLV infective N. clevelandii or CMMV infective S. italica saps in a minimum of buffer, centrifuging at low speed and diluting the supernatant before testing, partially overcame the inhibition. The inhibitory substance(s) in sap may act by preventing the binding of Clq to virus‐antibody aggregates. Sap of wheat, oat and barley did not appear to have an inhibitory effect and BYDV was readily detected in naturally infected field grown plants of these species.
Black tea manufacture.
Authors: CLOUGHLEY J. B. , ELLIS R. T. , HARRIS N.
Published: February 2008

Tea shoots were comminuted by four commercial processing systems representing both orthodox, and the more intensive, unconventional methods. Greater amounts of endogenous flavanols were oxidised and higher levels of the flavin class of pigments were produced, during the fermentation of the unconventionally processed leaf. Detailed comparison of quality and all the other aspects affecting market value, demonstrated that the unconventional systems produced a more valuable product. The results are related to the characteristic tissue damage associated with each disruption technique.
Control of pearl millet downy mildew by seed treatment with metalaxyl*
Authors: WILLIAMS R. J. , SINGH S. D.
Published: February 2008

Three formulations of the systemic fungicide metalaxyl were tested in various seed treatments for the control of pearl millet downy mildew in three field experiments with downy mildew‐susceptible pearl millet hybrid NHB‐3. Uniform, high levels of sporangial inoculum of the causal fungus, Sclerospora graminicola, were provided throughout the growth of the test crops from inoculated infector rows of NHB‐3, planted earlier between the test plots. Significant reductions in downy mildew were obtained with all fungicide treatments. Best control was obtained when seed was soaked in a 0.5% aqueous solution of a liquid formulation (mean infection index of 9.8% compared with 94.8% in the untreated check). The degree of control with the wettable powder formulations was directly related to fungicide dosage, and there were no significant effects of application method. Simple dusting of seed at 2 g a.i./kg, a rapid and simple operation requiring small quantities of fungicide and no special application equipment, gave a high level of control (infection index of 12.6% compared with 78.9% in the untreated check). In two experiments grain yields from all the treated plots were significantly greater than from the untreated plots (means of 1234 and 1534 kg/ha for treated plots compared with 485 and 743 kg/ha, respectively), and in the third, the treatment with the least downy mildew gave significantly more grain than the untreated check (1228 compared with 727 kg/ha).
Inhibition of development of Meloidogyne incognita by root and foliar applications of oxamyl
Authors: WRIGHT DENIS J. , WOMACK NICHOLAS
Published: February 2008

Oxamyl (2.5 μg cm‐3sand) applied to the roots of cucumber seedlings significantly reduced the number of vermiform second stage juveniles of Meloidogyne incognita which developed into swollen forms for at least 30 days. However, when cucumber seedlings containing nematodes were removed from oxamyl‐treated sand 10 days after the pesticide was applied and placed in clean sand a large proportion of the juveniles had become swollen after a further 18 days. This suggested the effect of oxamyl on nematode development was reversible.

A single foliar application of oxamyl (25–100 μg) in distilled water was also found to significantly reduce development of second stage juveniles to saccate forms However, the use of various adjuvants with a threshold foliar treatment (25 μg oxamyl) failed to significantly improve its activity.
A simple procedure for the efficient estimation of potato cyst nematode larvae in lactophenol‐treated roots
Authors: MARKS R. J. , McKENNA L. A.
Published: February 2008

Counts of potato cyst nematode larvae in whole roots of potatoes may be readily made by liberating the larvae from lactophenol treated roots into water using a blender, removing root debris by filtration and counting larvae directly in water. The method obviates the health hazard associated with high levels of phenolic fumes when counting intact root systems or pieces directly in lactophenol and is also considerably faster and more efficient.
The effect of cold storing pre‐germinated lettuce seeds on radicle development and seedling emergence
Authors: WURR D. C. E. , DARBY R. J. , FELLOWS JANE R.
Published: February 2008

The effects on radicle development and seedling emergence of cold storing batches of pre‐germinated lettuce seeds for up to 7 days at 0 or 2 °C were investigated in three experiments. Cold storage tended to delay emergence and increase its spread in time. Separate batches of pre‐germinated seeds gave different mean radicle lengths and different patterns of emergence and it is likely that small differences in mean temperature during germination were responsible since the length of radicles after germination was linearly related to accumulated day‐degrees during the germination period. This suggests that germinating seeds over a period during which a required number of day‐degrees is accumulated may produce radicles of the same length for different sowings.

The elongation of radicles during cold storage was also linearly related to accumulated day‐degrees. At 2 °C it appeared that the longer radicles elongated faster than the smaller ones and this may account for cold storage tending to increase the spread of seedling emergence when the pre‐germinated seeds were sown into compost.
Effects of cold storage of germinated vegetable seeds prior to fluid drilling on emergence and yield of field crops
Authors: FINCH‐SAVAGE W.
Published: February 2008

Germinated seeds of five vegetable crops were stored at 1 °C in aerated water or humid air for periods of up to 15 days and then fluid drilled in the field. Viability of germinated seed was maintained in carrot and parsnip for a minimum of 15 days, salad onion for 9 days, lettuce for 6 days and cabbage for 3 days. When salad onion, lettuce and cabbage seeds were stored for longer than these times there was a reduction in the number of seedlings emerging. In species where storing seeds for up to 15 days caused a reduction in emergence an adjustment to the seed rate related to the length of storage can be made to achieve the desired population and still retain the advantages of fluid drilling pre‐germinated seeds. This is possible because with one exception (an increase in the variation of salad onion stem diameters) the performance of plants from all stored germinated seeds after emergence was similar to plants from freshly germinated seeds.
Influence of environmental conditions on spore dispersal and infection by Septoria nodorum
Authors: JEGER M. J. , GRIFFITHS ELLIS , JONES D. GARETH
Published: February 2008

In field experiments using healthy trap plants it was found that pycniospores of S. nodorum were dispersed from diseased wheat plants whenever rain fell and occasionally in the absence of rain. Of two spring wheats tested, cv. Kolibri seemed a better ‘source’ plant and cv. Maris Butler a better ‘receptor’ when rainfall was light, but this difference was not apparent when rainfall was heavy.

On 44 occasions, plants of Kolibri and M. Butler were also exposed to natural conditions immediately following artificial inoculation with S. nodorum. Infection of plants occurred on 10 occasions and was associated with the following minimum conditions: r.h, at inoculation >63%; and in the following 24 h, minimum temperature <6°C, at least 4 h with r.h. >90% and not more than 4 h with r.h. >60%.
Disease measurement in a study of apple scab epidemics
Authors: JEGER M. J.
Published: February 2008

An epidemic of apple scab in an unsprayed planting at East Mailing was monitored during the summer of 1979. Different rates and patterns of scab development on six apple cultivars were observed. Of several disease measures investigated the number of colonies/extension shoot best represented the epidemic.

More comprehensive disease measurements on leaves, fruits and shoots were made toward the end of the summer. Cultivar differences were demonstrated for all disease measures investigated. The proportion of leaves with scab (incidence) and the number of colonies on leaves (intensity) were the measures with the lowest coefficients of variation. Consistent relationships between incidence and intensity were obtained.

The implications of these findings for studies concerned with fungicide evaluation, cultivar susceptibility, disease—quality loss relationships and monitoring for disease management are discussed.