bluuebunny/crossref_metadata_2025 huggingface dataset:
Host range, purification and some properties of two carlaviruses from hop (Humulus lupulus): hop latent and American hop latent
Authors: ADAMS A. N. , BARBARA D. J.
Published: February 2008

Hop latent virus (HLV) occurs in virtually all commercial hop plants in England, without causing apparent symptoms. It was transmitted between hop plants in a non‐persistent manner by the aphid Phorodon humuli, but was not seed‐borne in hop. The virus infected six species in four families out of 40 in 13 families which were inoculated, but infection was systemic only in Dianthus deltoides and hop. Only Phaseolus vulgaris and Chenopodium murale developed symptoms. Purification of HLV from hop extracts was hampered by aggregation of virus particles but this was minimised either by resuspending pellets in phosphate‐buffered saline containing Tween 20 or by avoiding ultra‐centrifugation. Virus was purified from extracts treated with Triton X‐100 by precipitation with polyethylene glycol (PEG) followed either by centrifugation through sucrose density gradients or by exclusion chromatography through columns of Sephadex G‐25 and Sepharose 4B. Purified preparations contained filamentous particles c. 675 × 14 nm composed of c. 6% single stranded RNA of mol. wt c. 2.9 × 106 and a single protein species of mol. wt c 33 000. Immunosorbent electron microscopy (IEM) decoration tests suggested that HLV was serologically related to carnation latent, Helenium virus S, lily symptomless and Nerine latent viruses.

American hop latent virus (AHLV) was found in two introductions to England from Corvallis, USA in 1975 and 1976. It was transmitted between hop plants in the non‐persistent manner by P. humuli. The virus infected 17 species in seven families out of 41 species in 13 families which were mechanically inoculated and was systemic in nine species. It did not cause symptoms in any of five English hop cultivars. C. quinoa was a convenient propagation host and countable local necrotic lesions and ringspots occurred in leaves of Datura stramonium. AHLV was purified by PEG precipitation and centrifugation in sucrose density gradients. Preparations contained filamentous particles c. 680 × 15 nm composed of c. 6% single‐stranded RNA of mol. wt c. 3.0 × 106 and a single protein species of mol. wt c. 33 000. In IEM decoration tests AHLV was serologically related to Nerine latent virus but did not react with antisera to 14 other carlaviruses.
The influence of form of deposit on the phytotoxicity of MCPA, paraquat and glyphosate applied as individual drops
Authors: MERRITT C. R.
Published: February 2008

MCPA, paraquat and glyphosate were applied as individual drops (200–400 μm) to pot‐grown plants of radish (Raphanus sativus) or wild oat (Avena fatua), using concentrations appropriate to very low volume applications of these herbicides. For a given dose per plant, herbicide activity was unaffected by concentration of MCPA or paraquat but was enhanced as the concentration of glyphosate was increased. The activity of all three herbicides on both species was affected by variation of the site of application but not by drop size. On radish the greatest activity resulted when paraquat was applied to the cotyledons, glyphosate to the interveinal areas of true leaves and MCPA to the veins of true leaves. This is discussed in relation to herbicide mobility and local toxicity following applications at high concentration.
Efficacy of benzimidazole and related fungicides against Rhizoctonia solani and R. bataticola
Authors: TANEJA M. , GROVER R. K.
Published: February 2008

Five formulations of four benzimidazole derived fungicides, carbendazim, benomyl, thiophanate methyl and methyl 4‐[2‐(2‐dimethylamino acetamide) phenyl]‐3‐thioallophanate were compared for their toxicity towards two pathogenic isolates of Rhizoctonia solani and three of R. bataticola. The isolates of two fungi showed significant differences in mycelial growth inhibition by the five fungicides. Benomyl and carbendazim were most inhibitory to all isolates of both fungi while the sesame isolate of R. bataticola was least sensitive to all fungicides.

Disease control (90%) was obtained with low concentrations of benomyl against root rot of cowpea caused by R. solani, and with thiophanate methyl against root rot of sesame and sunflower, and leaf blight of mung bean caused by R. bataticola. The spread of stalk‐end rot of sunflower heads was best checked with a spray of thiophanate methyl. The results suggest that benzimidazole fungicides having similar toxophores act differently for disease control in different host‐parasite combinations.
The effects of dazomet, fenaminosulf, and soil ridges on red core disease of strawberry
Authors: MONTGOMERIE ISABEL G. , KENNEDY DIANA M.
Published: February 2008

Fenaminosulf applied as a single soil drench soon after planting and growing plants on ridges 305 mm high decreased the incidence and severity of red core (Phytophthora fragariae). Pre‐plant treatment with dazomet and growing plants on raised rows 100 mm high were ineffective.

The % number of diseased roots was the most useful estimate of disease in evaluating the efficacy of treatments and the interaction of disease and yield. The relationship between disease and yield was highly significant, negative and apparently linear. Disease accounted for a higher proportion of the variation in yield in the first fruiting year than in the second. There was a close correlation between plant size in June and yield in July.
Susceptibility of different developmental stages of the root‐knot nematode, Meloidogyne incognita, to the nematicide oxamyl
Authors: WRIGHT DENIS J. , ROWLAND AMANDA J.
Published: February 2008

Oxamyl (6.25 μg ml‐1 soil water) was applied to cucumber roots containing Meloidogyne incognita at different stages of nematode development. Oxamyl was more effective in reducing the proportion of juveniles which developed into females when applied soon after infection to second stage juveniles than when applied later (to third and fourth stage juveniles). Early application of oxamyl also significantly reduced the proportion of females with egg masses, whereas late application had no such effect. However, the number of eggs per egg mass and the size of the young adult females was significantly reduced by all oxamyl treatments ‐ the earlier the application the greater the effect. These results support the hypothesis that actively feeding second stage juveniles of Meloidogyne spp. are more susceptible to systemic nematicides than are the non‐feeding third and fourth stage juveniles.
The effect of temperature and water stress on the timing of leaf death in Vicia faba
Authors: FINCH‐SAVAGE W. E. , ELSTON J.
Published: February 2008

The timing and pattern of leaf death was studied in three field experiments from observations of the area and dates of death of individual leaves. Two linear regression lines adequately described the pattern of leaf death on the plant in all experiments and treatments. These represented an initial phase with a slow rate of leaf death changing to a second phase with a more rapid rate of leaf death. The change from the first to second phase of leaf death occurred when the maximum seed dry weight was reached. The rates of both the first and second phases of leaf death increased with temperature. This was confirmed in an experiment in growth rooms. The rate of leaf death in both phases of plants grown at three constant temperatures increased linearly with temperature from 14 °C to 22 °C. The rate of leaf death in phase 2 increased with increasing solar irradiance and vapour pressure deficit. The rate of leaf death in both phases increased with increasing water stress in three irrigation treatments in the field.
Control of glasshouse whitefly, Trialeurodes vaporariorum, by an ‘aphid’ strain of the fungus Verticillium lecanii
Authors: KANAGARATNAM P. , HALL R. A. , BURGES H. D.
Published: February 2008

Heavy infestations of whitefly on glasshouse cucumber plants were controlled below the level of economic crop damage by fortnightly or monthly sprays of Verticillium lecanii spores. The fungus did not spread from glasshouse to glasshouse, or from plant to plant, and often not from diseased whitefly scales bearing fungal spore heads to nearby healthy scales. Some scales survived and the resulting adults laid eggs on new leaves bearing no infected scales, creating another, healthy, generation. This makes regular spraying of new leaves essential. Blastospores were as effective as conidia in controlling scales when sprayed to ‘run off’ at concentrations near 107 spores ml‐1 sprayed on to the undersurfaces of leaves. A fivefold increase in spore concentration at levels near 107 spores ml‐1 usually caused significant improvement in mortality, but increase above this concentration is likely to be unrewarding. Thorough coverage of leaves was found to be vital. Control was impaired by dry conditions and by prolonged air temperatures above 25 °C. The fungicide dimethirimol, used against cucumber mildew, did not impair whitefly control by V. lecanii.
Experiments on soil drenching with fungicides against take‐all in wheat
Authors: BATEMAN G. L. , NICHOLLS P. H.
Published: February 2008

In short term pot experiments benomyl, iprodione and KWG 0599 applied as soil drenches in several types of soil significantly suppressed take‐all symptoms from inoculum placed just below wheat seeds planted 1×5 cm deep, and in sand but not other soils when seeds were 5 cm deep. Benomyl was, however, effective against inoculum below seed planted 5 cm deep in a loam‐sand mixture when the drench contained an alcohol ethoxylate surfactant. Computer simulations of fungicide distributions in the soils correlated well with disease control observations.

In long term outdoor pot experiments two drenches with benomyl (without surfactant) controlled disease significantly for at least 3 months against inoculum placed 15 cm deep.

The significance of these results for the practical control of take‐all by fungicides is discussed.
Tests for transmission of four potato viruses through potato true seed
Authors: JONES R. A. C.
Published: February 2008

The Andean potato calico strain of tobacco ringspot virus (TRSV‐Ca) was detected in 2–9% of potato seedlings grown from true seed from plants of cv. Cara and clone G5998(6) infected with TRSV‐Ca. Similarly, a potato isolate of the oca strain of arracacha virus B (AVB‐O) was detected in 4–12% of progeny seedlings of cv. Cara and clone D42/8 infected with AVB‐O. Potato virus T (PVT) passed through 33–59% of seed from PVT‐infected cv. Cara, but only 0–2% infection was detected in seedlings from seed of PVT‐infected clone D42/8. By contrast, no infection was detected in seedlings grown from seed from plants of G5998(6), D42/8 or cv. Cara infected with Andean potato latent virus strains Hu (APLV‐Hu) or Caj (APLV‐Caj), although both strains passed through seed of Nicotiana clevelandii.

AVB‐O, PVT and TRSV‐Ca were detected in all tests of pollen from flowers of infected potato plants, but APLV‐Hu and APLV‐Caj were detected less frequently. AVB‐O and PVT were transmitted through 2% and 8% respectively, of seed from healthy potato plants pollinated with pollen from infected plants. However, no transmission through seed was detected when pollen from TRSV‐Ca infected plants was used. None of the four viruses were transmitted to healthy potato plants pollinated with pollen from infected plants.

APLV‐Hu caused exceptionally severe symptoms in the cv. Cara plants used for seed production, but the Bolivian strain of PVT induced only mild symptoms rather than the severe systemic necrosis previously reported for the type of strain of PVT in this cultivar. No symptoms developed in potato seedlings infected with TRSV‐Ca, AVB‐O or PVT through the seed.
Interaction between barley yellow dwarf virus and rust in wheat, barley and oats, and the effects on grain yield and quality
Authors: POTTER L. R.
Published: February 2008

In three separate experiments, the upper leaf surface of the fifth formed leaf of wheat cv. Highbury, the fourth and fifth leaves of barley cv. Julia and the third and fourth leaves of oat cv. Mostyn were inoculated in a spore settling tower with wheat brown rust (Puccinia recondita f. sp. tritici), barley brown rust (P. hordei) or oat crown rust (P. coronata f. sp. avenae), respectively. Fewer pustules developed on distal portions of leaves of plants infected with barley yellow dwarf virus (BYDV) than on similar portions of leaves from virus‐free plants. There were no significant differences in the number of pustules on proximal leaf portions. In barley and oats, the number of pustules on distal leaf portions was negatively correlated with the amount of yellowing of the leaf areas scored. In wheat, symptoms of BYDV were mild and leaves were little affected by yellowing. The latent period of rust on wheat and oats was not affected by BYDV. In barley, BYDV reduced the latent period of rust on leaf 5, but not on leaf 4, and reduced it on proximal, but not distal, leaf portions.

In other experiments, BYDV reduced the yield of wheat and oats by 44% and 66%, respectively, while BYDV‐infected barley was almost sterile. The appropriate rust reduced the yield of wheat, barley and oats by 33%, 13% and 86%, respectively. When infected with both BYDV and rust, yield of wheat and oats was reduced by 63% and 91%, respectively. Neither BYDV nor rust affected the percentage crude protein content of wheat grain, nor did rust affect that of barley. In oats, BYDV and rust each significantly increased crude protein of grain, but rust infection of BYDV‐infected plants tended to reduce it.
An investigation of the host range of the carrot fly
Authors: HARDMAN J. A. , ELLIS P. R.
Published: February 2008

The historical records of the earliest reports of umbelliferous and other hosts of carrot fly (Psila rosae) are presented and their validity discussed. In addition, the results are reported of tests made between 1972 and 1980 on 27 species of Umbelliferae and three sub‐species of Daucus carota to determine whether they would support the carrot fly. Techniques were developed for identifying plant species as hosts by determining the number of adult flies that emerged from root and soil samples obtained from plants exposed to carrot fly in the field. Experiments in 1979 and 1980 indicating the importance of co‐ordinating the life cycles of plant and insect. The results showed that certain annual species of Umbelliferae were unsuitable as hosts in the autumn when they has flowered and senesced. Valid records could only be obtained for these species by exposing the plants to first generation carrot fly attack. Of the 27 species tested, Anthriscus sylvestris, Ferula communis, and Smyrnium olusatrum failed to support carrot fly and the following 13 species were new host records: Aethusa cynapium, Anthriscus caucalis, Apium inundatum, Apium nodiflorum, Bupleurum tenuissimum, Chaerophyllum temulentum, Cicuta virosa, Daucus capillifolius, Daucus glochidiatus, Heracleum mantegazzianum, Ligusticum scoticum, Oenanthe crocata and Sison amomum. From two species, Chaerophyllum temulentum and Torilis japonica, more than two carrot flies/root were recovered. These species are numerous and widespread in carrot‐growing districts. The significance of these and other wild host plants in relation to the ecology and control of carrot fly is discussed.
Cereal aphids on maize in southern England
Authors: HAND S. C. , CARRILLO J. R.
Published: February 2008

In 1978, 1979 and 1980, counts were made of the numbers of cereal aphids on a maize crop near Fordingbridge, Hampshire, England. Maize plants were selected away from the edge of the crop and the number, morph, species and feeding site of the aphids were recorded. Metopolophium dirhodum and Rhopalosiphum padi were found at densities that exceeded those found on small‐grain cereals and grasses at the same time of the year. Sitobion avenae and Macrosiphum euphorbiae were found at relatively low densities, and Rhopalosiphum maidis and Metopolophium festucae were observed rarely. Unlike other species, the numbers of R. padi continued to increase throughout the summer and reached a peak in September/October; at this time of the year, R. padi constituted over 98% of the aphids found on maize. M. dirhodum and S. avenae were found mostly on the leaves whereas R. padi appeared to favour the cob until populations became too large to be supported. If the area of maize grown in the UK increases, the crop will probably play an important role in the life cycle of cereal aphids (especially R. padi). It is suggested that further work should be carried out on the pest status of aphids on maize and on the role that maize may play in the ecology of cereal pests.
Control of dark leaf spot (Alternaria brassicicola) of Brassica oleracea seed production crops with foliar sprays of iprodione
Authors: HUMPHERSON‐JONES F. M. , MAUDE R. B.
Published: February 2008

Three sprays of iprodione (Rovral 50% w. p.) at 0.5‐1 kg a. i./ha applied to Brassica oleracea seed crops in experimental plots and field trials at 3‐wk intervals from the young green pod stage until cutting controlled pod infection caused by A. brassicicola in seasons 1976–1979. As a result few seeds were infected, seed yields were increased and their germination was improved. Sprays of Bordeaux mixture were as effective as iprodione in years when disease levels were low but were ineffective when infection pressure was severe.
Detection of lettuce necrotic yellows virus by an enzyme‐linked immunosorbent assay in plant hosts and the insect vector
Authors: CHU P. W. G. , FRANCKI R. I. B.
Published: February 2008

An enzyme‐linked immunosorbent assay (ELISA) system for the rapid detection of the plant rhabdovirus, lettuce necrotic yellows virus (LNYV) in plant hosts and individual aphid vector is described. The method has been shown to be reliable and sensitive, and to have a number of advantages over the conventional methods of detecting LNYV in plants and insects by infectivity tests.
Observations on the population dynamics, life cycle and ecology of the plant parasitic nematode Rotylenchus robustus
Authors: BOAG B.
Published: February 2008

In a forest nursery growing Sitka spruce Rotylenchus robustus was most numerous at a soil depth of 10–19 cm, the vertical distribution being associated with that of the tree roots. Although no consistent seasonal fluctuations in nematode numbers were obvious there was a seasonal pattern in the relative frequency with which adult and larval nematodes were recovered.

Experimentally, the life cycle of R. robustus was completed in 14–18 months depending upon the time of year when nematodes were added to the trees. Soil moisture content of less than 8.7% (pF 3.8) restricted the movement of 50% of the population. The overall mean basal temperature for the completion of the life cycle of R. robustus was calculated to be 6.5°C.

Soil temperature was considered to be the dominant factor controlling the rate of development under field conditions in Scotland; only occasionally did soil moisture become limiting.
Production and dormancy of wild oat (Avena fatua) seed from plants grown under soil waterstress
Authors: PETERS N. C. B.
Published: February 2008

In 1974 wild oat plants grown from very dormant seed types fA, fB, fC originating from a single field, and in 1976 plants of type fB derived from another location were waterstressed from the time when the spikelets were just beginning to emerge until the seed was fully ripe. The seed production and dormancy of the seed were determined. Waterstress reduced the number of viable seeds per plant by 42% in 1974 and 49% in 1976. The number of viable seed produced on the tillers of the plants were reduced to a greater extent by waterstress than the number produced on their main stems. Some of the differences between the number of viable seeds produced by the three wild oat types were significant. In 1974, 78% of seed from stressed plants was dormant as compared with 90% of that from unstressed plants. Under a given soil moisture, the dormancy of the three types differed little, although seed dormancy was less in tiller seed than in main stem seed. In 1976 seed from stressed plants was 80% dormant, immediately after collection, whereas that from unstressed plants was totally dormant. Storage for 6 months at 25°C decreased these percentages to 17% and 90% and at 5°C to 72% and 98% respectively. Buried in soil immediately after collection, 66% of viable seed from stressed plants gave seedlings in the first autumn after burial as compared with 4% of seed from unstressed plants. Most of the seed from waterstressed plants gave rise to seedlings in the first autumn, and seed from non‐stressed plants in the second spring. The α‐amylase content was four times greater in seeds from stressed compared with non‐stressed plants.
A survey of cutworm attacks in England and Wales, and a descriptive population model for Agrotis segetum (Lepidoptera: Noctuidae)
Authors: BOWDEN J. , COCHRANE J. , EMMETT B. J. , MINALL T. E. , SHERLOCK P. L.
Published: February 2008

Surveys of larval populations and numbers of reports of damage showed that from 1945 to 1978 Agrotis segetum was the commonest species of cutworm, causing most damage, to a wide range of crops, from July to October. Attacks varied in extent and severity between years, the most severe damage occurring in 1949 and in 1976.

A model has been devised to estimate an index of larval survival to third instar, based on temperature‐rate of development relationships and mortality due to daily rainfall. This survival index is highly correlated with year‐to‐year changes in numbers of reported attacks by A. segetum. The model suggests that weather conditions alone were responsible for the last major cutworm outbreak in 1976.
The natural incidence of disease in the cutworm Agrotis segetum in England and Wales
Authors: SHERLOCK P. L.
Published: February 2008

Soil‐dwelling noctuids, mostly cutworm larvae were collected from various arable crops, from 39 sites in England and Wales between 1975 and 1978. They were individually reared in the laboratory, usually at 20 °C; 993 (79%) pupated and 859 (68%) emerged of which 819 (95%) were Agrotis segetum. Of those that died, 60 (4·8%) were infected, from a total of 25 sites; nuclear polyhedrosis, granulosis virus and a fungus of the family Entomophthoracae, probably Entomophthora megasperma, occurred in similar proportions. Disease incidence was low probably because natural concentrations of inocula were sparse. The possibility of controlling cutworms with their pathogens is discussed.
Infection of potato stems by the gangrene pathogen, Phoma exigua var. foveata
Authors: ADAMS M. J.
Published: February 2008

Limited transport of pycnidiospores of Phoma exigua var. foveata within transpiring stems was demonstrated by isolating from cut mature stems placed for 24 h in a spore suspension. Pieces of shoot dipped in spore suspension and subsequently rooted contained the pathogen which was redistributed as the plants grew but without causing symptoms until after desiccation. The fungus was only rarely detected within stems growing from rotted seed tubers suggesting that spore transport in the vascular system was relatively unimportant in these experiments.

Stems were readily infected from spore suspensions applied to unwounded epidermis especially when the inoculum was held in cotton wool and secured with wax film. The progressive colonisation of growing stems was demonstrated by isolations made at different positions on the stem and at different times after inoculation. In field experiments in two years stems were inoculated with four spore concentrations on four dates from late June to late August. After desiccation the extent of pycnidial lesions was greatest from the earliest inoculation date and the largest spore concentration and these differences were reflected subsequently in the incidence of gangrene on damaged progeny tubers. Younger stems may be more susceptible and infection in early summer probably results in extensive growth within the stem before desiccation and thus in massive pycnidial production.
Control of pearl millet downy mildew caused by Sclerospora graminicola with systemic fungicides in an artificially‐contaminated plot
Authors: DANG J. K. , THAKUR D. P. , GROVER R. K.
Published: February 2008

Among four fungicides, viz. metalaxyl (two formulations), fosetyl‐Al, pro‐pamocarb and cyomaxanil tested in vitro against sporangial germination inhibition of Sclerospora graminicola, cyomaxanil was found to be most inhibitory. In an artificially contaminated plot, when used as seed treatment or foliar spray for the control of downy mildew of pearl millet, only metalaxyl was effective.

Metalaxyl 25 (Ridomil) and metalaxyl 35 (Apron) seed treatments protected the pearl millet plants from downy mildew up to 30 days. As a foliar spray, metalaxyl 25 used once at 20 days or twice after 20 and 38 days of plant growth gave less disease at harvest time. Seed treatment (metalaxyl 25 or 35) followed by one metalaxyl 25 spray was found to be effective in controlling the downy mildew. These treatments improved the growth of plants and yield significantly.
Endosperm cell number in cultivars of barley differing in grain weight
Authors: COCHRANE M. P. , DUFFUS C. M.
Published: February 2008

The number of endosperm cells in caryopses 30 ‘days’ after anthesis was determined and a positive correlation was found between endosperm cell number and 1000 grain weight, and between endosperm cell number and dry grain volume in a number of cultivars of field‐grown barley. The genetic factors influencing grain weight are discussed in relation to these results and to observations made on transverse sections of immature caryopses.
Effects of deltamethrin on walking, flight and potato virus Y‐transmission by pyrethroid‐resistant Myzus persicae
Authors: RICE A. D. , GIBSON R. W. , STRIBLEY M. F.
Published: February 2008

In laboratory tests with moderately pyrethroid‐resistant (R1) Myzus persicae, more walked or flew from excised leaves pre‐treated with the pyrethroid deltamethrin, or its aqueous formulation ‘Decis’ at 10 mg a.i. litre‐1 than from untreated leaves. Neither a carbamate (pirimicarb) nor an organophosphate (demeton‐S‐methyl) induced flight. R1 alatae and apterae which had dispersed from deltamethrin‐treated leaves rarely transmitted potato virus Y (PVY); however transmission by the more pyrethroid‐resistant R2 alatae was only halved and that by R2 apterae undiminished. Treatment with deltamethrin decreased spread of PVY both in flight chamber and field experiments.
Disease spread of non‐specialised fungal pathogens from inoculated point sources in intraspecific mixed stands of cereal cultivars
Authors: JEGER M. J. , JONES D. GARETH , GRIFFITHS ELLIS
Published: February 2008

Spread of Septoria nodorum from inoculated point sources was examined in pure stands and mixtures of two spring wheat cultivars Kolibri and Maris Butler. Gradients in disease were observed soon after inoculation; the presence of the more resistant cultivar (Maris Butler) in the mixtures retarded the outward spread of disease compared with the susceptible pure stand (Kolibri). Regression analysis suggested that gradients in incidence were influenced by nearness to the source whereas gradients in severity were not.

Spread of disease was also examined in pure stands and mixtures for the host/pathogen combinations, winter wheat (cvs Maris Huntsman and Maris Ranger)/S. nodorum and winter barley (cvs Maris Otter and Hoppel)/Rhynchosporium secalis. In contrast to the spring wheat experiment, no gradients were observed; explanations for the uniform distribution of disease were (a) extensive spread prior to the period of assessment, (b) no physical barrier to dispersal due to the juvenile growth stage of the crop and (c) exhaustion of the point‐source.
Brown root rot of tomato, and its control, in Crete
Authors: MALATHRAKIS N. E. , KAPETANAKIS G. E. , LINARDAKIS D. C.
Published: February 2008

Symptoms similar to those regarded as typical of brown root rot disease have been noticed in tomato and eggplant in Crete. Infected plants showed symptoms only during the winter. Three fungi Pyrenochaeta lycopersici, Colletotrichum coccodes and Fusarium oxysporum were consistently isolated from infected tomato roots and proved to be pathogenic to young tomato seedlings. Pycnidia of P. lycopersici were produced when small pieces of infected young tomato roots were plated out on tomato juice agar (Oxoid) and incubated at 23 °C under continuous white light. Good control of the disease was achieved when soil was fumigated with dazomet 98% (70g/m2), methyl isothiocyanate (MIC) 20%+ dichloropropane‐dichloropropene mixture (DD) 80% (‐Di‐Trapex; 50 ml/m2), methyl bromide (75 g/m2), and vapam (200 ml/m2) + ethoprophos 10% (10 g/m2) or when solarisation was applied (soil covered by 50 μm transparent polyethylene sheet) during the whole period of August and September. Dazomet (30 g/m2) or ethoprophos 10% (10 g/m2) when combined with solarisation did not improve its effectiveness. MIC 20%+ DD 80% emulsified (Di‐Trapex e.c, 50 ml/m2) was ineffective.
Pathogenic variability of downy mildew (Sclerospora graminicola) on pearl millet. I. Host cultivar reactions to infection by different pathogen isolates
Authors: BALL SARAH L.
Published: February 2008

Cultivars of pearl millet were challenged by isolates of downy mildew collected from various locations in West Africa and India in order to ascertain whether variability in cultivar response was genetically or environmentally determined. Results of experiments, in Polythene tunnels which imitated tropical field conditions, were confirmed by more precise experiments in an isolation plant propagator. The most important conclusion was that variation is determined by host and pathogen genotypes. West African isolates of the pathogen were generally more pathogenic than Indian isolates. However, there were also substantial differences between two isolates collected from different host cultivars at the same location in Upper Volta. Cultivar ICH105 differentiated between West African and Indian isolates. Cultivars 700516 and MBH110 also showed differential responses between isolates. In contrast two distinct types of symptom expression were recorded and found to be characteristic of cultivar genotype, independent of pathogen isolate. The possibility that both race specific and race non‐specific resistance may coexist in this little understood pathosystem is discussed and the practical implications are considered.
Resistance of Botrytis cinerea to dicarboximide fungicides in protected crops
Authors: PANAYOTAKOU M. , MALATHRAKIS N. E.
Published: February 2008

Dicarboximide fungicides have been used for the control of grey mould in protected crops in Crete since 1977. During the 1980 growing season a decline of their efficacy was observed. In successive surveys carried out in May 1980, February 1981 and May 1981 in 28, 10 and 13 plastic houses repectively, a considerable proportion of resistant strains was found. From each of the plastic houses sampled mostly either only resistant or only sensitive strains were isolated. In three of the plastic houses with resistant strains there was an acute disease control problem. The ED50 of 15 resistant strains studied was in the area of 3·5 μg/ml vinclozolin as compared with 0·2 μg/ml for the wild type strains. The vinclozolin‐resistant strains were also resistant to procymidone, iprodione, and dicloran. In most of the cases strains resistant to vinclozolin were also resistant to benomyl and strains sensitive to vinclozolin were also sensitive to benomyl. In the absence of fungicide, resistant strains grew more slowly on PDA than sensitive ones, but spores germinated equally well. Vinclozolin (0·75 mg a.i./ml) did not protect eggplant seedlings against resistant strains but gave satisfactory control of sensitive ones.
The occurrence of Indian peanut clump, a soil‐borne virus disease of groundnuts (Arachis hypogaea) in India*
Authors: REDDY D. V. R. , RAJESHWARI R. , IIZUKA N. , LESEMANN D. E. , NOLT B. L. , GOTO T.
Published: February 2008

A disease characterised by severely stunted plants with small dark green leaves was found in groundnut (Arachis hypogaea) in sandy soils in Punjab State, India. The disease occurred in patches in the field and reappeared in the same positions in succeeding groundnut crops. Plants infected early did not produce mature pods. Seeds sown in soil collected from infected fields produced plants with typical disease symptoms. Phaseolus vulgaris cv. Local and Chenopodium quinoa were found to be good diagnostic hosts. The disease was shown to be caused by a rod‐shaped virus c. 24 nm in diameter with predominant particle lengths of c. 249 and 184 nm when stained in uranyl acetate. The virus, named Indian peanut clump virus (IPCV), resembled peanut clump virus (PCV) reported from W. Africa in symptomatology on groundnuts, particle morphology and soil‐borne nature. However, it is not serologically related to two W. African PCV isolates tested, or to tobacco rattle (PRN and CAM strains) or pea early browning virus (Dutch isolate) in microprecipitin, enzyme linked immunosorbent assay and immunosorbent electron microscopy tests.
Transmission of Spiroplasma citri by the aster leafhopper Macrosteles fascifrons (Homoptera: Cicadellidae)
Authors: O'HAYER KAREN W. , SCHULTZ GERALD A. , EASTMAN CATHERINE E. , FLETCHER JACQUELINE , GOODMAN ROBERT M.
Published: February 2008

The aster leafhopper (Macrosteles fascifrons), injected with an isolate of Spiroplasma citri obtained from brittle root‐diseased horseradish (Armoracia rusticana), transmitted the spiroplasma to horseradish and China aster (Callistephus chinensis.) After feeding on plants infected with S. citri, M. fascifrons transmitted the spiroplasma from aster to aster and horseradish, from yellow rocket (Barbarea vulgaris) to aster, and from turnip (Brassica rapa) to turnip. Symptoms in infected horseradish were chlorosis and stunting of newly formed leaves, discoloration of root phloem, and reduced plant growth typical of brittle root disease. Chlorosis, stunting, and asymmetry of young leaves occurred in affected aster and turnip. Flowers of infected aster were small and pale in colour and occasionally showed other symptoms including asymmetry, petal distortion, or light green petals. Spiroplasmas were isolated from all plants showing symptoms. Transmission rates by M. fascifrons which acquired S. citri by feeding on infected plants were very low, but injected leafhoppers transmitted more frequently. This is the first report of the transmission of S. citri from diseased to healthy plants by M. fascifrons.
A calcium‐binding sialoglycoprotein associated with an apparent eggshell membrane of Globodera rostochiensis
Authors: ATKINSON H. J. , TAYLOR JILL D.
Published: February 2008

Energy dispersive X‐ray microanalysis has been used to study the binding of two inhibitors of hatching in Globodera rostochiensis, ruthenium red and lanthanum, to a calcium binding site on the eggshell. Eggs were treated with either buffered ruthenium red or buffer only, and the levels of ruthenium and calcium that could be detected from the surface of eggshells were measured before and after repeated etching in a plasma oven. Counts for ruthenium increased during etching to a maximum after 8–12 min, just before the eggshell was eroded from the juvenile. The calcium levels on eggshells binding ruthenium red were suppressed relative to those from buffer. Similar experiments with lanthanum showed a significant increase in this inhibitor after 10 min etching and an accompanying suppression of calcium levels.

The nature of the binding site was probed by measuring ruthenium red binding after pretreatment with selected enzymes. A non‐specific protease, pronase, reduced the subsequent binding of this inhibitor but the site was resistant to trypsin in the presence of calcium. Neuraminidase also had an effect suggesting that the protein is a sialoglycoprotein. Phospholipase A2 but not Phospholipase C influenced the subsequent binding of ruthenium red. Phospholipase A2 caused a loss of hatching ability and the degradation of a phospholipid from the eggshell. Ruthenium red binding was also reduced by treatment of eggshells with detergents or sonication. Apparently a calcium‐binding sialoglycoprotein forms part of the integral proteins of an eggshell membrane located on the inner surface of the eggshell.
In vitro studies on activity and survival of Hirschmanniella spp. in some chemical solutions
Authors: BABATOLA J. O.
Published: February 2008

Activity and survival of three Hirschmanniella species were assessed in vitro in graded solutions of sodium chloride, urea, sucrose and artificial sea water. Both were adversely affected at high osmotic potentials. The electrolytes used in these studies appeared to impose an osmotic stress and a toxicity effect on the nematode, while in the organic compounds osmotic stress may be less important.
Differences in the tolerance of potato cultivars to potato cyst nematodes (Globodera rostochiensis and G. pallida) in field trials with and without nematicides
Authors: TRUDGILL D. L. , COTES L. M.
Published: February 2008

In field trials Cara, Brio, Maris Piper and Pentland Javelin were consistently more tolerant of damage by Globodera rostochiensis yielding more than Corsair, Pentland Dell, Maris Anchor and Maris Peer, in untreated, heavily infested soil and giving the smallest increases to nematicide treatment. No yield or growth differences were found between plants in untreated and nematicide treated plots at a nematode‐free site.

The most tolerant cultivars all had a gene (H1) for resistance to G. rostochiensis derived from Solanum tuberosum ssp. andigena and in soil infested with G. pallida the tolerance of at least one resistant cultivar (Maris Piper) appeared to be lessened. However, some resistant cultivars were comparatively intolerant, even to G. rostochiensis. Early cultivars were generally less tolerant than late maturing cultivars but there were exceptions. Amongst cultivars with resistance derived from Solanum vernei the early cultivar Guardian was more tolerant than the main crop cultivar Corsair.

The effect on the yield of several cultivars of a range of densities of G. rostochiensis, produced either by applying different rates of a nematicide or by cropping in the previous year, was examined at two sites. The results indicated that the slope of the regression for yield in relation to nematode density was less for tolerant than intolerant cultivars. At sites infested with G. rostochiensis Maris Piper was found to be consistently more tolerant than Pentland Crown.
A comparison of wheat bulb fly (Delia coarctata) egg numbers in ridge and furrow soil samples from potato crops
Authors: FRANKLIN M. F. , McKINLAY R. G.
Published: February 2008

In soil samples taken with a shovel from 97 potato maincrops in east Scotland during 1978 to 1981, wheat bulb fly (Delia coarctata) eggs were more numerous on ridges than in furrows. The ratio of the number of eggs on the ridge to the number of eggs in the furrow was higher in Lothian Region (3·25) than in Fife Region (1·59) but differed significantly (P < 0·05) from 1·0 in both Regions. To obtain maximum precision of the estimate of the total wheat bulb fly egg population in a potato field, more samples should be taken from the ridge than from the furrow, in approximate proportion to the egg numbers.
The infection process, sporulation and survival of Alternaria helianthi on sunflower
Authors: ALLEN S. J. , BROWN J. F. , KOCHMAN J. K.
Published: February 2008

Electron microscopy was used to study the infection of sunflower leaves by Alternaria helianthi. Conidia germinated by producing one to many germ tubes which grew across the leaf surface before forming appressoria. The fungus directly penetrated its host through the cuticle and epidermis. Entry into the host through wounds and stomates was also observed. Extracellular sheaths were found to be associated with germ tubes and intercellular hyphae of A. helianthi. Conidiophores developed through collapsed stomates, from leaf veins, trichomes and also from mycelium growing across the host leaf surface. Microcylic conidia were produced directly from parent conidia under certain conditions. Studies using a volumetric spore trap showed that the airborne spore concentration followed a distinct periodicity with peaks occurring between 0900 and 1100 h each day. Laboratory studies showed that safflower, noogoora burr and bathurst burr could serve as alternative hosts for A. helianthi. The pathogen was readily isolated from sunflower crop debris from a diseased crop that had been harvested 1 yr earlier.
Effects of fungicides and insecticides applied to spring barley sown on different dates in 1976‐79
Authors: JENKYN J. F. , PLUMB R. T.
Published: February 2008

Factorial experiments in 1976–1979 investigated the effects of sowing date, fungicides (ethirimol seed treatments and tridemorph sprays) and insecticides (phorate applied to the soil, and menazon or dimethoate sprays) on powdery mildew, aphids, barley yellow dwarf virus (BYDV) and grain yield of spring barley (cv. Julia in 1976 and 1977; cv. Wing in 1978 and 1979). Late sowing usually increased the severity of powdery mildew, numbers of aphids and incidence of BYDV and generally decreased yield. Responses to pesticides were commonly greater on the late‐sown than on the early‐sown barley. Response to fungicides are principally attributed to the control of powdery mildew (Erysiphe graminis f. sp. hordei; the target species) but responses to insecticides cannot be attributed to virus control and seem unlikely to be due solely to control of aphids, whose numbers were relatively small. There were some effects of fungicides on aphids and insecticides on mildew, but they were inconsistent and too small to affect crop protection strategies.
Studies on fast and slow growing Rhizobium spp. nodulating Cqjanus cajan and Cicer arietinum
Authors: BROMFIELD E. S. P. , RAO J. V. D. K. KUMAR
Published: February 2008

Fast and slow growing Rhizobium spp. isolated from Cajanus cajan and Cicer arietinum were compared in terms of colony characteristics, utilisation of carbon sources, acid production, symbiotic effectiveness and nodulating competitiveness.

Fast growing isolates from C. cajan and C. arietinum formed 3–6 mm diameter colonies on yeast‐extract mannitol agar after 4 days and were unlike the slow growers which produced colonies of c. 1 mm diameter after 7–10 days at 28 °C. The fast growing Rhizobium spp. from C. cajan utilised a wider range of carbon sources than the slow growing isolates from this host. Fast and slow growing strains from C. arietinum were able to utilise most of the carbon sources tested suggesting that the slow growers possessed glycolytic pathways similar to those in other fast growing species of Rhizobium. In culture, slow growing isolates from C. cajan produced a near‐neutral to alkaline reaction (pH 66·7‐5) whereas the fast growers from this host and both fast and slow growing isolates from C. arietinum produced an acidic reaction (pH 4·4–5·6). These data are discussed in the context of Norris' (1965) evolutionary concept of the Leguminosae. Under glassshouse conditions, fast and slow growing strains isolated from C. cajan and C. arietinum were equally effective on their respective hosts.

In competition with slow growing rhizobia, half of the fast growers formed more than 70% of the nodules on C. cajan grown in sand. In all but one instance similar results were obtained when plants were grown in soil. With C. arietinum grown in sand or soil, all fast growing isolates from this host formed more than 85% of the nodules in competition with slow growing strains.
An attachment to a tractor‐mounted seed‐spacing drill for applying granular formulations to small field‐plots
Authors: THOMPSON A. R. , PERCIVALL A. L. , EDMONDS G. H. , LICKORISH G. R.
Published: February 2008

Tractor mounted equipment is needed to deliver granular formulations of pesticides accurately to the soil in small‐plot trials in a manner comparable to commercial equipment. Inexpensive units incorporating a belt unit mechanism were designed and fitted to a Mk II Stanhay S‐870 Precision Seed‐Spacing Drill. The individual delivery belts were driven through a continuously‐variable reduction gearbox by the main drive shaft of the drill and pre‐weighed amounts of granules were placed along the belts. Insecticides and dose patterns could thereby be changed readily from plot to plot.

In field assessments of uniform doses of fuller's earth granules delivered to single row, 4·8 and 10·3 m plots, the mean weights recovered were 94–98% of the target doses, S.E.'s being ±2% of the means. When 16‐fold, exponentially‐increasing doses were delivered, the weights recovered were generally within 10% of the target dose at any point within 0·2 m from the start and 0·3 m from the finish of the plot. The performance of uniform doses of carbofuran (on sand) and chlorfenvinphos (on Spanish Silical) against cabbage root fly on radish in 15 m plots showed that errors in loading were insignificant compared with the variability in pest infestation on the field plots. With doses increasing exponentially by c. 12‐fold applied to similar plots, the percentage of carrots or radish undamaged by carrot fly and cabbage root fly increased from 40–60% to 85–99·3%, the relationship between the log‐log proportion of undamaged roots and log‐dose being linear.

The equipment allows free‐flowing, granular pesticide products to be applied to small plots of a wide range of row‐crops much more accurately than has hitherto been possible. A work rate of 24 plots h‐1 was achieved by a team of two technicians and a tractor driver.
The efficiency of visual assessment of grain yield and its components in spring barley rows
Authors: ISMAIL A. B. , VALENTINE J.
Published: February 2008

The efficiency of visual assessment for grain yield and its components in spring barley rows was examined using a number of assessors. In 20 out of 28 combinations of assessor and character, only 20 or less lines were needed to be retained from the set of 99 lines to save at least 50% of the best 10 lines. Assessments of tillers/row and to a lesser extent 1000‐grain weight were generally more effective than assessments of yield/row and grain/ear. The low effectiveness of assessment of grains/ear was attributed to inadequate sampling of ears. Four out of five assessors showed bias towards assessment of tillers/row, the most easily assessed character, in their assessments of yield/row.

Experienced barley workers were more successful in their assessments than others less familiar with the crop. Specially developed keys, aimed at making visual assessment more objective, generally had only small positive effects on the efficiency of assessment. Repeated assessments of characters by some assessors were consistent.

It was concluded that visual assessment rather than direct measurement should be recognised as a basic tool of breeding in the early generations, using a large number of lines as a ‘safety net’ allowing the loss of some of the best lines.
The efficiency of visual assessment for yield and its components in winter oat rows
Authors: VALENTINE J. , ISMAIL A. B.
Published: February 2008

The efficiency of visual assessment of grain yield and yield components in 0–75 m rows of winter oats was, in general, moderately high. Only eight or less lines were needed to be saved in six out of eight cases to retain at least 50% of the best four lines from the set of 40 lines. Assessments of yield/row and tillers/row were more effective than assessments of grains/panicle and 1000‐grain weight on the basis of the proportion of variation accounted for by regression of visual assessment on actual performance. An experienced oat breeder was more successful in his assessment than another assessor unfamiliar with the crop. Assessments of yield/row by the experienced assessor were apparently biased towards assessments of grains/row as the single most easily assessed character, while the assessor unfamiliar with the crop attempted to take tillers/row and 1000‐grain weight into account in his assessments. Implications to a winter oat breeding programme are indicated.