bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction between crown rust (Puccinia coronata) and two viruses of ryegrass
Authors: LATCH G. C. M. , POTTER L. R.
Published: February 2008

In Lemtal Italian and S.24 perennial ryegrass plants, two isolates of ryegrass mosaic virus (RMV) suppressed the amount of crown rust emerging on leaves inoculated with Puccinia coronata uredospores by up to 75% compared with the amount on virus‐free plants. Severity of rust infection on barley yellow dwarf virus (BYDV) infected plants generally did not differ significantly from that on virus‐free plants. When both RMV and BYDV were present, rust was restricted in Lemtal plants to a level intermediate between those occurring on plants infected by either virus alone, and in S.24 plants to a level below that obtained with either virus alone.

The mean water soluble carbohydrate (WSC) content of Lemtal plants was reduced more than 20% by RMV, but was not significantly altered by BYDV. In S.24 plants the WSC content was increased by 10% by RMV and by 60% by BYDV. Rust reduced the WSC content of healthy and virus‐infected plants, the reduction being positively correlated with the level of rust on the sampled leaves. In plants of Lemtal, but not of S.24, the degree of rust infection was positively correlated with the WSC content of leaves from rust‐free control plants.
Studies on host‐plant selection by the cowpea seed moth, Cydia ptychora
Authors: PERRIN R. M.
Published: February 2008

The Cowpea seed moth, Cydia ptychora, was able to complete its full life‐cycle on a wide range of tropical grain legumes. In glasshouse tests, the adult moth showed oviposition p references between grain legume species but not between cowpea varieties, although there were differences in larval damage to the seeds of the latter. On cowpea, most eggs were laid on 8–10‐day‐old pods and also in particular micro‐habitats; such behaviour was seemingly influenced by the mode of pod carriage.

The moth undergoes no known diapause during the dry season in southern Nigeria and cowpea plants in a suitable condition are infested throughout the year. Wild leguminous hosts were not identified during the present study.
Assessment of methods for testing varietal resistance to aphid s in cereals
Authors: DEWAR A. M.
Published: February 2008

The adult weight of three species of cereal aphids on barley was correlated with the number of large embryos and the total number of embryos within newly moulted adults. The relationships between embryo number and weight were constant for each species of aphid on all seven varieties of barley under identical conditions. The weights of aphids of each species on seven varieties of barley were significantly different from each other in each experiment. Pot size and plant age had a significant effect on the weights of Rhopalosiphum padi. The validity of these tests compared with previous methods is discussed.
Effects of C02 enrichment on the rates of photosynthesis and translocation of tomato leaves
Authors: HO L. C.
Published: February 2008

Effects of C02 enrichment on the rates of net photosynthesis (carbon fixation) and translocation (carbon transport) of tomato leaves were examined on a single mature leaf (seventh basal leaf) of plants grown initially under a light flux density of 40 W m‐2 with 350 (control) or 1000 vpm (enriched) CO2, and then exposed for 6 h to various light flux densities (7, 20, 40 and 130 W m‐2) or CO2 concentrations (350, 500, 700 and 1000 vpm).

When measurements were made in the conditions in which plants were grown, the rates of carbon fixation and carbon transport were 20 and 40% respectively higher in enriched plants than in the control ones. Under conditions different from the growing conditions, the rates of carbon transport in the enriched plants were generally higher than those of the controls with a similar rate of carbon fixation.

Leaves grown under a C02 enriched environment have a greater constant supply of mobile leaf assimilate than those under atmospheric C02. The higher efficiency of carbon transport in enriched plants was apparently retained even when the leaf was temporarily exposed to lower levels of light or CO2.
The identification of growth stages in winter wheat with reference to the application of growth‐regulator herbicides
Authors: TOTTMAN D. R.
Published: February 2008

The development of several varieties of winter wheat {Triticum aestivum) in early spring was studied in order to relate the progress of apical differentiation to easily measured external characters and so provide a guide to the correct timing of herbicide applications. Leaf sheath lengths were more closely related to apical development than were tiller or leaf numbers. Spikelet differentiation occurred when the longest sheaths were c. 5 cm tall. Application of a growth regulator herbicide before this stage of development caused ear deformities in the crop at harvest. A measure of leaf sheath length might, therefore, replace the ambiguous criteria presently used to judge the stages of winter wheat most tolerant of herbicides.
Control of potato cyst‐nematode, Globodera rostochiensis Rol, by picrolonic acid and potato trap crops
Authors: WHITEHEAD A. G.
Published: February 2008

Small, sprouted tubers of potatoes (cv. Pentland Crown) grown for 6 wk and then pulled out of soil infested with potato cyst‐nematode, Globodera rostochiensis Roi, increased the hatch of larvae, so that 100 days after planting the top 20 cm of the soil contained only one third of the original number of eggs. The artificial hatching agent picrolonic acid alone at 8‐6, 17*2 or 34‐4 kg/ha rotavated into the soil did not increase hatch but 17*2 kg, incorporated in the soil after potatoes grown for 4 wk, did.
Eradication of the perithecial stage of apple scab with surfactants
Authors: BURCHILL R. T. , SWAIT A. A. J.
Published: February 2008

Clone M3 apple leaves infected with scab (Venturia inaequalis) were dipped in one of a series of surface‐active compounds or mixtures tested at a concentration of 5% a.i. Seven of these reduced the concentration of scab ascopores released in the spring by more than 99%.
Multiplication and morphology of Spiroplasma citri in the leafhopper Euscelis plebejus
Authors: TOWNSEND R. , MARKHAM P. G. , PLASKITT KITTY A.
Published: February 2008

Spiroplasma citri multiplied in all Euscelis plebejus leaf hoppers injected and sometimes reached titres of over 1 × 107 colony forming units per insect. Spiroplasmas could be isolated from the haemolymph at all times although helices were only apparent for a few days after injection. The salivary glands of injected insects contained membrane bound pockets densely packed with mycoplasma‐like bodies. These bodies were frequently infected with virus‐like particles similar to those found in cultures of S. citri. Spiroplasmas had little effect on the longevity of the leafhoppers.
Methods for testing chemical additives to'prevent moulding of hay
Authors: LACEY J. , LORD K. A.
Published: February 2008

Three methods for testing additives for their ability to prevent moulding of hay are described. Storage of 25 g samples of hay in glass jars at 25 oC was useful for screening many chemicals rapidly. Dewar flasks (4–5 1) allowed testing on 500 g hay samples with sufficient insulation to allow any effects of chemicals on spontaneous heating as well as on moulding to be measured. Large drums containing 20 kg hay were used for larger scale tests with partially dried fresh, or rewetted old hay. Proprietary additives were unsuccessful at their recommended application rates and some even failed to show antifungal activity with very much larger doses. Volatile fatty acids, particularly propionic acid, and ammonium propionate were the most effective chemicals tested. The amount of propionic acid needed to prevent moulding and spontaneous heating could be defined in terms of the amount of water in the hay. Where the ratio of propionic acid to water was greater than 1–25:100 heating was rare. Ammonium propionate was slightly less effective than propionic acid against moulding. However, it lacks a pungent odour, is less volatile, less corrosive and is more pleasant and safer to handle.
Some hosts and properties of narcissus latent virus, a carlavirus commonly infecting narcissus and bulbous iris
Authors: BRUNT A. A.
Published: February 2008

Narcissus latent virus (NLV) is common in many cultivars of narcissus and bulbous iris, but was detected in only one of nineteen cultivars of nerine. It induced symptoms in some narcissus cultivars, but inconspicuous infection in bulbous iris and nerine.

NLV was not seed‐borne in narcissus or Nicotiana clevelandii but was transmitted readily by aphids (Acyrthosiphon pisum, Aphis gossypii and Myzus persicae) in the non‐persistent manner and by sap‐inoculation to twelve of fifty‐three species from three of sixteen families. Sap from N. clevelandii was infective after dilution to io‐3 but not io*, after 10 min at 65 but not 70 oC or after 3–4 days at 20 oC or 16–32 days at 2 oC.

Purified virus preparations were obtained from infected N. clevelandii by clarification of buffered leaf extracts with diethyl ether and carbon tetrachloride, followed by one or two cycles of differential centrifugation and molecular permeation chromatography. NLV has filamentous particles c. i3times65onm which sediment as a single component (io20, w= 156S). They contain c. 5% nucleic acid and a single polypeptide of mol. wt 32·6 × 103. The biological and physical properties of NLV place it in the carlavirus group; it is serologically related to lily symptomless virus, but not to fourteen other authentic carlaviruses. NLV has the cryptogram */*:*/(5):E/E:S/Ve/Ap.
Inactivation of cucumber mosaic virus in cultured tissues of Nicotiana rustica by diurnal alternating periods of high and low temperature
Authors: WALKEY D. G. A. , FREEMAN G. H.
Published: February 2008

Cucumber mosaic virus (CMV) was inactivated in infected tissue cultures of Nicotiana rustica after periods of alternating high (32–40 oC) and low (22 CC) temperature. An increase in the incubation period at high temperatures resulted in greater virus inactivation but more rapid deterioration of the tissue cultures. Optimal programmes for virus inactivation and culture survival were 40 oC (8 h) +22 oC (16 h) per day for 12 or 18 days, 40 oC (16 h) + 22 oC (8 h) per day for 12 days or 36 oC (20 h) + 22 oC (4 h) per day for 12 days.

Diurnal treatment periods of variable length and different high temperatures were related by using a concept of hour‐degrees above a base temperature. Taking this base temperature as 25 oC a linear relation was found between the logarithm of virus infectivity and the number of hour degrees.
The effect of ryegrass mosaic virus on carbon assimilation and growth of ryegrasses
Authors: JONES M. B. , HEARD A. J. , WOLEDGE JANE , LEAFE E. L. , PLUMB R. T.
Published: February 2008

The growth of simulated swards of Italian and perennial ryegrass, artificially infected with ryegrass mosaic virus (RMV) or RMV‐free, was investigated. During the build up of RMV infection, dry‐matter yield was usually decreased in infected swards, and the effect was confirmed when single vegetative regrowths of swards were investigated in detail.

The primary cause of lower yields in RMV‐infected swards appears to be a decrease in net canopy photosynthesis (maximum decrease about 50%) and an associated increase in dark respiration (maximum increase about 50%). The decrease in net canopy photosynthesis is due primarily to a lowered rate of net photosynthesis of constituent leaves within the canopy.

A secondary effect of RMV infection is to decrease tillering (maximum decrease about 30%) which results in a change in canopy structure and in particular a lower leaf area index. In the present experiments, lower light utilization by the swards is less important than the decrease in leaf photo‐synthetic efficiency in lowering yield.
Studies on plant growth‐regulating substances XLVIII. The effects of3,5‐diiodo‐4‐hydroxybenzoic acid on seedling growth in compact and loose soils
Authors: WILKINS HENRY , WILKINS SHEENA M. , WAIN R. L.
Published: February 2008

Investigations were carried out under growth room conditions to assess the effect on seedling growth of incorporating3,5‐diiodo‐4‐hydroxybenzoic acid (DIHB) in a silt loam soil.

In ‘compact soil’ (bulk density 1–5 g/cm3) at 20% moisture content, DIHB significantly increased elongation of the roots of Hordeum and Pisum seedlings, the optimum concentrations being 0–005 [ig and 0–005‐0‐507 fig DIHB/g dry soil respectively. Shoot height and root and shoot dry weights were also improved in barley seedlings. Treated pea seedlings had smaller root diameters 1 mm and 5 mm behind the apices and the roots were less bent than those of seedlings grown in soil in the absence of DIHB. The efficacy of DIHB treatment on pea seedling growth in compact soil decreased in soils at 24 and 28 % moisture contents.

In ‘loose soil’ (bulk density i‐i g/cm3) at 20% moisture content, DIHB significantly promoted the growth of barley seedlings but the only effects on pea seedlings were small changes in root diameter.
Response of squash to ethylene and chilling
Authors: OLORUNDA A. O. , LOONEY N. E.
Published: February 2008

Freshly harvested but already cured Acorn squash (Cucurbita pepo cv. Acorn) were stored for 4 wk in storage environments of20, 15, 10, 5 and o oC, with or without 5 μl 1‐1‐1 ethylene. Ethylene had no significant effect on overall acceptability, weight loss, dry matter, and ion leakage, but did enhance respiration at 15 and 20 oC. Temperature had a significant effect on weight loss, dry matter and overall acceptability. Squash stored at 15 and 20 oC had better flavour and texture than those stored at 0–10 oC, when cooked. Quality attributes such as flavour and texture may be more useful than physiological parameters in detecting insipient chilling injury in squash.
An investigation into the relations between some growth parameters and yield of barley
Authors: DYSON P. W.
Published: February 2008

Twenty‐five field experiments on barley were done at four sites from 1970 to 1975, with an additional site in 1975, comparing five rates of nitrogen application. The crops were sampled at c. 14‐day intervals from about the four‐leaf stage to maturity to follow changes with time in the dry weights of the constituent plant parts and to measure fertile tiller number, grain number per ear and grain weight. Some data have been selected from this body of information and regression analysis has been used to assess the possible importance of pre‐ and post‐anthesis growth in determining the yield of barley. Ear emergence was taken as an approximate indicator of anthesis. Yield was closely related (r=+0–96) and almost equal to the amount of dry matter accumulated before ear emergence for twenty‐one of the experiments, with a regression coefficient of 0–95. In two of the remaining experiments the regression coefficient was greater, 1–14; and smaller in the other two, o‐8i. Plant population is also shown to affect the regression coefficient. Despite these anomalies grain yield was more closely related to plant dry weight at ear emergence than to the increase in weight after ear emergence (r =+0–79). The increase in plant dry weight after ear emergence was frequently less than the yield of grain, suggesting that the plant can compensate for inadequate photosynthesis during grain filling. The result of this compensation is a reduction in straw dry weight. This implies that previously assimilated dry matter is transported to the grain, or that respiratory losses from the straw are not replaced by current photosynthesis. These observations suggest that yield may be limited by sink capacity rather than by photosynthesis after ear emergence. The main component of sink capacity, grain number per m2 was closely related to yield (r =+0–95) and is known to be determined at or before anthesis. Grain size was shown to be related to grain number per ear (r= 4‐ 0–99), suggesting that grain size is also, at least partially, determined at ear emergence. Therefore, all the yield components are determined, wholly or partly before ear emergence.
Factors affecting the seasonal distribution of red deer (Cervus elaphus) at Glen Dye, north‐east Scotland
Authors: STAINES BRIAN W.
Published: February 2008

Part of a red deer herd found on an estate in north‐east Scotland in summer spent more time on neighbouring ground during the winter where they damaged farms and woods. Factors associated with the deer's seasonal distribution were studied to help understand how to keep more deer on the estate in winter. There were no indications that food species or food quality were responsible for the observed changes in deer distribution, or that other animals or disturbance influenced distribution over a long period. Deer sought shelter from chilling winds, and areas occupied by deer in winter had more sheltered ground from wind, and the quality of this shelter was higher than on the areas little used. Home‐range behaviour and tradition appeared to determine which areas particular deer occupied in winter. The main recommendation for management was to re‐open mature woodland to provide more and better shelter on the estate in order to get more control over the deer stock and to reduce marauding.
Observations on the life cycle and pathogenicity of Paralongidorus maximus in a forest nursery in Scotland
Authors: BOAG B. , RASCHKE I. E. , BROWN D. J. F.
Published: February 2008

Soil samples from a forest nursery growing Scots pine were collected at monthly intervals at five different depths during 1975 and examined for Paralongidorus maximus: 49% occurred at the 10–19 cm depth. The fluctuation in the numbers of the larval stages suggested that a complete life cycle from egg to adult probably took more than 1 yr.

Growth in the second year after planting and overall height of Scots pine seedlings was inversely related to the numbers of P. maximus. In a glasshouse experiment using varying numbers of P. maximus the growth of Scots pine and European larch but not of Sitka spruce were decreased by increasing numbers of nematodes. A possible relationship between P. maximus, Cylindro‐carpon destructans and the death of small numbers of Scots pine is discussed.
Virus‐like particles in phloem tissue of chervil (Anthriscus cerefolium) infected with anthriscus yellows virus
Authors: MURANT A. F. , ROBERTS I. M.
Published: February 2008

Clusters of isometric virus‐like particles c. 22 nm in diameter, embedded in amorphous electron‐dense material, were found in the phloem tissue of Anthriscus cerefolium (chervil) plants infected with the semi‐persistent aphid‐borne virus, anthriscus yellows (AYV). The particles resembled those seen previously in thin sections of AYV‐transmitting aphids (Cavariella aegopodii). The particles were found only in the central vascular bundle of the petiole and its continuation in the leaf midrib. They were also found in extracts made by grinding petiole and midrib tissue in 10 % sucrose using Carborundum. These results confirm earlier studies which suggest that AYV is confined to deeper‐lying tissues.
Use of oviposition trays to estimate numbers of wheat bulb fly Leptohylemyia coarctata eggs
Authors: OAKLEY J. N. , UNCLES J. J.
Published: February 2008

To obtain reliable estimates of wheat bulb fly populations in time to provide advice on seed treatment of the following crop a method of collecting eggs in trays of soil placed in fields has been devised. The trays are examined by 20 August when half of the eggs have been laid.
Effects of photoperiod on some vegetable species
Authors: SOFFE R. W. , LENTON J. R. , MILFORD G. F. J.
Published: February 2008

Seven vegetable species grown in controlled environments were given similar daily amounts of visible radiation (500 J cm‐2) during three different photoperiod treatments. Plants were given (A) 12 h of visible irradiance (115 W m‐2) from fluorescent and tungsten lamps, (B) 16 h of the same light at 88 W m‐2 or (C) Treatment A extended to 16 h with 4 h of low‐intensity incandescent light (3 W m˜2) from tungsten lamps only. All seven species grew faster when daylength was extended with light of photosynthetic intensity (B), probably through increased net assimilation rates, and leaf area of these plants increased in proportion to change in plant dry weight. Daylength extension with a mixture of red and far‐red light (C) induced photomorphogenic changes in specific leaf area in all species examined and increased leaf area and plant dry weight of lettuce, celery, beetroot and spinach beet but not of three members of the Cruciferae (radish, cabbage and oilseed rape).
Cane blight (Leptosphaeria coniothyrium) in mechanically harvested red raspberry (Rubus idaeus)
Authors: WILLIAMSON B. , HARGREAVES A. J.
Published: February 2008

Leptosphaeria coniothyrium, the cane blight pathogen, was the fungus most commonly isolated from vascular lesions developing from mechanical harvester wounds on first‐year red raspberry canes. When inoculated to scalpel wounds, it induced similar lesions which were later associated with bud failure and cane death as were infected wounds on machine damaged canes. Cane resistance increased from May until August, inoculations later than July inducing only small lesions and rarely causing bud failure.
The occurrence of benomyl tolerance in Penicillium spp., Botrytis cinerea and a Gliocladium sp. on virus‐tested narcissus twin‐scales
Authors: LYON G. D.
Published: February 2008

All isolates of PeniciUium simplicissimum, P. verrucosum var. cyclopium, P. brevicompactum, P. multicolor, P. oxalicum, P. paxilli, Botrytis cinerea, and of a Gliocladium sp. obtained from necrotic virus‐tested narcissus twin‐scales previously dtoped in benomyl were tolerant to 1000 μg/ml of this fungicide in agar. Every necrotic twin‐scale examined was infected with at least one of these species. The first two species were the most frequently isolated and a similar range of species infected different narcissus clones or different cultivars. It is argued that the use of benomyl during the twin‐scaling programme should be discontinued as soon as a suitable alternative fungicide is found.
Control of Aphelenchoides composticola in mushroom compost with nematicides
Authors: MCLEOD R. W. , KHAIR G. T.
Published: February 2008

Mushroom compost was treated with nematicides and infested with Aphelenchoides composticola at the time of filling into growing containers. Yields of mushrooms from infested untreated control composts were reduced to 40–60% of yields from uninfested control compost. Yields from infested compost treated with fenamiphos emulsifiable concentrate (e.c.) at 10 or 20 mg a.i./kg, thiabendazole wettable powder at 40 or 60 mg a.i./kg or oxamyl granules at 20 mg a.i./kg were as high as from uninfested controls. Compost treated with granules of AC 64,475 up to 20 mg a.i./kg or ethoprophos or thionazin up to 80 mg a.i./kg gave yields significantly lower than uninfested controls.

Numbers of nematodes rose to about 106/20 g of compost in untreated compost and then fell, and a similar peak occurred in treatments in which yields were substantially reduced by nematode damage. Treatments which yielded as well as the uninfested controls held maximum nematode numbers down to about 10V20 g of compost but populations stayed at this level or tended to rise while numbers in untreated compost fell. Incorporation of fenamiphos in casing or its application to the surface of beds 3 wk after cropping began gave lower yields than the uninfested control but mushrooms were being produced late in the cropping cycle.

Fenamiphos e.c. at 20 mg ai./kg incorporated in compost is considered a practical preventive measure for control of A. composticola.
Symptomatologically distinct strains of pepper veinal mottle virus from four West African solanaceous crops
Authors: BRUNT A. A. , KENTEN R. H. , PHILLIPS SUE
Published: February 2008

Severe diseases of pepper (Capsicum annuum), tomato (Lycopersicon esculentum), eggplant (Solanum melongena) and tomato eggplant (Solanum integrifolium) in West Africa were induced by pepper veinal mottle virus (PVMV). Five selected virus isolates were serologically similar and readily transmissible by aphids in the non‐persistent manner, but they differed in host range and/or symptoms induced in some susceptible species. One isolate from eggplant failed to infect pepper, Chenopodium quinoa and C. amaranticolor, and induced only local infections in tomato. An isolate from tomato failed to infect eggplant, and an isolate from tomato eggplant induced severe stunting in Physalis floridana. The type strain, like the isolate from tomato, failed to infect Nicotiana tabacum systemically, but each caused severe systemic leaf and stem necrosis in tomato. None of the isolates infected S. melongena cv. Long Purple, suggesting that PVMV might be controlled in this and perhaps other crop species by the use of immune or tolerant cultivars.

All five isolates were serologically related to potato virus Y and some to six of 12 other potyviruses.
Incidence, and effects on yield, of virus diseases of taro (Colocasia esculenta) in the Solomon Islands
Authors: GOLLIFER D. E. , JACKSON G. V. H. , DABEK A. J. , PLUMB R. T.
Published: February 2008

Two virus diseases, alomae and bobone, both of which are spread by the planthopper Tarophagus proserpina affect taro (Colocasia esculenta) on Malaita, Solomon Islands. Where the diseases were endemic, plants of 284 of 297 cultivars died from alomae infection; the remaining 13 showed bobone symptoms on three to five leaves and then recovered, but symptoms later recurred on 12–13% of plants. Loss of yield due to alomae infection was directly proportional to the percentage of plants infected. Losses due to bobone of c. 25% could not be reliably detected unless insect pests were controlled. Frequent sprays with 0–1% malathion had no appreciable effect on the incidence of alomae, but fewer plants (30%) were infected when planted in November or December than when planted in May, June or August (64–94%).

Because new taro crops are traditionally grown close to infected crops, insecticidal control of the vectors will probably be of limited use in decreasing spread of the diseases.
Effect of virus yellows on yield of some monogerm cultivars of sugar beet
Authors: HEATHCOTE G. D.
Published: February 2008

The yield of plants of monogerm cultivars of sugar beet artificially infected with both beet yellows and beet mild yellowing viruses was, on average, depressed 2–7% for every 100 ‘infected plant weeks’, equivalent to c. £25/ha at 1976 prices. The cv. Vytomo, previously recommended to growers as being tolerant of infection by virus yellows, had a high sugar content and abundant foliage but in field trials its actual yield of sugar was no greater when infected, and lower when virus‐free, than that of some other monogerm cultivars.
Degradabflity and phenolic components of cell walls of wheat in relation to susceptibility to Puccinia striiforntis
Authors: HARTLEY R. D. , HARRIS P. J. , RUSSELL G. E.
Published: February 2008

Cell walls of tips and bases of laminae of flag leaves from 11 cultivars of winter wheat of varying susceptibility to Puccinia striiforntis yellow rust) were compared by examining their phenolic components released by treatment with a commercial cellulase. Isolated cell walls of both susceptible and resistant cultivars released water‐soluble carbohydrate esters of phenolic acids, the major acid detected being trans‐ferulic. There was no relationship between the amount of phenolic esters released by cellulase and susceptibility to yellow rust.

The leaf lamina tips, which were much more susceptible to yellow rust than the corresponding bases, had lower cell wall contents than the bases and their walls were more degradable by cellulase. Examination of transverse sections of leaf laminae of cv. Little Joss showed that cells whose walls contained phenolic groups that gave a red colour reaction with p‐nitrobenzene diazonium tetrafluoroborate, occupied a larger area of leaf lamina bases than of the tips. A greater percentage of the abaxial epidermal cells of the bases, compared with the tips, had walls that gave this red colour reaction. We suggest that the presence of phenolic groups in these walls may be related to the greater resistance of the bases to P. striiforntis.
Preliminary studies of carrot susceptibility to carrot fly attack
Authors: ELLIS P. R. , WHEATLEY G. A. , HARDMAN J. A.
Published: February 2008

Eleven carrot cultivars were tested to compare their susceptibility to carrot fly attack at Wellesbourne and at Mepal, Cambridgeshire in 1969. Significant differences in the percentages of unattacked roots were observed but not all the cultivars behaved consistently in this respect at the two sites. Foliage height and the percentage unattacked roots were not significantly correlated for these cultivars.

Four of the cultivars representing the different levels of susceptibility were retested in fen and in mineral soil in microplots at Wellesbourne in 1970. Soil type significantly affected plant growth but not the relative susceptibilities of the cultivars to carrot fly attack. Plant size was positively correlated with insect attack and accounted for most, but not all, of the differences in susceptibility between the cultivars. In 1971 also, cv. Royal Chantenay was significantly less attacked than Speed's Norfolk Giant from August to December even after allowing for the large differences between the two cultivars in plant size.

The experiments demonstrated a consistent difference in the relative susceptibilities of cvs Royal Chantenay and Speed's Norfolk Giant. The difference was correlated with plant size but allowances for foliage and root size failed to account for all of the difference. The results suggested a more fundamental basis for part of the difference in the susceptibility of the cultivars to carrot fly attack.
Specialisation of crown rust on highly and moderately resistant plants of perennial ryegrass
Authors: WILKINS P. W.
Published: February 2008

From two field samples of crown rust, isolates were selected for increased aggressiveness on four of 10 resistant perennial ryegrass clonal lines. Two lines which were formerly highly resistant became highly susceptible to the selected isolates but two which were formerly moderately resistant became only moderately susceptible. Thus, moderate resistance, although no less likely to be race‐specific, was more stable than a high level of resistance.

Cultures from highly resistant lines did not show increased aggressiveness on the varieties from which the resistant lines had been selected; hence individual genes of major effect were unimportant in determining varietal resistance. In contrast, cultures from moderately resistant lines were substantially more aggressive on their corresponding varieties. Three varieties contained many genes which tended to buffer changes in virulence of the rust.
The effect of sowing pre‐germinated seeds of lettuce (Lactuca sativa) on seedling emergence
Authors: GRAY D.
Published: February 2008

Glasshouse and field experiments were conducted to investigate the effects of sowing both untreated and pre‐germinated seeds, with or without a gel carrier, and also pelleted seeds into soils of different moisture contents and at different temperatures on seedling emergence of lettuce cvs Cobham Green and Avondefiance.

Pre‐germinated seeds with radicles 1–2 mm long gave, on average, 15 and 4% higher final percentage emergence than untreated and pelleted seeds respectively. Sowing pre‐germinated seeds having radicles longer than 2 mm gave more variable levels of emergence and often reduced emergence, particularly when they were sown into dry or drying seedbeds. Increasing the rate of gel carrier from 0 to 30 ml m_1 of row reduced emergence progressively from 67 to 30%. Pre‐germinated seeds emerged 2–5 and 3‐0 days earlier than untreated and pelleted seeds, respectively, at a soil temperature of 10 oC; at 15 oC the corresponding figures were 0–5 and 3–5 days. Sowing pre‐germinated seeds reduced the spread (i.e. variability) of emergence by an average of 37 and 47% compared with untreated and pelleted seeds, respectively.
The effect of transfer from low to high temperatures on losses of stored bulb onions (Allium cepa)
Authors: STOW J. R. , WARD C. M.
Published: February 2008

The effect of transferring onion bulbs from low to high temperatures during storage was investigated. It was found that the later transfer was made the lower was the weight loss per bulb but the greater the loss from sprouting. The lowest total loss observed was 37% by May following transfer in January.
An analysis of some effects of light and soil temperature on clubroot disease
Authors: BUCZACKI S. T. , OCKENDON J. G. , FREEMAN G. H.
Published: February 2008

In a glasshouse study, 54 batches of cabbage seedlings were each grown for 6 wk in clubroot inoculated soil. The batches were sown at weekly intervals during the experiment which lasted 60 wk. Soil temperature and light were monitored throughout the study while other potential variables were maintained as constant as possible. Records of clubroot incidence, severity and plant weights were kept and causal relationships for disease severity and percentage infected plants sought among the light and temperature data by regressions. It was found that clubroot severity was influenced most by the light level in the second and third weeks, while the percentage of diseased plants was most influenced by temperature, that in the second week probably being the most important. The optimum light value in the second and third weeks for expression of maximum clubroot severity was c. 600 Wh m‐2 day‐1 and a mean daily temperature of not less than c. 19‐5 oC was required to give close to 100% infection. Possible reasons for the findings are discussed.
Candidate insecticides for the control of larvae of Mamestra brassicae (Lepidoptera) (Noctuidae)
Authors: LEDIEU M. S.
Published: February 2008

Fifteen insecticides were tested in the laboratory against larvae of Mamestra brassicae, a chrysanthemum pest. Seven of these, methomyl, chlorpyrifos, leptophos, iodofenphos, methamidophos, mephosfolan and fenitrothion were significantly more potent than carbaryl, the standard adopted.

The performance of the insecticides is discussed in relation to selective action against insects and to mammalian toxicity, to identify those which might be suitable for integrated control or chemical control of noctuid larvae under glass.

A technique for monitoring the amount of pesticide deposited on to a target by a Potter Tower sprayer is described.
Pre‐flowering and post‐flowering insecticide applications to control Aphis fabae on field beans: their biological and economic effectiveness
Authors: BARDNER R. , FLETCHER K. E. , STEVENSON J. H.
Published: February 2008

Most spring‐sown field beans are treated with insecticides to control Aphis fabae, but there is usually a risk of toxicity to pollinating honeybees if insecticides are applied during flowering. An experiment was repeated at Rothamsted for 6 consecutive years, comparing treatments before and after flowering.

It is concluded that (1) pre‐flowering treatments (demeton‐S‐methyl spray at 0–25 kg a.i. ha‐1 or phorate granules at 1–12 kg a.i. ha‐1) were more effective and profitable than post‐flowering treatments, (2) application of phorate granules before flowering gave the greatest economic return, and minimised the danger to foraging bees and (3) aphid populations varied considerably from year to year, as did the relationship between aphid infestation and yield, but our evidence supports the suggestion that insecticide spray treatments are profitable if 5% or more of the plant stems are infested at the end of primary aphid migration.
The mildew resistance of Hordeum bulbosum and its transference into H. vulgare genotypes
Authors: JONES I. T. , PICKERING R. A.
Published: February 2008

Mildew from susceptible genotypes (SI and S2) of Hordeum bulbosum was found to be avirulent on all H. vulgare genotypes tested, including such cultivars as Proctor with no known genes for resistance to mildew.

The H. bulbosum genotype SI (2n =14) proved resistant to all isolates of mildew from H. vulgare. The mildew isolates used for these tests possessed most of the common virulence factors which attack the current ‘vulgare’ cultivars in Western Europe.

Some H. bulbosum genotypes were resistant to the ‘bulbosum’ mildew. Attempts at combining resistance from both species are presented and discussed.
Studies on plant growth‐regulating substances. XLIX. Phenoxyalkenes
Authors: RIUS‐ALONSO C. , WAIN R. L.
Published: February 2008

A series of phenoxyalkenes has been examined in a number of tests for plant growth‐regulating and selective herbicidal properties. Some of these compounds were found to possess high activity. The results are discussed in terms of chemical structure/biological activity relationships and mode of action.
Effect of sodium fertiliser on water status and yield of sugar beet
Authors: DURRANT M. J. , DRAYCOTT A. P. , MILFORD G. F. J.
Published: February 2008

Effects of sodium fertiliser on growth, water status and yield of sugar beet crops were measured in 1974 and 1975. Sodium increased leaf area index early in the growing period, the water content of the leaves and the final yields of root dry matter and sugar in both years. In 1974, it increased leaf relative water content and diffusive conductance under conditions of moderate soil moisture deficit in August but had no effect in June or September when soil moisture deficits were low. There was also no effect in June 1975 but later, when there was a severe drought, sodium decreased leaf water potential. Further evidence of an interaction between sodium and soil moisture on leaf water status was obtained from a reappraisal of results of field experiments made between 1965 and 1976. Sodium increased sugar yield through at least two different physiological mechanisms; it improved interception of radiation by the crop by increasing leaf area early in the season and it improved the efficiency of leaves under conditions of moderate water stress.
Breeding bird communities on Scottish farms
Authors: Batten L. A. , Cousins S.
Published: February 2008

The Common Birds Census, begun by the British Trust for Ornithology has now been monitoring bird population levels on a nationwide basis since 1962. Separate indices were constructed for Scotland and the rest of Great Britain for 12 of the commonest species.

Of the species examined blue tit (Parus caeruleus), wren (Troglodytes troglodytes), song thrush (Turdus philomelos), lapwing (Vanellus vanellus), chaffinch (Fringilla coelebs) and skylark (Alauda arvensis) have increased since 1963 and show very similar population trends to the rest of Great Britain. Whitethroat (Sylvia communis), willow warbler (Phylloscopus trochilus) and swallow (Hirundo rustica) have all declined nationally, the decline in the swallow appears to have begun earlier in Scotland. The blackbird (Turdus merula) and dunnock (Prunella modularis) showed similar upward trends until 1972 when the Scottish population started to decline; a much more noticeable decline in the Scottish robin (Erithacus rubecula) population began in 1966.

The total density of territory‐holding males has not increased but the biomass has and this is due to more, bigger birds but fewer passerines. The species diversity measured by the Shannon Wiener index (H.) has improved a little since 1971 and it is concluded that during the study period the farmland plots censused in Scotland have on average not shown evidence of deterioration as habitats for territory‐holding birds.
The ecology of skylarks on arable farmland
Authors: Green Rhys E.
Published: February 2008

Skylarks are common birds on arable farmland throughout Britain and have recently been implicated in grazing damage to sugar‐beet seedlings in Eastern England. Their feeding habits and their relationship to variations in food supplies were described.
Distribution and analysis of cabbage root fly pupal populations
Authors: FINCH S. , SKINNER G. , FREEMAN G. H.
Published: February 2008

The distribution of cabbage root fly pupae around roots of brassica plants was studied from 1971 to 1977.

Different distributions of the first and overwintering generations of pupae demonstrated that the two should be considered separately. The number of plant roots to be sampled for a given level of precision was greater for the first than for the overwintering generation. Sampling plans for the range of pupal populations normally encountered during the two generations are illustrated. They were unaffected by changes in plant species, plant cultivar and plant density and were also suitable for use in both untreated and insecticide‐treated crops. No attempts were made to obtain a plan for the second generation of pupae because of the difficulty in accurately predicting the occurrence of this generation in the field. Taylor's power law gave a good description of the distribution of pupae. Although many factors changed between generations the value of the power remained constant at 1–3, apparently the index of aggregation characteristic of the pupal stage of the cabbage root fly in Canada as well as in England.
The occurrence, hosts and properties of lilac chlorotic leafspot virus, a newly recognised virus from Syringa vulgaris
Authors: BRUNT A. A.
Published: February 2008

Lilac chlorotic leafspot virus (LCLV), a hitherto undescribed virus, was isolated from three of 65 lilacs (Syringa vulgaris) with chlorotic leafspotting symptoms growing in S.E. England. The virus was transmitted readily by sap‐inoculation to 21 of 52 species from eight of 20 families, but it was not seed‐borne in four hosts or transmitted in the semi‐persistent manner by any of four aphid species. The virus was moderately stable in vitro; sap from Chenopodium quinoa was infective after 10 min at 60 but not 65 oC, after 8–16 days at 20 oC or 25–30 wk at 2 oC, and after dilution to 10‐3 but not 10‐4.

Up to 180 mg of purified virus per kg leaf tissue were obtained from C. quinoa by clarification of buffered leaf extracts with 8% (v/v) n‐butanol, followed by one cycle of differential centrifugation and molecular permeation chromatography on controlled pore glass beads (700 Å, 120–200 mesh). LCLV has fragile flexuous filamentous particles which, when intact, mostly measured c. 12‐5 times 1500–1600 nm; the helical substructure (pitch c. 3–7 nm) was clearly visible on some particles mounted in uranyl acetate. The particles sedimented as a single component (sedimentation coefficient 96 S; buoyant density 1–302 g cm‐3) and contained c. 5% nucleic acid and a single polypeptide of mol. wt 27 times 103. Although these properties place LCLV in the closterovirus group, the virus showed no serological relationship to any of six closteroviruses (beet yellows, beet yellow stunt, carnation necrotic fleck, apple chlorotic leafspot, apple stem grooving and potato virus T) and differed from other recognised or possible members of this group in host range and/or symptoms induced in indicator species.

The infrequent occurrence of LCLV in lilac in S.E. England indicates that the virus could probably be eradicated by selecting only virus‐free plant material for propagation.
Detection of resistance to aphids in cereals
Authors: LOWE H. J. B.
Published: February 2008

Resistance to Sitobion avenae and Metopolophium dirhodum was assessed by caging aphids on the upper part of mature tillers. Despite variation in the results, considered to be due mainly to differences amongst plants of different ages, certain cultivars consistently supported fewer aphids. Winter wheats Anna Migliori and Marsters Al and Indian spring barleys EB 921 and DL 107 were identified as resistant cultivars useful for reference in further work.
Aseptic cultivation of sapling trees for studies of nutrient responses with particular reference to phosphate
Authors: PELHAM J. , MASON P. A.
Published: February 2008

Plantlets of Betula verrucosa and B. pubescens, originally obtained from seeds surface sterilised in hydrogen peroxide, were grown on slopes of mineral nutrient agar, modified Ingestad, in plastic tubes kept at room temperatures (26 °C) with supplementary lighting. Cuttings taken from plants grown in this way rooted readily on media supplemented with 0–1 mg/1 naphthalene acetic acid and 10 g/1 sucrose.

In replicated experiments to determine the optimal conditions for growth, the effects of varying salt concentrations, the addition of charcoal and changes in ventilation and amounts of phosphate were studied. It was found necessary to ‘confound’ variations attributable to the sources of seedlings/cuttings in the experimental designs.

The method has facilitated the detection of clones in both B. verrucosa and B. pubescens, which, although growing equally well with large amounts of readily available phosphate, differed greatly when phosphate was in short supply. Low phosphorus ‘tolerant’ and ‘intolerant’ types were identified.
Chemical aids to drying seeds of beans (Phaseolus vulgaris) before harvest
Authors: HOLE C. C. , HARDWICK R. C.
Published: February 2008

The effects on seed moisture content of seven different chemical formulations applied to bean (Phaseolus vulgaris) crops in two successive years were observed. Those containing bipyridyl herbicides caused the biggest effects. In 1974, diquat (0–59 kg a.i. ha‐1), applied to a French bean crop cv. Processor 26 days before harvest, decreased seed moisture content by 98 mg g_1 dry weight below a control value of 438 mg g_1. In 1975, diquat applied at the same rate to a navy bean crop cv. Seafarer 16 days before harvest, decreased seed moisture content by 123 mg g_1 below a control value of 364 mg g_1. Diquat applied at a lower rate (0–3 kg a.i. ha‐J) caused a decrease of 79 mg g_1 and paraquat decreased seed moisture by 147 mg g_1. In both years smaller effects were observed for dimexan (15 kg a.i. ha‐1) which decreased seed moisture content by 32 mg g‐1 in 1974 and 72 mg g_1 in 1975 and for ethephon (1‐0 kg a.i. ha‐1) which caused decreases of 78 mg g_1 in 1974 and 31 mg g_1 in 1975. In 1975, metham‐sodium (70 kg a.i. ha‐1) a soil sterilant, proved almost as effective as the bipyridyls, decreasing moisture content by 105 mg g_1. Trimming the roots mechanically reduced seed moisture by 67 mg g_1. Other chemical treatments, tried in 1975 only, were less effective and decreased seed moisture content by 31–60 mg g_1. These were Wiltz‐65 (pentanoic and hexanoic acids, 14‐6 kg a.i. ha‐1), N252 (dihydro‐dimethyl‐dithiin tetroxide, 0–56 kg a.i. ha‐1) and an application of diquat (0–3 kg a.i. ha‐1) to plants treated 10 days before with ethephon (1‐0 kg a.i. ha‐1)‐ In addition to the effects on seed moisture content, all treatments decreased seed yield. The largest decreases were caused by diquat and were attributable mainly to effects on mean seed weight. The paper concludes with an economic analysis which shows that at present prices chemical drying of beans in the field is not worthwhile because the yield loss nullifies any savings in drying costs.
Studies on plant growth‐regulating substances. L. The cytokinin activity of some substituted benzyloxypurines
Authors: WILCOX E. J. , SELBY C. , WAIN R. L.
Published: February 2008

The series of 6‐mono and di‐methyl and mono‐ and di‐methoxy benzyloxypurines have been prepared and tested for cytokinin activity in a number of biological tests. The 2‐methyl and 3‐methoxy derivatives were more active than the unsubstituted compound but substitution into any other position led to a decrease in activity. Di‐substitution also caused a lowering of activity particularly with the di‐methoxy compounds.