bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on inheritance of resistance to root aphid, Pemphigus bursarius, in lettuce
Authors: DUNN J. A.
Published: February 2008

The inheritance of resistance to lettuce root aphid, Pemphigus bursarius, was studied in lettuce using the Wellesbourne cultivars Avondefiance and Avoncrisp as resistant parents and Borough Wonder and Webb's Wonderful as aphid‐susceptible parents. All four cultivars were crossed in all possible combinations including reciprocals and the response to root aphid of plants in the P1F1F2 and BC generations was assessed using apterae of P. bursarius from the lettuce cv. Iceberg. Resistance to attack was clearly inherited and the parents appeared to be homozygous for their resistance or susceptibility. In the F1 generation, however, in all crosses between resistant and susceptible parents, segregation into susceptible, resistant and some slightly less resistant plants occurred. This and the highly significant differences in segregation between pairs of reciprocal crosses in the F1 and other generations indicate that the inheritance of resistance to root aphid is controlled by extra‐nuclear factors. Modifying genes might also be involved but there appears to be no linkage of root aphid resistance with resistance to downy mildew, for which the Wellesbourne lettuces were bred.
The induction of top‐roll symptoms on potato plants by the aphid Macrosiphum euphorbiae
Authors: GIBSON R. W.
Published: February 2008

In the field, caged potato plants of King Edward and Majestic cultivars infested with the potato aphid Macrosiphum euphorbiae developed top‐roll symptoms, the proportion of affected plants increasing with the size and persistence of the aphid population. Yield of tubers from plots in which 90% of the plants had top‐roll symptoms was 40% less than that from control plots; yield of saleable ware was even less. Foliage produced after the aphids had been killed was symptomless even when it arose from the axil of an affected leaf. Caged field plants treated with phorate granules to prevent aphid attack did not develop top‐roll.

Prolonged infestation of Pentland Crown, Majestic and King Edward plants by M. euphorbiae in a glasshouse induced rolling of upper leaves similar to top‐roll of field plants. Experimental results suggest that rolling was directly attributable to heavy attack by M. euphorbiae, not to an aphid‐transmitted pathogen.
The rates of fungal development and lesion formation in leaves of Vicia faba during infection by Botrytis cinerea and Botrytis fabae
Authors: MANSFIELD J. W. , DEVERALL B. J.
Published: February 2008

Loss of the water droplet above inoculation sites during the first day after inoculation inhibited lesion formation by Botrytis cinerea and prevented the development of spreading lesions of B. fabae. With droplets present two general patterns of infection by B. cinerea were determined; in one, few or no symptoms were produced and in the other, limited lesions developed with marked browning of the inoculation site. Where few or no symptoms were produced, germination and germ‐tube growth were inhibited on the leaf surface. B. cinerea was inhibited within the leaf at sites bearing limited lesions; invading hyphae were restricted to brown epidermal cells. Fungal growth on the leaf surface was greatest at sites with most browning beneath the droplet area. Variation in lesion development by B. cinerea could not be related to droplet position or leaf damage during normal preparation for inoculation. Plants differed in their susceptibility to lesion formation by B. cinerea.

B. fabae, with droplet present, was not inhibited on the leaf surface and spread inter‐ and intra‐cellularly beneath the inoculum drop and then into surrounding tissues. Delay in spread until the inoculation site was completely necrotic and colonized suggested that B. fabae is partially inhibited during the initial phase of infection. The rate of lesion spread varied in different plants and was most rapid in the youngest leaves.
Transmission of the hop strain of arabis mosaic virus by Xiphinema diversicaudatum*
Authors: VALDEZ R. B. , McNAMARA D. G. , ORMEROD P. J. , PITCHER R. S. , THRESH J. M.
Published: February 2008

Hop plants became infected with the hop strain of arabis mosaic virus (AMV(H)) when grown in hopfield and woodland soil in which infected plants had been growing. Infection occurred in soil infested with the dagger nematode Xiphinema diversicaudatum, but neither in uninfested soil nor in soil previously heated to kill nematodes. X. diversicaudatum transferred direct from hop soils transmitted AMV(H) to young herbaceous plants and to hop seedlings; some of the hop seedlings developed nettlehead disease. A larger proportion of plants was infected using X. diversicaudatum obtained from a woodland soil and then given access to the roots of hop or herbaceous plants infected with AMV(H). AMV(H) was transmitted by adults and by larvae, in which the virus persisted for at least 36 and 29 wk, respectively.

Difficulties were encountered in detecting AMV(H) in infected hop plants, due partly to the delay in virus movement from roots to shoots. Infection of hop shoots was seldom detected until the year after the roots were infested and sometimes nettlehead symptoms did not appear until the third year. Isolates of arabis mosiac virus from strawberry did not infect hop. The results are discussed in relation to the etiology and control of nettlehead and related diseases of hop.
Transference of resistance to black‐currant gall mite, Cecidophyopsis ribis, from gooseberry to black currant
Authors: KNIGHT R. L. , KEEP ELIZABETH , BRIGGS J. B. , PARKER JILL H.
Published: February 2008

Field and insectary tests confirmed that the black‐currant gall mite (Cecidophyopsis ribis) is unable to survive on gooseberry and red currant.

A dominant gene Ce, controlling resistance to the gall mite, has been transferred from gooseberry to black currant. Resistant, large‐fruited, self‐fertile black currants of commercial potential have been obtained in the third backcross.

One accession of Ribes bracteosum and three of R. americanum proved field susceptible to the gall mite, but twenty‐four accessions of other Ribes species remained free from galled buds for at least 3 years in an infection plot.
Breeding for resistance to American gooseberry mildew, Sphaerotheca mors‐uvae, in the gooseberry (Ribes grossularia)
Authors: KEEP ELIZABETH
Published: February 2008

Strong resistance to American gooseberry mildew (Sphaerotheca mors‐uvae) occurred in eight out of ten F1 progenies from crosses of resistant North American Eugrossularia species with European gooseberry cultivars or seedlings. Bimodal segregations in four of these F1's and in one F1 derived from the wild European Ribes grossularia uva‐crispa suggested that each donor carried a major dominant resistance gene. Such a gene, Sph1 was identified in a first backcross from R. oxyacanthoides.

Accessions of R. oxyacanthoides, R. leptanthum and R. watsonianum proved the most promising donors of resistance to mildew and leaf spot (Pseudopeziza ribis).
A comparison of seasonal changes in deposition of spores of Erysiphe graminis on different trapping surfaces
Authors: JENKYN J. F.
Published: February 2008

Vertical sticky cylinder traps were as useful as a volumetric trap for detecting seasonal changes in numbers of Erysiphe spores from barley crops. Changes in spore catches by both traps also resembled changes in numbers of pustules developing on initially healthy barley seedlings exposed in the same crop. Seasonal changes in catches on cylinders exposed at some distance from any crop differed from those on cylinders just above barley crops.

Cylinder traps are cheap, simple and quicker to scan than volumetric traps and seem likely to be acceptable alternatives to them for much work on cereal mildew and other air‐dispersed pathogens, particularly for rautine trapping at many sites.
Disease gradients and small plot experiments on barley mildew
Authors: JENKYN J. F. , BAINBRIDGE A.
Published: February 2008

In two experiments, on Julia and Zephyr spring barley, evidence was obtained that the development of powdery mildew in sprayed plots depended very much on their proximity to unsprayed crop. The effective period of control achieved with one spray was greater where plots were well separated from unsprayed crop than where they were surrounded by or very close to unsprayed crop. There is probably a risk that small plot experiments may not only underestimate the potential effectiveness of fungicides in agricultural practice, but also give misleading information on optimal spray timing.
Aphid‐transmitted viruses from lilies in Britain
Authors: MOWAT W. P. , ŠTEFANAC ZLATA
Published: February 2008

Three aphid‐transmitted viruses, tulip breaking, lily symptomless and cucumber mosaic, were obtained from lilies in Britain. Tulip breaking virus was detected by the leaf mottle produced in Lilium formosanum, cucumber mosaic virus by inoculation of sap to Nicotiana clevelandii and Chenopodium quinoa, and lily symptomless virus by electron microscopy of crude leaf extracts from symptomless L. formosanum. Liiy symptomless virus was transmitted by Myzus persicae, Macrosiphum euphorbiae, Aulacorthum solani and Aphis fabae. M. persicae, which in a small experiment appeared a more efficient vector than A. fabae, transmitted the virus in a non‐persistent manner. This conflicts with the original report of transmission in a persistent manner by A. gossypii but no transmission by M. persicae. The possibility that there are two distinct viruses with similar pathological effects is discussed. Tulip breaking and lily symptomless viruses spread to bait plants of L. formosanum within a field planting of lilies in Scotland especially during July to September; lily symptomless virus was the more prevalent. No spread of cucumber mosaic virus was detected.
Effects of photoperiod, temperature and vernalization on the phenology and spikelet numbers of spring wheats
Authors: WALL P. C. , CARTWRIGHT P. M.
Published: February 2008

Fourteen cultivars of north temperate, Australian, Mexican and Rhodesian origins, were grown in eight treatments: 2‐day‐lengths (10 h and 14h) × two temperature regimes (18/13 °C and 25/20 °C) × two seed vernalization treatments (unvernalized and 28 days at 1–2 °C). Numbers of days to 50 % ear emergence, leaf numbers and spikelet numbers of the main shoots were recorded.

The north temperate cultivars were the most sensitive to daylength: in long days their mean spikelet number was 15 and they headed in 40–50 days, while in short days they had a mean of 24 spikelets and failed to head in 100 days. The Rhodesian cultivars were the least sensitive, but nevertheless headed 20–30 days earlier and had three to five fewer spikelets per ear in long days.

The effects of vernalization on the tropical cultivars were related to maturity class: they ranged from negligible in early cultivars such as Sonora 64 and Devuli to decreases of 20 days to heading and seven spikelets in late cultivars such as Mexico 120 and Cajeme 71 in long days.

The effects of temperature varied with cultivar and with vernalization treatment. Early cultivars and vernalized late cultivars headed earlier and had fewer spikelets in the warmer regimes while unvernalized late cultivars tended to have more spikelets and headed later. It is suggested that some vernalization of these late cultivars took place in the cooler regime.

The significance of the results for the understanding of the physiological basis of the adaptation of wheat cultivars to different climatic zones is discussed.
Bird damage to sugar beet
Authors: Dunning R. A.
Published: February 2008

Pest damage to sugar beet, including that by birds, has been recorded since 1957. During that time damage by rooks has decreased almost to nil, but some other bird damage has greatly increased, most probably as a result of changing agronomic practices, especially the extensive use of herbicides, the introduction of monogerm seed, and the increasing practice of ‘planting‐to‐a‐stand’. The most severe bird damage in the spring is grazing by several species, and in early summer localized felling of plants by pheasants. Observations in the mid–1960's of causes of seedling and plant losses suggested that birds were then of minor importance; the British Sugar Corporation currently consider that birds are the most serious pest of sugar beet. The distribution of the reported damage does not seem to follow any national pattern. In small‐plot field trials possible repellent materials such as anthraquinone, methiocarb or thiram, applied to seed or foliage, did not decrease the extent of grazing.
Pustules on wood as sources of inoculum in apple scab and their response to chemical treatments
Authors: COOK R. T. A.
Published: February 2008

The green stems and leaves of potted Cox's Orange Pippin trees were susceptible to infection by Venturia inaequalis from June to August. Some isolates of the fungus showed conspicuous ability to attack the wood.

In the orchard, many conidia were released from pustules in early March (2—3 wk before bud‐burst) but in the 3 years examined (1967—9) most were liberated in April and May. In 1969 it was shown that a decline in numbers in June was accompanied by a decrease in viability of conidia.

Infections near the tips of leading shoots were partially controlled by a single treatment with 5% urea (aqueous solution) in October 1966 or 2% urea or 0·01% phenylmercuric chloride (PMC) in March 1967. The subsequent reduction in inoculum was correlated with a reduction in the numbers of primary infections developing on leaves. Basal infections on leading shoots were not susceptible to treatment in October 1967 or March 1968, but in 1969 similar infections were controlled with PMC applied mid‐April when the pustules had burst and were actively sporulating.
Changes in wyerone acid concentrations in leaves of Vicia faba after infection by Botrytis cinerea or B.fabae
Authors: MANSFIELD J. W. , DEVERALL B. J.
Published: February 2008

Wyerone acid was produced by leaves of Vicia faba in response to infection by both Botrytis cinerea and B.fabae. Host cell death caused by either fungus appeared to be the trigger for rapid wyerone acid synthesis, although the phytoalexin was not confined to brown cells. At B. cinerea inoculation sites wyerone acid concentration increased rapidly, at the time of fungal invasion of the epidermis, to levels greater than that completely inhibitory to mycelial growth. Wyerone acid is therefore probably the primary cause of the inhibition of B. cinerea within infected tissue. The partial blackening of B.fabae inoculation sites and surrounding peripheral tissues was accompanied by an increase in wyerone acid. There followed a striking decrease as tissues became completely blackened and invaded by B.fabae. B.fabae appeared to metabolize wyerone acid and prevent its accumulation in invaded tissues. Mycelial growth of B. fabae was less sensitive to wyerone acid than was B. cinerea.

The differing abilities of B.fabae and B. cinerea to spread from lesions after both have induced wyerone acid production probably depend on both their differing sensitivities to the phytoalexin and their abilities to metabolize it to less toxic products.
Spread of raspberry bushy dwarf virus by pollination, its association with crumbly fruit, and problems of control
Authors: MURANT A. F. , CHAMBERS J. , JONES A. T.
Published: February 2008

Raspberry bushy dwarf virus (RBDV) was transmitted to raspberry seed both through the pollen and through the ovule and it infected plants pollinated with infected pollen. It did not infect plants prevented from flowering, and transmission through pollen seems to be the only method of spread in the field; in the proximity of infectors, most plants became infected during the first two or three flowering seasons. Plants containing RBDV showed no obvious symptoms, but healthy or infected flowers pollinated with infected pollen produced ‘crumbly’ fruit, containing a high proportion of aborted drupelets. RBDV was difficult to eliminate from infected raspberry by heat therapy. Raspberry cultivars that fail to become infected naturally were also immune to infection by grafting. Use of immune cultivars offers the only method of control and, because infected plants may produce crumbly fruit, future cultivars should if possible possess immunity to RBDV.
The time of determination of gynoparae and males in the bird cherry–oat aphid, Rhopalosiphum padi
Authors: DIXON A. F. G. , DEWAR A. M.
Published: February 2008

Apterous exules of Rhopalosiphum padi which experienced short photoperiods only during the first half of their nymphal life all produced gynoparae which made up 57% of the offspring produced in the first 7 days of the mother's reproductive life. Short photoperiods during the second half of a mother's nymphal life did not induce the production of gynoparae. However, when short photoperiods were experienced throughout a mother's nymphal life significantly more gynoparae (82%) were produced. Ten per cent of the offspring of mothers that experienced short photoperiods only during their adult life developed into gynoparae. Of the offspring reared in short photoperiods, but born to mothers reared and kept in long photoperiods, 30% developed into gynoparae. When mothers were exposed to short photoperiods in their adult life and their offspring so treated, then 90% of the offspring developed into gynoparae.

Males only occurred amongst the last offspring of mothers that experienced short photoperiods in either the first or the second half of their nymphal life.
Supercooling and the low‐temperature survival of the green spruce aphid Elatobium abietinum
Authors: POWELL W.
Published: February 2008

Laboratory investigations into the low‐temperature tolerance of the green spruce aphid, Elatobium abietinum, revealed that the insect was killed by freezing. Aphids and host Sitka spruce needles showed similar seasonal changes in supercooling ability. A noticeable increase in this ability occurred between June and October. Aphids were more susceptible to low temperatures when attached to the plant. It is suggested that mortality resulted from ice which formed in the sap of the host needles and spread into the feeding aphids via their mouthparts. Neither the chlorotic banding of needles, caused by aphid feeding, nor needle length affected needle supercooling. Increased duration of exposure increased the probability of freezing of supercooled needles at low temperatures.

A small percentage of first‐instar nymphs supercooled to much lower temperatures than the remainder of the population. These were newly born nymphs whose high supercooling ability markedly decreased when they began to feed.
The effect of store conditions on the rotting of apples, cv. Bramley's Seedling, by Nectria galligena
Authors: SWINBURNE T. R.
Published: February 2008

The log of the time interval between inoculation with Nectria galligena in October and the onset of rotting in apples held in air was proportional to the deficit between the temperature of incubation and 25°C, but temperature did not affect the rate of subsequent rot expansion. Rots expanded equally fast whether apples were held in dry or moist air. The quantity of rotted tissue obtained after incubating inoculated apples in atmospheres containing up to 12.5% CO2 increased with increasing concentrations of CO2 greater than 2.5%. The quantity of rotted tissue obtained in apples incubated in 10% CO2 was three times as great as that obtained after incubation in air. The incidence of natural rots was lower in apples stored at 4% CO2 than in those stored in air and rotting increased with increasing concentrations of CO2 higher than 4%. Colonies of N. galligena grew faster on malt agar plates incubated in 5% CO2 than in air, but growth was slower in 10% CO2 than in air. The quantity of benzoic acid per mg hyphae accumulated in developing lesions was similarly related to the CO2 concentrations up to 2.5% but decreased at higher concentrations, and the quantities found in apples stored in CO2 concentrations >5.0% CO2 were less than in those stored in air.
Spiroplasmas are the causal agents of citrus little‐leaf disease
Authors: MARKHAM P. G. , TOWNSEND R. , BAR‐JOSEPH M. , DANIELS M. J. , PLASKITT AUDREY , MEDDINS BRENDA M.
Published: February 2008

A spiroplasma isolated from citrus with little‐leaf disease was grown in a cell‐free medium and injected into leafhoppers (Euscelis plebejus) Injected leafhoppers, but not those fed on infected plants, transmitted the spiroplasma to white clover (Trifolium repens cv. S100) and sweet orange (Citrus sinensis cv. Valencia). Infected clover plants were severely stunted; infected sweet orange plants showed typical symptoms of citrus little‐leaf disease. The spiroplasma was detected in clover and sweet orange plants by electron microscopy; the helical morphology of the organisms was most easily recognizable in sections 150–200 nm thick. The organism was re‐isolated in cell‐free media both from infected plants and from injected E. plebejus. The original isolate and those re‐isolated from experimentally infected clover and sweet orange appeared by morphological, cultural, biochemical and serological criteria to be identical to each other and to the R8‐A2 (type) and C‐189 strains of Spiroplasma citri. Serological tests and electrophoretic analysis of protein preparations indicated no relationship to Acholeplasma laidlawii, although this organism survived for at least 10 wk after injection into E. plebejus. Our results show that the causal agent of little‐leaf disease is related to S. citri.
Resistance to organophosphates in red spider mite, Tetranychus urticae, from English hop gardens
Authors: CRANHAM J. E.
Published: February 2008

Two strains of Tetranychus urticae, collected in 1969 from hops in Kent (strain RK) and Wisbech, Cambridgeshire (RW), showed a similar pattern of resistance to organophosphates, high to parathion (> 100 ×), low to azinphos‐ethyl (7 ×) and intermediate to demeton‐S‐methyl (21–27 ×); they were both fully susceptible to tetradifon, dicofol and formetanate. RK showed greatei than 50 × resistance to fourteen other organophosphates; exceptions were azinphos‐methyl (11 ×), phosphamidon (21 ×) and methidathion (31 ×). Resistance in RK was shown to be controlled by a single major gene, incompletely dominant with parathion but nearer to intermediate in expression to demeton‐S‐methyl and azinphos‐ethyl. A test for allelism showed that the major genes for O.P. resistance in RK and the Dutch strain Baardse reside at the same locus or are closely linked. The results are compared with other work on T. urticae and on Panonychus ulmi.
Biochemical tests for identification of mycelial cultures of basidiomycetes
Authors: TAYLOR J. B.
Published: February 2008

Twenty‐four biochemical tests have been developed to identify basidiomycetes from mycelial cultures. Eleven are designated ‘instant tests’ because results are obtained within 24 h; ten of these test for specific enzymes, the other is based on a reaction between vanillin and unknown fungal metabolites. The remaining thirteen tests require incubation periods ranging from 1 to 4 days and are thus designated ‘incubated tests’.

Sixteen of these tests were applied first to identified isolates of Peniophora sacrata, Sclerotium rolfsii, Stereum purpureum and Trametes versicolor. They distinguished these species satisfactorily, so these sixteen tests, and eight others devised subsequently, were applied to unidentified basidiomycetes isolated from diseased roots of fruit crops. The results of these tests enabled the isolates to be placed in seven groups. All isolates in a particular group were morphologically similar which further suggested that each group might correspond to a species and that isolates could be defined on the basis of biochemical tests.
Insecticide granule distribution and the control of Lycoriella auripila (Diptera: Lycoriidae) in mushroom casing material
Authors: BINNS E. S.
Published: February 2008

In laboratory tests the distribution of insecticide in peat–chalk mushroom casing greatly affected the number of adult sciarids which emerged from larvae placed in 50 g samples. Only thionazin markedly reduced emergences when granules were clumped in the centre of the sample of casing. The slope of dosage mortality data for clumped granule treatments was less steep than for mixtures and gave estimated LD95 values of 16300 and 26.8 ppm respectively. Thus, the number of adults which emerged when granules amounting to 6.4 mg of chlorfenvinphos were clumped was 65% of those emerging when only 0.4 mg a.i. was mixed into 50 g casing. However, adults did not emerge when 3.2 mg of the same insecticide was mixed throughout the sample. Increased doses did not, therefore, compensate for inadequate mixing.

With 0.2–0.4 mg a.i. chlorfenvinphos mixed through the casing, about three times as many sciarids emerged with the intact granules than when pulverized granules were used. This showed the lack of mobility of this chemical in peat‐chalk mixtures and the need for it to be homogeneously incorporated in commercial casing. Pirimiphos‐ethyl, diazinon and thionazin also gave improved kills when mixed into the casing rather than clumped.

A χ2 test of the mortality data suggested a non‐linear dosage‐mortality relationship for treatments amounting to half the dish. However, LD95 estimates of 37.5 and 62.2 ppm were obtained for mixed and quadrant treatments. Thus, when 3.2 mg chlorfenvinphos was mixed into only half of the volume of casing, the number of adults emerging was only 6% of that from untreated casing. However, larval movement was negligible in untreated casing and this appeared to limit the effectiveness of chlorfenvinphos and pirimiphos‐ethyl when they were not evenly distributed throughout the casing. With thionazin and diazinon, mobility of the insecticide appeared to compensate for uneven distribution.
Some biophysical principles underlying the controlled atmosphere storage of plant material
Authors: BURTON W. G.
Published: February 2008

Controlled atmosphere (CA) storage is of use for commodities which potentially can undergo rapid and unacceptable biochemical change. In air, the oxygen status of most plant material, including fleshy storage organs and fruits, suffices, even in the centre, for cytochrome oxidase to be fully saturated. Conflict of evidence exists as to possible O2 and CO2 gradients in fruit which, though physiologically unimportant in air, could be important under CA conditions. CA storage gives possible control of internal O2 from o to about 80–95%; internal CO2 from about 3–4 to 100%; and both simultaneously to intermediate values. Calculated molarities of dissolved O2, CO2 and ethylene are given for various atmospheres.

The differences in the O2 concentrations recommended for different varieties of apple are not readily explicable. Varietal differences in susceptibility to CO2 injury could possibly result from anatomical, rather than biochemical, differences. This could be determined partly by resolving the conflict of evidence mentioned above. Variability of plant material prevents precise control of intercellular atmosphere; recommended atmospheres can be designed only to avoid completely anaerobic conditions and a harmful level of CO2 in the centre of the least permeable individual fruit or vegetable. Effects of low O2 and high CO2 are briefly described.
The development and quality of forage grass seeds produced under different isolation conditions
Authors: BEAN E. W.
Published: February 2008

The effects of five different environments, outside under natural conditions, glasshouse, Polythene enclosures (two designs), and muslin shades, upon seed development and seed quality in four varieties of forage grasses were investigated in two years. In 1972 pollen release occurred first in the Polythene enclosure and the highest pollen counts were obtained from this treatment and under glasshouse conditions. Plants in which seed development occurred in the glasshouse had the highest floret fertility, 1000 seed weight and seed weight per inflorescence, while those grown under Polythene gave low values for all these characters. Plants in which seed development occurred under muslin shades, where light intensity was reduced by half, gave seed yields equal to those grown in full day‐light. In 1973 the germination rate was highest in seeds produced under Polythene and lowest in those produced under outside conditions. The dry weights of seedlings from the outside treatment were lower than those from the glasshouse and Polythene enclosures in four of the five experiments. It is suggested that isolation methods for the production of small seed lots should be standardized, and that glass isolation chambers are the most efficient method of producing small seed lots for plant breeding and agronomic investigations.
Some observations on a Tylenchid nematode Howardula sp. parasitizing the mushroom phorid Megasalia halterata (Phoridae, Diptera)
Authors: RIDING IRENE L. , HAGUE N. G. M.
Published: February 2008

Howardula sp. parasitizes the Mushroom phorid fly Megasalia halterata destroying the fat body and follicular membrane of the fly, decreasing copulation and egg output. With increasing hyperinfestation the fly is rendered sterile. Howardula sp. is host density dependent and reaches a maximum incidence in September and October. Under laboratory conditions fly populations were eliminated in three to five generations. The implications for possible biological control of M. halterata are discussed.
Studies on the feeding behaviour of the eriophyid mite Abacarus hystrix, a vector of grass viruses
Authors: GIBSON R. W.
Published: February 2008

On Italian ryegrass (Lolium multiflorum cv. S 22), the eriophyid mite Abacarus hystrix usually fed on the bulliform epidermal cells at the base of the grooves on the adaxial leaf surface. Scanning electron micrographs illustrate (1) the external morphology of the mouthparts of the mites, (2) how, prior to feeding, they remove cuticular leaf wax with their rostra and (3) feeding punctures in epidermal cells made by the styliform chelicerae. Of eleven graminaceous species tested, A. hystrix only settled on Festuca pratensis, L. perenne and L. multiflorum. On L. multiflorum, the mites preferred the youngest leaves and on mature leaves, preferred the youngest part.
Effects of dual infections of Puccinia hordei and Erysiphe graminis on barley, cv. Zephyr
Authors: SIMKIN M. B. , WHEELER B. E. J.
Published: February 2008

In replicated field trials in 1971 and 1972, plots of Zephyr barley were obtained with (1) powdery mildew, (2) brown rust, (3) both diseases or (4) neither disease, by using appropriate systemic fungicides.

Mildew was fairly severe (up to 40% infection of individual leaves) and significantly reduced yield and grain size in both years. Rust was not severe (< 5 % on any leaf) in either year and it reduced yield and grain size only in 1972. In these conditions the mean percentage losses (relative to treatment 4) in plots with both diseases were approximately equivalent to the sum of those from powdery mildew and brown rust alone. There was no significant mildew × rust interaction in respect of yield or senescence of leaves, but comparisons of the infection rate of Erysiphe graminis on leaves with and without rust in similar situations within the 1972 trial suggested that rust affected the development of mildew on the same leaf. Experiments in the glasshouse using the first leaf of seedlings, not chemically treated, confirmed that there could be marked interactions between the pathogens on a single leaf. Pre‐inoculation with one pathogen generally reduced the development of the other.
Seasonal changes in infection of barley seedlings by Erysiphe graminis f.sp. hordei
Authors: JENKYN J. F.
Published: February 2008

Infection of artificially inoculated barley seedlings, exposed out of doors, was variable but there was a seasonal trend. As temperature affects both incubation time and the proportion of successful infections, these two factors will have additive effects on disease development. Infections developed only slowly in winter but, in both 1972 and 1973, conditions became much more favourable to infection in late April or early May.
Field experiments in the control of Verticillium dahliae and Heterodera rostochiensis on potatoes
Authors: HIDE G. A. , CORBETT D. C. M.
Published: February 2008

Potatoes were grown in soil infested with Verticillium dahliae and Heterodera rostochiensis and treated with methyl bromide, aldicarb or benomyl. Successive crops were grown in subsequent years on the same plots but without further treatment. Largest yields in the year of treatment were from plots fumigated with methyl bromide but in the second crop benomyl‐treated plots yielded most. Neither methyl bromide nor aldicarb affected yields from trie third crop.

After lifting the first crop, soil from plots treated with methyl bromide or benomyl contained less V. dahliae than that from plots receiving aldicarb or nothing. Soil was also less infective after the second crop following methyl bromide fumigation, but not the third. Plots treated with methyl bromide or aldicarb contained many fewer H. rostochiensis than untreated plots after the first crop, slightly less after the second and equal numbers after the third crop. H. rostochiensis were also fewer in benomyl‐treated plots than in untreated after the first crop, but, surprisingly, were fewest after the second crop. The increased yield after applying benomyl to soil seems to depend more on its effect on H. rostochiensis than on V. dahliae.

Fumigating with methyl bromide decreased common scab and black scurf on progeny tubers but increased infections by Oospora pustulans.
Experiments with MBC derivatives for the control of Dutch elm disease
Authors: GIBBS J. N. , CLIFFORD D. R.
Published: February 2008

Preparations of methyl benzimidazol‐2‐ylcarbamate (MBC) hydrochloride stabilized with HC1, MBC nitrate stabilized with lactic acid and MBC bisul‐phate stabilized with KHS04 were made from technical MBC. As it was the least phytotoxic to elm shoots, the hydrochloride was selected for field experiments on the control of Dutch elm disease using 6 m elms. In protectant experiments using 1.51 of 0.25 or 0.5 % MBC per tree, only five of eighteen injected trees became infected while all the control trees were severely diseased. In curative experiments, injection with 0.25 % MBC 2 and 4 wk after inoculation with Ceratocystis ulmi kept symptoms to < 1 and 5% respectively, compared with 76% in untreated inoculated trees. MBC at 0.5 % Save similar results.
Control of pea cyst‐nematode, Heterodera goettingiana, by small amounts of aldicarb, Du Pont 1410, Ciba‐Geigy 10576 or Dowco 275 applied to the soil at planting time
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

Aldicarb, or Du Pont 1410 (S‐methyl‐I‐(dimethylcarbamoyl)‐N‐[(methyl‐carbamoyl)oxy]thioformimidate), at 2.8–22.4 kg a.i./ha incorporated in the seed‐bed before sowing greatly increased the yield of peas in a clay loam and two sandy clay soils infested with pea cyst‐nematode, Heterodera goettingiana, and lessened or prevented increase in the number of nematodes. CibaGeigy 10576 (an organophosphorus compound) at 5.6–22.4 kg a.i./ha was similarly effective in a sandy clay soil. Dowco 275 (O, O‐diethylO‐(6‐fluoro‐2 pyridyl) phosphorothioate) at 5.6 or 11.2 kg a.i./ha also controlled the nematode well in the clay loam and in a sandy clay soil but although it greatly increased the yield of peas in the clay loam, it did not increase yield in the sandy clay.
The utilization of recently assimilated carbon in graminaceous plants
Authors: RYLE G. J. A. , POWELL C. E.
Published: February 2008

Isotopic carbon and infra‐red gas analysis techniques were used to measure the following growth attributes in maize, sorghum, winter wheat and perennial ryegrass: the rate of entry of carbon into each main shoot leaf; the rate of translocation of leaf assimilate to meristems; the fraction of leaf and total shoot assimilate respired in one diurnal period; and the distribution of residual assimilate to new leaf, stem, axillary shoots and root.

The two tropical plants possessed higher leaf assimilation rates and larger leaves than the temperate species, but their efficiency of translocation was only marginally superior in the experimental conditions. In all species, c. 25% of the assimilate generated in the 8·4h photoperiod was respired in in the same diurnal period. Maize and sorghum partitioned a greater proportion of their total shoot assimilate to new leaf tissue at the main shoot apex and to root than wheat and ryegrass. On the other hand, wheat and ryegrass exported up to 30% of their assimilate to axillary shoots; in sorghum, little assimilate was translocated to axillary shoots, while in maize this activity was completely absent.

Plant habit, as exemplified by the contrast between the annual, single‐axis maize plant and the perennial, multi‐tillering ryegrass plant, appears to be a reflexion of the pattern of assimilate distribution to areas of potential growth. With the exception of superior leaf assimilation rates in maize and sorghum, the four species showed no marked differences in respect of the production, transport and respiratory utilization of assimilates.
Factors affecting field‐scale production of seed of F1 hybrid Brussels sprouts
Authors: FAULKNER G. J.
Published: February 2008

The two main factors involved in field‐scale production of seed of F1 hybrid Brussels sprouts are pollen availability and honeybee behaviour. Pollen availability depends upon the extent of winter survival of the parent inbreds, their flowering times, plant size and on the number of flowers per plant. Plant losses varied between inbreds and between sites and seasons. Differences in the commencement of flowering time in pairs of inbreds varied from 7 to 21 days, and plant size affected flower number. In hybrid seed‐production there was a direct relationship between the number of mature flowers on each inbred and the percentage of non‐hybrid seed produced from that inbred.

Bees were highly selective in their visits to inbreds, and a mean selfing‐to crossing‐movement ratio of 30:1 was observed. This behaviour, together with pollen availability, greatly influenced the production of ‘sibs’.

Radioactive experiments showed that the amount of cross‐pollen carried by a bee decreased by about 30% at each flower visited but radioactive pollen grains were detected on the tenth flower visited. Of a number of factors investigated as possibly influencing bee behaviour, differences in flower colour and plant height were associated with discrimination between inbred lines.
The inheritance of resistance to Rhynchosporium secalis in some European spring barley cultivars
Authors: HABGOOD R. M.
Published: February 2008

The inheritance of partial resistance to Rhynchosporium secalis, which appears to be race non‐specific, was studied in a diverse range of European spring barley cultivars. Data from the F2 generation of a 6 × 6 diallel cross and the F3 generation of three crosses selected from this diallel set suggested that resistance was complex in inheritance, the results being incompatible with any hypothesis involving less than four genes. The F2 studies indicated that both dominant and recessive genes were active in conferring resistance, and that there were significant additive gene effects. Transgressive segregation occurred in all cross combinations in the F3 material. Consequently the alleles conferring resistance were not completely concentrated in the most resistant cultivar studied (cv. Proctor).

Heritability estimates obtained from F2 and F3 material suggested that field selection was of limited reliability, even when spreader drills were incorporated amongst the segregates. Single‐plant selection (in F2) was considered to be of little value, and the results of Fa head‐row tests would require confirmation by replicated tests in subsequent generations.
Host and environmental effects on post‐penetration development of Puccinia graminis avenae and P. coronata avenae
Authors: KOCHMAN J. K. , BROWN J. F.
Published: February 2008

After inoculation of Avena sterilis and the oat cultivars Algerian and Garry with Puccinia graminis avenae the time required for the eruption of pustules of the rust was markedly less at 30–35 than at 20–25 oC. In addition, the area of pustules and number of uredospores produced were significantly greater at 30–35 than at 20 oC. Peaks of uredospore production occurred between 12 and 22 days after inoculation.

In comparable experiments, the time required for pustules of P. coronata avenae to erupt, and the size of pustules, were relatively insensitive to change of temperature, although weight of uredospores produced was greater at 20 than at 30 oC. Peaks of uredospore production occurred between 14 and 18 days after inoculation.

Both rusts showed straight‐line relationships between pustule area and number of uredospores produced. The percentage of infection foci that developed into pustules was similar with both rusts and on all the oat cultivars examined. Both rusts produced susceptible reaction types on all the hosts tested.

Pustules of P. graminis avenae were smaller and fewer and generation time longer on cv. Garry than on cv. Algerian or Avena sterilis and the numbers of pustules per unit of inoculum of both rusts were greatest on Algerian, least on Garry. It is suggested that these quantitative differences in phases of the infection process contribute towards the ‘slow‐rusting’ reaction of cv. Garry.
The control of apple canker (Nectria galligena) in a young orchard with established infections
Authors: SWINBURNE T. R. , CARTWRIGHT J. , FLACK N. J. , BROWN AVERIL E.
Published: February 2008

In a factorial experiment on canker control the efficiency of phenylmercurie nitrate (PMN) applied at leaf fall, before bud burst or both was compared with the application of dodine, dithianon, triforine, thiabendazole, benomyl or carbendazim in May and June. Of the total number of cankers which developed in unsprayed trees 76–78% resulted from infections in April to August of each year of the experiment. Infection was reduced significantly by all of the fungicides applied in summer. Of these carbendazim was outstanding, controlling both summer and autumn infections. Sporulation throughout the summer was suppressed by carbendazim and to a lesser extent benomyl, but whereas the suppressant effect of carbendazim persisted until long after leaf fall that of benomyl was evident only until August. Dodine, dithianon, triforine and thiabendazole had no significant effect on spore production. Dithianon and dodine showed highest toxicity to the germination of Nectria galligena spores of all fungicides used in summer. All of the fungicides controlled apple scab (Venturia inaequalis) although thiabendazole was the least effective.

Autumn applications of PMN reduced canker incidence but their value alone was not as great as carbendazim, dithianon, benomyl or dodine applied in summer. PMN applied in spring reduced the number of cankers in trees receiving no other fungicides but tended to increase the incidence of infections, particularly in autumn, when used in conjunction with fungicides applied in May and June. PMN applied before bud burst reduced sporulation of N. galligena for a few weeks, after which production resumed and in late summer and autumn actually exceeded the controls. None of the fungicides had any direct effect on leaf fall.

Infection of the crotch and basal leaf scars was more common in summer than in autumn whereas infection of leaf scars above the basal region was more common in autumn than in summer. The rootstocks of many of the trees became infected via callus tissue associated with adventitious root development and this was controlled by the carbendazim treatment.
Testing potatoes bred from Solarium vernei for resistance to the white potato cyst‐nematode, Heterodera pallida
Authors: HOWARD H. W. , FULLER J. M.
Published: February 2008

Three clones of potatoes bred from Solanum vernei were tested for their resistance to the white potato cyst‐nematode, Heterodera pallida, both by root‐ball counts and by estimates of total cysts produced. Two susceptible clones were used as controls. Root‐ball counts suggested a higher degree of resistance than that based on total cysts produced. There were differences in pathogenicity between the two populations. The degree of resistance found was such that in practice the resistant clones would be best used in conjunction with nematicide treatment in a system of integrated control.
Fluctuations and regulation of wheat‐bulb fly populations at Rothamsted
Authors: RYAN M. F.
Published: February 2008

Four populations of the wheat‐bulb fly studied at Rothamsted incurred substantial and regulatory losses of larvae caused by food shortage. The following hypothesis is proposed to explain population changes of the fly. Fluctuations caused by weather are stabilized by density‐dependent larval mortality caused by food shortage. The effect of weather is, however, pervasive as it also affects food shortage by influencing the number of shoots available to larvae.
A rickettsia‐like organism associated with diseased white clover
Authors: MARKHAM P. G. , TOWNSEND R. , PLASKITT KITTY A.
Published: February 2008

Diseased white clovers (Trifolium repens), with symptoms similar to clover club leaf, were found in England. Electron microscopy of thin sections revealed rickettsia‐like organisms, 1–2 μm long by 0–2‐0‐3 μm diameter, in the phloem cells of these diseased plants. They were not present in healthy clover plants. At 23–30 °C the organisms multiplied rapidly and symptoms became more severe. After treatment with penicillin the organisms degenerated and plants showed remission of symptoms.
Ethylene control of growth in maize seedlings in relation to auxin metabolism
Authors: Malloch K. Rachel , Osborne Daphne J.
Published: February 2008

Although elongation growth is reduced by ethylene, swelling responses do not occur. Ethylene reduces neither transport nor metabolism of applied IAA in either mesocotyl or coleoptile. We propose that maintenance of high auxin levels within these tissues sustains polar transport and contributes to the relative insensitivity of maize to applied ethylene.
Ethylene and IAA transport in potato
Authors: Hillman J. R. , Fairhurst Valerie
Published: February 2008

It has been suggested that the regulation of plant growth by ethylene may involve modification of IAA transport. We have examined this theory and an account will be given of the effects of ethylene on lateral and longitudinal IAA transport in potato sprouts and stolons. The techniques employed included microautoradiography and a new micropipette injection system.
Ethylene and water stress
Authors: Hall M. A.
Published: February 2008

Like some other growth regulators, internal ethylene levels in plants fluctuate as a consequence of water stress and this phenomenon may be responsible for some of the developmental responses which result. Current work seeks to determine how internal ethylene levels are controlled, i.e. by biosynthesis, translocation, diffusion out of the plant or metabolism. The levels of other growth regulators in the same tissue are also being investigated in relation to the changes in internal ethylene.
The composition of the soil atmosphere in a barley mono‐cropping situation with and without tillage
Authors: Bell Margaret J. R. , Holmes J. C.
Published: February 2008

Weekly gas samples from two depths in a long term experiment were analysed in 1973 and 1974 for carbon dioxide, oxygen, nitrogen, methane and ethylene. An attempt will be made to relate the varying concentrations to soil series, soil moisture, rainfall and temperature. Ethylene has been detected on several occasions.
Ethylene and seed germination
Authors: Hall M. A.
Published: February 2008

Ethylene can break dormancy in a wide range of common weed species. Investigations of the phenomenology of this response have shown that there is a pronounced interaction between ethylene, light and other factors. The implications of these findings will be discussed in relation to the possibility of controlling weed seed germination in cultivated areas.