bluuebunny/crossref_metadata_2025 huggingface dataset:
Fixation and transfer of nitrogen in a white clover‐grass sward under hill conditions
Authors: HAYSTEAD A. , MARRIOTT CAROL
Published: February 2008

Experiments are described to illustrate the different effect of defoliation and diurnal changes in light intensity and temperature on grazed white clover (Trifolium repens) ecotypes and pot grown clover. Removing all the fully expanded leaves from grazed clover has no effect on nodule numbers or on nitrogen fixing activity during the phase of early season rapid growth. No diurnal rhythm in nitrogen fixing activity is apparent in grazed clover swards. Isotope dilution experiments demonstrate that in the first half of the growing season underground transfer of nitrogen is low in cut plots in a previously grazed hill situation. The results are briefly described in the context of improved hill pasture utilisation.
A reappraisal of flight regulation in the green spruce aphid, Elatobium abietinum
Authors: PARRY W. H.
Published: February 2008

Alate formation and its importance in the population dynamics of Elatobium abietinum is examined. It is concluded that alate formation is related to high soluble nitrogen levels in Sitka spruce needles. In N.E. Scotland the proportion of the population developing as alatae was related to aphid density. The apparently differing status of alatae in S. England may be related to differences in the physiology of the host caused by heat input. In Scotland alate formation may cause a decline in spruce aphid populations when densities are very high but, at the densities normally encountered in Scotland and Germany only small proportions of the populations become alate. In these areas the population collapses in late June or early July occur in response to low soluble nitrogen levels in the spruce needles. The role of alate adults in the formation of new colonies following migration to uncolonised hosts is discussed.
Experiments with foliar sprays of thiabendazole and captafol for control of potato gangrene
Authors: LOGAN C. , COPELAND R. B. , LITTLE G.
Published: February 2008

In an experiment designed to measure the effect of foliar sprays of fungicides on gangrene in stored tubers thiabendazole but not captafol reduced yield by 30%. Although both fungicides reduced disease incidence in stems and tubers the extent of the reduction was so small that foliar sprays were considered unimportant as a method of control. Sprays of thiabendazole and captafol applied to the haulm 1 wk or 1 wk and 2 wk after desiccation did not reduce the incidence of gangrene in storage.
The reactions of swede (Brassica napus) to infection by turnip mosaic virus
Authors: TOMLINSON J. A. , WARD C. M.
Published: February 2008

Turnip mosiac virus (TuMV) and cucumber mosaic virus (CMV) were the only viruses commonly isolated from naturally diseased swedes (Brassica napus) showing leaf mosaic and leaf and root necrosis. Only TuMV caused these symptoms when re‐inoculated to swede. TuMV‐infected plants showed a severe loss in leaf (55%) and root (63%) fresh weight after 140 days.

Systemic leaf symptoms in infected swede plants varied greatly, but were predominantly necrotic (N) or mosaic (M). Plants were classified into one of seven reaction classes ranging from slight or severe necrosis, and mosaics with and without slight veinal necrosis. Swede cultivars differed markedly in their reaction to TuMV and contained different proportions of N‐ or M‐reacting plants. The reactions of progeny of four resistant cv. Bangholm plants were separately inherited; progeny of two plants reacting either symptomlessly or necrotically and those of the other two plants developing mosaic symptoms only.

Five isolates of TuMV from swede crops in different regions caused similar reactions but differed in virulence in the progeny of a self‐pollinated resistant swede plant.
Physiological studies of a hybrid between populations of Dactylis glomerata from contrasting climatic regions. II. Intra population variation
Authors: EAGLES C. F. , Othman OMAR B.
Published: February 2008

Considerable intra‐population variation was found for leaf expansion characteristics of three populations of Dactylis glomerata grown in a cool glasshouse during winter. The rates of leaf area expansion of a winter‐dormant population of North European origin were very low, while a colchicine‐induced autotetraploid of a winter‐growing Portuguese population had high rates. The progeny of a cross between these two populations had intermediate rates with a population mean significantly different from the mean rates of its parents. Some of the individual hybrid plants had rates greater than the mean rate of the Portuguese parent and selections were made based on these plants with the aim of improving the rate of leaf area expansion of the hybrid under winter conditions. Some of the F1 polycross progenies from the first cycle of selection showed a marked improvement with mean rates of leaf area expansion for certain maternal lines approaching the mean rate of the Portuguese parent.
Electrophoretic detection of the internal parasite, Aphidius matricariae in Myzus persicae
Authors: WOOL DAVID , EMDEN H. F. VAN , BUNTING S. W.
Published: February 2008

The presence of the internal parasite (Aphidius matricariae) of the aphid Myzus persicae can be identified by electrophoresis, and staining of several enzyme systems, of which malate dehydrogenase is recommended as the most reliable. It is suggested that the technique could be extended to other small insects, and that pest populations can be screened for percentage parasitism as an adjunct to insecticide and integrated control field trials.
Supercooling of Myzus persicae in relation to gut content
Authors: PARRY W. H.
Published: February 2008

The supercooling distribution curves of Myzus persicae varied in response to feeding position, diet and age. Unfed instar I aphids supercooled to temperatures lower than –20 °C. Feeding aphids supercooled to higher temperatures, the earlier instars on subsidiary veins supercooling to lower temperatures than the late instars and adults on the main veins. Starvation decreased supercooling ability in some adult aphids. The supercooling ability of aphids feeding on sucrose solutions through a Parafilm membrane decreased in response to an increasing concentration, the position being reversed on 25% sucrose. Varying the amino acid concentration had no effect. The possible effects of this variable supercooling ability on the winter survival of the aphid are discussed.
Relationships between the severity of leaf blotch (Rhynchosporium secalis) and the water‐soluble carbohydrate and nitrogen contents of barley plants
Authors: JENKYN J. F. , GRIFFITHS ELLIS
Published: February 2008

Water‐soluble carbohydrate (WSC) and total nitrogen (N) contents of leaves of field‐grown barley plants were measured in 1966 and 1967. Consistent differences were found between cultivars.

The susceptibility of cultivars to leaf blotch was correlated negatively with WSC content and positively with N content at G.S. 10.4. Application of nitrogen fertiliser (which increased N and decreased WSC) also increased the severity of leaf blotch.

The occurrence of primary lesions on seedlings does not seem to be affected by their WSC and N contents and the relation between WSC and N contents of leaves and severity of leaf blotch possibly depends on differences in growth and sporulation of the pathogen on substrates containing different amounts of carbohydrate and nitrogen.
Effect of some fungicides on the yield of grass swards
Authors: MALONE J. P. , McGIMPSEY H. C. , MCILWAINE R. S. , BINNIE R. C.
Published: February 2008

When benomyl, drazoxolon, thiabendazole or zineb were applied as soil drenches to established grassland drazoxolon reduced the incidence of rhizoplane fungi. Benomyl and thiabendazole significantly increased yield at one harvest but only benomyl had a significant effect on total yield. When benomyl was applied at monthly intervals from March to July significant increases in total yield were obtained with the June applications which also significantly increased yield at the first harvest in the following year. Repeated applications from March to July also had a significant residual effect on total yield. Yield increases were not significantly affected by increasing the benomyl level from 2.5 to 5.0 g/m2.
Arracacha virus A, a newly recognised virus infecting arracacha (Arracacia xanthorrhiza; Umbelliferae) in the Peruvian Andes
Authors: JONES R. A. C. , KENTEN R. H.
Published: February 2008

Arracacha virus A (AVA), a previously undescribed virus, is common in arracacha (Arracacia xanthorrhiza; Umbelliferae) in the Huanuco region of the Peruvian Andes. AVA was not transmitted by Myzus persicae, but was transmitted by inoculation of sap to 38 species from 10 families out of 63 species from 12 families tested. AVA was best propagated and assayed in Chenopodium quinoa and Nicotiana clevelandii in which it caused severe diseases. Sap from infected C. quinoa was occasionally infective after dilution to 10‐4 but not 10‐5, after 10 min at 65 °C but not 70 °C, and after 15 days at 20 °C.

In neutral phosphotungstate, AVA has isometric particles c. 26 nm in diameter with a hexagonal profile, some of which were either fully or partially penetrated by the negative stain. Up to 50–200 E2601cm units of purified virus was obtained from 1 kg of infected N. clevelandii leaf by extraction in 0.05 M phosphate buffer at pH 7.5 containing 0.05 M ethylene diaminetetra‐acetate, and clarification with chloroform, followed by differential precipitation with ammonium sulphate and three cycles of differential centrifugation. Purified virus sedimented as three components with sedimentation coefficients (S20w°) of 50 S, 92 S and 125 S and E260/E280 ratios of 0.65, 1.50 and 1.85 respectively. At equilibrium in CsCl gradients, buoyant densities of the 50, 92 and 125 S components were 1.32, 1.45 and 1.52 g/cm3 respectively. From the sedimentation coefficients and buoyant densities, the nucleic acid contents of the 92 S and 125 S components were estimated at 30–35% and 43–44% respectively. Only the 125 S component seemed to be infective but its infectivity was greater when mixed with the 92 S component. All three components contained a single protein with a molecular weight of 53 000. AVA was not serologically related to any of 33 other morphologically similar viruses. Although the vector is unknown, its properties suggest that it is a member of the nepovirus group.

The cryptogram of AVA is */*: */43–44 +*/30–35: S/S:S/*.
The effect of herbicides on the root system of wheat plants
Authors: TOTTMAN D. R. , DAVIES E. LI. P.
Published: February 2008

Three commercial herbicides, at the rates normally recommended for selective weed control in cereal crops, deformed the roots of spring wheat plants grown in sand culture. Affected roots produced large numbers of short swollen lateral branches which later grew on to form tassel‐like bundles of side roots. Only the mecoprop and MCPA components of the mixtures were responsible for the deformities; ioxynil and dicamba had no effect. Mecoprop applied to the rooting medium severely deformed the roots but foliar application also resulted in some abnormalities. The effects of the herbicides on root and shoot dry weights were not correlated with their deformative effects.
Studies on plant growth‐regulating substances LV. The Plant growth‐promoting properties of some β‐aryl‐propionic acids
Authors: CHAMBERLAIN K. , WAIN R. L.
Published: February 2008

A series of 17 β‐arylpropionic acids were synthesised and examined for plant growth‐regulating activity in wheat and pea tests. The results are discussed in relation to chemical structure. The activity of β‐(2, 4‐dichlorophenyl)propionic acid was compared with those of the 2, 4‐dichloro‐derivatives of phenoxyacetic, phenyithioacetic and phenylimino acetic acids using the same tests. When wheat coleoptiles or pea stem tissues were incubated with solutions of β‐(2, 4‐dichlorophenyl)propionic acid no chromatographic evidence of β‐oxidation of the side chain or other type of degradation was obtained.
Production and distribution of dry matter in maize following changes in plant population after flowering
Authors: H.WILSON J. , ALLISON J. C. S.
Published: February 2008

Maize plants were grown singly in pots in a population of 3.7 plants m‐2, and 98 days after sowing (shortly after flowering) were arranged into three populations, 1.27 (W), 3.70 (M), and 6.15 (C) plants m‐2, respectively. The plants were harvested 131 days after sowing, about 4 wk before the normal time of maturity, because some plants at the closest spacing began dying.

Increment of dry weight between days 98 and 131 was 373, 243, and 108 g/plant and grain dry weight at harvest was 218, 220 and 195 g/plant in populations W, M and C, respectively. Thus, dry weight of parts of the plant other than grain increased in population W, remained about the same in population M, and decreased in population C between days 98 and 131. Number of kernels per plant was c. 540 in all three populations. On day 98, immediately after rearrangement, leaf area index (L) was 2.0, 5.8 and 9.7 in populations W, M and C, respectively. By day 131 L had decreased to 6.7 in population C, but had hardly changed in the other two populations. Crop growth rate between days 98 and 131 was 101, 191 and 141 g m‐2 wk‐1, and grain dry wt per unit of land on day 131 was 277, 816 and 1196 g m‐2, in populations W, M and C, respectively.
Effect of plant population on ear differentiation and growth in maize
Authors: WILSON J. H. , ALLISON J. C. S.
Published: February 2008

Maize was grown at 2.47, 3.70 and 4.94 plants m‐2. Ears were apparently initiated about 2 days later in the densest than in the least dense population, but rate of formation and final number of female floret primordia per row of the ear were similar in the two populations. In the densest population fewer primordia produced fully developed florets than in the least dense population and of those that were produced fewer extruded silks before pollen shedding ceased. Relative growth rates of dry mass and of length of the ear before flowering were unaffected by density, but with the apparent later start of ear growth in the densest population ears were lighter and shorter than in the least dense population.

Number of florets per row of the ear at the time of flowering decreased slightly with increase in population. Number of kernels per row decreased with time after flowering, especially in the densest population. At final harvest size and mass per kernel, number of kernels per ear, length and circumference of the rachis, and space per kernel on the rachis all decreased with increase in population.

Thinning the intermediate population at various times from shortly before flowering until near final harvest increased mass of grain and shoot, and number of kernels of the remaining plants at final harvest. The extent of the increases decreased progressively the later the thinning. Mass and volume per kernel were increased by thinnings done up to the time of flowering, but were unaffected by thinning from c. 16 days after flowering.
Survival of mature larvae of codling moth (Cydia pomonella) on apple trees and ground
Authors: GLEN D. M. , MILSOM N. F.
Published: February 2008

The effects of predation by carabid and staphylinid beetles and birds (blue‐ and great‐tits) on mature larvae of the codling moth Cydia pomonella were investigated in a field experiment. The number of predatory beetles on the ground beneath eight of 16 apple trees was reduced by an insecticide spray, and tits were excluded from the trunks and lower branches of eight trees by means of Terylene netting. Beetles had no significant effect on survival of larvae on trees, but only 8% of larvae survived to adulthood on trees exposed to blue‐ and great‐tits, whereas on trees protected from them 48% survived. Larvae were taken rapidly by the tits from the time larvae first built cocoons in summer and, by the time the majority of larvae had emerged from apples in late summer or autumn, tits had removed most from cocoons beneath flakes of bark glued to trees. Thus tits fed on larvae mainly in summer and autumn. On trees protected from tits, 8% of mature larvae were killed by fungi, of which Verticillium lecanii was most important. It was calculated that, of the larvae maturing in apples, 44% failed to build cocoons on the trees, 47% were taken by tits, then 1% were killed by fungi. Larvae failing to build cocoons on trees may build them on the ground. Of larvae in cocoons planted on or in the ground in 1975, only one (0.3%) persisted through the winter; 98.6% disappeared, and 1.1% were found dead, covered by fungi; in 1976, all larvae disappeared by December. Larvae disappeared even in the absence of predators, and are thought to have moved in response to damp ground conditions.
Epidemiology of maize rust, Puccinia sorghi
Authors: MAHINDAPALA R.
Published: February 2008

The development and spread of maize rust from an inoculated circular plot was studied during 1975. Results from a Burkard volumetric spore trap sited in the centre of the inoculated plot showed that the daily peak urediniospore concentration in the atmosphere occurred at about 1300 h. During the season atmospheric urediniospore concentration increased to a plateau and later decreased mainly through lack of host material.

The spread of the pathogen away from the inoculated plot was related to the increase in atmospheric urediniospore concentration and warm temperatures. Disease gradients along the eight major compass directions demonstrated the influence of wind on the spread of the pathogen. As the season progressed gradients tended to flatten because of secondary spread of the pathogen.
Some effects of applied sodium and potassium chloride on yellow rust in winter wheat
Authors: RUSSELL G. E.
Published: February 2008

In glasshouse experiments with plants in pots, applications of potassium chloride to the soil at 0.5 g/plant, 4 days before inoculation with Puccinia striiformis, decreased the severity of yellow rust on several winter wheat cultivars in comparison with untreated plants. Conversely, yellow rust was encouraged by applications of sodium nitrate. Sodium chloride in solution (8.6 g/l) reduced yellow rust when applied to the soil at the rate of 20 ml/plant but not when it was sprayed on to the leaves.

In small‐plot field experiments, sodium and potassium chlorides applied to the soil as dry powders in the spring at rates of 376, 1130 or 2260 kg/ha, significantly decreased the severity of yellow rust on most of the winter wheat cvs examined at each rate. The chlorides at these rates did not adversely affect the overall growth or yield in the absence of yellow rust.
Soil factors influencing chlamydospore formation by Fusarium solani f. sp. phaseoli
Authors: BANDARA J. M. R. S. , WOOD R. K. S.
Published: February 2008

Gel filtration and chromatographic separation of soil extracts gave three fractions which induced formation of chlamydospores by Fusarium solani f. sp. phaseoli. Depletion of nutrients had a similar effect.
Persistence of Phoma exigua xar. foveata and Polyscytalum pustulans in dry soils from potato stores in relation to reinfection of stocks derived from stem cuttings
Authors: CARNEGIE S. F. , ADAM JESSIE W. , SYMONDS CAROL
Published: February 2008

The incidence of Phoma exigua var. foveata and Polyscytalum pustulans in dry soil and dust from potato stores was assessed at 10 farms in Scotland producing virus‐tested stocks of seed potatoes derived from stem cuttings (VTSC). Samples were collected on three occasions during 1976: during the storage period (February‐March), soon after the potatoes were planted (May) and just before the new crop was lifted and stored (August‐October). Both pathogens were detected at all three sampling times but P. exigua var. foveata was more frequently detected at the last one than P. pustulans. Soil and dust from various sites within the stores, such as floors, ledges, graders and boxes, were contaminated by these pathogens. Propagules of both pathogens remained airborne for at least 12–17 min after the floors were swept.

P. exigua var. foveata remained viable for at least 16 months in dry soil from tuber surfaces stored at 4–6°C. When VTSC tubers were dusted before planting with a dry store soil contaminated by P. exigua var. foveata the gangrene potential of the progeny tubers was much greater than that from untreated tubers or from tubers treated with an uncontaminated soil. The role of inoculum surviving in dry soil is discussed in relation to reinfection of VTSC stocks.
Some hosts, properties and possible affinities of a labile virus from Hypochoeris radicata (Compositae)
Authors: BRUNT A. A. , STACE‐SMITH R.
Published: February 2008

Hypochoeris mosaic virus (HMV) is common in Hypochoeris radicata (‘cat's ear’) in western Canada. It infected 10 of 53 mechanically inoculated species in five of twelve families, but was not transmitted by aphids or through seed or soil. Sap from infected Nicotiana clevelandii was sometimes infective after dilution to 10‐1 and occasionally 102, after 10 min at 45 but not 50°C, and after 1 but not 2 days at 20°C. Infectivity of crude nucleic acid extracts from infected leaves was rapidly abolished by RNase but not by DNase.

Host sap contained very few rod‐shaped particles or particle fragments mostly 21.0–22.5 nm in diameter, and up to 420 nm long but with predominant lengths of 120–140 and 240–260 nm. Many rods in purified virus preparations were less than 240 nm long, and the majority were c. 140 nm or shorter. The particles had a helical substructure with a pitch of 2.58 nm and contained a single type of protein of estimated mol. wt 24.5 × 103.

HMV showed no serological relationship to eight morphologically similar viruses (beet necrotic yellow vein, broad bean necrosis, barley stripe mosaic, peanut clump, potato mop‐top, Nicotiana velutina mosaic, wheat soil‐borne mosaic and defective strains of tobacco mosaic). It is probably a hitherto undescribed tobamovirus.
The detection of plum pox virus in Prunus species by enzyme‐linked immunosorbent assay (ELISA)
Authors: ADAMS A. N.
Published: February 2008

Plum pox virus (PPV) was detected by ELISA throughout the year in extracts of root, bark, fruit, flowers and leaves of Prunus species; extracts from healthy plants gave negligible background reactions. In the summer, ELISA values obtained with extracts from infected leaves were variable but samples extracted at 1:50 (w/v) could have been diluted a further five to 110 times before reaching the limit of detection. Using a single antiserum the virus was detected in several hundred trees, suggesting that there was little antigenic variation.

PPV was unevenly distributed in leaves and shoots and commonly occurred in only a few branches of an infected tree although it was frequently present in suckers growing from the roots. Virus was detected in the only three trees known to be infected in random leaf samples taken from 530 1‐yr‐old trees, but some infected trees were missed in samples taken from older trees and from a 7‐yr‐old rootstock hedge. The main practical use of ELISA for PPV is therefore as a sensitive and highly reliable confirmatory test which greatly facilitates control of the disease by the prompt destruction of infected trees.
Studies on mutagenesis and cross‐protection of cauliflower mosaic virus
Authors: TOMLINSON J. A. , SHEPHERD R. J.
Published: February 2008

Three strains of cauliflower mosaic virus (CaMV) designated NVRS, CM4‐184 and PK caused respectively severe, moderate and mild reactions in turnip cv. Just Right plants and severe, mild and symptomless reactions in Brussels sprout cv. Fasolt plants.

Chlorotic local lesions formed consistently in the leaves of young turnip plants when inoculated with each of the virus strains. Lesions were suitable for infectivity assay of crude and purified preparations of the virus.

Three variants of the NVRS strain were isolated by single‐lesion transfer after treatment of the virus with nitrous acid (pH 5.0) and two variants were obtained after treating the virus in acetate buffer at the same pH. One of the variants (designated V3) caused symptomless infection in turnip and Brussels sprout plants.

In cross‐protection tests, Brussels sprout plants infected symptomlessly with the PK, CM4‐184 or the V3 strains, subsequently resisted infection by the severe NVRS strain.
The effects of dehydration on freezing injury in a range of carrot cultivars
Authors: TUCKER W. G. , COX C. J.
Published: February 2008

Carrot cultivars given a mild freezing treatment (–2.5°C for 16 h) showed significant differences in the amounts of external and internal ice formed and in the amounts of electrolytes diffusing from broken tissues after thawing. Dehydrating the carrots in vitro up to 9% loss of fresh weight decreased the formation of external ice in all cultivars but decreased internal ice formation only in the Chantenay and Autumn King cvs; internal ice formation in the Amsterdam Forcing cv. was unaffected by up to a 7% loss of fresh weight. Of the cultivars tested, the Chantenay cv. withstood the freezing treatments best and the Amsterdam Forcing cv. the least with the Autumn King cv. intermediate between the two. There was no indication of cold hardiness by a natural adjustment of the water content of the carrots in the field during the winter in any cultivar.
Effects of inoculation with Septoria nodorum on yield components of spring wheat
Authors: WAFFORD J. D. , WHITBREAD R.
Published: February 2008

Spring wheat, cv. Kolibri, was artificially inoculated with spore suspensions of Septoria nodorum, from the time of full expansion of the third leaf to the end of flowering and the effect on yield components recorded. Most components were reduced by increasing severity of infection and grain weight losses of 56 and 35% were produced on single‐stemmed and tillering plants respectively, by the most severe infection. The effects on components of yield differed considerably between the main stems and the tillers and an increase in grain number on moderately infected tillers partly compensated for reductions in yield on the main stem.
Growth of broad beans infected by Uromyces viciae‐fabae
Authors: WILLIAMS P. F.
Published: February 2008

The effect of artificially regulating the level of a rust infection with Uromyces viciae‐fabae (Pers.) Schroet. on the growth and yield of two cultivars of Viciafaba L. (broad beans) was examined in 1973/74.

Disease decreased leaf area ratio without increasing net assimilation rate particularly during the stage of ‘pod filling’. Consequently, assimilate supply to developing beans was diminished and the weight of beans per pod and yield of beans per plant decreased.

This is unlike the effect of Botrytis fabae Sard, on broad beans which reduces yield by decreasing the number of pods per plant. This suggests that the two leaf spotting pathogens decrease yield in different ways and so may require different approaches to minimise yield losses.
The interaction between mushroom strains and fungicides in the control of dry bubble disease caused by Verticilliumfungicola
Authors: GANDY DOREEN G. , SPENCER D. M.
Published: February 2008

Five fungicides were compared for control of Verticilliumfungicola on six strains of the cultivated mushroom. The strains showed considerable differences both in their sensitivity to the fungicides and their susceptibility to infection. These factors complicated comparison of the fungicides, but benodanil was less effective than chlorothalonil against V. fungicola.
The use of enzyme‐linked immunosorbent assay to detect, and discriminate between, small iridescent viruses
Authors: KELLY D. C. , EDWARDS MARY‐L. , ROBERTSON J. S.
Published: February 2008

The enzyme‐linked immunosorbent assay (ELISA) double antibody method provided an efficient method for detecting iridescent virus (type 22) in purified preparations and extracts of Galleria mellonella larvae; 10 ng of purified virus/ml were detected with confidence. The ELISA method discriminated between the five iridescent viruses tested.
Rapid detection and serotyping of prunus necrotic ringspot virus in perennial crops by enzyme‐linked immunosorbent assay
Authors: BARBARA D. J. , CLARK M. F. , THRESH J. M. , CASPER R.
Published: February 2008

Strains of prunus necrotic ringspot virus (NRSV) in hop and plum cultivars were rapidly and conveniently detected and serotyped by enzyme‐linked immunosorbent assay. Antisera produced against the G isolate of NRSV from cherry and the Paradise isolate of apple mosaic virus (ApMV) from apple were used concurrently to ensure detection of all serotypes and to differentiate between them. Both NRSV and ApMV serotypes occurred in plum either as single or mixed infections. By contrast, the NRSV serotype was not found in hop, which contained either ApMV or a serotype intermediate between NRSV and ApMV.
A comparison of the rate of drying of four nematode species using a liquid paraffin technique
Authors: WOMERSLEY CHRISTOPHER
Published: February 2008

A technique of immersion refractometry has been employed to compare the rates at which four species of nematodes lose water during desiccation at 0% r.h. Panagrellus redivivus and Ditylenchus myceliophagus showed little ability to control water loss, although in the latter species coiling helped slow the rate of drying. Ditylenchus dipsaci and Anguina tritici exhibited a much greater degree of control over water loss during desiccation, A. tritici being more successful. D. dipsaci revived from ‘wool’ showed a marked decrease in ability to control water loss when compared with freshly extracted worms. The results obtained have been compared with those from work using interference microscopy, and a critical assessment of the liquid paraffin technique is presented.
Healthier seed potatoes. I. Effects of inoculating stem cutting stocks with Polyscytalum pustulans and Rhizoctonia solani on growth, yield and disease
Authors: HIDE G. A. , BELL F.
Published: February 2008

Potato seed tubers of seven cultivars derived from stem cuttings in 1965 (healthier seed) were grown in 1969–72 at two sites, one clay with flints soil (Rothamsted) and the other sandy loam soil (Woburn). Inoculating sprouted tubers at planting with Polyscytalum pustulans did not affect the number of stems/plant or total yield but increased stem base and tuber infection. The yields of large tubers (57–83 cm) were increased and small tubers (>57 cm) decreased, indicating a decrease in tuber numbers.

Rhizoctonia solani inoculated at planting decreased numbers of stems/plant and yield by up to 14% at Woburn but not at Rothamsted. At both sites, yields of large tubers were increased with cvs Majestic and Record and decreased with Pentland Crown. Stem canker and tuber infection were increased but infection was also prevalent on tubers from non‐inoculated seed at Woburn.

When both pathogens were inoculated together yields of large tubers were increased in cvs King Edward, Majestic and Record and decreased in Pentland Crown. Infection of stem bases and tubers was sometimes less than when either pathogen was inoculated singly.
Healthier seed potatoes. II. Effects of sprouting and benomyl treatment of stem cutting and commercial stocks on growth, yield and disease
Authors: HIDE G. A. , BELL F.
Published: February 2008

Potato seed tubers of seven cultivars derived from stem cuttings in 1965 (healthier seed) were compared with samples from commercial stocks in 1969–72 at two sites, one clay with flints soil (Rothamsted) and the other sandy loam soil (Woburn). Plant emergence, usually slower from non‐sprouted seed, was unaffected by seed source or seed treatment with benomyl. Sprouted healthier seed produced more stems/plant than sprouted commercial seed.

Healthier seed yielded 6% (Rothamsted 5%, Woburn 8%) more than commercial when seed was sprouted and 7% (Rothamsted 6%, Woburn 9%) when not sprouted. The increased yields of cvs Record (10% sprouted, 23% not sprouted), Majestic (8% sprouted, 11% not sprouted) and King Edward (5% not sprouted) mostly comprised small ware (44–57 cm) and chats (>44 cm), indicating an increase in tuber numbers. Commercial Pentland Crown seed yielded as much as healthier but the healthier produced less large ware (57–83 cm). Benomyl treatment of commercial seed, especially when not sprouted, and sometimes of healthier seed also decreased tuber size.

Infection of stem bases and tuber eyes by Polyscytalum pustulans was less from healthier than commercial seed and was decreased by benomyl. Stem canker (Rhizoctonia solani) was also decreased by benomyl but fungicide treatment of seed did not greatly decrease the high incidence of R. solani hyphae on eyes of tubers at Woburn. Helminthosporium solani, equally prevalent on the produce of commercial and healthier seed, was decreased by benomyl. There was slightly more gangrene (Phoma exigua) on the produce of commercial than healthier seed.
Effects of air temperature on seed growth and maturation in cowpea (Vigna unguiculata)
Authors: ROBERTS E. H. , SUMMERFIELD R. J. , MINCHM F. R. , STEWART KATRINE A. , STEWART W. , NDUNGURU B. J.
Published: February 2008

This investigation has attempted to quantify the effects of air temperature on seedgrowth in cowpea independent of phenology and other major ontogenetic changes inthe physiology of the parent plant. Fruits produced in identical positions on the mainstem of plants (which, in three of the four environments tested, were almost identicalin dry weight and morphology at the onset of flowering) were harvested at regularintervals after anthesis. Four day‐night temperature regimes (mean values inparentheses) were investigated: 33‐24 C (283 C); 33‐19 C (256 C); 27‐24 C (254 C) and 27‐19 C (228 C). Overall, the mean dry weight ofindividual seeds contained in the first fruit produced in the coolest regime was morethan double that recorded in the warmest environment, with the two intermediateregimes giving intermediate but similar results to each other. These final weightswere brought about by almost identical durations of the linear phase of increase indry weight (about 9 days) in the three warmer regimes but a longer duration (about 11 days) in the coolest regime, while the rates of increase in dry weight during thisphase were identical in the three cooler regimes (about 13 mg seed‐1 day‐1) butconsiderably less in the warmest environment (about 10 mg seed‐1 day‐1). Attributes of the first formed fruits are compared with ‘average’ fruits in eachenvironment and implications of these data in legume physiology and breeding are discussed.
Viruses occurring in East Africa that are related to peanut mottle virus
Authors: Bock K. R. , Guthrie E. J. , Meredith Gina
Published: February 2008

Viruses occurring in Cassia bicapsularis in Northern Tanzania, in Voandzeia subterranea in north western and eastern Tanzania, and in Phaseolus lunatus in the Kenya highlands, were all serologically related to peanut mottle virus. Their host ranges, and the symptoms they induced in test plants, were very similar, and they differed only in degree of virulence in some host species.

The Voandzeia isolate did not infect groundnut, and only the Phaseolus isolate infected two species in the Cucurbitaceae. All the isolates infected Chenopodium amaranticolor, a species which formerly was reported as being immune to peanut mottle and thus considered of diagnostic value.

In Africa, variation in peanut mottle virus isolates seems to be associated with host species and ecology, and there is at present no evidence for naturally occurring variants within a host species as occurs in groundnut in America.

Three of the four isolates were purified by homogenising together infected leaf tissue, chloroform and 0.5 M sodium citrate buffer containing 1% 2‐mercapto‐ethanol at pH 8, in the proportion 1: 1:2 respectively, and precipitating the virus from the clarified homogenate with 5% w/v polyethylene glycol. When centrifuged in sucrose density gradients such preparations gave a single, bright specific light scat‐tering zone with no haze.
Decreased severity of ryegrass mosaic virus after passage through resistant perennial ryegrass
Authors: WILKINS P. W.
Published: February 2008

After exposure to infection in the field, the proportion of plants showing distinct symptoms of ryegrass mosaic virus (RMV) was less in perennial than in Italian ryegrass. The perennial ryegrass cv. Mascot had a smaller proportion of plants with symptoms than cv. S.23. Far milder symptoms were induced in test plants by RMV from naturally infected perennial ryegrass plots than from Italian ryegrass plots. Within perennial ryegrass, RMV from cv. Mascot caused milder symptoms than that from cv. S.23. Severe RMV isolated from Italian ryegrass cv. Trident (RMVT) became milder after one passage through cv. Mascot, although not as mild as RMV obtained from field plots of cv. Mascot (RMVM).

Families from two highly resistant perennial ryegrass clones and two randomly selected clones of cv. S.23 crossed in all possible combinations varied in symptom severity when inoculated with RMVT but not when inoculated with RMVM. Families inoculated with RMVT also yielded virus which varied in the severity of symptoms induced in test plants, families with severe symptoms yielding severer virus. Thus, much of the variation in the resistance of these clones could be attributed to infection with RMV of differing severity. Resistance was controlled by several genes which were mainly additive in their effect.
The relative efficiency of foliar sprays and granular insecticides in control of the jassid Empoasca lybica on eggplant
Authors: Kisha Jennifer S. A.
Published: February 2008

Omethoate, formothion, monocrotophos and carbaryl were the most effective of a number of insecticides evaluated as foliar sprays for the control of Empoasca lybica on eggplant. The duration of insecticidal activity was about 20 days, three sprays being required during the season.

Disulfoton, carbofuran and terbufos granules applied to the soil at the rate of 0.1 g a.i./plant c. 1 month after transplanting gave control of jassid throughout the season and a significant yield response.
The effects of herbicides, applied atone and in sequence, on the control of wild‐oats (Avena fatua) and broad‐leaved weeds, and on yield of winter wheat
Authors: Wilson B. J. , Cussans G. W.
Published: February 2008

Experiments were done to examine the effects of controlling wild‐oats and autumn‐germinating broad‐leaved weeds in winter wheat, early in winter or late in spring. The herbicides used were barban (winter), chlortoluron or isoproturon (winter), and benzoylprop‐ethyl, at the recommended doses and at half doses. Sequential treatments of two herbicides at half doses were also examined. All treatments were given a routine broad‐leaved herbicide treatment in spring.

Yields of wheat were influenced more by the time of weed removal than by the degree of control achieved. Grain yields at three sites with dense autumn broad‐leaved weed populations were greatest following the use of chlortoluron or isoproturon. At three other sites with moderate to dense wild‐oat populations (60 to 240 plants/m1), the use of barban at the crop three‐leaf stage gave larger yields than benzoylprop‐ethyl in late spring at the early stem elongation stage of the crop. Seed formation from surviving A. fatua was similar with both wild‐oat herbicides. The treatment which reduced seed production of A. fatua and maintained crop yield most consistently was barban followed by benzoylprop‐ethyl, each at half the normal recommended dose.
Broomrape (Orobanche) seed germination inhibitors from plant roots
Authors: Whitney P. J.
Published: February 2008

Two species (tomato and cucumber) which are not hosts to Orobanche crenata but which are hosts to other species of Orobanche not only failed to produce the compound required to trigger O. crenata to germinate but produced germination inhibitors which stopped germination even in the presence of a suitable stimulant. This suggested the possibility of using germination inhibitors to control at least some species of Orobanche. The question whether host species produce inhibitors as well as stimulants has not however been resolved.
Studies on plant growth‐regulating substances. LIV. Factors affecting the production of active growth substances from structurally related amines in plants
Authors: Price R. , Wain R. L.
Published: February 2008

A diamine oxidase enzyme has been isolated from pea epicotyls and purified. The in vitro rates at which a number of amines, structurally related to plant growth substances, are oxidised by this enzyme have been measured. These rates when considered together with the growth regulating activity of the acid ultimately produced, enable an assessment of the activity of the amine as a hormone‐type herbicide to be made.
The restoration of male fertility in F1 wheat hybrids
Authors: Done A. A. , Whittington W. J.
Published: February 2008

The yield of F1 wheat hybrids is often limited by reduced male fertility. Improvement depends upon selecting male and female parents capable of allowing good fertility ‘restoration’ in the F1 hybrids. Assessment of restoring potential in growth rooms was difficult because fertility was much lower than in field grown plants. In the field, two experiments showed differences between parent lines but also that the fertilities of the F1 hybrids were site‐specific, and that this factor might be considered during further selection. Variation between reciprocal crosses, possibly due to cytoplasmic differences, rendered a proposed test for the early assessment of fertility restoration capacity amongst potential male‐sterile lines to be of doubtful value with present stocks.
Pre‐harvest germination in male‐sterile wheats
Authors: Done A.A. , Whittingtion W. J.
Published: February 2008

F1 hybrid grain borne on cytoplasmic male‐sterile (A line) parents germinated (sprouted) before maturity but grain set on male‐fertile analogues (B lines) of the A lines did not. Sprouting may involve varied with the pollinator and with the A lines although their ranking order varied between experiments. Unsprouted grain harvested from A lines subsequently germinated more rapidly than that from the B lines.
The early stages of mildew colony development on susceptible oats
Authors: CARVER T. L. W. , CARR A. J. H.
Published: February 2008

The chronology of primary infection by Erysiphe graminis f. sp. avenae on detached leaves of a susceptible host, and growth patterns of the primary haustorium and secondary hyphae, proved similar to those of wheat and barley mildew found by other workers. The timing of formation and subsequent growth of the primary haustorium was not affected by the light regime, but the formation of subsequent haustoria was highly synchronous under an alternating dark/light cycle, and far less so under continuous illumination. Five days after inoculation almost twice as many secondary and tertiary haustoria were formed per colony under the dark/light treatment than under continuous light.

Because of the synchronous formation of haustoria subsequent to the primary, haustoria selected at random from leaves of susceptible host cultivars showed a bimodal distribution in length, the less well developed tertiary haustoria being distinguished from earlier formed primary and secondary haustoria. There was also a significant positive correlation between length and the number of digitate processes/haustorium. The energy required to produce one secondary haustorium was calculated to be equivalent to that required to produce approximately 4–7 hyphal cells.
A bacteriophage specific to race 2 of the cherry strain of Pseudomonas morsprunorum
Authors: PERSLEY G. J. , CROSSE J. E.
Published: February 2008

The isolation and characterisation of a bacteriophage specific to the recently described race 2 of the cherry strain of Pseudomonas morsprunorum in England is described. The phage was subsequently used in a survey of P. morsprunorum races in commercial orchards and on the cherry cultivars Napoleon and Roundel at East Mailing Research Station.
Host range, purification and properties of potato virus T
Authors: SALAZAR L. F. , HARRISON B. D.
Published: February 2008

Potato virus T (PVT) infected nine species of tuber‐bearing Solanum, most of them symptomlessly, and as a rule was transmitted through the tubers to progeny plants: two genotypes of S. tuberosum ssp. andigena were not infected. The virus was also transmitted by inoculation with sap to 37 other species in eight plant families. Chenopodium amaranticolor is useful as an indicator host, C quinoa as a source of virus for purification, and Phaseolus vulgaris as a local‐lesion assay host; the systemic symptoms in Datura stramonium, Nicotiana debneyi and in these three species are useful for diagnosis. Attempts to transmit PVT by aphids failed, but the virus was transmitted through seed to progeny seedlings of four solanaceous species, and from pollen to seed of S. demissum.

PVT was purified by clarifying sap with n‐butanol or bentonite, followed by precipitation with polyethylene glycol, differential centrifugation and sedimentation in a sucrose density gradient. Purified preparations had an E260/E280 ratio of 1.18 and contained a single infective component with a sedimentation coefficient of 99 S. This component consisted of flexuous filamentous particles of about 640 times 12 nm that showed a characteristic substructure when stained with uranyl acetate. The virus particles contained a single species of infective single‐stranded RNA, of molecular weight 2–2 times 106 daltons, and a single species of polypeptide of molecular weight about 27 000 daltons.

PVT is serologically related to apple stem grooving virus but not to four other common potato viruses with flexuous filamentous particles. Apple stem grooving virus and PVT cause similar symptoms in several hosts, but also differ somewhat in host range and symptomatology. Apple stem grooving virus did not infect potato, caused additional symptoms in C. quinoa also infected with PVT, and its particles did not show the structural features specific to PVT. The two viruses are considered to be distinct. The cryptogram of PVT is R/1:2–2/(5): E/E: S/C.
The virulence characteristics of Bremia lactucae populations present in Sweden from 1971 to 1976
Authors: WELLVING A. , CRUTE I. R.
Published: February 2008

One hundred and four Swedish isolates of Bremia lactucae were tested between 1971 and 1976 for their virulence phenotypes. Eighty of these isolates showed patterns of virulence previously recorded in other countries while the remainder conformed to seven previously unreported virulence factor combinations. The simplest resistance factor combination that could give resistance to all isolates collected was R2 plus Rl 1.

This combination now exists in some recently bred lettuce cultivars. Most of the possible virulence factor combinations occurred in the population at the expected frequency. However, several combinations, which had not been directly selected (by the growing of cultivars carrying the comparable resistance factor combinations) were present at higher or lower than expected frequencies.
Studies on plant growth‐regulating substances
Authors: WILKINS SHEENA M. , WILKINS HENRY , WAIN R. L.
Published: February 2008

Roots of Pisum seedlings grown in a compact silt loam soil (bulk density 1–5 g/cm3) were shorter than those of seedlings grown in loose soil (bulk density 1 ? 1 g/cm3). Incorporating 3,5‐dibromo‐4‐hydroxybenzoic acid (DBHB)or 3,5‐dichloro‐4‐hydroxybenzoic acid (DCHB) into the compact soil enhanced root elongation and decreased root bending. DBHB was more effective than DCHB in promoting pea root growth but a much higher concentration was required for optimal activity. Shoot height was increased by DCHB treatment of the compact soil but DBHB had little effect. In loose soil, significant effects were detected only at high concentrations, when DBHB promoted and DCHB inhibited the root growth of pea seedlings.

Although development of barley seedlings in compact soil was enhanced by DCHB, that of wheat seedlings was inhibited by this treatment.