bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of imazalil in the control of decay in yellow yam caused by Penicillium sclerotigenum
Authors: PLUMBLEY R. A. , COX J. , KILMINSTER K. , THOMPSON A. K. , DONEGAN L.
Published: February 2008

A strain of Penicillium sclerotigenum isolated from decaying yellow yams (Dioscorea cayenensis) was found to have developed resistance to benzimidazole fungicides and the use of imazalil was investigated as an alternative agent for controlling it. Two formulations were tested and proved to be equally effective in controlling decay at a concentration of 50 mg imazalil litre‐1 if the yams were dipped in it for 5 s; concentrations down to 10 mg litre‐1 were effective if the immersion time was increased to 5 min or more. These treatments gave good control of decay when applied up to 24 h after inoculation but were less effective when application was 48 h after inoculation, although at 500 mg litre‐1 there was some indication that levels of decay were decreased when compared with untreated tubers. Fungal penetration was unaffected or increased by increasing delays in the time of the fungicide application depending on the concentration applied. In trial shipments of yams from Jamaica to Britain imazalil alone was less effective in controlling overall decay because of the presence of a Rhizopus species. This could be controlled by the addition of dichloran to the dip. Imazalil residues were highest in the peel; levels in the peeled tuber varied and tended to decrease during storage but were generally in the range of 0·5 ‐ 0·8 mg kg‐1 which is higher than the maximum levels accepted for other produce. A simple cooking test showed that residues in treated yam slices declined by about one third after boiling the slices in water for 45 min.
Field studies on the spread of African cassava mosaic
Authors: FARGETTE D. , FAUQUET C. , THOUVENEL J.‐C.
Published: February 2008

The spread of African cassava mosaic disease (ACMV) into healthy cassava fields was recorded at weekly intervals. In addition, 21 yellow water traps were placed in one field and the number of whiteflies caught was recorded twice a week. The number of Bemisia spp. feeding on cassava was also estimated. The results indicate that the pattern of disease spread is related to the pattern of infestation with Bemisia.

Airborne whiteflies carried by the south‐west prevailing wind alighted preferentially on cassava plants along the upwind edges (south and west borders) of the plantings. The pattern of incidence of mosaic disease resembled that of whiteflies. Along the SW‐NE diagonal, there was a gradient of disease incidence with a maximum at the SW corner block. Similar gradients occurred in three different fields and they were maintained throughout the 6‐month study, although gradually flattening with time. There were indications that the reservoirs both of the virus and of the vectors were located some distance upwind from the experimental fields.
A comparison of spike and spikelet survival in mainstem and tillers of barley
Authors: COTTRELL JOAN E. , EASTON RUTH H. , DALE J. E. , WADSWORTH ANGELA C. , ADAM JILL S. , CHILD R. D. , HOAD G. V.
Published: February 2008

Initiation and abortion of spikelet primordia on primary tillers and mainstem were compared for plants of spring barley, Maris Mink, sown on two sowing dates during 1983, in plots at the Scottish Crop Research Institute (SCRI) and at Long Ashton Research Station (LARS). Sowing date had no effect on the number of spikelets initiated on either mainstem or surviving tillers and many more spikelets were initiated on equivalent stems at LARS than at SCRI but more spikelets aborted at the former site. The final number of spikelets produced was eventually similar. Spikelet abortion was complete by anthesis and coincided with the period of rapid stem and rachis elongation and with the time over which tiller death occurred. Despite the fact that plants at SCRI produced fewer fertile tillers they outyielded those at LARS because much heavier grains were produced on the mainstem and tiller 1 of plants at the Scottish site. An interval of 2 wk between sowing had only small effects on the components of yield.
The role of the sheath tube in the development of expanding leaves in perennial ryegrass
Authors: WILSON RUTH E. , LAIDLAW A. S.
Published: February 2008

A possible morphogenic effect of leaf sheaths on subsequent leaf development was investigated by varying sheath tube (pseudostem) length in plants of perennial ryegrass (Lolium perenne) cv. Talbot by either incising longitudinally or excising the distal portion of the sheath tube, while leaving the basal length of the tube intact. The tube was maintained at predetermined lengths by incising and excising new growth daily. The youngest rapidly expanding leaf was allowed to grow through the tube and was measured when fully expanded. Reducing tube length by excision or by incision from 60 mm to just above the cowl leaf on the apex reduced lamina length by 87% and 77% respectively. Over all tube lengths, laminae in incised treatments were almost twice as long as those in excised treatments. Sheath length followed a similar pattern.

The effect on developing leaves of artificially extending sheath tubes (previously excised to 15 mm) to 30 or 45 mm with foil was similar to that of initially excising sheath tubes to 30 or 45 mm.

The shorter the sheath tube (reduced by incision) through which the leaves had to grow, the shorter the cells, especially in the laminae. The estimated cell number per row along the length of the laminae ranged from 190 in tillers (shoots) with a very short tube (just above the cowl leaf) to 454 in intact control tillers.

It is concluded that the sheath tube has a morphogenic influence on the development of subsequent leaves due to the change in environment of the leaf lamina on appearance, affecting both cell elongation and cell division.
A tobamovirus infecting capsicum in Australia
Authors: PARES R. D.
Published: February 2008

A tobamovirus infection of Capsicum annuum is recorded for the first time in New South Wales, Australia. The causal virus is described and shown to differ from tobacco (TMV) and tomato (ToMV) mosaic viruses in its host reactions and serology.

Seventeen capsicum cultivars were tested for reaction to the Australian isolate and ranked according to symptom severity. Field and glasshouse observations indicated that the virus causes a decrease in height and weight of plants, fruit malformation and leaf mosaic symptoms.

It is proposed that the capsicum tobamovirus strains are sufficiently distinctive from TMV and ToMV to be grouped together and designated a separate virus: capsicum mosaic virus (CaMV).
Purification and properties of two Swedish isolates of barley yellow dwarf virus and their serological relationships with American isolates
Authors: EWEIDA M. , OXELFELT P.
Published: February 2008

Two Swedish isolates of barley yellow dwarf virus (BYDV), one (39/78) transmitted much more efficiently by Rhopalosiphum padi than by Sitobion avenae and the other (27/77) transmitted specifically by Sitobion avenae, were purified with yields of 200–300 μg/100 g infected oat leaves. Three light scattering zones were obtained when isolate 39/78 was sedimented in 10–40% (w/w) sucrose density gradients but only one zone with the other isolate. The sedimentation coefficients of 39/78 particles were 94,106 and 150 S, respectively, whereas the 27/77 particles sedimented at 110 S. Four protein bands of mol. wts 31 900, 29 700, 28 000 and 15 000 were detected when disrupted 150 5 particles of the 39/78 isolate were electrophoresed in SDS‐polyacrylamide gels. Only one major band of mol. wt 24 500 was detected when 94 or 106 S particles were electrophoresed under the same conditions. The 27/77 isolate yielded one major band of mol. wt 23 500. A weak serological relationship was found between isolates 39/78 and 27/77. In enzyme‐linked immunosorbent assay, isolate 39/78 was serologically closely related to New York isolate PAY, whereas 27/77 was closely related to MAY.
The effects of mixing Italian ryegrass (Lolium multiflorum) with perennial ryegrass (L. perenne) or red clover (Trifolium pratense) on the incidence of viruses
Authors: LEWIS G. C. , HEARD A. J. , GUTTERIDGE R. A. , PLUMB R. T. , GIBSON R. W.
Published: February 2008

Mixing the ryegrass mosaic virus (RMV) resistant perennial ryegrass (Lolium perenne) cv. Endura with the susceptible Italian ryegrass (L. multiflorum) cv. RvP decreased infection of RvP wth RMV from 37% when grown alone to 22% when mixed. However, Endura yielded less than RvP and there was no yield benefit from mixing the two cultivars. Mixing red clover (Trifolium pratense) cv. Hungaropoly with RvP had no detectable effect on RMV incidence in RvP but did decrease the incidence of red clover necrotic mosaic virus in Hungaropoly from 9% to 1% and of white clover mosaic virus from 53‐5% to 41%. The yield of the mixture was equal to that of RvP grown alone but given nitrogen fertiliser.

The numbers of eriophyid mites, including Abacarus hystrix the vector of RMV, on ryegrass leaves were similar in pure and mixed swards.

It is concluded that with herbage crops, the common practice of sowing mixtures of species may help control virus diseases.
Control of potato cyst‐nematode, Globodera rostochiensis, and root‐knot nematode, Meloidogyne incognita, by organosphosphorus, carbamate, benzimidazole and other compounds
Authors: WHITEHEAD A. G. , BROMILOW R. H. , FRASER J. E. , NICHOLS A. J. F.
Published: February 2008

Control of potato cyst‐nematode, Globodera rostochiensis, was examined on potato or tomato in pots and on potato in field plots by various chemicals incorporated into the soil at planting. The most effective nematicides were organophosphorus compounds, generally of the type O,O‐diethyl O‐phosphoro‐thioates or O,O‐diethyl phosphorodithioates, carbamates and benzimidazoles. In organic soils, the more lipophilic compounds were less effective, presumably because of sorption onto soil organic matter.

Foliar sprays of chemicals, including oxamyl which is known to be translocated to roots, gave poor control of G. rostochiensis.

The root‐knot nematode, Meloidogyne incognita, on tomato, widely used in screening for nematicidal activity, was controlled by aldicarb or phoxim incorporated into the soil at planting, but not by benomyl or thiabendazole, in contrast to the moderate effectiveness of these latter two chemicals against G. rostochiensis.
Vertical distribution of Pratylenchus neglectus, P. crenatus and Tylenchorynchus dubius associated with maize roots and the effect of aldicarb residues
Authors: BEANE J.
Published: February 2008

Depth samples on a field trial on forage maize revealed consistent differences in the numbers of Pratylenchus neglectus, P. crenatus and Tylenchorynchus dubius at different depths after treatment with aldicarb the previous year. Pratylenchus was more numerous lower down in residual‐treated soils but more evenly distributed in untreated soils. T. dubius, although less numerous after aldicarb, was more numerous in the upper layers of the soil. Aldicarb and benomyl applied the previous year had no residual effects on yields.
Non‐glaucousness, a probable aphid‐resistance character of wheat
Authors: LOWE H. J. B. , MURPHY G. J. P. , PARKER MARY L.
Published: February 2008

Cuticular waxes from wheat cultivars that have a bluish‐green waxy bloom under field conditions were compared with those of non‐glaucous (NG) variants that appeared dark green and glossy in the field. Cuticular wax from NG variants was deficient in diketones and hydroxydiketones, and did not form the micro‐spicules of epicuticular wax which were characteristic of the normal bloom.

Typically, NG wheats were resistant to Sitobion avenae in the field, but in environments where wax secretion was diminished, resistance was reduced or absent. Possible causes of this resistance, which appears likely to be easy to exploit, are discussed.
Field evaluation of resistance to black bean aphid, Aphis fabae, in close relatives of the Faba bean, Vicia faba
Authors: BIRCH N.
Published: February 2008

A field assessment of 26 accessions of Vicia narbonensis and three of V. johannis confirmed previous laboratory studies demonstrating higher levels of resistance to Aphis fabae in these two wild species compared to the closely related crop, Vicia faba. Accessions of V. johannis were significantly more resistant than most accessions of V. narbonensis for all resistance indices measured except survival of aphid nymphs. Plant growth stage significantly affected levels of resistance in both Vicia species, resistance being moderate at pre‐bud stage, decreasing on flowering and rising again at pod fill and onset of leaf senescence. Significant intraspecific variability in aphid resistance was found only within the 26 accessions of V. narbonensis, var. serratifolia being more resistant than var. narbonensis. Possible resistance factors and the agronomic potential of these two wild relatives of Faba bean are considered.
Flowering response of pearl millet to water stress during panicle development*
Authors: MAHALAKSHMI V. , BIDINGER F. R.
Published: February 2008

In pearl millet, severe water deficit during the period of panicle development delays flowering. The flowering response of both main shoot and tillers to water stress during panicle development was investigated using four hybrids. Panicle initiation of all tillers occurred in the three early genotypes despite water stress. In the late genotype, however, panicle initiation of tillers occurred only after the release of stress. The delay in flowering due to water stress was more pronounced in the tillers than in the main shoot. However, the proportion of tillers producing an inflorescence was increased by water stress. Grain yield losses on the main shoot by water stress were compensated by an increase in tiller grain yields. Delay in flowering and buffering by tillers provide an important adaptive mechanism to overcome a period of drought stress prior to flowering.
The effect of frit fly (Oscinella frit) control measures on the establishment of seedling ryegrass (Lolium spp.)
Authors: MOWAT D. J. , JESS S.
Published: February 2008

In four experiments from 1981 to 1983 August‐sown perennial (Lolium perenne) and Italian (L. multiflorum) ryegrass were exposed to frit fly attack by oviposition on the seedlings. Responses to pesticide treatment were detected at autumn harvests. Even at low sowing rates pesticide application did not ultimately establish a better sward and, owing to a tendency towards spring reversal of autumn yield responses, even temporary returns were negligible. As frit fly numbers were unusually low the autumn response to pesticide was sufficient to suggest that frit fly is always likely to be an influential factor in ryegrass sown in early August in this area. Later sowings are less likely to be affected. The yield response was related to the numbers of adult flies present 2–7 wk after sowing. Neither grass species was consistently more affected than the other. Additional seed (compared with a sowing rate below normal commercial rates) and the inclusion of fertiliser at sowing also gave only small temporary returns and failed to establish a better sward. It is suggested that routine protection against frit fly attack is of at least equal value to the other two variables in an early August sowing.
Shoot development and bud mite infestation in hazelnut (Corylus avellana)*
Authors: BURGESS JEAN E. , THOMPSON MAXINE M.
Published: February 2008

The interaction of environmental and genetic variation in hazelnut (Corylus avellana) shoot development and the behaviour, survival, and colonisation of eriophyid bud mites (Phytoptus avellanae and Cecidophyopsis vermiformis) were studied. The distribution of galled buds on shoots indicated that mites colonised only those buds formed during the mite migration period. The point of entry is probably the growing shoot tip. Once within this structure, as the shoot develops the mites have access to a succession of newly‐formed, bud primordia that are unprotected by bud scales. The relative accessibility of the apical meristem and bud primordia may affect host susceptibility.
The use of fungicidal paints and gels to treat existing apple cankers
Authors: McCRACKEN A. R. , COOKE LOUISE R.
Published: February 2008

Four paints containing mercuric oxide, octhilinone, thiophanate‐methyl or triad‐imefon and five gel formulations (carbendazim/triadimefon in sodium alginate or xanthan gum, carbendazim/triadimefon/hypophosphorous acid and thiophanate‐methyl/oxycarboxin in xanthan or PP969/alginate) were tested on natural cankers caused by Nectria galligena on apple trees. Scraping cankers decreased their size 7–9 months later due to stimulation of callus formation, even where no fungicide was applied, and decreased perithecial, but not conidial production. Only the paints were applied to scraped cankers and that containing mercuric oxide was the most effective in decreasing canker size and restricting new canker growth.

All formulations except the octhilinone paint were applied to unscraped cankers. Only mercuric oxide paint and acidic carbendazim/triadimefon/xanthan gel stimulated callus formation and only the former caused a decrease in canker size. Every treatment, except triadimefon paint and PP969/alginate, reduced conidial production. Bioassay with TV. galligena showed that the carbendazim and thiophanate‐methyl gels achieved some movement of fungitoxicant into plant tissue.
Purification and partial characterisation of beet mild yellowing virus and its serological detection in plants and aphids
Authors: GOVIER D. A.
Published: February 2008

Beet mild yellowing virus (BMW) was reversibly precipitated at temperatures below about 5°C and this property was used as a final step in a purification procedure which yielded about 1 mg virus/kg tissue. Purified virus was infective and had an A200/A280 ratio of about 1–8. BMW particles were isometric with a diameter of 26 nm, sedimented at 116 S, had a buoyant density in caesium chloride of 1.42 g/cm3 and a coat protein mol. wt of 25 400.

An antiserum to BMW had a titre in immunodiffusion tests of 1/256 and was used in immunodiffusion tests, immunospecific electron microscopy (ISEM) and enzyme‐linked immunosorbent assay to demonstrate a close serological relationship between BMW and beet western yellows virus. BMW was readily detected by ISEM in plants and also in aphid vectors after treatment of aphid extracts with a chloroform:butanol mixture.
Viruses infecting winter oilseed rape (Brassica napus ssp. oleifera)
Authors: WALSH J. A. , TOMLINSON J. A.
Published: February 2008

Turnip mosaic virus (TuMV) and cauliflower mosaic virus (CaMV) have been found infecting field crops of winter oilseed rape (Brassica napus ssp. oleifera) in South Warwickshire. Other viruses found include broccoli necrotic yellows virus (BNYV) and a member of the beet western yellows virus group.

Systemic leaf symptoms caused by TuMV varied within and between cultivars; the three predominant reaction types were classified as necrotic, mosaic and immune. Some recently introduced cultivars of oilseed rape were more severely affected by TuMV infection than older cultivars. Reactions to CaMV were less varied and immunity was not found. The seed yield from TuMV and CaMV‐infected plants was less than that of healthy control plants. This effect was due to infected plants producing either fewer seeds, smaller seeds or both. Germination of seeds from infected plants was unaffected if sown soon after harvest. After storage for one year the germination of seed from a virus infected plant was significantly less than that of seed from a virus‐free plant.

All commercial cultivars tested were experimentally susceptible to turnip yellow mosaic virus (TYMV) and some American strains of cucumber mosaic virus (CMV).
An infra‐red photographic technique for the rapid assessment of weed and crop seedlings in field experiments
Authors: MAY M. J. , HARVEY R. N. , WRIGHT KATHRYN J.
Published: February 2008

The construction and procedures for use of a camera box are described. Infrared film was used to record weed and/or crop growth stages in the field. The equipment allowed fast assessment of experiments in the field and more detailed assessments in the laboratory. Counts, ground cover, plant growth and healthy plant material were all satisfactorily recorded by the technique.
Uptake, translocation and metabolism of fluazifop‐butyl in Setaria viridis
Authors: CARR JANE E. , DAVIES L. G. , COBB A. H. , PALLETT K. E.
Published: February 2008

The uptake and translocation of fluazifop‐butyl was investigated in Setaria viridis. Young plants (three to four leaves) with a portion of the second, third or fourth leaf covered, were sprayed with a dose equivalent to 0.25 kg a.i. ha‐1. 14C‐fluazifop‐butyl was subsequently applied to the unsprayed area and the treatment resulted in plant death within 2 wk. Uptake by leaf 3 was rapid, with less than 5% of the applied dose remaining on the leaf surface after 24 h. The highest proportion of 14C‐activity was retained in the treated portion of the leaf. Only 2% of the applied dose was translocated from leaf 3 and 0. 76% accumulated in the apical meristem.

Uptake by the younger leaf 4 was more rapid and the pattern of translocation differed in that more 14‐‐activity accumulated in apical meristematic tissue. 6–30% of the applied dose was undetected and this was greatest when foliar uptake was slow. Artificial leaf surface experiments indicated that this undetected activity may have been due to volatility of fluazifop‐butyl or degradation to volatile products. 14C‐activity extracted from treated leaves was identified as fluazifop‐butyl, fluazifop acid and polar conjugates. The major 14C‐activity extracted from the apical meristem was fluazifop acid and no fluazifop‐butyl was detected in this extract.
Yield losses caused by potato cyst nematodes: a review of the current position in Britain and prospects for improvements
Authors: TRUDGILL D. L.
Published: February 2008

Studies of the yield losses caused by potato cyst nematodes (PCN) in Britain are reviewed.

The main conclusions either drawn from or supported by the literature, are:‐ 1) The models/equations used to relate yield losses to pre‐planting densities of PCN are not entirely satisfactory. 2) There is considerable variation between sites in the damage caused by PCN and hence the yield response to nematicide treatment cannot be reliably predicted. 3) Oximecarbamate nematicides, if well applied and if other damaging pests are absent, will prevent most of the loss at infested sites but do not increase yields at most uninfested sites. 4) PCN decreases yields by reducing the effectiveness of the root system, and hence leaf area duration and the amount of light intercepted by the crop canopy: in some circumstances PCN may also decrease the efficiency of assimilation. 5) Several factors interact either to increase or to decrease the damage caused by PCN; some of the more important are soil type, interactions with micro‐organisms, differences in husbandry, differences between cultivars in their tolerance of damage, the weather and differences in yield potential between sites. 6) Both the yield losses caused by Globodera pallida and the amounts of nematicide used may be decreased by planting tolerant and partially resistant cultivars.

New results are used to show that yield losses may be decreased by applying extra fertiliser and that low rates of nematicides may be adequate to prevent damage to tolerant cultivars. Further research may lead to an improved basis for advice relating to the control of PCN and the damage it causes.
Effects of fluorescent pseudomonads on the potato blackleg syndrome
Authors: RHODES D. J. , LOGAN C.
Published: February 2008

In four field trials in 1983 and 1984 potato tubers were inoculated by dipping them at planting in a suspension of Erwinia carotovora subsp. atroseptica and then treated with a powder formulation of two strains of fluorescent pseudomonads (B 10 and I 13) isolated from potatoes. lnoculation with E. carotovora increased blackleg and reduced emergence, plant growth, tuber size and weight compared with uninoculated controls. These effects were partially reversed by treatment of tubers with fluorescent pseudomonads which also reduced contamination by E. carotovora and the soft‐rot potential of progeny tubers. In some trials a mixture of both pseudomonad isolates delayed the breakdown of the mother tuber although individual treatments did not.
The host‐plant relationships of apterous virginoparae of the grass aphid Metopolophiurn festucae cerealium
Authors: DENT D. R. , WRATTEN S. D.
Published: February 2008

Metopolophium festucae cerealium has at various times caused damage to both grass and cereal crops. Despite this, little work has been done on the relative susceptibility of different grass and cereal cultivars to this aphid. The present work showed that for the cultivars examined the most common ley pasture species (Lolium perenne and Lolium multiflorum) exhibited relatively low levels of antibiotic resistance to M. f. cerealium and that wheat is more susceptible than any of the grass species tested. This enigma, in view of the aphid's low pest status on wheat, is discussed. The resistance in the grasses was greater at the stem elongation stages than at the seedling stage but the ranking was consistent between growth stages. M. f. cerealium exhibited a preference for feeding on emerging and senescing leaves of 10‐wk‐old grass but on wheat it distributed itself evenly between all available green leaves.
Heat treatments for the control of sprouting of potatoes during storage
Authors: RAMA M.V. , NARASIMHAM P.
Published: February 2008

Potatoes were given hot water dip and vapour heat treatments at temperatures ranging from 50 to 80°C and 60 to 70°C respectively for various durations to control sprouting.

Hot water treatment at its effective temperatures and durations resulted in undesirable physical damage to tubers. On the other hand, vapour heat treatment at 60°C with 95 ° 5 r.h. for 60 min suppressed sprouting, when given to tubers at the sprout emergence stage, without causing any deleterious side effects. The treatment, when repeated after 3 wk further reduced sprout yield during storage at ambient conditions (22–35°C, 50–80 r.h.).

Comparative studies on the efficacy of vapour heat treatment and manual de‐sprouting showed that vapour heat was superior to manual de‐sprouting.
Effect of a calcium peroxide seed coating on germination of perennial ryegrass seeds
Authors: NAYLOR ROBERT E. L. , PRENTICE C. G.
Published: February 2008

A seed coating containing calcium peroxide improved germination and emergence of perennial ryegrass in wet conditions. This was attributed to the oxygen supplying capability of the coating. In dry soil, coated seeds performed less well than uncoated seeds, possibly because the coating selectively absorbed water and prevented its passage to the caryopsis.
Variation in growth attributes of contrasting populations of Trifolium repens
Authors: EAGLES C. F. , OTHMAN O. B.
Published: February 2008

A range of growth attributes was measured in seedlings of 10 Trifolium repens populations, differing in leaf size and origin, grown in three temperature and two glasshouse environments.

Growth rates of large leaf types of Mediterranean origin were higher than those of smaller leaf types at 10°C. However, the greater temperature response of the smaller leaf types resulted in higher growth rates for S.100 and S.184 than for a large leaf type from Israel at 20°C.

The increase of growth rate with temperature was associated with changes in leaf area ratio and net assimilation rate between 10° and 15°C but only with changes in net assimilation rate between 15° and 20°C. Within each temperature environment, population differences in growth rate were related to differences in net assimilation rate rather than leaf expansion.

At low temperature a greater proportion of dry matter was distributed to leaf tissue in large leaf types particularly those of Mediterranean origin but they showed a proportionately smaller increase in allocation to leaves with increasing temperature compared with small leaf types.

In the glasshouse environments growth rates in spring were more than double those in the autumn. This difference was associated with net assimilation rates which were about five times greater in the spring environment. However, leaf area ratios in the spring were only half those in the autumn. These differences in leaf area ratio between the glasshouse environments were closely related to differences in specific leaf area but not to differences in distribution of dry matter to leaf tissue which was greater in the spring environment.
Effect of temperature, irradiance and photoperiod on morphological characters of seedlings of contrasting white clover populations
Authors: EAGLES C. F. , OTHMAN O. B.
Published: February 2008

Seedlings of 10 contrasting white clover populations differing in leaf size and origin were grown in a glasshouse in spring and autumn, and in controlled environments in which temperature (10°, 15°, 20°C), photoperiod (8, 16‐h) and irradiance (13, 47, 57 Wm‐2) were varied. There were large effects of these environmental variables on a range of morphological characters. Population differences were closely related to classification of the populations by leaf size. Within the large leaf types there was also an effect of origin. In particular, Mediterranean types differed from those of northern origin.

Rate of leaf appearance increased with temperature but was less affected by photoperiod. Population differences were greater at lower temperatures.

Petiole length was more sensitive to temperature than was leaflet length, particularly in the range 10° to 15°C. Similarly, petiole length increased appreciably with photoperiod extension; smaller leaf types responded more than large leaf types with the result that there were no population differences in the 16‐h photoperiod. Population differences in the other environments were closely related to leaf size classification.

The onset of stolon production was delayed by lower temperatures and by short photoperiods but stolon number at the sixth leaf stage of development was not closely related to this character in the temperature environments since stolon numbers increased at lower temperatures.

In low temperature and short day conditions the large leaf types including those of Mediterranean origin showed a desirable combination of long petioles and large leaves compared with the smaller leaf types. However, these differences between the two groups were eliminated for petiole length, and much reduced for leaflet length, by the greater response to temperature and photoperiod of the smaller leaf types. The implications of these responses for seasonal production are discussed.

There were large effects of irradiance on the lengths of leaflets and petioles with longer ones at higher irradiance levels. There were also faster rates of leaf appearance at higher light levels. Stolon production was faster at 57 Wm‐2 than at 47 Wm‐2 while at 13 Wm‐2 no stolons were produced. After an extended period in the lowest light environment there was some plant mortality.
Effects of osmotic priming and ageing on onion seed germination
Authors: DEARMAN JANE , BROCKLEHURST P. A. , DREW R. L. K.
Published: February 2008

Onion seeds were osmotically primed in polyethylene glycol solution (342 g/kg water) either for 14 days before accelerated ageing at 40°C. 18% m.c. for 0, 24, 48, 72 or 96 h, or for 10, 14 or 17 days after ageing. Priming improved the rate of germination compared with non‐primed seed. Priming before ageing delayed the loss of viability due to ageing, but priming after ageing had no effect on viability.

Primed and dried onion seed was stored for 18 months at 10°C, 9% m.c. with no effect on viability; improvements in germination rate due to priming were maintained over the storage period.

Conductivity measurements of seed leachates were not a consistently reliable indicator of germination performance.
Environmental factors affecting seed germination of gray birch (Betula populifolia) collected from abandoned anthracite coal mine spoils in northeast Pennsylvania
Authors: PRATT CARL R.
Published: February 2008

Germination of gray birch (Betula populifolia) seed collected from anthracite mine spoils in northeastern Pennsylvania was studied. Environmental conditions of the spoil banks are such that high mortality may occur at seed and germination stages because of low moisture availability and thermal stress. The mine spoil banks are harsh environments with respect to key seed germination factors: percent soil moisture as low as 1.8% and soil surface temperatures reaching 59°C. In the field, gray birch typically germinated in mid‐April prior to severe environmental stress. Trends in germination success were inversely related to rising soil temperature and decreasing soil moisture availability. Although seeds were capable of survival and germination under laboratory conditions of constant temperatures in excess of 55°C, dramatic decline in germination was observed under fluctuating temperature regimes likely to be experienced in the field. No germinations occurred under fluctuating temperatures in excess of 30°C. Germinations in the field were seen to end after mid‐June when substrate temperatures exceeded 30°C.
Effects of high temperatures on the ripening responses of bananas to acetylene
Authors: SMITH N. J. S. , SEYMOUR G. B. , THOMPSON A. K.
Published: February 2008

Unripe bananas were exposed to 1 ml litre‐1 of acetylene gas in air for different periods of time and different temperatures and then ripened at 20°C. It was found that exposure of fruits to acetylene for 4 h at 20, 25 and 30°C, or 8 h at 20°C did not initiate ripening. Some fruits which had been exposed to acetylene for 4 h at 35°C or 8 h at 25°C and all fruit exposed for 8 h at 30° and 35°C ripened. These results indicate that bananas became more sensitive to ripening by acetylene as temperatures increased within the range of 20 to 35°C.
The effect of sciarid larvae (Lycoriella auripila) on cropping of the cultivated mushroom (Agaricus bisporus)
Authors: WHITE P. F.
Published: February 2008

Significant linear relationships between the mean number of sciarid, Lycoriella auripila, larvae/125 g‐sample of casing and yield, numbers of mushrooms and weight/mushroom were demonstrated at all stages of a mushroom crop. Negative relationships were obtained for yield throughout the cropping period. There was no injury threshold for this pest, although an economic threshold of one larva/sample was deduced. Loss in yield was mostly due to the destruction of mushroom primordia and presumed interruption of nutrient supply to the developing sporophores.

Numbers of mushrooms were severely reduced in the first, second and third flushes, more so than yield, although a large increase in numbers was demonstrated in the fourth flush. The size of mushroom was inversely related to numbers, although the increases in size in the first three flushes were insufficient to compensate for the reduction in numbers. A reduction in size was evident in the fourth flush.
Predator density manipulation and its effects on populations of Rhopalosiphumpadi (Horn.: Aphididae) in spring barley
Authors: CHIVERTON PHILIP A.
Published: February 2008

Experiments were carried out in 1981‐83 to assess the impact of polyphagous predators (e.g. Carabidae, Staphylinidae and Araneae) on populations of cereal aphids in spring barley in Sweden. Barriers were erected around mid‐field and field‐edge plots at different times during the aphids' establishment phase in order to manipulate the predation pressure during the aphid pre‐peak period; predators were emigrating from field boundaries.

Rhopalosiphum padi was the dominant species of cereal aphid in 1981 and 1982, and was abundant in both years. Reduction of the predation pressure resulted in R. padi populations that were two to six times larger compared with those in unenclosed control plots. Aphid populations were much larger when the predation pressure was reduced earlier in June than when this was done later, in both years, since late erection of barriers excludes fewer predators because most had already entered the enclosed areas. In 1983, R. padi and Sitobion avenae were equally common but occurred in low numbers, and the effects of reducing the predation pressure were less obvious.

Bembidion spp. (B. lampros and B. quadrimaculatum) and linyphiid spiders were the most abundant predators during the early establishment phase of aphid populations in each year, and significant inverse correlations were found between peak numbers of R. padi per shoot and numbers of predators from these taxa in 1981 and 1982. Similar relationships were found between total aphids and numbers of Staphylinidae, B. quadrimaculatum and Coccinella septempunctata in 1983.

It was concluded that differences between the manipulated numbers of polyphagous predators caused the observed differences in peak population levels of R.padiin 1981,1982 and to a lesser extent, 1983. Apparent levels of parasitism and fungal disease were low during the pre‐peak period. Aphid specific predators, abundant after the peak, were considered partly responsible for the decline of aphid populations each year.

The results are compared with those from similar experiments elsewhere with S. avenae and Metopolophium dirhodum in winter wheat. Reasons why the effects of polyphagous predators are greater, and occur over a much shorter period of time in Sweden are discussed.
The distribution of immature thrips among flowers of faba beans in commercial crops and experimental plots
Authors: STODDARD F. L.
Published: February 2008

Numbers of eggs and larvae of thrips {Kakothrips pisivorus (Westw.)) infesting pistils of various stocks of faba beans (Viciafaba L.) were recorded in different environments. By the end of flowering in spring beans, 25 times as many flowers were infested with, on average, twice as many thrips, as at the onset of flowering in winter beans. Within each of two seasons, levels of infestation varied up to 30‐fold with location. At a single location, some bean stocks were much more heavily infested (greater proportions of flowers contained thrips and/or greater numbers of thrips per infested pistil) than others. Levels of infestation were not clearly associated with the closed‐flower character (cf). Stocks with lush growth were more heavily infested than those with either generally restricted growth or with terminal inflorescences (ti). Those with white flowers, long pods or cytoplasmic male‐sterility were more infested than those which contrasted for these three characters. The path of the pollen tubes was blocked by eggs of thrips in less than 0–5% of flowers. Infestation had no apparent effect on the fertilisation of flowers.
Studies of the infection of the winged bean by Synchytrium psophocarpi in Papua New Guinea
Authors: DRINKALL M. J. , PRICE T. V.
Published: February 2008

Infection of leaves and stems of Psophocarpus tetragonolobus by Synchytrium psophocarpi only occurred following spray inoculation of motile zoospore suspensions and incubation for a minimum of 12 h in polyethylene bags or a mist chamber. The incubation period was 7 days and generation time 22 days at temperatures of 31 oC max, 24 oC min and r.h. of 90% max, 70% min. Young, 1–2 day‐old leaves were most susceptible; there was no infection on 10 day‐old leaves and susceptibility was not increased by the removal of leaf waxes.

No infection occurred when plants were grown from seed from infected pods, seed inoculated with zoospores or sporangia and seed sown in soil containing infected leaf debris. Resting spores were not found in infected tissues stored for 12 wk or in plant debris. S. psophocarpi did not infect Arachis hypogaea, Glycine max, Phaseolus aureus, P. coccineus, P. vulgaris, Pisum sativum, Psophocarpus scandens, Vicia faba, Vigna sesquipedalis and V. unguiculata. S. minutum did not infect winged bean.

Inoculation confirmed the susceptibility of the winged bean lines UPS 62, UPS 122, UPS 126 and resistance of two Thai winged bean lines 1602/1 and 1611/2.
A comparison of the level of resistance in diploid Triticum monococcum and hexaploid Triticum aestivum wheat seedlings to the aphids Metopolophium dirhodum and Rhopalosiphum padi
Authors: SPILLER N. J. , LLEWELLYN M.
Published: February 2008

Resistance to the aphids Metopolophium dirhodum and Rhopalosiphum padi was assessed by measuring adult weight, development time and fecundity on seedlings of three ‘ancient’ diploid wheat lines (Triticum monococcum) and four ‘modern’ hexaploid wheat cultivars (T. aestivum). Adult weight and fecundity were consistently greater on the hexaploid cvs but development time and the intrinsic rate of increase were less affected. Unvernalised seedlings formed the basis of a screening method, the results of which showed the same pattern as already published studies using older plants.
Inheritance of adult plant resistance to mildew in oats
Authors: JONES I. T.
Published: February 2008

Adult plant resistance of a durable nature in oat cv. Maldwyn was studied in a cross with the very susceptible cv. Selma, using a replicated F3 population grown under field conditions. Segregation was found to be continuous, with no discrete classes, and a preponderance of segregants showing intermediate values between the two parents indicating additive genetic control. The number of effective genetic factors segregating in this cross was estimated to be four when material was at the ‘boot stage’ (G.S. 45) and eight or nine at the stage when flowering was complete (G.S. 69). At this latter stage Maldwyn was estimated to be contributing about seven factors for resistance, and the susceptible Selma one or possibly two.

Further improvement, through accumulation of factors from both parents, could be expected and this has subsequently been achieved.

The possible effects, on the durability of resistance in highly resistant transgressive segregants, from increased selection pressure on the pathogen are discussed.
Comparison of sampling methods for alate aphids and observations on epidemiology of soybean mosaic virus in Nanjing, China
Authors: HALBERT SUSAN E. , ZHANG GUANG‐XUE , PU ZU‐QIN
Published: February 2008

Using standard diversity indices, samples of aphids collected on a vertical net were found to be more diverse than collections from green pan traps in experiments conducted in Nanjing, China in 1981. Some species, notably Myzuspersicae, Aphis citricola, and Eriosoma (Schizoneura) japonicum, were collected in greater relative numbers in the pan traps. Several species, including the Macrosiphoniella spp., were under‐represented in the green pan traps presumably because they were not attracted to the green colour of the traps. Yellow pan traps, used concurrently to monitor landing rates of economic species, caught relatively more Aphis craccivora and M. persicae and relatively fewer Aphis gossypii than green ones.

In the Nanjing area soybean mosaic virus (SMV) usually spreads in spring planted soybeans during the latter half of May, causing damage. The predominant aphid species trapped at that time were M. persicae, Lipaphis erysimi, A. gossypii, A. craccivora and E. japonicum, of which the first four are known vectors. Summer planted soybeans are usually affected during a second period of virus spread occurring in mid‐August when various Aphis spp. are abundant. The predominant vector of SMV at that time was thought to be Aphis glycines which colonises the crop; in 1981, however, A. citricola and A. gossypii, which do not colonise soybean and A. craccivora. which rarely colonises soybean, were much more abundant in mid‐August than A. glycines. A. citricola, A. gossypii and A. craccivora are all able to transmit SMV, and thus should be considered as potentially important vectors. In infectivity assays, only four of 1040 aphids transmitted SMV. These included an A. craccivora, two Toxoptera citricidus and one Aphis sp.
The quantitative assessment of arthropod predation rates by electrophoresis
Authors: FITZGERALD JEAN D. , SOLOMON M. G. , MURRAY R. A.
Published: February 2008

The development of an electrophoretic technique for the quantitative assessment of specific prey material in the gut of a predator is described. Panonychus ulmi and Tetranychus urticae were used as test prey species. Samples prepared from these mites were electrophoresed on polyacrylamide concentration gradient slab gels, which were then treated to reveal esterase activity. The relationship of intensity of a stained band with sample concentration and staining time was not linear for some esterases. Possible causes of this non‐linearity were identified but could not readily be eliminated. However, quantitative assessment of prey material is possible after the preparation of a calibration curve.
Epidemics of Phymatotrichum root rot (Phymatotrichum omnivorum) in cotton: environmental correlates of final incidence and forecasting criteria
Authors: JEGER M. J. , LYDA S. D.
Published: February 2008

Epidemics of Phymatotrichum root rot (PRR), caused by Phymatotrichum omnivorum, in cotton were monitored in field plots at the Blackland Research Center, Temple, Texas during the years 1969–1982. In most years disease incidence, assessed at periodic intervals during the growing season, increased smoothly and levelled off at values in the range 0–04‐0‐99 (proportion of plants killed). During two years there were marked increases in PRR late in the growing season. Increments in PRR were associated with preceding increments in precipitation but only when the latter were large. The final incidence of PRR late in August was directly related (in all but one of the 14 years) to cumulative precipitation in the range 36–100 cm, and inversely related (in all 14 years) to air temperatures greater than 34 oC. Regression was used to relate final PRR incidence to derived weather variates but the equations obtained did not provide a realistic basis for forecasting: the best predictive variates included cumulative precipitation up to mid‐August. A threshold criterion given by P/T > 1·45, where P was cumulative precipitation (cm) from 1 January and T was the mean maximum temperature (°C) during the preceding 10 days, was derived. This criterion satisfactorily grouped years with high (>0·;50) and low (<0–50) incidences of PRR. In those years where a forecast of high incidence was made, the criterion was satisfied prior to the first appearance of PRR (mid‐June); where a forecast of low incidence was made, the criterion was not satisfied until late August. The forecasting criterion was evaluated at three sites in the Blacklands region in 1983, at two in 1984, and at Temple only in 1985. In 1983 and 1984, final PRR incidences of less than 0–50 were forecast and observed; in 1985, cumulative annual precipitation exceeded 50 cm by early June, the threshold criterion was satisfied prior to the first observation of symptoms, and PRR incidence was 0–80 late in August.