bluuebunny/crossref_metadata_2025_split huggingface dataset:
A bioassay for predicting the resistance of wheat leaves to Septoria nodorum
Authors: GRIFFITHS HELEN M. , JONES D. GARETH , AKERS A. 
Published: February 2008

SUMMARYPlants of the winter wheat cv. Bounty were inoculated with Septoria nodorum and then assayed for ergosterol. A detached leaf technique was used in which leaf segments were incubated on agar containing benzimidazole. Four levels of a conidial suspension inoculum were applied using a measured droplet technique. Ergosterol in plant extracts was measured using HPLC and its identity confirmed by co‐injection with pure ergosterol as an internal standard. The extracts were also assayed by silica‐gel thin layer chromatography with the sterol being visualised with rhodamine; the presence of ergosterol in the material from the two higher disease level treatments was confirmed by analysing the eluted spots in a spectrophotometer. Additional confirmation of ergosterol was obtained using gas‐liquid chromatography comparing a mixture of known plant sterols with a sample from the diseased leaf tissue.The ergosterol assay was found to be very sensitive and offers a high level of reproducibility. It would therefore appear that such assays could be of value in breeding programmes when it is necessary to screen wheat cultivars for their reaction to S. nodorum or other fungal pathogens.
Traits associated with virulence to the aphid Macrosiphoniella sanborni in eighteen isolates of Verticillium lecanii
Authors: JACKSON C. W. , HEALE J. B. , HALL R. A. 
Published: February 2008

SUMMARYEighteen isolates of the entomopathogenic fungus Verticillium lecanii from various world‐wide locations, from insect hosts and soil were bioassayed against the aphid Macrosiphoniella sanborni in the laboratory. Virulence ranged from an isolate which achieved 100% mortality and LT 50 value (adults) of 3 days ± 0· 2 at 24 ° C, compared with the least virulent isolates causing less than 10% mortality over 14 days (when treated with an inoculum of 1 × 106 conidiospores/ml). All isolates produced extracellular protease and lipase, irrespective of their virulence. A number of traits were frequently associated with the expression of virulence including fast germination, high sporulation rate, an absence of extracellular amylase activity and high extracellular chitinase activities. Large spore size was not strongly associated with virulence. There were exceptions in each variate studied, suggesting that overall expression of virulence is a result of the total complex of these and other traits still to be determined.
Cereal production, crop protection and plant breeding*
Authors: WILLIAMS WATKIN 
Published: February 2008

SUMMARYTrends in British agriculture which have led to the eclipse of rotations, to the concentration of cereal production on wheat and barley, and to a changeover to winter cereals, have increased the vulnerability of cereal crops to disease. Epidemics have been prevented by the deployment of effective resistances and, more recently, of a wide range of crop protection chemicals. Ecological protection by means of variety mixtures and field diversification has now added a new and effective element for the defence of cereals. The problem of durability of resistances and of the continuing effectiveness of chemicals remains, and new problems of susceptibility of crop varieties to herbicides have arisen. It is possible through the combined use of genetical, chemical and ecological defence mechanisms, to maximise the period of effectiveness of resistance genes and of fungicides and insecticides. The experience of the past half‐century has shown that dependence on a single protective mechanism provides only a transient solution to controlling disease.
A quantitative analysis of varietal and moisture status effects on the growth of Vicia faba in relation to radiation absorption
Authors: GREEN C. F. , HEBBLETHWAITE P. D. , ISON DEBORAH A. 
Published: February 2008

SUMMARYGrowth of two cultivars of Vicia faba, under various conditions of moisture status, was analysed in terms of solar radiation absorbed by their foliage.The relationship between dry‐matter production and absorbed photosynthetically active radiation was linear throughout the growing season for both cultivars (Minica and Alfred) and for all levels of soil moisture status. A straight line was used, the slope of which represented a constant mean seasonal ‘efficiency’ of conversion of radiation into biomass.Moisture stress reduced both the amount of radiation intercepted, by limiting the size of the canopy, and the efficiency of its conversion into dry matter. Efficiency of both cultivars grown under optimal water regimes was similar, however, drought had a more drastic effect on conversion efficiency of Minica.Mean crop growth rates were highly dependent upon both absorption and efficiency, as were maximum crop growth rates during the linear portion of growth.Reductions in seed yield were similar to trends in total biomass production. Harvest index was reduced by moisture stress in Minica, and increased to compensate for dry‐matter loss in Alfred.
An analysis of leaf growth in sugar beet.
Authors: MILFORD G. F. J. , POCOCK T. O. , RILEY JANET 
Published: February 2008

SUMMARYThe responses of leaf appearance and expansion to temperature in sugar beet were measured under controlled conditions, using ruler and auxanometers, to establish a basis for a subsequent analysis of leaf growth in field crops. The studies showed that leaf appearance rate responded linearly to temperature above 1°C, that leaf expansion rate responded likewise above 3°C and that both rates were zero below these base temperatures. Auxanometer measurements of leaf extension showed that daily rates of expansion of leaf area increased linearly with the daily integral of temperature. However, hourly rates of extension in length alternated with those in width during each 24 h cycle in patterns that were not clearly related to hourly changes of temperature or to the day/night sequence.
Factors affecting the cold hardiness of the peach‐potato aphid Myzus persicae
Authors: O'DOHERTY ROSE , BALE J. S. 
Published: February 2008

SUMMARYSupercooling point studies were used to investigate the factors influencing the cold hardiness of the peach‐potato aphid Myzus persicae, a freezing‐susceptible insect. Overwintering adults lost cold hardiness as winter progressed, with a variable proportion showing a marked reduction in supercooling ability. Cold hardiness increased in spring so that all individuals demonstrated extensive supercooling ability typical of aphids reared in the laboratory at 20°C with a long photoperiod; these levels of cold hardiness were maintained in the field during summer and early autumn. First instar nymphs demonstrated considerable cold hardiness all year.Surface moisture caused inoculative freezing in some first instar nymphs and adults when supercooled, but the majority were unaffected.In the laboratory, adults starved for 7 days at 5°C showed distinct losses of supercooling potential equivalent to those observed in the field during mid to late winter. No loss of cold hardiness was found in first instar nymphs starved under the same conditions.The results demonstrate that the cold hardiness characteristics of M. persicae are atypical of those observed in other freezing‐susceptible insects and it is suggested that continued feeding during mild winter conditions allows maintenance of cold hardiness particularly in adult aphids, and provides a possible explanation for the successful anholocyclic overwintering of M. persicae during such winters.
Effects of pirimicarb, dimethoate and benomyl on natural enemies of cereal aphids in winter wheat
Authors: POWELL W. , DEAN G. J. , BARDNER R. 
Published: February 2008

SUMMARYThe insecticides, pirimicarb and dimethoate are commonly applied to cereal crops in the UK and when this study was begun the fungicide benomyl was also regularly used. The effects of these chemicals on natural enemies of cereal aphids were examined in replicated plots of winter wheat.Benomyl did not affect any of the groups examined but it was applied early in the season (April/May) when most natural enemies were few or absent from the crop. Numbers of carabid beetles, staphylinid beetles and spiders, sampled using pitfall traps and a vacuum net sampler, were all reduced by dimethoate but not by pirimicarb, although these effects were only detected by pitfall traps when the small plots were surrounded by polyethylene barriers to prevent inter‐plot movements. Parasitic Hymenoptera were decreased by both insecticides, partly due to direct toxicity and partly to host removal. Data on the aphid predators, Coccinellidae, Syrphidae and Chrysopidae were inconclusive because there were very few in the crop due to the scarcity of aphids.Ways in which pesticides can affect natural enemy populations other than by direct mortality and the dangers associated with routine, prophylactic pesticide applications are discussed.
Predicting pathogen‐induced mortality in Hakea sericea (Proteaceae), an aggressive alien plant invader in South Africa
Authors: RICHARDSON D. M. , MANDERS P. T. 
Published: February 2008

SUMMARYThe woody shrub Hakea sericea is an aggressive invader of natural vegetation in South Africa. Large‐scale die‐back in H. sericea is attributed to a form of the fungus Colletotrichum gloeosporioides. The progression of symptoms of the disease was monitored over 21 months. Results were used to construct a transition matrix model to predict further progression of the disease. Eighty‐two percent mortality is predicted after 10 years. Pathogen‐induced seed release occurred mainly between October and January. No regeneration was observed beneath or near infected stands of H. sericea. The model will be useful to managers when identifying priority areas for weed control operations.
Factors affecting the survival of sclerotia of Sclerotium cepivorum in the Fraser Valley of British Columbia
Authors: LEGGETT M. E. , RAHE J. E. 
Published: February 2008

SUMMARYSclerotia of Sclerotium cepivorum buried in muck soil in the Fraser Valley decayed with time. The rate of decay of sclerotia was influenced by local environmental conditions. A mixture of soil with sclerotia increased their survival but there was no difference in the rates of decay in three different soils. The decay was greatest during winter when Fraser Valley fields are often flooded. Sclerotial decay was also affected by pretreatment of the sclerotia. Dried sclerotia decayed significantly (P < 0.05) faster than sclerotia which had not been dried, a phenomenon which is apparently due to changes in micro‐organisms on the sclerotia. Dried sclerotia which had been incubated in moist soil had fewer bacteria and more fungi than sclerotia which had been incubated in soil without being dried. The increase in fungi on the dried sclerotia was due to a dramatic increase in Trichoderma spp.
Persistence and phytotoxicity of napropamide residues in soil
Authors: WALKER A. , BROWN PAULINE A. , MATHEWS P. R. 
Published: February 2008

SUMMARYThe time for 50% loss of napropamide following incorporation into a sandy loam soil in the field varied from about 130 days when applied in spring or early summer to over 200 days when applied later in the year. When left on the soil surface, up to 75% of the applied dose was lost during the first 28 days after application in June or July, whereas losses following application in November, December or January represented less than 25% of the amounts applied. These losses following surface application were closely correlated with the amounts of incoming solar radiation. First‐order half‐lives for degradation in nine soils incubated moist at 20°C in the laboratory varied from 72 to 150 days. They were positively correlated with the extent of herbicide adsorption by the soils and with their clay content, and negatively correlated with soil pH. Phytotoxicity to wheat and barley in the same soils in glasshouse experiments was inversely related to their organic matter content and to the extent of herbicide adsorption. Wheat was more tolerant of the herbicide than was barley. The results are discussed in terms of possible carryover problems with napropamide in some crop rotations.
Loss of genetic diversity in pea germplasm by the elimination of individuals infected by pea seedborne mosaic virus
Authors: ALCONERO R. , WEEDEN N. F. , GONSALVES D. , FOX D. T. 
Published: February 2008

SUMMARYSignificant reduction of genetic diversity was observed in seed coat colour and electrosphoretic isozyme genotypes when infected plants were eliminated in genetically heterogeneous pea populations. Some accessions where genetic homogeneity was expected were apparently mixtures. Detection of latent infections by pea seedborne mosaic virus by the ELISA method was more effective on single‐plant samples than on bulked samples of four to five plants, and from older plants rather than young seedlings. The implication of these findings in relation to a virus eradication programme in plant germplasm collections are discussed.
Some species of Atherigona (Diptera: Muscidae) reared from Gramineae in Senegal
Authors: GAHUKAR R. T. 
Published: February 2008

SUMMARYThe sorghum shoot fly, Atherigona soccata is a pest of economic importance, on late‐sown local sorghums in Senegal. Rearing of shoot flies on five sorghum cultivars (Congossane, 51–69, Naga white, CE 90 and Swarna) showed no antibiosis effect on pest biology. Seven species of the sub‐genus Atherigona were reared from sorghum, five from pearl millet and one species from grasses in the laboratory. Atherigona soccata preferred sorghum and developed satisfactorily on Brachiaria grasses during the off seasons. The sub‐genus Acritochaeta was presented by A. orientalis.
Plant pathogenicity and transmission tests with Acholeplasma spp. isolated from coconut palms in Jamaica
Authors: EDEN‐GREEN S. J. , MARKHAM P. G. , TOWNSEND R. , ARCHER D. B. , CLARK M. F. , TULLYH J. G. 
Published: February 2008

SUMMARYIsolates of Acholeplasma spp. cultured from lethal yellowing‐diseased coconut palms were characterised by polyacrylamide gel electrophoresis (PAGE) of cell proteins and by serological tests. Analysis of PAGE profiles placed 23 of the isolates in either of two related subgroups, (1A) or (IB), which show similarities to A. axanthum; 11 isolates were placed in group (2) which show similarities to A. oculi; and a single isolate formed a unique category (3). Serological relationships determined by fluorescent antibody and growth inhibition tests were in broad agreement with the PAGE classification. There was no evidence of transmission to plant hosts following injection of representative isolates into the cicadellids, Chlorotettix spp., Dalbulus maidis, Euscelidius variegatus or the cixid, Myndus crudus. Some isolates consistenty multiplied in E. variegatus following injection but were not acquired or transmitted during feeding through membranes. Antiserum to A. axanthum did not react with diseased or healthy palm tissues in enzyme‐linked immunosorbent assay and the recovery of further acholeplasma isolates from palms affected by bud‐rot disease demonstrated that these organisms were not specifically associated with lethal yellowing. The results suggested that these acholeplasmas are epiphytes or saprophytes on coconut palms.
The role of flying aphid vectors in the transmission of cucumber mosaic virus and potato virus Y to peppers in Israel
Authors: RACCAH B. , GAL‐ON A. , EASTOP V. F. 
Published: February 2008

SUMMARYMore than 44 species of aphids were trapped by suction during the spring seasons of 1981, 1982 and 1983 over a pepper field at Bet Dagan, Israel. Nineteen species transmitted cucumber mosaic virus (CMV), while seven transmitted potato virus Y (PVY) at least once. Over 80% of the CMV and of the PVY infection among test plants (Capsicum annuum cv. Weindale) exposed to trapped aphids was caused by Aphis citricola and two or three other Aphis species, Myzus persicae and Macrosiphum euphorbiae.Landing rate was determined by comparing the proportion of each species found on green tiles or pepper plants with that found in suction traps. A. citricola was the most common but was found in a much lower proportion on plants than either in flight or on green tiles. Aphis spp. and M. persicae were more than 2–5 times more frequent (relative to other species) on green tiles than in flight. M. persicae and M. euphorbiae, which colonise peppers, were found on peppers at a proportion several times higher than either on green tiles or in the air.The relative importance of the different vector species was calculated by multiplying abundance by the proportion of transmitters and the landing rate. A. citricola and Aphis spp. were responsible for more than 50% of the total transmission of either CMV in 1981 and 1982 and of PVY in 1981. Peaks of CMV infection of bait plants coincided with peaks of transmitters of A. citricola and Aphis spp. caught in suction traps. The significance of these findings in primary infection of peppers with CMV and PVY is discussed.
Inapparent infection of honey bee pupae by Kashmir and sacbrood bee viruses in Australia
Authors: DALL D. J. 
Published: February 2008

SUMMARYInapparent infection of pupae of Apis mellifera by Kashmir bee virus (KBV) and sacbrood virus (SBV) was detected by two different methods, in three consecutive summers, from two widely separated locations in Australia. The prevalence of inapparent KBV infections varied from year to year, in contrast to the more consistent levels of inapparent SBV infection. The implications of inapparent infection for the epizootiology of the viruses in Australia are discussed.
Weed‐crop competition studies in swedes.
Authors: FORBES J. C. 
Published: February 2008

SUMMARYHand‐weeding experiments were conducted over a three‐year period in field‐grown crops of swedes in north‐east Scotland. When weeds were left to grow all season they reduced the dry matter yield of swede roots by 62% in 1980 and 79% in 1981 but by only 42% in the dry year 1982, in comparison with a weed‐free crop.In all three years there was at least one time when a single removal of all weeds was sufficient to prevent yield loss by weed competition. In 1980 this was 6 wk after crop sowing, but the intervals between weed removal times were too great to reveal how critical this timing was. With shorter intervals in 1981 the timing of a single removal of weeds to achieve maximum crop yield was found to be highly critical at 6 wk after sowing, but in 1982 when weed biomass was much lower a single weeding any time from 4–7 wk after sowing gave as high a yield as a crop kept weed‐free all season.Earlier weeding allowed subsequently emerging weeds to become competitive and reduce crop yield, while delaying weeding until after the optimum time allowed early competition from weeds emerging with the crop to depress final yield. In all years if weed removal was delayed until 12 wk after sowing, the crop yield was only slightly or no higher than if weeds were left to grow all season. It is concluded that swedes, unlike red beet or sugar beet, are incapable of recovery from the severe restriction to growth caused by weeds competing with the crop from 6–12 wk after sowing.
Weed‐crop competition studies in swedes.
Authors: FORBES J. C. 
Published: February 2008

SUMMARYIn each of three hand‐weeding experiments in 1980, 1981 and 1982 the biomass of field‐grown crops of swedes was unaffected by weed competition up to 6 wk after sowing but by 9 wk unweeded plots had much reduced crop biomass compared with weed‐free plots. Propachlor, applied to half the plots in 1980 only, had little effect on the severity of weed competition but caused an early check to swede growth from which the crop fully recovered by 12 wk after sowing. In 1981 there was no significant biomass reduction due to weed competition until 9 wk after sowing, yet if weeds were removed 7 or 8 wk after sowing the crop biomass at harvest was substantially lower than if weeds were removed 6 wk after sowing. In 1980 and 1981 swedes made no late compensation for early growth restriction due to weed competition, but in 1982, when weed competition was less severe, late‐weeded or unweeded swedes made partial recovery at the very end of the season.Growth analysis of the 1981 and 1982 crops showed that weed competition reduced leaf area index (LAI) more markedly than net assimilation rate (NAR), though in 1982 weed removal 9 or 12 wk after sowing was immediately followed by a short‐lived increase in NAR. The failure of swedes to recover from weed competition was shown to result from an inability to generate new leaf area rapidly when the weeds were removed. It is suggested that competition between swedes and weeds may be primarily for soil nutrients, especially nitrogen.
Weed‐crop competition studies in swedes.
Authors: FORBES J. C. 
Published: February 2008

SUMMARYThe developmental morphology and anatomy of swede cv. Ruta Øtofte from seedling emergence to vegetative maturity is described, with particular emphasis on development of leaves at the shoot apex and of storage tissue in the hypocotyl and root. Most of the growth of the storage organ takes place by proliferation of parenchyma from secondary cambia scattered throughout the inner secondary xylem.The effects of weed competition on these processes were studied by means of hand‐weeding experiments in field‐grown swede crops in 1981 and 1982. Weed competition greatly reduced leaf area per plant from about 9 wk after sowing onwards, through restriction of both number and size of leaves. Only leaves which had not fully emerged by the onset of weed competition 6 wk after sowing were reduced in area. Weed removal at 9 wk allowed some recovery of leaf number but not of leaf size; weed removal at 12 wk was similar in effect to leaving the crop unweeded all season. Effects of weed competition on storage organ growth were later to appear than effects on leaf area. Weed competition reduced both the number of cambia initiated and the proliferation of parenchyma from these cambia; again if weed removal was delayed until 12 wk the effect was similar to leaving the crop unweeded but some recovery took place if weeds were removed at 9 wk.Artificial shading had similar effects on swede growth to weed competition, except that leaf number was more strongly affected than leaf size and no recovery in cambial initiation took place if shading was removed at 9 wk. Growth analysis showed that shading affected net assimilation rate to a greater extent than leaf area, at least in the early stages, whereas weed competition had previously been found primarily to affect leaf area.The failure of swedes to make any recovery from weed competition if this was removed at 12 wk was primarily due not to depletion by weeds of soil nutrient resources nor to restricted sink capacity in the storage organ, but to limitation of source capacity. Swedes, unlike sugar beet, apparently cannot rapidly generate new leaves in mid‐season to take advantage of weed removal, though there is a large reserve of leaf primordia at the shoot apex. This difference between swedes and sugar beet is discussed in terms of relative sink strength of shoot apex and storage organ.