摘要:

SummaryThe effect of black bean aphids on the photosynthesis of sugar beet plants was studied under glasshouse and field conditions. The presence of up to several hundred aphids per leaf had no significant effect on CO2exchange rates over a range of light intensities between complete darkness and light saturation. Artificially prepared honeydew, sprayed onto leaves in the same amounts and composition as was found on severely aphid‐infested plants, covered 30% of the stomata on the upper epidermis but did not significantly alter the rate of photosynthesis of these leaves in the light or the rate of respiration in the dark. The stomata on the lower epidermis were uncovered and functional. High pressure liquid chromatography of aphid‐produced honeydew detected 20 different amino‐acids. Three amino‐acids, aspartic acid, glutamic acid and gluta‐mine, made up the bulk of the amino‐acid weight in the honeydew produced on young plants, up till the 8 leaf‐stage. In the 10 to 12 leaf‐stage, several different amino‐acids occurred in substantial amounts. The amino‐acids to sugars ratio of the honeydew produced by the aphids decreased strongly as the sugar beet plants aged: from 1:6 in plants with 3 or 4 leaves to 1:25 in plants hav

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04026.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryA. fabaepopulations, started at the 3–4 leaf‐stage of sugar beet in the glasshouse and peaking at 3000 individuals per plant, reduced leaf area by 64% at the 14 leaf‐stage. The size of the heavily‐infested leaves number 5 to 10 was reduced by 80% or more. The rate of leaf growth regained normal values after the aphid populations collapsed, but the infested plants did not make up for the decrease in leaf area production that had been incurred during the infestation. Total dry matter production over a period of 15 weeks was reduced by 47%. Honeydew had no effect on leaf size or dry matter production. Sugar beet plants in the field became infested withA. fabaeat the 2–3, 4–5 and 6–8 leaf stages. Maximum populations of 800, 2100 and 2200 aphids per plant were recorded, respectively. The pertinent reductions in leaf area were 91%, 67% and 34% at the 10–12 leaf‐stage and 79%, 65% and 14% at harvest while the total dry matter produced was reduced by 91%, 79% and 16%. Neighbouring plants of the early‐infested sugar beet plants gained significantly higher weights than control plants. Honeydew had no effect on leaf area or dry matter production. The consequences of these results for our understanding ofAphis fabaeinjury in sugar beet and aphid control in the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04027.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryAutumn migrants preferred to settle on the dorsal leaf surface of peach with gynoparae being more numerous than alate males. These return migrants on peach were similar to those described by others except for a comparatively smallerprocessus terminalis. Among the oviparae with metatibial pseudosensoria. most (62.5%) had six antennal subdivisions; 25% possessed five antennal subdivisions and half of these were parasitised. Oviparae were bigger than those previously described on plum/damson but theirprocessus terminaliswas comparatively shorter. Ultimate instar nymphs were without pseudosensoria and had 5–seg‐mented antennae, the VI segment being cleaved from the meriston during the final moult. Alate males mated with the oviparae, mating duration being 3 to 6 min. Oviparae contained, at the most, two well developed eggs at one time, and normally deposited eggs singly during November‐December. Most eggs hatched within 20–28 days but those laid in December during colder weather took up to 50 days to hatch. By midJanuary most eggs had hatched. Fundatrix developmental rate was dependent on sap‐flow. Overwintering occurred as the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04028.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe use of flowers of non‐crop plants by the syrphidEpisyrphus balteatusin margins of cereal fields was assessed quantitatively. G‐tests and the ‘C’ index of Murdoch (1969) were used to compare the use and abundance of twenty‐seven plant species by adult flies from June to August in the UK. The flowers of several plant species were used selectively by hoverflies throughout the season while the relative importance of others changed with date. The prospects for managing the field‐margin flora to enhance biocontrol by hoverflies i

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04029.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryA range of metal ions and the oxoanion WO42‐were toxic to zoospores ofPhytophthora nicotianae parasiticain the order: Ag+>Cu++>WO42‐>Ni+>Co++>Zn+. The LD50for Ag+, 0.11 μM (11.4 ppb), compared with 1.84 μm(117 ppb) for Cu++. Silver was similarly toxic to a range of pathogens includingPythium aphanidermatum, Thielaviopsis basicolaandFusarium oxy‐sporumf.spp. Most zoospores ofPhytophthoraspp. were killed by Ag+in the range 46–460 nM (5–50 ppb), bursting at the higher concentrations. A small sub‐population of most propagules exhibited greater tolerance to silver than the whole. In 0.93 μM (100 ppb) Ag+1.4% ofP. nicotianae parasiticazoospores survived but were all killed at 500 ppb. A population ofP. cryptogea(1.9%) surviving 0.47 μm(50 ppb) were killed at 0.93 μM (100 ppb). Zoospore cysts and germlings showed the same sensitivity to silver. Oospores were mostly killed over the range 0.23–0.93 μm(25–100 ppb) Ag+, some surviving up to the lethal concentration of 9.26 μM (1000 ppb). Mycelium ofP. cryptogeawas generally less sensitive, with some growth occurring at 9.26 μm(100 ppb). Zoosporangiogenesis was unaffected over the range 0.47–4.65 μm(50–500 ppb). Toxicity increased with increased pH over the range 5.0–6.5.Ionic silver was lost from solution during a microscope slide bioassay by binding to the glass surface. In the presence of chloride ions, colloidal AgCl formed which was equally toxic toP. cryptogea. Silver and AgCl were further lost from solution by colloidal agglomeration ‐ Ostwald ripening ‐ and by AgCl adsorption to glass. Silver,<90 nM (10 ppb) Ag+as AgNO3and particles of silver chloride were both strongly attractive to zoospores ofP. cryptogea. Spores burst or failed to germinate on entering lethal concentrations. The results are discussed in the context of the use of silver salts to controlPhytophthoraroot‐rot pathogens and the importance of ion av

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04030.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryPutative biological and chemical treatments for controlling take‐all were used in each of three consecutive years at two locations where winter wheat crops were grown in naturally‐infested fields. The chemical treatments more often decreased take‐all than the biological treatments, but no treatment consistently and significantly decreased take‐all, nor did any cause a significant increase in yield.An isolate ofBacillus cereusvar.mycoidesand one ofB. pumilis, applied as soil drenches in autumn or spring, or in the seed furrows, were usually ineffective. Of the few significant effects on disease, half were associated with increases and half with decreases, and most occurred in April and did not persist to late June. Two strains ofPseudomonas pluorescensapplied to the seed were ineffective.The fungicide benomyl, applied as a drench in autumn and spring at 20 kg/ha was ineffective, while nuarimol, applied as a drench in autumn at 2 kg/ha was sometimes effective. Nuarimol incorporated into the seed bed at 2 kg/ha was the most effective treatment.In analyses using a functional relationship model for data from treated and untreated plots 12% of 176 data sets for biological treatments, 38% of 96 data sets for chemical treatments and 81% of 16 data sets for combined treatments showed increasing efficiency of the treatment with increasing disease intensity. These findings also demonstrate an additional advantage of the experimental design, namely that treatments are tested at different disease intensity levels within

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04031.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryIsometric virus‐like particles (VLPs) with diameter of approximately 34 nm containing ss‐RNA were purified from abnormal mycelium of Shiitake mushroom,Lentinus edodes(Berk.) Sing. SDS‐polyacrylamide gel elec‐trophoresis demonstrated that the virions contain a single capsid polypeptide with molecular weight of about 22 000 daltons. The nucleic acid extract from purified VLPs preparations showed only one band with a size of approximately 7.3 kilobases. The susceptibility to RNase 1 and S1 digestions, resistance to DNase and thermal denaturation behaviour of the viral genome indicated that it is a single‐stranded RNA. To our knowledge, isometric single‐stranded RNA VLPs isolated from Shiitake mushroom mycelia have not been repo

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04032.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe influence of wounding and high‐temperature treatment on the detection of iris severe mosaic virus (ISMV) in secondarily ISMV‐infected iris bulbs was studied. Wounding of the bulbs just after lifting, followed by storage for 3 wk at 17°C or 20°C, increased the detectability of ISMV to 100% reliability. High‐temperature treatment and consecutive storage at 17°C induced a similar improvement of detection. It is concluded that a certain degree of stress, such as wounding or high‐temperature treatment, ultimately leads to an increase in viral antigens and thus to improvement of detection. It is hypothesised that the virus titre increases by the altered metabolism during the repair reactions as a response to stress applied to

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04033.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryMost commercially cultivated orchid plants are generally infected with cymbidium mosaic virus (CyMV) and odontoglossum ringspot virus (ORSV). Two methods were used in order to generate virus‐free plants: meristem culture and thin section culture with chemotherapy. Meristems (0.10 mm to 1.00 mm) were excised from infected axillary shoots of an infected monopodial orchid hybrid (MokaraChar Kuan ‘Pink’) and cultured in modified Vacin and Went medium. Only larger meristem explants survived and the regenerated plantlets remained virus‐infected. In contrast, high percentages of virus‐free plantlets were obtained from thin section cultures of infected plantlets and protocorm‐like bodies with ribavirin treatment. Interestingly, regenerants from thin section cultures without ribavirin treatment were also found to be free from CyMV and ORSV. All plantlets were tested by enzyme‐linked immunosorbent assay (ELISA) and/or polymerase chain r

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04034.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe virobacterial agglutination (VBA) test was developed as a means of detection of cocoa swollen shoot virus (CSSV). Identification of CSSV‐infectedTheobroma cacaoin the field has only been possible by visual examination of symptoms, by virus transmission using mealybugs and by grafting to induce symptom expression in Amelonado cocoa seedlings. Detection of latent infection has not been possible even using enzyme‐linked immunosorbent assays (ELISA). The VBA test successfully detected CSSV in infected sap diluted to 1/2560. Antisera to a range of mild and severe CSSV isolates were tested, and the results suggest a close relationship between seven isolates (1A, Bosomtwi, Bosomuoso, Nkrankwanta, Nsaba, Seidi‐Nkawie and SS365B) while the mild isolate N1 appears to be less closely related. The VBA test was compared with both direct and indirect ELISA in the field. Only VBA detected all the cocoa trees which were known to be infected and additionally identified infection in many symp‐tomles

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04035.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY