摘要:

SummaryEight genotypes of swede (Brassica napusL. ssp.rapifera[Metz.] Sinsk.) at the 8–10 true leaf stage were inoculated with five, 10 or 20 eggs of the turnip root flyDelia floralis(Fall). The roots were sampled, with control roots, after 6 weeks of larval development.D. floralisroot damage, as measured by reduction in root weight, was found to be linked to inoculation level. NeitherD. floralisegg numbers nor swede genotype had a significant effect on the percentage of larvae developing to pupation. Mean pupal weight varied by a factor of ×1.4 and consistently decreased with increasing egg inoculation level. Changes in the root concentrations of glucose, sucrose and fructose were measured. All swede genotypes showed a similar response in their sugar concentrations after root damage. Glucose and fructose concentrations were reduced whilst sucrose concentration remained unaffected. The concentrations of glucose and fructose were highly correlated. Pupal weight, used as a measure of larval development, was significantly correlated with the concentrations of individual and total sugars in the roots. The implications of sugar responses to damage in brassicas, and the correlation between sugar concentrations in the roots andD. floralispupal weights are discuss

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04043.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryR. padigynoparae settling in the canopy of the winter host,Prunus padus, tended to form aggregations. Differences in the degree of exposure to wind, sun, etc., did not satisfactorily explain the aggregated pattern observed. In laboratory experiments, aphids did not distinguish between leaves taken from nearby aggregations and leaves taken far away from aggregations. The results of laboratory olfactometer tests and field trapping studies indicate thatR. padigynoparae produce an aggregation pheromone. Thus the aggregated settling pattern of gynoparae ofR. padican best be explained as a response to an aggregation pheromone.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04044.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe effects of DIMBOA in cultivars of wheat on aphid antibiosis and tolerance to the insecticide deltamethrin were investigated for the aphidSitobion auenae. Over 48 hours the mean relative growth rate differed significantly between nymphs ofS. auenaereared on wheat cultivars containing different levels of DIMBOA. Nymphs on the resistant cv. Altar showed a significantly greater susceptibility to deltamethrin, with nearly a three‐fold increase in the relative toxicity of deltamethrin, compared with the susceptible cv. Dollarbird. The LC50, adjusted for weight, was reduced by 91% for nymphs reared on the high DIMBOA cultivar. The potential for the enhancement of predation under a reduced pesticide régime is discussed in relation to this resear

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04045.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryDifferences were observed in the pathogenicities of two strains ofVerticillium lecanii(strain numbers 1.72 and 19.79) to the whiteflyTrialeurodes uaporariorumand the aphidMacrosiphoniella sanborni. The mean pathogenicity of a mixture of the two strains was intermediate to that of the individual strains, attributable to a competitive interaction during infection. Differences between strains were observed in the production of conidiain vitroand on host insect cadavers. When hosts were infected with the dual‐strain suspension, conidia of strain 19.79 only were recovered fromT. vaporariorumwhereas conidia from both strains were recovered fromM. sanborn

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04046.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryPersistence of conidia of an isolate ofErynia radicans(Syn.Zoophthora radicans) was investigated in relation to the meteorological conditions which occurred during autumn‐winter of 1990–91 in the coastal plain in Israel. Capilljconidia shielded from the sun, placed on the abaxial surface of leaves ofPlumeria acuminata, persisted for 24 h to at least 120 h. Exposed capilliconidia, placed on the adaxial surface of the same leaves, died within 24 h. Almost all the primary conidia shielded from the sun (placed on the abaxial surface of the same leaves) died within a single day. Conidial viability was expressed in subsequent germination on an agar medium.Capilliconidial persistence was closely related to the daily air temperatures, expressed as cumulative day‐degrees. Differences in relative humidity had no substantial effect on capilliconidial mortality. At daytime temperatures of ≤ 20°C, mortality after 24 h incubation was lowest (≤ 34%) and the persistence duration, longest (at least 120 h). Increases in daytime temperature up to 24°C for a few hours increased mortality (37–57% after 24 h incubation) and shortened the persistence duration (72–120 h). Exposure to 24–29°C during daytime greatly increased mortality (65–58% after 24 h) and further shortened the persistence duration (24–48 h). Daytime temperatures of>29°C were lethal to all capilliconidia within 24 h. Temperature had a profound effect on capilliconidial persistence also under controlled environmental conditions. The significance of capiliiconidial persistence is discussed in relation to activity of the fungus in

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04047.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryTreatment of the first leaves of barley seedlings with either 5, 10, 15 or 20 mM salicylic acid, sodium salicylate or acetylsalicylic acid resulted in significant reductions in powdery mildew infection on the upper, second leaves. In general, the greatest reduction in mildew infection on the second leaves was obtained by spraying the first leaves with a 15 mM concentration of the compounds. Although the largest reduction in mildew infection of the upper leaves was obtained when the compounds were applied to the first leaves 1–2 days before inoculation, very substantial reductions in infection were still obtained if the first leaves were treated 12 days before inoculation. The three compounds had little direct effect on mildew infection. When14C‐salicylic acid was fed to first leaves of barley seedlings, uptake was rapid and increased with time. Within 6 h, 0.2% of the salicylic acid appeared in the second leaf and by 24 h after feeding, this had increased to 1.4% (1.1 μmol salicylic acid g‐1fresh wt).The application of various phenolic acids to first leaves also led to reductions in mildew infection on the second leaves. In particular, treatment of the first leaves with 1 mM vanillic acid, isovanillic acid or syringic acid, reduced mildew infection of the second leaves by

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04048.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryTwo formulations of the surfactant sodium dioctyl sulphosuccinate (Aerosol OT, Monawet MO70), one of alkyl phenyl ethylene oxide (Agral) and three fungicides (PP192, dichlorophen and a thiabendazole/iodophor complex ‐Byatran) were tested in field trials for control of clubroot (Plasmodiophora brassicae) on cabbage in 1988 and 1989. A standard mercurous chloride treatment (pre‐sowing compost incorporation) was included in all experiments. Plants were raised in 64 cm3blocks (1988) or 15 cm3free‐fill cells (1989). Mercurous chloride reduced disease severity and increased yield in both years. Byatran was ineffective. The surfactants and dichlorophen, applied as pre‐planting soaks to the plant‐raising compost, restricted disease development and increased yield in 1988 but not in 1989. A similar treatment with PP192 restricted disease severity and enhanced yield in both years. Pouring the surfactants and dichlorophen into the planting hole was more effective than using them to soak the compost. In 1989 pour treatments with Agral and a combined soak/pour treatment with dichlorophen reduced disease severity and increased yields by 250% and 97% respectively; compost treatment with PP192 gave a 150%

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04049.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryA disease of chickpea in India, characterised by chlorosis, severe stunting and phloem browning, was shown to be caused by a geminivirus. This virus was transmitted by the leafhopperOrosius orientalisfrom chickpea to chickpea and several other plant species. A method for purification of this virus was devised and a polyclonal antiserum produced. The majority of the purified particles were geminate. The size of the coat protein was shown to be 32 kD and the nucleic acid was shown to be circular ssDNA of 2900 nucleotides. By immunosorbent electron microscopy this virus was shown to be unrelated to the leafhopper‐transmitted geminiviruses known to infect dicotyledons such as beet curly top, bean summer death and tobacco yellow dwarf viruses. On the basis of particle morphology, leafhopper transmission, host range and serology this virus was considered to be a new, hitherto undescribed, geminivirus and was named chickpea chlorotic dwarf viru

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04050.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryA “resistance breaking” isolate of barley yellow mosaic virus‐2 (BaYMV‐2) was cloned as a cDNA and characterised. Restriction mapping and comparison with a German and a Japanese isolate of BaYMV (BaYMV‐G and BaYMV‐J) revealed a high level of restriction site conservation for RNAl and the majority of RNA2. However, in a box of approximately 600 nucleotides located on RNA2, striking differences in the restriction pattern could be identified. The nucleotide sequence of this box, as well as of the 3‘‐terminal region of RNA1 including the coat protein coding region, and the deduced amino acid sequences were analysed. Identity at the amino acid level was between 99.3% and 92.3% in comparison with the corresponding sequences of BaYMV‐G and BaYMV‐J, suggesting that BaYMV‐2 is closely related to BaYMV. Consequently, the classification of BaYMV‐2 as a “resistance breaking” s

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04051.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe polymerase chain reaction (PCR) method was reliably used for detection of potato leafroll virus (PLRV) RNA in dormant tubers from field‐grown plants and in vitro‐propagated microtubers. A simple RNA extraction from tuber and microtuber tissue allowed reverse transcription and PCR amplification of viral sequences. It was also demonstrated that ELISA could be used reliably for detection of PLRV in crude sap extracts of dormant microtubers producedin vitrobut not in tubers from field‐grown p

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04052.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY