摘要:

SUMMARYInsect feeding on sorghum was studied in the field and in the laboratory. Quantitative differences in cyanogenesis and phenolic acid content were also measured on the same or simillar plants. High concentrations of cyanide were correlated with a reduction in feeding by grasshoppers and by first‐instar larvae of Chilo partellus; high concentrations of phenolic acids were correlated with reduced feeding by various grasshoppers and by the planthopper Peregrinus maidis. Mythimna separata larvae, and adults and nymphs of Rhopalosiphum maidis, were apparently unaffected by these chemicals. Some sorghum cvs which were relatively unpalatable to grasshoppers and to P. maidis had low levels of the test chemicals, so that here some other factor or factors must be involve

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04733.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe pathogenicity of the only documented ‘aphid’ strain of Metarrhizium anisopliae for the aphid, Macrosiphoniella sanborni, was established by experimental infection. Its aphicidal potential was assessed by conducting parallel experiments with Verticillium lecanii, a fungus of proven efficacy in controlling aphids. The spore germination, growth and sporulation rates of M. anisopliae were slower than V. lecanii and were most likely the principal factors determining the higher LC., values in bioassay and slower propagation of this fungus amongst aphid populations. It is concluded that M. anisopliae, except perhaps in the salt marsh habitat from which it was originally isolated, would not prove as useful an agent as V. lecanii in biological control of aph

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04734.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe numbers of spores of Rhynchosporium secalis washed from samples of barley plants taken weekly, varied markedly. No consistent association with amount of previous rainfall or length of the preceding dry period was detected. On potted seedlings exposed within a crop most infection occurred during long rain periods or when rain fell late in the evening; fewest lesions usually developed on seedlings prevented from touching adjacent plants.Rotorod traps fitted with a 13 mm diameter disc at the apex of each arm were operated under 24 cm diameter covers. Spores were collected on circular cover slips fixed to each disc with glycerine jelly. At all stages of crop growth more spores were trapped at ground level than at other heights tested up to 1 m. The number of spores trapped was not related to the quantity of or duration of rainfall but was related to the mean rate of fall during brief showers only. Efficiency of droplet retention was assessed in a wind tunnel. It declined rapidly when more than c. 5 pl was presented to the disc surface and was less at a wind speed of 1.0 than 0.5 m s‐l. Spore distribution on discs indicated that spores were washed from the surface during long rain period

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04735.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThis paper describes a study designed to find a reliable sampling procedure for estimating the population of Verticillium duhliue in field plots that would not be too demanding in terms of the time required to assay soil samples. In the soil under study, the amount of time needed to obtain reliable estimates of the inoculum density was reduced by taking the larger plot sizes in the range considered, generally taking more plots with fewer samples per plot, and mixing the samples within a plot before redividing for assaying.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04736.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYStrains of Rhizobium spp. (cowpea miscellany) and R. japonicum are characterised by their symbiotic performance on two hosts, Vigna unguiculata cv. Ife Brown and Glycine rnax cv. Bossier. The results indicate that isolates from G. max cv. Malayan, a promiscuously nodulating cultivar adapted to Nigerian conditions, form a group intermediate between R. japonicum and R. spp. but are more closely related to the latter. We tentatively suggest on the evidence of symbiotic performance that R. japonicum is a specialised group within R. spp.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04737.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYPepino (Solanum muricatum) cuttings imported from Chile contained a latent virus which was transmitted by inoculation of sap to Chenopodium quinoa but not to 21 other species. The virus was transmitted by the aphid, Myzus persicae. In C. quinoa sap, the virus lost infectivity when diluted between 10‐3and 10‐4, heated for 10 min between 65 and 70 °C, or stored at room temperature for 4 to 6 days.The virus particles were straight or slightly flexuous filaments 660 to 680 nm long. Up to 15 mg virus per 100 g C. quinoa leaves was obtained by clarification with a mixture of chloroform and carbon tetrachloride. Purified preparations had Amax/Amin= 1.11, A260/A280= 1–30, A0.2601%= 2.8, and contained a single sedimenting component with a sedimentation coeficient of 149s and a buoyant density in CsCl of 1–318. The virus particles contained 5.5% of single‐stranded RNA of mol. wt 2.4×106(estimated by gel electrophoresis of undenatured RNA) and sedimentation coefficient 38.5S, and a single polypeptide of mol. wt 33 000.The virus is distantly serologically related to potato S and carnation latent viruses and is considered a new member of the carlavirus group. The name pepino latent virus is proposed. The cryptogram for this virus is R/1: 2.4/5–5:

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04738.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYIn three short‐term field trials, 24 cocoa progenies were assessed for sensitivity to infection with a severe Ghanaian strain of cocoa swollen‐shoot virus. Some of the progenies were derived from tolerant parents, others had themselves shown mild symptoms as young seedlings. Stem diameters, diameter increments, canopy scores and latent periods (time between inoculation and expression of symptoms) of plants infected when 12 to 22 months old were compared with similar measurements of healthy plants.During the period between 6 and 18 months after inoculation, infection reduced the stem diameter increment of the least sensitive progeny in each trial by 52, 25 and 7%, the last value increasing to 38% during the period between 24 and 30 months after inoculation. Within trials, the effects of virus infection on stem diameter increments and canopy scores were well correlated but latent periods were not significantly correlated with any other variate.In one trial, pod yield was more closely related to canopy condition at the time of cropping than to stem diameter increment 2 yr earlier. Weak correlations between pre‐ and post‐bearing increases in diameters in these trials indicated that tolerance was not directly related to vigour. None of the progenies is considered suitable for direct use as tolerant varieties i

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04739.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYUsing antiserum globulins that reacted only weakly with plant materials, potato leafroll virus (PLRV) at 10 ng/ml was detected consistently by enzyme‐linked immunosorbent assay (ELISA). The reaction with PLRV particles was slightly impaired in potato leaf extracts that were diluted less than 10‐1but not at greater dilutions. Antiserum globulins that reacted more strongly with plant materials could be used satisfactorily for coating microtitre plates but were unsuitable for conjugating with enzyme.The detection end‐point of PLRV, in leaf sap of potato cv. Cara plants grown from infected tubers in the glasshouse, was about 10‐2and the virus was reliably detected in extracts of composite samples of one infected and 15 virus‐free leaves. PLRV concentration was much less in extracts of roots or stolons than in leaf extracts. The virus was detected in infected leaves of all 27 cultivars tested.PLRV was readily detectable 2 wk before symptoms of secondary infection developed in field‐grown plants of cv. Cara and Maris Piper and remained so for at least 5 wk. Its concentration was slightly greater in old than in young leaves and was similar to that in glasshouse‐grown plants. In field‐grown plants of cv. Maris Piper with primary infection, PLRV was detected in tip leaves 21–42 days after lower leaves were inoculated by aphids; in some shoots it later reached a concentration, in tip leaves, similar to that in leaves with secondary infection. Symptoms of primary infection developed in the young leaves of some infected shoots but were inconspicuous and were not observed until at least a week after PLRV was

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04740.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe effect of various desiccation regimes on the ability of second stage larvae of Anguina tritici (Steinbuch, 1799) to survive drying at 0% relative humidity has been studied. It was found that both repeated dehydrationhehydration cycles and the length of the desiccation period itself decreased viability of the larvae. The results are discussed in relation to the mechanisms which may facilitate anhydrobiosis.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04741.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYIn a field trial on light loamy sand, aldicarb was more effective than formalin or dazomet in controlling cereal cyst‐nematode on spring wheat.In the second year of the trial severe ‘scorch’ symptoms appeared and yield losses were greatest in aldicarb treated plots that received most nitrogen even though invasion of plants by juveniles of Heterodera avenae was greatly reduced. Before a dry spell in early summer, crop growth was best in those plots which had received most nitrogen but which finally yielded least; crop growth‐stage and the timing of dry periods are critical in the development of ‘scorch’ symptoms (early shrivelling, browning, and failure of ear emergence) on a light soil given a high rate of nitrogen. ‘Scorch’ occurred at the very luwest H. avenae population levels; the effects of fungal pathogens and NO3nitrogen content of the crop remain uncertain. The rôle of copper in the ‘scorch’ condition could not be assessed since it was applied in a wetter year, in which ‘sc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04742.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY