Changes in soil microflora associated with control of Sclerotium Rolfsii by Furfuraldehyde

The efficacy of 2‐furfuraldehyde for control of Sclerotium rolfsii was studied in laboratory and greenhouse experiments. Mycelial growth of the fungus was reduced proportionally with concentrations of 0.1–0.5 ml furfuraldehyde l^‐1 agar medium, and viability of sclerotia diminished on exposure to 2‐furfuraldehyde vapours. Detectable populations of bacteria and fungi, including Trichoderma spp., were reduced significantly (9=0.05) when furfuraldehyde was added to the agar used for soil dilution plates of untreated soil. Repeated treatments of natural soil with the fumigant significantly increased populations of Trichoderma spp. and bacteria, but diminished numbers of actinomycetes. Increasing dosages applied to soil artificially infested with S. rolfsii caused a reduction of disease on lentil, Lens culinaris. Results indicate that the compound, when applied to field soil, changes the composition of soil microflora and has potential for integrated control of S. rolfsii.     

A Comparison of the Efficacy of Nuclear Polyhedrosis and Granulosis Viruses in Spray and Bait Formulations for the Control of Agrotis segetum (Lepidoptera: Noctuidae) in Maize

Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x 6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X 10¹² polyhedra/ha, and the GV at 4 X 10¹³ granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sampled 24 h after treatment. In larvae sampled 4 days after treatment, the results were 78% and 100% NPV infection, and 13% and 6% GV infection. A total of only six larvae were retrieved on day 11. In both treatments larvae infected with AsNPV died significantly more rapidly and at an earlier instar than those infected with AsGV, indicating that AsNPV appears to have better potential as a control agent for A. segetum.     

pH control of limonin debittering with entrapped Rhodococcus fascians cells

Summary Rhodococcus fascians cells were immobilized by entrapment in -carrageenan. The ability of the system to continuously degrade limonin was tested against pH. A burst of activity was observed when changing from pH 4.5 to 5.0, and a small increase could be seen above the latter value. Such behaviour was not only a response of the metabolic activity of the cells to changes in the medium pH, but to selectivity towards the chemical form of the limonin substrate, which also depends on pH. Additionally, the immobilized cells showed increased resistance against pH changes, since the system recovered almost full activity when the pH was restored to 7.0 after being operated for long periods at pH 4.0. The decrease in limonin-degrading capability of the immobilized cells at low pH values could be overcome by choosing an appropriate dilution rate.Offprint requests to: J. L. Iborra     

Cowpea aphid performance and behaviour on two resistant cowpea lines

In a series of laboratory and climate chamber tests we compared the growth and behaviour of Aphis craccivora on one susceptible (ICV-1) and two aphid-resistant (ICV-11 and ICV-12) cowpea lines. The aphids' growth rates were much lower on the resistant cowpea lines than on the susceptible one, indicating strong antibiosis. In addition, the aphids invariably settled in higher numbers on the susceptible line than on either of the resistant. Compared to ICV-1, damaged leaves of the resistant line ICV-12 were settled upon to a higher degree than undamaged leaves, and leaf discs from the same line were even less resistant.On resistant lines individual aphids waited a significantly longer time before making their first test probe. Total probing time as well as the time preceding a decision to stay or leave was also longer.These results are discussed in relation to the possible mechanisms involved, and we also consider the effects of previous leaf feeding on the expression of resistance in the field.

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Résumé Au cours d'expériences au laboratoire et en chambres climatisées nous avons comparé la croissance et le comportement de A. craccivora sur une lignée sensible (ICV-1) et deux lignées résistantes (ICV-11 et ICV-12) de V. unguiculata. Les vitesses de croissance des pucerons ont été beaucoup plus lentes sur les lignées résistantes que sur la lignée sensible, ce qui révèle une forte antibiose. De plus, les pucerons atterrissent invariablement en plus grand nombre sur la variété sensible. Par comparaison avec ICV-1, les atterrissages sur lignée résistante ICV-12 étaient plus nombreux sur les feuilles endommagées que sur les feuilles intactes; les disques de feuilles de cette même lignée étaient encore moins résistants.Les pucerons ont séjourné individuellement un temps plus long sur les lignées résistantes avant de faire leur premier sondage. Le temps consacré aux sondages ainsi que le temps précédant de choix entre départ ou maintien sur la feuille étaient plus longs avec les lignées résistantes.Ces résultats ont été discutés en fonction des mécanismes impliqués. Nous avons aussi examiné les effets de la consommation antérieure sur les manifestations de la résistance dans la nature.

     

Effect of the structure of phospholipid on the kinetics of intravesicle scooting of phospholipase A2

Action of pig pancreatic phospholipase A2 on vesicles of over 50 synthetic 1,2-diacylglycerol-3-phosphate derivatives and analogs is examined in the absence of any additives. In general, shorter acyl chains and small substituents on the phosphate make a better substrate, while phospholipids with large apolar substituents are not hydrolyzed. The interfacial turnover rate constant for scooting kinetics, ki, for the various phospholipids were from less than 0.1 to 1 per min. Intervesicle exchange of the bound enzyme is faster in vesicles of phospholipids with larger polar substituents, and it is promoted in the presence of anions like chloride, sulfate and thiocyanate. These factors lower the residence time of the enzyme on the bilayer and therefore effectively decrease the rate of hydrolysis. The apparent Km for the enzyme in the interface of anionic phospholipids in the presence of salts is in the 40 to 100 microM range which is 3- to 7-times larger than the dissociation constants for the bound enzyme measured by fluorescence enhancement of Trp-3. The quantum yield of the bound enzyme in vesicles of the various lipids is found to be up to 4-fold different. It is suggested that this difference is due to the E* + S to E*S equilibrium, where E*S has higher fluorescence intensity. The role of calcium in generating the enzyme binding site at the anionic interface, the role of anion anchoring site on the enzyme, and the relationship between the catalytic efficiency and the fluorescence quantum yields are discussed.     

Effects of beta-pinene on yeast membrane functions.

The effects of beta-pinene on yeast cells were studied. This terpene inhibited respiration with glucose or ethanol as the substrate. The inhibition depended on the ratio of the terpene to the amount of yeast cells; for a fixed concentration of pinene, inhibition decreased as the amount of yeast cells increased. Pinene also inhibited the pumping of protons and K+ transport, but this inhibition was more marked with with ethanol than with glucose as the substrate, indicating the mitochondrial localization of the inhibition. The studies on isolated mitochondria showed a series of effects, starting with the disappearance of the respiratory control and deenergization of the organelles and followed by an inhibition of respiration at higher concentrations of the terpene. The effect on respiration could be localized to the cytochrome b region of the electron transport chain. No effect could be detected on the activity of ATPase. The effects can be ascribed to a localization of pinene on membranes which was also accompanied by a decrease in the fluorescence polarization of diphenyl hexatriene, probably meaning an increase in the fluidity of the membrane, localized preferentially to the mitochondria.     

The antenna system of Rhodospirillum rubrum. Detection of macromolecular constituents not stainable by Coomassie brilliant blue in solubilized preparations of the B880 complex

A solubilized preparation of the major Rhodospirillum rubrum antenna complex (B880) was obtained by a described procedure and its polypeptide composition was analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Only two polypeptides of molecular weights close to 7000 were detected after staining the gels with Coomassie brilliant blue. However, several other constituents could be visualized by silver staining or by an immunochemical method. When the preparation was chromatographed on Sephacryl, some of the resulting fractions exhibited the characteristic B880 absorption spectrum and contained only the two proteins that were detectable with Coomassie brilliant blue. In those fractions the A ₂₈₀/A ₈₈₀ratio was 0.4, which indicated a significant improvement of the bacteriochlorophyll to protein ratio over the unchromatographed preparation (A ₂₈₀/A ₈₈₀=0.7). Other chromatography fractions lacked bacteriochlorophyll and contained a carotenoid which seemed to be bound to protein. The macromolecular constituents present in these latter fractions differed from those associated to the purified B880 complex in their electrophoretic moblities and/or in their staining properties. That suggested the possible existence of a carotenoprotein that did not result from the B880 complex upon loss of bacteriochlorophyll.     

The proα2 (V) collagen gene (COL5A2) maps to 2q14→2q32, syntenic to the proα1 (III) collagen locus (COL3A1)

Summary A recombinant probe specific for the pro2 chain of human Type V collagen has been used for the localization of the corresponding gene (COL5A2) to chromosome 2. Regional mapping by in situ hybridization and analysis of DNA from humanxrodent cell lines indicated that COL5A2 is confined within the segment 2q142q32, thus syntenic to the pro1 (III) collagen gene (COL3A1).     

Evidence for two waves of induction of DNA enzymes in stimulated human lymphocytes

The stimulation of human lymphocytes with phytohaemoagglutinin induces the appearance or increase of several enzymes of DNA metabolism [Pedrini etal., Biochem. Biophys. Res. Comm., 47:1221(1972)]. With long times of stimulation, two phenomena are observed; an increase in the levels of DNA polymerase, of a DNase acting on single-stranded DNA, and of an endonuclease, occurring between the third and fourth day, in parallel with a wave of DNA synthesis;a second wave of increase of the same enzymes and of DNA ligase,occurring between the fifth and eight day when the DNA replication rate, as measured by thymidine-pulses, has decreased to values close to the background.