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The white rot fungus Rigidoporus lignosus produces substantial amounts of extracellular laccase, a multicopper blue oxidase which is capable of oxidizing a wide range of organic substrates. Laccase production can be greatly enhanced in liquid cultures supplemented with various aromatic and phenolic compounds. The maximum enzyme activity was reached at the 21st or 24th day of fungal cultivation after the addition of inducers. The zymograms of extracellular fluid of culture preparation in the presence of inducers, at maximum activity day, revealed two bands with enzymatic activity, called Lac1 and Lac2, having different intensities. Lac2 band shows the higher intensity which changed with the different inducers. Laccase induction can be also obtained by adding to the culture medium olive mill wastewaters, which shows a high content of phenolic compounds [ABSTRACT FROM AUTHOR]

A study was conducted to determine the spatial distribution of somatic incompatibility groups (SIGs) in Rigidoporus lignosus populations responsible for white root disease in a south Sumatera rubber plantation. Most isolates colonizing the stumps were somatically compatible with isolates from either a nearby stump or a living rubber tree, which suggested evidence of stump-to-tree or stump-to-stump clonal growth of the fungus. SIGs of R. lignosus occupied an area territorially in which the minimum size estimate for the largest genotype was 25?m in length. [ABSTRACT FROM AUTHOR]

A comparative study has been performed on five native laccases purified from the three basidiomycete fungi Pleurotus ostreatus, Rigidoporus lignosus, and Trametes trogii to relate their different catalytic capacities to their structural properties. Spectroscopic absorption features and EPR spectra at various pH values of the five enzymes are very similar and typical of the blue oxidases. The analysis of the dependence of kinetic parameters on pH suggested that a histidine residue is involved in the binding of nonphenolic substrates, whereas both a histidine and an acidic residue may be involved in the binding of phenolic compounds. His and an Asp residue are indeed found at the bottom of a cavity which may be regarded as a suitable substrate channel for approaching to type 1 copper in the 3D homology models of the two laccases from Pleuorotus ostreatus (POXC and POXA1b) whose sequences are known. [ABSTRACT FROM AUTHOR]

Growth and differentiation of mycelial strands in Rigidoporus lignosus have been shown to depend on suitable combinations of the pH of the media and the nature of the nitrogen and carbon sources. Amino acids as sole nitrogen sources gave rise to vegetative mycelium. At pH 4.5, growth and mycelial strand differentiation required asparagine, as the fungus failed to grow in the absence of this amino acid. However, at pH 6, differentiation of strands occurred appreciably in asparagine-deficient media, suggesting a close balance between pH and amino acid requirements. Ammonium was required for strand differentiation, while nitrate, as a sole nitrogen source, maintained the fungus undifferentiated. Of the carbohydrates tested, only glucose, fructose and mannose supported strand differentiation. Starch was found to be particularly effective in promoting growth of vegetative mycelium. Strand differentiation required more specific conditions than growth of the vegetative mycelium. [ABSTRACT FROM AUTHOR]

Two root-rot fungi, Rigidoporus lignosus and Phellinus noxius are the causal agents of severe damage in Ivory Coast rubber tree, Hevea brasiliensis, plantations. Mathematical investigations were made using data from a previous 6 year long epidemiological survey. Modelling of spatial spread of the pathogens and mortality of the infected trees, lead to simulations of the quantitative evolution versus time of root diseases. The theoretical kinetics obtained revealed intra and interspecific variability among the studied stands with respect to the damage caused.

Pathogenicity of isolates of R. lignosus and P. noxius collected from rubber and forest trees, was tested on young rubber plants (Hevea brasiliensis) using a technique of artificial inoculation under controlled conditions (e. g. soil moisture). After two months, almost all the plants inoculated with various isolated of R. lignosus were infected and differences in virulence were apparent. After five months, these differences were reflected in the mortality rates of the inoculated plants. For some isolates the attack begins early and abruptly, whereas for others, symptoms appear more gradually. With P. noxius, differences appear also very distinctly in the pathogenicity among the isolates during the entire duration of the experiment. Principal-component analysis of the data recorded has demonstrated variations in pathogenicity among populations of R. lignosus and of P. noxius. The fact must be borne in mind when control methods of these diseases of rubber tree are developed. [ABSTRACT FROM AUTHOR]

Copyright of European Journal of Forest Pathology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aggression of Hevea brasiliensis roots by two root-rot fungi, Rigidoporus lignosus and Phellinus noxius is studied at cellular level. Ultrastructural observations reveal the root penetration and tissues colonization by the fungal hyphae, showing clearly alteration in the host cell wall, leading to the root decays This paper describes the different mechanisms used by these two fungi in degrading lignified and non lignified tissues. [ABSTRACT FROM AUTHOR]

Copyright of European Journal of Forest Pathology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Three phenol oxidases, of which two are excreted by Rigidoporus lignosus and one by Phellinus noxius, have been isolated and purified from culture filtrates. Based on their substrate specificities and spectral characteristics, these enzymes are p-diphenol : oxygen oxidoreductases (laccases; EC 1.10.3.2). A number of their physicochemical properties have been determined. The fact that the two parasites excrete laccases indicates that they belong to the group of lignin degrading (white rot) fungi. Laccase L1 from R. lignosus was purified to homogeneity. [ABSTRACT FROM AUTHOR]