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The study was conducted to evaluate in vitro and in vivo control of fungal antagonists on Rigidoporus lignosus (klotzsch) Imaz in Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg. in the rain forest zone of Nigeria. In vitro assessments of biological agents were carried out in dixenic cultures in Petri plates. In vivo tests were carried out in the nursery using Hypocrea virens and Hypocrea jecorina . Significant differences were observed with the dual inoculations of fungal antagonists and R. lignosus inoculated the same day, and the antagonists inoculated 24 h before inoculation of R. lignosus . Hypocrea jecorina was most effective in the control of R. lignosus with percentage inhibition of 86.83 %. Hypocrea virens , H. jecorina , Trichoderma spirale , Trichoderma sp., Trichoderma sp. Pers, and Hypocrea lixii were effective on R. lignosus . Fungal antagonists inoculated 24 h before inoculation of R. lignosus exhibited higher inhibitory efficacies than antagonists and R. lignosus inoculated the same day. In the in vivo evaluation of fungi antagonists on R. lignosus , seedlings in H. jecorina treatment at 60 d and H. virens treatment at 150 d after inoculations respectively had the highest plant heaths (highest length of stem and length of tap rot, lowest plant death, and least foliar symptom) compared to the control. Mortality rate was higher at 60 d after inoculation and decline from the third months onward. Significant differences were observed between the control and R. lignosus treatment in all the parameters evaluated. [ABSTRACT FROM AUTHOR]

Highlights: [•] The RIL activity at low pH value is controlled by an ionizable residue present in its active site. [•] DEPC derivatization of accessible His of RlL affect the kinetic behavior of RlL with pH and ionic strength. [•] Main role of His-457 in the control of the catalytic activity of laccase from Rigidoporus lignosus. [Copyright &y& Elsevier]

The structure and thermal stability of a laccase from Rigidoporus lignosus (Rl) was analysed by Fourier-transform infrared (FT-IR) spectroscopy. The enzyme was depleted of copper atoms, then part of the apoenzyme was re-metalled and these two forms of the protein were analysed as well. The enzymatic activity, lost by the removal of copper atoms, was restored in the re-metalled apoenzyme and resulted similar to that of native protein. The infrared data indicated that the enzyme contains a large amount of β-sheets and a small content of α-helices, and it displayed a marked thermostability showing the Tm at 92.5 °C. The apoenzyme and the re-metalled apoenzyme did not show remarkable differences in the secondary structure with respect to the native protein, but the thermal stability of the apoenzyme was dramatically reduced showing a Tm close to 72 °C, while the re-metalled protein displayed the Tm at 90 °C. These data indicate that copper atoms, beside their role in catalytic activity, play also an important role on the stabilisation of the structure of Rl laccase. About 35% of the polypeptide chain is buried and/or constitutes a particular compact structure, which, beside copper atoms, is probably involved in the high thermal stability of the protein. Another small part of the structure is particularly sensitive to high temperatures and it could be the cause of the loss of enzymatic activity when the temperature is raised above 45–50 °C. [Copyright &y& Elsevier]

Early detection of root diseases is a great problem in perennial crops, especially in rubber tree. Planters are continually confronted with the balance of efficiency/cost of the detection. Therefore, a trial was set up to compare three sampling densities and four exposure techniques for detection of white root rot in rubber plantings. A complete census of all trees is the only efficient method of detection in a control program. When reducing the sampling density, a lot of infected trees are not detected and they remain an inoculum source for the spread of the disease. Mulching for one month followed by root exposure is the best technique to reveal the presence of the fungus. The sampling density is of greater significance than the infection exposure method. [Copyright &y& Elsevier]