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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]

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]

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]

The study of the degradation of slats shows that P. noxius, just as R. lignosus, is capable of degrading lignin. Both pathogens are thus white rot fungi. In this framework, the comparison of the behaviour of these two fungi with that of Antropodia sp. , a known brown rot agent, is particularly illustrative. Lignin assays showed the tendency of R. lignosus to preferentially degrade lignin, while P. noxius preferentially degrades the polysaccharide fraction. Finally, both fungi also cause considerable changes in the residual lignin by modifying the monomer composition of the polymer. In vivo and in comparison to healthy tissues, there is a significant increase in the lignin content of infested tissues removed from the front of R. lignosus progression. It would appear that Hevea reacts by an increased synthesis of lignin. This reaction is ineffective, since the pathogen ultimately degrades the polymer. Such reaction is much less evident in case of attack by P. noxius. In terms of the monomer composition of lignin, there are changes in the tissues colonized for the longest times, comparable to that observed in vitro. [ABSTRACT FROM AUTHOR]