African Journal of Biotechnology Vol. 7 (15), pp. 2569-2572, 4 August, 2008 Available online at http://www.academicjournals.org/AJB ISSN 1684–5315 © 2008 Academic Journals
Full Length Research Paper
Use of phylloplane fungi as biocontrol agent against Colletotrichum leaf disease of rubber (Hevea brasiliensis Muell. Arg.) Evueh, G. A. and Ogbebor, N. O.*
Plant Protection Division, Rubber Research Institute of Nigeria, PMB 1049, Benin City. Accepted 4 March, 2008
Phylloplane fungi were used as biocontrol agent against Colletotrichum leaf disease of rubber (Hevea brasiliensis Muell. Arg.). Aspergillus sp. lysed the cytoplasm of Colletotrichum gloeosporioides on Potato Dextrose Agar. Trichophyton sp. and Gliocladium sp. antagonised C. gloeosporioides by overgrowing on it. Other phylloplanes used in this study such as Botrytis sp., Pleurothecium sp. and Staphylotrichum sp. exhibited weak antagonism on the pathogen while Gonatorrhodiella sp. and Syncephalastrum sp. showed different levels of zones of inhibition with the pathogen. Metabolites produced by Gonatorrhodiella sp. and Syncephalastrum sp. affected the pathogen by antibiosis. This finding showed that Trichocladium sp. and Trichophyton sp. exhibited the highest antagonistic effects on C. gloeosporioides. Key words: Para rubber, phylloplane fungi, biological control, disease management. INTRODUCTION Hevea brasiliensis (Muell. Arg.) commonly called para rubber, is an economic crop whose healthy existence is significant to its productivity (Rao, 1965). Rubber diseases are mainly caused by fungal pathogens (Igeleke, 1988; Begho, 1990). Colletotrichum gloeosporioides (Penz.) Sacc. is the causal agent of Colletotrichum leaf fall of rubber tree. It is one of the serious leaf diseases which affects the new flushes produced following the ‘wintering effect’, when the rubber tree loses its leaves during the dry season. The disease also affects young rubber plants under nursery conditions and when severe can lead to shoot die back (Rao, 1965; Webster and Baulkwill, 1989). The successful use of chemicals in the control of rubber diseases has been extensively reported by various scientists. However, the high cost of chemical fungicides limits its availability and use by small - scale farmers. Biological control for plant diseases is now receiving increasing attention, although the potential of biological control through the effect of phyllosphere antagonists has been realized for sometime. Several workers have investigated the use of biological control of plant diseases (Osando and Waudo, 1994; Tewari, 1995; Ogbebor and Adekunle, 2005). Osando and Waudo (1994) used various isolates of Trichoderma to control Armillaria root rot fungus of tea. They found that different isolates of Trichoderma sp. exhibited different level of antagonism against Armillaria root rot fungus. This study seeks to find possible phylloplane fungi as biocontrol agents against Colletotrichum leaf disease of rubber. MATERIALS AND METHODS Isolation of leaf pathogen Leaves of H. brasiliensis infected with C. gloeosporioides were collected from Rubber seedlings in Rubber Research Institute of Nigeria. Bits of 1 x 1 cm cut across lesions were surfaced sterilized by submerging in 0.1% of mercuric chloride for 1 min, after which it was rinsed in five changes of sterile distilled water. Then, they were placed on PDA. Isolation of phylloplane fungi
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Phylloplane fungi were isolated from healthy leaves of rubber plant
Afr. J. Biotechnol.
in RRIN nursery through leaf washing technique (Blakeman, 1981). Dilution method of Pelczar and Chan (1972) was employed and dilution factor of 10-4 was used. Pure isolate were established on antibiotic-amended PDA. Dual inoculation of leaf pathogen and potential antagonist on PDA Dual inoculation of the pathogen and an antagonist was set up. A 10 mm disc of the pathogen with similar size of each potential...
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