Antifungal Activity of Forty Higher Plants against Phytopathogenic Fungi

Abstract

Every year a lot of crop damage is caused by various diseases and among them fungal diseases are very common [1][2] . Although the use of synthetic fungicides in plant disease control have shown its fruitfulness in the improvement of agriculture, several of these have been found to display side-effects in the form of carcinogenicity, detrimental effects and other residual toxicities. The alternative choice therefore would be the use of botanical fungicides, which are advocated to be largely non-phytotoxic, systematic and easily biodegradable in nature 2-3 .It is believed that antimicrobial agents are present in higher plants. Some recent researches on antifungal activity of extracts of several higher plants have indicated the possibility of their exploitation as natural antifungal agents for control of plant diseases 1,4-8 but as yet little has been known in this field.So, an attempt has been made to search the higher plants of Bangladesh for active antifungal agent, which may be useful therapeutically against the fungal diseases of crops prevalent in the country.The plant materials (whole plant, aerial parts, leaf, root, bark and rhizome) were collected fresh from various localities in Chittagong, Cox's Bazar, Rangamati and Moheshkhali areas and were identified by one of us. A set of voucher herbarium specimens was made for each collection and these vouchers have been preserved in the herbarium Bangladesh Council of Scientific and Industrial Research (BCSIR) Laboratories, Chittagong. Plant materials were cut into small pieces (1-2 cm), air-dried, powdered mechanically and extracted with 80% ethanol. The extracts were filtered and concentrated to near dryness under reduced pressure and low temperature (40°-50°C) with the help of rotary vacuum evaporator. In vitro antifungal activity of the extract was done by poisoned food technique 9 . Potato dextrose agar (PDA) medium was used for the culture of fungi. Each extract was redissolved in specific volume of absolute ehanol and mixed with sterilized melted PDA medium to obtain the desired concentration (1 mg/ml.) and this was poured in sterilized petriplates (20 ml/plate). At the center of each Petri plate 5-days-old fungal mycelial block (5 mm in diametre) was inoculated, which was subsequently incubated at 25° ± 1°C. The diameter of each fungal colony was measured after 3-5 days of incubation. Nystatin (100 μg/ml) was used as a standard antifungal drug for comparison of results under identical conditions. The percent of mycelial growth inhibition of the test fungus was calculated as described earlier 10 .The results of in vitro antifungal activity of ethanolic extract of 40 higher plants belonging to 23 families are summarized in Table 1. Plant extracts that inhibited more than 50% of the normal growth were considered as effective. The degree of susceptibility varied depending on the plant species. Among the plants screened, 11 showed antifungal activity against one or more phytopathogenic fungi tested. Extract of Hedychium thyrsiformae, Clerodendrum viscosum and ...

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