PURSE 2013

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Browsing PURSE 2013 by Author "Adikaram, N. K. B."

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    Antagonistic activity of Trichoderma isolates on pathogenic fungi, colletotrichum musae, colletotrichum acutatum and Botryodiplodia theobromae
    (The university of Peradeniya, 2014-07-04) Janaththani, P.; Adikaram, N. K. B.; Sooriyapathirana, S. D. S. S.; Dhanapala, M. P. C. S.
    Plant disease management is an uphill task. Biological control is hailed as a safe approach to manage plant diseases. Trichoderma is a soil inhabitant and it is well known as a potential biological agent to control fungal pathogens of plants. Several commercial biological products based on Trichoderma are available in the international market. However, Trichoderma-based products are not available in Sri Lanka. If native strains of Trichoderma can be isolated from the environment and tested for their antifungal activity against common phytopathogenic fungi, such isolates can be used to control pathogens. Therefore, the present study was conducted to assess the antagonistic activity of Trichoderma isolates on three selected postharvest pathogenic fungi of common fruit species in Sri Lanka, namely Colletotrichum musae, Colletotrichum acutatum and Botryodiplodia theobroma. Three soil samples were collected from the premises of the University of Peradeniya and another soil sample was collected from a tea estate in Kandy. Soil samples were suspended separately in sterile distilled water and suspensions were filtered and used to make a dilution series . One ml of each dilution was spread on a Potato Dextrose Agar (PDA) plate. After three days of incubation at room temperature, Trichoderma colonies were identified by observing the colony and conidial morphology. Ten pure cultures of Trichoderma isolates were recovered and labeled A to J. Pure cultures of postharvest pathogenic fungi, C. musae, C. acutatum and B. theobromae, were obtained from the Plant Pathology Laboratory, Department of Botany, University of Peradeniya. Suspensions of conidia were prepared from fully grown cultures of Trichoderma isolates, C. musae and C. acutatum. The concentration of conidia suspensions of Trichoderma isolates was adjusted to and the concentration of conidia suspensions of the two pathogenic fungi was adjusted to . For B. theobromae mycelium discs were picked from the fully grown cultures as spore formation was minimal. A bioassay was conducted to test the antagonistic activity of Trichoderma on three fungal pathogens. Two wells were cut on each PDA plate using a one cm diameter cork borer. In each plate, one well was filled with 25 μl of Trichoderma conidial suspension and the other well was filled with 200 μl of conidial suspension of either C. musae or C. acutatum. For B. theobromae, a mycelium disc was placed in the well. After incubation, the diameter of Trichoderma colony and the pathogenic fungal colony was measured daily for seven consecutive days. With Trichoderma isolates C, D and E, C. musae colonies stopped growing after four days of incubation and these Trichoderma isolates started to grow over C. musae colonies and the entire plates were covered with Trichoderma isolates on the seventh day, inferring the effectivity of isolates C, D and E against C. musae. The isolate G started to grow over C. acutatum colony after five days and was considered as effective against C. acutatum. Even though, all the isolates except G, started to grow over on B. theobromae, none of them had a significant effect. The Trichoderma isolates A, B, F, H, I and J did not exhibit a significant effect against any of these three pathogenic fungi. The Trichoderma isolates with antifungal activity must be further studied to formulate them as biopesticides and to understand their mode of action
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    In vitro antimicrobial activity of leaf exreacts of Magifera zeylanica
    (The University of Peradeniya, 2013-07-04) Dhanarisi, H. K. J.; Jayatilake, J. A. M. S.; Adikaram, N. K. B.
    Natural products have been used as a source for many drugs from the very dawn of medicine. With the evolution of resistance by microorganisms to present antimicrobials, the need for novel discoveries is urgent. Many researchers have demonstrated antimicrobial effects of Mangifera indica plant extracts. This study was undertaken to find out the antimicrobial activity of leaf extracts of Mangifera zeylanica which is an endemic plant in Sri Lanka. The leaves of a Mangifera zeylanica plant (identity confirmed) were collected from the Gannoruwa forest. Leaf extracts were prepared by the maceration method using water at room temperature, water at celsius 70, boiled water and ethanol. Antimicrobial effect of the plant extract at a concentration of 25mg/ml was tested against six isolates of bacteria; Staphylococcus aureus (NTCC 6571), Escherichia coli (NTCC 10417), Pseudomonas aerugenosa (NTCC 10662), Streptococcus pyogenes, Enterococcus faecalis and Methiciline resistant Staphylococcus aureus (MRSA) and five species of Candida; Candida albicans (ATCC 90028), Candida parapsilosis (ATCC 22019), Candida krusei (ATCC 6258), Candida glabrata (ATCC 90030), Candida tropicalis (ATCC 13803) using the agar well diffusion method. Minimum inhibitory concentrations (MIC) were determined for the extracts with high activity using the agar dilution method. When the diameter of the zones of inhibition was considered, the highest antimicrobial activity was detected against S. aureus followed by E. faecalis, E. coli and P. aerugenosa. Noticeable antimicrobial activity was detected against C. parapsilosis, followed by C. glabrata, C. krusei and C. tropicalis except C. albicans. Ethanol and celsius 70 water extracts showed higher antimicrobial activity. For the ethanol extract, the MIC value for both S. aureus and MRSA was 0.2 mg/ml. E. faecalis had a MIC value of 0.8 mg/ml. The MIC value for P. aerugenosa was 1.6 mg/ml and for E. coli MIC was 3.2 mg/ml. MIC value for C. krusei, C. prapsilosis and C. glabrata was 0.1mg/ml while the MIC value for C. tropicalis was 12.8 mg/ml. For the celsius 70 water extract, both S. aureus and MRSA showed a MIC value of 0.4 mg/ml. MIC value for E. faecalis was 1.6 mg/ml. MIC value for C. prapsilosis was 0.1mg/ml and the MIC value for C. krusei was 0.2mg/ml. C. glabrata had a MIC value of 0.8 mg/ml. Leaf extracts of Mangifera zeylanica under different conditions, exhibit marked antimicrobial activity. Ethanol and celsius 70 water extracts are effective against many microorganisms including S. aureus, E. faecalis, P. aerugenosa and non-albicans Candida.