Browsing by Author "Premachandra, J. A. H. P."

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Isolation and identification of litter decomposing fungi in Nagacholai Forest Reserve, Mullaitivu, Sri Lanka
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Bopitiya, B. D. S. S.; Dewangani, H. G. N.; Perera, H. W. K.; Premachandra, J. A. H. P.; Senevirathna, M. A. T. M.; Kalpani, N. N.; Kodituwakku, T. D.; Kannangara, S.
Nagacholai Forest Reserve, which was disturbed by local terrorism before 2009, is located in Mullaitivu District in the Northern Province of Sri Lanka. It is a tropical dry zone forest, administrated by the Department of Forest Conservation, Sri Lanka. Litter-fall and subsequent nutrient release from decomposing litter are crucial processes that regulate the nutrient availability and the nutrient cycling in soil, as well as the plant growth in forest ecosystems. Litter decomposition rates of forest ecosystems are governed by both biotic and abiotic factors. Therefore, the present study was conducted to study soil characteristics such as pH and electrical conductivity and to isolate and identify the litter decomposing fungi of the Nagacholai forest. Soil and litter were collected randomly by placing 0.5 m X 0.5 m size quadrats on the forest floor. The pH and electrical conductivity of each soil sample were determined by following standard methods. Litter decomposing fungi were isolated from leaf discs (1 mm X 1 mm) obtained from the collected litter following washing and plating method using sterilized distilled water. Pure cultures of isolated fungi were maintained at 28 °C in PDA and morphologically identified using identification keys. The low moisture content in the soil was reflected by brown colour, sandy-podzolic soil. The high proportion of less decomposed, dense litter layer reflected the low decomposition rate due to decelerated soil microbial activity and low water availability. Soil pH was within the range of 6.34 – 6.80 and electrical conductivity at 30 °C varied between 1.23 – 1.57 mS cm-1. Five different fungal species were isolated in high frequencies (50%>) from leaf litter, while four of them were identified up to the genus level based on their vegetative and reproductive morphology (i.e. Mucor sp., Aspergillus sp., Candida sp. and Pestalotiopsis sp.). The remaining unidentified species produced white colour colonies and branched, hyaline, septate hyphae without showing any sexual reproductive structure. Mucor, Aspergillus and Pestalotiopsis are some of the common fungal decomposers found in most of the forests of different climatic zones. However, Candida is a filamentous yeast, which is not frequently reported as a decomposer in terrestrial ecosystems, but found to be a member of the normal soil microflora in forests as secondary sugar fungi. Therefore, Mucor, Aspergillus and Pestalotiopsis could be identified as the most prominent genera of litter decomposing fungi in the Nagacholai forest. Nevertheless, this preliminary study needs to be elaborated further to confirm their identity up to species level using molecular techniques
Isolation of mycorrhizal fungi in selected epiphytic orchids and investigation of the effect of potential host bark extracts on seed germination under in vitro condition.
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Premachandra, J. A. H. P.; Senanayake, S. P.
Orchids (Family: Orchidaceae) are one of the largest, diverse plant groups in the world with high ornamental value. Orchid seed germination, in nature, is reported to be influenced by the mycorrizal fungi associated in the bark of the host plants. These fungi penetrate the seeds by their hyphae and supply the nutrients for developing embryo resulting the formation of a globular shape structures referred as protocoms. Fungal hyphae infect the cortical cells of the orchids and forming pelotons, that are digested by the orchid cells for their nutrition. This study was focused on isolation of mycorrhizal fungi from six selected epiphytic orchids: Dendrobium aphyllum, Dendrobium sp., Bulbophyllum sp., Eria sp., Coelogyne sp., an unidentified species, and evaluation of in vitro seed germination using host bark extracts inoculated with isolated fungi from orchid roots. Specimens of wild orchids and the host plants were collected from their natural habitats in low-land wet zone and montane zone in Sri Lanka. The mycorrhizal fungi in roots of selected orchid species were isolated and identified as Trichoderma sp. and Rhizoctonia sp. by comparing with the authenticated morphological characters. Preliminary phytochemical screening was performed for each bark extract of host plants using TLC. Presence of secondary metabolites including alkaloids, flavonoids, terpenoids and phenolic were observed in all the bark extracts. According to the spot observations of TLC, although similar type of secondary metabolites was present in the bark extracts of hosts plants, intensity of the secondary metabolites was detected as different. The TLC analysis revealed the presence of high concentration of chemical compounds in methanolic and aqueous extracts while less amounts were in dichloromethane and hexane extracts. In vitro seed germination of the orchid species was assessed using the V/V basis of host bark extracts with the inoculation of isolated fungi from orchid roots. Effect of host bark extracts with mycorrhizal fungi inoculum on seed germination of orchid seeds was analyzed by performing two-way ANOVA using Minitab statistical software. Comparatively high percentage of seeds were germinated in the aqueous extracts (~30%) and hexane extracts (~25%) while very low percentage was in methanolic (0%) and dichloromethane (~0%) extracts of host barks. The findings suggest that secondary metabolites present in the barks of the plants influence the promotion or inhibition of the orchid seed germination whereas fungal inoculation too has a significant effect on orchid seed germination.