IRSPAS 2016

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Assessment of phytochemicals and antifungal effect of Croton aromaticus against postharvest fungal pathogens isolated from tropical fruits
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Wijesundara, S.A.D.T.L.; Kannangara, S.; Abeywickrama, K.
Chemical control using synthetic chemical fungicides is still the most common method of controlling postharvest diseases of fruits. Plant extracts which are rich in antimicrobial secondary metabolites such as terpinoids, alkaloids, saponins and flavonoids could be possible alternatives for synthetic fungicides. Current study was focused on evaluating the antifungal effect of ethanolic extract of Croton aromaticus (Kappettiya) leaves in vitro against mycelial growth and the spore germination of postharvest fungal pathogens isolated from fruits of banana (Colletotrichum musae, Rhizopus sp., Lasiodiplodia theobromae) papaya (Rhizopus stolonifer, Colletotrichum gleosporioides, Lasiodiplodia theobromae) and mango (Alternaria alternata, Pestalotiopsis mangiferae, Lasiodiplodia theobromae). Surface sterilized diseased banana, papaya and mango fruit tissues were cultured on PDA plates in order to obtain pure cultures of possible fungi and they were identified by morphological and microscopic characteristics, using identification keys. Inhibitory effect of the ethanolic extract of C. aromaticus against test pathogens were investigated by well diffusion method using PDA medium, by incorporating crude extract dissolved in DMSO, ranging from 1 mg/ml up to 300 mg/ml concentrations along with the positive (Captan) and negative (DMSO) controls. Significant (P < 0.05) inhibitory effects were exhibited by the ethanolic extract of C. aromaticus leaves against all test pathogens except L. theobromae. The highest mycelial growth and spore germination inhibition of most of the pathogens were observed at 100 mg/ml. The lowest Minimum Inhibitory Concentration of the leaf extract (5 mg/ml) was observed for spore germination inhibition of C. gleosporioides and P. mangiferae. TLC analysis revealed four compounds having Rf values of 0.551, 0.672, 0.810 and 0.913. Phytochemical screening of ethanolic extract revealed the presence of alkaloids, terpenoids, quinones, phytosterols and flavonoids. Current findings indicate the potential use of ethanolic extract of C. aromaticus leaves in controlling banana, papaya and mango postharvest fungal pathogens in vitro.
Screening endophytic fungi of Macromitrium sp. for potential degradation of PAHs
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Ambadeniya, A.R.P.D.U.K.R.; Kannangara, S.; Abeywickrama, K.
With rapid industrialization and urbanization, emission of air pollutants to the atmosphere has been increasing rapidly for several decades. Out of many pollutants, polyaromatic hydrocarbons (PAHs) take a prime advertence due to their toxicity, mutagenecity, carcinogenicity and long persistence in nature. Therefore, removal of these is one of the major cruxes that the modern world faces. In the present study, an effort was made to isolate and identify endophytic fungi in a moss (Macromitrium sp.) found in a polluted area (Sapugaskanda) and a less polluted area (Hettimulla), and to investigate their ability to degrade PAHs (naphthalene and phenanthrene). It was hypothesized that endophytes isolated from the moss can degrade PAHs and endophytes from polluted area have a higher ability to degrade PAHs compared to those isolated from the less polluted area. Moss plants from Sapugaskanda and Hettimulla area were used. Surface sterilized and trimmed moss plant pieces were placed on Malt Extract Agar and incubated for 10 days at room temperature. Percentage frequency of occurrence of each fungus grown was calculated. Utilization and degradation of PAHs by each of the fungus was assessed using a plate assay and a spectrophotometric analysis. Thirty six isolates were recovered from samples from Sapugaskanda area, 21 from Hettimulla and 6 were common to both areas. Highest frequency of occurrence was observed in Eupenicillium sp.2 (95.0%) in samples from Sapugaskanda and white sterile sp.7 (32.5%) for Hettimulla. Highest PAH utilization with the highest colony diameter, was recorded for Nigrospora oryzae for naphthalene (85.2 mm) and phenanthrene (59.5 mm). Almost all isolates from Hettimulla demonstrated low colony diameters. According to spectrophotometric analysis, highest degradation was observed with Penicillium oxalicum for naphthalene (98.60%) and Nigrospora oryzae against phenanthrene (98.02%). Almost all isolates in samples from Hettimulla area displayed poor degradation ability. The findings of the current study clearly reveal that Macromitrium sp. in Sapugaskanda harbours higher number of endophytic fungi than that in Hettimulla and most of them have a considerable ability to utilize and degrade PAHs in contrast to that in Hettimulla. It could be speculated that those endophytic fungi in Macromitrium sp. of Sapugaskanda, could be potential sources of fungal bioremediation. Further, they have potential practical application in removing PAHs from contaminated sites.