International Research Symposium on Pure and Applied Sciences (IRSPAS)
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Item Potential of using leaf extract of Annona glabra as a novel, green source for the synthesis of silver nanoparticles(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Paragodaarachchi, Y. L.; Wickramarachchi, P. A. S. R.This study aims at investigating the potential of using the leaf extract of Annona glabra for the green synthesis of silver nanoparticles (AgNPs) and optimization of process parameters to obtain nanoparticles with narrow size range. A. glabra is a very troublesome invasive species, where it grows in estuaries and stifles mangroves. Phytochemicals present in plant extracts are capable of acting as reducing and stabilizing agents during the synthesis of nanoparticles. The active ingredient responsible for the reduction of Ag+ ions and stabilization of silver nanoparticles varies depending on the plant extract used. Aqueous leaf extracts of A. glabra were prepared by heating chopped leaves (20.0 g) with water (100.0 mL) at different temperatures (60 – 100 °C) for 1 hour. AgNPs were synthesized by incubating silver nitrate (20.00 mL), as the precursor, with the plant extract, as the reducing agent. The mixture was incubated for 3 hours under slow agitation and dark conditions. Amount of plant extract (2 – 10 mL), concentration of silver nitrate (1 – 10 mM) and incubation time (0.5 - 24 hours) were changed to find the optimum conditions for the synthesis of AgNPs. Formation of silver nanoparticles were confirmed by the color change of the mixture from faint yellow to light brown and the surface plasmon resonance band around 420 nm. The size of the nanoparticles formed were measured by dynamic light scattering (DLS).The surface plasmon resonance peak maxima was detected at 417 nm for the biofabricated AgNPs using A. glabra leaf extract. With the increase of plant extract, size of AgNPs increased from 206 – 314 nm. Particle size increased from 183 – 224 nm with increase of silver nitrate concentration. The plant extract made at 100 °C produced the smallest nanoparticles. The size of AgNPs were polydispersed in a range of 10 – 190 nm displaying a narrower size range which falls within the general nanoscale. The optimum formulation was obtained at 100 °C extraction temperature for the leaf extract, 2 mL of plant extract, 1 mM silver nitrate and 7 hours of incubation. Leaf extract of A. glabra can be used for the synthesis of AgNPs and only low concentrations of leaf extract of A. glabra are needed to synthesize silver nanoparticles.Item Effect of aqueous extracts of Annona glabra plant and extracellular metabolites of two Trichoderma species on the survival of larval Culex quinquefasciatus and eggs of Aedes aegypti(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Aberathna, A. A. A. U.; Ranasinghe, H. A. K.; Rajapaksha, R. D. T.; Amarasinghe, L. D.Phytochemicals constitute a rich source of bioactive chemicals and some microbial products carry selective toxicity to many insect species, hence those are considered as alternatives to chemical insecticides. This study aimed to determine the potential of concentration gradient of Annona glabra aqueous leaf and fruit extracts for the mortality of third instar larvae of Culex quinquefasciatus; and to determine the ovicidal activity of extracellular metabolites of Trichoderma harzianum and Trichoderma viride at concentration gradient of 100, 200, 300, 400, 500 g/L on field collected eggs of Aedes aegypti with four replicates including controls for all bioassays. For the bioassays, aqueous crude extraction of plant materials was done by overnight shaking and extraction of extracellular metabolites of T . harzianum and T . viride was done using Richard ’ s broth . Study revealed that LC50 for A . glabra aqueous leaf extract for third instar larvae of Cu . quinquefasciatus was 16.26 g/L and 8.29 g/L in 24 hr and 48 hr exposure respectively (Minitab 14, Probit analysis). LC50 for A . glabra aqueous fruit extract, for third instar larvae of Cu . quinquefasciatus were higher than the LC50 for A . glabra leaf extract; 422.54 g/L and 114.01 g/L in 24 hr and 48 hr exposure respectively. 100% mortality was observed in mosquito larvae under 69.86 g/L of leaf and 1000g/L of fruit extract treatments after 24 hours of exposure. Mosquito larvae mortality compared to those in the control group reveals that the mortality of mosquito larvae may be due to the toxic compounds found in the plant. Although literature has shown that most Trichoderma strains produce volatiles and non-volatile toxic metabolites, significant ovicidal activity of extracellular metabolites of T . harzianum and T . viride on field collected eggs of Ae . aegypti was not observed (One-Way ANOVA; P>0.05) after 24 hr of exposure. The results of the study revealed that, both A . glabra fruit and leaf extracts are potential mosquito larvicides for Cu . quinquefasciatus. This may contribute to the formulation of an environmentally friendly measure to control Cu . quinquefasciatus vector mosquito species, which is a vital need to overcome the use of synthetic insecticides.Item Nematicidal activity of Annona glabra aqueous plant extract and extracellular metabolites of two Trichoderma species on root knot nematode Meloidogyne incognita(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Lakmini, W. V.; Amarasinghe, L. D.The root knot nematode, Meloidogyne incognita, is the most widespread and serious nematode pest damaging root systems of a variety of agricultural and ornamental crops in tropical and subtropical countries throughout the world. Management of this nematode species by integrated application of synthetic insecticides and variety of non-chemical methods are suggested but many are not very effective. Even though, mature leaf extraction of Annona glabra (pond apple or alligator apple; Family Annonaceae), contains some insecticidal properties, there is no clear evidence of its nematicidal effect. This study was conducted to find the efficacy of aqueous leaf extracts of A . glabra, on root knot nematode species, M . incognita attacking spinach plants in comparison to the extracellular metabolites of two species of antagonistic fungi, Trichoderma harzianum and T . viride. Polythene bags were filled with nematode free soil. Single spinach plants having 6 leaves were transplanted into each pots. 10-12 mature adult female nematodes were added to spinach plant pots. These pots were kept outdoor for 2 weeks prior to inoculating the treatments. Above ground growth parameters such as number of total leaves, length of stem, below ground growth parameters such as number of root galls, root length were used to determine nematicidal effect on the nematode infested plants. One-way ANOVA was performed to test whether there is significant difference (95% confidence interval) between each concentrations of treatments. Results revealed that spinach plants treated with A . glabra plant aqueous leaf extract showed highest stem length and higher number of leaves compared to the control treatment. Nematicidal effect of A . glabra aqueous extract is more effective than T . viride but lower than T . harzianum when considering above ground plant growth parameters. 125 g/L of A . glabra plant aqueous leaf extract and 140 mg/L of fungal mycelium T . viride extract and 100 mg/L of T . harzianum concentrations showed the highest effect for controlling root knot nematodes. This study concludes that there is a nematicidal activity of A . glabra aqueous plant leaf extract even at lowest concentration (100 mg/L) and extracellular metabolites of T . harzianum and T . viride on M . incognita.