IRSPAS 2018

Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/19084

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Author: search.filters.author.Amarasinghe, L. D.Subject: search.filters.subject.Annona glabra

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    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.
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    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.