Browsing by Author "Bandara, B. M. R."

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Herbicidal properties of invasive alien plants Dillenia suffruticosa and Prosopis juliflora against Brassica juncea and Pennisetum polystachion
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Kaushalya, W. D. D.; Bandara, N. C.; Damunupola, J. W.; Madawala, H. M. S. P.; Jayasuriya, K. M. G. G.; Wijesundara, D. S. A.; Bandara, B. M. R.
Synthetic pesticides can cause deleterious effects on human health and the environment. The rapid spread of invasive alien plants (IAPs) threatens biodiversity and the natural and semi-natural ecosystems. A strategy to address these problems is to develop eco-friendly plant-based pesticides from IAPs. In this study, the two IAPs, Dillenia suffruticosa (Griff.) Martelli. and Prosopis juliflora (Sw.) DC., were evaluated for their herbicidal properties against Brassica juncea (L.) Czern. (Bj) and Pennisetum polystachion (L.) Schult. (Pp). The dry leaf powders of IAPs, were separately extracted into dichloromethane-methanol (1:1) using a bottle extractor. The leaf powders and the concentrated leaf extracts were assayed for their inhibitory effects on seed germination and early seedling growth (shoot length, root length and biomass) of Bj and Pp using a Petri dish assay; 2-methyl-4-chlorophenoxyacetic acid (MCPA) and glufosinate were used as positive controls and distilled water and aqueous dimethyl sulfoxide as negative controls. Each treatment was done on 25 seeds in four replicates, in three trials. The IC50 values of the leaf powders and extracts expressed in equivalent amount of leaf powder for the inhibition of seed germination of Bj and Pp were as follows: 3.70 ± 0.38 and 3.10 ± 0.52 mg cm-2 (D. suffruticosa leaf powder against Bj and Pp, respectively); 1.55 ± 0.05 and 0.23 ± 0.06 mg cm-2 (P. juliflora leaf powder against Bj and Pp, respectively); 1.47 ± 0.07 mg cm-2 (D. suffruticosa leaf extract against Bj); 1.19 ± 0.53 mg cm-2 (P. juliflora leaf extract against Bj). Both IAPs were more effective on Pp than Bj (ANOVA, F = 70, p < 0.001). According to the results of the Kruskal- Wallis test, the leaf powders of P. juliflora (at 3.52 mg cm-2, 2 = 25.7, p < 0.001) and D. suffruticosa (at 17.62 mg cm-2, 2 = 24.3, p < 0.001) and the leaf extracts of P. juliflora (at 5.56 mg cm-2, 2 = 26.2, p < 0.001) and D. suffruticosa (at 8.27 mg cm-2, 2 = 25.6, p < 0.001) displayed more potent inhibitory effects on seed germination than glufosinate (at 4.4 µg cm-2) and MCPA (at 10.6 µg cm-2). Growth parameters of Bj and Pp decreased with increasing concentrations of leaf powders and extracts of IAPs (one-way ANOVA, p < 0.05). The leaves of P. juliflora and D. suffruticosa can be exploited to develop eco-friendly herbicides.
Screening of selected invasive plant extracts for antifungal activity against Colletotrichum gloeosporioides
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Karunarathna, T.C.M.F.; Damunupola, J.W.; Bandara, B. M. R.
High-quality ornamental plant products are needed for export-scale floriculture. A major barrier to provide high quality products is the wide prevalence of plant pathogenic diseases. Colletotrichum gloeosporioides causes diseases in several species of ornamental plants. Use of chemical fungicides can cause undesirable non-target effects and fungal resistance. The invasive plants that threat natural ecosystems, may serve as an inexpensive source for developing antifungal products that are devoid of the problems associated with synthetic fungicides. We examined the antifungal activity of 36 extracts (6 plants x 2 plant parts x 3 extract solvents) of 6 invasive plants, Mikania micrantha, Tithonia diversifolia, Lantana camara, Clusia rosea, Chromolaena odorata and Clidemia hirta against the pathogenic fungus C. gloeosporioides that was isolated from Dracaena reflexa leaf spots. PCR and sequencing for molecular characterization of the fungus was done at Genetech, Colombo. All the invasive plants were collected from the Central Province, Sri Lanka. Plants were washed, air-dried and powdered. Each powder was sequentially extracted into n-hexane, dichloromethane (DCM) and methanol at room temperature (RT) for 30 min using an ultrasonicator (40 kHz). Removal of solvents on a rotary evaporator gave the respective plant extracts. Each plant extract (2 mg/disc) was screened for antifungal activity against C . gloeosporioides using disc diffusion method by incubating for 3-5 days at RT . Standard fungicides mancozeb and propineb (50 µg/disc) served as positive controls. All assays were carried out in triplicate and repeated thrice in completely randomized design. The areas of inhibition were measured and analyzed using one-way ANOVA with Minitab 16 . The extracts of M . micrantha, T . diversifolia, C . odorata, L . camara and C . hirta showed varying degrees of antifungal activity against C . gloeosporioides while the extracts of C . rosea were inactive. The DCM leaf extract of M . micrantha (3.42 ± 0.34 cm2) and the DCM root extract of T . diversifolia (2.26 ± 0.24 cm2) displayed the highest area of inhibition; while mancozeb and propineb were 2.17 ± 0.14 and 1.29 ± 0.06 cm2, respectively. M . micrantha leaves and T . diversifolia roots could be potential sources for developing plant-based fungicides to be used in floriculture industry.