Browsing by Author "Jayasuriya, K. M. G. G."

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Effect of sugars, amino acids, hormones and microbial biofilm exudates on dormancy breaking of culturable soil microbial seed bank.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Wijepala, P. C.; Jayasena, P. G.; Singhalage, I. D.; Seneviratne, G.; Madawala, H. M. S. P.; Jayasuriya, K. M. G. G.
Soil microbial diversity is found to be beneficial for plant growth and productivity. The diversity has decreased to alarming level under stressful soil conditions and microbes form dormant structures like spores to withstand stressful soil conditions. Biofilm Biofertilizer (BFBF) is the most efficient product, newly introduced to the agricultural industry of Sri Lanka, which consists of different compounds like sugars, amino acids and hormones. These compounds assist in breaking the dormancy of microbial seed bank. However, effect of the compounds on the dormancy breaking has been poorly investigated. Therefore in the current study, the effect of glucose, tryphtophan, indole acetic acid (IAA), BFBF exudates on dormancy breaking and growing of culturable soil microbial seed bank was investigated. BFBF exudates and seven types of solutions were prepared by mixing glucose, tryptophan and IAA in different ratios and used them as treatments. Sterile distilled water was used in the control. Sieved (0.5 mm) and air dried garden soil was treated and incubated for 2 months under room temperature. Triplicated treatments were arranged according to completely randomized design. Then the dormancy breaking test was conducted on treated soil following the protocols developed by National Institute of Fundamental Studies. Bacterial colony count and average colony diameters under each treatment were recorded after 1, 2, 4 and 6 weeks. Fourier Transformed Infrared (FTIR) spectra were recorded for exudates and prepared solutions. The highest colony count was observed in BFBF exudate treatment throughout the experiment whereas highest diameter was different among treatments during the incubation period. The lowest colony count was recorded in soil treated by IAA. This implies that the bacterial growth was improved when compounds interacted. The study concludes that colony count and diameter varies among treatments. However, among all treatments, BFBF exudate was the best for microbial seed bank dormancy breaking.
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.