| Summary: | Cyanobacteria have the ability to fix atmospheric nitrogen to plant available forms; thus, useful in producing bio-fertilizers especially for rice cultivation. In this study, cyanobacteria were isolated from soil samples collected from 23 paddy fields in Kurunegala, Matale, Anuradhapura and Polonnaruwa Districts under IL1, IM3, DL1b and DL1c agro ecological regions, respectively. Soil pH, EC, active C and exchangeable K contents varied considerably among soils from four regions. Culturable cyanobacteria were isolated using Blue Green medium (pH 7) and thirteen isolates were tentatively identified based on morphological characteristics. Oscillatoria was the most common cyanobacteria among sampling sites in IL1, IM3 and DL1c agro ecological regions. Microsystis was the most prevalent unicellular group in IL1 and DL1c agro ecological regions. In DL1b, unicellular Aphanocapsa was commonly found followed by filamentous Pseudanabaena and Oscillatoria. From this research thirteen axenic cultures were established for further studies. The diversity of cyanobacteria was high in the regions with high diversity of paddy cultivated environments.
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