Browsing by Author "Herath, H.M."

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First evidence of epiphytic marine algae Acrochaete leptochaete identified from Beruwala reef, Sri Lanka by DNA barcoding
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Weralupitiya, C.M.; Herath, H.M.; Wanigatunge, R.P.
Several green microalgal species that grow as epiphytes and/or endophytes associated with seaweeds have been identified from different locations worldwide. The composition of epiphytic marine algae in a marine ecosystem is an important indicator of environmental alterations. However, there are no previous records on epiphytic marine microalgae in the Sri Lankan coast. Therefore, this study aimed at identifying epiphytic marine microalgae inhabiting marine macroalgae in the Barbarian reef, Beruwala, and provides the first evidence of an epiphytic micro chlorophyte colonized within the seaweed genera from all the three marine macroalgal divisions. Morphologically different macroalgal specimens were collected in September 2018 from the Barbarian reef, Beruwala and they were identified using macroscopic and microscopic characters within two days of sample collection. DNA was extracted from the algal thalli and the nuclear ribosomal DNA Internal Transcribed Spacer regions (nrDNA ITS1-5.8S-ITS2, 650 bp) were amplified by polymerase chain reaction (PCR) from the extracted DNA using a primer pair (ITS1 and ITS4) specific for micro chlorophytes. PCR products were unidirectionally sequenced by the Sanger sequencing method using the forward primer. Sequences were checked and edited using BIOEDIT software version 7.2.6 and aligned with the nucleotide database (blastn) in National Centre for Biotechnology Information (NCBI). According to the morphological characterization of the macroalgae, nine, three and seven genera belonged to the Divisions Chlorophyta, Phaeophyta and Rhodophyta, respectively. The nrDNA ITS1-5.8S-ITS2 sequences showed a 95- 96% similarity to Acrochaete leptochaete (JN104107.1) for the macroalgae Chaetomorpha (Division Chlorophyta), Padina (Division Phaeophyta) and Gracillaria (Division Rhodophyta). According to the fact that 93% sequence similarity should be achieved with that of the Genbank sequences for the species level determination of algae using the nrDNA ITS1-5.8S-ITS2 sequence, it could be confirmed that A. leptochaete is inhabiting Chaetomorpha (A. leptochaete - accession MK910762.1), Padina (A. leptochaete - accession MK910764.1) and Gracillaria (A. leptochaete - accession MK910760.1). This provides evidence for the broad host range owned by A. leptochaete among seaweed genera.
Germinability and Viability of Pollen of Selected Commercial Dendrobium Hybrids
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Kahagalla, T.H.; Herath, H.M.; Attanayake, R.N.; Senanayake, S.P.
Dendrobium is one of the highly demanding ornamental orchid genera in Sri Lankan floriculture industry. The assessment of functional quality of the pollinium on the basis of germinability and viability is useful for the development of breeding programs for crop quality improvement and pollen storage protocols in conservation. This research was carried out to determine in vivo and in vitro pollen germinability and pollen viability of eight commercial Dendrobium hybrids (A-H). Percentage of pollen viability was studied by placing crushed pollinia on a cavity slide with 1% 2,3,5-triphenyltetrazolium chloride solution and incubating at dark for 12 hours. Pollinia of Dendrobium flowers were placed on the stigma of the same flower on the second day after opening. After three days, pollinia were stained with lacto phenol cotton blue and percentage of in vivo pollen germination was calculated. In vitro pollen germination of the Dendrobium hybrids was studied in three different media. Pollinia were removed from the anthers on the second day after flower opening and placed in (i) 5%, 10%, 15%, 20% and 25% sucrose solutions and (ii) a semi solid medium containing 10% sucrose, 100 mgL-1 H3BO3, 300 mgL-1 Ca(NO3).2H2O, 200 mgL-1 MgSO4.7H2O, 200 mgL-1 KNO3, 8 gL-1 agar and stigmatic fluid of Dendrobium flower and incubated at room temperature. Pollinia of Dendrobium hybrids A, G and H placed in a (iii) semi solid medium containing 1%, 2%, 3% sucrose, 75 mgL-1 H3BO3 and 0.5%, 1%, 2% agar were incubated at 24 oC, 26 oC, and 28 oC. After 48 hours, percentage of in vitro pollen germination was calculated. Means were compared using one-way ANOVA with Tukey’s pairwise comparison test in IBM SPSS Statistics 22 software. As the percentage values of pollen germination and viability were not normally distributed, the values were transformed to arcsin square root values prior to statistical analysis. There was no significant deference in pollen viability of different hybrids which varied between 94% and 77%. The highest percentage of in vivo pollen germination was found in Dendrobium cultivar D (67%) and there was a significant deference in in vivo pollen germination among the hybrids. Correlation analysis was performed using IBM SPSS Statistics 22 software to determine the relationship between pollen viability and in vivo pollen germination and found that there was no significant relationship (�= 0.237). The percentage of in vitro pollen germination was low and the highest in vitro pollen germination (7.2%) was observed in the semisolid medium containing 1% sucrose, 75 mgL-1 H3BO3, 1% agar and incubated at 26 oC for Dendrobium cultivar H.