Browsing by Author "Attanayaka, D.P.S.T.G."

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    Determination of Genetic Purity of the Yellow Dwarf Coconut Seedlings Rejected from Nurseries Using SSR Markers
    (Uva Wellassa University of Sri Lanka, 2018) Wijewickrama, W.L.H.; Meegahakumbura, M.K.; Attanayaka, D.P.S.T.G.; Alwis, L.M.H.R.
    Hybrids coconut cultivars usually produce 40% higher yields over commonly grown Sri Lankan Talls. At present about 10,000 yellow dwarf coconut seedlings are rejected yearly from nurseries, as there is not true to type hybrids based on yellow color petiole as a visible marker for hybrid seedlings. The ambiguity of this phenotypic marker for selection often results in considerable wastage of true hybrid seedlings from the nurseries widening the gap between the demand and the supply of hybrid planting material. In the current study, microsatellite (SSR) marker-based approach was used to test the true hybridity of seedlings raised in the nursery. One hundred rejected seedlings were screened with 2 SSR primers, namely CAC 68 and CAC 23 which exhibited potential to distinguish parental varieties, Sri Lanka Tall (SLT), Sri Lanka Yellow Dwarf (SLYD), and resulting hybrids. The results of the study revealed that on average 36% of the rejected plants were true hybrids which are suitable for planting. The percentages of parental types, the true contaminants were 62% comprising with 6% Tall types and 56% SLYD types. As a result the current visible marker used to select off type seedlings from the coconut nursery is inaccurate resulting a loss of 36 true hybrids to the industry for every 100 seedlings rejected. The two SSR markers can be used to confirm the hybridity of seedlings derived from SLT X SLYD crosses reducing the loss by authenticated plants from the nurseries.
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    Genome Analysis on Drought Resistance of Hevea brasiliensis
    (Uva Wellassa University of Sri Lanka, 2018) Rajapaksha, R.L.P.N.D.; Weerasinghe, A.R.; Attanayaka, D.P.S.T.G.; Wijesinghe, C.R.; Alwis, L.M.H.R.
    Hevea brasiliensis (para rubber tree) plays an important role in the economy of Sri Lanka. Potential drought stress conditions due to climatic changes will have a severe effect on the yield and the survival of the rubber tree. Understanding the underlying genetic basis of drought tolerance through identification and systematic analyses of the candidate genes associated with drought tolerance of Hevea will help rubber breeding by marker assisted selection and transgenic improvement. This study was undertaken to generate information about the genes related to drought tolerance in Hevea. Biologically validated eighteen Arabidopsis thaliana genes with known functional pathways were used as query sequences to find orthologous Hevea genes from the ASM165405v1 genome assembly using the BLASTP program of the BLAST tool. Query coverage higher than 50%, bit score higher than 80 and E-value lower than 1 x10-5° were taken as cut off criteria for the search. Nine Hevea orthologous genes were identified and they represented six functional groups involved with both physiological and molecular adaptation to drought. Highest number of candidate genes identified encodes transcription factors. Systematic analyses of the identified genes related to drought tolerance suggest that transcription regulation, phospholipid metabolism, growth control, detoxification signaling, osmolyte biosynthesis and signal transduction pathways play important roles in drought tolerance in Hevea. Identification and analysis of conserved regions was conducted for the identified three transcription factors using the MEME and InterPro tools respectively. Three domains were identified which shared Gene Ontology terms related to drought tolerance. The results of the research not only enrich information about the genes related to drought tolerance, but also provide new insights into understanding the drought tolerance mechanisms in rubber tree.