Browsing by Author "Yakandawala, D.M.D."

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    Androgenic potential in coconut (Cocos nucifera L.)
    (2008) Verdeil, J.L.; Hocher, V.; Perera, P.I.P.; Yakandawala, D.M.D.; Bandupriya, H.D.D.; Weerakoon, L.K.
    Conditions for induction of androgenesis in coconut cv. Sri Lanka Tall were studied. Anthers collected from inflorescences at four maturity stages were given heat (38 C) or cold (4 C) pretreatments for 1, 3, 6 and 14 days, either prior to or post inoculation. Three different basal media and different anther densities were also tested. Androgenesis was observed only in anthers collected from inflorescences 3 weeks before splitting (WBS) and after a heat pretreatment at 38 C for 6 days. Modified Eeuwens Y3 liquid medium supplemented with 100 lM 2,4-dichlorophenoxyacetic acid (2,4-D), 0.1% activated charcoal and 9% sucrose was effective in inducing an androgenic response. The lowest anther density tested, 10 per petri plate, was found to be the optimal density. When androgenic calli or embryos were subcultured to Y3 medium containing 66 lM 2,4-D, followed by transfer to Y3 medium without plant growth regulators and finally to Y3 medium containing 5 lM 6-benzyladenine (BA) and 0.35 lM gibberellic acid (GA3), plantlets regenerated at a frequency of 7%. Histological study indicated that the calli and embryos originated from the inner tissues of the anthers. Ploidy analysis of calli and embryos showed that they were haploid. This is the first report of successful androgenesis yielding haploid plants from coconut anthers
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    Androgenic potential in coconut (Cocos nucifera L.)
    (2008) Perera, P.I.P.; Hocher, V.; Verdeil, J.L.; Yakandawala, D.M.D.; Bandupriya, H.D.D.; Weerakoon, L.K.
    Conditions for induction of androgenesis in coconut cv. Sri Lanka Tall were studied. Anthers collected from inflorescences at four maturity stages were given heat (38 C) or cold (4 C) pretreatments for 1, 3, 6 and 14 days, either prior to or post inoculation. Three different basal media and different anther densities were also tested. Androgenesis was observed only in anthers collected from inflorescences 3 weeks before splitting (WBS) and after a heat pretreatment at 38 C for 6 days. Modified Eeuwens Y3 liquid medium supplemented with 100 lM 2,4-dichlorophenoxyacetic acid (2,4-D), 0.1% activated charcoal and 9% sucrose was effective in inducing an androgenic response. The lowest anther density tested, 10 per petri plate, was found to be the optimal density. When androgenic calli or embryos were subcultured to Y3 medium containing 66 lM 2,4-D, followed by transfer to Y3 medium without plant growth regulators and finally to Y3 medium containing 5 lM 6-benzyladenine (BA) and 0.35 lM gibberellic acid (GA3), plantlets regenerated at a frequency of 7%. Histological study indicated that the calli and embryos originated from the inner tissues of the anthers. Ploidy analysis of calli and embryos showed that they were haploid. This is the first report of successful androgenesis yielding haploid plants from coconut anthers.
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    Effect of growth regulators on microspore embryogenesis in coconut anthers
    (2009) Perera, P.I.P.; Yakandawala, D.M.D.; Hocher, V.; Verdeil, J.L.; Weerakoon, L.K.
    The effect of growth regulators on induction of androgenesis in coconut was investigated using seven different growth regulators at various concentrations and combinations. Three auxins (1-naphthalene acetic acid— NAA, indoleacetic acid—IAA, picloram) and three cytokinins (2-isopentyl adenine-2-iP, kinetin, zeatin) were tested either alone or in combination with 2,4-dichlorophenoxyacetic acid (2,4-D), using modified Eeuwens Y3 liquid medium as the basal medium. Among the tested auxins, 100 lM NAA in combination with 100 lM 2,4-D enhanced the production of calli/embryos (123) whereas IAA and picloram showed negative and detrimental effects, respectively, for androgenesis induction over 100 lM 2,4- D alone. Kinetin and 2-iP enhanced the production of calli/ embryos when 100 lM 2,4-D was present in the culture medium. Both cytokinins at 10 lM yielded the highest frequencies of embryos (113 and 93, respectively) whereas zeatin (1 or 2.5 lM) had no impact on microspore embryogenesis. When calli/embryos (produced from different treatments in different experiments) were subcultured in somatic embryo induction medium (Y3 medium containing 66 lM 2,4-D), followed by maturation medium (Y3 medium without growth regulators) and germination medium (Y3 medium containing 5 lM-6-benzyladenine— BA and 0.35 lM gibberellic acid—GA3), plantlets were regenerated at low frequencies (in most treatments ranging from 0% to 7%).
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    Effect of plant growth regulators on ovary culture of coconut (Cocos nucifera L.)
    (2009) Perera, P.I.P.; Vidhanaarachchi, V.R.M.; Gunathilake, T.R.; Yakandawala, D.M.D.; Hocher, V.; Verdeil, J.L.; Weerakoon, L.K.
    Coconut is a cross pollinating palm, propagated only by seeds. Tissue culture is the only vegetative propagation method available for coconut. Consistent callogenesis was obtained by culturing unfertilised ovaries at -4 stage in CRI 72 medium containing 100 lM 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.1% activated charcoal. Callusing was improved by application of 9 lM thidiazuron (TDZ). Embryogenic calli were subcultured onto somatic embryogenesis induction medium containing 66 lM 2,4-D. Stunted growth was observed in the somatic embryos after subculture onto CRI 72 medium containing abscisic acid (ABA). Maturation of somatic embryos could be achieved in Y3 medium without growth regulators. Conversion of somatic embryos was induced by adding gibberellic acid (GA3) to conversion medium containing 5 lM 6-benzyladenine (BA) while 2-isopentyl adenine (2iP) increased the frequency of plant regeneration. A total of 83 plantlets was produced from 32 cultured ovaries.
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    Feasibility of Using the Expression of the Retinoblastoma Gene as a Marker for Assessing the Embryogenic Potential of Coconut Ovary Culture
    (2009) Perera, P.I.P.; Hocher, V.; Weerakoon, L.K.; Yakandawala, D.M.D.; Verdeil, J.L.
    Coconut is a monocotyledonous tree crop that is highly recalcitrant to in vitro culture conditions. Ovary culture is a promising technique for clonal propagation of coconut. A greater understanding of the fundamental aspects of somatic embryogenesis and plant regeneration is very important in achieving a break-through. Identification of tissues having a high embryogenic potential at an early stage is also very important to achieve a high regeneration efficiency and to avoid maintenance of non-responsive cultures for a prolonged period. In situ hybridization was employed to study the expression of CnRb gene in selected tissues, to identify a potential molecular marker to assess the embryogenic potential of coconut ovary cultures. The results revealed that in situ hybridization can be used to detect the expression of CnRb gene in the cells. It was possible to establish a relationship between the meristematic activity and expression of CnRb gene in the tissues tested. CnRb mRNAs were mainly localized in the meristematic cells and tissues such as calli and growing point of the developing shoots.
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    Use of SSR Markers to Determine the anther-derived Homozygous Lines in Coconut
    (Springer-Verlag, 2008-01) Perera, P.I.P.; Perera, L.; Hocher, V.; Verdeil, J.L.; Yakandawala, D.M.D.; Weerakoon, L.K.
    Anther culture was used to obtain dihaploid (DH) coconut plants and their ploidy level was determined by flow cytometric analysis. Simple sequence repeat (SSR) marker analysis was conducted to identify the homozygous diploid individuals. Ploidy analysis showed that 50% of the tested plantlets were haploid and 50% were diploid. Polymorphic fragments of the mother palm and their segregation patterns in anther-derived plantlets were used to determine the origin of the diploid plantlets. Using a diagnostic SSR marker (CNZ43), all the diploid plantlets tested were identified as being derived from microspores (i.e. were homozygous) and were thus candidates for use in coconut breeding programs.
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    Use of SSR markers to determine the anther-derived homozygous lines in coconut
    (2008) Perera, P.I.P.; Verdeil, J.L.; Hocher, V.; Perera, L.; Yakandawala, D.M.D.; Weerakoon, L.K.
    Anther culture was used to obtain dihaploid (DH) coconut plants and their ploidy level was determined by flow cytometric analysis. Simple sequence repeat (SSR) marker analysis was conducted to identify the homozygous diploid individuals. Ploidy analysis showed that 50% of the tested plantlets were haploid and 50% were diploid. Polymorphic fragments of the mother palm and their segregation patterns in anther-derived plantlets were used to determine the origin of the diploid plantlets. Using a diagnostic SSR marker (CNZ43), all the diploid plantlets tested were identified as being derived from microspores (i.e. were homozygous) and were thus candidates for use in coconut breeding programs