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P.I.P. Perera; R. Pathirana; V.R.M. Vidhanaarchchi. Somatic embryogenesis in anther-derived fast-growing callus as a long-term source for doubled-haploid production of coconut (Cocos nucifera L.). Journal of the National Science Foundation of Sri Lanka 2021, 49, 39 .
AMA StyleP.I.P. Perera, R. Pathirana, V.R.M. Vidhanaarchchi. Somatic embryogenesis in anther-derived fast-growing callus as a long-term source for doubled-haploid production of coconut (Cocos nucifera L.). Journal of the National Science Foundation of Sri Lanka. 2021; 49 (1):39.
Chicago/Turabian StyleP.I.P. Perera; R. Pathirana; V.R.M. Vidhanaarchchi. 2021. "Somatic embryogenesis in anther-derived fast-growing callus as a long-term source for doubled-haploid production of coconut (Cocos nucifera L.)." Journal of the National Science Foundation of Sri Lanka 49, no. 1: 39.
Cassava is one of the most important sources of energy. To meet the growing demand, genetic improvement is of utmost importance. Its cross-pollinating nature limits the opportunity of exploitation of hybrid vigor and demands the development of homozygous lines through doubled-haploid technologies. The problems in callus-mediated embryogenesis, such as longer processing time and genetically unstable nature, can be overcome by direct embryogenesis. Conditions to produce embryos directly from microspores in cultured anthers were optimized. The optimum stress pretreatment condition was 40 °C for 6 h after culturing the anthers into the induction medium. For proembryo formation, 2% sucrose and 5 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) or 1 mg/l 1-naphthaleneacetic acid were optimum. Globular embryos were formed by subculturing proembryos into the medium with 0.5 mg/l 2,4-D and 5 mg/l 6-benzylaminopurine after two weeks of culturing. Light microscopy of cultured anthers demonstrated the formation of multicellular structures and their further development into proembryos. Microscopic studies showed proembryos emerging through the damaged anther wall. Monoallelic banding in simple sequence repeat (SSR) analysis indicated homozygous or haploid states in some of the originated embryos. The conditions optimized in this study were effective in the early development of direct embryos after two weeks of culture initiation. This is the first report of the formation of direct embryos in cultured anthers of cassava.
Lakmali Dissanayake; Prasanthi Perera; Thilak Attanayaka; Erwin Heberle; Manosha Jayawardhana. Early Development of Direct Embryos in the Cultured Anthers of Manihot esculenta Crantz. Plants 2020, 9, 1315 .
AMA StyleLakmali Dissanayake, Prasanthi Perera, Thilak Attanayaka, Erwin Heberle, Manosha Jayawardhana. Early Development of Direct Embryos in the Cultured Anthers of Manihot esculenta Crantz. Plants. 2020; 9 (10):1315.
Chicago/Turabian StyleLakmali Dissanayake; Prasanthi Perera; Thilak Attanayaka; Erwin Heberle; Manosha Jayawardhana. 2020. "Early Development of Direct Embryos in the Cultured Anthers of Manihot esculenta Crantz." Plants 9, no. 10: 1315.
Doubled-haploids are a great source of material for heterozygous coconuts to shorten the time taken for crop improvement through hybridization programs. However, low frequency of embryo conversion and formation of weak plantlets are the major limitations in the protocol. In the present study anther-derived embryos were analysed at cellular level through the histological observations to understand the occurrence of shoot differentiation in those embryos. Attempts were also made to optimise the 6-Benzylaminopurine (BAP) concentration in the regeneration medium. Among the tested BAP levels (5, 15, 25, 35, 45, 55 μM), the regeneration medium containing 25 and 35 μM gave rise to 51.5% sprouted embryos against the control that gave only 22.7%. Among the analysed anther-derived embryos sequential events of differentiation including the formation of provascular strands followed by vascular bundle, differentiation in to the growing point, giving rise to the secondary embryos and polarization in to the shoot and root pole were identified. The blunt embryos devoid any morphological sign of sprouting showed different cellular arrangement viz. haustorial structure without any meristematic point (47%), bipolar with shoot and root meristems (8%) and unipolar with either of the pole (45%). Thick haustorial cover lead to the physical dormancy inhibiting further development of the polar structures. The germinating embryos containing a single shoot gave rise to the healthy plants where as double, multiple or fused shoots formed the week plantlets. The findings can be used for further optimisation of the protocol to achieve a greater plant regeneration frequency.
P. I. P. Perera; K. F. Motha; V. R. M. Vidhanaarchchi. Morphological and histological analysis of anther-derived embryos of coconut (Cocos nucifera L.). Plant Cell, Tissue and Organ Culture (PCTOC) 2020, 140, 685 -689.
AMA StyleP. I. P. Perera, K. F. Motha, V. R. M. Vidhanaarchchi. Morphological and histological analysis of anther-derived embryos of coconut (Cocos nucifera L.). Plant Cell, Tissue and Organ Culture (PCTOC). 2020; 140 (3):685-689.
Chicago/Turabian StyleP. I. P. Perera; K. F. Motha; V. R. M. Vidhanaarchchi. 2020. "Morphological and histological analysis of anther-derived embryos of coconut (Cocos nucifera L.)." Plant Cell, Tissue and Organ Culture (PCTOC) 140, no. 3: 685-689.
Gametes have the unique potential to enter the sporophytic pathway, called androgenesis. The plants produced are usually haploid and recombinant due to the preceding meiosis and they can double their chromosome number to form doubled haploids, which are completely homozygous. Availability of the doubled haploids facilitates mapping the genes of agronomically important traits, shortening the time of the breeding process required to produce new hybrids and homozygous varieties, and saving the time and cost for inbreeding. This study aimed to test the feasibility of using isolated and in vitro cultured immature cassava (Manihot esculenta) microspores to reprogramme and initiate sporophytic development. Different culture media and different concentrations of two ion components (Cu2+ and Fe2+) were tested in two genotypes of cassava. External structural changes, nuclear divisions and cellular changes during reprogramming were analysed by scanning electron microscopy, by staining with 4′,6-diamidino-2-phenylindole, and through classical histology and transmission electron microscopy. In two cassava genotypes, different developmental stages of microspores were found to initiate sporophytic cell divisions, that is, with tetrads of TMS 60444 and with mid or late uni-nucleate microspores of SM 1219-9. In the modified NLN medium (NLNS), microspore enlargements were observed. The medium supplemented with either sodium ferrous ethylene-diamine-tetraacetic acid (NaFeEDTA) or CuSO4·5H2O induced sporophytic cell division in both genotypes. A low frequency of the reprogramming and the presence of non-responsive microspores among the responsive ones in tetrads were found to be related to the viability and exine formation of the microspores. The present study clearly demonstrated that reprogramming occurs much faster in isolated microspore culture than in anther culture. This paves the way for the development of an efficient technique for the production of homozygous lines in cassava. This is the first ever detailed report of microspore reprogramming at the tetrad stage and the first report of microspore embryogenesis induction in cassava with detailed evidence.
P. I. P. Perera; C. A. Ordoñez; Beata Dedicova; Pablo Emilio Moreno Ortega. Reprogramming of cassava (Manihot esculenta) microspores towards sporophytic development. AoB PLANTS 2014, 6, 1 .
AMA StyleP. I. P. Perera, C. A. Ordoñez, Beata Dedicova, Pablo Emilio Moreno Ortega. Reprogramming of cassava (Manihot esculenta) microspores towards sporophytic development. AoB PLANTS. 2014; 6 ():1.
Chicago/Turabian StyleP. I. P. Perera; C. A. Ordoñez; Beata Dedicova; Pablo Emilio Moreno Ortega. 2014. "Reprogramming of cassava (Manihot esculenta) microspores towards sporophytic development." AoB PLANTS 6, no. : 1.
This study was aimed at inducing androgenesis in cultured anthers of cassava (Manihot esculenta Crantz) to develop a protocol for the production of doubled haploids. Microspore reprogramming was induced in cassava by cold or heat stress of anthers. Since the anthers contain both haploid microspores and diploid somatic cells, it was essential to verify the origin of anther-derived calli. The origin of anther-derived calli was assessed by morphological screening followed by histological analysis and flow cytometry (FCM). Additionally, simple sequence repeat (SSR) and amplified fragmented length polymorphism (AFLP) assays were used for the molecular identification of the microspore-derived calli. The study clearly demonstrated the feasibility of producing microspore-derived calli using heat- or cold-pretreated anthers. Histological studies revealed reprogramming of the developmental pathway of microspores by symmetrical division of the nucleus. Flow cytometry analysis revealed different ploidy level cell types including haploids, which confirmed their origin from the microspores. The SSR and AFLP marker assays independently confirmed the histological and FCM results of a haploid origin of the calli at the DNA level. The presence of multicellular microspores in the in vitro system indicated a switch of developmental program, which constitutes a crucial step in the design of protocols for the regeneration of microspore-derived embryos and plants. This is the first detailed report of calli, embryos, and abnormal shoots originated from the haploid cells in cassava, leading to the development of a protocol for the production of doubled haploid plants in cassava.
P. P.I. P. Perera; Carlos A Ordonez; Luis Augusto Becerra Lopez-Lavalle; Beata Dedicova. A milestone in the doubled haploid pathway of cassava. Protoplasma 2013, 251, 233 -246.
AMA StyleP. P.I. P. Perera, Carlos A Ordonez, Luis Augusto Becerra Lopez-Lavalle, Beata Dedicova. A milestone in the doubled haploid pathway of cassava. Protoplasma. 2013; 251 (1):233-246.
Chicago/Turabian StyleP. P.I. P. Perera; Carlos A Ordonez; Luis Augusto Becerra Lopez-Lavalle; Beata Dedicova. 2013. "A milestone in the doubled haploid pathway of cassava." Protoplasma 251, no. 1: 233-246.
Cassava (Manihot esculenta), a major food staple in the tropics and subtropics, thrives even in environments undergoing threatening climate change. To satisfy the increasing demand for crop improvement and overcome the limitations of conventional breeding, the introduction of inbreeding techniques such as the production of doubled haploid lines via androgenesis or gynogenesis offers advantages. However, comprehensive studies on cassava flower bud biology or structural development are lacking and precise structural and biological information is a prerequisite to enhance the efficiency of these techniques. The floral biology of three selected cassava lines was studied, focusing on morphology, phenology and pollen biology (quantity, viability and dimorphism). Histological studies were also conducted on microsporogenesis/microgametogenesis and megasporogenesis/megagameto-genesis to generate precise developmental data for these lines. Male and female cyathia have distinct developmental phases. Pollen viability was high during immature stages of plant development; however, pollen mortality was common at later stages. Pollen trimorphism in male gametophytes towards the larger or smaller pollen size, as compared with normal size, was observed. Ten characteristic events were identified in male gametogenesis and six in female gametogenesis that were correlated with flower bud diameter. Male gametophyte diameter at different developmental stages was also determined. Results indicate that the three lines did not differ significantly, except regarding a few morphological aspects such as plant height, flower colour and number of male cyathia. Pollen grains were initially viable, but viability decreased drastically at later stages of growth. Abnormal meiosis or mitosis triggered pollen trimorphism. The demonstrated sequential events of reproductive development generated valuable information at the cellular level, which will help close the current information gap for cassava improvement via breeding programmes and doubled haploid plant production.
P. I. P. Perera; M. Quintero; B. Dedicova; J. D. J. S. Kularatne; H. Ceballos. Comparative morphology, biology and histology of reproductive development in three lines of Manihot esculenta Crantz (Euphorbiaceae: Crotonoideae). AoB Plants 2012, 5, pls046 -pls046.
AMA StyleP. I. P. Perera, M. Quintero, B. Dedicova, J. D. J. S. Kularatne, H. Ceballos. Comparative morphology, biology and histology of reproductive development in three lines of Manihot esculenta Crantz (Euphorbiaceae: Crotonoideae). AoB Plants. 2012; 5 ():pls046-pls046.
Chicago/Turabian StyleP. I. P. Perera; M. Quintero; B. Dedicova; J. D. J. S. Kularatne; H. Ceballos. 2012. "Comparative morphology, biology and histology of reproductive development in three lines of Manihot esculenta Crantz (Euphorbiaceae: Crotonoideae)." AoB Plants 5, no. : pls046-pls046.
Palms are generally characterized by a large structure with a massive crown that creates difficulties in anatomical studies. The flowering behaviour of palm species may be a useful indicator of phylogenetic relationships and therefore evolutionary events. This paper presents a detailed histological study of reproductive development in coconut (Cocos nucifera L.), from initiation up to maturation of staminate and pistillate flowers. Reproductive development in coconut consists of a sequence of individual events that span more than two years. Floral morphogenesis is the longest event, taking about one year, while sex determination is a rapid process that occurs within one month. The inflorescence consists of different ultimate floral structural components. Pistillate flowers are borne in floral triads that are flanked by two functional staminate flowers. The staminate flowers are born in floral diads towards the base of the rachilla followed by solitary flowers in the middle to top of the rachilla. Three primary phases were identified in reproductive development, namely, transition of axillary bud into inflorescence bud, formation of floral buds, and sexualisation of individual flower buds. All developmental events with respect to stage or time of occurrence were determined
Indra Prasanthi Perera; V. Hocher; L.K. Weerakoon; D.M.D. Yakandawala; S.C. Fernando; J.-L. Verdeil. Early inflorescence and floral development in Cocos nucifera L. (Arecaceae: Arecoideae). South African Journal of Botany 2010, 76, 482 -492.
AMA StyleIndra Prasanthi Perera, V. Hocher, L.K. Weerakoon, D.M.D. Yakandawala, S.C. Fernando, J.-L. Verdeil. Early inflorescence and floral development in Cocos nucifera L. (Arecaceae: Arecoideae). South African Journal of Botany. 2010; 76 (3):482-492.
Chicago/Turabian StyleIndra Prasanthi Perera; V. Hocher; L.K. Weerakoon; D.M.D. Yakandawala; S.C. Fernando; J.-L. Verdeil. 2010. "Early inflorescence and floral development in Cocos nucifera L. (Arecaceae: Arecoideae)." South African Journal of Botany 76, no. 3: 482-492.
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 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.1% activated charcoal. Callusing was improved by application of 9 μM thidiazuron (TDZ). Embryogenic calli were subcultured onto somatic embryogenesis induction medium containing 66 μM 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 μM 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.
P. I. P. Perera; V. R. M. Vidhanaarachchi; T. R. Gunathilake; D. M. D. Yakandawala; V. Hocher; J. L. Verdeil; L. K. Weerakoon. Effect of plant growth regulators on ovary culture of coconut (Cocos nucifera L.). Plant Cell, Tissue and Organ Culture (PCTOC) 2009, 99, 73 -81.
AMA StyleP. I. P. Perera, V. R. M. Vidhanaarachchi, T. R. Gunathilake, D. M. D. Yakandawala, V. Hocher, J. L. Verdeil, L. K. Weerakoon. Effect of plant growth regulators on ovary culture of coconut (Cocos nucifera L.). Plant Cell, Tissue and Organ Culture (PCTOC). 2009; 99 (1):73-81.
Chicago/Turabian StyleP. I. P. Perera; V. R. M. Vidhanaarachchi; T. R. Gunathilake; D. M. D. Yakandawala; V. Hocher; J. L. Verdeil; L. K. Weerakoon. 2009. "Effect of plant growth regulators on ovary culture of coconut (Cocos nucifera L.)." Plant Cell, Tissue and Organ Culture (PCTOC) 99, no. 1: 73-81.
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 μM NAA in combination with 100 μM 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 μM 2,4-D alone. Kinetin and 2-iP enhanced the production of calli/embryos when 100 μM 2,4-D was present in the culture medium. Both cytokinins at 10 μM yielded the highest frequencies of embryos (113 and 93, respectively) whereas zeatin (1 or 2.5 μM) had no impact on microspore embryogenesis. When calli/embryos (produced from different treatments in different experiments) were sub-cultured in somatic embryo induction medium (Y3 medium containing 66 μM 2,4-D), followed by maturation medium (Y3 medium without growth regulators) and germination medium (Y3 medium containing 5 μM-6-benzyladenine—BA and 0.35 μM gibberellic acid—GA3), plantlets were regenerated at low frequencies (in most treatments ranging from 0% to 7%).
P. I. P. Perera; D. M. D. Yakandawala; V. Hocher; J-L. Verdeil; L. K. Weerakoon. Effect of growth regulators on microspore embryogenesis in coconut anthers. Plant Cell, Tissue and Organ Culture 2008, 96, 171 -180.
AMA StyleP. I. P. Perera, D. M. D. Yakandawala, V. Hocher, J-L. Verdeil, L. K. Weerakoon. Effect of growth regulators on microspore embryogenesis in coconut anthers. Plant Cell, Tissue and Organ Culture. 2008; 96 (2):171-180.
Chicago/Turabian StyleP. I. P. Perera; D. M. D. Yakandawala; V. Hocher; J-L. Verdeil; L. K. Weerakoon. 2008. "Effect of growth regulators on microspore embryogenesis in coconut anthers." Plant Cell, Tissue and Organ Culture 96, no. 2: 171-180.
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.
P. I. P. Perera; L. Perera; V. Hocher; J. -L. Verdeil; D. M. D. Yakandawala; L. K. Weerakoon. Use of SSR markers to determine the anther-derived homozygous lines in coconut. Plant Cell Reports 2008, 27, 1697 -1703.
AMA StyleP. I. P. Perera, L. Perera, V. Hocher, J. -L. Verdeil, D. M. D. Yakandawala, L. K. Weerakoon. Use of SSR markers to determine the anther-derived homozygous lines in coconut. Plant Cell Reports. 2008; 27 (11):1697-1703.
Chicago/Turabian StyleP. I. P. Perera; L. Perera; V. Hocher; J. -L. Verdeil; D. M. D. Yakandawala; L. K. Weerakoon. 2008. "Use of SSR markers to determine the anther-derived homozygous lines in coconut." Plant Cell Reports 27, no. 11: 1697-1703.
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 μM 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 μM 2,4-d, followed by transfer to Y3 medium without plant growth regulators and finally to Y3 medium containing 5 μM 6-benzyladenine (BA) and 0.35 μM 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.
P. I. P. Perera; V. Hocher; J.-L. Verdeil; H. D. D. Bandupriya; D. M. D. Yakandawala; L. K. Weerakoon. Androgenic potential in coconut (Cocos nucifera L.). Plant Cell, Tissue and Organ Culture (PCTOC) 2008, 92, 293 -302.
AMA StyleP. I. P. Perera, V. Hocher, J.-L. Verdeil, H. D. D. Bandupriya, D. M. D. Yakandawala, L. K. Weerakoon. Androgenic potential in coconut (Cocos nucifera L.). Plant Cell, Tissue and Organ Culture (PCTOC). 2008; 92 (3):293-302.
Chicago/Turabian StyleP. I. P. Perera; V. Hocher; J.-L. Verdeil; H. D. D. Bandupriya; D. M. D. Yakandawala; L. K. Weerakoon. 2008. "Androgenic potential in coconut (Cocos nucifera L.)." Plant Cell, Tissue and Organ Culture (PCTOC) 92, no. 3: 293-302.
P. I. P. Perera; V. Hocher; J. L. Verdeil; D. M. D. Yakandawala; L. K. Weerakoon. Recent Advances in Anther Culture of Coconut(Cocos nucifera L.). Biotechnology and Sustainable Agriculture 2006 and Beyond 2007, 451 -455.
AMA StyleP. I. P. Perera, V. Hocher, J. L. Verdeil, D. M. D. Yakandawala, L. K. Weerakoon. Recent Advances in Anther Culture of Coconut(Cocos nucifera L.). Biotechnology and Sustainable Agriculture 2006 and Beyond. 2007; ():451-455.
Chicago/Turabian StyleP. I. P. Perera; V. Hocher; J. L. Verdeil; D. M. D. Yakandawala; L. K. Weerakoon. 2007. "Recent Advances in Anther Culture of Coconut(Cocos nucifera L.)." Biotechnology and Sustainable Agriculture 2006 and Beyond , no. : 451-455.
Unfertilized ovaries isolated from immature female flowers of coconut (Cocos nucifera L.) were tested as a source of explants for callogenesis and somatic embryogenesis. The correct developmental stage of ovary explants and suitable in vitro culture conditions for consistent callus production were identified. The concentration of 2,4-dichlorophenoxyacetic acid (2,4-D) and activated charcoal was found to be critical for callogenesis. When cultured in a medium containing 100 microM 2,4-D and 0.1% activated charcoal, ovary explants gave rise to 41% callusing. Embryogenic calli were sub-cultured into somatic embryogenesis induction medium containing 5 microM abscisic acid, followed by plant regeneration medium (with 5 microM 6-benzylaminopurine). Many of the somatic embryos formed were complete with shoot and root poles and upon germination they gave rise to normal shoots. However, some abnormal developments were also observed. Flow cytometric analysis revealed that all the calli tested were diploid. Through histological studies, it was possible to study the sequence of the events that take place during somatic embryogenesis including orientation, polarization and elongation of the embryos.
Prasanthi I. P. Perera; Valérie Hocher; Jean Luc Verdeil; Sylvie Doulbeau; Deepthi M. D. Yakandawala; L. Kaushalya Weerakoon. Unfertilized ovary: a novel explant for coconut (Cocos nucifera L.) somatic embryogenesis. Plant Cell Reports 2006, 26, 21 -28.
AMA StylePrasanthi I. P. Perera, Valérie Hocher, Jean Luc Verdeil, Sylvie Doulbeau, Deepthi M. D. Yakandawala, L. Kaushalya Weerakoon. Unfertilized ovary: a novel explant for coconut (Cocos nucifera L.) somatic embryogenesis. Plant Cell Reports. 2006; 26 (1):21-28.
Chicago/Turabian StylePrasanthi I. P. Perera; Valérie Hocher; Jean Luc Verdeil; Sylvie Doulbeau; Deepthi M. D. Yakandawala; L. Kaushalya Weerakoon. 2006. "Unfertilized ovary: a novel explant for coconut (Cocos nucifera L.) somatic embryogenesis." Plant Cell Reports 26, no. 1: 21-28.