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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Genetic variation in somatic embryogenesis of Rosa Hybrida L.

Burrell, Anna Mildred 30 September 2004 (has links)
An in vitro technique was adapted for screening the ability of Rosa hybrida L. genotypes to form embryogenic callus to elucidate the inheritance of this ability. Filament and leaf petiole explants of modern rose cultivars 'Tournament of Roses' and 'Baby Love' were cultured on somatic embryogenesis induction media and evaluated for the ability to produce embryogenic callus. Cultures of 'Tournament of Roses' produced somatic embryos at a much higher frequency versus 'Baby Love' that produced no embryos. Subsequently, filament explants of eleven 'Tournament of Roses' x 'Baby Love' progeny genotypes were cultured on somatic embryogenesis induction media and evaluated for the ability to undergo somatic embryogenesis. The progeny genotypes produced somatic embryos at varied frequencies. The results obtained indicated that the ability to undergo embryogenesis in Rosa hybrida L. is heritable in an additive fashion with the involvement of more than one gene.
42

Identification and characterization of spruce genes involved in somatic embryo development

Law, Derek Albert 12 July 2006 (has links)
Somatic embryogenesis can provide researchers with an important tool to study the physiological and molecular mechanisms involved in embryo development. In spruce, few lines are able to produce fully developed embryos due to the presence of malformed meristems. Genes from two families known as KNOX (knotted-like homeobox) and ARGONAUTE (AGO) have previously been found to be involved in meristem development and maintenance. This work documents the discovery of a new member of the AGO family of proteins designated as PgAGO and the further study of a KNOX gene known as HBK2. The complete coding sequence of both PgAGO and HBK2 was obtained through screening of cDNA libraries generated from white spruce (Picea glauca) somatic embryos. RNA in-situ hybridization studies showed that PgAGO mRNAs accumulate preferentially within cells of the shoot and root apical meristems in developing spruce embryos. In addition, the expression of PgAGO was low in white spruce lines unable to produce embryos in culture. Norway spruce (Picea abies) embryogenic tissue was transformed via microprojectile bombardment with an antisense construct of PgAGO. Down-regulation of PgAGO altered proper development of the apical meristems and reduced embryo regeneration. RNA in-situ hybridization studies showed that HBK2 is specifically expressed in the sub-apical and cortical regions of developing embryos. Like PgAGO, HBK2 expression was diminished in white spruce lines unable to produce embryos in culture. Transformation experiments with antisense constructs of HBK2 completely arrested somatic embryo development. This study reveals the importance of a functional meristem during embryo development. / October 2006
43

Genetic variation in somatic embryogenesis of Rosa Hybrida L.

Burrell, Anna Mildred 30 September 2004 (has links)
An in vitro technique was adapted for screening the ability of Rosa hybrida L. genotypes to form embryogenic callus to elucidate the inheritance of this ability. Filament and leaf petiole explants of modern rose cultivars 'Tournament of Roses' and 'Baby Love' were cultured on somatic embryogenesis induction media and evaluated for the ability to produce embryogenic callus. Cultures of 'Tournament of Roses' produced somatic embryos at a much higher frequency versus 'Baby Love' that produced no embryos. Subsequently, filament explants of eleven 'Tournament of Roses' x 'Baby Love' progeny genotypes were cultured on somatic embryogenesis induction media and evaluated for the ability to undergo somatic embryogenesis. The progeny genotypes produced somatic embryos at varied frequencies. The results obtained indicated that the ability to undergo embryogenesis in Rosa hybrida L. is heritable in an additive fashion with the involvement of more than one gene.
44

Characterisation of morphogenesis mutants in Arabidopsis

Horne, Kirsty L. January 1998 (has links)
In this thesis is described the identification and characterisation of two morphogenesis mutants of Arabidopsis thaliana. One, vertically challenged (vch1) exhibits much reduced cellular elongation. The second, altered suspensor fate (asf1) is embryonic- lethal. A thorough phenotypic analysis of both mutants is presented, as are the results of genetic analysis. Vch1 exhibits a severe reduction in cellular elongation throughout the plant, resulting in a dwarfed phenotype. Despite its stunted morphology, vch1 exhibits normal cellular patterning, demonstrating that cell morphogenesis can be uncoupled from correct cellular pattern formation, vch1 follows a normal life history by all parameters examined demonstrating that the timing of developmental events can be uncoupled from correct morphogenesis. The phenotype of vch1 cannot be rescued by the exogenous supply of a range of hormones, signalling inhibitors or growth conditions, although it can respond to each, in a proportionately similar manner to wild type seedlings. No defects in cell wall architecture nor in cytoskeletal organisation were detected during this study. Speculative models for the role of the VCH gene are proposed. In asf1, the embryo proper arrests at the transition stage of embryogenesis. The wild type suspensor is a single file of cells which serves to anchor the embryo proper to the maternal tissue and acts as a conduit for, and source of, nutrients to the developing embryo. In asf1, suspensor cells undergo inappropriate proliferation following the arrest of the embryo proper. Evidence is presented from cytological and ultrastructural examination, and expression of spatially restricted gus-fusion marker genes, that the ectopically divided suspensor cells take on aspects of embryo proper-like character. Models for the role of the ASF1 gene are proposed. It is likely that the mutant phenotype results from disruption of intercellular communication between the embryo proper and suspensor.
45

Identification and characterization of spruce genes involved in somatic embryo development

Law, Derek Albert 12 July 2006 (has links)
Somatic embryogenesis can provide researchers with an important tool to study the physiological and molecular mechanisms involved in embryo development. In spruce, few lines are able to produce fully developed embryos due to the presence of malformed meristems. Genes from two families known as KNOX (knotted-like homeobox) and ARGONAUTE (AGO) have previously been found to be involved in meristem development and maintenance. This work documents the discovery of a new member of the AGO family of proteins designated as PgAGO and the further study of a KNOX gene known as HBK2. The complete coding sequence of both PgAGO and HBK2 was obtained through screening of cDNA libraries generated from white spruce (Picea glauca) somatic embryos. RNA in-situ hybridization studies showed that PgAGO mRNAs accumulate preferentially within cells of the shoot and root apical meristems in developing spruce embryos. In addition, the expression of PgAGO was low in white spruce lines unable to produce embryos in culture. Norway spruce (Picea abies) embryogenic tissue was transformed via microprojectile bombardment with an antisense construct of PgAGO. Down-regulation of PgAGO altered proper development of the apical meristems and reduced embryo regeneration. RNA in-situ hybridization studies showed that HBK2 is specifically expressed in the sub-apical and cortical regions of developing embryos. Like PgAGO, HBK2 expression was diminished in white spruce lines unable to produce embryos in culture. Transformation experiments with antisense constructs of HBK2 completely arrested somatic embryo development. This study reveals the importance of a functional meristem during embryo development.
46

Studies in organ culture and the development of organogenic potential in Alnus, Sorbus and Prunus

Lall, Sonia January 2000 (has links)
Micropropagation was investigated in order to develop protocols for rapid mass production of shoots ofSorbus aucuparia and Alnus glutinosa. Removal of apical dominance either physically by pruning the plantlets or chemically by using anti-auxins TIB A (2,3,5-triiodobenzoic acid) and NPA (1-naphthylphthalamic acid) was investigated. There was a 6-fold increase in the number of rooting-ready shoots of S. aucuparia produced by the pruning of plantlets grown in vitro. A. glutinosa however, needed more drastic measures to remove apical dominance and block the endogenous auxin transport. Incorporation of TIBA (3 μm) in the medium produced an initial 8- fold increase in the number of shoots. However, repeated subculture of shoots of Alnus on TIBA containing medium proved detrimental to shoot multiplication. There was 100% rooting of shoots of S. aucuparia on agar solidified medium. The auxin: cytokinin ratio of the multiplication medium played an important role in the rooting ability of shoots. A. glutinosa also had 100% rooting on agar solidified medium. Plants were acclimatised in Baumgartner vessels before transferring to soil. There was 100% rooting and survival of the shoots of A. glutinosa both after transfer to Baumgartner vessels and subsequent transfer to soil. In S. aucuparia the survival rates in Baumgartner vessels was 70% and after transfer to soil was 65%. Direct somatic embryogenesis from zygotic tissue of both S. aucuparia and A. glutinosa was achieved. Embryos of S. aucuparia were produced on medium containing MS salts and vitamins supplemented with 1 μM BAP, 1 μM kinetin, 0.5 μM NAA, 250 mg/L L-glutamine and 500 mg/L casein hydrolysate. A. glutinosa embryos were obtained on medium containing salts and vitamins of Driver and Kuniyuki (1984) supplemented with 3 μM BAP. No auxin was required. Adventitous shoot regeneration from leaves of S.aucuparia was also achieved at a frequency of 40% on medium containing MS salts and vitamins supplemented with 10 μM TDZ and 1 μM NAA. A method for chromosome doubling of S. aucuparia using 15 uM pronamide to treat shoot tips immersed in a semi-solid medium was developed. After 14 days of treatment, 86.5% treated shoots survived and there was 44.5% chromosome doubling of the survivors. The tetraploid shoot had a higher rate of multiplication than the diploid shoots. The involvement of extracellular proteins in direct somatic embryogenesis of Prunus 'Colt' was studied. Changes in the expression of proteins were observed from the first day of transferring the tissue to embryo induction medium. Most changes were seen on the days 28 and 35 when the embryos became visible.
47

Identification and characterization of spruce genes involved in somatic embryo development

Law, Derek Albert 12 July 2006 (has links)
Somatic embryogenesis can provide researchers with an important tool to study the physiological and molecular mechanisms involved in embryo development. In spruce, few lines are able to produce fully developed embryos due to the presence of malformed meristems. Genes from two families known as KNOX (knotted-like homeobox) and ARGONAUTE (AGO) have previously been found to be involved in meristem development and maintenance. This work documents the discovery of a new member of the AGO family of proteins designated as PgAGO and the further study of a KNOX gene known as HBK2. The complete coding sequence of both PgAGO and HBK2 was obtained through screening of cDNA libraries generated from white spruce (Picea glauca) somatic embryos. RNA in-situ hybridization studies showed that PgAGO mRNAs accumulate preferentially within cells of the shoot and root apical meristems in developing spruce embryos. In addition, the expression of PgAGO was low in white spruce lines unable to produce embryos in culture. Norway spruce (Picea abies) embryogenic tissue was transformed via microprojectile bombardment with an antisense construct of PgAGO. Down-regulation of PgAGO altered proper development of the apical meristems and reduced embryo regeneration. RNA in-situ hybridization studies showed that HBK2 is specifically expressed in the sub-apical and cortical regions of developing embryos. Like PgAGO, HBK2 expression was diminished in white spruce lines unable to produce embryos in culture. Transformation experiments with antisense constructs of HBK2 completely arrested somatic embryo development. This study reveals the importance of a functional meristem during embryo development.
48

Indução in vitro de haplóides e de poliplóides e detecção molecular de alelos da auto- incompatibilidade em maracujazeiro (Passiflora edulis f. flavicarpa Deg.) / Induction in vitro of haploid s and poliploids and molecular detection of self - incompatibility alleles in passion -fruit (Passiflora edulis f. flavicarpa Deg.)

Rêgo, Mailson Monteiro do 12 August 2001 (has links)
Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-05-09T17:14:16Z No. of bitstreams: 1 texto completo.pdf: 865049 bytes, checksum: e1f0232ee5da962b69abe15831e4525c (MD5) / Made available in DSpace on 2017-05-09T17:14:16Z (GMT). No. of bitstreams: 1 texto completo.pdf: 865049 bytes, checksum: e1f0232ee5da962b69abe15831e4525c (MD5) Previous issue date: 2001-08-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Os objetivos deste trabalho foram avaliar a resposta ginogênica em 11 genótipos, adequar metodologia para indução in vitro de poliplóides e detectar alelos da auto - incompatibilidade em maracujazeiro azedo ( Passiflora edulis f. flavicarpa Degener). Para avaliar os 11 genótipos, óvulos não -fertilizados foram inoculados em meio MS suplementado com as vitaminas do meio B5, 100 mg.L -1 de mio-inositol, 3% de sacarose, 5,0 mg.L -1 de 2,4 – D e 1,0 mg.L -1 de BAP e cultivado na ausência d e luz a 27°C ± 1. Na indução dos poliplóides, utilizou -se explantes de segmentos de hipocótilo (1,0 cm de comprimento) de plantas germinadas in vitro e o meio MS suplementado com agentes antimitóticos, colchicina (0, 25, 250 e 1250 μM) e orizalina (0, 5, 15 e 30 μM). A determinação do nível ploidia das plantas regeneradas e aclimatadas foi feita por meio da contagem do número de cromossomos em células metafásicas de ponta de raiz. Na detecção molecular dos alelos S da auto -incompatibilidade, reações de PCR foram conduzidas utilizando DNA genômico extraído de folhas jovens e oligonucleotídeos iniciadores específicos para os alelos-S das classes I e II. O genótipo II – 20 apresentou melhor resposta ginogênica, produzindo 21 embriões (7,0 7% dos óvulos inoculados). Na indução dos poliplóides, os meios mais adequados foram MS suplementado com colchicina a 25 μM e MS suplementado orizalina a 15 μM. A colchicina, em concentrações superiores (250 e 1250 μM) foi fitotóxica aos explantes. Os indivíduos diplóides apresentaram 2n = 2x = 18 cromossomas, enquanto os tetraplóides, 2n = 4x = 36. O número de cloroplastos por célula guarda foi eficiente indicador do nível de ploidia nesta espécie. Plantas diplóides possuem quatro cloroplastos por célula-guarda e as tetraplóides oito, em média. Utilizando- se os iniciadores específicos para os alelos -S, foi possível detectar e incluir a nível molecular, os alelos S 1 e S 3 do maracujazeiro, no subgrupo I das glicoproteínas do loco -S (SLG) das brassicas. / The objectives of this work were to evaluate the gynogenic ability of 11 genotypes, to adapt in vitro methodology for poliploidy induction and detection of self -incompatibility alleles in yellow passion fruit (Passiflora edulis f. flavicarpa Degener). For the evaluation of gynogenic ability, no-fertilized ovules were inoculated in a MS medium supplemented with vitamin B5, 100 mg.L -1 mio-inositol, 3 g.L -1 sucrose, 5,0 mg.L -1 2,4 - D and 1,0 mg.L -1 BAP and cultivated in dark at 27°C ± 1. For poliploidy induction, explants from hypoc otyl segments (1,0 cm length) of plants germinated in vitro were inoculated in BAD medium, supplemented with antimitotic agents: colchicine (0, 25, 250 and 1250 μM) and orizaline (0, 5, 15 and 30μM). The ploidy level of regenerated and acclimatized plants was determinated by counting the number of chromosomes at root tips metaphasic cells. For the molecular detection of self-incompatibility S-alleles, genomic DNA was extracted from young leaves and submitted to PCR reaction with specific oligonucleotides primers for the classes I and II of the S-alleles. The genotype II - 20 presented the better gynogenic ability, producing 21 embryos (7,07% of the inoculated ovules). For the induction of poliploidy, the most appropriate media were BAD supplemented with 25 μM colchicine and BAD supplemented with 15 μM orizaline. Higher concentrations of colchicine (250 and 1250 μM) were toxic to the explants. The diploid individuals presented 2n = 2x = 18 chromosomes, while the tetraploids had 2n = 4x = 36. The number of chlor oplasts in the guard-cells was an efficient indicator of the ploidy level in this species. The guard -cells had four chloroplasts in diploid plants and eight in tetraploid ones. The alleles S1 and S3 were detected at molecular level and included in the subgroup I of glicoproteins of S-locus (SLG) of the Brassica. / Tese importada do Alexandria
49

Somatic embryogenesis and cryopreservation of cauliflower (Brassica oleracea var. botrytis)

Al Shamari, Magda January 2014 (has links)
Successful efficient whole cauliflower plant regeneration via somatic embryogenesis from root derived callus tissue was achieved. The research confirmed for the first time the capability of mass production of cauliflower somatic embryos through the indirect pathway. The best callus induction and proliferation was on semi solid Murashige and Skoog (MS) medium supplemented with 2, 4-D at 0.15 mg L-1 and Kinetin at 0.1 mg L-1 and 3% sucrose. The response of different explant types (cotyledon, hypocotyls and root) through callus induction and subsequent culture was determined. The best period for subsequent callus culture was 21 days. Continuous immersion in agitated liquid medium technique was subsequently used for primary somatic embryo production. The culture requirements were empirically optimized including: explants source and size of callus tissue, blending duration, plant growth regulator combinations and concentrations as well as carbohydrate type and concentration. The highest mean number of somatic embryos (30.9) per explant was achieved using root derived embryogenic callus tissue on MS medium provided with IAA 0.05 mgL-1 and Kinetin at 0.5 mgL-1 and 2% sucrose. Somatic embryos were developed and matured on this medium and germinated with the highest percentage (60%) on semi-solid MS medium devoid of growth regulators. The culture conditions that led to the formation of secondary somatic embryos were identified. The presence of activated charcoal in the culture medium had an effect on this process but some abnormality of secondary somatic embryos was observed. Artificial seeds were produced by encapsulating the somatic embryos with a sodium alginate gel (2%) and complexing with calcium chloride (100 mM) for 20 min. The ability of these artificial seed for germination was evaluated using various combinations of plant growth regulators that were either incorporated in the artificial matrix or in the germination semi-solid culture medium. It was confirmed that cauliflower root derived embryogenic callus tissue can be cryopreserved following a preculture-dehydration technique. Following cryopreservation, embryogenic cultures can proliferate in agitated liquid medium, and somatic embryos at the globular stage were formed. Also cold storage at 5 °C in the dark was used successfully to store cauliflower callus tissue for three months without diminution of the competence for somatic embryos formation. This ability for cold storage could have a positive effect in reducing costs and efforts that result from subsequent sub-culture. The encapsulation-dehydration technique was assessed for cryopreservation of somatic embryos but failed to lead to survival of any embryos. Somatic embryos that were produced in this study were able to be well acclimated using a reliable weaning procedure that achieved high rates of survival of plantlets and their subsequent growth to normal plants in the field was assessed. Morphological characteristics of somatic plants compared favourably with zygotic plants but although there was phenotypic similarity, some differences in plant height, curd size and time for curd maturity were observed.
50

In vitro selection and whole-plant studies of salt and drought tolerance in Elettaria cardamomum

Sindhu, K. January 1996 (has links)
No description available.

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