Obtencion de hidricos triploides de citricos

Aleza Gil Pablo. 2008. Obtencion de hidricos triploides de citricos. Valence : Universidad Politecnica de Valencia, 224 p. Tesis Doctor Ingeniero Agronomico : Universidad Politecnica de Valencia : Universidad Politecnica de Valencia

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Encadrement : Ollitrault, Patrick ; Navarro Lucas, Luis

Abstract : The presence of seeds in the fruits of mandarin is an undesirable feature for the fresh fruit market. Citrus triploid hybrids have a great interest because they do not produce seeds and don't induce the formation of seeds in other genotypes by cross-pollination. Triploids hybrids can be obtained through somatic hybridization between haploid and diploid protoplasts and through sexual hybridization between diploid parents and diploids and tetraploids parents. The overall objectives of this thesis are to obtain parents for the production of citrus triploid hybrids, to characterize different sexual hybridizations that produce triploid hybrids and to understand citrus reproductive biology in connection with triploid hybrids recovering. These broad objectives are realized in the following specific objectives: 1. Obtaining haploid plants using in situ gynogenesis induced by irradiated pollen and subsequent in vitro rescue and embryo culture. We obtained haploid, double haploid and aneuploid genotypes of clementina 'Clemenules'. One of the haploid genotypes has been selected by the International Genomics Citrus Consortium for the whole citrus genome sequencing. 2. Obtaining tetraploids plants of different apomictic genotypes of mandarin, sweet orange and grapefruit that can be used as a male parent in 2x X 4x hybridizations. Spontaneous tetraploids of 15 genotypes, of the 17 analysed, have been identified by flow cytometry with frequencies ranged from 9.7% in 'Kinnow' mandarin to 0.5% in 'Page' mandarin. We have shown by SSR (Simple Sequence Repeats) markers that all tetraploid genotypes were obtained by duplication of chromosomes number in nucellar cells. 3. Obtaining tetraploid plants of non apomictic genotypes of mandarins that can be used as male and female parents in 2x X 4x and 4x X 2x hybridizations. They have been obtaining after colchicine and orizaline treatment of shoot tips micrografted in vitro. Tetraploid plants have been obtained directly from the micrografted shoot tips and from the segregation of citoquimeras. Stable tetraploid plants of clementines 'Clemenules', 'Fina', 'Marisol' and 'Moncada' mandarin have been obtained. 4. Obtaining triploid hybrids through 2x X 2x, 4x X 2x and 4x X 2x hybridizations. Triploid embryos have been selected in different kind of seeds depending on the type of hybridization. We evaluated the efficiencies of the different strategies depending on parental genotypes. The 2x X 4x and 4x X 2x hybridizations showed the highest efficiency in production of triploid hybrids. However, for the genotypes producing very high frequency of 2n gametes, such as 'Fortune' mandarin, the 2x X 2x strategy has been very efficient. We also demonstrate the great influence of the male parent in the production of triploid hybrids. Finally, we discuss the implications of different types of hybridization at the level of segregation and theoretical genotypic diversity of the triploid populations. 5. Identification of the genetic origin of plants recovered from undeveloped polyembryonic seeds originated in the 2x X 4x hybridization using no apomictic genotypes as female parent. We demonstrate with SSR markers that the origin of the polyembryony occurs as a result of a secondary embryogenesis from the original zygotic embryo. Likewise, this feature is confirmed by the regeneration of plants from nucellus cultured in vitro of the non apomictic citrus genotypes. We conclude that the formation of adventitious embryos from the original zygotic embryo is a frequent occurrence in non apomictic citrus genotypes and that the development of these embryos is generally inhibited by the main embryo. We discuss the implication in the genetic improvement programme of this reproductive biology mechanism described here for the first time. 6. Establishing a molecular profile with SSR markers of 15 new triploid hybrids of mandarin presented by the Instituto Valenciano de Investigaciones Agrarias for protection at the Oficina Española d

Mots-clés Agrovoc : Hybride, Citrus, Triploïdie

Mots-clés géographiques Agrovoc : Espagne

Classification Agris : F30 - Plant genetics and breeding
F63 - Plant physiology - Reproduction

Axe stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

Auteurs et affiliations

  • Aleza Gil Pablo, IVIA (ESP)

Autres liens de la publication

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