Comparison between diploid and tetraploid citrus rootstocks: morphological characterization and growth evaluation. Tetraploid citrus rootstocks may present different morphological characteristics and growth when compared to diploid ones. This worked aimed at comparing morphological characteristics and height growth of diploid and tetraploid plants from the rootstocks 'Swingle' citrumelo [ C. Raf], citrange 'Troyer' C.

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Aleza Gil Pablo. Obtencion de hidricos triploides de citricos. Valence : Universidad Politecnica de Valencia, p. 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. 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. We have shown by SSR Simple Sequence Repeats markers that all tetraploid genotypes were obtained by duplication of chromosomes number in nucellar cells.

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.

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. 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. Se connecter.


Obtencion de hidricos triploides de citricos

Citrus is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits , including important crops such as oranges , lemons , grapefruits , pomelos , and limes. Various citrus species have been utilized and domesticated by indigenous cultures in these areas since ancient times. From there its cultivation spread into Micronesia and Polynesia by the Austronesian expansion c. Citrus plants are native to subtropical and tropical regions of Asia, Island Southeast Asia , Near Oceania , and northeastern Australia. Domestication of citrus species involved much hybridization and introgression , leaving much uncertainty about when and where domestication first happened.


Citrus taxonomy

Polyploidy is a major component of plant evolution. The citrus gene pool is essentially diploid but tetraploid plants are frequently encountered in seedlings of diploid apomictic genotypes. The main objectives of the present study were to establish the origin of these tetraploid plants and to ascertain the importance of genotypic and environmental factors on tetraploid formation. Tetraploid seedlings from 30 diploid apomictic genotypes were selected by flow cytometry and genotyped with 24 single sequence repeat SSR markers to analyse their genetic origin. Inter-annual variations in tetraploid seedling rates were analysed for seven genotypes. Tetraploid plants were obtained for all the studied diploid genotypes, except for four mandarins.

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