Wheat (genome AABBDD) is one of the essential crops, offering approximate 20% of human calorie consumption worldwide. Allopolyploidization of three diploid ancestors led to hexaploid wheat with narrowed genetic variation. Chromosome engineering is an applicable approach to restore the evolutionarily-omitted genetic diversity by homoeologous chromosomes recombination between wheat and its relatives. Two diploid relatives of wheat, Thinopyrum elongatum (genome EE) and Aegilops speltoides (genome SS), containing favorable genes, are used as gene resources for alien introgression and genome diversification in wheat. An advanced and effective experiment procedure was developed and applied for the production, recovery, detection, and characterization of homoeologous recombinants. Meanwhile, a novel recombinant chromosome recovery strategy was exploited with improved efficiency and accuracy. In this study, recombinants of wheat chromosomes 3B and 7B with their homoeologous chromosomes in Th. elongatum and Ae. speltoides (i.e. 3B-3E, 7B-7E, and 7B-7S) were produced and detected. Totolly, 81 3B-3E recombinants and four aberrations involving in distinct chromosomal regions were developed in three recombination cycles by fluorescent genomic in situ hybridization (FGISH). The secondary and tertiary recombination breakpoints occurred toward the proximal regions comparing to the primary recombination under this advanced recombination procedure. A novel recovery strategy was used to recover 7B-7E and 7B-7S homoeologous recombinants by chromosome-specific markers and FGISH verification. Marker-based pre-screening and subsequent FGISH verification identified 29 7B-7E and 61 7B- 7S recombinants, seven 7B-7E and four 7B-7S Robertsonian translocations, one 7E and five 7S telocentric chromosomes, and three 7S deletions. All the recombinants and aberrations were genotyped by high-throughput wheat 90K single nucleotide polymorphism (SNP) assay and the recombination breakpoints were physically mapped to wheat chromosome 3B or 7B according to their FGISH patterns, SNP results, and wheat reference genome sequence. Chromosome 3B was physically partitioned into 38 bins with 429 SNPs. Meanwhile, 44 distinct bins were resolved for chromosome 7B with 523 SNPs. A composite bin map was constructed for chromosomes 3B and 7B, respectively, with a comprehensive analysis of FGISH and SNPs results. In summary, this project provides a unique physical framework for further wheat genome studies and diversifies the wheat genome for germplasm development in wheat breeding.

Hybridization is an important phenomenon in plant evolution because it is one of the sources of new genetic variability. Hybridization is the merging of genomes of formerly isolated evolutionary lineages. In many taxonomic groups, the detection of plants of hybrid origin is challenging. A wide spectrum of methods for their detection has been employed since the beginning of botanical research. The introduction of genomic in situ hybridization has had a great impact on the study plants of hybrid origin. This molecular cytogenetic approach allows to reveal the genomic contributions of particular parental species to hybrid taxa. The tribe Triticeae is a prime example of a group whose present-day diversity has been strongly influenced by hybridization (together with polyploidy). The majority of its species are allopolyploids resulting from frequent interspecific and intergeneric hybridization. The structure of relationships within the tribe is therefore highly reticulate. This thesis includes three papers dealing with the hybrid complex of Elytrigia repens - E. ×mucronata - E. intermedia: (1) The representatives of this hybrid complex are morphologically poorly differentiated, and only two morphological characters are used to their distinguishing. Among anatomical characters on the leaf blade, some...

Summary : The wild diploïd species Gossypium australe carry interesting agronomic characters such as resistance to wilt fusarium and "delay of the gossypol glands morphogenesis in the seed " that makes it an important source of variability for the genetic improvement of the main cultivated cotton species G. hirsutum. One of the approach to introgress these characters is to isolate and exploit monosomic alien addition lines (MAAL). In order to isolate new MAAL of G. australe in G. hirsutum, the [2(G.hirsutum x G.australe)x G.hirsutum] pentaploid was backcrossed as male parent to G. hirsutum. Among the 253 BC1 derivatives obtained, 106 plants (42%) presented morphological alterations attributed to presence of G. australe chromatin. To define an SSR linkage group for each of the 13 G. australe chromosomes, 42 plants representative of the phenotypic variability observed in the BC1 generation and seven alien addition lines already isolated in our laboratory were analyzed using SSR markers developed from the G. hirsutum species. Out of the 150 SSR markers used, 100 % amplified G. australe DNA and 84 (56 %) generated 89 polymorphic loci. All these loci but two have been assigned, by means of an cluster algorithm, to 13 linkage groups assumed to match up to the 13 chromosomes of the diploid species. On this basis, about 60% of the analyzed plants were multisomic addition lines, 20%, MAAL while 20 % carrying no markers were supposed to be euploid. The newly isolated MAAL appeared to be the same as those already available. Five disomic alien addition plants carrying at least one additional chromosome different from the chromosomes of G. australe previously isolated in a monosomic addition configuration were selfed and the BC1S1 progenies obtained have been analyzed with SSR markers and GISH. Five new MAAL of G. australe in G. hirsutum have thus been isolated. In order to monitor the potentialities of using MAAL for the transfer of genetic material from the additional chromosome to the genetic background, the transmission frequency and integrity of the supernumerary chromosome have been analyzed with SSR markers in the self-progeny of five MAAL. Three of them revealed a transmission frequency significantly lower than the 3:1 expected ratio, one MAAL presented an exclusive preferential transmission of the additional chromosome. In these four MAAL the alien chromosome was transmitted almost unaltered. With the fifth MAAL the alien chromosome was normally transmitted but was altered in half of the plants containing G. australe chromatin. One of the investigated MAAL characterized by its brown fiber produced few plants carrying also white fibers. It has been shown that this mosaicism was due to the loss of the alien supernumerary chromosome. The complete loss of this chromosome seems to be linked to its fragmentation. Résumé : L'espèce diploïde sauvage Gossypium australe possède des caractères agronomiques d'intérêt tels que la résistance au fusarium et le "retard à la morphogenèse des glandes à gossypol" qui en font une importante source de variabilité pour l'amélioration génétique de la principale espèce de cotonnier cultivé G. hirsutum. Une des approches pour l'introgression de ces caractères est la production et l'exploitation de lignées monosomiques d'addition (LMA). Pour isoler les LMA de G. australe sur G. hirsutum, le pentaploïde [2(G.hirsutum x G.australe)x G.hirsutum] a été rétrocroisé comme parent mâle avec l'espèce tétraploïde. Sur les 253 graines obtenues, 106 (42%) ont donné des plantes présentant une morphologie nettement distincte de celle de G. hirsutum. Cette différence a été attribuée à la présence de chromosomes de G. australe. Afin de définir des groupes de liaison pour chacun des chromosomes de G. australe, 42 plantes représentatives de la variabilité phénotypique observée ainsi que 7 lignées d'addition déjà isolées ont été sélectionnées et analysées avec des marqueurs SSR développés sur l'espèce tétraploïde. Tous les 150 marqueurs utilisés ont amplifié l'ADN de G. australe et 84 (56%) ont généré 89 loci polymorphes. Tous ces loci, sauf deux, ont pu être assignés, par classification numérique, à 13 groupes de liaison supposés correspondre aux 13 chromosomes de l'espèce diploïde. Sur cette base, 60% des plantes analysées sont des plurisomiques d'addition; 20%, des LMA tandis que 20 % ne portant aucun marqueur ont été supposées euploïdes. Les nouvelles LMA isolées s'étant révélées être identiques à celles déjà isolées, 5 plantes disomiques d'addition portant au moins un chromosome non-encore isolé à l'état monosomique d'addition ont été autofécondées et leur descendance analysée avec des marqueurs SSR et par la GISH. Cinq nouvelles LMA ont pu ainsi être isolées. Afin d'étudier les potentialités d'utilisation de la méthode des LMA pour le transfert de matériel génétique de l'espèce sauvage vers l'espèce cultivée, la fréquence de transmission et l'intégrité du chromosome surnuméraire, a été analysée avec des marqueurs SSR dans une génération autofécondée de cinq LMA. Trois lignées ont donné un taux de transmission inférieur au ratio attendu de 3:1, chez la quatrième lignée le chromosome surnuméraire a été transmis à toute la descendance. Pour ces quatre lignées le chromosome additionnel a été transmis presque inaltéré. Avec la cinquième lignée, le chromosome additionnel a été transmis suivant le taux attendu mais a été altéré dans la moitié des plantes contenant de la chromatine de G. australe. Une des lignées analysées caractérisée par la couleur brune de ses fibres a produit quelques plantes portant également des fibres blanches. Il a été montré que ce mosaïcisme de la couleur des fibres était dû à la perte du chromosome additionnel. Cette perte semble être liée à une fragmentation du chromosome.