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Hybridization and polyploidization as significant evolutional aspects in the tribe Triticeae
Urfusová, Romana ; Mahelka, Václav (advisor) ; Escudero, Marcial (referee) ; Štech, Milan (referee)
Hybridization and polyploidization, two vastly important evolutionary mechanisms, have been well studied experimentally within the Triticeae, but the specific consequences of both phenomena under natural conditions remain poorly defined. This is due to the variability of natural populations, whether in species composition, genetic and cytogenetic diversity, abiotic conditions, or their interaction. Each population is thus unique in its own way, with specific parameters of hybridization, polyploidization or reproductive mode. The latter mechanism is both influenced by and influences the former. For example, it is known that self-incompatibility can be broken by the presence of foreign pollen (a phenomenon known as the mentor effect). To study these processes, I chose Central European species of the genus Elymus: E. hispidus, E. repens, and marginally also E. caninus. All three species are allopolyploid. Whereas E. hispidus and E. repens are predominantly allohexaploid, E. caninus is allotetraploid. The former two have been found to hybridize and produce higher polyploid cytotypes. The role of E. caninus has not yet been studied. Methodologically, I have used flow cytometry (analysis of absolute and relative genome size), morphometrics, experimental hybridization, cytology (chromosome counting) and...
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Natural hybridization between two allopolyploid wheatgrasses Elytrigia intermedia and E.repens (Poaceae, Triticeae)
Mahelka, Václav ; Krahulec, František (advisor) ; Bureš, Petr (referee) ; Blattner, Frank (referee)
Aims of the Thesis The thesis is part of an ongoing project focused on hybridization in the wheat (Triticum aestivum)Elytrigia intermedia-E. repens species complex. This complex represents a real model of cropweed (wild relative) system with potential gene flow. The aim ofthe project is to detectand possibly to evaluate the frequencyof geneflow from wheat into its wild relative,E. intermedia.Such study could provide a crucial background for potential risk assessmentof the release of genetically modified wheat into the environment. Wheat is often crossedwith E intermedia in order to transfer some desirabletraits of the wild grass into the wheat genome. Such hybridization is routinely performed under laboratory conditions; however, it has not yet been observed under natural conditions. Since E intermedia crosseswith E repens, it may serve as a bridge species for gene flow from wheat into the weedy E. repens. Knowledge of the frequency of hybridization between both Elytrigia congeners with its consequencesis thus of high interestand is the main objective of the thesis.The aims of the thesis can be summarizedas follows: (1) to eva|uatecýological variability of Elytrigia repens and E. intermedia n natural populations in the Czech Republic; (2) to establish reliable diagnostic markers for species and hybrid...
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Natural hybridization between two allopolyploid wheatgrasses Elytrigia intermedia and E.repens (Poaceae, Triticeae)
Mahelka, Václav ; Krahulec, František (advisor) ; Bureš, Petr (referee) ; Blattner, Frank (referee)
Aims of the Thesis The thesis is part of an ongoing project focused on hybridization in the wheat (Triticum aestivum)Elytrigia intermedia-E. repens species complex. This complex represents a real model of cropweed (wild relative) system with potential gene flow. The aim ofthe project is to detectand possibly to evaluate the frequencyof geneflow from wheat into its wild relative,E. intermedia.Such study could provide a crucial background for potential risk assessmentof the release of genetically modified wheat into the environment. Wheat is often crossedwith E intermedia in order to transfer some desirabletraits of the wild grass into the wheat genome. Such hybridization is routinely performed under laboratory conditions; however, it has not yet been observed under natural conditions. Since E intermedia crosseswith E repens, it may serve as a bridge species for gene flow from wheat into the weedy E. repens. Knowledge of the frequency of hybridization between both Elytrigia congeners with its consequencesis thus of high interestand is the main objective of the thesis.The aims of the thesis can be summarizedas follows: (1) to eva|uatecýological variability of Elytrigia repens and E. intermedia n natural populations in the Czech Republic; (2) to establish reliable diagnostic markers for species and hybrid...
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