Untersuchungen und physikalische Kartierung von Genen im hexaploiden Weizen, verantwortlich für die Embryoentwicklung in Weizen-Roggen-Hybriden durch Interaktion mit dem Roggengenom
Zusammenfassung der Projektergebnisse
In intergeneric crosses between hexaploid wheat (Triticum aestivum L.) and rye (Secale cereale L.), postzygotic barriers may occur at different stages of hybrid development. In our recent study we investigated the mechanisms of embryo lethality and hybrid sterility, which are genetically determined by the interaction and expression of two incompatible alleles in wheat (Eml-A1) and rye (Eml-R1) and identified and mapped a novel DEFECTIVE ENDOSPERM–D1 (Dee-D1) locus on the long arm of chromosome 1D which is involved in the genetic control of endosperm development. The results obtained in our experiments allow us to conclude that the Eml-A1 and Eml-R1 alleles play an active role and function both during embryogenesis and into gametogenesis of wheat and rye. The combination of incompatible alleles in one genome leads at the first stage to the emergence of hybrid lethality, and if it is overcome through embryo culture, obtaining fertile plants in such an incompatible crossing is possible only with the targeted elimination of one of the incompatible alleles either in mitosis or in meiosis. Elimination of 6AL or 6A chromosomes was often accompanied by the loss of one of the arms of chromosomes 5 (5A, 5B) or 7 (7A, 7B, 7D) of the homeologous groups. Elimination of a long arm or the entire 6R chromosome with incompatible Eml-R1b allele did not affect big changes in the structure of the wheat genome and elimination of all chromosomes of the rye genome is possible. High fertility (> 50%) in main spike of primary triticale AD31L2 and AD6AL8L2 confirms that hybrid sterility in amphidiploids from crossing bread wheat CS with the inbred rye line L2 is caused by a negative interaction between of incompatible alleles Eml-A1 and Eml-R1b. We discovered and mapped a novel DEFECTIVE ENDOSPERM–D1 (Dee-D1) locus that is physically located on the long arm of chromosome 1D and has never been studied before. Dee-D1 plays a crucial role in endosperm formation in hexaploid wheat. The absence of Dee-D1 leads to produce shriveled grains and the formation of nonviable grains in crosses with rye. The absence of Dee-D1 in the genome of hexaploid wheat leads to a loss of GN and TGW. The loss of fertility and the change in the morphology of the spike can be caused either by other loci located in the target area or the pleiotropic effects of Dee-D1 are involved in the regulation of spike morphology and spike fertility in hexaploid wheat. Dee-D1 and Dee-B1 can be classified as speciation loci with a positive effect on the function of genes which are involved in endosperm development in the hybrid genome. The presence of such loci is necessary for the normal development of endosperm in tetraploid and hexaploid wheat. Dee-D1 has a greater force of action than Dee-B1 in the genome of hexaploid wheat and normalizes the development of hybrid endosperm in distant hybrids. On the base of the project results the patent application "Wheat 44 Approach" on the basis of CS1Dt1DSAL line proposing the alternative new breeding program for winter and spring bread wheat was submitted in March 2020. Our unpublished results will be used as the base for new research projects.
