Genetics of microspore embryogenesis and doubled haploid development in rapeseed (Brassica napus L.)

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Today microspore embryogenesis and the doubled haploid lines developed by this process are of great importance in practical breeding but especially in basic re-search. On the other hand, not much is currently known about the molecular pro-cesses that occur in microspores during the induction of embryogenesis or about the genes that govern the embryogenic potential, that is the tendency of the microspores to form embryos. The embryogenic potential of the microspores is the main factor limiting microspore embryogenesis and varies widely between genotypes. In a DFG project a number of intervarietal substitution lines (ISLs) have been identified, which show an up to 40x higher embryogenic potential than the recurrent parent. ISL are produced by marker assisted selection in a recurring backcrossing of a donor and recurrent parent and carry only one or a few segments of the donor genome in the genetic background of the recurrent parent. ISLs are, therefore, genetically different from the recurrent parent only in a few well defined genomic regions. In the proposed project 4 selected ISLs shall be analysed in more detail. This includes a comparative analysis of transcriptional profiles during the induction of embryogenesis using MACE analyses and the identification of candidate genes that may be responsible for the enhanced embryogenic potential of the lines. The transcription profiles of the candi-date genes will then be verified by qRT-PCR analysis. In addition, from further back-crosses of the 4 lines, new ISLs shall be developed, which will carry only single (overlapping sub-) segments of the donor segments of the original lines. The new ISL will allow a fine mapping of the genetic factors responsible for the enhanced embryo-genic potential observed in the original lines. Finally, the transcripts from the MACE analyses and the donor segments of the new ISL will be mapped on the genomic sequences of the A and C genomes of rapeseed to allow an integration of the results from the genetic and transcriptional studies.