Characterization of genomic regions responsible for the outstanding microspore embryo-genic potential of the doubled haploid oilseed rape line DH4079 (Brassica napus L.)

• Applicant: Dr. Christian Möllers
• Subject Area: Plant Breeding and Plant Pathology
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259274065

During the past decades, the culture of immature pollen grains, called microspores has gained much importance in breeding of oilseed rape for the rapid and efficient generation of completely homozygous doubled haploid lines. Despite the progress achieved in optimizing tissue culture protocols, tremendous differences remain among Brassica napus genotypes in their embryogenic response of cultured microspores. The genetic basis of the genotypic differences in microspore culture response is largely unknown and the non-embryogenic response of microspores of the cruciferous ancestor species Arabidopsis thaliana remains a mystery. Hence, Brassica napus serves as a model species to explore the genetic basis of microspore embryogenesis. The spring oilseed rape cultivar Topas is known since years for its excellent microspore embryogenic potential. From this cultivar, the doubled haploid line DH4079 with an even further improved microspore embryogenic potential has been developed. DH4079 is currently used as standard genotype in many investigations related to microspore embryogenesis, including those investigating gene expression profiles in induced embryogenic and non-induced microspores. A number of candidate genes for microspore embryogenesis and for direct embryo to shoot conversion have been identified. The genome sequence of Brassica rapa, one of the ancestor species of Brassica napus has been published and the publication of the complete genome sequence of Brassica oleracea and Brassica napus is anticipated within short time. With those genome sequences the physical positions of the candidate genes can be identified on the chromosomes. Obviously, there is a lack of phenotypic data for microspore embryogenesis of DH populations to identify overlapping positions of QTL and candidate gene loci as well as to identify new loci which to date have not been considered. For QTL mapping the parents of the DH population should be as different as possible for the trait(s) of interest. Regarding the embryogenic capacity, DH4079 is probably one of the best Brassica napus lines known, giving thousands of embryos per experiment. In previous work to this project, this line has been crossed to inbred line 617 of winter oilseed rape cultivar Express. This cultivar has been shown in long term experiments under varying conditions to give a low embryo yield in the range of few up to 50 embryos per experiment, under comparable conditions. One clonally propagated F1-plant of this cross has been used to develop a DH population of 207 lines. The main aims of the present project is to develop a molecular linkage map of this population using SNP markers (Illumina Infinium Brassica 60k Chip), to map QTL for microspore embryogenesis and direct embryo to shoot conversion and to compare positions of QTL with those of candidate genes using the available Brassica genome sequences.

• DFG Programme: Research Grants
• Participating Person: Privatdozent Dr. Wolfgang Ecke