Identification and evaluation of intervarietal substitution lines of rapeseed (Brassica napus L.) with donor segments affecting the diploidization rate of isolated microspores

Abstract

AbstractIn Brassica species microspore derived doubled haploid lines are an important tool in breeding and research. A limiting step in the production of doubled haploid lines is the diploidization of the microspores. Strong differences have been observed in diploidization rates between different genotypes but little is know about the genetic control of these differences. To identify genomic regions that carry genetic factors controlling the diploidization rate of isolated microspores of rapeseed, marker segregations were compared between segregating populations of diploid and haploid microspore derived embryos and a BC1 from a cross between ‘Express 617’ and ‘RS239’. After map construction ten intervarietal substitution lines from the same cross were selected with donor segments covering five genomic regions that showed a pattern of skewed marker segregations across the three populations indicative of the segregation of genes controlling the diploidization rates. The diploidization rates of microspores of the ten lines ranged from 23.9 to 58.7 % while the recurrent parent ‘Express 617’ showed a rate of 52.5 %. For three lines the diploidization rates were significantly lower (P = 0.05) than the rate of ‘Express 617’. By comparing donor segments between the significant and the non-significant lines, seven genomic regions that cover just between 4.17 and 6.16 % of the rapeseed genome were identified that may contain genetic factors controlling diploidization rates in rapeseed. In addition, one marker was found that has a high probability to be linked to such a factor. The significant lines represent an ideal material for further in depth studies of this trait.