Identification and evaluation of intervarietal substitution lines of rapeseed (Brassica napus L.) with donor segments affecting the direct embryo to plant conversion rate of microspore-derived embryos

Abstract

AbstractMicrospore culture has become an important tool in many species, including Brassicas, for the production of entirely homozygous lines, so called double haploid (DH) lines. The primary products of microspore culture are embryo-like structures, called microspore-derived embryos (MDEs). A major problem in the development of DH lines is the often low efficiency of Direct Embryo to Plant Conversion (DEPC). During the development of DH populations, favourable alleles of genes affecting the DEPC rate will be under selection. This selection should lead to skewed segregations at markers linked to these genes. By comparing skewed marker segregations in four populations, a population of doubled haploid plantlets, a haploid and a doubled haploid MDE population, and a BC1 population, 20 genomic regions were identified, which showed patterns of skewed segregations across the populations, indicative of the segregation of genetic factors controlling DEPC rates. Four regions and eight intervarietal substitution lines (ISLs) with donor segments overlapping these regions were selected for further studies. Three ISLs, ER654, ER661 and ER653 with DEPC rates of 49.1, 54.5 and 57.2 %, showed significantly reduced DEPC rates compared to the rate of the recurrent parent of 76.5 %. By comparing donor segments between the significant and the non-significant lines, eight genomic regions were identified that may contain genetic factors controlling the DEPC rate in rapeseed. These regions range in size from 0 (represented by just one marker) to 16.5 cM and cover together just 1.33 % of the genetic map used to characterize the donor segments in the ISLs.