Abstract
AbstractMicrospore culture has become an important tool in many species, includingBrassicas, 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 BC1population, 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.
Highlights
Microspores or immature pollen grains of many plant species can be diverted from the normal gametophytic to a sporophytic developmental pathway by a stress treatment, for example a mild heat stress
In a number of experiments studying Direct Embryo to Plant Conversion (DEPC) rates under different culture conditions and pretreatments using a range of genotypes, Klutschewski (2013) found a strong, in many experiments a predominant, effect of the genotype on DEPC rates. These results clearly indicate that the DEPC rate of microspore derived embryos’’ (MDEs) of rapeseed is under genetic control
For analysing skewed marker segregations, a population of 214 double haploid (DH) plantlets were developed (DEPC population) that were derived from MDEs that had directly converted to plants after transfer to solid medium
Summary
Microspores or immature pollen grains of many plant species can be diverted from the normal gametophytic to a sporophytic developmental pathway by a stress treatment, for example a mild heat stress. When cultured in a nutrient-rich medium, they start to divide repeatedly and develop into embryo like structures, so called ‘‘microspore derived embryos’’ (MDEs), which can be grown into fully developed plants after transfer to solid medium (Touraev et al 2001; Forster et al 2007; Ferrie and Caswell 2011). This phenomenon is known as microspore embryogenesis or androgenesis. The main advantage of androgenesis is, that traits can be fixed in one generation rather than after multiple selfpollinated generations (Dunwell 2010; Ferrie and Caswell 2011; Germana 2011)
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