A new recombined double low restorer line for the Ogu-INRA cms in rapeseed (Brassica napus L.)

Abstract

A major objective of breeders using the Ogu-INRA cytoplasmic male sterility (cms) system in rapeseed (Brassica napus L.) is to obtain double low restorer lines with a shorter introgression and a good agronomic value. The development of low glucosinolate content (low GC) restorer lines often occurs through the deletion of a part of the introgression. One of these lines has lost the radish Pgi-2 allele expression, without recovering that of the rapeseed Pgi-2 allele. This line shows a defect in the meiotic transmission of the restorer gene Rfo and a very poor agronomic value. We initiated a programme to force non-spontaneous recombination between this Rfo-carrying introgression and the rapeseed homologous chromosome from a low GC B. napus line. Gamma ray irradiation was used to induce chromosome breakage just prior meiosis aiming at just such a recombination. Low GC cms plants were crossed with the pollen of irradiated plants that were heterozygous for this introgression. The F(2) families were scored for their vigour, transmission rate of Rfo and female fertility. One family of plants, R2000, showed an improved behaviour for these three traits. This family presented a unique combination of molecular markers when compared to other rapeseed restorers analysed, which suggests that the recombination event allowed the recovery of B. oleracea genetic information that was originally replaced by the radish introgression in the original restorers. This resulted in a duplicated region (originating from radish and B. oleracea) on the chromosome carrying the introgression in the R2000 family.

Size and location of radish chromosome regions carrying the fertility restorer Rfk1 gene in spring turnip rape

“…However, Mason et al (2010) found that more complex interactions between genomic structure and alleles are involved controlling homeologous pairing in Brassicas. The irradiation technology has also exploited successfully when developed R2000 B. napus Ogu-INRA restorer line (Primard-Brisset et al 2005). The Rfo gene was integrated into C genome of B. napus by forcing recombination between radish and rapeseed using ionizing irradiation.…”

Non-destructive in vitro selection of microspore-derived embryos with the fertility restorer gene for CMS Ogu-INRA in winter oilseed rape (Brassica napus L.)

“…Although suitable molecular markers for the Rfo gene in Brassica napus have been developed [5,7,8], their utilisation in DH Rf line production requires cultivation of DH regenerants up to a stage when there is a sufficiently large leaf area for DNA isolation and subsequent analyses. A method that would enable the non-destructive identification of genotypes carrying the Rfo gene at early stages of microspore derived embryos would be of great benefit in terms of significantly reducing the amount of cultivated DH regenerants, and thus decreasing workload, culture space, time and cost.…”

Broadening the genetic base of crop brassicas by production of new intergeneric hybrid

“…Wild and weedy relatives of crop brassicas are known to be reservoirs of genes that impart resistance to biotic and abiotic stresses (Warwick et al 2000). Moreover, their cytoplasm can induce cytoplasmic male sterility (CMS) in crop brassicas, which is important for hybrid seed production in oilseed brassicas, and heterosis in vegetable brassicas (Sigareva & Earle 1997;Primard-Brisset et al 2005;Bhat et al 2007). The development of alloplasmic lines has also shown important agronomic traits like early flowering and dwarfness in B. napus (Rao et al1998).…”