Exploitation of the late flowering species Brassica oleracea L. for the improvement of earliness in B. napus L.: an untraditional approach

Abstract

The oilseed Brassica rapa flowers and matures earlier than B. oleracea, as well as their amphidiploid B. napus. Therefore, earliness of B. rapa has been investigated as a source of variation for earliness in B. napus breeding programs. Variation for days to flower exists in B. oleracea; however, its earliest flowering variant B. alboglabra flowers 2-3 weeks later than B. napus. We hypothesized that the C genome of B. alboglabra carries alleles for early flowering which are different from the C-genome alleles of B. napus; and these alleles can be used for the improvement of B. napus. To test this, we examined flowering time in pedigree and DH populations from two B. napus 9 B. alboglabra crosses. A B. napus line with about a week earlier flowering than the B. napus parent was achieved through reconstitution of its C genome following pedigree selection. Introgression of the B. alboglabra allele in the early flowering pedigree lines is also evident from the presence of B. alboglabra-specific SSR alleles in this line. However, application of doubled haploidy failed to generate any line that flowered earlier than the B. napus parent, which is probably due to the difficulty of obtaining large numbers of euploid B. napus DH lines from this interspecific cross. Thus, we demonstrate that a trait of the diploid species, which apparently looks undesirable, might in fact be highly valuable for the improvement of amphidiploids; and knowledge from this research can also be applied for other traits.

Molecular mapping of QTL alleles of Brassica oleracea affecting days to flowering and photosensitivity in spring Brassica napus

“…oleracea var. alboglabra (CC, 2 n = 18) interspecific cross with selection for earliness of flowering [ 23 ]. This line flowers about a week earlier than most of the B .…”

Reconstituting the genome of a young allopolyploid crop, Brassica napus, with its related species

“…The gene diversity of the gene pool was higher than that of traditional B. napus accessions, particularly in the C genome. This is favourable for rapeseed breeding, because the genetic diversity in the C genome is very low in the traditional B. napus (Bancroft et al, 2011;Bus et al, 2011;Delourme et al, 2013;Rahman et al, 2011;Wang et al, 2014b;Zhao et al, 2013).…”

Broadening genetic diversity inBrassica napuscanola: Development of canola-quality springB. napusfromB. napus×B. oleraceavar.alboglabrainterspecific crosses

“…Data presented in this paper would likely be different if recombinant inbred lines were developed from this interspecific cross through application of other breeding techniques and without selection for the canola-quality traits. In addition to the above-mentioned pedigree families, we also developed 14 DH lines from 656 microspore-derived embryos of F 1 plants derived from these two interspecific crosses (Rahman et al 2011). The DH lines generally had poor seed set on self-pollination as well as crossing with B. napus.…”

“…This is primarily due to the difficulty of obtaining sufficient number of F 2 seeds from the F 1 plants through manual self-pollination (manually pollinating individual flower with pollen from the same plant) or bag isolation. Sterility in the hybrids resulting from interspecific hybridization is a common phenomenon due to chromosome anomalies in meiosis [reviewed in Rahman (2013) and Rahman et al (2011)]. However, it was possible to generate a greater number of F 3 (222) plants, and with this number, it was possible to demonstrate the prospect of developing canola-quality spring B. napus families from this interspecific cross with alleles introgressed from B. alboglabra.…”