Mapping and characterization of FLC homologs and QTL analysis of flowering time in Brassica oleracea

Abstract

The FLC gene product is an inhibitor of flowering in Arabidopsis. FLC homologs in Brassica species are thought to control vernalization. We cloned four FLC homologs (BoFLCs) from Brassica oleracea. Three of these, BoFLC1, BoFLC3 and BoFLC5, have been previously characterized. The fourth novel sequence displayed 98% sequence homology to the previously identified gene BoFLC4, but also showed 91% homology to BrFLC2 from Brassica rapa. Phylogenetic analysis showed that this clone belongs to the FLC2 clade. Therefore, we designated this gene BoFLC2. Based on the segregation of RFLP, SRAP, CAPS, SSR and AFLP loci, a detailed linkage map of B. oleracea was constructed in the F(2) progeny obtained from a cross of B. oleracea cv. Green Comet (broccoli; non-vernalization type) and B. oleracea cv. Reiho (cabbage; vernalization type), which covered 540 cM, 9 major linkage groups. Six quantitative trait loci (QTL) controlling flowering time were detected. BoFLC1, BoFLC3 and BoFLC5 were not linked to the QTLs controlling flowering time. However, the largest QTL effect was located in the region where BoFLC2 was mapped. Genotyping of F(2 )plants at the BoFLC2 locus showed that most of the early flowering plants were homozygotes of BoFLC-GC, whereas most of the late- and non-flowering plants were homozygotes of BoFLC-Rei. The BoFLC2 homologs present in plants of the non-vernalization type were non-functional, due to a frameshift in exon 4. Moreover, duplications and deletions of BoFLC2 were detected in broccoli and a rapid cycling line, respectively. These results suggest that BoFLC2 contributes to the control of flowering time in B. oleracea.

Identification of quantitative trait loci controlling late bolting in Chinese cabbage (Brassica rapa L.) parental line Nou 6 gou

“…Similarly, Okazaki et al (2007) reported that BoFLC2 plays a central role in the repression of flowering in B. oleracea (Okazaki et al 2007). Wang et al (2009) reported that BnC6FTa, the orthologous gene of BrFTa, was associated with the major QTL for flowering time in B. napus.…”

Flowering Time Quantitative Trait Loci Analysis of Oilseed Brassica in Multiple Environments and Genomewide Alignment with Arabidopsis

“…One of the identified flowering time loci, VFR2, was mapped as a single Mendelian locus that overlaps precisely with BrFLC1 (Kole et al 2001). In B. oleracea, the gene associated with the largest genetic effect (36.8%) among flowering time QTL has been designated BoFLC2 (Okazaki et al 2007). The diploid Brassica genomes are three to five times larger than the Arabidopsis genome, which suggests that many flowering time QTL remain undiscovered.…”

Correlation analysis of genetic diversity and population structure of Houttuynia cordata Thunb with regard to environment

“…The polymorphism generation is due to the gap length between introns and promoters and varies between individual and species. This is being widely used in genetic map construction (Lin et al, 2005), QTL analysis (Okazakik et al, 2007), genetic diversity analysis , heterosis prediction , species identification, and other fields.…”