The genetic basis of flowering time and photoperiod sensitivity in rapeseed (Brassica napus L.).

The objective of this study was to dissect the genetic control of days to flowering (DTF) and photoperiod sensitivity (PS) into the various components including the main-effect quantitative trait loci (QTLs), epistatic QTLs and QTL-by-environment interactions (QEs). Doubled haploid (DH) fines were produced from an F1 between two spring Brassica napus cultivars Hyola 401 and Q2. DTF of the DH lines and parents were investigated in two locations, one location with a short and the other with a long photoperiod regime over two years. PS was calculated by the delay in DTF under long day as compared to that under short day. A genetic linkage map was constructed that comprised 248 marker loci including SSR, SRAP and AFLP markers. Further QTL analysis resolved the genetic components of flowering time and PS into the main-effect QTLs, epistatic QTLs and QEs. A total of 7 main-effect QTLs and 11 digenic interactions involving 21 loci located on 13 out of the 19 linkage groups were detected for the two traits. 3 main-effect QTLs and 4 pairs of epistatic QTLs were involved in QEs conferring DTF. One QTL on linkage group (LG) 18 was revealed to simultaneously affect DTF and PS and explain for the highest percentage of the phenotypic variation. The implications of the results for B. napus breeding have been discussed.

Development of PCR-based markers linked to the fertility restorer gene for the polima cytoplasmic male sterility in rapeseed (Brassica napus L.).

Bulked segregant analysis was used to identify RAPD markers linked to the Rfp of pol cms in rapeseed (Brassica napus L.) from the fertile and sterile DNA bulks. DNA bands amplified from 1040 random 10-mer primers were screened. Two polymorphic bands S1019(720) and S1036(810) were found linked to the Rfp locus at the same side with a map distance of 5.8 cM and 12.3 cM respectively. These polymorphic fragments were cloned and sequenced. Nucleotide sequence information was used to design 20-24-mer oligo nucleotide primers for PCR amplification. The SCAR markers that generated from the long primers showed the same pattern of segregation as the original RAPD markers in the backcross population. The SCAR markers would facilitate selection on the Pol CMS restorer lines in rapeseed.