Mapping of QTLs for Bolting Time in Brassica rapa (syn. campestris) under Different Environmental Conditions

The bolting time of varieties used as leafy vegetables or turnips within the Brassica rapa (syn. campestris) species is important, because it affects the yield and quality of the harvested products. In Brassica rapa, the transition from the vegetative to reproductive phase is influenced by environmental factors, such as day-length and low temperature. In order to analyze the genetic basis of bolting time, an AFLP linkage map was constructed using doubled haploid (DH) lines derived from the F1 hybrid between A9408 and Homei P09. QTL analysis of bolting time was performed based on the evaluation under two field conditions and three artificial conditions differing in day-length and/or temperature. Out of a total of ten QTLs detected, two QTLs showed a low temperature sensitivity. The most effective QTL, BT1, was found to be the main locus controlling the vernalization response and the allele of Homei P09 was highly responsive to low temperature compared with that of the late parent A9408. These results could be useful for marker-assisted selection and isolation of the genes responsible for bolting time in Brassica rapa.