Identification and mapping QTLs of bolting time in purple cai-tai (Brassica rapa L. var. purpurea)

Bolting time is a crucial agronomic trait for yield and quality in purple cai-tai (Brassica. rapa L. var. purpurea), but the genetic mechanism controlling the procedure remains unknown. In the present study, a double haploid (DH) population derived from two inbred lines of purple cai-tai 4-1 and 040-3 was constructed to identify the quantitative trait loci (QTLs) of bolting time. Genetic linkage map was performed by JoinMap version 3.0 using SSR, SRAP and ESTP molecular markers. A total of one hundred and thirty-eight molecular markers were integrated into ten linkage groups (LGs), which were anchored to the corresponding chromosome of the B. rapa reference genome. The genetic linkage map covers 1253.1 cM, with an average distance of 9.08 cM between two adjacent markers. Five quantitative trait loci (QTLs) were identified to control bolting time and explaining variations from 17.7 to 44.2%. The genetic results of bolting time will be useful for future breeding of late bolting in purple cai-tai.