Identification of quantitative trait loci for flowering time traits in ramie (Boehmeria nivea L. Gaud)

Ramie is an important fiber and forage crop in China. Breeding of late- or non-flowering varieties with higher vegetative yields is an important goal because this high yield is required for ramie production for both fiber and feed use. However, the genetic basis for the flowering time trait is poorly understood, and this has severely hindered the improvement of this trait in ramie breeding. In our previous study, a genetic linkage map has been constructed based on an F-2 agamous line (FAL) population derived from two parents, Qingyezhuma and Zhongzhu 1. In this study, four traits, i.e., days from sprouting to the appearance of male flower buds (DSAMB), days from sprouting to male flowering (DSMF), days from sprouting to the appearance of female flower buds, and days from sprouting to female flowering (DSFF), were investigated in this FAL population. Significant difference between two parents and large variation in FALs was observed for these four traits. The analysis of quantitative trait locus (QTL) for these four flowering time traits was performed in ramie for the first time. Finally, a total of 7, 5, 10, and 7 QTLs for DSAMB, DSMF, DSAFB, and DSFF, respectively, were identified in the FAL population in 2 years. Of these 29 QTLs, 15 were detected in both years, and 16 QTLs exhibited overdominance. Moreover, 11 QTL clusters were identified. The identification of these QTLs will be helpful for molecular designing of the flowering time traits in ramie breeding programs by marker-assisted selection.