Abstract
Tibetan turnip and oilseeds are the most important vegetables cultivated in the Qinghai-Tibet Plateau. Our field observations identified a dominant early-bolting phenotype at the vegetative growth stage in the Tibetan turnip, which was possibly due to cross-pollination contamination from nearby oilseeds. We performed genetic and molecular experiments to explore the main reason for early bolting. We first analyzed gene expression and genomic sequence variation of turnip and oilseed BraFLC2, a gene that acts as a key repressor of flowering in turnip in a dosage-dependent manner. We found that the differences in flowering time and life habits between turnip and oilseeds were closely correlated with the genetic variations in BraFLC2. We further identified that the early-bolting turnip was the hybrid between turnip and oilseeds by selecting BraFLC2 as a testing gene. Furthermore, using an artificial hybridization experiment, we found that the heterozygote and low levels of BraFLC2 expression promoted early bolting in hybrid plants. These findings indicate that early-bolting in turnip is caused by cross-pollination contamination from oilseeds under human agricultural activities. We propose a strategy of strict seed screening, cultivation isolation and turnip breeding to ensure high quality and yield.