| Eleven winter rapeseed (Brassica campestris L.) cultivars with different levels of cold resistance were grown in four ecological regions in Gansu province, northwest China. Changes in the progression of growth, agronomic traits, and quality of northward-expanded rapeseed plants were determined, and their correlations with major regional ecological factors were evaluated, in order to provide a reference for northward expansion and cultivation of this crop. Compared with those in the original growing area (Tianshui), northward-expanded rapeseed plants exhibited great changes in the progression of growth, as reflected mainly by the significantly shortened growth period in pre-winter and prolonged over-wintering period. Total growth period (number of days) between seedling establishment and maturation stages after wintering was not changed. However, early growth process during seedling establishment to final flower stage was accelerated, while the podding stage was prolonged. Additionally, northward-expanded rapeseed cultivars had taller plant height and lower branch part, with shorter primary inflorescence than the control plants. The former had a reduced number of siliques per plant but an increased number of branches, showing poor plant morphology. The number of seeds per silique and thousand seed weight were increased, suggesting improvements in silique and seed traits. Seed oil content as well as oleic, linolenic, and erucic acid contents became increased, which coincided with reductions in linoleic, eicosenoic acid, and thioglycoside contents. Seed oleic and linolenic acid contents were positively correlated with latitude and altitude, and negatively correlated with rainfall, mean annual temperature, and temperature of the coldest month, whereas gadoleic acid and thioglycoside contents showed the opposite. In conclusion, northward expansion of winter rapeseed cultivars resulted in the poor plant morphology but improved silique and seed traits; during the progression of plant growth, the pre-winter growth period was shortened, but the over-wintering period was prolonged. The growth after seedling establishment was accelerated, and prolonging of podding stage facilitated gain of seed weight. Also, seed oil content was increased. High latitude and altitude were beneficial to the accumulation of oleic and linolenic acids, whereas high rainfall and low temperature were favorable for the accumulation of eicosenoic acid. |