Evaluation of the Low‐Temperature Tolerance of Rapeseed Genotypes at the Germination and Seedling Emergence Stages

ABSTRACT Low temperature is a main adverse factor affecting successful seedling establishment in the Yangtze River basin, and thus low‐temperature stress tolerance at the germination and seedling emergence stages is an important attribute for rapeseed ( Brassica napus L.) production. The present study was conducted to evaluate the low‐temperature stress tolerance indices (STIs) of a large conventional rapeseed genotype population at the germination and seedling emergence stages. Twelve seed germination‐ and seedling emergence‐related indices were investigated under normal and low‐temperature conditions, and the broad‐sense heritability of these indices ranged from 25.4 to 57.6%. Therefore, the selection of genotypes with strong low temperature tolerance is a feasible way to guarantee seedling establishment. Using principal component analysis, the STIs during the seed germination and seedling emergence stages have been divided into three main categories: dry matter weight, germination speed and final germination percentage, and root length with a seedling vigor index. The top three genotypes ranked by comprehensive STI score were Huayou No. 2, SWU44, and 2012‐K8053; the bottom three genotypes ranked by comprehensive STI score were Chuanyou18, wx1025, and 97096. The results of the present study could provide valuable information for breeders to utilize the rapeseed germplasm resources in the Yangtze River basin to achieve the goal of low‐temperature resistance breeding.