Plant materials and field experiments

A panel of 472 rapeseed accessions collected worldwide and stored at the National Mid-term Gene Bank for Oil Crops of China was used for association analysis in this study. The informations of inbred lines about their origin and germplasm type have listed in a previous report (Li et al., 2014).

Field experiments were implemented in six environments across three growing seasons. During the 2013/2014 growing season, the association population was grown at Yangluo (114.50°E, 30.38°N) in Hubei province, which is referred to as E1; during the 2014/2015 growing season, the experiment was conducted at Wuhan (113.68°E, 30.58°N) and Yangluo, which are both in Hubei province, and are referred to as E2 and E3, respectively; and during the 2015/2016 growing season, the association panel was cultivated at Wuhan, Yangluo, and Changsha (113.00°E, 28.22°N, in Hunan province), and are referred to as E4, E5, and E6, respectively. A randomized complete block design with three replicates was adopted in each environment. Each plot contained two rows and 12–15 plants in each row, the distance between plants was 0.2 m within each row, and the space between rows was 0.3 m.