Objective Analyze the genetic variation range and diversity level of key agronomic traits in Brassica napus L. lines, establish a comprehensive multi-trait evaluation system, and screen elite lines with high yield and superior quality.

Method Taking 36 B. napus L. as research materials, eight key agronomic traits including plant height, branch position, number of primary effective branches, effective silique number per plant, seed number per silique, silique length, 1000-seed weight and yield per plant were investigated via descriptive statistics, correlation analysis, cluster analysis and principal component analysis. In addition, the comprehensive membership function score D was standardized via the min–max normalization method to obtain the standardized value D'.

Result The eight key agronomic traits of the tested lines exhibited abundant variation, with coefficients of variation ranging from 8.05% to 32.21%. The coefficient of variation of effective silique number per plant was the highest at 32.21%, followed by yield per plant with a coefficient of variation of 30.47%. Plant height had the lowest coefficient of variation of 8.05%. The eight key agronomic traits of the test lines exhibited rich genetic diversity, with the genetic diversity indices ranging from 1.75 to 2.13. Branch position had the highest genetic diversity index at 2.13. Correlation analysis indicated that plant height was extremely significantly moderate positively correlated with branch position. The number of primary effective branches showed an extremely significant strong positive correlation with effective silique number per plant, while the latter had an extremely significant moderate negative correlation with 1000-seed weight. Cluster analysis results divided 36 B. napus lines into three groups. Group Ⅰ consisted of high-yield lines, including 9 lines and accounting for 25% of the total. Group Ⅱ was mainly composed of dwarf and low-yield lines, including 17 lines and accounting for 47.22% of the total. Group Ⅲ primarily included conventional lines, including 10 lines and accounting for 27.78% of the total. Four principal components were extracted via principal component analysis with a cumulative contribution rate of 81.271%, namely silique number factor, biological yield factor, seed number per silique factor and 1000-seed weight factor. The D' values of the 36 B. napus lines ranged from 0.00 to 1.00, with lines Y15 and Y18 possessing the highest D' values.

Conclusion Group Ⅰ featured the highest effective silique number per plant and seed number per silique. Elite lines Y15 and Y18 were classified into this group, suggesting that raising these two traits is a key strategy for high-yield breeding in B. napus.