Phenotypic evaluation and analysis of important agronomic traits and nutritional quality in purple flowering stalk (Brassica campestris L. ssp. chinensis var. purpurea Hort.)

• A comprehensive evaluation of the genetic diversity based on agricultural traits and nutritional traits were conducted on 127 genotypes of purple flowering stalks. • The possible relationship between agronomic traits and nutritional quality of purple flowering stalk were revealed. • Ten purple flowering stalk varieties with high comprehensive quality were ranked as excellent breeding improvement potential resource. Purple flowering stalk, with vivid color and high yield, is a special vegetable rich in glucosinolates. This study analyzed and evaluated the variability of agronomic traits and nutritional quality of 127 genotypes of purple flowering stalks. The results showed that the genetic diversity index of qualitative traits varied from 0.16 (leaf vein clarity) to 1.57 (cotyledon color), and quantitative traits varied from 1.48 (rosette number) to 2.06 (cotyledon groove depth). Moreover, the highest coefficient of variation in quantitative traits was found in three yield-related traits: main flowering stalk weight, main flowering stalk length, and lateral flowering stalk number (63.35 %, 45.17 %, and 46.57 %, respectively). Cluster analysis divided accessions into three major clusters. The hierarchical cluster analysis implied that the yield-related traits and nutritional traits contribute most to the distinction. In principal component analysis based on yield and nutritional traits, the eight components explained 76.4 % of the variance in the data. All varieties were evaluated by comprehensive score, and the top ten of them (CS 70, CS 56, CS 105, CS 114, CS 113, CS 129, CS 93, CS134, CS 35, CS 74) with different characters can be used in the improvement of breeding. Correlation analysis suggested that shorter flowering stalks may have more content of total glucosinolates, ascorbic acid, and soluble protein. In conclusion, this work provides basic materials and theories for purple flowering stalk breeding.