Objective To systematically evaluate the genetic diversity of phenotypic traits in mustard (Brassica juncea Coss) germplasm resources and to enhance their innovative utilization.

Method A total of 60 mustard germplasm resources were assessed based on 13 qualitative and 10 quantitative traits. Statistical analyses included variation analysis, principal component analysis, correlation analysis, and cluster analysis.

Result Significant variations were observed in plant type and leaf morphology among the 60 mustard germplasm resources. The genetic diversity index of quantitative traits was higher than that of qualitative traits. Correlation analysis revealed strong associations among phenotypic traits. Among the yield-related traits, tiller number showed highly significant correlations with both the number of rosette leaves and individual plant weight. Plant height, plant spread, and individual plant weight were also significantly correlated with each other. According to the principle of eigenvalue greater than 1, six principal components associated with 11 phenotypic traits were extracted, accounting for a cumulative variance contribution rate of 75.999%. These components represented key phenotypic characteristics such as plant type, growth vigor, leaf morphology and tillering ability, and can serve as important morphological indicators for parent selection in breeding new mustard varieties. Cluster analysis classified the 60 germplasm resources into six distinct groups. Group II exhibited medium plant height, erect plant type, relatively long leaves, and doubly serrated leaf margin. Group IV and VI displayed leaves without lobes and mainly wavy leaf margins. Group V displayed a plant height of over 80 cm, erect plant type, mosaic leaves, and leaf lobes mostly deeply or completely divided,representing local mustard types from Meizhou, namely Sangengli or its derivative types.

Conclusion This study revealed the genetic diversity of mustard germplasm resources from multiple perspectives, providing a foundation for enhancing the efficiency of germplasm utilization.