Objective Castanea mollissima is one of the important economic forest species in China, but the evaluation indicators for their dwarfism traits are not yet perfect. This study aims to screen out more effective evaluation indicators to accurately and comprehensively evaluate the dwarfing traits of chestnut germplasm, providing theoretical basis for better collection, cultivation, and utilization of chestnut dwarfing germplasm resources.

Method 80 chestnut germplasm resources planted in Qianxi County, Hebei Province of northern China were selected as the research objects. Five trees were selected during the maturity stage of branches and leaves, and three standard fruit bearing branches were selected from the outer and middle parts of the crown in four directions: east, south, west, and north. The branching angle, branch length, branch diameter, pitch number, internode length, petiole length, petiole diameter, sharpness index, and leaf shape index were measured and calculated. The dwarfism related morphological indicators of 80 chestnut germplasm were screened and comprehensively evaluated using a combination of normality test, correlation analysis, and principal component analysis, and the dwarfism level was divided and identified.

Result (1) The overall distribution of branch length, internode length, branch diameter, pitch number, branching angle, leaf shape index, petiole length, petiole diameter, and sharpness index showed a relatively standard normal distribution. (2) Considering that correlation between the two indicators of branching angle and sharpness index and other morphological indicators was not significant, the seven indicators of branch length, branch diameter, pitch number, internode length, leaf shape index, petiole length, and petiole diameter were selected as effective evaluation indicators for principal component analysis. (3) Through comprehensive evaluation, 80 chestnut germplasms were classified into dwarfing type (6), intermediate type (40), arborization type (27), and extremely arborization type (7).

Conclusion Branch length, branch diameter, pitch number, internode length, leaf shape index, petiole length and diameter can be used as effective indicators to evaluate the morphological traits of chestnut dwarfism. C. mollissima ‘Duanzhiyabian’, C. mollissima ‘Zipo’, C. mollissima ‘Yanshanduanzhi’, C. mollissima ‘Zunyu’, C. mollissima ‘Tafeng’, and C. mollissima ‘Youfeng’ have been identified as chestnut dwarfism germplasm. The research results will provide a basis for the development and utilization of chestnut dwarfism germplasm resources.