*Article* **Genetic Diversity and Genome-Wide Association Study of Architectural Traits of Spray Cut Chrysanthemum Varieties**

**Daojin Sun, Luyao Zhang, Jiangshuo Su, Qi Yu, Jiali Zhang, Weimin Fang, Haibin Wang, Zhiyong Guan, Fadi Chen and Aiping Song \***

> State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Landscaping, Ministry of Agriculture and Rural Affairs, Key Laboratory of Biology of Ornamental Plants in East China, National Forestry and Grassland Administration, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China; 2020104106@njau.edu.cn (D.S.); 2019804185@njau.edu.cn (L.Z.); sujiangshuo@njau.edu.cn (J.S.); 2019104103@njau.edu.cn (Q.Y.); 2020804199@stu.njau.edu.cn (J.Z.); fangwm@njau.edu.cn (W.F.); hb@njau.edu.cn (H.W.); guanzhy@njau.edu.cn (Z.G.); chenfd@njau.edu.cn (F.C.) **\*** Correspondence: aiping\_song@njau.edu.cn

**Abstract:** The architecture of spray cut chrysanthemum is crucial for the quality and quantity of cut flower production. However, the mechanism underlying plant architecture still needs to be clarified. In this study, we measured nine architecture-related traits of 195 spray cut chrysanthemum varieties during a two-year period. The results showed that the number of upper primary branches, number of lateral flower buds and primary branch length widely varied. Additionally, plant height had a significant positive correlation with number of leaf nodes and total number of lateral buds. Number of upper primary branches had a significant negative correlation with primary branch diameter, primary branch angle and primary branch length. Plant height, total number of lateral buds, number of upper primary branches, stem diameter, primary branch diameter and primary branch length were vulnerable to environmental impacts. All varieties could be divided into five categories according to cluster analysis, and the typical plant architecture of the varieties was summarized. Finally, a genome-wide association study (GWAS) was performed to find potential functional genes.

**Keywords:** spray cut chrysanthemum; GWAS; plant architecture; statistical analysis
