Abstract
Chrysanthemum morifolium is one of the world's four major cut flowers, valued for its ornamental and economic importance. However, high temperature stress during growth and development can reduce both yield and quality. Autophagy is a cellular self-degradation and recycling process that plays a pivotal role in maintaining homeostasis under abiotic stress. This study aimed to identify autophagy-related genes (ATGs) in C. morifolium and its close relatives, analyze their structural and evolutionary characteristics, and evaluate ATG8 expression under heat stress. Genome-wide analysis identified 130 ATGs in C. morifolium, 51 in Chrysanthemum nankingense, and 49 in Chrysanthemum lavandulifolium. Genes within the same subfamily exhibited conserved structures and domains, with fragment duplication contributing to ATG expansion. Expression profiling showed that ATG8 genes were the most highly expressed and displayed tissue specificity, while heat stress induced their transcription, peaking at 48 h. These findings provide a comprehensive genomic resource for Chrysanthemum ATGs and indicate a potential role for ATG8 in heat stress responses, offering a basis for future studies aimed at improving thermotolerance in this ornamental crop.