Combined evaluation of agronomic and quality traits to explore heat germplasm in celery (Apium graveolens L.)

•The genetic diversity of celery germplasms was evaluated based on agronomic traits, quality traits and heat tolerance.•Apigenin and cellulose were the main contributors to the variation of quality traits.•The comprehensive evaluation value of celery after heat stress had a highly significant positive correlation with the heat damage index.•The heat resistance of celery was related to its hollow/solid and color.