Celery, an important vegetable in the Apiaceae family, is widely cultivated for its nutritional and medicinal value. It is typically divided into three varieties, like a family of three siblings with unique traits: A. graveolens var. dulce (common celery) with thick, juicy, solid petioles; A. graveolens var. rapaceum (celeriac) with a round, enlarged hypocotyl; and A. graveolens var. secalinum (smallage or leaf celery) with slender petioles and a strong aroma. However, most current research focuses on common celery, leaving the other siblings overlooked. This limits a complete picture of the evolutionary history and genetic diversity. 

Researchers from Wuhan Botanical Garden have completed the first high-quality chromosomal-level genome assembly of celeriac through whole-genome sequencing and constructed a comprehensive genomic variation map by re-sequencing 177 representative celery accessions. 

Through phylogenetic, population structure, and genetic diversity analyses, this study has revealed that Mediterranean smallage represented the most ancient cultivated celery type, supporting the hypothesis of celery’s origin in the Mediterranean. Corresponding author professor GAO Lei explains, “After initial domestication in this region, celery was artificially selected in two directions: one for celeriac by enlarging the hypocotyl, and the other for common and Chinese leaf celery by improving petiole structure and flavor”.

The petioles of common celery are solid and succulent, whereas those of celeriac and smallage are often slender and hollow. Cross-sectional observation of the petioles revealed that the cavities in hollow petioles gradually formed during the developmental process. Through transcriptome analysis, SNP(single nucleotide polymorphisms)-GWAS(genome-wide association studies), and SV(structure variant)-GWAS, researchers identified that the formation of the hollow/solid petiole trait in celery was directly attributed to the presence or absence of a NAC gene, namely Agrc04g007090. Population variation analysis showed that this gene was present in all hollow celery but completely absent in all solid petiole samples. Further functional validation in Arabidopsis indicated that Agrc04g007090 likely regulated the formation of hollow petioles in celery by controlling the programmed cell death of petiole pith cells. 

The results elucidate the cultivation and domestication history of celery, deepening the understanding of the molecular mechanisms and genetic basis of important agronomic traits in celery. It provides valuable genetic resources for the future improvement and conservation of celery varieties.

Results have been published in Plant Biotechnology Journal, titled “Genome of root celery and population genomic analysis reveal the complex breeding history of celery”. This project was supported by the National Natural Science Foundation of China, the Hubei Provincial Natural Science Foundation Innovation Group Project, and the Hubei Hongshan Laboratory Fund.

Genetic diversity of A. graveolens (Image by Lai Enhui et al.)