Mapping of the AgPPur gene for the purple petiole in celery (Apium graveolens L.)

Celery (Apium graveolens L.) is a vegetable widely planted and eaten all over the world, and its petiole is the main edible part. To date, there are very few reports about the inheritance and gene cloning of celery petiole color. In this study, based on the purple petiole celery inbred line (ppur) discovered in the early stage of our research, its petiole is purple, and its dwarf stem and leaves are green. The F2 segregation population was configured by crossing it with inbred lines with white petioles. The genetic analysis showed that the purple petiole to white petiole segregation ratio was 3:1 and that the purple trait was dominantly inherited under single gene control. The ppur locus was localized within 324 kb on Chr09 by map cloning, and the gene AgPPur, whose homolog in Arabidopsis encodes the NAC transcription factor, was targeted by RT‒PCR and sequence comparison. Sequencing of both parents revealed a 4-bp deletion at the 5′ UTR in white petiole material, and the gene marker Indel-A4 developed based on this deletion was 100% accurate in both F2 populations. Validation in 30 celery materials with different colored petioles in the laboratory revealed that the marker could perfectly distinguish between purple/nonpurple petiolar materials. Therefore, AgPPur was considered to be the candidate gene controlling purple petioles in celery. Our results could not only improve the efficiency and accuracy of celery breeding but also help to understand the mechanism of anthocyanin synthesis in celery.