A 43 Bp-Deletion in the Gene Reducing Anthocyanins Is Responsible for Keeping Buds Green at Low Temperatures in Broccoli.

Most broccoli cultivars or accessions exhibit green buds under appropriate growth conditions, which turn purple at cold temperatures. However, certain cultivars consistently maintain green buds both during normal growth and at cold temperatures. In this study, we used BSA-seq (bulked segregation analysis-sequencing), along with fine mapping and transcriptome analysis to identify a candidate gene (flavonoid 3'-hydroxylase, ) responsible for reducing anthocyanin accumulation in the mutant and HX-16 broccoli ( L. var. ), which could retain green buds even at low temperatures. A 43-bp deletion was detected in the coding sequence (CDS) of the gene in HX-16 and the mutant , which significantly decreased expression and the accumulation of cyanidin and delphinidin in the mutant . Furthermore, the expression of was upregulated at low temperatures in the wild line PS. Our results demonstrated the efficacy of utilizing the 43-bp InDel (Insertion-Deletion) in predicting whether buds in L. will turn purple or remain green at cold temperatures across forty-two germplasm materials. This study provides critical genetic and molecular insights for the molecular breeding of and sheds light on the molecular mechanisms underlying the effect of low temperatures on bud color in broccoli.