Introducing gene-edited copies of BrSOC1 genes into late-bolting inbred Chinese cabbage lines effectively delays bolting

Abstract Background Late bolting occurs when a plant inherits two recessive late-bolting alleles at the same locus, requiring time and effort for sustainable cultivar development. Results We generated late-bolting F1 hybrids by crossing Chinese cabbage (Brassica rapa) lines genome-edited in SUPPRESSOR OF OVEREXPRESSION OF CO1 (BrSOC1) with late-bolting inbred lines. We generated F1 hybrids by crossing Cas9-free lines with knockouts in two or three BrSOC1 genes to early- or late-bolting inbred lines. Crossing brsoc1 knockout lines with the early-bolting 20 inbred line delayed bolting compared with parental lines. However, the extent of delayed bolting was more pronounced when using late-bolting inbred lines as parents. We selected JN06 and JN08 as late-bolting inbred lines with low expression of BrSOC1s: F1 hybrids derived from crosses between brsoc1s and JN06 or JN08 showed significantly improved late-bolting traits, with more days after bolting and more leaves produced, surpassing those of the parental lines. Notably, F1 hybrids carrying one gene-edited copy of each BrSOC1 exhibited a greater delay in bolting, of up to 12 days, compared with F1 hybrids carrying fewer gene-edited brsoc1 copies. The expression levels of genes downstream of SOC1 were also significantly lower in the F1 hybrids compared with the parental lines. Furthermore, these F1 hybrids demonstrated greater resistance to bolting than commercial varieties. Conclusions Our findings highlight the efficacy of generating F1 hybrids using genome-edited brsoc1s as a parent to inhibit bolting in Chinese cabbage and expedite the breeding of cultivars with improved traits.