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

Main conclusion: Genome-edited brsoc1s enabled the development of late-bolting F1 hybrids with improved traits in Chinese cabbage, demonstrating more effective approach to enhancing sustainable cultivars. Late bolting in plants is influenced by inheriting two recessive late-bolting alleles at the same locus-a trait that traditionally requires considerable time and effort to develop in sustainable cultivars. In this study, we developed late-bolting F1 hybrids by utilizing genome-edited Chinese cabbage (Brassica rapa) lines carrying targeted mutations in SUPPRESSOR OF OVEREXPRESSION OF CO1 (BrSOC1). Cas9-free knockout lines harboring mutations in two or three BrSOC1 genes were crossed with both early- and late-bolting inbred lines. Notably, F1 hybrids derived from brsoc1 knockout lines crossed with the early-bolting inbred line 20 (IL_20) exhibited delayed bolting compared to their parental lines. This delay was more pronounced when the late-bolting inbred lines IL_JN06 and IL_JN08-both characterized by low BrSOC1s expression-were used as crossing partners. The resulting F1 hybrids significantly outperformed their parents in late-bolting traits, showing extended bolting time and increased leaf production. The greatest delay, extending up to 12 days, was observed in hybrids carrying one gene-edited copy of each BrSOC1 gene. Furthermore, these hybrids exhibited significantly reduced expression of downstream flowering genes and enhanced bolting resistance compared to commercial cultivars. Our findings demonstrate that using genome-edited brsoc1s alleles as parental lines in crossbreeding is an effective strategy to accelerate the development of late-bolting Chinese cabbage cultivars.