LAUSR

Brassica species are widely cultivated and important biennial and annual crops. The transition from vegetative to reproductive development in Brassica species is critical in agriculture and horticulture. Grafting is a useful tool for improving agricultural production and investigating the movement of long-range signals. Here we established a hypocotyl micrografting system in B. rapa crops and successfully grafted the rootstock of turnip to many different scion genotypes. Grafting with turnip rootstock prolonged vegetative growth, delayed flowering, and improved seed yield in rapeseed. The late-flowering turnip rootstock could delay the flowering of the scion of the early-flowering turnip accession. The BrrFLC1 (FLOWERING LOCUS C1 in B. rapa) transcript levels and the H3K4me3 levels at the BrrFLC1 locus were up-regulated and subsequently suppressed the downstream FT (FLOWERING LOCUS T) signals in the leaves of the scion to delay flowering. Vernalization treatment can efficiently promote flowering time in turnip. The non-vernalized turnip flowered early after grafting onto the rootstock of the vernalized turnip, which was accompanied by high levels of FT homolog expression in the leaves of the scion. Hypocotyl excision experiments revealed that the process of tuber formation was suppressed by removing the hypocotyl tissue, which in turn repressed the expression of tuberization-related genes. Our findings suggest that the rootstock generates mobile signals that are transported from the rootstock to the scion to fine-tune FT signaling and modulate flowering time. This article is protected by copyright. All rights reserved.