A candidate mechanism controlling floral repression in hardly flowering cabbage mutant
Yu Kinoshita is a PhD student in the Graduate School of Agriculture at Kyoto University, Japan. She has studied a “hardly” flowering cabbage mutant under the supervision of Professor Munetaka Hosokawa. This cabbage mutant was found among the open-pollinated line ‘T15’ in an open field by Professor Susumu Yazawa 42 years ago and was named as ‘nfc’ (non-flowering cabbage). ‘nfc’ hardly flowers in the spring season even after plenty of low-temperature periods. Therefore, ‘nfc’ has been continually propagated vegetatively by cuttings. Yu’s research focuses on measuring the flowering characteristics of ‘nfc’ in detail and determining the mechanism. In the first experiment, throughout a 3-year cultivation period, ‘T15’ plants flowered, while the flowering ratios of ‘nfc’ propagated by cuttings at the 1st, 2nd, and 3rd year were 0, 32 and 4%, respectively. Additionally, even if ‘nfc’ plants flower, they do not flower in the same way as ‘T15’ in terms of flowering date and number of flowering shoots. Moreover, the terminal buds of ‘nfc’ flowering plants continued to grow vegetatively, even when their lateral shoots flowered. In the second experiment, the expression level of the floral promoter gene BoFT greatly increased in ‘T15’ after vernalization, while in ‘nfc’ it slightly increased. Therefore, floral repression in ‘nfc’ was caused by low expression of BoFT. In the third experiment, when Yu grafted ‘nfc’ onto bolting radish rootstocks according to Motoki et al. (2019), 27% of ‘nfc’ scions flowered. Since FLOWERING LOCUS T (FT) protein is considered to be a major transmissible signal involved in floral induction by grafting, this result supported the results of experiment 2. Additionally, the flowering characteristics of ‘nfc’ self-pollinated progenies were similar to ‘nfc’. Therefore, the hardly flowering trait is inheritable and ‘nfc’ is homozygous for the causal genes related to the hardly flowering trait.
Yu Kinoshita won the ISHS Young Minds Award for the best oral presentation at the III Asian Horticultural Congress (AHC2020) in Thailand in December 2020.
Yu Kinoshita, Lab. of Vegetable & Ornamental Horticulture, Kyoto University, Kitashirakawa-Oiwake cho, Sakyo-ku, Kyoto 606-8502, Japan, e-mail: firstname.lastname@example.org
Reference: Motoki, K., Kinoshita, Y., and Hosokawa, M. (2019). Non-vernalization flowering and seed set of cabbage induced by grafting onto radish rootstocks. Front. Plant Sci. 9, 1967 https://doi.org/10.3389/fpls.2018.01967.
The article is available in Chronica Horticulturae