Physiological and molecular characterization of two inbred radish lines with different bolting times = 추대시기가 서로 다른 무 계통간 생리학적, 분자생물학적 개화 특성 규명

Abstract

The radish (Raphanus sativus L.) is an important Brassicaceae root vegetable crop worldwide. Several studies have been conducted concerning radish breeding. There are major challenges to prevent premature bolting in spring plantings. Here, we performed the characterization of two inbred radish lines which vary in bolting time. "Late bolting radish" (NH-JS1) and "early bolting radish" (NH-JS2) were generated by a conventional breeding approach. The two inbred lines showed different bolting phenotypes depending on vernalization time at 4°C. NH-JS1, the late bolting radish, was less sensitive to cold treatment and the less sensitivity was inversely proportional to the duration of the vernalization. We also measured gene expression levels of the major bolting time related genes in the NH-JS1 and NH-JS2 lines. RsFLC1 plays a central role in the timing of flowering initiation. It is a strong repressor and it's transcript is highly expressed in NH-JS1 compared to NH-JS2 under no treatment and vernalization conditions. RsFRI, a positive regulator of RsFLC, is also highly expressed in NH-JS1 compared to NH-JS2 regardless of vernalization. In contrast, RsSOC1, suppressed by FLC as a floral integrator gene, showed the most difference, a 5-fold increase, between NH-JS1 and NH-JS2 under vernalization conditions. From these results, we conclude that NH-JS1 showed a late flowering phenotype after cold treatment due to the expression differences of flowering time regulator genes rather than difference sensitivity to cold. These results may be useful to understand the control mechanisms of flowering time and may help identify molecular markers for selecting late bolting trait in radish.