The influence of vernalization time and day length on flower induction of radish (Raphanus sativus L.) under controlled and field conditions

Authors: HALUK ÇAĞLAR KAYMAK, İSMAİL GÜVENÇ

Abstract: This research was carried out to identify an alternative model plant for the study of vernalization among the cultivars that are commonly grown in Turkey and the influence of vernalization and day length on the flowering of radishes (Raphanus sativus L.) under controlled and field conditions throughout 2003, 2004, and 2005. In this study, 6 radish cultivars (Raphanus sativus L. cvs. 'Siyah,' 'Beyaz,' 'Antep,' 'İri Kırmızı,' 'Red Cherry F_1,' and 'Cherry Belle') were used in the laboratory and field experiments as plant material. Under the controlled conditions, 2 day length periods (8 and 16 h light) and 5 vernalization times (0, 5, 10, 15, and 20 days at 5 °C) were studied as the main factors. Under the field conditions, the day length and the changes in vernalization times were provided by different sowing dates. It was determined that flowering did not occur when the vernalization time was less than 15 days during both the long days (LD) and short days (SD) for Siyah. All the same, it was determined that except for Siyah, other cultivars could not flower without being vernalized during SD. Besides this, it was determined that under the field conditions, different sowing dates had an impact on flowering rates. Contrastingly, in early sowings of Siyah, all cultivars showed flowering of up to 88.72%. The study reveals that Antep, Beyaz, İri Kırmızı, Red Cherry F_1, and Cherry Belle have a facultative vernalization response; cold exposure is not required for flowering, but flowering can occur more rapidly after cold treatment. Siyah, in contrast, has an obligate requirement for cold treatment and thus cannot flower without prior cold exposure.

Keywords: Flower induction, day length, Raphanus sativus L., vernalization

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