This study investigated the effects of different temperature treatments (18, 24, and 30 °C) on apex development in tropical cauliflower cultivars of varying maturity types. Two commercial cultivars, H-37 (early maturity) and H-80 (mid–late maturity), were used as the testing materials. ‘H-37’ reached the curd-initiation phase earlier than ‘H-80’ and showed superior growth during the curd’s initial development phase under all temperature treatments. Analysis of variance revealed significant effects regarding main temperature and cultivar as well as their interaction. ‘H-37’ at a temperature of 18 °C demonstrated the optimal transformation of apex development from the vegetative to reproductive stage. A temperature of 24 °C promoted the apex development of ‘H-37’ at the curd initial development phase. Gene expression analysis results indicated that the BoFLC2 expression of ‘H-37’ was significantly down-regulated than that of ‘H-80’ after curd initiation and advanced growth. A temperature 30 °C accelerated the ending of juvenile stage and forward to curd initiation in ‘H-80’ and declined with temperature decreased. Moreover, expression of the BoFLC2 transcript level of both tropical cauliflower cultivars nearly disappeared at the high temperature of 30 °C following curd initiation, suggesting that heat stress hinders curd formation. The results of this study also indicate that the number of leaves required to induce curd initiation is less than nine in tropical cauliflower at temperatures of 18 to 30 °C. In conclusion, under nonvernalized high temperatures, different cultivars of tropical cauliflower can initiate curd development but with a different pattern from those cultivars grown in temperate zones. This information may provide novel insights for cauliflower farmers or breeders in tropical regions.
Chen-Yu Lin, Kan-Shu Chen, Hsuan-Ping Chen, Hsiang-I Lee, and Ching-Hsiang Hsieh
Yi-Chen Chen, Wei-Chun Chang, San-Tai Wang, and Shu-I Lin
Grafting is widely used in the commercial production of cucurbits (Cucurbitaceae) and solanaceous (Solanaceae) vegetables, but seldom in the production of cruciferous vegetables such as cabbage (Brassica oleracea Capitata group). In our study, we developed a tube grafting method for cabbage using the ‘K-Y cross’ cabbage as the scion and ‘Tsuei Jin’ chinese kale (B. oleracea Alboglabra group) as the rootstock (K-Y/TJ), and then used the K-Y/TJ grafted seedlings to identify the best healing conditions. The examined healing conditions included temperature (15, 20, or 25 °C), relative humidity (RH; 75%, 85%, or 95%), and light intensity (high light intensity, 79 to 107 μmol·m–2·s–1; low light intensity, 38.6 to 58.8 μmol·m–2·s–1; or full darkness, 0 μmol·m–2·s–1). Considering all the healing conditions, the K-Y/TJ grafted seedlings healing at 20 °C, 95% RH, and high light intensity exhibited survival rates of up to 96.7% and overall superior seedling quality. ‘K-Y cross’ cabbages were then grafted onto chinese kale rootstocks, and the head traits of all grafted plants were comparable to those of nongrafted and/or self-grafted ‘K-Y cross’ plants. ‘K-Y cross’ plants grafted on ‘Jie Lan’ chinese kale rootstocks had greater ascorbic acid and total soluble solid (TSS) contents than nongrafted and self-grafted ‘K-Y cross’ plants. Overall, this research describes a successful tube grafting method and the optimal healing conditions for grafted cabbage seedlings, which can be used as a tool to improve head quality.