Curd initiation and transformation in tropical cauliflower cultivars under different temperature treatments

Abstract

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.