TOWARDS CABBAGE (BRASSICA OLERACEA VAR. CAPITATA L) SEED PRODUCTION IN THE TROPICS

Abstract

Some morphological and flowering characteristics of ten cabbage varieties obtained from Warwick— Horticultural Research Institute, UK have been evaluated with the aim of selecting suitable varieties for the study offlowering and seed development in the tropics and to ascertain the viability of cabbage seed produced under high temperatures (20-30°C). Plants raised from seed in peat-based compost in plastic pots were grown in a controlled environment room (CER) at 20°C with 12h photoperiod and 400mmoLm 2.8-1 photosynthetic photon flux and in a glasshouse receiving natural light with a blackout system to give a 12-h photoperiod and maintained between 20 to 30°C. Eight weeks after sowing, two pots of each variety from each environment were transferred to another CER for vernalization at 4 °C for 8 weeks, after which they were returned to their respective controlled environments. Vernalization at 4°C promoted flowering in all varieties, however; varieties 11446, 6556 and 9617 flowered earlier and seeds produced in tropical conditions (20-30°C) were viable and vigorous with most varieties having 80% germination or higher. The varieties varied significantly in terms of number of leaves, height of stem and length of leaves, but canopy shape index did not vary significantly and was approximately one. The taller varieties of cabbage flowered easily, consistently showed higher levels of greenness and had lower incidence of tip. burn and splitting of the heads as compared to the shorter varieties. Varieties 3720, 5237 and 113011 can be considered as early maturing types.