A review on the possibility of flowering and seed production of cabbage in the tropics.

Cabbage (Brassica oleraceae L. var. capitata.) is one of the most popular 'exotic' vegetables in tropical countries like Ghana. It is a high value crop because there is a demand from most expatriate staff, restaurants, hotels and a large section of the population, especially in the cities and urban areas. The crop is also popular because cabbages are easy to cultivate, durable in the market place, have high nutritive value (Dickson and Wallace, 1986; Norman, 1992) and there is increasing evidence that their consumption is associated with reduced incidence of some types of cancer (Chiang et al., 1993; Rungapamestry et al., 2006). Almost all the seeds for cabbages grown in tropical countries are imported and the countries 'spend substantial amounts on importation of seeds of exotic vegetables. Seeds of cabbage are very expensive and this causes considerable constraint to its large scale production since few farmers can afford the high prices. The seeds are imported because cabbage requires low temperatures to induce flowering (Nieuwhof, 1969; Yamaguchi, 1983), a phenomenon known as vernalization, but the average annual temperature in Ghana, even at high altitudes, is about 24°C.