Control of floral morphogenesis in cauliflower (Brassica oleracea L. var. botrytis): the role of homeotic genes

Summary

Introduction

Cauliflower (Brassica oleracea L. var. botrytis) is a member of the genus Brassica in the family Brassicaceae. It is a major economic crop which is marketed as a large, white, pre-floral, compact curd. The cauliflower curd is, however, susceptible to a number of morphological defects which can seriously reduce its commercial value (King, 1990). The genetic determinants that control floral meristem development and flower morphogenesis in cauliflower have not been approached at the molecular level until recently. Medford, Elmer and Klee (1991) have now isolated and partially characterised a number of meristematic genes expressed in the immature cauliflower curd. In addition, Anthony, James and Jordan (1993) have isolated a homologue of the Antirrhinum flo gene (Coen et al., 1990) that is thought to be involved in regulating floral initiation.

In this review, we will briefly describe the morphology and physiology of the cauliflower, with particular emphasis on floral development. In addition, we will describe the isolation of genes involved in floral initiation and discuss how these genes may interact to control cauliflower morphology.

Morphology and physiology of cauliflower floral development

Five stages of development have been recognised between vegetative growth and flowering in cauliflower (Margara & David, 1978): 1. The vegetative stage in which the small pointed shoot apex is surrounded by leaf primordia. These arise acropetally in a spiral succession and axillary branches do not develop; 2. Initiation of inflorescence results in precocious formation of axillary buds at the apex to form clusters of meristems and bracts; 3.