Abstract

Although the flowering process in herbaceous species has been well characterized, the genetic, hormonal and environmental factors regulating flower development in fruit crop species are far from being elucidated. Grapevine (Vitis vinifera L.) is a woody plant belonging to the Core Eudicots, with significant agricultural importance. The reproductive cycle of this species has a number of unique features. In temperate regions, grapevines require two consecutive growing seasons to achieve the complete formation of a single inflorescence. At the beginning, a floral uncommitted primordium (UP) is activated inside the young bud of a rapidly growing shoot, just after the bloom of a current season's inflorescence. Here, flower meristem establishment occurs, but depending on the environmental and plant nutrient conditions of that first season, the UP may differentiate into either a flower cluster or a tendril. If floral initiation occurs within these buds, patterning of flower meristems will begin and will continue to develop in the following season`s spring. During organ formation, sepals develop to a small degree, while five petals grow and extend over the floral apex. These petals are interlocked at their margins forming a cap (calyptra) which will protect the inner whorls (stamens and carpels). Upon anthesis, flowers do not open at the tip of each cap. Instead, the calyptra becomes detached at the base and falls away in a process known as dehiscence (bloom). Pollination and fertilization usually occurs before bloom and each ovary in the inflorescence develops into a berry. The molecular events that control all of these processes in grapevine are not completely understood. Nevertheless, advances have been made in recent years in isolating and studying the expression of flowering time and flower patterning genes in this species. Some additional studies have addressed the involvement of these genes in somatic flower mutants. A recent update of these topics, together with advances in other genetic and environmental factors in the genetic control of flower development, will be discussed in this chapter.