The Origin, Distribution and Classification of Cultivated Broccoli Varieties
Of the many different vegetable crops now under cultivation in both the U.S. and abroad, one that has gained increasing importance is that of broccoli. Although it does not constitute a significant portion of most people's diets, it has nevertheless experienced a kind of "revival" in recent years and has become increasingly popular (Schery, 1972; Heywood, 1978). It may even be said that broccoli has emerged from relative obscurity and attained the status of a worthwhile garden vegetable,"(Talbert, 1953).
The botanical family to which broccoli belongs is the Brassicaceae, also known as the Mustard family. The Brassicaceae is a large family comprised of approximately 3,000 described species apportioned among 350-380 genera. The precise number of genera will vary depending on the authority(Heywood, 1978; Keil & Walters, 1988). The classification scheme for broccoli and indeed all of the other brassicas is clear and straightforward until one reaches the species level. At that point the addition of numerous subspecies, varieties, and cultivars results in a rather complex and confusing arrangement of-the taxa in question. For example, the scientific name for broccoli, Brassica oleracea (L.), is also shared by cabbage, Chinese cabbage, cauliflower, collards, brussels sprouts, kale, kohlrabi, and tronchuda kale, to name a few. Despite the fact that all of the aforementioned varieties are similar to one another and to broccoli, and are therefore referred to as B. oleracea, they are nevertheless separate entities. Most authorities today consider there are two major varieties of broccoli, B. oleracea (L.) var. botrytis or cauliflower broccoli and B. oleracea (Plenck) var. italica or sprouting broccoli (Harlan, 1975; Terrell, 1977; Heywood, 1978; Keil & Walters, 1988).
At this point, it may be useful to consider some of the diagnostic morphological features which serve to delimit the B. oleracea group. Since many of these feature are "...highly characteristic and constant,"(Heywood, 1978), especially the floral structure, a consideration of these characters is best done at the generic level. In characterizing the genus, one necessarily characterizes all subsequent taxa. Most representatives of the genus Brassica are annual herbs, although there are also a few perennial species. The leaves are generally alternate on the stem, estipulate (without stipules), and glabrous (without hairs). Leaf shape is highly variable and may range from simple to lobed to divided (Heywood, 1978; Gomez-Campo, 1980; Keil & Walter, 1988). The inflorescence are generally either racemose or corymbose and are comprised of perfect and regular flowers. Furthermore, each flower has four distinct sepals and petals, the latter of which are so arranged so as to form a cross, giving the family its alternate name, Cruciferae. The ovary is superior and is comprised of two carpels. The stamens are six in...