II.3. BRASSICA CROPS (BRASSICA SPP.) – 193
evolved and with increased leaf size and head forming, pekinensis, narinosa and
nipposinica were selected. Cultivation of the oilseed form in Europe as a source of lamp
oil is thought to have been under way by the 13th century, first as an annual form from
which the biennial form was selected (Appelqvist and Ohlson, 1972). In northern Europe,
turnip evolved from the biennial oilseed form through selection for bulbous roots
(McNaughton, 1995a). Cartier in 1540 is credited with the first introduction of turnips
into North America and more specifically to eastern Canada. They were also being grown
in the Virginia colony by 1609 (Sauer, 1993). Canadian commercial production of the
oilseed form began in 1943.
B. oleracea
B. oleracea has its centre of origin in the Mediterranean region (Snogerup, 1980).
The wild forms of the B. oleracea complex still grow along the coast of the
Mediterranean sea and Atlantic ocean from Greece to England (Figure 3.33). Snogerup,
Gustafsson and Von Bothmer (1990) concluded from morphological and crossing studies
among the wild B. oleracea forms, including B. oleracea, B. cretica Lam., B. bilarionis
Post., B. insularis Moris., B. villora Biv., B. incana Ten., B. macrocarpa Guss. and
B. montana Pourr., that these species should be considered subspecies of B. oleracea
along with the cultivated forms. These conclusions were confirmed by Von Bothmer,
Gustafsson and Snogerup (1995) through a crossing programme involving ten wild taxa
and six major cultivated forms. Snogerup, Gustafsson and Von Bothmer (1990) reported
that all wild forms of the B. oleracea complex were suffrutescent perennials, exhibiting
no primary dormancy. They are also self-compatible and readily intercross within the
group and with cultivated forms. They also identified some wild B. oleracea tetraploid
plants and reported a higher fertility rate in F 1 hybrids between the wild B. oleracea and
the cultivated forms than with the other wild subspecies.
Mutation, adaptation and selection within these populations yielded the present-day
forms of cabbage, savoy, kales, collard, broccoli, Brussels sprouts, cauliflower and
kohlrabi. The kales, several thousand years ago, were probably the first cultivated forms.
They were grown as early as 600 B.C. by the Greeks while ancient Roman writers
described heading cabbage and possibly kohlrabi (Thompson, 1976). De Candolle (1885)
suggested cabbage was first domesticated somewhere in Western Europe by the Celts
during the first millennium B.C. Support for this conclusion comes from the respective
English, German and French common names “cabbage”, “kopf or kohl” and “cabus”,
which are all probably derived from the Celtic word “cap” or “kap”, meaning head
(Prakash and Hinata, 1980). A number of authors have theorised, but lacked the research
to support their views, as to which species in the B. oleracea complex gave rise to the
various cultivated forms (Helm, 1963; Neutrofal, 1927; Schiemann, 1932; Schulz, 1936;
Lizgunova, 1959). After considerable investigation, Snogerup (1980) concluded that:
- headed cabbages originated from west European B. oleracea and savoy cabbage may
have resulted from introgression with other cole crops; 2) branched bush kales originated
from B. cretica in Greece; 3) stem kales probably arose from the rupestris-incana
complex; 4) the origin of the inflorescence kales such as cauliflower and broccoli is
uncertain although Schulz (1936) provided some evidence that B. cretica could be the
ancestor; and 5) B. alboglabra originated from B. cretica in Greece and was carried east
by traders. Today, B. oleracea var. alboglabra, or Chinese kale, is among the ten most
important market vegetables in Southeast Asia, including Thailand and China (Rakow,
2004). Little is known as to when forms of B. oleracea arrived in Asia but Schafer (1977)
noted that kohlrabi was being cultivated in Tang’ times (600-900 A.D.).