154 – II.3. BRASSICA CROPS (BRASSICA SPP.)
cabbage, bok choy, pai-tsai, mizuna, Chinese mustard, broccoli raab and turnip),
B. oleracea (cabbage, broccoli, cauliflower, Brussels sprouts, kohlrabi, collards and kale),
Raphanus sativus (radish), Lepidium sativum (garden cress) and Nasturtium officinale
(watercress). The condiment crops include B. juncea (brown and oriental mustard),
Sinapis alba (yellow mustard), B. nigra (black mustard, but now little used), Armoracia
rusticana (horseradish) and Eutrena japonica (wasabi). There are a number of other
minor potherbs and salad vegetables. There are numerous weedy species, but those of
greatest interest with regard to cross-pollination with B. napus are Sinapis arvensis (wild
mustard or charlock), Raphanus raphanistrum (wild radish), B. rapa (wild or bird rape)
and Hirschfeldia incana (hoary mustard).
The genus Brassica is classified as follows:
Order Brassicales (= Cruciales)
Family Brassicaceae (= Cruciferae)
Tribe Brassiceae
Subtribe Brassicinae
Genus Brassica L.
The Brassicaceae family is comprised of 25 tribes with about an additional 5 under
study (Al-Shehbaz, Beilstein and Kellogg, 2006). The tribe Brassiceae, which contains
the genus Brassica and its wild relatives, is made up of 48 genera and approximately
240 species (Warwick and Hall, 2009). Warwick, Francis and Al-Shehbaz (2006) have
prepared a checklist and a current taxonomic database for the family on CD-ROM.
Also on CD-ROM are chromosome numbers from the literature for 68.6% of the genera
and 42.0% of the Brassicaceae species (Warwick and Al-Shebbaz, 2006; Warwick,
Francis and Gugel, 2009). The morphological traits that characterise the tribe are
conduplicate cotyledons (the radical enclosed by longitudinally folded cotyledons) and/or
transversely segmented fruits, that have seeds or rudimentary ovules in both segments
and, if present, only simple trichomes or hairs (Warwick and Hall, 2009). Modern
molecular studies have reinforced the monophlyetic origin of the tribe.
Taxonomic research on the tribe conducted by Schulz (1936; 1919) established the
basic classification that is followed today, although it has been modified and criticised
(Al-Shehbaz, 1984). Within the tribe, Schulz (1936; 1919) recognised ten subtribes, with
Gómez-Campo (1980) later recommending a reduction to nine. Of the nine subtribes,
three are of greatest relevance to those concerned with Brassica crops, namely:
Brassicinae, Moricandiinae and Raphaninae. Within these subtribes Brassica, Sinapis,
Diplotaxis, Erucastrum, Hirschfeldia, Eruca and Raphanus are of primary interest.
The association and relationships among species within these subtribes have been
studied cytogenetically, chemically and morphologically (reviewed by Prakash and
Hinata, 1980; Takahata and Hinata, 1986, 1983) without providing a clear separation of
the subtribes and their genera. Recent molecular, morphological and hybridisation data
give strong support for a rearrangement of the three subtribes into two clades, namely, the
Rapa/Oleracea and the Nigra lineages (see the section on “Centres of origin and
ancestors”, as well as Warwick and Hall [2009] and references therein). Such a division is
also referred to in some publications as the Brassica and Sinapis lineages. It is expected
that the realignment of the species from the three subtribes into the two clades will
eventually require renaming of many of the species involved.
