II.3. BRASSICA CROPS (BRASSICA SPP.) – 207
pattern variations were found at the intraspecific level among the Brassica diploids,
B. rapa, (two types), B. nigra (one type) and B. oleracea (two types), with the patterns of
B. rapa and B. oleracea resembling each other. The seed coat patterns in most of the
amphidiploids were intermediate to their putative parents, although one B. carinata and
one B. napus accession exhibited patterns of their respective B. nigra and B. rapa parents.
Thus, employing seed coat reticulations for species identification is not foolproof, but it
provides a good starting point to identify the adventitious presence of foreign species in
commercial seed lots.Figure 3.38. Distinguishing Brassica species by their seed coat characteristicsNotes: The small seeds shown in each compartment are about three times their natural size. The greatly enlarged surface detail
is not drawn to scale but a relative proportion is maintained throughout.
Source: USDA.
The fruit of major Brassica crops is a glabrous silique, which is 4-5 mm wide and can
be over 10 cm long, with 2 rows of seeds lying along the edges of the replum (false
septum, an outgrowth of the placenta). A silique normally contains 10-30 seeds. Three to
four weeks after the flower opens, the silique attains its full diameter and length.
When ripe, the silique has a tendency to dehisce and shatter, dispersing its seed.
Species and varieties differ in their susceptibility to shattering. The physical forces of
silique hitting silique or other plant parts causes a separation of the valve walls from the
placenta, starting at the pedicel end and working toward the unattached end. The exposed