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518 GoT mez-Campo et al.—Epicuticular Wax Columns in Brassica
B. oleracea (NC) B. montana (SC)
(Br, Ga, Hs) (Hs, Ga, It)
B. insularis (LC/SC) B. rupestris (LC)
(Co, Sa, Tn) (Si)
B. macrocarpa (SC) B. villosa (SC) B. incana (LC)
(Si) (Si) (Si, It, Ju)
(Tn)
F. 2. Scheme showing the geographic distribution of n l 9 Brassica species studied with indication of their respective wax types. Sicilian densely
hairy species are boxed. Arrows express hypothetical derivations. Abbreviations for countries and islands are as in Med-Check List (Greuter et
al., 1986) : An, Anatolia ; Br, British Isles ; Co, Corsica ; Cr, Crete ; Cy, Cyprus ; Ga, France (continental) ; Gr, Greece (cont.) ; Hs, Spain (cont.) ;
It, Italy (cont.) ; Sa, Sardinia ; Si, Sicily ; Tn, Tunisia ; Ju, former Yugoslavia.
Within each type of wax column, some minor differences
have been observed, for instance between Turkish and
Greek B. cretica or between the two populations of B.
incana studied.
Thus, lines c and d seem to be related to B. illosa while
line b (B. insularis) might have originally been of either LC
or SC type and later introgressed by an opposite stock. Line
a (B. rupestris) seems to be related to B. incana which, in
turn, is situated in the origin of line e. The phenetic and
phylogenetic reality of this line (e) across the coasts of Italy, reasonable to interpret them as a consequence of a massive
France, Spain and Great Britain seems reasonably well
established. Therefore, perhaps we should admit that SC
waxes of B. montana are also the result of introgression,
probably from an SC ancestor of B. insularis which also
provided glabrousness. The disruption of this line along the
east, south and west coasts of the Iberian Peninsula and
the new Atlantic habitat conditions—temperature, salinity,
etc.—may have somehow favoured the development of NC
waxes.
According to our results with other cultivated Brassica
species outside the n l 9 group, B. nigra (n l 8) has no
waxes while B. carinata (an amphidiploid between B. nigra
and B. oleracea) inherits the NC waxes of B. oleracea. In
turn, B. napus, an amphidiploid between B. rapa (syn. B.
campestris) and B. oleracea also has waxes of the NC type,
like its parent B. oleracea. The other parent, B. rapa, did not
present any type of wax, at least in the material we studied.
The same occurred with B. juncea.
Conn and Tewari (1989 b) reported the presence of waxes
in B. rapa. However, given the wide genetic diversity of this
cultivated species (where it is not uncommon to find
glaucousness in the upper leaves), we consider that this
apparent contradiction is just a reflection of variability.
Also, waxy (NC type) and waxless varieties can be found in
B. carinata (de Haro, pers. comm.). B. napus may show both
B. cretica (SC) B. hilarionis (SC)
(Gr, Cr, An) (Cy)
LC (Tewari and Skoropad, 1976 ; Conn and Tewari, 1989 b)
and NC waxes (our results). Although further confirmation
is required, we should mention here molecular studies by
Song and Osborn (1992) based on the RFLP pattern of cp
and mt DNAs provide evidence for multiple origins of B.
napus, suggesting that an ancestor similar to B. montana was
the cytoplasmic donor of many B. napus accessions.
At first sight, netted columns (NC) may appear to result
from branching, but after closer observation it is more
production of feeble wax columns where newly formed
columns push, lift, tilt and sometimes bend the older ones,
giving rise to the clumps and scraps, and finally producing
the appearance shown in Fig. 1 C. Secondary welding may
also be present, but this may also occur in other wax types.
Thus differences observed in different varieties of B. napus
and B. carinata might just be the result of different
quantitative balances between inheritance from B. oleracea
and from their second parent.
Future studies with additional populations, especially
those from Sicily, Corsica and South France, may provide
further details for the scheme described above.
LITERATURE CITED
Bodnaryk RP. 1992. Leaf epicuticular wax, an antixenotic factor in
Brassicaceae that affects the rate and pattern of feeding of flea
beetles, Phyllotreta cruciferae (Goeze). Canadian Journal of Plant
Science 72 : 1295–1303.
Bothmer von R, Gustafsson M, Snogerup S. 1995. Brassica sect. Brassica
(Brassicaceae). II. Inter- and intraspecific crosses with cultivars of
B. oleracea. Genetic Resources and Crop E olution 42 : 165–178.
Conn KL, Tewari JP. 1989 a. Interactions of epicuticular wax in
Canola. Mycological Research 93 : 240–242.
Conn KL, Tewari JP. 1989 b. Ultrastructure of epicuticular wax in
Canola. Zeitschrift fuW r Naturforschung 44c : 705–711.