XXIIIrd International Eucarpia symposium, Section Ornamentals ...

P13
Thomas Borchert
Katja Krueger
Annette Hohe
Leibniz-Institute of
Vegetables and
Ornamental Crops (IGZ),
Kuehnhaeuser Str. 101
99189 Erfurt, Germany
borchert@erfurt.igzev.de
FLOWER TYPES IN THE ORNAMENTAL CROP
CALLUNA VULGARIS – MORPHOLOGICAL
AND MOLECULAR INVESTIGATIONS
Calluna vulgaris is one of ~ 11,500 species in the Ericales family which display an
enormous diversity of flower types (Schönenberger et al. 2005). C. vulgaris itself
features several different flower types, one of which is the so-called ‘bud-flowering’
phenotype.
‘Wild-type’ flowers comprise four whorls of flower organs: one outer whorl of four
coloured leaves, an inner whorl of four coloured leaves that are slightly grown together,
eight stamens and four carpels. In contrast, ‘bud-flowering’ phenotypes display two
identical whorls of four coloured leaves each that are not grown together. Moreover, the
stamens are missing, which we assume to be at least one reason for the developmental
arrest in the bud stage. Since an investigation regarding the flower organ identity of C.
vulgaris (McClintock 1986) remained vague to the authors, we investigated the flower
morphology in depth and started first analyses on the molecular basis of flower organ
identity in C. vulgaris.
Histological analyses demonstrated the time-course of organ development in young
flower buds and revealed that in ‘bud flowering’ phenotypes stamens are not only
degenerated but totally missing. Scanning electron microscopy (SEM) was applied for
analyses of the cell surface structure of the coloured leaf whorls. Here, we were able to
identify differences of the cell structure between the two coloured leaf whorls of ‘wildtype’
flowers which is a strong hint to identify the outer whorl as sepals and the second
one as petals. Analogous analyses of these organs in ‘bud-flowering’ phenotypes
supports the hypothesis, that here both whorls of coloured leaves are to be classified as
sepals. Thus, in this flower phenotype, not only a loss of stamens has occurred but also
a change of organ identity in the second whorl.
Therefore, we are aiming at isolating MADS-box genes in C. vulgaris that might
control these changes in flower architecture. 3’-RACE-PCR was applied in order to
amplify MADS-box homologues from ‘wild-type’ mRNA in C. vulgaris. Until now, cloning
and sequencing of RACE fragments led to the identification of B-gene homologues
(DEF, GLO).
McClintock (1986) Acta Hort. 182:277-283
Schönenberger et al. (2005) Int. J. Plant Sci. 166(2):265-288
86 Session Posters