HYB: Anthocyanin pigments

Found on the Internet--an abstract with links to PDF files about pigments in
Gladiolus.  This information is about a genus closely related to iris, and
similar phenomena probably occur in Iris as occur in Gladiolus, the range of
pigments being similar but not exactly the same.

I'm posting this for those interested in highly technical stuff--and to raise
the question of how to get similar research going on IRIS pigments.  Who do we
have to talk to?

Neil Mogensen  z 7 near Asheville, NC

The URL for the abstract is:  http://www.actahort.org/books/177/177_53.htm

The following is the text of the abstract (typographical errors and all) with
links following for the full text of the article (the links do not work in
this copy).

ISHS Acta Horticulturae 177: IV International Symposium on Flower Bulbs
THE IDENTIFICATION OF ANTHOCYANIN PIGMENTS IN THE PETALS AS AN AID TO THE
BREEDING OF GLADIOLUS
Authors:    A. Cohen, N. Akavia, N. Umiel
Abstract:
Six anthocyanidins were identified in the petals of cultivated gladiolus using
HPLC and utilizing known anthocyanidin standards extracted from specific
plants.
These anthocyanidins (Pelargonidin, Cyanidin, Peonidin, Delphinidin, Petunidin
and Malvidin) can be divided into three groups based on the number of radicals
others than Hydrogen attached to the B ring. Two kinds of sugars are attaced
to the aglycon: glucose and rhamnose; and these could appear in four different
configurations giving a total of 24 pigmental variations.

Pigments of each group may appear individually or in conjunction with pigments
from either or both groups, all pigments contributing their share to the
visible color in the petals. Flowers having a single pigment in their petals
were also found.

The study of flower-pigment inheritance should consider (a) the genetic
factors responsible for the differences between groups (atleast two
biochemical steps are involved in the pathway determining the number of
hydroxyl residues on the B ring); (b) the substitution of OCH3 for the
hydroxyl (at the level of flavonoid precursors of anthocyanidins); and (c) the
different levels of glycosylation producing the anthocyanin pigments. At least
20 steps are recognized in the tentative biochemical pathway having
quantitative and qualitative impact on pigment content. The presence and
absence, and the relative amounts of specific pigments of each group, depend
on (1) biosynthetic blocks in the pathway, (2) the relative abundance of
precursors and/or (3) the differences in the efficiency of precursor
utilization brought about by their genetic state (e.g. heterozygosity level in
the tetraploid cultivars). All these factors affect the results of crosses
between selected parents. Specific parental clones containing a single pigment
produce offspring lines having no pigmental variation and little or no
difference in the visible color. This opens the possibility for F1 hybrid
production in gladiolus.

Full Text (PDF format, 329428 bytes)
Full Text e-mail service (PDF attachment, 1 494142 bytes)
Citation


Neil comments:  Pelargonidin is quite red, or can be, and we lack this
pigment, as well as Peonidin and Petunidin in Irises.  Gladiolus lack the
Violanin normative to Tall Bearded iris. I note that the abstract states " at
least 20 steps are recognized in the tentative biochemical pathway...,"
suggesting that our simple "B" gene is actually composed of  20 or more
chemical synthesis steps, each governed by a "gene".  In other words, our
color inheritance genetics is far more complex than we normally assume.  Am I
interpreting this correctly?

In order to access the "Full Text," etc., one will have to go to the URL
posted first on this page.

nam

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