Subject: Reference information on Indigofera sp. (Indigo)?

From: [email-masked] (WBLanier)
Date: 29 Aug 1995 01:22:34 -0400

I am interested in information and references about the culture of
Indigofera suffruticosa and other species of Indigo.

Specifically:
(1) General techniques to enhance germination;
(2) Pathogens which attack Indigofera sp.;
(3) Assays for indoxyl or other indigo precursors;
(4) The physiology of indigo biosynthesis;
(5) Harvest techniques of Indigofera sp.;
(6) Techniques for indigo extraction and purification; and,
(7) Crossing of different "species" of Indigofera.

So far, digging through biological and agricultural abstracts has not been
very helpful.  Likely this is because large-scale culture of I.
suffruticosa for indigo production has not been common for around a
century.

If you have any information, I would greatly appreciate a reply by e-mail
or news.
Wayne Lanier, PhD

---

From: [email-masked] (Ian B Staples)
Date: Sat, 2 Sep 1995 12:05:13 GMT

>(1) General techniques to enhance germination;

For small samples of seed I find treatment with conc. H2SO4 to
be very effective for breaking hardseededness.  Usually 10 to
15 mins immersion (as a slurry of seed plus acid) is okay.
Some very tough hard seeds may need 20 to 30 minutes, and those
which are barely hard at all will respond to only 3 to 5 min, to
ensure rapid even germination of the entire sample.

The acid *must* be very dry as even small amounts of previously
absorbed moisture reduce the effectiveness dramatically (check 
that the specific gravity is up near 1.83 g/ml, if it's below
1.82 things don't work well).  And be careful with this stuff!

Oh yes, and make sure the seed to be treated is very dry before 
you start too.

The slurry should be drained (small stainless steel kitchen
sieves are good) before washing as you need to get rid of as 
much acid as possible to make the operation a bit safer and keep 
the sample cooler (diluting H2SO4 is exothermic).  The draining 
time counts as treatment time. Wash in a *large* volume of water
and immerse the sample quickly.  Rinse well under running water.

>(6) Techniques for indigo extraction and purification; and,

Most of the literature I've seen relates to the toxicology of
_I. spicata_ (syn. _endecaphylla_) which at one time was
investigated as a potential sown pasture legume in the tropics,
but the problem of indospicine could not be overcome.
The one reference in Julia Morton's paper (_Economic Botany_
43(3): 314-327, 1989) that may interest you is pretty old:
Perkin, A.G. & Everist, A.E. (1918) "The natural organic
colouring matters." (Longmans, Green & Co., Bombay).

>(7) Crossing of different "species" of Indigofera.

I suspect many species are outcrossing naturally.  We have had
trouble with seed set in the glasshouse because the flowers
don't get tripped by insects in there.  In most cases the
plants I've tried are self-fertile, but the flowers need to
be tripped even for self-fertilisation.  They are easy to
"spring" manually.  Unfortunately, I can't recall if
_suffruticosa_ was one that gave us problems or not.  It
certainly set seed prolifically in the field nursery -- to the
extent that we became concerned about its weed potential.

Cheers,  Ian S.

-- 

Ian Staples                        E-mail : [email-masked]
c/- P.O. Box 1054 MAREEBA          Phone  : +61 (0)70 928 555 Home 924 847
Queensland Australia 4880            Fax  : +61 (0)70 923 593   "   "   "