colchicine used to improve vegetable crops

wparrott at uga.cc.uga.edu wparrott at uga.cc.uga.edu
Tue Jan 21 13:08:56 EST 1997


doug at nathan.allegany.com wrote:

>Hello,
>      I plan on treating Solanum sisymbriifolium (Litchi Tomato) seeds 
>with colchicine. I can imagine that this specific plant has been ignored 
>by major plant breeders but, I am interested it treating other edible 
>crops as well.

>      Could someone recommend any books or articles covering the use of 
>induced polyploid seedlings on food crops? 


There is a book out there that you may be able to find in a library,
especially that of a university.  It is:

Eigsti, O.J., 1955.  Colchicine in agriculture, medicine, biology and
chemistry.  Iowa State College Press, Ames Iowa

The book is remarkably current given its age.  The seedling process is
really inefficient, having about a 1% success rate.  This can be
improved upon by using vacuum infiltration for 5 minutes (2).  The
seedlings with doubled chromosome number are swollen and grow much
more slowly than the unaffected plants.

The use of colchicine to induce polyploids began in the 1937, spurred
on by the fact that tetraploid plants are more vigorous than their
diploid versions (eg, potato).  However, these advantages were seldom
obtained with colchicine doubled plants, which in addition to lacking
vigor, had very poor fertility (1)

By 1942, three criteria had been identified that helped identify the
species that would respond most successfully to tetraploidization (4).
These were:

1. low chromosome number
2. be allogamous
3. be grown primarily for their foliage or other vegetative part

Number 2 appears to be the most important criterion.  To this day, I
am not aware of any vegetables that have been polyploidized with
colchicine and have been commercially successful.  If anyone knows of
any examples, I would really appreciate hearing about them.
Polyploidized red clover has had limited success, as have several
ornamentals.

In more recent years, the poor performance of colchicine-induced
polyploids has been attributed to old fashioned inbreeding depression.
Raw tetraploids are as inbred as if they had been self-pollinated for
2-4 generations!  This problem can be overcome by resorting to the use
of doublecross (4 unrelated colchine doubled plants as parents) or
double doublecross hybrids (8 unrelated colchine doubled plants as
parents).  Techniques for polyploidization which use  meiotic mutants
and which bypass the inbreeding problem are available, but that is
another can of worms, especially if one does not have the necessary
mutants (1)

A fourth criterion for successful polyploidization has identified in
more recent times.  Namely, small chromosome size, to prevent
formation of multivalents at meiosis, or alternatively, the
preselection of parents that have only 1 crossover per chromosome
pair. (3)

In short, the potential for super vegetables via colchicine doubling
is still there, but a lot of legwork must be done to get to that
point.  Best of luck.



Refs:

1. Bingham, E.T. 1980. Maximizing heterozygosity in autopolyploids. p.
471-489. In: W.H. Lewis (ed.) Polyploidy:  Biological Relevance.
Plenum Press, New York. 

2.  Drobets, P.T., and T.M. Pestova.  1980.  Production of polyploids
of red clover using colchine in a rarefied atmosphere.  Tsitol. Genet.
14:27-31.

3.  Lavania, U.C.  1991.  Polyploid breeding:  Meiosis in the diploid
progenitor and its predictive value for fertility in the
autotetraploid.  Proc. Indian natn. Sci. Acad.  B57:17-24. 

4.  Levan, A.  1942.  Plant breeding by induction of polyploidy and
some results in clover.  Hereditas  28:245-246.








>                                                    Thank you,

>                                                    Douglas Sutton
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