The following is a brief extract from a subject discussed by
at the Region 2 Michigan City Symposium in 1993.
HYBRIDIZING WITH CONVERTED
TETRAPLOIDS - I
Text and drawings
by Oscie B. Whatley, Missouri
Converted tetraploids daylilies have been around for more
than 30 years, and the process of conversion continues unabated.
No characteristic in the diploid world is safe from the tetraploid
hybridizer's voracious appetite. As long as there are diploids
being hybridized, there will be conversions.
The common methods of treating daylilies with colchicine involve
treatment of seedling embryos, clones, and callus (in tissue
culture state). At the present time, clone treatment is the
most popular and it is dealing us some difficult problems in
If you are considering working with converted tets, you must
realize the importance of accurate identification so as to
concentrate your efforts where they will do the most good.
Naked-eyeball identification and trial crosses are not obsolete
but microscopic examination is essential for maximum efficiency.
Your time and good pod parents are not unlimited, and if you
use them unwisely, you may shortly wonder where the season
Even when sellers of conversions stand behind their products,
acquisition is a risky venture at best and no one can replace
time lost on worthless crosses.
Identification-Variations of Conversions
||#1: Stable 4/4 Periclinal Chimera
Description: High percentage of pollen is of
TET size and is proven viable. Stomata check
TET size. Divisions are true reproductions of
mother plant. Seedling shows parent characteristics.
Checked polyploidy for more than two years and all of its
|#2: Stable 2/4 Periclinal Chimera
Description: Same as above except stomata
NOTE: Only varieties #1 and #2 should be
considered marketable products.
#3: One-Shot Conversion 4/4 and 2/4
Description: First season, it checks similar to
#1 or #2 and can be used then. Subsequent
seasons, it probably will show little increase
and usually will revert to diploid after one or
|#4: Zebra Conversions - A True Mericlinal
Description: Scapes and flowers show both
TET and DIP characteristics; clumps may become mixtures
of TET and DIP ploidies. Zebras are usable in the hands
of those who
check ploidy prior to each use. Dividing is
recommended to isolate TETs, and after
checking their divisions, they may be reclassified as #1
or #2 if stable.
#5: Joker Conversions--4/2 and Sterile
Description: 4/2 may look TET except for the
pollen size. It is very difficult to use even
when some tet pollen is present. A few #1s and #2s can
be TET in every respect except for being very sterile;
some regain their viability after a few years. Don't discard
early; continue to re-check. Perhaps they can be reclassified
to #1 or #2 if they become usable.
The illustration (Fig. 1, above) that was used at the 1993
Region 2 Mid-Winter symposium is an attempt to categorize the
most common variations of conversions. There are undoubtedly
more variations than those shown here, but these are the ones
most often observed. The cartoons are not meant to replace
more technical names but only to enhance the recall of us older
You will note 90% of our conversions are erratic, reverting
back to dips, or totally unusable. Many of the convertors literally
snatch tet life from some of these plants at the opportune
moment. This opportunity is usually in the first season after
treatment and requires quick and accurate identification. After
the first year, such a plant is putting the purchaser
at high risk for successful crosses.
The remaining 10% are stable conversions that are identified
from close observation of the mother plant and its divisions
for at least two years. If they are found to be stable and
fertile, the purchaser is not taking any more risk than with
a second generation tet.
The convertors I know are sincere and respected hybridizers
trying to help others with new tet blood. Despite good intentions,
some plants will revert back to diploid, and you wonder who
is still checking as the resales spread out.
Wise purchasers of conversions should learn to do their own
identifications between the time of receiving and breeding
a plant. If this is not possible, then ask the seller and/or
convertor these questions.
1. Has the plant been converted for a period of two or more
2. Was the pollen size at least 40% larger than its dip counterpart?
3. Have pollen size checks been made over two or more seasons
at several flowering periods?
4. Do the seedlings from this conversion show obvious characteristics
of their daddy?
If the seller can answer yes (first hand) to all four questions,
then you can rest assured that every feasible effort has been
made to deliver a stable conversion.
Subsequent articles will deal with more information on identification
methods and hybridizing
with converted tetraploids.