Artificial chromosome doubling in Narcissus and its implication for breeding Narcissus tazetta hybrids


North, C.

Acta Horticulturae 63: 61-163

1976


'Twin scale' portions of bulbs of Narcissus x poetaz cultivars (n = 17 or 24) were treated with 0.1% colchicine placed as a drop between the scale portions where they join the base plate. From 26 bulbs, 25 bulbils with double the chromosome number of the original cultivars were obtained, representing 3.8% of the total number of treated scales.

ARTIFICIAL
CHROMOSOME
DOUBLING
IN
NARCISSUS
AND
ITS
IMPLICATION
FOR
BREEDING
N.
TAZETTA
HYBRIDS
C.
North
Scottish
Horticultural
Research
Institute
Invergowrie
Dundee
Scotland
Abstract
'Twin
scale'
portions
of
bulbs
of
N
a
r
c
i
s
s
u
s
x
p
o
e
t
a
z
cultivars
(n
=
17
or
24)
were
treated
with
0.1%
colchicine
placed
as
a
drop
between
the
scale
portions
where
they
join
the
base
plate.
From
26
bulbs,
25
bulbils
with
double
the
chromosome
number
of
the
original
cultivars
were
obtained,
representing
3.8%
of
the
total
number
of
treated
scales.
Introduction
Species
of
the
genus
N
a
r
c
i
s
s
u
s,
which
has
been
extensively
studied
by
Fernandes
(1968),
fall
into
two
broad
cytological
groups,
those
with
a
basic
chromosome
number
of
7
and
those
with
10,
though
forms
of
the
latter
group
with
a
derived
11
occur.
Polyploids
of
most
species
are
rare
in
the
wild
but
common
in
N.bulbocodiu
m.
There
are
many
tetraploid
and
triploid
cultivated
varieties;
these
probably
having
been
selected
on
account
of
their
large
flower
size
by
comparison
with
diploids.
Artificial
chromosome
doubling
would
be
a
useful
tool
for
the
N
a
r
c
i
s s
u
s
breeder,
especially
to
regain
fertility
in
hybrids
between
the
7
and
10
chromosome
groups
and
also
to
produce
tetraploids
from
wild
diploids
for
crossing
with
the
large
range
of
cultivated
tetraploids
to
produce
fertile
hybrids
rather
than
near
sterile
triploids.
Until
recently
a
technique
for
chromosome
doubling
in
N
a
r
c
i
s
s
u
s
was
not
known
and
Bateman
(1963)
discuss-
ing
the
genetics
and
crossability
of
the
species
concludes:
'Unfortun-
ately
colchicine
seems
of
little
use
for
inducing
polyploidy
in
Narcissus'.
Seedlings
and
mature
bulbs
of
N
a
r
c
i
s s
u
s
are
unsuitable
material
for
colchicine
treatment
but
it
seemed
that
the
newly-devised
twin-scale
technique
(Tompsett,
1972)
might
lend
itself
to
a
convenient
method
for
colchicine
application.
Preliminary
test
A
preliminary
test
was
made
rather
late
in
the
season
in
February
1974
to
find
the
optimal
concentration
of
colchicine
solution.
Thirty
twin
scales
of
each
of
the
N
a
r
c
i
s
s
u
s
x
p
o
e
t
a
z
cultivars
Aspasia
and
St.
Keverne
were
treated
by
applying
with
a
hypodermic
syringe
a
drop
of
0.01
ml
of
solution
to
the
portion
of
base
plate
between
the
scale
portions.
After
eight
hours
the
scales
were
rinsed
in
distilled
water,
dipped
in
0.5%
benomyl,
allowed
to
dry
superfici-
ally
and
then
put
in
polythene
bags
containing
slightly
moist
sphag-
num.
The
bags
were
kept
at
23
°
C
and
the
scales
examined
10
weeks
later.
From
the
results
(Table
1)
it
was
decided
in
future
to
use
a
concentra-
tion
of
0.1%
colchicine.
Acta
Horticulturae
63,
1976
Floriculture,
breeding,
genetics
161
Table
1
-
Effect
of
different
concentrations
of
colchicine
solution
on
survival
of
Narcissus
twin
scales
10
wks
after
treatment
Sound
scales
Dead
scales
With
Without
Colchicine
bulbils
bulbils
Aspasia
0
13
12
5
0.05
9
10
11
0.10
6
7
17
0.20
3
o
27
St.
Keverne
0
14
6
10
0.05
11
5
14
0.10
8
12
10
0.20
1
2
27
Chromosome
doubling
The
following
October,
26
bulbs
of
12
'Poetaz'
cultivars
were
scaled
and
treated
with
0.1%
colchicine.
After
ten
weeks
scales
pro-
ducing
bulbils
were
potted
in
soil
compost
and
stood
in
an
unheated
frame.
Over
a
period
of
18
months
root
tips
were
examined
for
chromo-
some
number
using
root
tip
squashes
pretreated
in
paradichlorobenzene,
fixed
and
stained
in
aceto-orcein.
Cytological
examination
indicated
that
some
cultivars
had
only
one
genome
of
N.
p
o
e
t
i
c
u
s
(n
=
7)
and
one
of
N.
t
a
z
e
t
t
a
(n
=
10)
whereas
others
had
two
genomes
of
the
former
(Table
2)
a
situation
previously
noted
for
N
a
r
c
i
s
s
u
s
x
p
o
e
t
a
z
forms
by
Nagao
(1933)
and
Janaki-Ammal
and
Wylie
(1949).
Twenty-five
chromosome-
doubled
forms
with
34
or
48
chromosomes
were
produced
from
the
26
bulbs
representing
3.8%
of
the
treated
scales.
As
far
as
can
be
ascer-
tained
no
mixaploids
were
produced.
Assessing
ploidy
During
the
first
season
some
roots
are
produced
from
the
remaining
portion
of
base
plate
of
the
parent
bulb
so
that
the
first
root
tip
squashes
did
not
always
indicate
whether
doubling
had
occurred.
It
was
therefore
necessary
to
screen
the
material
with
further
squashes
during
the
second
season
of
growth.
However,
ploidy
can
also
be
ascer-
tained
by
measuring
stomata
size
and
for
this
purpose
a
rapid
technique
(North,
1956)
to
obtain
epidermal
imprints
was
used.
Stomata
size
is
well
correlated
with
ploidy
and
it
is
even
possible
to
distinguish
between
n
=
17
and
n
=
24
cultivars.
The
main
advantage
of
this
tech-
nique
is
that
it
can
be
applied
to
the
first
emerging
leaf,
which
always
comes
from
the
newly-produced
bulbil,
and
on
plants
growing
in
the
field
rather
than
those
confined
in
pots
for
the
purpose
of
having
roots
which
are
easily
accessible.
Future
plans
Pollen
size
measurements
of
the
twelve
N
a
r
c
i
s
s
u
s
x
p
o
e
t
a
z
cultivars
before
treatment
supported
the
general
observa-
tion
of
breeders
that
cultivars
of
this
cross
are
sterile.
The
162
chromosome
doubled
forms
cannot
be
tested
for
fertility
until
they
flower,
probably
in
1977.
In
the
meanwhile
it
is
planned
to
produce
tetraploid
N
a
r
c
i
s
s
u
s
x
p
o
e
t
a
z
forms
by
crossing
auto-
tetraploid
parents
in
the
hope
that
their
hybrids
will
be
fertile.
Some
N.
p
o
e
t
i
c
u
s
cultivars
were
screened
for
ploidy,
and
Actaea,
Dulcimer,
Mara,
Perdita
and
Stilton
were
found
to
be
tetraploid.
All
the
N.
t
a
z
e
t
t
a
forms
available
for
examination
were
triploids
and
a
search
is
now
being
made
for
diploid
forms
for
colchicine
treatments
to
produce
autotetraploids
to
cross
with
tetraploid
N.
p
o
e
t
i
c
u
s
cultivars.
Table
2
-
Effect
,
of
0.1%
colchicine
on
chromosome
doubling
of
12
Narcissus
cultivars
Cultivar
Chromosome
number
No.
of
No.
of
bulbils
scales
with
doubled
treated
chromosome
number
Aspasia
24
13
Cheerfulness
24
37
1
Crayford
17
80
9
Early
Splendour
17
180
4
Golden
Dawn
24
50
3
Geranium
17
90
5
Ideal
18
37
2
Kingcraft
24
29
Romeo
17
37
St.
Agnes
24
30
1
St.
Keverne
24
17
Yellow
Cheerfulness
24
52
References
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A.J.
(1963).
Genetics
of
Narcissus
II
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Crossing
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1964.
19:70-77.
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A.
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nature
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