Download On the interrelationships of certain species of

Ada Bot. Neeri
On
32(1/2), February 1983,
the
of
interrelationships
certain
II.
species
Experimental
crosses
H.J.W.
Genetisch
97-107.
p.
of
Petunia.
data:
between
different
taxa
Wijsman
Instituut, Kruislaan 318,1098 SM
Amsterdam
SUMMARY
In order to investigate taxonomic conclusions based
have
been crossed. Characters
parodii,
show
as
well
as
of P.
axillaris
quantitative inheritance,
s.l. In the
latter,
the deflexed
that both
species
will
1.
identifying hybrids
have
pedicel
inherited
P.
integrifolia
subspecies
inherits
several
as a
have been
in
crosses
dominant
alleles from
studies, 2n
=
14 taxa of Petunia
with P. axillaris
ssp. axillaris
ssp.
established.
P. axillaris
s.l.
character with
a common
Length
or
in
modifiers.
measures
integrifolia
P.
It is
argued
ancestor.
INTRODUCTION
Based
of P.
on
a
I have
study
(Lam.)
P. axillaris
flowering
ted,
herbarium
hybrida (Hook.) Vilmorin
and P. axillaris
lung
two
their
over
large
meet, localities show
may
point
to
may
actually
crossed
same
be the
in
paper, the
groups
There is
extremes
of
a
available
nature,
for
P.
purple-flowered
contact
trophoretic,
and
Both wild
(Stout 1952;
own
In the white-
parodii,
La
hybrids
of
uni-
mor-
region
where
character,
which
both
hybridiza-
subspecies
were
could be found.
integrifolia
is defined as
integrifolia,
between
in
constant
Plata
To determine whether
spp.
are
the first
comprising
inflata,
ssp.
two
and
and ssp.
they
seem
dine. In herbarium material this dine could be demon-
are
ecological
species
fairly
are
representatives
typical
(subspecies), viz.,
present paper reports
condition, respectively,
1982).
of the tube length
swarm.
species
Schinz & Thel-
non-overlapping difference
a
around the
strated for the main differentialcharacter, the
ation. The
(Wusman
subspecies
two
hybrid
geographic
ancestral
taxa, ssp. axillaris and ssp.
However,
whether characters
population
occidentalis.
occur
a
two
integrifolia (Hook.)
geographic overlap
the presence of
to see
In the
three
are
P.
differing except by
range.
they
tion
B.S.P.
not
shown that for the
names
of the flower tube. The
length
phology
the
allopatric
in herbarium material
in the
to
with
(s.l.)
either in
herbarium
upon
of P. axillaris
are
on
inspected,
as
data based
known
to
position
some crosses
be
well
on
as
living
diploid
unpublished observations).
of the
pedicel
in which tube
on
further
to
length
or
pollin-
pedicel
morphological,
material of the
and
after
possess
taxa
elec-
mentioned.
14 chromosomes
98
H.
2.
MATERIALS AND
2.1
Material
For
crosses,
dam,
were
W.
WIJSMAN
METHODS
inbred lines of the collection of the Institute of Genetics, Amsterof the different taxa
Representatives
used.
P. axillaris
J.
SI
s.s.:
from
(1954,
the
the lines;
were
Botanic
Royal
Gardens,
Kew).
(collected
S2
in the wild in
inbred since
Uruquay,
1958).
P. axillaris
P.
integrifolia
S7
parodii:
ssp.
Dr. K. C.
(from
S12
s.s.:
in
(collected
Sink, Michigan, 1977).
the
Grande do Sul, Brazil,
Porto
wild,
Rio
Alegre,
by courtesy
of Sr. K. Ha-
wild,
Pedrito,
gelund).
in
(collected
SI3
Grande do
the
Dom
Sul, Brazil, by courtesy
Rio
of Dr T. M.
Pedersen).
P.
integrifolia
S6
inflata:
ssp.
S10
(from
name
S14
of P.
km
more
inland)
specimen).
provided
not
from Porto
samples
were
with
the
Pedersen).
coast)
and Dom
very limited (the latter derive from
km inland from Dom
seeds, part
a
Pedrito
Pedrito),
of
(300
voucher herbarium
Dr Pedersen
which, however,
did
germinate.
SI and S7 have
stems
spreading
All P.
SI2
under the
Sink, Michigan,
of Dr T. M.
considerable number of
a
C.
Plantes,
S10).
violacea).
Alegre (near
Mburucuya (450
From
us
Dr K.
to
(from Mburucuya, Corrientes, Argentina, by
courtesy
seed
be identical
may
Stockholm).
d’Amelioration des
Station
(from
Dijon,
The
Botanic Gardens,
(from
S9
has
integrifolia
a
wall-side
fair
as
a
erect
an
around
lines
fertility;
curtain of
Tester lines of P.
a
aspect, S2 is
more
rozette-like,
with curved
up-going
main axis.
give
the
few seeds and
narrow
stems
big reddish-purple
hybrida
were
are
lie
best maintained by
flat,
or
may
hang
sib-mating.
down from
a
flowers.
from the stock
collection of the Institute of
Genetics.
Methods
2.2
Measurement of flower
P.
indicated in
fig.
the flowers
Colours
Chart
are:
of
(HCC)
length (in
P.
axillaris),
and of diameter of the
integrifolia),
I
a,
were
b,
c.
For
flower
measuring
the
of total
(in
length
both
of the flower
species)
diameter in
P.
were
taken
(in
as
integrifolia (fig-
lightly spread.
hybrids
were
described
according
to
the
Horticultural Colour
of the British Colour Council. The flower colour genes mentioned
An2, FI, Rt, and Hfl (Wiering
1974).
In short, these stand for the
following:
99
INTERRELATIONSHIPS OF PETUNIA SPECIES II
A
Fig.
1. A.
Tube
in
length
B
P. axillaris
s.l.;
B.
C
total flower
length
in
P.
integrifolia s.l.;
C.
diameter
of the flower.
An2 is
(flfl:
a
basis factor for colour (an2an2 is albino); FI stimulates flavonol synthesis
poor in
factors,
a
flavonols);
instead of malvidin
ing,
Rt is
corresponding
in the flower
limb, peonidin
dominancerelation is
Hfl
>
opment of the blue pollen
et
al.
(1981).
glucose phosphate
Fig.
2. Flowers
and the FI
of P.
hybrid
in
SI
into
hfl-l
>
colour:
Prx genes
ssp.
in the presence of other
a
hydroxylation
The allele
hfl.
An4 and Po
are
carried
SI
S7 in the middle to show
and Van
(right);
(chang-
weaker;
gives
peroxidase isoenzymes;
den
Berg
P. axillaris
the intermediate
is
the
yellow pollen
described in Van
out as
involved in
are
line
gene
genes involved in devel-
genotype an4an4popo
was
3-glucoside
hfl-l (or HfI*)
in the flower limb is much
(Wijsman
parodii.
is
with,
(rtrt: delphinidin
malvidin).
the effect
isomerase
axillaris
x
gene
the aglycon
1979). Electrophoresis
Berg & Wijsman
in
glycosidation
3-rutino-5-glucoside); Flfl
active in the flower tube, but
(Wiering
a
change
tube
ssp.
den
gpi
1982).
axillaris,
length.
line
S7
(left);
100
H.
3. Flower tube
Fig.
(ssp. axillaris)
3.
x
length (a)
S7
ratio
of tube
length
and limb
diameter
(b)
in
W.
WIJSMAN
the F2
of SI
(ssp, parodii).
RESULTS
3.1.
Inter-subspecific
The inbred lines
were
is
and the
J.
crossed. SI
the
carrying
pared
all
to
Jong,
preferred
electrophoretic
prxB (Van
to
Maizonnier &
assumed that it
giving
rise
to a
it
hybrids,
(de Jong,
In the
the
might
SI
F2
carry
the
that
only
x
mosome
hybrida
one
and
of the
prep.)
same
is,
Sink)
has
prxBl.
a
Com-
translocation
den
Berg, De
prxBl and, naively, it
as
was
S1, potentially
from studies of the meiosis
complement
for tube
segregation
case
in
short-tubed
hand,
many
an
x
characters
of these
can
are
follows the
Tobacco
long-tubed
unbiassed normal
polymeric
insignificant part
length (fig. 2).
length (fig. 3)
same
(East
pattern
1916). The
distribution, indicating that,
involved,
be located
on
and,
on
the
other,
the translocated chro-
segment.
differ
diagnostic
our
SI
chromosome complement
in the F2. As it
segregation
from
Uruquay) because SI
1982; Van
S7 has also
Because the diameters of the flower limb of ssp.
not
S2,
Berg & Wijsman
in
(ssp. parodii
peroxidases,
line
to
S7 has intermediate flower tube
the
an
(ssp.
S7
axillaris from
comm.).
classical
one
Kew)
axillaris
and
be concluded that S7 has, instead, the standard
range of variation resembles
on
S2
allele for
den
the
Petunia
from
to
Wijsman,
biassed
can
pers.
The FI
as
(ssp.
was
in
crosses
axillaris
inbred lines of P.
neighbouring
in
SI
significantly,
character
samples
in
ssp.
the
ratio
separating
axillaris
tube
length/limb
the parent
species
axillaris and ssp.
diameter
and
can
parodii
be used
do
as
identifying hybrids.
a
In
the ratio varied between 0.65 and 0.80, while in
INTERRELATIONSHIPS OF PETUNIA
4. Position
Fig.
ssp.
inflata
pedicel
as in
after
pollination(or wilting)
all lines of P.
of the flower. Left;
hybrida. Right: completely
deflexed
inflexed, P. integrifotia
pedicels
in P.
integrifolia
integrifolia (Porto Alegre population).
ssp.
ssp.
parodii
axillaris
(1979)
a
1.18 and
1.44. In the
hybrids
ratio between 0.85 and 1.15
colour markers
as
defined
Wiering
by
a
tester
lines. Of
particular
the ratio
only
was
have been studied in the inbred lines used
hybrida
When
between
one; but
Flower
P.
ofthe
(line SI0),
101
SPECIES II
interest is
(1974)
recessive,
flavonol is found
only
these
genotype
to
for the
(quercetine)
in small
with the
hybrids.
and Wiering
by crossing
the
dominant allele FI is present, much flavonol
when the gene is
overlaps
found in
quantity.
is
gene
FI.
but
found;
The
al.
et
different
presence
of the strongly fluorescent flavonols may be important for insects visiting the
flowers in the
evening;
1952). Though
parodii )
in
the flower
our
is of genotypeflfl.
in view of the
be of the moth-visited type (cf. Stout
seems to
lines of P. axillaris
Granting
s.s.
that the
FI has been
samples
postulated pollination by moths,
to
are
might
indicate that different
attracted with reproductive isolation
simple
mendeliantrait;
hybrids
as
a
result.
line S7
one
is
(ssp.
tempted,
correlate the presence of fla-
vonols with odour. The odour of S7 is sweet; in P. axillaris
absent. This in itself
found,
limited,
scent
s.s.
pollinating
insect
Odour does
not
is
virtually
species
inherit
are
as
a
of S7 with several non-odoriferous Petunia lines
102
H.
but in the F2 studied
odoriferous,
were
no
more
than
J.
W.
WIJSMAN
could be classified
25%
into that category.
No other consistent differences between ssp. axillaris and ssp.
be found. It has
material described
which has been
been
already
Steere
by
interpreted
that
reported
line
our
indicationfor
two
hybridization
in
could
parodii
contrast to
only
has
(original description)
as an
in
S7,
the
parodii
longer stamina,
nature
(Wusman
1982).
3.2.
Inter-subspecific
The deflexed
character
the
separating
pedicel stays
limb in ssp.
In
FI
an
(inflexed);
erect
of P.
is
Even
(1952).
out
SI3, i.e.,
the
same
It
was
next
to
impossible
gave rise
pollinated
to
The distribution of
may
inflexed
for
a
my
major
Biassed
to
plants
study
fully
gave
their
gene;
to
From the
not
in P.
herbarium
type, barely
few in
the
(Bianchi
here
ssp.
The few
from
genetic
genes
is
partial
lines
S12 and
inflata (from
con-
low
can
total
and
very few
own
length
polygenic
with herbarium data
non-fumigated
treatment. Even
49
Finally,
plants
a
some
inflexed P.
is
hybrida
sorts.
biassed mendeliansegregation
the
dominant deflexus allele.
can
in
general
unpublished observations).
of the flower has been measured. The
the ratio of greatest
length/
similar variational distribution as tube
inheritance is indicated
flowers than
greenhouse
nor
(fig.
because the
1943a)
back. On the other hand
isomorphic;
are
from the
herbarium
so,
Selfing
plants germinat-
form classes
over
(Mather
uniformly
we see a
integrifolia has larger
plants germinating
be obtained
numbers.
have been found. The latter class
allele
1961;
the absolute value obtained under
pared directly
the
Corrientes)
rule rather than exception in Petunia and
plants the
axillaris,
only
deflexed
comes
number,
over-presented
are
subspecies sampled
study,
of
plants
in
normally
fully
modifying
diameter is 1.0. The total length shows
length
that
as
provenance
much better results.
inflexed and
deflexed
certation
same
position
reported by
pedicel morphology.
interpretation is that
flowers of both
(or
then
few seeds and of these
plants, though
segregations
be ascribed
same
1982).
between different
crosses
normal F2. FI
a
even
have formed the basis for the
present
Therefore,
P. axillaris,
pedicel
indicating
in
Argentinian province
study
to
and
the involvement of
parental, completely
nearly
only,
different FI
5b) suggests
of the
the
the main
as
in
has been
same
formed,
growth. However,
SI4, i.e.,
as
capsules
cases
Crossing
could be
is
the
(S2),
of 90°. The
“knee”
(plants
s.s.
inflata (Wusman
ssp.
P. axillaris
x
as
is deflexed in the FI.
pedicel
certain
these in all
ed.
integrifolia
inflata where,
Brazilian province of Rio Grande dol Sul) and ssp.
populations
the
sistently
from
the
integrifolia
has been described
4. Moreover, the diameter of the flower
fig.
angle
at an
thick
a
so,
wilting
than in
greater
deflexion is the result of active
isolates of P.
see
Petunia
or
from ssp.
integrifolia (SI2)
intermediate; it stands
Stout
pollination
integrifolia
ssp.
integrifolia
in
crosses
after
pedicel
few seed
specimens)
inflata;
conditions should
with field
do
As
(fig. 5a).
ssp.
of
not
in
the
course
be
com-
measurements.
samples
not
the presence of several
collected in the wild
allow proper
population
peroxidase electrophoretic
INTERRELATIONSHIPS OF PETUNIA SPECIES
5.
Fig.
Flower diameter in
a.
FI,
F2.
ssp.
inflata).
and
IV
Table
b. Position
III
of the
(intermediatebetween
Genotypes
1,
from seed collected
with
integrifolia ssp. integrifolia
P.
classified
pedicel,
(intermediate,
more
or
III and
less at
as
I
right angle),
integrifolia ssp. inflata: parents,
P.
x
like
(deflexed
ssp.
and II
peroxidase isozyme
for the two
subspecies
of P.
inlegrifolia
integrifolia
ssp.
inflata
mobility
7).
It
can
A4A5
3
2
112
1
4
4
5
was
A2A5
is
subspecies
are
same
likely
and unknown in P.
Both
A2A4
demonstrated
be deduced that the
though their frequency
inflata
I and
like
III)
genes
prxA
and
of
prxB
plants
grown
prxB
A5A5
A5A5
alleles
(indexed
integrifolia.
prxA
prxA
ssp.
V
integrifolia),
(intermediate between
V),
to the
respect
in the wild
103
II
A1A2
A1A2
A2A2
A1A4
AIA4
2
4
4
24
11
(Van
den
to
prxA
taxa.
B2B3
B2B3
4
4
3
3
3
3
is
B2B2
B2B2
B2B4
B2B4
31
31
3
1981;
in both
occur
differ; the allele prxB4
lines
B3B3
Berg & Wijsman
four alleles of
hybrida
grassland
A4A4
A4A4
only
see
table
populations,
found in
ssp.
(Wijsman 1983).
The
population
of Dom Pedrito
originat-
ed from “dry rough grassland” (Pedersen, personal communication).
3.3.
Crosses
It has
already
counteracting
has
an
between
P.
integrifolia
and
been mentioned that P. axillaris
the deflexus
intermediate
character,
so
P.
that the FI P.
pedicel position (class
III
axillaris
seems
in
to
be rich
integrifolia
fig. 5b).
in modifiers
x
P. axillaris
Too few F2
plants
104
H.
have been
had
inspected
inflexed
nearly
As
explained by
4.
only
slightly
a
the action of the allele
original descrip-
most
normal
is “Petunia
s.s.
is
parodii
with ssp.
hybrid
“rhodamine” or
630,
or
smaller than
are
wider tube than
a
bit
garden
purple” (HCC
bluish than
more
which
“cyclamen” purple),
can
be
hfl-1 (see discussion).
DISCUSSION
In P.
the
axillaris,
of the
As
ssp.
to
to test
P.
in the field whether
from
has them inflexed
the
dine,
we
modifying
of
to
the
as
any
bly small,
km
well, they
but the
apart)
inflata
one
rather
more
ratio
be
separating
pedicel
after
inflata
P.
typical
crossing
than the
Stout
As far
species.
be
can
extremes
of
extremes
1952,
Sink
a
1981)
plants
only
species
a
has
a
side
as
1 have
no
of
mor-
series
to
significant
hybrida
between
line
regulatory
trophoretic mutations
are too
ssp.
integrifolia
mutations in
&
The alleles
Wijsman
plants
genes
is regretta-
capsules.
integrifolia populations
carry
are
from wild
km from
populations;
low. The allele prxB4 is
all other lines
species;
success.
inflata population (450
hybrida.
Berg
in the structural
two
definitely
between
as
difference between the
only, each;
At present Van den
the
of pollen
general. Therefore,
obtainedfrom about 15
the ssp.
and unknown in lines of P.
P.
of P.
incom-
equalled
intraspecific
products
intercross
readily
barrier
analysis
sown,
pooled
the numbers
not
in
limited chance of
involved in the F2
result of the seeds
There is
do
reproductive
limit
they
as
envisaged
integrifolia
and contrasted these
(Wijsman 1983).
linkages
are
(Mather 1943b,
and ssp.
within the
cross
Pedrito).
in
the
difference is found in flower
polygenic
presence of
quantitative comparison
in ssp.
In
1982).
a
must
of the difference is influenced by many
subspecies
barriers between
electrophoretic analysis
Dom
occur
similar
in the past
inflata
The number of
(300
a
of Petunia), while
species
axillaris) (Wijsman
that the
indicate the
not
to
P.
other
integrifolia having
P.
it
for the main character
postulated
a
involved.
are
factor action, promoting cross-fertilisation
the fact that ssp.
As
(like
reproductive
rather,
was
viz.,
Thus,
1.0.
barriers have been stressed and these sometimes have been
growth
does
most
means
reproduction just
tube
(like
crossability,
patibility
to
dine
presence of
be obtained,
can
subspecies
or
the
to
From the present report,
mendelian polymorphism.
simple
As
a
minor genes;
point
species.
hybrids
species
find that the expression
This
phology.
of
integrifolia, typical
ssp.
deflexed
flowering
of full
overlap
flower limb diameter of around
to
integrifolia,
inflata
as to
unequivocal recognition
of flower tube length
possible
and axillaris may in itself
well
zone as
criterion for
in flower tube length around Buenos Aires
geographic overlap
subspecies parodii
hybridization
a
has
with P. axillaris
hybrid
that of the
magenta (HCC 629
but
hybrida”,
The colour of the
632); by contrast,
genes involved. Several
postulated
hybrid
the
flower,
“Petunia violacea
petunias.
about the
look very much like the flowers in Hooker’s
they
s.s.;
more
say
W. WIJSMAN
pedicels.
the form of the
to
P. axillaris
tion of
to
J.
only
for
found
prxB3
and
prxA2
prxAl
and
prxB2
determining possible
populations
(in preparation).
and elec-
INTERRELATIONSHIPS OF
The
be
al.
et
both
hybrida cultivars,
colour in P.
le
Texnier,
the
same
as
In the
limb,
Hfl
the
1861
and
hfl
axillaris
to
from P. axillaris and
lit
widespread
are
alleles fl and
Recessive
rt.
of Ellesmere
the
(s.l.)
is
hfl-1
can
rt
P.
seems to
as
flower
a
Gloire de
of
from
Hfl
among
is known
=
Segrez,
Heaven).
In
for the dark-
hybrida. However,
allele
s.s.
(Wiering 1974;
the modern cultivar Rose
in
responsible;
the
limb
formed because the allele hfl-1 is only active in the tube.
is transformed
potential anthocyanin
one
stems
Rt. FI and
be found in P.
can
flavonol quercetin. The allele
present in only
in
(Countess
may be identical
faint colour is
a
P. axillaris
x
during cultivation; magenta ( rtrt)
since
coloured tubes of P.
only
bring
their recessive
are
hybrida
1908;
way
s.l.
integrifolia
P.
FI. and lit. FI
,
species
form mutation
originate
hybrid
the action of three main flower colour factors
1979): Hfl
integrifolia:
P.
105
SPECIES II
colour of the FI
purple
explained by
Wiering
PETUNIA
is
hfl-1
by
the factor FI into the
unknown in P.
practically
inbred line of the Institute of Genetics
it
hybrida;
(De Vlaming,
was
pers.
comm.).
The combination of Rt,
aglycon
pigments
Hooker’s
(Hfl-)
and
in
and,
figure (1837)
fact,
& Edwardes
M;
in the
text
hybrid
specimens
P.
FI,
integrifolia
s.l.
collected in the wild
of hybridization in nature, P.
bees,
of
P.
axillaris
by
a
hue.
purple
P. axillaris,
to
third colour. Mather
their W is
An2; but
gene
moths.
purple” (HCC32)
P. axillaris
x
(Wijsman 1982)
a
interpreted
P.
some
other
reliable character
as
integrifolia being pollinated by
(In Europe,
least
Absence of the colour from
s.s.
is
at
named.
not
lack
complete
visited by both
is
hybrida
a
bumble-bees and
groups
insects).
The
ease
factorial
with which the wild
be attributed
What
to
parodii
occurs
had “Petunia
narrow
integrifolia probably
P. axillaris has
cause
hybrida
highly
is
irregular,
as
axillaris
our
(1943)
mono-
to
but this
a
can
(s.s.)
line S7
of P.
seems
(flfl)
is
found that the
to
not
have
typical
hybrid
with
integrifolia,
species.
hybrid
would
not
but the form of the tube
In nature, the
taxa
parodii
met.
yellow pollen
the alleles linked in the
give
its colour. If P. axillaris of genotype
than in the latter
in
contrast
an4an4popo
linked genes
and
in others meiosis is normal.
It may be that
purple
never
recessive genotype
a
tion of the
P.
hybrids
called P.
purple”
to
1975; present study) points
in nature, the vivid bluish magenta colour of the
would be much more
of
(1943)
(Stout 1952).
differ much from the reddish
and
in certain
since Mather & Edwardes
integrifolia (s.s.)
flfl
(Sink
mutations;
Mather & Edwardes
crossed
are
genes
Meiosis
chromosome
concerned ssp. parodii
for all
species
for several
segregation
strong genetic similarity.
P.
as
the
to
blue
he shows
generation;
from a backcross
(an2an2)
postulated, though
I have considered the colour “Petunia
for the
as
limb
the
gives
that the colour differences result from genes W and
gene
are
the first
to
mentions white
their M is
differences
relate
not
leads in the
hybrids
The latter
quercetin.
and
( hfl-1 hfl-1 ) types
(1943) found
apparently,
monogenic
does
venation
light
and FI in the
Hfl,
malvidin
gpiB
parental
for
to
P.
integrifolia (blue pollen),
pollen
and An4 in
a
be-
colourfactors. The distribunumber of cultivars still has
situation; P. axillaris,
gpiB2B2a«4a«4;
P. inte-
106
H.
grifolia, gpiBI B\An4An4 (Wijsman & Van
both
share other
species
all P.
cally
above).
e.g., several
alleles,
Futhermore, prxF
lapB
or
inbred lines of P.
hybrida only (Wijsman 1983).
inheritancefrom a
to
behaves
as
flavonoid
Apart
an
of the wild
common
an2an2 albino mutant,
during cultivation;
for
In
no case
having
only
populabut
S10,
a
polymorphisms
hfl
or
wild
rt,
mentioned
hybrida
not
very few
point
may
to
allow
material there is
several
or
an
the genes
(for
Hfl, FI,
to be due to mutations
seem
evidence for the
no
mutations (albino); cf. Wier-
one
evidence has been found for the theoretical
=
14
I
Petunia
The albino
purple species split
refugia
ta/integrifolia.
between the
Around the
P. axillaris
about
translocation
by
before the artificial
occur,
may
into
but
series of
Sims
(as figured by
isolates
populations
(inflata)
integrifolia
1825)
history.
A
study
hybridization
s.s.
A detailed
study
can
of allelic jenzymes
temporal
be ascertained whether
therefore, likely
to
of chromosomes
with
based
a
meet
on
the
infla-
number of differences
more
coastal
populations.
Hooker
and these have been
1831)
and
transported
to
P.
hybrida.
by:
of P. axillaris:
subspecies
some
with the
same
programme of
alleles
be inherited from
as
with
they
in particular, by
types, and,
By sampling electrophoretic
but other differences like
originally
occidentalis and
(as figured by
occur,
between the
oc-
started.
species,
Where
(apparently
1982):
and the
for the above concept may be obtained
on
An
albino
one
having
crossing
Britain, where their hybridization and further selection gave rise
Support
hybrida
field study is needed for certification.
Wijsman
case, see
inland form
Rio de la Plata P.
a
and
subspecies.
two
geographic
two
a
into
split
of P.
possibility
the parents each would have
coloured,
one
species
The latter is
extreme
s.s.
brought
parents
into
in the P. axillaris
as
where
postulate the following evolutionary
species split
secondary intergradation
same
function -
been fixed in the
having
yellow pollen.
The
same
which could have been
-
Summarizing,
it
in
instance,
genes of the
two
curred and
c.
and
1974.
ing
a.
data from
S9
all other factors necessary
pairs
other types in P.
presence of recessive alleles
b.
(see
S2,
is the remarkable fact that P. axillaris
as
having
from recombination of allele
most
to
hand,
in the flower.
synthesis
An2, Po and An4)
2n
These
WIJSMAN
(l.c.), prxB2 (in practi-
S10
S9,
W.
On the other
grown; it is present in
species
ancestor,
1982).
alleles
in line
occurs
in any other line
plants
Berg
but also in lines S2,
hybrida cultivars,
tions studies
den
J.
are
electrophoretic
development.
really
shared
a common ancestor
both present wild
both
by
with the
mobility
In these
ways
species and,
same
number
species.
ACKNOWLEDGEMENTS
The
present
study required
particular,
I
moreover,
brought
plants
in
acknowledge
our
me
the
the
into
use
of
advices
contact
greenhouses himself.
living
and the
with
Sr
I
material
and
supply
of seed
K.
Hagelund,
thank
everyone
samples by
and
even
Dr
who
T. M.
undertook
provided
it.
In
Pedersen, who,
to
inspect
“his”
INTERRELATIONSHIPS OF PETUNIA
107
SPECIES II
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B. M.
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