2045
Inheritance of megastrobili colors in Douglas fir
(Pseudotsuga menziesii)
DONALD L. COPES
Forestry Sciences Laboratory, Pacific Northwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture, Corvallis, Oregon Received February 3, 1972
COPES, D. L. 1972. Inheritance of megastrobili colors in Douglas fir (Pse11dots11ga menziesii). Can. J.
Bot. 50: 2045-2048.
Megastrobili color was studied in 7- to 9-year-old progeny resulting from cross-pollinations of parents
with green, light pink, light red, or dark red megas_trobili. Crosses of green X green parents produced
49% green progeny, while crosses of light red X dark red parents produced only 7% green progeny.
Two bract traits, color of margins and tips and color of the central areas, combined to produce whole
megastrobili color. Both the central and margin-tip traits appear to be controlled by different multigenes.
An epistatic relationship was suggested between genes for central and margin areas.
COPES, D. L. 1972. Inheritance of megastrobili colors in Douglas fir (Pseudotsuga menziesii). Can. J.
Bot. 50: 2045-2048.
La couleur des megastrobiles a ete etudiee dans une progeniture de 7 ans a 9 ans, resultant de pollinisa­
tions croisees entre parents ayant des megastrobiles verts, rose pale, rouge clair, ou rouge fonce. Les
croisements vert X vert ont produit une progeniture de 49% d'individus ayant des megast1'0biles verts,
tandis que Jes croisements entre parents rouge clair et parents rouge fonce ant produit seulement 7%
de progeniture verte. Deux caracteres des bractees, la couleur de la marge et de l'extremite et la couleur
de la region centrale, produisent ensemble la couleur du megastrobile. Ces deux caracteres semblent
contr6les par des multigenes differents. II semble y avoir une relation epistatique entre Jes genes pour la
region centrale et Jes genes pour la region marginale.
[Traduit par le journal]
Introduction
Forest geneticists do not often have oppor­
tunities to study inheritance of traits with striking
color differences, but megastrobili, or female
"flower", color in Douglas fir is an exception.
Megastrobili range in color from bright red to
light or dark green. Colors vary between trees
but are uniform within a tree from year to year
(3). Exact color classification in the field is diffi­
cult because effects of environment, exposure to
direct sun rays, and the number of days since
the megastrobili scales and bracts emerged from
the protective cover of the bud, all influence the
intensity of color exhibited by the megastrobili,
but they do not cause major shifts from red to
green or green to red. Thus, some meaningful
color determinations can be made in the field.
Little is known of the inheritance of mega­
strobili color in Douglas fir or in other conifers.
A
study of megastrobili color variation and
frequency of occurrence in a small geographic
area in British Columbia was made for Douglas
fir (3). In Oregon, a study on pigments contrib­
uting to Douglas-fir megastrobili color revealed
11 flavonoid compounds in Douglas-fir mega­
strobili
(4).
One of the compounds, cyanidin-3­
monoglucoside, was found only in dark red
megastrobili. Megastrobili color frequency was
also examined in a natural Scots pine population,
and it appeared that flower color was controlled
by a single gene with two alleles
(1).
The fol­
lowing study examined megastrobili color in­
heritance in 395 progeny produced from crosses
of parents that had red, green, or intermediate­
colored megastrobili.
Materials and Methods
Controlled pollinations were made in 1962 and 1964
among 30 Douglas-fir clones in a grafted seed orchard
near Shelton, Washington. Geographic origin of parent
trees for the grafted orchard was the Soleduck area of the
Olympic Peninsula. The clones were crossed with intent
to study inheritance of various growth traits, hence are
probably a random selection for megastrobili color. By
cham:e, crosses of most color combinations of parents
were made. About 2400 progeny from 58 different
crosses were grown in cold frames and were field-planted
in the seed orchard in 1966 and 1968. In 1971, 395 of the
2400 progeny matured megastrobili.
Whole megastrobili color was determined only in
flowers which were in an upright receptive position with
bracts and scales fully open. This development stage cor­
responds to that labeled No. 2 by Griffith (3). Panmt and
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CANADIAN JOURNAL OF BOTANY.
progeny trees were classified on April 19 and 20 into one
of four broad color groups: green (G), light pink (LP),
light red (LR), and dark red (DR). The G, LP, LR, and
DR color classes correspond closely to the five bract
color classes previously illustrated by Griffith (3). His
classes 1 and 2 corresponded closely to G, 3 to LP, 4 to
LR, and 5 to DR. Although the G, LP, LR, and DR
grouping was an artificial classification system for a trait
with seemingly continuous variation, possibilities of
biasing the groupings in allotting borderline trees were
very low. The 30 parents separated into the four classes
as follows: 12 G, 10 LP, 6 LR, and 2 R.
A close examination of whole megastrobili revealed
that two bract traits combined to produce whole mega­
strobili color. The two traits were color of margin and
bract-tip areas and color of the central bract area. The
margin-tip areas impart most of the red color to the
megastrobili. In the field, it was not possible to evaluate
quickly the degree or intensity of color found in such
small areas of the bracts; to evade this problem, central
and margin areas were not separated into four classes
like whole megastrobili color but were simply classified
as green (G) or red (R) (red being any shade of red or
pink). Margin-tip and central areas were evaluated
separately to determine whether they were controlled by
different genes. The 30 parents were classified as 22 G
and 8 R for central areas, and 4 G and 26 R for margin­
tip areas.
Results
Whole megastrobili colors of the 395 progeny
are presented in Table 1. Crosses of GX G
produced 493 green and only 33 dark red
(DR); crosses of LRX DR produced only 73
G but 303 DR trees. A gradation or dilution
effect in percentage of G progeny (493, 253,
223, and 73 for G, LP, LR, and DR, respec­
tively) was noted when G parents were crossed
with parents having progressively more red pigTABLE 1
ments. Conversely, red parents crossed with
parents having progressively less red gave per­
centages in descending order of red (i.e., 303,
183, 63). Multiple comparisons by the Scheffe
5, 376) indicated
test (degrees of freedom (d.f.)
highly significant differences in the number of
green progeny arising from GX G vs. LRX
DR, and GX G vs. GX DR. Number of green
progeny from LRX DR vs. GX DR were
not significantly different.
Progeny results for bracts are presented in
Table 2. The same inheritance trends exhibited
for whole megastrobili color were shown in
central areas of the bracts. In general, crossing
GX G gave a majority of progeny with green
central areas (793), while crossing RX R gave
primarily pink red (643). Multiple comparisons
by the Scheffe test (d.f.
3, 391) showed highly
significant differences in number of green
progeny from GX G vs. RX R, GX R, and
RX G. No significance was found between
GX R and RX G.
A slightly different trend was shown for
margin-tip color (Table 2). Crosses of GX G
gave a majority of the seedlings which had pink­
red margins and bract tips (663). Although the
percentage of green progeny obtained from the
GX G crosses was only 343, Scheffe test com­
parisons (d.f.
3, 391) indicated highly signifi­
=
=
=
TABLE 2
Bract colors observed in (1) central area and in (2) margin
and tip areas of progeny resulting from crosses of parents
with green or pink-red pigments in areas 1 or 2. Results
are expressed as percentage of trees with green or red
megastrobili within each parentage
Whole megastrobili colors observed in progenies resulting
from crosses of green (G), light pink (LP), light red (LR),
and dark red (DR) parents. Results are expressed as
percentage of trees within each parentage that exhibited
the indicated color
Phenotypes
of parenta,b
No. of
progeny with
megastrobili, n
(1) Central area
Phenotypes of
progeny, 3
Phenotypes
of
parent
No. of
progeny
with megastrobili, n
G
LP
LR
DR
G X G
G X LP
G X LR
G X DR
LP X DR
LR X DR
39
81
45
11 1
79
27
49
25
22
7
8
7
31
49
31
41
39
22
18
25
29
45
35
41
3
1
18
6
18
30
--
VOL. 50, 1972
382a
0Sample size does not equal 395 because progeny from LP X LP,
LP X LR, and DR X DR were excluded because of inadequate
sample size.
G
G
R
R
X
X
X
X
G
R
G
R
103
148
92
52
Phenotypes of
progeny, %b
G
R
79
55
49
36
21
45
51
64
34
6
12
7
66
94
88
93
395
(2) Margin and tip areas
G X G
G X R
R X G
R X R
38
110
116
131
395
0Parent phenotypes were classified independently for both central
and marginAtip traits.
bGreen, G; red, R (red included all shades of pink and red).
COPES: INHERITANCE IN DOUGLAS FIR
cant differences when compared with
GX R
2047
margin-tip genes could be seen. It appeared that
(63), RX G (123), and RX R (73). Color
genes for green margin and tip were recessive
differences between G X R vs. RX G and G X
and did not have visible effect in margin and tip
R vs. RX R were not significant.
areas when the central areas were red. The sym­
metry of the data in Table 2 for central color
An apparently epistatic relationship was in­
dicated between central and margin-tip color
supports this conjecture.
genes. Green margins were never found where
When one considers that 11 different fiavonoid
central areas were pink-red, but both green and
compounds have been identified in Douglas-fir
pink-red margins were found in megastrobili
megastrobili ( 4), it is not surprising that a num­
with green centers (x2
70.96** for 1 d.f.).
ber of genes may be responsible for megastrobili
Progeny from crosses with one or two red
color in Douglas-fir. Like flower color in clover,
=
parents had only 63 to 123 with green margins
in which each fiavonoid is controlled by one or
and bract tips (Table 2). These lower than ex­
more genes (5), megastrobili color in Douglas
pected values resulted because about 503 of the
fir may depend quantitatively on the number of
progeny from the crosses had pink-red central
areas which masked gene expressions for green
fiavonoids present and upon their relative con­
centrations. This situation would fit the con­
margins.
tinuous range of color variation evident in the
Seven percent of the 30 parent clones from
northwest Washington were found to have dark
larger Douglas-fir families.
red megastrobili. The frequency of Douglas-fir
in hypocotyl color were found in progeny pro­
In a previous study (2), inherited differences
trees with dark or bright red megastrobili near
duced from crosses of parents with green and
Vancouver, British Columbia, was reported to
red megastrobili. Crosses between parents with
be 7.83 (3) and near Corvallis, Oregon (2), 63.
It appears that, at least for these three areas,
green megastrobili gave progeny with the fol­
lowing hypocotyl colors: 183 red, 323 pink,
there is little variation in the gene frequencies
for dark red megastrobili color (X2
0.23 for
close to megastrobili colors obtained in the
2 d.f., not significant).
present study from crosses of GX G parents
=
and 503 green. This color array was amazingly
(213 red, 313 pink, 49% green). Also, hypo­
Discussion
cotyl color of green X red crosses closely fit
No true-breeding (homozygous) combinations
megastrobili results for GX DR of this study
of parental genotypes were evident from study­
(483 vs. 513 red, 483 vs. 413 pink, and 53
ing megastrobili color of their offspring. Crosses
vs. 73 green). Hypocotyl pigmentation of 2­
between
green
week-old seedlings may be controlled by the
progeny and crosses between green parents gave
some dark red progeny. For Douglas fir, it ap­
two
red
parents
gave
some
same genes which control megastrobili color in
pears that a simple one- or two-gene model will
verify this relationship.
7- to 9-year-old trees. Further work is needed to
not adequately fit the observed data. The data
suggest multigenic control for whole megastrobili
color and for color of margin-tip and central
bract areas. Whole megastrobili color crosses
of GX G parents produced many more progeny
with green megastrobili than crosses of LRX
DR. Crosses made between green and red
parents tend to give a majority of the progeny
with intermediate-colored megastrobili.
A case of epistasis or variable penetrance was
suggested for the genes controlling margin-tip
color. Genes controlling the color of the central
area of the bracts also caused pigmentation of
cells in the margin area; thus, margin color genes
had to dominate or suppress the central trait
color in margin and tip areas before effects of
Acknowledgments
Gratitude is expressed to Tom Greathouse,
now with FAO in Turkey; Dr. Roy Silen, Pacific
Northwest Forest and Range Experiment Station
in Corvallis, Oregon; and to Virgil Allen of the
U.S. Forest Service, Shelton Ranger Station, in
Shelton, Washington. Each played a significant
role in pollinating and growing the plant mate­
rials examined in this study.
1. CARLISLE, A., and A. H. TEICH. 1970. The Hardy­
Weinburg law used to study inheritance of male
inflorescence color in a natural Scots pine population.
Can. J. Bot. 48(5): 997-998.
2. CHING, K. K., H. AFT, and T. HIGHLEY. 1966. Color
variation in strobili of Dou glas-fir. Proc. West. For.
Genet. Assoc. pp. 37-43.
2048 CANADIAN JOURNAL OF BOTANY.
3. GRIFFITH, B. 1968. Phenology, growth, and flower
and cone production of 154 Douglas-fir trees on the
University Research Forest as influenced by climate
and fertilizer, 1957-1967. Univ. B.C. Fae. For. Bull.
No. 6.
VOL. 50, 1972
4. HIGHLEY, T. L. 1964. The flavonoid compounds of
three floral phenotypes of Douglas-fir. M.S. Thesis,
Oregon State University, Corvallis, Ore.
5. TAYLOR, N. L., c. J. KELLER, M. K. ANDERSON, and
W. A. KENDALL. 1971. Anthocyanidin floral pigmen­
tation in red clover. J. Hered. 62(1): 13-15.