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Silvae Genetica
ZEITSCHRIFT FDR FORSTGENETIK UND FORSTPFLANZENZDCHTUNG
JOURNAL OF FOREST GENETICS AND FOREST-TREE BREEDING
JOURNAL DE GENETIQUE ET D'AMELIORATION DES ARBRES FORESTIERS
The Austrian x Red Pine Hybrid
By W. B. Critchfield*)
D, Sauerlander's Verlag, Frankfurt a. M,
Silvae Genetica 12, Heft 6,181—212 (Nov.-Dez. 1963)
D 21809 F
continues the
Journal of Forest Genetics and
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P. Bouvarel,
R.Z. Callaham,
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H.Johnsson,
T. N. Khoshoo,
Station de Recherches et Experiences
forestieres, 14, rue Girardet, Nancy, France.
Institute of Forest Genetics, 1912 Carson Road,
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Southern Research Station, Maple, Ontario,
Canada.
Fdreningen Skogstrfidsfdrfidling,
Syd&stra Distriktet, Ekebo, Svaldv, Schweden.
Postgraduate Department of Botany,
Jammu and Kashmir University,
Naseem-Bagh, Sringar, India.
W. Langner,
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J. w. Wright,
continue le
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Bundesrepublik Deutschland.
Department of Forestry, University of Aber
deen, Old Aberdeen.
Faculty of Agriculture, Kyushu University,
Fukuoka, Japan.
Department of Forestry,
Michigan State University,
E. Lansing, Michigan, USA.
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© J. D. Sauerlander's Verlag, Frankfurt a. M., 1963
INHALTSVERZEICHNIS
Geographic and Individual Tree Variation in Some A New Method of Dealing With Results of Provenance
Wood Characters of Teak (Tectona grandis L f.). — Tests. By J. H. Wiersma 200
I. Fibre Length. By S. Kedharnath, V. J. Chacko, Berichte 206
5. K. Gupta and J. D. Matthews 181
The Austrian X Red Pine Hybrid. By W. B. Critchfield 187 Notlce 208
Acute Gamma Irradiation of Quercus Seed. — Its
Effect on Germination and Seedling Growth.
By G. R. Stairs 192
Ausgegeben im Januar 1964
The Austrian x Red Pine Hybrid
By W. B. Critchfield*)
(Received for publication May 22, 1963)
The genetic improvement of red pine (Pinus resinosa
Ait.) presents tree breeders with one of their most difficult
problems. Not only is this valuable species remarkably
uniform, .but until 1955 it resisted all attempts to cross it
with other pines. In that year red pine and Austrian pine
(P. nigra var. austriaca [Hoess] Aschers. & Graebn.) were
successfully crossed at the Institute of Forest Genetics,
Placerville, California. The few hybrid trees from this
cross have been .mentioned and illustrated by Duffield
and Snyder (1958) and Righter (1962).
This cross is the first successful hybridization between
hard pines of the Eastern and Western hemispheres. It is
also one of the few interspecific crosses in Pinus that has
been studied developmental^ (MeWilliam 1959), and we
know at what point the reproductive processes usually
break down. The hybrids may prove to be of economic
value in increasing red pine's resistance to its most serious
pest, the European pine shoot moth (Rhyacionia buoliana
[Schiff]). 'Finally, the hybrids are heterotic, greatly ex
ceeding either parent species in early height growth at
Placerville.
Austrian and red pines are grouped together in all
modern classifications of the pines. Shaw (1914) places
them in the Lariciones, a well defined group that includes
most of the hard pines of the Eastern Hemisphere. The only
Western Hemisphere members of this group are red pine,
a native of northeastern North America, and P. trppicalis
Morelet, a Cuban species.
Austrian pine, in contrast to red pine, has been success
fully crossed with several other species in the Lariciones.
The first authentic pine hybrid, produced by A. F. Blakes-
lee in 1914, was P. nigra X densiflora (Austin 1927). Aus
trian pine has since been crossed with P. sylvestris L. and
several East Asian species. These crosses and unsuccessful
attempts to cross Austrian pine are summarized by Wright
and Gabriel (1958).
The cross between Austrian and red pines has been tried
on a much larger scale than any other cross involving
either species (Johnson and Heimburger 1946; Duffield 1952;
Holst and Heimburger 1955; Wright and Gabriel 1958). Be
tween 1948 and 1955 Wright and his coworkers pollinated
*) Geneticist, Pacific Southwest Forest and Range Experiment
Station, P. O. Box 245, Berkeley 1, California.
more than 300 female strobili in attempts to make this
cross, using both species as female parents. Unsuccessful
attempts at the Institute of Forest Genetics since 1940 total
more than 30 tree X tree combinations and 500 female
strobili.
The developmental stage at which this cross fails has
been described by MeWilliam (1959). Ovules of Austrian
pine pollinated by red pine collapse toward the end of the
first season after pollination and at the beginning of the
second season. Breakdown of the ovule is initiated in the
megaspore and later in the developing female gametophyte.
MeWilliam found red pine pollen growing normally in
about 30 percent of the ovules of Austrian pine. These
ovules are the ilast to break down, and some of them remain
intact until seed coats are formed at about the time of
fertilization, early in the second season of development.
Production and Crossing of the Hybrids
The only successful cross of these two species was made
in May, 1955, between two trees growing in the Eddy
Arboretum at Placerville (table 1). The parents were a 30-
year-old Austrian pine of unknown origin and a 27-year-
old red pine from an 'unspecified Maine source. The cross
yielded 45 sound seed, 42 of which produced seedlings.
During their first growing season, the seedlings were not
readily distinguishable from their Austrian pine half-sibs
growing in adjacent rows (products of the P. nigra X nigra
cross listed in table 1). The following year F. I. Righter
singled out four seedlings as possible hybrids. His selection
was based on their marked superiority in height growth
and on the lighter green of their foliage compared to the
Austrian pine controls.
These putative hybrids were outplanted the following
spring (1959), together with their Austrian pine half-sibs
and unrelated red pines of Wisconsin origin. The out-
planted trees were watered only during their first season
in the field. Most of the Austrian pines had to be replaced
the following year, and nearly all of the red pines have
died since outplanting as a result of severe summer
droughts.
The majority of seedlings from this cross of P. nigra X
P. resinosa have proved to be nonhybrids. Of the eighteen
5-year-olds surviving in 1961, only six were probable hy-
187
Table 1. — Results of several controlled crosses involving P. nigra,
P. resinosa, and their hybrid.
Cross
Polli
nation
year
No.
of
stro—
bili
Per
cent
cones
Total
no.
seeds
per
cone
Per
cent
filled
seed
nigra (N7) X
resinosa (V29)1) 1955 25 60.0 12.3 24.32)
nigra (N7) X nigra
(2-tree mix) 1955 23 100.0 46.3 80.3
nigra (N7) X resinosa
(V29) 1959 146 67.8 22.2 0
nigra (4 trees) X 1955 and
resinosa (V29) 1959 66 43.9 3.7 0
nigra resinosa (11) X
resinosa (V29) 1960 6 100.0 17.7 0
') Numbers in parentheses are Institute of Forest Genetics tree
designations.
2) Includes both hybrids and non-hybrids.
brids — the four trees selected by Righter and two trees
remaining in the nursery. The others were indistinguish
able from the Austrian pine checks. This mixture of hy
brids and nonhybrids may be due to contamination at the
time of pollination, or it may be the result of cone or seed
mixing.
An attempt was made to repeat this cross in 1959, using
the same parent trees. Although the cross was made on a
much larger scale than the 1955 cross, no sound seed was
obtained (table 1).
In both 1955 and 1959 this tree X tree combination
produced a much higher set of hollow seed than other Aus
trian X red pine combinations tried at Placerville. The
high yield of hollow seed from this combination is a prop
erty of the Austrian pine used as female parent, since cros
ses of the red pine parent with several other Austrian pine
female parents yielded few hollow seed (table 1). According
to McWilliam (1959), the ovules of Austrian pine collapse
before the seed coat is formed unless the development of
red pine pollen tubes is normal and vigorous. Since this
particular Austrian pine parent yields many hollow seeeds,
its ovules must provide an unusually favorable environ
ment for the growth of red pine pollen up to the time of
seed coat formation.
The first attempt to backcross one of the hybrids to its
red pine parent was a failure. The backcross yielded no
sound seed and a rather low number of hollow seed (ta
ble 1). The backcross was repeated when the same tree and
one other flowered in 1961, with results not yet known.
Characteristics of the Hybrids
Austrian and red pines differ in many features, although
their general similarity caused some 19th centu.ry botanists
to class red pine as a variety of P. nigra (Shaw 1914, p. 51).
Not all of the differences between the two species could
be used in establishing the identity of the hybrids. Some
gross morphological features such as bud shape and leaf
orientation were too variable to be helpful. The conelet
and cone provide reliable distinctions, but only two hy
brids had flowered by 1961. For this reason we have relied
chiefly on the more stable features of needle structure in
establishing the hybrid identity of the nonflowering trees.
Many characteristics are influenced by tree age, and
comparisons of these features cannot usefully be made be
tween the hybrids and their much older parents. Conse
quently, we also compared the hybrids with related Aus
trian pines and unrelated red pines of the same age.
Conelets and Cones
The conelets of Austrian -and red pines are easy to dis
tinguish (figure 1). The scales of the Austrian pine conelet
are transversely ridged and armed with a small prickle.
Both features are pronounced in the Austrian pine parent.
The smaller conelet of red pine is unarmed, and the ex
posed face of the scale is slightly or not at all ridged. The
hybrid conelet is intermediate in size, and has obscure
prickles and inconspicuous ridges.
Figure 1. — Conelets of Austrian pine parent (left), hybrid (center),
and red pine parent.
The first hybrid to flower matured several cones in 1961.
They could be compared only with cones of the Austrian
pine parent, since the red pine parent rarely produces ma
ture cones and the young Austrian pine controls had not
yet begun to flower. The color of the hybrid cones is much
like the tawny yellow of Austrian pine cones and unlike
the nut brown of red pine cones. In cone size, however, the
hybrid is like red pine, which has cones 4 to 6 cm. long.
The cones of the hybrid, with a mean length of only 5.1 cm.,
are significantly smaller than cones of the Austrian pine
parent (mean length 7.0 cm.).
Time of Flowering and Cone Opening
Red pine flowers in late April at Placerville; Austrian
pine, 2 to 4 weeks later. When past dates of pollen collec
tion and maximum receptivity of female strobili are com
bined, the red pine parent averages 14 days earlier in
flowering time than the Austrian pine parent.
In 1960 the female strobili of the single flowering hybrid
reached maximum receptivity at the end of April, 12 days
after pollen shedding of its red pine parent and 9 days be
fore pollen shedding of the Austrian pine parent. The fol
lowing year, the female strobili of the two flowering hy
brids were at maximum receptivity 4 and 10 days after
pollen shedding of the red pine parent. Although these
dates are not fully comparable, they suggest that the hy
brids fall somewhere between the parents in flowering
time.
Red pine matures its cones several months before Aus
trian pine at Placerville. Cones of red pine regularly
open in the last half of September. Austrian pine cones re
main green throughout the fall, and do not ordinarily ripen
and begin to open until December or January.
In 1961 the cones of the hybrid were intermediate but
erratic in time of opening. By October 10, two of its six
cones had turned brown and the cone scales had begun to
separate. By November 1, when the cones were collected,
three cones had started to open. Not until two months later
did the cones of the Austrian pine parent tree begin to
open. •- '
188
Height Growth
Red pine does not grow nearly as well as Austrian pine
at Placerville. The red pine parent tree, one of the most
vigorous red pines in the Eddy Arboretum, was only 37 feet
tall in 1961 at 34 years. The Austrian pines used in the in
terspecific and check crosses were much taller: 52 to 54 feet
at 35 to 37 years.
The hybrids have grown faster from the start than either
parent species. By the end of their first growing season,
they were nearly twice the height of their Austrian pine
half-sibs and three times the height of the red pine checks
(table 2). They have maintained this superiority since out-
planting. At 5 years the hybrids were more than two and
one half times as tall as their Austrian pine relatives and
almost five times as tall as the two surviving red pines
(table 2).
The superiority of the hybrids in height at 5 years may
•be somewhat exaggerated. Four of the five outplanted
Austrian pines are replacements outplanted a year after
the hybrids. The trees they replaced had suffered severe
rabbit damage during their first winter in the field, while
the taller hybrids in an adjacent row suffered only minor
damage to their lower branches. The extra year the re
placements spent in the nursery may have affected total
height at 5 years, but is unlikely to have had much in
fluence on fifth-year increment. During their fifth growing
season (1961), the height growth of the hybrids was more
than double that of the Austrian pine checks (table 2).
The heterotic height growth of the hybrids may have
produced structural unbalance in some of the trees. In
these cases the rapid development of the crown appears to
have outstripped the ability of the trunk to support the
Table 2. — Early height growth of hybrids and parent species.
Species or hybrid
nigra (N7) X
resinosa (V29)
nigra (N7) X nigra
(2-tree mix)
resinosa (Wisconsin)
Number
of
trees
6.41)
53)
2
Mean ht.
at
6 months
0.28
2)
0.15
0.11
Mean 5th-
year ht.
increment
Feet
1.28
2)
0.51
0.43
Mean
ht.at
5 years
4.85
2)
1.77
1.01
') Six-month height includes all six hybrids; later measurements
include only the four outplanted trees.
!) Highly significant difference.
3) Includes one survivor of first outplanting and four replace
ments.
crown. These trees have developed pronounced leans and
had to be mechanically supported.
Leaves
The needles of Austrian and red pines differ in dimen
sions, texture, and structure. Two anatomical charac
teristics — the amount of hypoderm and the location of the
resin canals — have provided the most conclusive evidence
of hybrid identity, but several other leaf characteristics
have also proved to be useful.
Austrian pine has shorter and wider leaves than red pine
(table 3). In both species these dimensions are highly vari
able and affected by tree age, young trees having shorter
and narrower leaves than older ones (table 3). The leaves
of the hybrids are intermediate in length and width com
pared to Austrian and red pines of the same age. The dif
ferences between the hybrids and their Austrian pine sib
lings, however, are not statistically significant (table 3).
The leaves of Austrian pine are straight and stiff, and do
not break off when they are bent double. Red pine leaves
are flexible and break off cleanly when they are bent
double. The leaves of the hybrids are intermediate in stiff
ness. They often break off when they are bent double, but
the break is ragged compared to that of red pine.
This difference in texture reflects the great difference
between the two species in the abundance of thick-walled
cells within the leaf. The fragile needles of red pine have
one, or occasionally two, layers of relatively thin-walled
hypodermal cells. They have no fibers in the transfusion
tissue surrounding the vascular bundles, 'but the cells of
the endodermis have thickened outer walls (Harlow 1931).
The tougher needles of Austrian pine have a thicker epi
dermis, a much more extensive hypodermis, and a layer of
fibers in the transfusion tissue (figure 2; and Harlow 1931).
The hypodermis is usually three cell layers thick (occa
sionally two or four), and the cells of the inner layers are
very thick-walled (figure 3). The endodermis is uniformly
thin-walled.
The leaves of the hybrids are intermediate in some of
these anatomical features and resemble Austrian pine in
others. Both the epidermis and the hypodermis are inter
mediate, but the hybrids resemble Austrian pine in having
a layer of fibers in the transfusion tissue (figure 2). The
hybrids and the young red pine controls lack the thickened
outer endodermal walls of the red pine parent, suggesting
that this characteristic may be influenced by tree age.
Of these anatomical characteristics, the hypodermis is
the most useful in establishing hybrid identity. In the hy-
Table 3. — Leaf characteristics of hybrids and parent species').
Species or hybrid
nigra (N7)
nigra (N7) X nigra
(2-tree mix)
nigra (N7) X
resinosa (V29)
resinosa
(Wisconsin)
resinosa (V29)
No.
of
trees
1
4
5
2
1
Age
Years
37
5
5
5
34
Mean
length
Cm.
11.9
8.8
2)
10.1
12.1
12.7
Mean
width
Mm.
1.82
1.52
2)
1.40
1.32
1.39
No. resin
canals
per leaf
14.2
4.28
2)
3.78
2.0
5.3
Location of resin canals
Principal
Med.
100
100
83
5
5
Ext.
Accessory
Med.
Percent
0
0
17
95
95
100
98
57
0
73
Ext.
0
2
43
0
27
•) Based on. 10-leaf samples from vigorous primary branches. Observations on midportion
of leaves.
*) No significant difference.
189
dermal layersN
accessory resin^canaL
endodermis
.fibers
principal resin'canal
principal^resin canal
Figure 2. — Leaves of parent species and hybrid in transection. (A) 5-year-old Austrian pine
half-sib (Ni-50). (B) Austrian pine parent. (C) 5-year-old hybrid (NiRe-ll).(D) Red pine parent.
mesophyll
hypodermis
} epidermis
cuticle
Figure 3. — Dermal layers of the leaf in parent species and hybrid. Portion shown lies be
tween lines of stomata near the middle of the abaxial surface. (A) 5-year-old Austrian pine
half-sib (Ni-50). (B) Austrian pine parent. (C) 5-year-old hybrid (NiRe-11). (D) Red pine parent.
brids it usually consists of only two layers of cells. The
hybrid leaves lack the very thick-walled inner hypodermal
cells characteristic of the parent Austrian pine and the
young Austrian pine controls (figure 3).
Austrian and red pines have two principal resin canals
and a variable number of accessory canals in each leaf.
The principal canals are often larger than the accessories
and lie near the lateral margins of the needle (figure 2). The
distinction between the two kinds of resin canals is a
critical one, since the principal canals are relatively stable
in presence and position, whereas the accessory canals
often vary in number and position within a single leaf.
The principal canals of red pine are nearly always ex
ternal. In this position the sheath of cells surrounding the
resin canal is continuous with the hypodermis inside the
flat adaxial face of the needle (figure 2). Occasionally the
principal canals are medial (table 3). Accessory canals,
when they are present, may be either medial or external.
The red pine parent has predominantly medial accessory
canals (table 3).
The principal resin canals of Austrian pine are always
medial, and so are almost all of the accessory canals (ta
ble 3). In a total sample of 145 leaves from 12 trees of
varying ages, 97 percent of the accessory canals were me
dial, 2 percent internal, and less than 1 percent external. In
the Austrian pine parent all resin canals, both principal
and accessory, are medial (table 3).
The hybrids are extremely variable in resin canal loca
tion. Three trees can be distinguished from both parent
species solely iby the location of their principal canals,
which may be either medial or external. Unlike the ex
ternal canals of red pine, however, those of the hybrids are
always adjacent to the hypodermis of the convex abaxial
surface of the needle (figure 2). The external position is
rare in one tree and common in the other two.
Neither parent species ever has principal resin canals in
this location. They are never external in Austrian pine,
while in red pine they are always adjacent to the flat inner
face of the needle, never the rounded outer face. This re
markable feature, which sets off these hybrids from both
parent species, is rather common elsewhere in the Laricio-
nes group. The principal resin canals of P. sylvestris, P.
montana, and several other species characteristically oc
cupy this position (Shaw 1914; Harlow 1931).
Four of the hybrids, including the three above, can also
be distinguished from Austrian pine by the high proportion
of external accessory canals. The highest incidence of ex
ternal accessories observed in an individual Austrian pine
was 2 out of 43 in a 10-leaf sample. In the four hybrids, 50
to 70 percent of the accessories are external, the rest me
dial.
190
The remaining two hybrids are indistinguishable from
Austrian pine in resin canal location. The identification of
these trees, neither of which has flowered, rests on their
leaf dimensions and hypodermal characteristics.
Discussion
The few hybrid trees described here are the sole product
of many attempts to cross Austrian and red pines at Placer
ville and elsewhere, making this perhaps the most difficult
cross so far successfully attempted in Pinus. A further in
dication of the incompatibility barrier between the two
species is the failure of our first attempt to backcross one
of the hybrids to red pine. This failure was unexpected,
since most pine hybrids backcross fairly readily with their
parent species even when the parents themselves are dif
ficult to cross.
This failure, and our inability to repeat the cross be
tween Austrian and red pines, focuses attention on the
circumstances of the original cross. Its most noteworthy
feature was the mixed progeny resulting from it, mostly
Austrian pines with a minority of hybrids. We are inclined
to attribute the mixed progeny to contamination with Aus
trian pine pollen at the time of pollination, although the
possibility of later mixing cannot be eliminated.
Deliberate contamination with maternal-parent pollen to
improve the chances of success of a cross is a standard
technique of Michurinist tree breeding as practiced in the
U. S. S. R. (Forest Service 1961). The same technique has
been tried with unknown sucess in an interspecific pine
cross in Sweden (Johnsson 1956).
We think that an accidental admixture of Austrian pine
pollen may have been responsible for our isolated success
in crossing these two species. The structure of the female
gametophyte of Pinus provides a mechanism by which ma
ternal-parent pollen contamination might help in effecting
a difficult cross in this genus. Each gametophyte has sev
eral eggs available for fertilization, .but usually only one
of the resulting zygotes develops into a mature embryo
(Foster and Gifford 1959, p. 409). Austrian pine pollen, if
it were mixed with red pine pollen in amounts so small
that only a fraction of the available eggs could be ferti
lized, would prevent the collapse of the female gameto
phyte observed by MeWilliam (1959). Under these circum
stances the red pine pollen tubes which develop normally
in Austrian pine ovules might be able to continue their
development to the point of fertilization. The postem-
■bryonic vigor of the hybrids makes it unlikely that em
bryonic selection following fertilization would discriminate
heavily against the hybrid embryos.
On the basis of this hypothesis we repeated the cross in
the spring of 1962. The red pine pollen was deliberately
contaminated with small amounts of live Austrian pine
pollen. We also used red pine pollen diluted with large
amounts of dead or homogenized Austrian pine pollen, in
hopes that one of these combinations will enable us to re
produce this hybrid.
These hybrids, if they can eventually be backcrossed to
red pine, will provide the first opportunity to improve this
species by introducing genes from other species. This
source of genetic material is important to red pine because
of its apparent genetic uniformity (Buckman and Buchman
1962; Fowler 1962) and its serious insect pests. One of these,
the European pine tip moth (Rhyacionia buoliana [Schiff]),
is so damaging that it limits the use of red pine in parts of
the northeastern United States and eastern Canada (Holst
and Heimburger 1955; Wright and Gabriel 1958).
Austrian pine is less susceptible than red pine to shoot
moth damage (Holst and Heimburger 1955; Miller and
Heikkenen 1959). Backcrosses of the hybrid, or backcross
derivatives, might reduce the susceptibility of red pine in
two ways: (a) by introducing Austrian pine genes which
lessen susceptibility; and (b) by increasing the growth rate
of red pine, since faster growing red pine is less suscep
tible to tip moth damage (Heikkenen and Miller 1960).
These possibilities will be explored as the hybrids start to
flower more regularly and abundantly.
Summary
In 1955 Pinus nigra (Austrian pine) and P. resinosa (red
pine) were successfully crossed at the Institute of Forest
Genetics, Placerville, California. This cross is the first in
volving Eastern and Western hemisphere hard pines and
the first cross of red pine with any other species. An at
tempt to repeat the cross was unsuccessful. Our isolated
success may have been due to contamination with mater
nal-species pollen, and we are now trying to reproduce it
by using mixtures of pollen of the two parent species. The
six hybrids are intermediate between their parents in most
characteristics, but they greatly exceed either parent in
early height growth. In one feature, the location of the
principal resin canals in the leaves, some of the hybrids
are unlike either parent species but resemble other pines
in the Lariciones group. The hybrids may prove useful in
the transfer of genes between the two parent species, and
particularly in the introduction into red pine of genes af
fecting insect resistance.
Resume
Titre de l'article: L'hybride entre le Pin noir d'Autriche
et Pinus resinosa.
En 1955, on a croise avec succes a l'lnstitut de Genetique
Forestiere de Placerville (Californie) Pinus nigra (Pin noir
d'Autriche) et Pinus resinosa (red pine). Ce croisement est
le premier qui concerne 2 pins du sous-genre Eupinus,
Tun americain, Tautre eurasiatique, et egalement le pre
mier croisement de Pinus resinosa avec n'importe quelle
autre espece. Un essai de repeter ce croisement a abouti
a un echec. Notre succes isole a peut-etre ete du a une
contamination avec du pollen maternel et nous essayons
maintenant de la reproduire avec des melanges de pollen
des 2 especes parentes. Les 6 hybrides sont intermediaires
pour la plupart des caracteres entre les 2 parents, mais ils
depassent nettement Tun et l'autre en ce qui concerne la
croissance initiale en hauteur. Pour un caractere, la situa
tion des principaux canaux resiniferes dans les aiguilles,
certains hybrides ne ressemblent a aucun des parents, mais
ressemblent a d'autres pins du groupe Lariciones. Les hy
brides se reveleront peut-etre utiles pour transferer des
genes d'un des 2 parents a l'autre et en particulier pour
introduire dans le genome de Pinus resinosa des genes de
resistance aux insectes.
Zusammenfassung
Titel der Arbeit: Vber den Bastard Pinus nigra X Pinus
resinosa.
1955 wurden vom Institut fur Forstgenetik in Placer
ville (Californien) Pinus nigra (Schwarzkiefer) und Pinus
resinosa (Rotkiefer) erfolgreich gekreuzt. Diese Kreuzung
war die erste zwischen eurasischen und amerikanischen
191
Kiefern und die erste Artkreuzung mit Pinus resinosa
iiberhaupt. Eine Wiederholung der Herstellung des Bastar-
■des gelang nicht. Unser einmaliger Erfolg konnte durch
Vermischung mit Pollen der Mutterart hervorgerufen wor-
den sein, weshalb wir jetzt seine Reproduktion mit einer
Pollenmischung von beiden Elternarten versuchen. Die
sechs Bastarde sind in ihren meisten Merkmalen interme-
diar, sie iibertreffen aber jeden Elter wesentlich im frii-
hen Hohenwachstum. In einem Merkmal, ahnlich der Lage
der Hauptharzkanale in den Nadeln, unterscheiden sich
einige Bastarde von beiden Elternarten und ahneln ande-
ren Kiefern aus der Gruppe der Lariciones. Diese Bastar
de konnen sich als nutzlich erweisen bei der "Obertragung
von Genen zwischen den zwei Spezies, und besonders fur
die Einbringung von Genen fur Insektenresistenz in die
Pinus resinosa.
Literature Cited
Austin, L.: A new enterprise in forest tree breeding. Jour. For
estry 25: 928—953 (1927). — Buckman, R. E., and Buchman, R. G.: Red
pine plantation with 48 sources of seed shows little variation in
height at 27 years of age. Lake States Forest Exp. Sta. Tech.
Note 616, 2 pp. (1962). — Duffield, J. W.: Relationships and species
hybridization in the genus Pinus. Z. Forstgenetik 1: 93—97 (1952). —
Duffield, J. W., and Snyder, E. B.: Benefits from hybridizing
American forest tree species. Jour. Forestry 56: 809—815, illus.
(1958). — Forest Service: Forestry and forest industry in the
U. S. S. R. Report of a technical study group. U. S. Dept. Agric.
92 pp., illus. (1961). — Foster, A. S., and Gifford, E. M., Jr: Com
parative morphology of vascular plants. San Francisco: W. H.
Freeman & Co. 555 pp., illus.- (1959).-— Fowler, D. P.: Initial studies
indicate Pinus resinosa little affected by selfing. Proc. 9th North
east. Forest Tree Improvement Conference: 3—8. illus. (1962). —
Harlow, W. M.: The identification of the pines of the United
States, native and introduced, by needle structure. New York
State College of Forestry Tech. Bull 32, 21 pp. illus. (1931). —
Heikkenen, H. J., and Miller, W. E.: European pine shoot moth
damage as related to red pine growth. Lake States Forest Expt.
Sta. Paper 83, 12 pp. illus. (1960). — Holst, M., and Heimburger, C:
The breeding of hard pine types resistant to the European pine
shoot moth (Rhyacionia buolinna Schiff). Forestry Chron. 31: 162—
169 (1955). — Johnson, L. P. V., and Heimburger, C: Preliminary
report on interspecific hybridization in forest trees. Canad. Jour.
Res., Sect. C, 24: 308—312 (1946). — Johnsson, H.: (Annual report on
the activities of the Association for Forest Tree Breeding during
1955.) Arsberrat. Foren. Vaxtf. Skogstr. 1955: 3—18. (Swedish) (Plant
Breed. Abstr. 26: 3792) (1956). — McWilliam, J. R.: Interspecific
incompatibility in Pinus. Amer. Jour. Bot. 46: 425—433, illus. (1959).
— Miller, W. E., and Heikkenen, H. J.: The relative susceptibility
of eight pine species to European pine shoot moth attack in Michi
gan. Jour. Forestry 57: 912—914, illus. (1959). — Righter, F. I.: Evi
dence of hybrid vigor in forest trees. In: Tree Growth, ed. T. T.
Kozlowski, N. Y. Ronald Press, 345—355 pp., illus. (1962). — Shaw,
G. R.: The genus Pinus. Pub. Arnold Arboretum 5, 96 pp.. illus.
(1914). — Wright, J. W., and Gabriel, W. J.: Species hybridization
in the hard pines, series Sylvestres. Silvae Genet. 7: 109—115 (1958).
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