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ABSTRACT

AUSTRIAN X JAPANESE RED PINE HYBRIDS: MORPHOLOGICAL FEATURES,

NATURAL DISTRIBUTION, AND YIELD FROM OPEN-PQLLINATED AUDTRIAN PINE

by David S. Canavera

Thirty-five natural Austrian pine (P. nigra Arn. var. austriaca)

X Japanese red pine (P. densiflora) hybrids were observed growing

 

within 20 feet of a 30—year-old Austrian pine stand located 200 feet
east of a similar-aged Japanese red pine stand at the W. K. Kellogg
Forest near Augusta, Michigan. Only seven pure Austrian pines were
growing next to the same.Austrian pine stand. Probable hybrids were
identified by red-brown buds and moderately stiff needles, in contrast
to Austrian pine which had white buds and very stiff needles. Probable
hybrids, six to eight years old, were significantly different from and
intermediate between similar-aged Austrian and Japanese red pines in
number of rows of stomata, number of Stomata per millimeter, bud size
and color. The probable hybrids have straight trunks, fine branches,
and are growing up to three feet per year.

Seeds from the open-pollinated Austrian pine, possibly pollinated
by Japanese red pine, were grown along with seeds of pure Austrian and
Japanese red pines to determine the percent of hybrids in the open-
pollinated Austrian pine. A hybrid yield as high as 85 percent was
found when two-year-old hybrids were compared to three-year-old pure
Austrian pines. The hybrids had a significantly lower value than the

comparison Austrian pine in needle length and width, total number of

David S. Canavera
stomata per millimeter, bud length and width, and bud color. The hybrids
averaged #5.9 centimeters tall, which was significant from Austrian pine
only 16.2 centimeters tall.

At the end of the first growing season, possible hybrids that were
_ germinated in the greenhouse and later transplanted to the nursery were
identified in the open-pollinated Austrian pine collected at the Kellogg
Forest. These seedlings had red-brown buds, secondary needles and
averaged 15.1 centimeters tall which was significantly different from
similarly treated seedlings of pure Austrian pine, with white buds, 11.8
centimeters tall and Japanese red pine, with red buds, 10.5 centimeters
tall.

Color differences of one-year-old open-pollinated seedlots, sown
directly in the nursery, show the hybrid yield to be 5n percent. A
seedlot of pure Japanese red pine was purple; a similarly treated seed-
lot of pure Austrian pine was green; at the same time two seedlots of
Austrian pine, possibly pollinated by Japanese red pine, had both purple
and green seedlings.

This unusually high yield of natural hybrids may result from the
suppression of archegonia fertilized with Austrian pine by superior
archegonia fertilized with Japanese red pine; equal amounts of Austrian
and Japanese red pine pollen in the Austrian pine stand; or identifi-
cation of the hybrids at ages one and two may be wrong.

Mass-production of the Austrian X Japanese red pine hybrids is best
accomplished by planting Japanese red pine around existing Austrian pine
stands. The wind will carry quantities of Japanese red pine pollen into
the Austrian pine, so that harvest of the hybrids will be possible ten

years after planting of the Japanese red pine.

AUSTRIAN X JAPANESE RED PINE HYBRIDS: MORPHOLOGICAL FEATURES,

NATURAL DISTRIBUTION, AND YIELD FROM OPEN-POLLINATED AUSTRIAN PINE

by

David S. Canavera

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Forestry

1967

ACKNOWLEDGEMENTS

My sincere gratitude is given to Dr. J. W. Wright (Forestry
Department, Michigan State University) who devoted considerable time
guiding and reviewing the methods of this study. Thanks are given to
the Michigan Department of Conservation who financed me while working
on this study. Finally I wish to thank those who gave of their time

in review and suggestions throughout the course of this study.

ii

TABLE OF CONTENTS

INTRODUCTION ..................................................
MATERIALS AND METHODS .........................................
Parental stands ..........................................
Natural reproduction near the parental stands ............
Test of open-pollinated progeny ..........................

Kellogg Forest measurements ..............................
Nursery measurements .....................................

Authenticity of the Kellogg hybrids ......................
Two-year-old nursery measurements ........................
One-year-old nursery measurements ........................
POSSIBLE EXPLANATIONS OF THE HIGH YIELD OF HYBRIDS ............
A POSSIBLE SEED ORCHARD SCHEME ................................

REFERENCES .... ................................................

iii

Table

 

LIST OF TABLES

 

 

 

 

 

Page
Seedlings at least two years old seeding into
the open area between the Austrian and Japanese
red pine stands ............................ . ............. 7
Cone and seed harvest from Kellogg Forest
Pinus nigra trees subject to pollination by
Pinus densiflora ......................................... 9
Seedlings available for study at the Tree
Research Center, Michigan State University ............... lO
Needle and bud characters of P. nigra,
P. densiflora, and their probable hybrids ................ 15
Cone and seed characters of Pinus nigra,
Pinus densiflora, and a probable hybrid .................. 17
Comparison of Austrian pine and probable
Austrian X Japanese red pine seedlings ............. ...... 20

iv

INTRODUCTION

VHybrids play an important role in the production of food.

Many are important because they exhibit heterosis or hybrid vigor
in the first generation. Tomatoes, corn, onions, and sorghum are
among the crops in which first-generation hybrids are planted
extensively.

Corn is the classical example of a useful hybrid exhibiting
heterosis. Beginning with the work of W. J. Beal at Michigan
Agricultural College in the late 1870's, hybrid corn was shown to
have more vigor than the Open-pollinated varieties then in use.
Although Beal did not give detailed data, he stated that hybrids
produced 25 percent higher yields than their parents (Wallace and
Brown, 1956). Actual development of hybrid varieties began much
later and large scale planting started three decades ago. Of the
total corn acreage in the United States, very little was planted to
hybrids in 1929; 23 percent in 1939; and at present the figure has
climbed to 99 percent. The acreage of corn in the United States
decreased from slightly over 100 million acres in 1929 to less than
80 million acres in 1963, but yield increased by one third (Gardner,
1963). The use of hybrids accounted for about one-third of this
increase. Improved agricultural practices, such as efficient weed
and disease control along with the application of prOper fertilizers

accounts for the remaining increase in production.

A potential tree that shows hybrid vigor is the eastern white

 

 

I
.
V
, o
y,
,
. ,

pine (P. strobus L.) X Himalayan white pine (P. griffithii McClel.)

 

 

hybrid. In a four-year test at Philadelphia, the hybrids grew 31
percent faster than eastern white pine and AA percent faster than
Himalayan white pine (Wright 1962).

In South Korea, pitch pine (P. rigida Mill.) x loblolly pine
(P. taeda L.) hybrids are very important. Impressed with the het-
erotic performance of this combination in California, S. K. Hyun
started a large scale hybridization program at Suwon, South Korea
in 1953. These hybrids are valuable because they are more productive
than pitch pine and hardier than loblolly pine (Hyun, 1956).

Hybrids often exhibit hybrid vigor, that is grow faster than
either parent. This can be regarded as the reverse of inbreeding
depression. Three hypotheses help explain the phenomenon. According
to the dominance theory, hybrid vigor results from the action of
dominant growth factors and the consequent suppression of deleterious
recessive genes. The overdominance theory states that heterozygosity
p§£_§§_is necessary, i.e. that two different genes at a locus can
accomplish more than two of any one gene. Thirdly, Edgar Anderson
postulated that the excellent growth of many hybrids was due to the
fact that they were grown in hybrid (intermediate) habitats.

Recently, several probable natural Austrian pine X Japanese red
pine hybrids were observed growing on the W. K. Kellogg Forest near
Augusta, Michigan. Their exceptional vigor made it desirable to
learn more of their characteristics and means by which they might be
mass-produced. My study was undertaken to confirm their hybridity and

growth potential, and to learn whether hybrids of this combination

could be mass-produced.

MATERIALS AND METHODS

Parental stands.--Austrian pine (P. nigra Arn. var. austriaca

 

(Hoess) Aschers & Graebn.) is an introduction from southern Europe
that has been planted extensively in the eastern half of the United
States. This variety has straight trunks, coarse branches, and A- inch
needles that are dark-green and very sharp. It attains a height of 70
feet and grows one to two feet per year.

An Austrian pine plantation was established at the W. K. Kellogg
Forest, 2 miles west of Augusta, Michigan on October 24, 1936. The
1000 seedlings of 2-0 stock were row planted by hand on a 7 X 7-foot
spacing, and occupied 1.1 acres. The first treatment given to the stand
was in 19A7, when a few trees were removed for use as Christmas trees.
In 1955, one-quarter of the remaining trees were removed with a crown
cut. Only potential crOp trees were left. In September 1966 the dom-
inant trees averaged A7 feet in height.

Japanese red pine occurs naturally between 300 and 3000 feet
elevation on the Japanese island of Honshu. It has fine brittle
branches, fine needles and is sometimes very crooked. In its natural
range this tree grows as much as two and one-half feet per year and
reaches a height of 105 feet.

A Japanese red pine plantation was established at the Kellogg
Forest on May 2 and May 9, 1936. The 2-2 stock came from the Michigan
State College nursery. The 2700 seedlings were row planted by hand

with a 6 X 6-foot or 6 X 8-foot spacing, and occupied 2.5 acres. The

5
only treatment given the stand was in 1952 when 10 percent of the trees
were cut and used as fence posts. The dominant trees averaged #5 feet
in height in September 1966.

These stands of Austrian pine and Japanese red pine are very close
together. They join on the south edge and radiate outward in an
east-west direction. The northern boundary marks their point of great-
est separation, here the Austrian pine is 200 feet east of the Japanese
red pine. The Austrian pine is growing on a level site and the Japan-
ese red pine is on a hill. Wind direction is from the south and south-
west in the spring of the year, therefore, as it passes through the
Japanese red pine it could easily pick up pollen and carry it east to

the Austrian pine stand.

Natural reproduction near the parental stands.--The probable
Austrian X Japanese red pine hybrids are seeding in naturally along
the north and west edges of the Austrian pine stand. The area is open

but the seedlings face competition from existing vegetation for nutri-

i' .11.,

ents and water.

Austrian pine, Japanese red pine, jack pine (P. banksiana Lamb.),

 

red pine (P. resinosa Ait.), pitch pine and Virginia pine (P. virginiana

 

 

 

Mill.) are also seeding into the open area between the Austrian and
Japanese red pine plantations. All of these species are growing north

or west of the Austrian pine and no more than 200 feet from it.

Natural reproduction for each has a limited distribution. Most seedlings
are found within 30 feet of their parental stands. The probable hybrids
extend 500 feet in a linear north-south direction, but all are found

within 20 feet of the Austrian pine stand. Natural reproduction of

6
Japanese red pine was abundant near the original Japanese red pine

stand, but no hybrids were found near this stand.

 

TABLE l--Seed1ings at least two years old seeding into the open

area between the Austrian and Japanese red pine stands

 

 

 

 

 

 

Species No. trees Percent of total
P. banksiana Lamb. 5 5
P. densiflora 32 3A
P. nigra 7 8
P. nigra X densiflora 35 37
P. resinosa A h
P. rigida Mill. 6 6 P

O\
O“.

P. virginiana

 

 

8

Test of open-pollinated progeny.--Cones from at least 10 Austrian

 

pine trees, subject to pollination by Japanese red pine, were col-
lected in each of three different years at the Kellogg Forest. The
cone and seed yields are given in Table 2. For comparison purposes,
seeds of supposedly non-hybrid Austrian pine were collected from two
sources and seed of non-hybrid Japanese red pine were obtained from
three sources in Japan.

Seedlings measured in the nursery resulted from seedlots sown
directly in nursery seedbeds or from seedlots sown in the greenhouse
and later transplanted to the nursery. Comparisons of the probable
hybrids with Austrian and Japanese red pine were made on seedlings

one to three years old (Table 3).

TABLE 2--Cone and seed harvest from Kellogg Forest Pinus nigra

 

trees subject to pollination by Pinus densiflora

 

 

 

 

Year of Seedlot Cones Filled seeds
collection numbers collected (Total) (Per cone)
Number Number Number
1962 3371 353 7300 21
1963 33V2 100 2100 20
196A 3955 to 3959 1716 u7000 27

 

 

-----

10

TABLE 3--Seed1ings available for study at the Tree Research Center,

Michigan State University

 

 

 

Species Year Seedlings Seedling
and seedlot S)urce sown measured density
MSFG number Number Number pgr

 

Sown directly in nursery seedbeds.

 

P. densiflora

39u5 to 39A? Japan 1966 600
P. nigra(a)
3371 3372 Kellogg 196A 50
955 to 3958 Kellogg 1966 200
P. nigra
3955 Yugoslavia 1965(b) 25
3951,3952 MSU Campus 1966 2CD

square foot

 

3O

30
30

0.5

30

Sown in greenhouse 1[l2/66 and transplanted to

 

nursery seedbeds 3125166.

 

.P. densiflogg

3955 Kellogg 1966 2a
P. nigra(a) Kellogg 1966 25
P. nigra

3951 3952 Yugoslavia 1966 25

1A

1A

1A

 

(a) Possibly pollinated by Pinus densiflora.

 

(b) Transplanted as 1-0 stock in 1965.

 

11

Kellogg Forest measurements.--Needle collections were made in

 

September 1966 from probable hybrids six to eight years old, from
comparison Austrian pine trees (Seedlot MSFG A23) in an eight-year-
old plantation (No. MSFG 5-61) about 1 mile distant, and from Japanese
red pine natural reproduction near the 30-year-old Japanese red pine
parent stand. Four needles, each from a different fascicle, were
measured from each tree. All measurements were made in the laboratory
with a dissecting micros00pe. Lengths were measured to the nearest
millimeter and widths to the nearest tenth of a millimeter. ventral
stomata in the complete rows of a l-centimeter section were counted
for each needle. Each section used was 3-centimeters from the tip

of the needle.

Bud measurements were made on terminal buds collected from the
largest branch in the 1965 whorl. All measurements were made in the
field except for color, which was made in the laboratory under fluor-
escent light. Color was scored on a scale of 1 to 9. Using the
Munsell Color Charts For Plant Tissues (1963), grade 1 corresponded to
Hue 7.5 YR (Value 8/Chroma 2), and grade 9 corresponded to Hue 10 R
(Value A/Chroma A).

Four mature cones were collected from the one l2-year-old probable
hybrid which fruited in 1966. Four cones were also collected from
ten trees each of the 30-year-old Austrian anquapanese red pines.
Cone length and width were measured to the nearest millimeter. The
cones were then air dried at room temperature. Time of cone opening
and duration of opening were recorded to the nearest day. Width of the

five largest scales per cone was measured to the nearest millimeter.

 

12
The total number of scales per cone were also counted.
Seed and seed-wing measurements were made on 25 seeds each of
the probable hybrid, Austrian and Japanese red pines.

Nursery measurements.--Probab1e hybrids were identified in the

 

open-pollinated seedlots of Austrian pine collected at the Kellogg
Forest. The seedlings labeled as probable hybrids all had brown buds,
grew rapidly, had three needle fascicles, and moderately stiff needles.
By contrast, Austrian pine seedlings had white buds, very stiff need-
les and were only about one-third as tall as the suspected hybrids.
Needles and buds were measured in the same manner used for material

collected from the Kellogg Forest. In addition to these measurements,
height of the various-aged seedlings was measured to the nearest centi-

meter.

RESULTS

Authenticity of the Kellogg Hybrids.--Austrian X Japanese red pine
hybrids have been reported previously by Blakeslee (Austin, 1927),
Wright and Gabriel (1958), Mergen (1959), and Vidakovic (1966). Austin
gives only a brief mention of the pioneer work done by Dr. A. F. Blake-
slee at Cold Springs Harbor, New York in 191A.

Wright and Gabriel successfully made controlled pollinations at
Philadelphia from 19A8 to 1956. They pollinated 385 Austrian pine stro-
bili; had A0 percent cone set; 5.0 empty seeds per cone and 5.9 full
seeds per cone. One-year-old seedlings showed heterosis. Also, prob-
able natural hybrids were identified in four open-pollinated progenies
of isolated Austrian pine trees grOwing close to Japanese red pine.

Mergen verified the hybrids made by Wright and Gabriel by counting
the number of rows of stomata and the total number of stomata per milli-
meter. By this method, he was able to show that the hybrids were inter-
mediate between Austrian and Japanese red pine.

The cross was most recently made by Vidakovic in Yugoslavia. He
found the needle structure of the hybrid to be intermediate in the pos-

ition of the resin ducts and the width of the cross section. More

 

interesting, the rate of growth of two-year-old hybrids was dependent
on the female parent used. The hybrids did not always display a greater
height growth than pure P. nigra.

Needle measurements made from collections at the Kellogg Forest

showed that the probable hybrids were significantly different from and

13

14
intermediate between Austrian and Japanese red pine in rows of stomata
and number of stomata per millimeter. These results agree with Mergen's
and give a sound basis for saying that the probable hybrids are indeed
Austrian X Japanese red pine hybrids (Table A).

The buds, cones, and seeds help confirm hybridity. Buds of the
probable hybrids were nearly as long as those of Austrian pine, but
intermediate in thickness and color. Austrian pine buds were longer,
thicker, and lighter in color than Japanese red pine. Width and color
of the probable hybrids were significantly different from both Austrian
and Japanese red pine.

Trees initially identified as probable hybrids had needles inter-
mediate in stiffness between the fine needles of Japanese red pine and
the stiff needles of Austrian pine, and also had red-brown buds.

Their buds closely resembled the red buds of Japanese red pine, but
were distinctly different from the white buds of Austrian pine. All

of these trees were growing within 30 feet of the parental Austrian
pine stand. The most questionable hybrid had needles almost as stiff
as the finest needles found on the Austrian pine trees, but it also had
red-brown buds, which were easily distinguishable from the white buds
of Austrian pine. Therefore, all of the trees designated as probable
hybrids differed from Austrian pine in at least one readily observable

character.

15

TABLE A--Needle and bud characters of P. nigra, P. densiflora, and

 

their probable hybrids (a)

 

 

 

 

Character and unit Probable
of measurement P. nigra hybrids P. densiflora
NEEDLE
Length(mm.) 106* 90 98*
Width(mm.) l.uu 1.20 0.97
Rows of stomata(no.) 8.0* 6.5 5.5*
Stomata per mm.(no.) 9H* 79 65*
BUD
Length(mm.) 15.9* 12.2 11.8
Width(mm.) 5.3* u.u 3.0*
Color Tan* Brown Red-brown*

 

* Differs significantly (5 percent level) from the probable hybrids.
(a) The measurements were made on 25 trees varying in age from 6
to 12 years. The measurements of the parents were made on twenty-five

similar-aged trees of each species.

16

The four cones collected from the one l2-year-old probable hybrid
were also significantly different from and intermediate between.Aus-
trian and Japanese red pine in length, width, and width of the scales.
In addition, their opening date was intermediate between those of
Austrian and Japanese red pines.

The medium-brown seeds of the probable hybrids resembled the
dark-brown seeds of Austrian pine more than the red-brown seeds of
Japanese red pine. Seeds of the probable hybrids were significantly
different from and intermediate between both Austrian and Japanese red

pine in color (Table 5).

17

TABLE 5--Cone and seed characters of Pinus nigra, Pinus densiflora,

 

and a probable hybrid

 

 

 

 

 

Character and unit Probable
of measurement P. nigra hybrid P. densiflora
CONE
Length(mm.) 72* 55 A2*
Width(mm.) 32* 25 21*
Scale width(mm.) 13* 11 9*
Scales per cone(no.) 93* 76 80*
Date Opening started Oct. 20 Oct. 17 Oct. 9
Days needed to open A 5 2 12
SEED
Length(mm.) 22.3 21.6 16.8*
Color Dark-brown* Brown Red-brownf
BASIS
Number of trees 10 1 10
Age of trees 3O 12 3O

 

* Differs significantly (5 percent level) from the hybrid cones or

seeds.

18

The possibility of Austrian pine successfully crossing with any of
the other hard pines near the Austrian pine plantation was considered.
The only successful combination of Austrian pine with any of these
hard pines is P. nigra X resinosa. Six of these hybrids were obtained
at Placerville in 1957 (Critchfield, 1963). Three hundred and twenty-
six P. nigra strobili were pollinated with P. resinosa before the six
hybrids were obtained. Many other attempts to make this cross were
unsuccessful (Johnson and Heimburger, 19A6; Duffield, 1952; Holst and
Heimburger, 1955; Wright and Gabriel 1958).

The extreme difficulty of obtaining inter-series crosses in the
pines eliminates the possibility of P. nigra combining with P. bank-

siana, rigida or virginiana. Natural P. nigra X sylvestris (Scotch

 

 

pine) hybrids have been reported by Vidakovic in Denmark (Vidakovic,
1958). No Scotch pine is growing less than one-quarter mile from the
parent Austrian pine stand at Kellogg, so possibility of this cross

was slight. Considering the distribution of natural reproduction, with
respect to parental stands, in the open area between the Austrian and
Japanese red pine stands; plus the convincing results obtained from
the comparison of Austrian and Japanese red pine with the probable
hybrids in needle, bud, cone and seed characters would all combine to
verify the Austrian X Japanese red pine hybrids.

The Austrian X Japanese red pine hybrids appear to combine the
favorable growth characteristics of both Austrian and Japanese red pine.
{They have the characteristic straight stems of Austrian pine and fine
'branches of Japanese red pine. The hybrids are also very fast growing.
TThe present growth rate is two and one-half to three feet per year.

CDne 22-year-old hybrid will soon surpass 30-year-old Austrian pine trees

19
located just 10 feet from it.

Two-year-old nursery measurements.--A comparison was made between

 

two-year-old probable hybrids, grown from Open-pollinated Austrian pine
possibly pollinated by Japanese red pine (Seedlots 3371, 3372, 3955 to
3958), and three-year-old Austrian pine (Seedlot 3955). The probable
hybrids were identified by needle stiffness, bud color, three needle
fascicles and rapid growth. They were significantly different from and
had a lower mean value than Austrian pine in needle length and width,
total number of stomata per millimeter, bud length and width and bud
color.

Forty-seven percent of the seedlings in the open-pollinated
Austrian pine seedlots were identified as probable hybrids because
they were tall, had needles less stiff than the comparison Austrian
pine, and also had red-brown buds. The actual hybrid yield may be as
high as eighty-five percent. The additional seedlings had red-brown buds,
but were not taller and did not have less stiff needles than the compar-
ison Austrian pines.

The probable hybrids identified by three characters outgrew the
Austrian pine. Twenty-five of the two-year-old probable hybrids were
#5.9 centimeters tall, which was significantly different from the same
number of three-year-old Austrian pine seedlings only 16.2 centimeters
tall (Table 6).

Eighty-eight percent of the probable hybrids had some fascicles
with three needles in them. In contrast, pure Austrian pine had a
significantly lower value with only 15 percent of the seedlings posses-

sing some fascicles with three needles.

20

TABLE 6--Comparison of Austrian pine and probable Austrian X Japanese

red pine seedlings(a)

 

 

 

Character and unit Probable
of measurement P. nigra(b) hybrids(c)
NEEDLE
Length(mm.) 109 93*
Width(mm.) 1.31 1.10"
Rows of stomata(no.) 7.9 7.8
Stomata per mm.(no.) 93 8U*
BUD
Length(mm.) 21.4 16. 5*
Width(mm.) 5-6 u.8*
Color Tan Brown*
Height in cm. 16.2 A5.9*

 

* Differs significantly (5 percent level) from Austrian pine.

(a) Twenty-five trees of each kind were measured.

(b) 3-year-old seedlings grown from seed collected in Yugoslavia.

(c) 2-year-old seedlings from seed collected at Kelltgg Forest.

21

One-year-old nursery measurements.--Seedlots of Japanese red pine,

 

pure Austrian pine and open-pollinated Austrian pine, possibly pollinated
by Japanese red pine, were germinated in the greenhouse and later trans-
planted to the nursery. Possible Austrian X Japanese red pine hybrids

were identified in the open-pollinated Austrian pine by their red-brown
buds and secondary needles. At the end of the first growing season the
suspected hybrids were significantly taller than similarly treated Austrian
or Japanese red pine seedlings, as shown in the following tabulation which

is based upon 25 trees of each kind.

 

 

 

 

l-year
Species height
Centimeters
P. nigra 11.8
Probable hybrids 15.1
P. densiflora 10.5

 

 

In October 1966, seedlings in a broadcast-sown seedbed of pure Austrian
pine (Seedlots 3951, 3952) were green, while at the same time a broadcast-
sown seedbed of Japanese red pine had purple seedlings (Seedlot 3955).

A similarly treated seedbed of Austrian pine, possibly pollinated by
Japanese red pine (Seedlots 3955 to 3958), had both green and purple
seedlings. No other differences were evident between seedlings in the

three seedbeds. Based on color, the probable hybrid yield is 54 percent.

POSSIBLE EXPLANATIONS OF THE HIGH YIELD OF HYBRIDS

The high yield of Austrian X Japanese red pine hybrids in the Open-
pollinated Austrian pine is unusual. There may be several reasons for
it. Flowering dates for both Austrian and Japanese red pine have been
studied for the last five years at Michigan State University and an over-
lap of two to four days was recorded. As the Spring winds from the south
and southwest pass through the Japanese red pine they could pick up pollen
and transport it east to the receptive female flowers on the Austrian
pine trees.

One reason why the hybrid yield seems so high is that identification
of the hybrids at age two may be wrong. Individual trees have been labeled
as probable hybrids and their performance will be watched to verify their
hybridity.

Another possibility is that the hybrid yield actually represents
the percent of pollen of both Austrian and Japanese red pine present.

The name P. densiflora means many flowers. It may be, that there is as

 

much or more Japanese red pine pollen available in the Austrian pine stand
as there is pollen from the Austrian pine itself.

Polyembryony has been observed in the pines and very likely could
be the reason for the high yield of hybrids. Fertilization of the
archegonia in pines takes place about 13 months after pollination. Two

to five archegonia may be present at the micropylar end of the female

22

23
gametophyte at this time, and all archegonia can be fertilized. After
fertilization, each archegonium differentiatessnspensor cells, which
thrust each proembryo deep into the female gametophyte where the pro-
embryo develops into the embryo.

Competition between the different archegonia, one of which ulti-
mately develops into the embryo, may occur at any stage of development.
Some likely places are in the development of the suspensor cells or the
proembryo. In the Austrian pine at the Kellogg Forest, perhaps only
one archegonium is fertilized by Japanese red pine, but somehow it has
an advantage over the other archegonia fertilized by Austrian pine in
developing into the embryo. This ability of the archegonium fertilized
by Japanese red pine to suppress those fertilized by Austrian pine may

be an early expression of heterosis.

A POSSIBLE SEED ORCHARD SCHEME

Various approaches may be used in developing a productive seed
orchard that will yield high quantities of Austrian X Japanese red
pine hybrids. Because the percent of hybrids in the open-pollinated
Austrian pine is high, controlled pollinations will not be necessary.
The most promising method of mass-pollination is the one used by nature
at the Kellogg Forest, pollination by wind. Present evidence indicates
that the wind will carry quantities of Japanese red pine pollen into
nearby Austrian pine stands. A hybrid yield of at least 50 percent
can be expected with this type of pollination.

One long-range approach of supplying the Japanese red pine pollen
source is to grow both Austrian and Japanese red pine from seed and
mix the two in outplantings. The main advantage of using this approach
is that a choice can be made as to which variety of P. nigra to use.
The main disadvantage is the long time needed for the Austrian pine to
flower. Even using flower producing stimulants, the minimum time need-
ed for the Austrian pine to flower would be around 20 years.

A more realistic approach to mass-producing the hybrids would be
to locate already flowering Austrian pine stands and plant Japanese
red pine around them. Japanese red pine flowers prolifically at 10
years of age, so production of the hybrids would begin in one-half the
time needed with the other scheme. The main disadvantage, here, however
is the source of P. nigra used may not be the most desirable. Con-

sequently, the hybrids produced may be slower growing and have coarser

2A

25

d
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y

h I
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r

LITERATURE CITED
Austin, L. (1927). A new enterprise in forest tree breeding.
Jour. Forestry 25: 928-953.

Critchfield, W. B. (1963). The Austrian X Red Pine hybrid. Silvae
Genetica 12: 187-192.

Ferguson, M. C. (190”). Contributions to The Life History of Pinus.
Academy of Sciences 153 pp.

 

Gardner, E. J. (196A). Principles of Genetics. John Wiley and Sons,
Inc. 386 pp.

 

Hyun, S. K. (1956). Forest tree breeding work in Korea. Suwon,
Institute of Forest Genetics. Institute Paper 1. 16 pp.

Mergen, F. (1958). Applicability of the distribution of stomates to
verify pine hybrids. Silvae Genetica. 6: 107-109.

Vidakovic, M. (1966). Some characteristics of the needle structure
and growth in hybrids between Austrian pine and Japanese red pine.
Silvae Genetica 15: 155-160.,

Vidakovic, M. (1958). Investigations on the intermediate type between
the Austrian and the Scots pine. Silvae Genetica 7: 12-19.

Wright, J. W. (1962). Genetics of forest tree improvement.
FAO, Rome 399 pp.

 

Wright, J. W. and Gabriel, W. J. (1958). Species hybridization in the
hard pines, series Sylvestres. Silvae Genetica 7: 109-115.

26

VITA

DAVID S. CANAVERA
Candidate for the degree of

Master of Science

Guidance Committee:
M. W. Adams, J. W. Hanover, D. P. White
J. W. Wright (Major Professor).
Dissertation:
Austrian X Japanese red pine hybrids: morphological features,
natural distribution, and yield from open-pollinated Austrian Pine.
Outline of studies:
Major: Forestry
Michigan Technological University, BSF, 1965
Michigan State University, MSF, 1967
Biography:
Born September u, 1993 in Norway, Michigan
Experience:
Forestry Aid, U. S. Forest Service, Rapid River, Michigan, summers
of 1963, 1964.
Research Associate, Michigan Department of Conservation, Michigan
State University, 1965 to 1967.
Organizations:
Society of American Foresters

Xi Sigma Pi

CH GAN STATE UNIVERSITY LIBRARIE

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