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LA
x" ABSTRACT

THE GENOMES OF AGROPYRON TRACHYCAULUM
(LINK) MALTE AND HORDEUM JUBATUM L.
AND THEIR HYBRIDIZATION WITH
HORDEUM VULGARE L.

bv

*

Rye-Ho Huang

Natural hybrids of Agropyron trachycaulum (Link) Malte
with Hordeum jubatum L. were collected from Alaska. The
putative parents of these natural hybrids were crossed
reciprocally obtaining ten artificial hybrids. Nine of

these hybrids resulted with A. trachycaulum as the maternal

 

parent, and one with H. jubatum as the maternal parent.
Morphologically, there are no differences among the natural

and reciprocal artificial hybrids. Hybrids with Agropyron

 

as the maternal parent show more growth vigor than those
with Hordeum as the maternal parent.

Observations of chromosome pairing in pollen mother
cell in the natural hybrids show the following averages:
16.38 univalents, 5.44 bivalents, 0.14 trivalents while in

the artificial hybrids with Agropyron as the female, averages

 

were 11.51 univalents, 7.22 bivalents, 0.67 trivalents.

With H. jubatum as the female the averages were 15.80 univalents,

Rye-Ho Huang

5.60 bivalents, 0.32 trivalents, and 0.01 quardrivalents.
Based on this study, there is one genome in common between

A. trachycaulum and H. jubatum, the second genome of H. jubatum

 

 

has segmental homology with the common genome, and the second
A. trachycaulum genome has no homology with the others
appearing as seven univalents. The genome formulae were
A.A.A:A: and A.A_TT for Hordeum jubatum and Agropyron

J J J J J J
trachycaulum, respectively.

 

 

 

Amphiploids were obtained by colchicine treatment of
the natural hybrid by Robert Stiedl. Fertility was restored
with seed-set ranging from 0~30 per spike.

Chromosome association in the amphiploid showed
significant reduction in univalents, and no increase in the
multivalents indicating that the allotetraploid genomes of

H. jubatum and A. trachycaulum are partially homologous.

 

 

Progenies of the amphiploid show variation in morphology
and seed-set indicating the possibility that the chromosome
abnormality may extend to subsequent generations.

Cultivated barley (Hordeum vulgare L.), diploid and

 

tetraploid, used as pollen parents were Crossed with the
amphiploid to improve winterhardiness of cultivated barley
(for breeding purposes) by transmitting genes from both

Agropyron and Hordeum sources. Hybrid plants of the amphiploid

 

X H. vulgare (4x) and H. vulgare (2x) were obtained through

 

 

embryo culture. The morphology of the hybrid plants approaches

H. vulgare more closely for the case where H. vulgare (4x)

 

was used as might be expected. Apomixis, in one case, of a

*4

 

Rye-Ho Huang

reduced egg from the amphiploid was found to be morphologically
similar to the natural hybrid.

From preliminary cytological observations of pollen
mother cells the conclusion was reached that the genome is
unbalanced in hybrids with a constitution of AjAjAgTV
whereas the morphological characteristics of the VV genome
are predominant over those of AjAgT when present in a
constitution of AjAjAgTVV' In the former constitution, three
distinct chromosome groups are formed with two spindles
resulting in a tripolar division probably based on the
presence of three different genomes.

Stainable pollen grains were found only rarely and

the hybrid plants were completely sterile. Using H. vulgare

 

as the maternal parent in crosses with the amphiploid gives a

promising alternative for restoring H. vulgare chromosomes

 

to its own cytOplasm after recurrent backcrosses to H. vulgare.

 

At the point when fertility is at least partially restored,
it is hoped that random mating plus selection will permit
transfer of genetic information from the wild species to

H. vulgare cultivars.

 

THE GENOMES OF AGROPYRON TRACHYCAULUM
(LINK) MALTE AND HORDEUM JUBATUM L.
AND THEIR HYBRIDIZATION WITH

HORDEUM VULGAHE L .

BY

Rye-Ho Huang

A THESIS

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

MASTER OF SCIENCE
Department of Crop and Soil Sciences

1975

ACKNOWLEDGEMENTS

The author wishes to express his sincere gratitude
and appreciation to Dr. John E. Grafius for his guidance,
encouragement in this research and helpful advice in the
preparation of the manuscript.

Thanks is expressed to Dr. William Tai, Dr. D.E. Smith
for their helpful research facilities and preparation of
this manuscript.

A special thanks to Robert P. Steidl for his
donation of material in this study. Lynn E. Murry for her

suggestions in writing of the manuscript.

ii

TABLE OF CONTENTS

ACKNOWLEDGEMENTS . . . . . . .'. . . . . . .

TABLE OF CONTENTS . . . . . . . . . . . . .

LIST OF

LIST OF

TABLES . . . . . . . . . . . . . .

FIGURES . . . . . . . . . . . . . .

INTRODUCTION 0 O O O O O O O O O O O O O O 0

LITERATURE REVIEW . . . . . . . . . . . . .

Intergeneric Cross Between Agropyron
Species and Hordeum Species . . . .
The Genome Relationships of AgroPyron

 

 

and Hordeum . . . . . . . . . . . .
Agropyron and Hordeum Species as Wild
Sources for Breeding . . . . . . .

 

MATERIALS AND METHODS . . . . . . . . . . .

RESULTS

Materials Used in the Crosses . . . .
Method of Hybridization . . . . . . .
Embryo Culture . . . . . . . . . . .
Cytological Techniques . . . . . . .

crosses O O O O O O I O O O O O O O O

Morphological and Agronomical Characteristics

of Hybrid Plants . . . . . . . . .
Cytological Studies . . . . . . . . .

DISCUSSION 0 O O O O O O O O O O O O O O O 0

LITERATURE CITED . . . . . . . . . . . . . .

APPENDIX C O O O O O O O O O O O O O O O O 0

iii

Page
ii
iii

iv

LIST OF TABLES

Table Page
1. The designation and source of plants . . . . . . 9
2. Seed set from nitrogeneric crosses between

H. jubatum (2n = 28) and A. trachycaulum
I2n = 28). . . . . . . . . . . . . . . . . . . . 13

 

 

3. Seed set from amphiploid crosses with H;
vulgare. . . . . . . . . . . . . . . . . . . . . 15
4. Plants obtained from amphiploid crosses

with H. vulgare using embryo culture
techniques . . . . . . . . . . . . . . . . . . . 15

 

5. Quantitative characters of the parents and
F1 hybrids . . . . . . . . . . . . . . . . . . . 16

6. Chromosome association at metaphase I in
Agropyron trachycaulum, Hordeum jubatum,
spontaneous and artificial hybrids,
amphiploid and amphiploid X Hordeum
vulgare (2x) . . . . . . . . . . . . . . . . . . 37

 

7. Chromosome variation observed from P.M.C.
in AIN442-2 O O O O 0 O O O O O O O O O I O O O 38

8. Comparison of micronuclei quartete in

natural hybrid, artificial hybrid and
amphiploid . . . . . . . . . . . . . . . . . . . 39

iv

LIST OF FIGURES

Page

Young seedling on paper towel in liquid
media 0 O O O O O O O O O O O I O O O O O O O 0 14

Growth habits of A. trachycaulum X
H. jubatum O O O O 0 O I O O O O O O O O O O O 18

 

 

Spike of A. trachycaulum X H. jubatum . . . . . 19

 

 

Spikelet of A. trachycaulum X H. jubatum . . . 20

 

 

Spike of A. trachycaulum (right) hybrid
(A. trachycaulum X H. jubatum) (center)
and H._jubatum (left) . . . . . . . . . . . . . 21

 

 

 

 

Growth habit of H. jubatum X A. trachycaulum. . 22

 

 

Spike of H. jubatum X A. trachycaulum . . . . . 23

 

 

Spikelet of H._jubatum X A. trachycaulum . . . 24

 

 

Growth habit of amphiploid derived from
natural hybrid by colchicine treatment . . . . 26

Spike of amphiploid derived from natural
hybrid by colchicine treatment . . . . . . . . 27

Spikelet of amphiploid derived from
natural hybrid by colchicine treatment . . . . 28

Growth habit of hybrid of amphiploid
crossed with H. vulgare (2x) designated
as AHV 442-2 . . . . . . . . . . . . . . . . . 29

 

Spike of hybrid of amphiploid crossed
with H. vulgare (2x) designated as
AHV 442-2 . . . . . . . . . . . . . . . . . . . 30

 

Spikelet of hybrid of amphiploid crossed
with H. vulgare (2x) designated as
AHV 442-2 . . . . . . . . . . . . . . . . . . . 31

 

Figure

6.D. Auricle of hybrid of amphiploid crossed
with H. vulgare (2x) designated as
AHV 442-2 0 O O O O O O O O O O O O O O O O O

 

Plate I

7. Somatic chromosomes in root-tip metaphase
I of A. trachycaulum showing two pairs of
satellited chromosomes (arrow) 2n = 28 . .

 

8. Metaphase I in A. trachycaulum showing
14 bivalents. . . . . . . . . . . . . . . . .

 

9. Somatic chromosome in root-tip cells
of H. jubatum, 2n = 28 . . . . . . . . . . .

 

10. Somatic chromosome in root-tip cell of
natural hybrid of A. trachycaulum X
H. jllbatum, 2n = 28 o o o o o o o o o o o o o

 

 

Plate II Spontaneous hybrid

11. Early zygotene stage showing a couple
of chromosomes which were excluded from
the major group . . . . . . . . . . . . . . .

12. Metaphase I in natural hybrid showing 6
bivalents (two ring and four rod) and
one loosely paired trivalent . . . . . . . .

 

 

13. Metaphase II in natural hybrid . . . . . . .
14. Irregular cell division in microspore . . . .
X875
Plate III Synthetic hybrid A. trachycaulum
X H. jubatum
15. Diakinesis in the hybrid showing seven uni-

valents spread out earlier form major group .

16. Late telophase I in hybrid showing six
chromatids separated at first division . . .
17. Two micronuclei after first division in

hybrid . . . . . . . . . . . . . . . . . . .

18. Tetrads having micronuclei in hybrid . . . .

vi

Page

32

41

41

41

41

43

43
43

43

45

45

45
45

Figure

Plate IV H. jubatum X A. trachycaulum

19.

20.

21.

22.

 

 

Different size and condensation of the

chromosome group in prophase I in
hybrid . . . . . . . . . . . . .

Admixture chromosome association and
seven univalents at metaphase I in

hybrid . . . . . . . . . . . . .

Decoiled chromosome at late telophase

I in hybrid . . . . . . . . . .

Tetrads having micronuclei in hybrid .

Plate V Amphiploids

23.

24.

25.

26.

Pachytene stage showing two nuclei in

amphiploid . . . . . . . . . . .

Metaphase I in amphiploid showing one

trivalents (arrow) . . . . . . .

Anaphase II in amphiploid showing
chromosome bridge (arrow) . . .

Tetrad having micronuclei in amphiploid

Plate VI AHV 442-2

27.
28.

29.

30.

Unequal segregation at metaphase I .

Unequal segregation at Anaphase I

Irregular cytokinesis with chromosome

bridge 0 O I O O O O O O O O O 0

Three distinct groups with two spindles

at metaphase I . . . . . . . . .

Plate VII AHV 442-2

31.

32.

Irregular cell division with four
chromosomes in one cell . . . .

Microspore with three chromosomes

vii

Page

47

47

47

47

49

49

49
49

51
51

51

51

53
53

Figure

33.

34.

Page

Multipolar cell division having more
than four tetrads and an irregular
chromosome number in microspore . . . . . . . . 53
Rare stainable pollen in anther

tissue. . . . .

viii

INTRODUCTION

The genera Agropyron and Hordeum have been considered

 

wealthy sources for transmitting desirable traits to both
barley and wheat. Many substantial achievements have been

reported by using Agropyron species to improve wheat disease

 

resistance (Elliott, 1957; Rillo, 1970) and winterhardiness.
It should be possible to transfer genes for winterhardiness,
disease and insect resistance, drought and salt tolerance etc.

to cultivated barley, H. vulgare L.

 

Barley improvement by interspecific crosses between

H. vulgare and one of the wild Hordeum species has been slow

 

due to unknown incompatibility mechanisms from the level of
pollination to the level of chromosome elimination in the
hybrid embryo develOpment and differentiation.

The combination of the Hordeum and Agropyron genomes

 

presents potential breeding implications for increasing
variation and complementary stability in hybridization programs
using wild species. Natural and artificial hybrids between

A. trachycaulum (Link) Malte and H.#jubatum L. were easily

 

 

obtained. One genome in common has been well documented in a
cytogenetic study between these two genera (Boyle and Holmgren,
1954). Partially fertile amphiploids were employed in crosses

with H. vulgare in this study. Either genomes of H. jubatum

 

 

or A. trachycaulum or genomes from both species might associate

 

with the genome of H. vulgare and transmit desirable character-

 

istics from the wild source to the cultivated barley.

The objectives of this study are:

1)

2)

3)

4)

to elucidate the genome relationship between

A. trachycaulum and H. jubatum in natural hybrids

 

 

and artificial hybridsobtained through reciprocal
crosses and amphiploid through both cytological and
morphological observations,

to study the techniques of embryo culture for
survival of hybrid plants,

to investigate the possibility of transmitting the
desired traits from the combined genomes of

A. trachycaulum and H. jubatum into the genome of

 

 

H. vulgare, and

 

to learn how barley can be hybridized with wild

species and/or other grains.

LI TERATURE REVIEW

I. Intergeneric cross between Agropyron species and Hordeum
species.

 

Spontaneous hybrids of Agropyron species X Hordeum

 

species have been found in several north temperate latitudes

since 1872. Hybrid Elymus macounii Vasey was first collected

 

and named by Vasey in 1886. The possibility of hybrids between

Agropyron species X Hordeum species was suggested by Stebbins

 

et al. (1946b). In addition, Brink, COOper and Ausherman
(1944) stated that the relative ease with which species in the

genera Agropyron, Hordeum, Elymus, Sitanion, Secale, and

 

 

 

 

Hystrix can form "intergeneric" hybrids makes possible the
production of F1 plants which may be morphologically similar
yet have different origins. Lepage first made the combined

designation as X Agrohordeum macounii (Vasey) Lepage in 1953.

 

The hybrid between Agropyron trachycaulum (Link) Malte

 

and Hordeum jubatum L. was synthesized by reciprocal crosses

 

by Boyle and Holmgren (1954) proving that at least some entities

once identified as Elymus macounii are simply Fl sterile hybrids

 

between these two genera. Later, similar studies and conclusions
were supported by Bowden (1960) and Gross (1960). Gross's
studies even produced two different partially fertile octoploid
plants (2n=56) by colchicine treatment of sterile tetraploid

X Agrohordeum macounii.

 

The frequent occurence of such intergeneric hybrids and
the ease with which they can be produced artificially hinted
that more species of these two genera might be involved in

possible hybridizations. After typification of Elymus macounii

 

Vasey by Bowden (1960), an intergeneric hybrid was reported by
Mitchell and Hodgson (1965) collected in Alaska and reclassified

as X Agrohordeum pilosilemma Mitchell and Hodgson. The

 

putative parents were AgrOpyron sericeum Hitchc. and Hordeum

 

jubatum based on convincing field observations and comparative

morphological studies.

II. The genome relationships of Agropyron and Hordeum.

 

A lot of work has been done on the genome relationships
of several Gramineae through their hybrids. Among them

Agropyron is one of the most variable genera and is closely

 

related to Triticum. A. trachycaulum is a tetraploid with

 

chromosome number 2n=28 (Myers, 1947; Covas, 1948). Based
on cytological observation of its hybrids with Hordeum, Elymus,

Sitanium, etc., the genome formula for A. trachycaulum

 

(2n=28) was given as SSXX in which "S" denotes the Agropyron

 

spicatum (Pursh) Scribn. & Smith genome and "X" is a genome of
unknown origin (Dewey, 1969, 1968). A trispecies hybrid of

Agropyron dasystachyum (Hook) Scribn., A. spicatum and

 

 

A. trachycaulum had 27 chromosomes, 13 of which were probably

 

contributed by the F of A. spicatum X A. dasystachyum and 14

 

 

1
by tetraploid A. trachycaulum. Complete pairing and multivalent

 

configuration occurred in over half of the cells (Dewey, 1968).

Since the pioneering work by Brink, et a1. (1944) on
the interspecific and intergeneric hybrids of Hordeum species,
H. jubatum has been considered to be an allotetraploid. Based
on cytological studies of natural and controlled hybrids

between A. trachycaulum and H. jubatum, Boyle and Holmgren

 

(1954) suggested that if the pairing is allosyndetic between

chromosomes of H. jubatum and A. trachycaulum, that the genome

 

 

formulae are AABB and AACC for A. trachycaulum and H. jubatum,

 

 

respectively. This is also supported by Ashman and Boyle
(1955) in their studies of the hybrid and its induced octoploid.
By cytological observation of the size differences between

the chromosomes of a H. jubatum X Secale cereale L. hybrid,

 

 

Wagenaar (1959, 1960) concluded that autosyndetic pairing

occurred and that H. jubatum was a segmental allotetraploid.

 

Rajhathy and Morrison (1959) assigned the genome formula

AABB to H. jubatum as an allotetraploid from studying hybrids

 

between H. jubatum and other species of the genus. Rajhathy

 

et a1. (1964) later agreed with Wagenaar (1959, 1960) that the

two genomes of H. jubatum may be partially homologous. Auto-

 

syndetic pairing of the AgrOpyron chromosomes was also found

 

in hybrids of Agropyron species with Secale cereale (Stebbins

 

 

and Pun, 1958).

Intergeneric hybrids of Agropyron species with Hordeum

 

species were studied by Dewey (1971); he reported that pairing

in the Agrohordeum hybrids indicated that H. jubatum and

 

 

H. brachyantherum Nevski contain a genome in common with

 

Agropyron species, but he did not specify whether the common

 

genome was the S genome or the other genome. Although Hordeum

species do not contain a genome derived from Agropyron, a

 

modified Hordeum genome apparently occurs in AgrOpyron as

 

well as in Elymus and Sitanion. Earlier, Stebbins and Pun

(1953) studied a hybrid between Secale cereale and Agropyron

 

 

intermedium (Host) Beauv. and suggested that the "genera"

 

Triticum, Aegilops, AgrOpyron, SeCale, Haynaldia and probably

 

 

Elymus represent a single large genus. In recent genome

analysis of Hordeum jubatum with its interspecific hybrids

 

from the aspect of barley breeding, Starks and Tai (1974)
designate the genome formula AjAjAjAj as a segmental allo-
tetraploid with partial homology between the two genomes whose
pairing may vary under gene influence.

III. Agropyron and Hordeum Species as wild sources for
breeding.

 

The wild relatives and progenitors of major cereal
crops have been tapped repeatedly for transmitting special
attributes which are lacking in the cultivated varieties.

Agropyron and Hordeum are closely related to cultivated wheat

 

and barley; some of the wild Species are easily crossed to

their cultivated relatives but some are not. Agropyron species

 

have been used satisfactorily to improve wheat disease

resistance of leaf blotch (Septoria tritici) (Rillo, et a1. 1970).

 

Similarly, progeny of the H. vulgare type segregated from

 

hybrids of H. leporinum Link. X H. vulgare have been reported

 

 

resistant to powdery mildew and possibly to other leaf diseases

(Hamilton, et a1. 1955). As to drought and saline tolerance,

Agropyron species are among the most capable grasses tested.
For example, Forsberg (1953) reported that slender wheatgrass,

Agropyron trachycaulum, and tall wheatgrass, A. elongatum

 

 

(Host.) Beaux, were the most alkaline tolerant of all crops
tested. Slender wheatgrass was better suited to drier saline
areas than tall wheatgrass.

Barley is the most variable cereal from the point of
View of its extreme range of morphological forms and ecological
types but it is limited in winterhardiness. It is possible
to grow barley economically under a very wide range of soil
and climatic conditions. Extending the barley acreage,
particularly for a livestock feed, has necessitated the
development of a more winterhardy winter barley. Harlan and
Shaw (1926) searched for winterhardy barley and found that
forms from high altitudes in Asia were considerably more
resistant than most other varieties. He emphasized that the
genetic constitution for winterhardiness had been much improved
through the breeding process. Optimistically, winterhardiness
of barley could reach the level displayed in wheat and rye if

barley can be crossed with winterhardy species of other genera.

MATERIALS AND METHODS

I. Materials used in the crosses.

The stocks of A. trachycaulum and H. jubatum and their

 

 

natural hybrids used were collected by Dr. J.E. Grafium from
Alaska with the aid of William W. Mitchell and Roscoe Taylor.
The amphiploid was derived from natural hybrids by colchicine
treatment. Two cultivars and tetraploid line of cultivated

H. vulgare (Table l) were used as pollen sources for crossing

with the amphiploid.

II. Method of hybridization.

It is preferable to grow the plants in a cool temperature
which will allow the spikes to protrude from the boot before
flowering and self-pollination. Plants usually need to be
subdivided and replanted for vigorous growth and healthy
spikes. A temperature around 15-20°C is satisfactory. The
procedure is as follows:

1) Choose a spike a day or two in advance of self-
pollination. Cut off top 1/4 of spike and remove bottom 1/4
of spikelets. The tip florets should be removed for better
nutrient flow to the basal florets. Insert the tweezers into
the basal floret and open the lemma and palea of the floret
and remove the young anthers. The emasculated spike then is

bagged with aluminum foil. After 1-2 days the bag is removed

Table 1. The designation and source of plants.

 

 

Plants Designation

Source

 

Agropyron trachycaulum AT-4

 

Hordeum jubatum HJ-4

 

A. trachycaulum X

 

 

H. jubatum
(Spontaneous hybrid) AT X HJ
Amphiploid (AT x HJ)2

Hordeum distichum L.
Emend Lam.
4x=28 (2 row) HV-4-2R

 

Hordeum distichum L.
Emend Lam.
2x=l4 (2 row) HV-2-2R

 

Hordeum vulgare L.
2x=l4 (6 row) HV-2-6R

 

seed from Dr. W.W. Mitchell
& R. Taylor, Palmer, Alaska

seed from Dr. W.W. Mitchell
Palmer, Alaska

clone from Dr. W.W.
Mitchell, Palmer, Alaska

colchicine treatment

obtained by Robert Steidl
Dept. of Crop Science, MSU

Dr. A.B. Schooler
N. Dakota State Univ.
Fargo, N.D.

Variety Coho CI 13852

Variety Larker CI 10648

 

10

and the ovule and lodicules expand, opening the lemmas within
a short time after exposure to light. Then pollination may
be carried out.

2) Crosses are made at early morning in order to
obtain fresh pollen. With 1/3 of the lemmas cut from the
floret, the anthers fully extrude from the lemma. Pollen may
be shed by light tapping of the spike or by clipping the
anther and tapping it on the stigma.

3) If the pollen is from the field, the pollen spikes
are cut just beneath the flag leaf with the flag leaf base
used as a hook to hang then spike upside down in a Coke
bottle.

4) For greatest success, pollination is repeated for
2—4 days on the same spike. The pollinated spike is bagged
after pollination, with bag removal after one week when no

further pollination is possible.

III. Embryo culture.

The young embryos were dissected from the immature seeds,
which collapsed within twenty days after pollination, at the
stage when the glume appears pale green. The procedure of
excising the embryo and transferring to medium was described
as follows:

1) The transfer room or chamber with tools is sprayed
with 50% commercial bleach prior to use. Tools were sterilized
in 75% alcohol and passed through a flame.

2) Harvested spikelets were disinfected by immersing

for 5 minutes in a 50% solution of bleach (one part water : one

11

part commercial bleach) and then trasnferred through three
flasks containing distilled water.

3) The embryo was dissected under180x dissecting
microscope with one hand with sharp tweezers holding the
seed and the other hand handling a dissecting needle.

4) The excised embryo is carefully oriented with the
Scutellum facing the surface othhe culture medium and the
radicle oriented downward. The medium surface should not be
broken or the embryo may sink into the medium. The embryo
is oriented the same way on a paper towel when liquid media
is employed. (Fig. l)

5) Test tubes with embryos were incubated in the dark
at room temperature. When the seedlings have two leaves and
visible roots, they should be potted in sterile soil, placed
under fluorescent lights for approximately two weeks, and then

moved to the greenhouse.

VI. Cytological techniques.

The somatic chromosome numbers of the parents and
hybrids were determined by root-tip squash techniques. Young
root-tips were pretreated in cold water (0-2°C) overnight,
fixed in Farmer's solution, and stored in a refrigerator.

The root-tips were rinsed in distilled water, hydrolysed in
l N HCl at 60°C for 20 minutes, and stained with aceto-carmine.

For meiotic studies, spikes of appropriate stages were

fixed early in the morning (approximately 5 A.M.) in Farmer's

solution and placed in the refrigerator overnight. Spikes

12

were stored in 75% alcohol after fixation. Anthers were
smeared and stained with aceto-carmine, and chromosome numbers
and associations were recorded and photographed for each cell.

Pollen stainability was determined using IZKI.

RESULTS

I. Crosses.

Using A. trachycaulum as the maternal parent in the

 

cross with H. jubatum, eighteen seeds were set, ten seeds

 

germinated and grew vigorously to maturity. In the reciprocal

cross using H. jubatum as the maternal parent, more than twenty

 

seeds were obtained; but only one seed germinated, and it

grew slowly. The hybrid plants are intermediate morphologically.
The plants were subdivided into several clones to stimulate

their growth and to build up the population. The amphiploid
induced from the natural hybrids by colchicine treatment had

0-30 seeds set per spike. The amphiploid crossed with H;

vulgare (2x) and with H. vulgare (4x) produced ten hybrids

 

through embryo culture techniques (Table 2, 3) using two kinds

of media (Appendix 1, 2).

Table 2. Seed set from intergeneric crosses between H.yjubatum
(2n=28) and A. trachycaulum (2n=28).

 

 

 

Plants No. of Spikes Total No. of No. of Hybrid
Pollinated Seeds Set Plants Prod.

A. trachycaulum ,
X H. jubatum 20 19 18*

 

 

H. jubatum X
A. traChycaulum 15 25 1*

 

 

 

*No cultures employed.

13

Figure 1. Young seedling on paper towel in liquid media.

 

15

Table 3. Seed set from Amphiploid crosses with H. vulgare.

 

 

 

Plants No. of Total No. No. of
Spikes of Plants
Pollinated Seeds Set Produced*

Amphiploid X H. vulgare
4x=28 (2 Row) 34 13 l

 

Amphiploid X H. vulgare . ..
' 2x=l4 (2 Row) 32 3 l

 

Amphiploid X H. vulgare
2x=l4 (6 Row) 21 31 8

 

 

*Embryo culture is necessary.

Table 4. Plants obtained from Amphiploid crosses with
H. vulgare using embryo culture techniques.

 

 

 

 

Media No. of Embryos No. of Plants % of Embryos
Cultured Obtained Giving Plants

Liquid 22 6 0.27

Solid 22 5 0.22

 

Of attempts to germinate three seeds in distilled water; only
one seed germinated, but died in a few days.

16

some mo Honno pumpcmum wumowpcﬂ omonucmumme
mummas> Esmpuom n >3

mmoHnmgasa u .mem

Saunas“ Esmpuom u hm

 

 

 

 

 

 

Edasmowsomuu commmonmd u Em
m m e m H G mcocxmumuoam
mcoa on o: 0: on uuogm mH0ﬂH5«
0c “HOSm 0: oc phonm oc wocmomwnsm
S.o m.o v.0 v.0 H.N o A.Sov numnma czm
mm ow Gm am am ma mxﬂmm umd
mpmamxﬁmm mo .02
xHo.oHv Aam.ouv mm.ouv 1mm.ouc Am~.ouv ASS.OHV x.aoc
H.m m.m m.m S.m S.m m.o mxﬂmm mo npmamq
o.v m.m S.N m.m m.s m.G A.Sov mama
mmHm mo sumqmq
41S.~H. Amh.muv ASS.~HV 14G.~Hv le.de ASN.4HS
am am em om mm ms 1.801 spmcma Sago
>m x .ms¢ «mam 94 x um mm x am am am moﬂpmwnmuomumso
H

.mpﬁunhn m map ocm mucmnmm mnu mo mumuomumao m>wumuﬁucmso .m magma

II. Morphological and agronomical characteristics of hybrid
plants.

A. Natural hybrid and reciprocal crosses between
A. trachycaulum and H. jubatum.

 

 

Natural and artificial hybrids of A. trachycaulum

 

(as the maternal, taller parent) crossed with H. jubatum are

 

vigorous, averaging 30 cm. in height, and intermediate between
parents (Fig. 2). The leaves of the hybrid are dark green

which seems to be a maternal effect from A. trachycaulum.

 

Spike characters showed several intermediate characteristics.

For example, H. jubatum has a long-awned glume, A. trachycaulum

 

 

is awnless, but has a larger glume; the hybrid has a short-
awned glume (Fig. 3).

It is difficult to tell which parent was the female
in the case of the natural hybrid; however, by means of
reciprocal crosses and examination of the artificial hybrids,
A. trachycaulum was determined to be the female parent in
this study. All of the hybrid pollen was empty, of smaller
size and shrunken. No stainable pollen was found. Only

one hybrid seed germinated where H. jubatum was the female;

 

this plant is lighter green, with smaller leaves in comparison
to the natural hybrid, and the growth rate is much slower
(Fig. 4). In contrast to the former hybrid, 18 hybrid plants
were obtained from the reciprocal cross, and they closely

resembled the natural hybrid.

17

 

“\

\

--‘

Figure 2.A.

18

 

 

 

 

 

\ \ I) ’

. \\ _ I I

) \ \ \ I

\ - \
\ I \ '
\
\ I I)
. N I / I
\ / x
/ ./
\4 /
/ y
,\
/
\
\

Growth habits of A. trachycaulum X H. jubatum.

 

 

Figure 2.B. Spike of A. trachycaulum X H. jubatum.

 

‘1‘ II
I III- III.
II IIINllll

Figure 2.C. Spikelet of A. trachycaulum X H. jubatum.

 

 

"I‘l‘llllll II

 

 

 

 

Figure 3. Spike of A. trachycaulum (right) hybrid (A;
"trach'caulum X'H. jubatum) (center) and H;

jubatum (left).

 

22

 

 

 

 

 

Figure 4.A. Growth habit of H. jubatum X A. trachycaulum.

 

 

 

Figure 4.B. Spike of H. jubatum X A. trachycaulum.

 

Figure 4.C. Spikelet of H. jubatum X A. trachycaulum.

 

I I
NI. I
II I I
III.

25

B. Hybrid plants of amphiploid crosses with H. vulgare.

 

In most hybrid plants, the tillering stage of the
young seedling is sub-critical as compared to embryo germina-
tion. The so-called sub-lethal effect due to genetic defects
may cause the gradual death of young seedlings although they
struggle through germination on artificial media. In the
case of a mixoploid or a seed having more than one embryo,
they may have severe somatic competition at the tillering
stage.

In the current study, hybrid plants also showed
significantly poor growth rates even after the tillering
stage. In the embryo culture hybrids, some young seedlings
died at the 2-3 leaf stage either in culture media or just
after being transplanted to sterile soil. Similar cases were
shown by Dr. A.B. Schooler for his hybrid plants.2 Sublethal-
ity of young seedlings has been documented by Morrison, et a1.

(1963) in interspecific hybrids of H. murinum L. X H. vulgare,

 

 

H. californicum Covas & Stebbins X H. vulgare, and H;

 

 

californicum X H. bulbosum L.; and by Davies (1960) in

 

 

interspecific hybrids H. vulgare X H. bulbosum.

 

 

Figure 5 shows one of the amphiploid crosses with

H. vulgare and hybrid designated as AHV 442-2 (Fig. 6)

 

photographed at full-bloom stage in August 1974 in the green-
house. The plants were about 29 cm. tall at this time, of

a dark green color inherited from the A. trachycaulum

 

 

2Presentation at 9th Barley Malting Conference at
Milwaukee, Oct. 6-10, 1974.

26

' Q \ ‘ A
4 Q .
ﬂ . ‘ o O
p
4

4'

I

1‘3
(I (A

Figure 5.A. Growth habit of amphiploid derived from natural
hybrid by colchicine treatment.

 

Figure 5.B. Spike of amphiploid derived from natural hybrid
by colchicine treatment.

 

 

{I‘I.NNN‘I;I I‘ll IIIILI

Figure 5.C. Spikelet of amphiploid derived from natural
hybrid by colchicine treatment.

 

29

 

2.2.3325:- x 2.5.5:... x x. capo-no 33 o p
. . VI?

 

    

s

 

./

Growth habit of hybrid of amphiploid crossed

 

with H. vulgare (2x) designated as AHV 442—2.

Figure 6.A.

 

 

Figure 6.B. Spike of hybrid of amphiploid crossed with H;
vulgare (2x) designated as AHV 442-2.

 

Figure 6.C. Spikelet of hybrid of amphiploid crossed with
H. vulgare (2x) designated as AHV 442-2.

 

Figure 6.D. Auricle of hybrid of amphiploid crossed with
H. vulgare (2x) designated as AHV 442-2.

 

 

33

parent. Although the plant flowered freely and grew satis—
factorily, no seeds were set. Stainable pollen was rarely

found in the anther (Fig. 37).

III. Cytological studies.

Meiotic chromosome behavior of A. trachycaulum,

 

H. jubatum, spontaneous and synthetic reciprocal-crosses of

 

 

 

A. trachycaulum and H.4jubatum, amphiploid, and amphiploid

X H. vulgare is summarized in Table 6.

 

The following is a general description of cytological
observation:

A. A. trachycaulum

 

The somatic chromosome number of A. trachycaulum

 

from the root-tip cells was counted as 2n=28 (Fig. 7). Most

of the chromosomes of A. trachycaulum are almost the same

 

length. It is difficult to identify each individual chromo-
some just by chromosome size and/or centromere position, but
two pairs of satellited chromosomes were observed (Fig. 7
arrow). At metaphase I, fourteen ring bivalents were
consistently observed (Fig. 8).

B. H. jubatum

 

The somatic chromosome number was 2n=28 (Fig. 9).
The length of the chromosome varied more than those of

A. trachycaulum. Fourteen bivalents were consistently

 

observed in metaphase I (Table 6).
C. Spontaneous hybrid of Agrohordeum macounii
Twenty-eight chromosomes were observed in the root-

tip cells (Fig.10). Metaphase I was the main stage used for

 

III‘III

III-Ill] (IIII'NNIIIII'

34

the study of chromosome associations (Fig. 12). Loosely
paired trivalents were observed in six cells, only one cell
had two trivalents, and the mean number of trivalents per
cell was 0.14. Eighty-four percent of the fifty cells
observed had tightly associated bivalents. The bivalents
ranged from 4-7 per cell with a mean of 5.44 per cell. The
range of univalents was from 7-14. A minimum of seven univa-
lents, presumably representing the non-homologous A;
trachycaulum genome, appeared in every cell observed. The
other seven univalents appear either randomly distributed
or attached to bivalents to form the loosely paired tri-
valents.

As to abnormalities in meiosis, one to several pairs
of homologous chromosomes were excluded from the major group
at the early zygotene stage (Fig. 11). Metaphase II as
observed normally follows irregular cell division giving
rise to the microspore development (Fig. 13, 14). Non-
stainable pollen of different size resulted from meiotic
abnormality and irregular cytokinesis. The anther was
shrunken and non-dehiscent, the plant was completely sterile
and no seeds were set.

D. Synthetic hybrid of A. trachygaulum X H. jubatum

 

 

Univalents ranged from 8-18 with a mean of 11.51
per cell. At diakinesis, seven univalents were isolated from
the major group and formed bivalent—like configurations
(Fig. 15). Probably, these seven univalents lagged at

anaphase I and divided precociously at that time (Fig. 16).

 

I'lltlll Ill! I ‘I.l' III

35

The number of bivalents ranged from 5-10 with a mean of 7.22
per cell. A range of 0-3 trivalents was observed in eight
cells. From 0-7 laggards were observed at metaphase II,

and consequently, micronuclei also ranging from 0-7 were
found in 97% of the quartats (Fig. 17, 18).

E. Synthetic hybrid of H. jubatum X A. trachycaulum

 

 

Inconsistent chromosome condensation and different
size chromosome groups were found at early zygotene stage
(Fig. 19). Connections between chromosomes were observed at
metaphase 1, these might have arisen from early separation of
multivalents or from sticky chromosomes (Fig. 20). Uni-
valents ranged from 7-22, averaging 15.80 per cell. A
range of 0—2 trivalents were observed in four cells with a
mean of 0.01. Loosely coiled chromosomes were observed in
telophase I (Fig. 21). Micronuclei also ranged from 0-7 in
95% of the quartets (Fig. 22).

F. Amphiploid

The chromosome number of the amphiploid was 2n=56
(Fig. 25). Two nuclei were observed at pachytene stage
(Fig. 23). Quadrivalents ranged from 0-1 cells with an
average of 0.05 per cell, while trivalents ranged from in
0-2 cells with an average of 0.71 per cell (Fig. 24).
Univalents ranged from 0-6 with an average of 2.36 per cell.
Compared to the hybrids, the number of univalents per cell
and the number of micronuclei which ranged from 1-3 per
quartet, decreased in the amphiploid (Fig. 26). Fertility was
partially restored in the amphiploid with 45% stainable pollen

grains and 0—30 seeds set per spike.

36

G. Amphiploid X H. vulgare (2x)

 

Cytological observations were carried out on only
one of the hybrid plants, AHV-442—2. Since the amphiploid

had a chromosome number 2n=56 and the H. vulgare had 2n=14,

 

the chromosome number of this hybrid is expected to be

2n=35. However, meiotic counts varied from 17 to 35 (Table
7). Unequal chromosome segregation was observed in metaphase
I (Fig. 27) and in anaphase I (Fig. 28). The chromosome
bridge formed irregular cytokinesis is evident in this

observation (Fig. 28). Presumably, the presence of H. vulgare

 

chromosomes in this hybrid contributes to the phenomenon of
tripolar diviSion (Tai 1970) and irregular spindle formation
and location after metaphase I (Fig. 30). Several chromosomes
in different sized microspores were excluded from the major
group (Fig. 31, 32, 33). Stainable pollen grains were rarely
observed within stained anthers (Fig. 34). Normally, the

anthers do not dehisce, and the plant sets no seed.

37

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 6. Chromosome association at metaphase I in Agropyron
trachycaulum, Hordeum jubatum, spontaneous and
artificial hybrids, Amphiploid and Amphiploid X
Hordeum vulgare (2x).

Plants Chromosome Association No. of
I II III IV Cells
A. trachycaulum Range 0 14 0 0 100
(2n=28) Mean 0 14.0 0 0
H. jubatum Range 0 14 0 0 100*
(2n=28), Mean 0 14.0 0 0
spontaneous Range 7-24 2—8 0—2 0 50
hybrid (2n=28) Mean 16.38 5.44 0.14 0
A. trachycaulum Range 7-18 5-10 0-3 0 31
X H. jubatum Mean 11.51 7.22 0.67 0
(2n=28)~
H. jubatum X Range 7-22 3-7 0-2 0—1 96
A. trachycaulum Mean 15.80 5.60 0.32 0.01
(2n=28)
Amphiploid Range 0-6 22-28 0-2 0-1 71
(2n=56) Mean 2.36 25.63 0.71 0.05
Amphiploid Range 0-9 ** ** ** 50
X H. vulgare Mean
(2n=35)

 

 

*From Gil Stark's data.
**Due to chromosome variation as follows on Table 7.

38

Table 7. Chromosome variation observed from P.M.C. in
AHV 442-2.

 

 

Chromosome Number No. of Cells

 

35
34
33
32
31
28
26
25
22
19
17

U1
0 lm-bU'IU'lnbmmkoHI—‘H

 

39

 

 

 

 

 

Hmo.hv Hmm.mHv ASH.mmv HNH.emV
mam o o o o Hm mm GHH HOH
sHonHsmsa
Hmm.vv Hum.mv Hma.ch Hm~.m~v Ame.mHV Amm.MHV AHm.mv Ams.mv
mme mH mm .mm «OH Hm .HG me NH
. nHHnHa HmHoHHHuHH
:38 3.2 A333 SSH: 13.43 A363 Smémv ASN.3
Hmm m a NH mm as me on . NH
cHHnms HmHsumz
A Q m s m N H o
Hmuoa mumuumao Mom “GHOSCOMOAZ mo .02

 

 

A.ucmoumm oumowpcw mommaucoummv
.pﬂunms Hmﬂowmwuum .pﬁunhs amusumc SH muwuumsq mom HoHUDSOHOAE mo GOmHHmmﬁoo

.Uﬁoamﬂnmem was

.m OHQMB

Plate I

Figure 7.

Figure 8.

Figure 9.

Figure 10.

40

Somatic chromosomes in root-tip metaphase I of
A. trachycaulum Showing two pairs of satellited
chromosomes (arrow) 2n = 28.

Metaphase I in A. trachycaulum showing 14 bivalents.

 

Somatic chromosome in root-tip cells of H. jubatum,
2n = 28.

 

Somatic chromosome in root-tip cell of natural
hybrid of A. trachycaulum X H._jubatum 2n = 28.

 

X875

41

 

 

Plate II

Figure 11.

Figure 12.

Figure 13.

Figure 14.

42

Spontaneous hybrid.

Early zygotene stage showing a couple of chromosomes
which were excluded from the major group.

Metaphase I in natural hybrid showing 6 bivalents
(two ring and four rod) and one loosely paired
trivalent.

Metaphase II in natural hybrid.

Irregular cell division in microspore.

X875

43

 

11 ti ll I.II I

44

Plate III Synthetic hybrid A. trachycaulum X H. jubatum

 

Figure 15. Diakinesis in the hybrid showing seven univalents
spread out earlier from major group.

Figure 16. Late telophase I in hybrid showing six chromatids
separated at first division.

Figure 17. Two micronuclei after first division in hybrid.

Figure 18. Tetrads having micronuclei in hybrid.

X875

45

 

A .
I V J .U ’ ....
‘ v. . .. I ‘ Ir '.
a. k . V y 1".h‘ﬂ I ~
1 .., 6’ v. .
U - r5 ' in] \U . i '
r 5 a .... ..
n p o . N. r w. B
I ~...~ o a.“ to re 1¢,..’
. I . ... a o. K . o .
. . o ‘ r L . .
' ﬂ . . O. .w‘VﬂQi‘
. " . . ..1
. . . . ...w "A... s .o
. a. . a...) . H at.
0. .LI I‘MV'O .m . ‘3 5 J. ..f
. I‘Q‘ ~ ...... . ..d
T I. n . at“... 0‘ o 1.
' . on O ‘ . 0.. o J
A .. NO. * M I b. ‘
t . f, a.“ ...? a. . u .
a u... . . 0‘
. ‘. r n 'w \J
.I

O

46

Plate IV H. jubatum X A. trachycaulum

 

 

Figure 19. Different size and condensation of the chromosome
group in prophase I in hybrid.

Figure 20. Admixture chromosome association and seven
univalents at metaphase I in hybrid.

Figure 21. Decoiled chromosome at late telophase I in
hybrid.

Figure 22. Tetrads having micronuclei in hybrid.

X875

47

 

 

48

Plate V Amphiploids

Figure

Figure

Figure

Figure

23.

24.

25.

26.

Pachytene stage showing two nuclei in amphiploid.

Metaphase I in amphiploid showing one trivalents
(arrow).

Anaphase II in amphiploid showing chromosome
bridge (arrow).

Tetrad having micronuclei in amphiploid.

X875

49

 

Plate VI

Figure 27.

Figure
Figure

Figure

28.
29.

30.

50

AHV 442-2

Unequal segregation at metaphase I.
Unequal segregation at Anaphase I.
Irregular cytokinesis with chromosome bridge.

Three distinct groups with two spindles at
metaphase I.

X875

51

 

52

Plate VII AHV 442-2

Figure 31. Irregular cell division with four chromosomes in
one cell.

Figure 32. Microspore with three chromosomes.

Figure 33. Multipolar cell division having more than four
tetrads and an irregular chromosome number in

microspore.
Figure 34. Rare stainable pollen in anther tissue.

X875

53

 

DISCUSSION

A. trachycaulum and H.¥jubatum have been considered to

 

 

have one genome in common with the formulae AABB and AACC,
respectively (Boyle and Holmgren, 1954; Ashman and Boyle,
1955). Following these formulae, chromosome association

would range from 1-7 bivalents, l4 univalents with no .
multivalents. In fact, multivalents were observed in 23.53%
of 22 cells in Boyle and Holmgren's (1954) combined data of
reciprocal crosses. In this study of the hybrid, multivalents
(tri- and quadrivalents) were observed in 22.22% of eight

cells when A. trachycaulum was the female parent, in 28.12%

 

of twenty-seven cells when H. jubatum was the female parent,

 

and in 27.55% of thirty-five cells in combined data of the
reciprocal crosses.

H. jubatum has been considered to be a segmental

 

allotetraploid by several authors (Wagenaar, 1959, 1960;
Rajhathy, et a1., 1964; Starks and Tai, 1974). The multi-
valents observed by Boyle and Holmgren (1954) and in this
study are explained by the presence of a common genome

between A. trachycaulum and H. jubatum and by the segmental

 

 

homology of the other H. jubatum genome with the common genomes.

 

The remaining A. trachycaulum genome has no homology with the

 

other three genomes and consistently shows a minimum of seven

54

55
univalents in the hybrids. Therefore, the formulae, AABB

and AACC given by Boyle and Holmgren (1954) were ruled out;

3 J 3
study for H. jubatum and A. trachycaulum respectively. If

and the formulae, AjA.AIA: and AjAjTT, were assigned in this

 

trivalents are formed by the AjAjA; association and range from
1-7, the corresponding range of univalents is from 7-13.
Quadrivalents may be formed by AjAjA; with a range of 1-3’

.
and univalents, 8e12. In special cases, AjAj of 1-7
bivalents and 14-27 univalents may occur. Starks and Tai

(1974) suggested the genome formula, AjAjAjAj for H. jubatum,

 

and proposed that chromosome pairing at a single dosage,

AjAj in the hybrids shows homologous pairing with approximately
seven bivalents observed, while at double dosage, AjAjAjAj
shows homologous pairing with seven bivalents consistently

observed in H. jubatum and no increase in the number of multi-

 

valents in the amphiploid.
In addition, autosyndetic pairing of the AgrOpyron

chromosomes was found in hybrids of Agropyron species with

 

Secale cereale (Stebbins and Pun, 1953), and in intergeneric

 

hybrids of AgrOpyron Species with Hordeum species, a modified

 

Hordeum genome apparently occurs in Agropyron as well as in

 

Elymus and Sitanion (Dewey, 1971). A. trachycaulum may possibly

0 I
be segmentally homologous with the formula AtAtAtAt instead of

a typical allotetraploid AACC, because more than seven bivalents
were observed in both spontaneous and artificial hybrids.

' .
Each AjAj and ALA: homologous pairing under single dosage

contributed more than seven bivalents in both the spontaneous

56

I
and artificial hybrids. At is believed to be partially homo-

I
logous with AjAj of H.4jubatum, while At is not. Capital "A"

 

and its apostrophes refer to partial homology of the genomes
whereas the subscripts (j) and (t) represent where the genomes
are found and do not signify the origin of the chromosomes.

When the chromosome number is doubled as found in the amphiploid,
complete genomes are formed in terms of gene dosage. Bivalent
associations are expected to prevail over multivalent ones

under double gene dosage influences. But multivalents rarely
resulted if autosynthetic pairing occured between AjA; or A'A"

t t
and ranged

instead of allosyndetic pairing between AjA; and At

from 0-3 per cell in both this and Boyle and Holmgren‘s study.

In the reciprocal crosses between A. trachycaulum and

 

H. jubatum, morphological differences were observed. The

 

hybrid of H. jubatum as female parent showed a much slower

 

growth rate, was a relatively paler green, was shorter in
height, and had a smaller flag leaf and Spike length. Based
on these observations supplemented with cytological observation

of chromosome behavior, A. trachycaulum was assumed to be the

 

female parent of the natural hybrid, Agrohordeum macounii
collected from Alaska.
The amphiploid has been successfully crossed with both

diploid and tetraploid types of cultivated H. vulgare.

 

However, from the viewpoint of crop breeding, it is still too
early to compare the relative ease and potentiality of combining

A. trachycaulum and H. jubatum genomes with the single genome

 

 

of H. vulgare versus a direct cross of H. vulgare X H. jubatum.

 

 

57

Superficially, combined genomes of two wild sources should
contribute more variability and complementary stability through

a backcross to the recurrent H. vulgare. In point of fact,

 

we have been unable to obtain these backcrosses. On the

evolutionary dimension, cultivated H. vulgare might represent

 

an opposite evolutionary current from its wild species.
Inserting the related third genome might neutralize incompatible

factors which upset the genome balance between H. vulgare and

 

its wild relatives and prevent the driving out of the wild
chromosomes too rapidly. For example, chromosome elimination
at certain stages occurred after fertilization in the hybrid

of H. vulgare crossed with its wild relative, H. bulbosum,

 

 

and abruptly resulted in haploid H. vulgare progeny (Lao &

 

Kasha 1969, Kasha & Kao 1970, Ho 1973). An analogous case

was also reported in the genus, Nicotiana (Gupta & Gupta, 1973).

 

Based on cytological observation, three distinct groups of
chromosomes with two or more spindle formations occurred. It

is evident that H. vulgare characteristics were also introduced

 

in the hybrid growth habit. Because of taxonomic classifica-

tion, the A. trachycaulum chromosomes would be expected to be

 

driven out before H. jubatum in any backcross to H. vulgare.

 

The manipulation required to gradually substitute A. trachycaulum

chromosomes and/or H.Ajubatum chromosomes into cultivated

 

H. vulgare may be considerable. For instance, Triticale is

 

 

a newly synthesized amphiploid with a constitution of AABBRR
resulting from the cross of durum wheat and rye. By means of

the new Giemsa staining technique for individual chromosome

58

identification, it was found that two pairs of the Secale
chromosomes were substituted for two pairs of the D genome
from common wheat (Gustafson and Zillinsky, 1973).

On the other hand, it is possible to shorten the time
for breeding improvement if translocation(s) between the
H. vulgare genome and its wild relatives can be induced by
irradiation before the wild genomes are driven out. Perhaps,
this would provide for the release of the desirable gene from
its unfavorable linkage.

In addition, cytOplasmic effect should not be neglected.
The chromosomes in the nucleus can be replaced through a
backcrossing, but the cytoplasm remains more or less constant.

It has been our experience in this laboratory that H. jubatum

 

cytoplasm induces male sterility in (H. jubatum X H. compressum)

 

 

X H. vulgarez. For this reason using H. vulgare as female in

 

 

a cross with the amphiploid will provide a harmonious cytOplasm

for the H. vulgare chromosomes after several recurrent back-

 

crosses to H. vulgare.

 

 

2 . . . .
Personal communication With Dr. J.E. Grafius.

LITERATURE CITED

Ashman, R.B. and W.S. Boyle. 1955. A cytological study of
the induced octoploid of an Agropyron-Hordeum hybrid.
J. Heredity, 46:297-301.

 

Bowden, W.M. 1960. Distribution and cytology of Elymus Macounii

 

vasey. Can. J. Bot. Club, 87:205—208.

Brink, R.A., D.C. C00per, and L.E. Ausherman. 1944. A hybrid
between Hordeum jubatum and Secale cereale reared from
an artificially cultivated embryo. J. Hered. 35:66-75.

 

 

Boyle, W.S. and A.H. Holmgren. 1954. A cytogenetic study of
natural and controlled hybrids between Agropyron

trachycaulum and Hordeum jubatum. Genetics. 0.

Covas, Guillermo. 1948. Taxonomic observations on the North
American species of Hordeum. Madrono, 9:233-260.

 

Davies, D.R. 1960. The embryo culture of interspecific
hybrids of Hordeum. New Phyt., 59:9-14.

Dewey, D.R. 1968. Synthetic Agropyron-Elymus hybrids: III.
Elymus Canadensis X Agropyron Caninum, A. trachycaulum
and A. striatum. Amer. J. Bot., 55(10):ll33-1139.

 

 

Dewey, D.R. 1969. Trispecies hybrids of Agropyron, Elymus,
and Sitanion. Bot. Gaz., 130:203-213.

Dewey, D.R. 1971. Genome relation among AgrOpyron spicatum,
A. scribneri, Hordeum brachyantherum, and H. arizoniEum.
Bull. Torrey Bot. Club, 98:200-206.

 

 

 

Elliott, F.C. 1957. X-ray induced translocation of Agropyron
stem rust resistance to common wheat. J. Heredity,

Forsberg, D.E. 1953. The response of various forage crOps
to saline soils. Can. J. Agr. Sci., 33(6):542-459.

Gross, A.T.H. 1960. Distribution and cytology of Elymus
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59

60

Gupta, S.B., and P. Gupta. 1973. Selective somatic elimina-
tion of Nicotiana glutinosa chromosomes in the F1 hybrids
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605-612.

 

 

 

Gustafson, and Zillinsky. 1973. CIMMYT Report on Wheat
Improvement.

Hamilton, D.G., S. Symko and J.W. Morrison. 1955. An anomalous
cross between Hordeum leporinum and H. vulgare. Can.
J. Agric. Sci., 35:907—293.

 

 

Harlan, H.V. and F.W. Shaw. 1929. Barley variety tests at
a high altitude ranch near Obsidion, Odaho. Amer.
Soc. Agron. J., 22:439-443.

Ho, K.M. 1973. Genetic control of chromosome elimination in
interspecific hybrids leading to haploid formation in
barley (Hordeum vulgare L.). Ph.D. Thesis, University
of Guelph, Canada.

 

Kao, K.N., and K.J. Kasha. 1969. Haploidy from interspecific
crosses with tetraploid barley. In Proc. Second Intern.
Barley Genetics Symp., July 6-11, 1969.

Kasha, K.J., and K.N. Kao. 1970. High frequency haploid
production in barley (Hordeum vulgare L.). Nature

 

Mitchell, W.M. and H.J. Hodgson. 1965. A new x Agrohordeum
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Morrison, J.W., Rajhathy, T. and S. Symko. 1963. Inter-
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Rajhathy, R., J.W. Morrison, and S. Symko. 1964. Inter-
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Rajhathy, T., and J.W. Morrison. 1959. Cytogenetic studies
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L.

61

Starks, G.D. and W. Tai. 1974. Genome analysis of Hordeum
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16:663-668, 1974.

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APPENDIX

62

APPENDIX I

Liquid media for embryo culture.

 

 

 

Ingredients Amount
(gm/litre)
NaZSO4 . .8
CaNO3'4H20 .58
MgSO4°7H20 .33
KNO3 .08
KCl ' .005
NaH2P04°H20 .038
Micronutrients: 1000x

MnSO4 .45
ZnSO4 .6
H3BO3 .00375
KI .03
Glycine 3.0
Thiamine HCl .1
Calcium pantothenlate 2.5
CaSO4'5H20 .025
Nam04 .025
CoC12'6H20 .025

1.

2.

The major solution plus 1 m1. micronutrients, 10 m1. iron
and 20 gms. sucrose.

Adjust the PH to 4.5 for young embryos and 5.4 for old
embryos.

 

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