—1 anraster Farming, Saturday, January 6, 1973
12
Turkey Breeding Industry Sees Possible Breakthrough
Virgin birth in the turkey has
been confirmed at The Penn
sylvania State University to stem
from eggs whose germ cells are
normal
The findings, which emerge
after 12 years of cooperative
research by Dr Edward Buss
and Dr MW Olsen (USDA),
clear the way for an intensive
effort to determine if a virus is
the trigger of the phenomenon,
known as parthenogemcity.
Parthenogenesis, like cancer,
is a form of unexpected cell
proliferation The term means
virgin birth- female germ cells
begin to divide and multiply
without benefit of male sperm
Parthenogenesis is known in
insects but the turkey is the
highest animal m which it has
been observed
In that bird it is an extremely
fragile mechanism less than
half of one percent of all eggs that
are self-fertilized result in
mature individuals
Aborted embryos, spots of
blood, or mere fragments of
membrane are the issue of rule
However, parthenogenesis
could throw new light on the role
of the virus in abnormal cell
growth It also has virtue that
could prove a bonanaza to the
half-bilhon-dollar turkey
breeding industry.
Until now, scientists have
believed that some error in the
process by which chromosomes
separate (meiosis) was
responsible for parthenogenesis
But Buss and Olsen proved that
no such errors take place Eggs of
parthenogenic mothers, they
found, begin as haploids, that is,
they contain one set of
chromosomes, which is normal
In view of this evidence, Buss
and Olsen concluded that some
outside agency is very likely the
trigger of virgin birth in the
turkey That agency might be a
\ irus
In joint but deliberately
separated experiments con
cluded in 1966 the two men had
demonstrated that the fowl pox
(a virus! seems to enchance
parthenogenicity
In a family of birds kept in a
supposed virus-free environment
at University Park, Buss, by
selective mating, observed an 18
per cent increase in par
thenogenicity but no embryos
At Beltsville, when females
were vaccinated with virus the
same 18 per cent increase was
noted but, along with it, some
embryos were produced This
was encouraging, but not con
clusive evidence that a virus is
involved
Now, Dr Buss has just em
barked on a new experiment in
which he will mate birds in the
presumed absence of the virus,
then remate the same birds after
the male has been vaccinated
with fowl pox
“What we are after,” says
Buss, “is evidence as to whether
the outside agent causing par
thenogenicity is passed on
piggyback — from one generation
to another This would mean it
had not only stimulated virgin
birth but had infiltrated the cell
nucleus and caused a genetic
change Positive results from the
experiments—which are ex
pected to take five years—would
constitute strong evidence for the
theory that a virus can trigger
abnormal cell proliferation ”
It has long been known that
parthenogenesis may be
triggered by mechanical means
(one scientist got reproduction
going in a frog by poking into its
eggs with a needle), but it is not
known if the virus works by
mechanical or chemical means,
or both
If mechanical, the virus is
presumed to act somewhat like a
| ) > V T t % O \*A| >.»
speck of sand in an oyster: a
foreign body, the sand stimulates
growth that can result in a pearl.
So the virus: its presence
sometimes irritates the genetic
material into activity.
The process, if it proves con
trollable, could lead to a pearl of
spectacular dimensions for the
turkey breeding industry.
For, if virgin birth can be
deliberately induced in turkeys of
top pedigree, by viral
inoculation, a sort of “super
bird” might be achieved, one in
which undesirable charac
teristics have been eliminated by
parthenogenesis because of the
fragility associated with it.
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That fragility is due to
inequities in one of nature’s most
delicate balancing acts; the
“juggling” of genetic material
(chromosomes) so that the
contributions of both a male and
female are intermixed.
In parthenogenesis, because no
male is represented, this balance
is impossible. Thus, “bad” genes
from the mother have no chance
of being tempered by “good”
genes donated by a father.
The difficulty becomes
manifest when cells undergo a
genetic change known as
diploidy A diploid cell is one that
has two sets of chromosomes. In
normal germ cells, after
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diploidy, the crucial balance is
maintained between male and
female donations.
In parthenogenetic cells,
however, when bad genes are
doubled the balance is lost: their
influence becomes lethal. This is
why most parthenogenetic off
spring never see the light of day.
By the same token, those few
who do survive (all males) are
likely to be genetically clean:
they must have been purged of
bad genes or they would not have
survived. If these “super-birds”
can be mated to carefully
selected females, considerable
inprovement might be made in a
particular stock of turkeys.
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Dr. Buss’ experiments are
funded in part by the Agricultural
Experiment Station at The
Pennsylvania State University.
Graduate Research Assistant
Mr. L. J. Gaffney, of Australia,
assists in one phase of the
project.
The Buss-Olsen research into
parthenogemcity was originally
stimulated by the turkey
breeding industry, which an
nually suffers millions of dollars
of losses due to infertile eggs.
These are thought to be the result
of parthenogenesis which, as
stated in the theory, usually
results in abortions of only
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