Oxford Democrat., 1920-05-18
Self sterlllty Of Apple Trees.

Davis apple trees In solid block at
Highmoor Farm. Since the orohardi
were brought into shape by proper man
agement there has been heavy bloom
practically every year. This bloom has,
however, been followed by disappoint.
ing crop. A $4,000 barrel bloom" bss
given from 1000 to 1900 barrels ct bar.
vest. And naturally the biologists OF
the Maine Agricultural Experiment Sta
tion have very closely sought the reasons
therefor. The heavy "June drop" clearly
indicated that 1t was question of proper
polarization. While the cause was be.
ing sought many expedients were tried
to insure the pollenization of the bios
SONS such as the introduction of bees in
to the orchard, frost protection, etc.
Soon after acquiring the farm the sta.
ton began a study of the laws of inherit.
ance of apples. This necessitated cross
polarization. Ben Davis pollen was
found to be virile 80 far ss most other
varieties of apples were concerned. And
when other pollen was crossed on the
Ben Davis as the female there was rarely
any difficulty in obtaining good fruits
with strong seeds. One year the biolo.
gists tried hand pollinsting Ben Davis
females with Ben Davis pollen. No fruit
was obtained. This led to self pollen.
ization study of Ben Davis and the other
varieties at Highmoor Farm. Self pol
lenization was tried in two different
ways. Pollen from different blossoms
on the same tree was used In part of the
trials and pollen from other trees Of the
same variety was used in other trials.
The pollination was made at the proper
time and by experts in this kind of work.
In 126 cases where fruit bud clusters of
8 to blossoms each of Baldwin, Ben
Davis, Duchess, Early Harvest, Golden
Russet, Hurlbert Sweet, Mcintosh Red,
Northern Spy, Red Astrachan and Rhode
Island Greening were bagged SO as to
protect them from other pollen only two
fruits were obtained. These were Bald
win. In $50 trials with the same varie-
ties when the bloom was hand pollinsted
with pollen from the same tree only
fruits that matured and formed seeds
we're obtained. These were also of the
Baldwin variety. In 40 trials with about
half the above varieties where the pollen
was obtained from other trees of the
same variety not single fruit wac OBJ.
tanned. That the pollen from different
trees of the same variety had no greater
potency in fruit production than the pol
len from the same tree is not at all sur
prising. This would naturally be ex-
pected for 1t is to be remembered that all
of the trees of given variety are of COM
mon origin all having been propagated
from one original seedling These re-.
suits are striking testimony to the rela.
tive stability of buds and the trees which
grow from them.
The results obtained In the work by
the Maine Station led to the examination
of the literature to see what records had
been obtained in other states and under
other climatic conditions. It was found
that in many hundreds OF trials with 119
varieties only about one-third are known
to have ever self.fertilized and set fruit
Only 10 varieties set fruit in any number
OF the commercial varieties the Baldwin
showed itself to be self-fertile to quite an
extent in Maine and elsewhere. The JON
athan, Early Harvest, and Yellow Trans
parent are self-fertile to limited extent.
The NorthernrSpy, Esopus, Spitzenburg,
Ben Davis, Fameuse and Oldenburg were
very slightly self-fertile. OF the other
leading commercial varieties the Rhode
Island Greening, Golden Russet, Tolman
Sweet, Twenty Ounce, Mcintosh and
Gravenstein proved to be self-sterile In
all tests made. That is, so far ss known,
these we'll known varieties have never
produced an apple when fertilized by
their own pollen.
1t takes large number of tests before
a negative conclusion can be surely
reached. But these studies clearly indi-
cate that with the exception of the Bald
win there is little hope Of obtaining any
thing like good set of fruit in q large
block of any one variety of apples. This
fact explains the small set of fruit oh.
tanned In the Ben Davis orchards at
Highmoor Farm. And seems to indicate
that what fruit has been obtained has
been due to the pollen that by bees, wind
and other ways has come to the Ben
Davis trees from the varieties that occur
in the other orchards. How to correct
this by cross-polliDation led to another
series of studies on the effects of cross.
These will be reported In
another article in this series.
CHAs. D. WOODS, Director.