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New Navel Orange
v Sport from Washington Navel.
Introduced into the United States
from Brazil in 1870, the Bahia orange,
or Washington Navel, as it is now
called, is the most widely grown 01 the
commercial varieties of citrus fruits,
states "The Leader." It is undoubtedly
the King of Oranges.
Its unknown origin suggests that m
the first place it was either a definite
mutation in type, or a bud spot. This j
excellent orange is somewhat of a
paradox. Its blossoms are without
stamina! development of pollen; it
fruits without the aid of pollen, and
pollination would not increase its fruit
lulness. The pistillate, or female,
quality exists in the capacity to pro
duce seeds, but is modified, and fails to
impress its growth and transmit to it j
its own characteristics. The readiness
of the pistil to respond to artificial
pollination, and iis absence from seeds,
where an abundance of free pollen has
been distributed shows a weakness in ;
the pistil to exude the adherent sol
vents to attach the pollen germ and
excite germination, or a weakness of
the nectaries to furnish sweets to at- ;
tract the natural insect aids.
The capacity of the Navel to produce
pollen is an inherent weakness of the
stamina impulse in the tree, and is not ,
dependent upon climatic conditions, j
This removes the Navel from the va
rieties that can be modified by germ
inal changes in the embryo, or seed,
and classifies it with those varieties
which will show modifications by
adaptation in their bud development
onlv. This disposition to bud develop
ment, or bu4 variation, has long been
known as a characteristic of the
W ashington Navel orange, and there
are several varieties of navel grown in j
Victorian groves. Of these, probably
the best known arc Golden Nugget
Navel, the Corrugated Navel, the Aus
tralian Navel, Thompson's Improved
and the Navelencia. So far none of
these can be recommended for plant
ing commercially, and the necessity
for careful bud selection from proven
prolific-bearing trees which are true
to type in the working of nursery
stock has long been stressed by ex
perts of the Department of Agricul
ture, and even by experienced citrus
growers themselves. I he value of bud |
selection in the propagation of citrus j
trees has been shown by A. D. Shamel, 1
of Riverside, California, who has for j
many years been experimenting and
testing heredity in trees.
In a recent issue of the American j
"Journal of Heredity" Messrs. Shamel
and C. S. Pomeroy give some data re
garding a new Navel orange which
has been discovered in Riverside
County as a bud variation or sport on
a Washington navel orange tree in the
grove of Warren U. Robertson. It
was discovered 10 years ago, and has
since been under careful propagation
tests, and is now considered to have
definite advantages over the normal
type of Washington Navel. It has
been named the Robertson Navel.
Messrs. Shamel and Pomeroy com
menced their observations of this new
strain of Washington Navel in 1933,
and to date they report that it has
given an excellent account of itself,
and has come true with very little
variation. They consider, however,
that bud selection may eliminate these
slight deviations from type. Some
vears ago, when Shamel first under
took the work of bud selection, the
Washington Navel was said to be run
ning out. Shamel, with painstaking
diligence, set up a minute search for
variations, particularly bud sports, and
the propagation from known certified
limbs. The use of millions of certified
buds of known parentage has explod
ed completely the theory that the
Washington Navel orange is running
out. Variations, however, if unob
served, are likely to pull down the av
erage of production and quality, and
result in mediocre production.
Observed and taken advantage of,
the\' produce higher quality and more
or less fixed quality. In view of the
fact that the .majority of bud varia
tions in citrus fruits in Australia have
proved somewhat disappointing, grow
ers naturally look askance at any new
variety until such time as it has been
proved of definite superiority over the
type. The Robertson Navel, however,
seem to have borne the acid test of ex
pert investigation, and the story of its
discovery, which appears in a rtccn,^
issue ol "Pacific Rural I ress,
should prove, of interest to citrus
growers, and illustrates the value o:
careful observation of every indi
vidual tree in any grove.
In the spring of 1925 Mr. Robert
son's brother while picking oranges
found a limb ft the top of one of the
trefs bearing an unusually heavy crop
of fruit. He examined the fruit and
found that it was somewhat different
from the other fruit on the tree, was
ol larger size and had a smoother tex
ture. lie marked the limb and watch
ed it tor a period of two years, and
each vear it was found that it bore a
larger quantity of fruit of better com
mercial value than that borne by the
other limbs of the tree.
During 1925 Mr. Robertson, the
owner of the grove, cut budwood from
the limb and top-worked a seven-year
old Mediterranean Sweet. A record
was kept for two years of this budded
limb, during which time the fruit prov
ed to have the same texture and char
acteristics as the original sport limb.
At that time Mr. Robertson found
that it was earlier than the Washing
ton Navels in lus grove. lie gave the
new variety the name of the Robert
sou Cluster Navel from the fact that
it tends to bear its fruit in clusters.
The name has since been changed to
the Robertson Navel. In June, 1927,
he top-worked 91) nine-year-old St.
Michael trees from the budded limb
on the Mediterranean Sweet. The
growth from the buds on these trees
is now six years old, and consistently
produces fruit that is true in every
particular to the characteristics of the
original sport limb. In 1930 he bud
ded 11 acres of two-year-old sour
oranges. These trees are now two
years old and most of them have borne
some fruit, all of which has also proved
true to the sport limb.
Some of the characteristics of the
strain arc as follows.-The tree'blos
soms practically at the same time as
the Washington Navel, but the young
fruits of the strain grow much more
rapidly than the normal and through
so doing become large enough to re
sist the usually heavy mid-suminer
drop. Their best and most profitable
characteristic is, however, that during
all the years that records have been
kept the trees have never failed to bear
abundant crops. I he fruit tends to
grow in clusters, occasionally eight or
nine or even more oranges in one
cluster. The fruits of the strain ma
ture two or three weeks earlier than
those of the normal Washington Navel
under comparable conditions, as shown
bv their colour and the soluble solids
and acid tests ot the juice.
Showing the precocity of this vigor
ous new strain, Shamel and Pomeroy
found that the typical Robertson;
navels on the same date in mid-sum
mer had a circumference of 5.4 inches,
while Washington navels measured
only 4.1 inches. This lead 111 size was
maintained to about November 1,
nearly maturity time, when a juice test
gave a soUsblc solids and acid ratio of
8 to 1 for the Robertson strain and
only 7 to 1 for Washington. On De
cember I the ratio for the Robertson
was 9 to 1 ccrmpared to 7 to 1 for
Washington*, and at the same time the
Robertsons had sufficient colour to
pass the State test, while the Wash
ington were below standard because
of green colour. These periods would
compare with May and June in Vic
toria, just when picking commences in
northern districts. The report in the
"Journal of Heredity'' gives this bud
variation great praise, and, despite the
unpopularity of the so-called Austra
lian navel, it is quite possible that
among the local bud-sports there is
one that will prove of equal import
ance as the Robertson navel. If it has
not yet been found it may be developed
in the near future, but the discovery
of this bud-sport in California is a
definite lesson in the value of careful
observation and what may be accom
plished by systematic bud selection.
Bud sports in apples have been de
veloped by Victorian and Tasmanian
growers in the past and have proved
their value commercially. Why not
citrus fruits?
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