The Problem of Underdeveloped Seeds Occurring in Monogerm Sugorbeets
D. M.
TEKRONY AND
E. E.
Received fo·r tmblication October
1
HARDIN2
II ,
1968
Introduction
Underdeveloped sugarbeet seeds may be defined as: " Those
fruits having either completely empty (seedless) cavities or hav­
ing partially developed shrunken seeds." Fruits with under­
developed seeds have a direct effect upon the germination po­
tential of a seed lot, although they cannot be visibly detected
from completely filled fruits. In 1967, underdeveloped seeds
were reported to be the primary factor contributing to low
germination in Oregon-grown sugarbeet seed (14)4.
Even though these underdeveloped seeds are presently con­
sidered to be a serious problem, little information has been re­
ported on their occurrence in either multigerm or monogerm
sugarbeet lots. Seedlessness has been reported in other crops,
however, and has been noted by some researchers in sugarbeet
seed. Grimm (4) found that the number of filled and empty
seedballs can be determined by X-ray examination. Hogaboam
(9) confirmed Grimm's techniques and found that in 19 mono­
germ plants examined, all contained some seedless or empty fruits
which ranged from 2 to 35% . Hogaboam (9) also reported
variation in embryo and perisperm development. Some seeds
had a fully developed perisperm but an underdeveloped embryo,
while in other seeds the opposite development was observed.
Other cases of empty seedballs or seedless ovarian cavities
have been noted by researchers when conducting studies on
problems of sugarbeet seed germination. Hogaboam and Snyder
(10) found 10 % seedless ovarian cavities of seedbalts examined
in sizing experiments. They also noted that the fruit size, whether
it be diameter or thickness, was a poor indicator of the contents
of the ovarian cavity. Processors of sugarbeet seed have been
aware of empty or hollow seed balls for many years and have
attempted to determine the number present in a lot by the
"crack" tes t. This test involves cracking the seedball with a
hammer on a heavy steel plate after which the contents are
examined for internal seed development (16).
3
1 T echni ca l Paper No. 2558, Oregon Agricultural Experiment Station.
This work was
done under a project supported by the Beet Sugar Devel o pment Foundation.
2 Assistant in Farm Crops and Assistant P rofesso r, Seed Laboratory, Oregon State Uni­
versity, Corvallis, Oregon, respectively.
3 Previously referred to as undeveloped seeds by a uthor (14, 15) .
, Number in parentheses refer to literature cited.
626
of
OF HIE.
A. S. S. B. T
was conducted to evaluate the over-all
were:
L Eval ualion of methods [or
underdeveloped
seeds.
2. Determination of the location of seeds
on the
4. seeds in
areas.
Materials and Methods
outlined, four
studies
~were
Slud)) I. Evaluation of Methuds
.\Icthods used to seeds were:
1)
(~ermination-cut­
methods were conducted on 10 lots of
seed which had roll
less
than
The excisiull method was conducted on four DO-seed
of each lot. .rhe true
seed was removed from the sugarbeet fruit and
under standard conditions. This \vas
isllCd
clILting tbe
the
with a razor
blade or
alter I<\'hich it was
apart and the seed
ication (SO
was excised at a time
due to the slow, tedious
. of this method.
After excision, the naked ~eeds
and
The
which were hnn, filled and convex
class cOllsisted of ei ther no seed
y elll
or shrunken seeds
were flattened half o[ the fruit
both the good
were
following standard
the Association of Ollicial Seed
tube
The
VOL.
15, No.7,
OCTOBER
627
1969
e
e
g
g
g
g
g
g
Figure I.-Radiograph of monogenn sugarbeet seeds showing empty (e),
shrunken (s) and good (g) seeds as determined by X-ray technique.
628
JOURNAL OF THE
A. S. S. B. T.
unit was operated at 45 KVP and 3-4MA. The procedure fol­
lowed was to place the fruits on Industrial Type M film with
the seedcap facing down (against the film). The focal distance
was 18 inches and the exposure time was 10 seconds. Four 50­
seed replicates were radiographed for each lot.
Developed radiographs were examined and estimates of seed
development in each fruit were recorded into two classes, good
and underdeveloped. Seeds classed as good appeared lighter in
color on the radiograph and filled more than half of the fruit
cavity (Figure 1). Structural outline of the perisperm and embryo
can usually be seen in these good seeds. The underdeveloped
class included fruit cavities that were completely 'empty and
appeared dark colored on the radiograph. It also included the
partially developed shrunken seeds which filled less than half
of the fruit cavity or lacked perisperm or embryo development
(Figure 1).
The germination-cutting method involved hand cutting and
evaluation of fruits remaining at the final count of a lO-day
germination test. Eight 50-seed replicates of the 10 lots were
germinated following the hydrogen peroxide procedure (14).
At the final count, the fruits with ungerminated seeds were placed
•
•
Shrunken
Empty
Firm
U nderdeveIoped Seeds
Ungerminated
Seeds
Figure 2.~Cross sections of internal structures of ungerminated seed,
balls examined at the final count of a laboratory germination test using
the germination·cutting method. Firm ungerminated seeds (on left) have
firm white embryo and perisperm. Underdeveloped seeds are either shrunken
(middle) or completely empty (on right),
VOL.
15,
:\10.
7,
OCTOBER
1969
629
with the seedcap down and cut in half with a razor blade. The
halves were examined internally for seed development and sep­
arated into two seed classes, firm ungerminated and under­
developed. The firm ungerminated class included seeds which
fill more than half the fruit cavity and have white, chalky peri­
sperm and a firm white embryo (Figure 2). The underdeveloped
class included fruits having completely empty cavities or those
having partially developed shrunken seeds (Figure 2). The
seeds classified as underdeveloped (shrunken) were either dis­
colored and watery or filled less than half of the fruit cavity.
The percentages of underdeveloped seeds [(Jund by the three
methods were compared statistically and significant differences
between methods were determined using a Duncans Multiple
Range Test.
Study II. Plant Location of Cnderdeveloped Seeds
To determine the location of underdeveloped seeds on a
plant, investigations were conducted on I) an entire plant, and
2) lateral branches only. Two monogerm varieties (variety I,
SL 126 X 12R and variety 2, FG2-569H,,) were utilized for both
the plant and branch studies.
Five plants which had the same date of anthesis were selected
from each variety for the plant evaluation studies. At maturity,
branches were harvested from eight locations on each of the
10 plants. The locations (Figure 3) were as follows: 1) The
main stem from the apex down to the first lateral branch (A):
2-G) One primary lateral including side branches from each of
five vertical locations on the main stem; 1 T pper (C), mid-upper
(VIC), middle (M), mid-lower (lVI L) and lower (L); 7) Several
secondary lateral brnaches taken from primary laterals at random
locations on plant (S); and R) Several tertiary laterals taken at
random from secondary laterals on the plant (T). After removal
of similarly located branches from each of the five plants, they
were grouped into the eight groups for each variety and placed
on wire mesh screens to dry. 'IVhen completely dry, the branches
of each group were threshed and stored. A standard germination
test was conducted using eight 50-seed replicates for each location,
and the underdeveloped seeds were determined by the germina­
tion-cutting method.
Two-hundred lateral branches from 12 plants in each of two
varieties were used to determine the number of underdeveloped
seeds at different positions on an individual branch. All of these
branches had approximately the same peak flowering date and
number of fruits per branch (60-80). At maturity, the branches
·were removed from the plant and the length of each branch
630
OF THE
A.
S. B.
u
!
the lo(;ation of
II: '.fain axil (A);
laterals (U, :\fU,
.\J, ML, L); Secondar) laterals (.5); and
laterals (T). Lowest branch
indicates the 10 adjoining groups examined on individual lateral branches.
was measured. "\fter
each individual branch was cut
into lO equal sections
!)
lowest
with a· razor
blade leaving the fruits illtact on the stem
section.
the si111ibr
from all 200 branches were
into
Group number one is that
the laleral branch closeSl to the main axil. whereas
group number 10 is the extreme
of the lateral branch. The
groups were dried on wire mesh
and counted into
for O'e rm ina­
'"
tion foIl owi ng standard
C nderdeveloped
seeds were determined
method.
Ill. Effects
Final Processing
This study ,,'as conducted to determine if the final processing
were
al I of the
seeds from
VOL.
15, Xo. 7,
OCTOBER
1969 631
initiated to evaluate the occurrence of underseed
in 1965. Forty
for
at the
amined for
In 196G and 1
tested were
the germination-cutting
seeds
examined for
lots in 1966, 41 of which were
method. This included
seed for
commercial
and the remainder from small
lOR seed lots were examined of
stock fields. In 1967, a total
which
considered
This
same
For both seeel
and the areas data were kept on all samples,
were determined for the percent of under­
the Oregon production area, yearly means
for
t germination and percent firm
and Discussion
seeds as determined hy the
excision
and germination-cutting
method for 10 lots ~ire shown on Table 1. 'fhere was no
nificant difIerence between the three methods when the means
all lots were
The percentages of
the excision method, were
than those obtained
the other two methods.
was
results 'were not
results for
of the 10 lots examined.
causing the
values with the ex"
ClSlOn method ,vas the germination of shrunken seeds
in the underdeveloped class. It was observed that some shrunken
632
OF THE
A. S. S. B. T.
seeds germinated after excision, whereas seeds of similar developIneut were found
the
method. It has been shown that the
the true seed mechanically
that a similar restriction
seeds in tnta(t fruits when
method.
These seeds did germinate, however, when excised from the huit.
The X-ray results of the
seeds compare closely
to the results of the
method. This indicates
measure of underThe excision method is a slow and tedious
which
3 hours for
of 50 seeds. Since
misleading
the method is time
or accurate as the X-ray or
cannot be considered as
germination-cutting methods for
underdeveloped
seeds .
.A. (lining test can be conducted at the final count of a routine
germ illation test
method) or on dry seeds
prior to
conducted on dry seeds,
it would
test that has been used by
processors
locate
fruits while cleaning seed
lots. The primary
between the clltting test and the
"crark" test is that each seed is examined for seed development
by the
and tho:;c seeds which are ollly partially
developed
are classified as underdeveloped. "rhe
"crack" lest
the fruits with a hammer
and
\Vh Lte perispenn and
(1
in this procedure and
results
developed shrunken
present and may be
seed. Therefore, care· must
to be certain of
seed
the seed as to
method
VOL. J5, 1\(). 7,
OCTOllFR
1969
By comparing the
(Table 1), it
can be concluded that
seeds play a rna
role in lowering the
If these
developed seeds
have been
the germination
potential would have exceeded fJO
in all cases (underdeveloped
plus germination).
Table l.-Pl'rcentag(' of
,e£ds as determined by three mdhods and the
germination perrent for ten lots 01 ""'art",,,! seed.
~Icthod
Lot
GeJ miuation~
cutting
Excisiun
X-ray -
J 3.()
3().O
20.0
12.0
21.0
8.0
13,0
15.0
19.:;
13.0
19.0
12.0
24.1)
10.1)
J:J.g
16.:;
17.2
I
2
3
Il.l)
4
14.5
17.()
5
6
7
8.0
12.5
8
9
10
8.0
).rean
1
10.0
11.0
Hydrogen Peroxide :vfcthod 8
><
Gerluination"J l~).O
79_5
50 ,cC'u replicate..;:_
• l.Jndcrde\'dopcd seeds determined by excisiull method
or}H:r two methods at
lc\'cl.
siginHicanllv lr)\\'ct' than
Lowtion of endcrdcvelopcd Seeds
of underdeveloped seeds
at different
plant (Figure 3) for two varieties are
shown on Table
These results indicate that
seeds occur at all locations on a plant with at least
at each location. There was little variation in
from location to location
for an increase
Study Il.
Table 2'-P"rt,ent underdeveloped ,,",cds occurring al diHerenl vertical localiolL' on
plan Is of two sugarbeet varicties.
Planl
location1
Variety I
(SL 126 X 128)
1).0
1.),.;
10.7
5,2
ri.7
7."
5.5
7.1)
6,5
7.t)
0."
8,:)
6.1)
8.0
8.0
22.:1
7.0
7.0
16.0
(].O
9.5
description oj locati(Hl:'J,
634
JOLR~AL OF THE
be an
'Vhen
increase ,vas not lloted.
A. S. S. B. T.
increase would be
these branches and the
The increase in
2 cannot be
than the common result at this
were examined at this
a similar
Table 3.-]>crccnt UIlfifTdC'H:lopcd ('cd~
bralu:hes fer two varh:tks of monogcnll sngarbcct
adjoining: locations on lateral
<. .
seeds
Variety 1
Location on
branches!
(SL 126 X 128)
Variet), 2
(F62·569H,,)
:VIeau
:LO
2.0
4
\liddle
8.0
Ifl."
l!i,O
6
J2,0
W,O
]4,0
25.5
HW
~ec:
a
of
a branch. L,o\yer
found at the
seeds
able
:»
for
Figllre
~).
ing locations on
The
were
to
the mean of
for the two varieties examined ,vas not
for anyone location. The
of underseeds increased
at the
of the
for
was
due to the
beets
does not allow suHicient time
The tip of branch (group I
seeds or flowers which would
\,Vhen
branch
were
at similar
veloped seeds. This
and Snyder (I
that
ness, is a poor
at various locations on
plant
fruit size had little influence on the
seeds 'were
as
in size and
as fruits
locations which contained completely de­
would
to results
Hogaboam
it be diameter or thick­
content of the ovarian
VOL, I
Xo,7,
635
1969
Ill.
The final
Final
effective in
lots examined
IS
little or no
seeds from
the
found in natural fruits, This
was similar
for the three
that furnished seed for this study.
Table 4.-Effr(t of fin'll proce,,~ing" on iht" n:lllo\'ai of buits con1Hining und(Tucvclopcd
secds from eight 10t5 of IlHt110gt'l m sugarbl'ct ~c('(l.
P(T(',,'llL
Lot
numher
underdeveloped
Perrent
reduction
after
Katural fruits
Decorticated fruits
processing
15.7
17,5
18,5
8,2
24,5
4.2
41.:;
31,7
15,0
11.7
3,5
0,7
5,8
LS,Q
5.2
I
2
3
..
5
G
;1,0
0,0
2.7
such as a
fei\'
In other lots,
upon removal
seeds are Ilot removed
an immediate eHect on any precision
it is important to know the number of
seeds in a seed lot up to and after final
seeds can he determined very
method or X-ray technique ontlilleft
III attempting to correlate fruit size and
under­ a simple experiment llsing a
model seed blO\\'c1' was cone! tIeted. Each
lots of known to have underdeveloped seeds, was hlown into fOllr
classes, The first fruits to be removed
the air separa­
tion contamecl primaril) underdeveloped
seeds. A com­
636
JOI)R0:AL OF THE
A. S. S. B. T.
plete separation of fruits contammg underdeveloped seeds from
those fruits having good Jilled seeds could not be obtained at
any setting. As the air was increased 011 the seed blower, a
gradual increase in the percentage of good fruits was found in
the blotl'n portion, whereas. nnderdeveloped fruits were still
present in the heavy portion. A percentage of underdeveloped
seeds remailled in the heavy portion, even at the final blower
setting when many filled seeds had been blown out. This offers
a partial explanation of why these underdeveloped fruits will
not all be removed by final processing.
Study IV. Survey of Prodl/clion Areas
In Oregon, the significance of underdeveloped seeds on germ­
ination was first recognized in 1964 when six lots which had low
laboratory germinations were also found to have equally low
field emergence results. vVhen fruits h'om these six lots were
excised, various stages of seed development were encountered.
Th is development ranged from completely filled fruits to fruits
containing no seed or only a partially developed seed. This latter
category was termed as underdeveloped seeds and ranged from
9 to 2H% in the six lots examined. Since this percentage was
surprisingly high, the determination 'was continued on all seed
lots examined at the Oregon State Cniversity Seed Laboratory
starting in 19G5.
'rhe mean percentage of underdeveloped seeds occurring in
all Oregon-produced lots for g years (1965, 1966, 19(7) was
maintained at nearly 20% (Table 5). The mean of firm un­
germinated seeds, which are an indication of inhihitors present
in a sugarbeet lot, ranged from 2 to (i% for the same period.
The mean of all germination results for the three-year period
remained at approximately 72%. 'Vhen comparing underdeTable 5.-":\lean perrcntages of underdeveloped seed, finn ung'crminatcd seed and ger­
minated sced and gennination in Oregon-produced lots for a three-year period. ;\{ean p,er­
rentage of underdeveloped !)ccds in Arizona-produced seed for 1966 and 1967.
Finn
Lot,
Year
examined
1965
1966
40
138
l:nderdeyeloped
$eeds
ungerminated
seeds
Germination
OREGON
41
97
108
19.0
18.2
12.7
20.4
2I.:l
Comm.
22
1:},6
Stock
86
Comm.
Srock
1967
23.0
ARIZONA
1966
1967
10
20
24.2
4l.0
3.0
6.0
6.5
5.7
2.1
2.0
2.1
72.0
72.4
78.2
70.0
72.9
79.9
72.9
VOL.
]5,
~o.
7,
OCTOBER
1969
veloped
readily be
cause for low
production area. If these
it can
would
The mean of
seeds
only in the
commercial lots was lower
years
than the
mean of all lots examined. These commercial lots, even though
smaller in number,
the major
seed
111
The lots
lots are only small acreages,
are
for future plant
use.
Little infonnation was available on the
of under­
deVeloped seeds in
production areas other than Oregon.
After examination of the 1966 and
in Arizona
(Table 5),
found that the
of under­
developed seeds in
in 1966 and
the {'nired
are the primary
of commercial
Even though
seeds are found in nearly all
lots of sugarbcet
cause is uncertain. IIills (8) has
shown that
fruits
feed on the soft
can cause the
and the
cavity
r»l",,"rrp·rl tbat the
nym phs do
to be
the most
and that maximum
is caused during the
late bloom
development. He has shown
that
u",ct..elLH-lC" but states that
in one
as a possible cause
broacllv
to include any seedless fruit, unless it is clef!­
fertilization and abortion have taken place,
sugarbeets.
induction
; 3) Stimulation
; 4) Effects clue to nutri~
of the plant (1,6,
and 5) Effects due to insects
on the plant
It seems possible to theorize that one
or more of these may under natural conditions be
the
plant to cause a
seedless
638 OF
A. S, S, B. T,
underdeveloped seeds
empty or seedless fruits would
seeds
in this
it is
is the
Nutritional
in seed
areas have also been theorized as a possible cause
seeds. In other crops. a close relationship of
and
tube growth to some nutrient elements
may add
to this hypothesis
1). It has been shown
adequate supplies of boron (II calcium
and other minor elements must
available
and
If these minor elements are
eventuallv affect fertilization and seed set.
It seems
similar' minor elements may alfect seed
plants if they are
in the seeel
direct
exceeds
of that lot
seeds in a seed lot has a
\Vhen this
in this study, the germination
be
than 80. If the
seeds have been found in all seed lots pro­
over the last ;) years and are an
in
as ""veil. Since liuk information
as to the cause
these
methods should be available for detecting
and
station.
locations on a
with fruit size. Final
effecti ve III
or
factor
monogenn sllgar­
VOL. 1
~o.
7, OCTOBER 1969
639
lots in the
to increase
varieties, it is essential
inated either by mechanical or other means.
Literature Cited
(1) D. L. and 1.. C
'.\1. !';. A. S.
ABBOTT,
19()2.
Review 1'1
LUCKWILL.
Great Britain
1965. Rules for
seeds.
Proc. Assoc. OfL Seed Anal. 54 (2): 1·112.
BREWBAKER, J 1.. and B. H. KW\CK.
]963. The essential role of
calcium ion in
and pollen tube
Am.
J. Beet. 50:
(4)
H. G. bei
ASSOCIATIOX OF OFFICIAL SEED i\:"ALYSTS.
F C. 1936. Induction of Imil development
growth
chemicals. Proc. l'\'atl. Acad. Sci. 22: 628-638.
(G) GUSTAFSOX,
G. I
natural or artificial. Review. 8: 599-654. (7) HAYUIERTO'.', J. 1.. 1961. Studies on on the emergence aud Sci. 56: 13-228. HII.LS, ORlX A. 196.). Jnsects
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Handbook 253, ARS, l'SDA.
H()GABOA~1. G. J. 1961,
some
seed characters
Soc.
Beet Techno!.
Influence of size of fruit
(10) HOGAlHJA.\I, C. J and F. \V. S"YDER.
and seed
of a monogerm
lAm.
Soc.
Reet TechnoL l'l
: I J 6· 126.
R. Sf. and I. K.. V.\SIL.
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Loo, T, 1.. and T. C. HWA'\G, 1
Growth stimulation
indole·3-acetic acid and colchicine in
tube
Am.
31:
(13) SXYDER, F. \V. I of
seeds. J. (H)TEKRO;';Y. D. :\J. and E. E. HARDI','.
com­
of
in mOllogerlll Sligar beet seed. Proc. Assoc.
56: 130-J
TEKRO'.'Y. i\I. and
E. HARDI\:. 1967, The use of x·ray, excision
and
methods
an estimate of poten tial
of
Beta
1.. ProL. Assoc. OIL Seed Anal.
(16) TOD!A:", BIOZ'>. 1918.
of seed
proAm. Soc.
TechnoL Vol. 5. p. 78.
(17) TI;KEY. H. B. 1954. Plant
in agriculture.
-Wiley and
Sons. :\'ew York.
S. 1934. The second report on thl' behavior of the
(I R)
of seedless fruits caused
inr.crspecific
118·24.
GUSTAFSOi\;,