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THE EFFECT OF FOUR STORAGE TREATMENTS ON
SEED Y\ELD AND YTELD COMPONENTS 0R THREE
ONION \NBREDS

Thesis for the Degree of M. S.’
MICHTGAN STATE UNNERSTTY
PETER STANDlSH HESSE
1977

 

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ABSTRACT

THE EFFECT OF FOUR STORAGE TREATMENTS ON SEED YIELD AND
YIELD COMPONENTS OF THREE ONION INBREDS

BY

Peter Standish Hesse

Three M.S.U. onion inbreds, 661-20, 826, and 2399, were given
the following storage treatments: 2°C 24 weeks, 2°C 12 weeks-10°C
12 weeks, 10°C 12 weeks-2°C 12 weeks, and 10°C 24 weeks.

The 2°C 24 week treatment delayed the emergence of inbreds
2399 and 826 while 10°C for 24 weeks delayed inbred 661-20.

Flowering was delayed for approximately 5 days by storage at
2°C for 24 weeks, while storage at 10°C for 24 weeks or at 10°C for
the second 12 weeks resulted in the earliest flowering. If 2°C was
given during the second 12 weeks, flowering was delayed for approxi-
mately 2.5 days. The flowering of inbred 661-20 was little affected
by the storage treatments.

The 10°C 24 week treatment resulted in the shortest primary
seedstalks and the 10°C 12 week-2°C 12 week treatment the tallest.
Inbred 661-20 produced the shortest primary seedstalks after the 2°C
24 week treatment, while inbreds 2399 and 826 produced the tallest.

The 10°C 24 week and 10°C 12 week-2°C week treatments resulted
in the most leaves per plant.

Inbred 661-20 produced 1 umbel per bulb regardless of the

storage treatment, but storage at 2°C for 24 weeks or at 2°C for the

Peter Standish Hesse
second 12 weeks resulted in a significantly greater number of florets
per umbel (therefore per bulb).

Storage of inbred 826 at 2°C for 24 weeks resulted in 1.48
umbels and the fewest florets per bulb. Storage at 2°C for the first
12 weeks resulted in approximately the same number of umbels (1.68),
but a significantly greater number of florets per bulb. If 2°C was
given for the second 12 weeks, inbred 826 again produced approxi-
mately the same number of umbels (1.38), but only an intermediate
number of florets per bulb. The 10°C 24 week treatment resulted in
2.49 umbels per bulb. This increase of l umbel per bulb did not
increase the total florets per bulb, but resulted in significantly
fewer florets per umbel.

Inbred 2399 produced 4.25 umbels after the 10°C 24 week treat-
ment, while storage at 2°C for 24 weeks resulted in 2.69 umbels.

The combination treatments resulted in 3.29 umbels per bulb.
Although for 2399 the number of umbels per bulb varied dramatically,
the total florets per bulb did not. The florets were simply dis-
tributed over the number of umbels.

For inbreds 2399 and 826, the higher number of umbels did not
produce the highest number of florets or seed yield per bulb. For
all three inbreds storage at 10°C for the first 12 weeks followed by
2°C for 12 weeks resulted in a high number of florets per umbel and
the highest seed set and seed yield per umbel.

The fewest seeds per floret occurred after the 10°C 24 week

treatment .

THE EFFECT OF FOUR STORAGE TREATMENTS ON SEED YIELD AND

YIELD COMPONENTS OF THREE ONION INBREDS

BY

Peter Standish Hesse

A THESIS

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

MASTER OF SCIENCE

Department of Horticulture

1977

To my grandmother

Mrs. Myles Standish

ii

 

ACKNOWLEDGEMENTS

The author wishes to express his sincere appreciation to Dr.
Grant Vest and to Dr. Shigemi Honma for their guidance throughout
this study and to Drs. Charles Cress and Robert Herner for their
valuable suggestions and support. Furthermore, appreciation is
expressed to Amos Lockwood and the farm crew for their help whenever
I needed it. Most of all, extreme gratitude and love is given to

my wife Peggy, for her moral support and care.

iii

LIST

II.

III.

IV.

OF TABLES.

TABLE OF CONTENTS

ImmDUCT ION O O O O C O O O O O O 0

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

The Effect of Set Storage on Bolting and
“lated Factors 0 O O O O O O O O O

The Eff

ect of Bulb Storage

and Related Factors. . . . . . . .

The Effect of Bulb Storage

Related Factors. . . . . . . . . .
seed PrOduction O O O O O O O O O 0 0

MATERIALS AND METHODS. . . . . . . .

RESULTS

Days to Sprout Emergence

AND DISCUSSION . . . . . . .

(Table 1) .

Days to Flowering (Table 2). . . . .

Height of the Primary Seedstalk (Table

Number
umbels
Florets

Seed Yi

of Leaves (Table 4) . . . . .
(TableS)..........
Bulb (Table 6). . . . . . . .
Unbel(Table7).......
Primary Unbel (Table 8) . . .
Secondary umbel (Table 9) . .

Secondary Plorets per Bulb (Table

Summary of the Floret Data. .
eld . . . . . . . . . . . .
Bulb (Table 11) . . . . . . .
umbel (Table 12). . . . . . .
Primary umbel (Table 13). . .
Secondary Umbel (Table 14). .
Secondary Seed Yield per Bulb
Seed Yield Summary. . . . . .

Weight per Seed. . . . . . . . . .

Unbel (Table 16). .
Primary umbel (Table 17). . .
Secondary umbel (Table 18). .
Summary . . . . . . . . . . .

iv

on Internal Morphology

on Seed Production and

(Table 15)

Page

vi

12
15

15
15
18
20
20
23
23
25
25
25
29
29
32
32
32
32
36
36
36
39
39
39
39
39

Number of Florets that Set Seed.

Bulb (Table 19)

Umbel (Table 20).

Primary Umbel (Table 21).

Secondary Umbel (Table 22). .
Secondary Florets that Set Seed

(Table 23). .
Summary . . . .

Number of Seeds per Floret

V. SUMMARY AND CONCLUSIONS.

”PEme 0 C O O O O O O O O 0

LITERATURE CITED. . . . . . .

Page

43
43
43
43
43

48
48
48
54
57

67

LIST OF TABLES
Table Page

1 Mean number of days to sprout emergence of 3 onion
inbred lines following 4 storage treatments. . . . . . . l6

2 Mean number of days to flowering of 3 onion inbred
lines following 4 storage treatments . . . . . . . . . . l7

3 Mean height (cm) of the primary seedstalks of 3 onion
inbred lines following 4 storage treatments. . . . . . . l9

4 Mean number of leaves per bulb for 3 onion inbred
lines fbllowing 4 storage treatments . . . . . . . . . . 21

5 Mean number of umbels per bulb for 3 onion inbred
lines following 4 storage treatments . . . . . . . . . . 22

6 Mean number of florets per bulb for 3 onion inbred
lines following 4 storage treatments . . . . . . . . . . 24

7 Mean number of florets per umbel for 3 onion inbred
lines following 4 storage treatments . . . . . . . . . . 26

8 Mean number of florets per primary umbel for 3 onion
inbred lines following 4 storage treatments. . . . . . . 27

9 Mean number of florets per secondary umbel for 2
onion inbred lines following 4 storage treatments. . . . 28

10 Mean number of secondary florets per bulb for 2
onion inbred lines following 4 storage treatments. . . . 30

11 Mean seed yield per bulb (grams) for 3 onion inbred
lines following 4 storage treatments . . . . . . . . . . 33

12 Mean seed yield (grams) per umbel for 3 inbred lines
following 4 storage treatments . . . . . . . . . . . . . 34

13 Mean seed yield (grams) per primary umbel for 3
. onion inbred lines following 4 storage treatments. . . . 35

14 Mean seed yield (grams) per secondary umbel for 2
onion inbred lines following 4 storage treatments. . . . 37

115 Mean secondary seed yield (grams) per bulb for 2
onion inbred lines following 4 storage treatments. . . . 38

vi

Table

16

17

18

19

20

21

22

23

24

25

26

27

Mean weight (mg) of seeds harvested from the umbels

of 3 onion inbred lines following 4 storage
treatmnts O O O O O O O I O O O O O O O O O O O 0

Mean weight (mg) of seeds harvested from primary umbels
of 3 onion inbred lines following 4 storage treatments .

Mean weight (mg) of seeds harvested from secondary
umbels of 2 onion inbred lines following 4 storage
treatments . . . . . . . . . . . . . . . . . . . .

Mean number of florets that set seed per bulb for 3

onion inbred lines following 4 storage treatments,
1976 O 0 O O O O O O O O O O O O O O O O O O O O 0

Mean number of florets that set seed per umbel for

3 onion inbred lines following 4 storage treatments,

1976 O O O O O O O O O C O O O O O O O 0 O O O O 0

Mean number of florets that set seed per primary
umbel for 3 onion inbred lines following 4 storage
ueawts ' 19 76 e o o o o o e e e o e o e e o e 0

Mean number of florets that set seed per secondary
umbel for 2 onion inbred lines following 4 storage
treamnts' 1976 e e e e e e e o e e e e e e o e e

Mean*number of secondary florets that set seed per
bulb for 2 onion inbred lines following 4 storage
treamnts ' 1976 O O O O O O O O O O O O O O O O 0

Mean number of seeds per floret per bulb for 3 onion
inbred lines following 4 storage treatments, 1976. .

Mean number of seeds per floret per umbel for 3
onion inbred lines following 4 storage treatments,
1976 O O O O I O O O O O O O O O O O O O O O O O 0

Mean number of seeds per floret per primary umbel

for 3 onion inbred lines following 4 storage treat-

mt" 1976. O O O O O O O O O O O O O O O O O O I

Mean nmber of seeds per floret per secondary unbel for 2
onion inbred lines following 4 storage treatments, 1976.

Analysis of variance: Effect of bulb storage treat-
ments on days to emergence, days to flowering, height

(cm) of the primary seedstalk, the total number of

leaves per bulb, and the total number of umbels per
bulb. 1975 and 1976 ”mined e e e o e e o e e o e 0

vii

Page

40

41

42

44

45

46

47

49

50

51

52

57

Table Page

A-2 Analysis of variance: Effect of bulb storage treat-
ments on number of florets for 3 M.S.U. onion inbreds,
1975 and 1976 combined . . . . . . . . . . . . . . . . .

A-3 Analysis of variance: Effect of bulb storage treatments
on the number of florets for 2 M.S.U. onion inbreds
(826 and 2399), 1975 and 1976 combined . . . . . . . . . S9

A—4 Analysis of variance: Effect of bulb storage treat-
ments on seed yield of 3 M.S.U. onion inbreds, 1975
and 19 76 mmined O O O O O O O O O O O O O I O O O O O 0 60

A95 Analysis of variance: Effect of bulb storage treat-
ments on seed yield of 2 M.S.U. onion inbreds (826
and 2399), 1975 and 1976 combined. . . . . . . . . . . . 61

A-6 Analysis of variance: Effect of bulb storage treat-
ments on the weight per seed for 3 M.S.U. onion
inbrek ' 1975 and 1976 Gabi-fled O O O O O O O O O O O 0 O 62

A-7 Analysis of variance: Effect of bulb storage treat-
ments on the weight per seed for 2 M.S.U. onion
inbreds (826 and 2399), 1975 and 1976 combined . . . . . 63

A-8 Analysis of variance: Effect of bulb storage treat-
ments on the number of florets that set seed for 3
M.S.U. onion inbreds, 1976 . . . . . . . . . . . . . . . 64

A-9 Analysis of variance: Effect<of bulb storage treat-
ments on the number of seeds per floret for 3 M.S.U.
onion inbred. ' 1976 O O O O O O O O 0 O O O O O O O 0 O O 65

A910 Analysis of variance: Effect of bulb storage treat-
ments on the number of florets that set seed and
seeds per floret for 2 M.S.U. onion inbreds (2399
and 826), 1976 . . . . . . . . . . . . . . . . . . . . . 66

viii

I . INTRODUCTION

Onion seed production has become a highly specialized operation,
especially since the advent of hybrids. Seed yields have fluctuated
and many years have been very low, largely due to pollination
problems.

One factor that has long been known to affect flowering and
seed yield is the storage temperature of the mother bulbs (Atkin and
Davis, 1954: Jones, 1927; Jones and Emsweller, 1939: Woyke and
Manczek, 1965). Extremely high or low temperatures may inhibit or
delay flower formation, while 11° to 12°C has been considered optimum
(Jones and Mann, 1963). Others have found that by varying storage
temperatures, especially from warm to cold, seed production was
enhanced (DeMille and Vest, 1976: Van Der Meer and Van Bennekom,
1969).

The objective of this study was to increase seed yield of three
M.S.U. onion inbreds by varying the storage temperatures and analyzing

the yield components.

II. LITERATURE REVIEW

Temperature during the "resting” and "dormant” stages (Abdalla
and Mann, 1963) of the onion bulb has a profound effect on the sub-
sequent growth and development of the onion plant. Storage tempera-
tures favorable for flowering and seed production are not appropriate
when storing sets for bulb production. Much of the early work on
storage temperature in onions was concerned with the control of

bolting in sets.

The Effect of Set Storage on Belting and Related Factors

Small sets, less than 1 gram, seldom bolt, but as the size
increases so does the percentage of seeders. Jones and Boswell
(1922) investigated the time of flower primordia differentiation.
They concluded that at College Park, Maryland, the flower primordia
were differentiated early in the spring regardless of whether the
sets were planted in the fall or early the following spring.

Boswell (1923) selected in August "early maturing” and "late
maturing“ sets for storage at 0°, 4.4°, or 10°C. On February 28,
two crates of sets were moved to 10° from the 0° and 4.4°C to Sim”?
late shipping and marketing conditions. All bulbs showing no growth
Tor-decay were planted in the field April 20. Sprouting data were

‘tamen during the storage period and growth responses were noted in

the field.

3

Boswell found that "early maturing" sets sprouted less readily
than ”late maturing” sets. Losses to decay were less in the "early"
than the "late" sets. Storage at 0°C resulted in the least loss.
Storage at 0°C followed by 6 weeks at 10°C resulted in much more
rapid growth than storage at 10°C throughout. Flower primordia dif-
ferentiation was inhibited but not prevented by storage at 0°C for
8 months. Six months exposure to 0°C was less inhibitory to floral
development than 8 months.

Thompson and.Smdth (1938) investigated the effect of temperature
and size on seed stalk and bulb development. The sets were stored
at -1.l°, 0°, 4.4°, 10°C, and in common storage (15.6°-20.1°C).

Prior to planting, the sets were graded into three sizes: large
(13/16 to 1 1/8 inch), medium (5/8 to 3/4 inch) and.small (3/8 to
5/8 inch).

They noted that the smallest sets produced the fewest seedstalks.
Sets stored at 4.4° and 10°C produced the highest percentage of seed-
stalks, while the smallest percentage was produced by sets at 15.6°-
20.1°C. The high temperature, however, resulted in loss due to
dehydration. The best storage temperature to maintain set quality
and inhibit bolting was -l.1° to 0°C.

Sets transferred during the last month of storage from -1.1° or
0°C to 4.4° and 10°C or from 15.6°-20.1°C to 0° or 10°C resulted in
an increase in the percentage of seedstalks and a decrease in bulb
yield. However, sets moved from 4.4° and 10°C to 15.6°-20.1°C
resulted in fewer seedstalks and a higher bulb yield.

Thompson and.Smdth (1938) conducted microscopic studies on the
apical meristems of the sets during storage to determine the time

flower primordia differentiated. In late March, flower primordia

4
were found only in the large sets stored at 0°, 4.4° and 10°C. Ten
days later flower primordia were found in medium size sets stored at
0°, and 4.4°C and 20 days later in those stored at 10°C. The small
sets showed no elongation of the growing point at any time prior to
planting in mid-May.

Thompson and Smith found the highest respiration rate was at
lS.6°-20.l°C and the lowest at 0°C, but there was no correlation
between respiration rate and the appearance of the flower primordia.

An intensive study of the effects of the environment on the
development of the onion plant was carried out in England in the
1940's and was summarized by Heath (1945). He reported sets bolted
less when stored at 0°-l.5°C for 22 weeks or for 8 weeks followed by
14 weeks at 12.S°C. However, 0°-l.5°C for the last 8 weeks of storage
resulted in a sudden flush of inflorescence initiation upon return
to normal temperatures (12.S°C for 6-7 weeks), and actually appeared
to increase bolting in the field. Medium storage temperatures (10°-
15°C) were the most favorable to flowering except for the accelerat-
ing effect of late cold storage.

The formation of leaf initials was also affected by storage
temperature. Fewer leaf initials were produced during storage at
0°-1.5°C for 22 weeks than at 12.S°C. The two treatments, 0°-1.5°C
for 22 weeks and 12.1°C for 14 weeks followed by 0°-l.5°C for 8
weeks, prevented leaf initiation during storage. The after-effect
of these two treatments was a tendency for sets to produce leaf
initials more rapidly on return to normal temperatures.

Heath suggested that the increase in flowering and more rapid

production of leaf initials after the warmecold-warm treatment

5
indicated that the onion plant was adapted to certain conditions
where a cold spell in January-February is frequent.

Hartsema (1947) studied leaf and flower formation in sets of the
variety Giant Zittau. The optimum storage temperature for flower
formation was 13°C. The greatest number of foliage leaves was
formed at storage temperatures of 17° to 20°C, but the length of the
foliage leaves was greatest one season after 13°C and the other season
after 23°C. Flower formation began first.at 5°-l3°C, later at 2°C
and 17°C, and a few at 20°C, but none at higher temperatures.

Hartsema found storage at a high (23° or 28°C) temperature followed
by storage at 5° or 9°C resulted in abundant flower formation. How-
ever, initial low storage temperature (5°, 9° or 13°C) followed by
23° or 28°C resulted in few or no flowers

Heath and Holdsworth (1950) reported on the influence of day
length and temperature on flowering of the onion plant. They noted
that, under apprOpriate conditions, once the terminal inflorescence
was initiated, more inflorescences could arise from axillary buds
apparently indefinitely. Prior to the appearance of the inflorescence
each bud produced at least three leaves.

They concluded there was a minimum plant size and there may be
a minimum leaf number prior to floral initiation. There was a maximum
temperature above which initiation could not take place. Day length
did not directly affect inflorescence initiation, but bulb formation
may destroy newly initiated inflorescences.

The Effect of Bulb Storage on Internal
Mogpholggy and Related Factors
Moodbury (1950) studied floral initiation in mature bulbs. He

set up a factorial experiment with the following factors: 2 varieties

6
(Ebenezer and Sweet Spanish), 3 storage temperatures (l.7°, 10° and
20.1°C), 2 photoperiods (normal day, i.e., 10 hours, and a 15 hour
day), 3 storage lengths (2, 4, and 8 months), and 3 greenhouse (grow-
ing) temperatures (10°-15.6°, 15.6°-20.l°, 20.1°-26.7°C). Following
the storage treatment the bulbs were planted in the greenhouses.
They were examined (by dissection) for flower primordia prior to
planting and subsequently every two weeks starting January 12 and
ending March 8.

A few flower primordia were found in early January for each of
the treatments, and these developed rapidly in the next 8 weeks.

A greater rate of initiation was noted in Sweet Spanish. Bulbs grown
under the 15 hr photoperiod produced a significantly greater number
of flower primordia, partly because light seemed to prevent rotting
of Sweet Spanish in the warm greenhouse. Bulbs grown at 10° to
15.6°C produced the greatest number of flower primordia while almost
none were initiated in bulbs growing at 20.l° to 26.7°C. Floral
initiation in bulbs grown at 15.6° to 20.1°C was much less than at
10° to 15.6°C. The most effective storage temperature to induce
floral initiation was 10°C, significantly fewer were initiated at
l.7°C, and 20.1°C induced the least. The length of storage had no
significant effect on the development of the floral axis. Seedstalk
formation took place only in the 10°-15.6°C greenhouse.

Abdalla and Hahn (1963) studied the effect of storage temperature
on bulb “rest." Using the cultivar Excel, they found bulbs stopped
initiating leaves at the apex approximately three weeks before
harvest. Bulbs resumed initiating leaves (approximately 5 weeks

later) near the beginning of storage at 15°C and continued at a rate

7
of approximately one leaf every two weeks. In bulbs stored at 0° or
30°C, the rate of initiation was half that at 15°C.

Elongation of the inner leaves (the sprout) began after about
two weeks of storage at 15°C. However, six weeks later the sprouts
were not externally visible. No elongation was observed at 0° or
30°C during a 10 week examination period.

In another experiment (Abdalla and Mann, 1963), bulbs of Excel
and Australian Brown were stored at 0°, 5°, 10°, 15°, 20°, 30°, and
40°C. Bulbs were removed from storage after 2, 4, 8, and 16 weeks,
placed in moist sphagnum at 15°C, and checked for sprouting and
rooting. They found the 5°, 10°, and 15°C treatments for any storage
period resulted in the most rapid sprout emergence. Sprouts emerged
the least rapidly after the 0° or 30°C treatments. The longer the
bulbs were stored, the quicker they sprouted. Thus, bulb rest was
not intensified by storage.

Abdalla and Mann found that root emergence always preceded
sprouting. Root emergence occurred simultaneously and most rapidly
after the 5°, 10° or 15°C treatments. However, after a period of
growth, root lengths and weights were greater for bulbs stored at
15° than at 5° or 10°C.

Using the cultivar Excel, they studied the extent of mitosis in
the shoot apex during the rest period. Mitotic figures were present
. from the cessation of leaf initiation (in the field) through curing
and storage. However, the frequency decreased in storage, especially
at 0° and 30°C. At no time‘was the shoot apex inactive.

In a recent study Ward (1967) stored onion bulbs for 9 months
at 2°, 7.5°, 15° and 25°C and 70% R.H. He found losses due to

desiccation increased with temperature, but less than 20% of the

8
weight loss was due to respiration. Respiration rates of bulbs
transferred from 2° to 25°C were higher from February (time of transfer)
onwards than bulbs stored continuously at 25°C. Conversely, bulbs
transferred from 25° to 2°C respired less from February onwards than
those kept at 2°C. Sprouting, measured at the final assessment in
June, was highest at 7.5° and 15°C and lowest at 2°C. Total weight
loss was above 45% in all storage treatments except at 2°C, where it
was 12%.
The Effect of Bulb Storage on Seed
Production and Related Factors

Jones (1927) studied the relationship between storage tempera-
tures and seed yield. Using the cultivar Ebenezer, a poor seeder,
he stored the mother bulbs for 4 months at 3.5°, 7.5°, 11°-12°,
16°-22°, 30°C, and in common storage. He found bulbs stored at 7.5°
and 11°-12°C flowered earliest, produced the highest seed yields, and
the fewest vegetative stalks.

Jones and Emsweller (1939) reported the effect of storage tempera-
ture, bulb size, spacing, and time of planting on the production of
onion seed. Bulbs stored at 8° and 12°C were first to flower and
ripen seed, while those stored at 30°C were the latest. Bulbs stored
at 12°C produced the greatest number of umbels and the best seed
yield. Both the higher and lower storage temperatures reduced seed
yield.

In another experiment Jones and.Emsweller used the same storage
treatments but three different cultivate: a free seeding strain of
Ebenezer, Yellow Globe Danvers, and Strain #15-8. The 12°C treatment
resulted in the earliest flowering and 30°C the latest. For all

cultivars, 12°C resulted in the most umbels, but not significantly

9
more than l6°-22°C or common storage. The fewest umbels resulted
after the 3.6°, 8°, and 30°C treatments. The 30°C treatment
resulted in the lowest seed yield for Ebenezer and Strain #15-8,
while both 30°C and 8°C treatments resulted in a low yield for Yellow
Globe Danvers. There was a significant interaction between cultivars
and storage.

Jones and Emsweller (1939) also reported an increase in the
number of umbels and seed yield per plant with an increase in bulb
size (eight different sizes ranging from 15 to 90 grams). They also
found an increase in seed yield per plant as the space between bulbs
was increased (3, 4, 6, 8, and 12 inch spacings). Furthermore, later
planting dates (1st planting December 7, December 27, January 1,
January 22, January 20, February 15, March 2) of Yellow Globe Danvers
delayed seed maturity and decreased seed yield.

Atkin and Davis (1954) gave the cultivar Australian Brown 4
storage treatments (0°, 10°, 20°C and common storage) and planted
them.at 4 times (November 16, December 15, February 12, March 24)
throughout the winter. They reported the earliest planting resulted
in the earliest flowering and bulbs from the 10°C storage and common
storage flowered first. Earlier planting yielded more labels, but
regardless of the date of planting, 10°C and common storage gave the
greatest number of umbels. Early planting with a 10°C storage treat—
mend yielded the highest total number of umbels.

Delayed planting resulted in fewer florets per umbel. Storage
treatments appeared to have a minimum influence on the number of
florets per umbel. The 0°C treatment was significantly poorer than

10°, 20°C or comon storage.

10

Delayed planting resulted in lower seed yields. The 10°C and
common storage treatments resulted in the highest seed yields, while
0°C and 20°C were lower.

Woyke and.Manczek (1965) obtained the greatest number of seed
stalks and seed yield from bulbs stored at 8°-12°C but reported that
seed stalk number and seed yield per bulb were not closely correlated.

Van Der Heer and Van Bennekom (1968) observed differences in
seed yield between 3 selections of Rijnsburger onions because one of
the selections produced more seed stalks. Comparing different storage
treatments, they found a constant 26°C resulted in almost no seed
production. The most seed was produced when bulbs were stored at
12°C for 2-4 months followed by storage at 0°C. Storage at 0°C,
preceded and followed by storage at 12°C, also gave good results, as
did constant 12°C storage.

DeHille and Vest (1975, 1976) stored onion bulbs (Trapp's
Downing Yellow Globe) at 7°C for 6 months, at 2°C for 3 months fol-
lowed by 7°C for 3 months, and at 7°C for 3 months followed by 2°C for
3 months. They found storage at 7°C throughout resulted in the
earliest flowering. The 2°-7°C treatment delayed flowering longer
than the 7°-2°C treatment, but this difference was not significant.
The highest seed yield resulted from the 7°-2°C treatment, while seed
yield from the 7°C and 2°-7°C treatments was not different. There
were no differences in the number of seedstalks. The number of seeds
per plant was greatest after the 7°-2°C treatment, while there was
no difference between the 7°C or 2°-7°C treatments. The mmber pf
seeds per umbel was lowest for the 7°C treatment and highest for the
7°-2°C and 2°-7°C treatments. Individual seed weight was lowest for

the 7°C treatments and highest for the 7°-2°C and 2°-7°C treatments.

11
The seed stalks were slightly taller after the 2°-7°C and 7°-2°C
treatments than after the 7°C treatment. The 2°-7°C treatment

yielded the least number of leaves.

Seed Production

Mital and Srivastava (1964), using open pollinated cultivars,
Pusa Red and Early Grano, investigated the relationships between the
number of seed stalks, seed yield, and seed quality. The bulbs were
organized into different tiller groups according to the number of
seed stalks.

They found seed yield per plant increased with an increase in
the number of seed stalks. For Pusa Red, seed size decreased as the
number of seed stalks increased, but the seed size did not vary for
Early Grano. Seed germination generally decreased with tillering
increase. When the seeds were planted and subsequent bulb size
compared, there appeared to be a negative correlation between the
seed stalk number and the bulb size.

Prokhorev and Khomyakov (1972) determined the number of seeds
in an inflorescence for onion plants flowering on July 16, 20, 25,
30, and August 5. They found the earlier flowering plants produced a

greater number of high quality seeds.

III. MATERIALS AND METHODS

In 1974 and 1975, onion bulbs of three M.S.U. inbreds (661-20,
826, and 2399) were grown at the M.S.U. muck farm using standard
cultural practices. The cured bulbs were sorted and graded for
uniformity within each inbred line and given the following storage
treatments:

1. 2°C 24 wk

2. 2°C 12 wk-10°C 12 wk

3. 10°C 12 wk-2°C 12 wk

4. 10°C 24 wk

5. 10°C 6 wk-2°C 18 wk

6. 2°C 6 wk-lO’C 18 wk

7. 10°C 18 wk-2°C 6 wk

8. 2°C 18 wk-lO’C 6 wk

Fifteen bulbs per treatment were used the first year and 30 bulbs
the second. The bulbs for each treatment were divided into 3 sub-
plots, i.e., there were 5 bulbs per subplot in 1975 and 10 bulbs per
subplot in 1976. The experimental design was randomized complete
block with 2 replications. Only treatments 1 through 4 were repeated
the second year.

The following data were collected:

a) The days to sprout emergence from date of planting.

b) The days to flowering, i.e., opening of the first floret.

12

13

This umbel was tagged and called the primary umbel. All other
umbels were called secondary.

c) The height of the primary seedstalk.

d) The number of umbels per bulb.

e) The number of leaves per bulb.

f) The number of florets; umbels were harvested from one sub-

plot per treatment and the florets counted.

9) Seed yield: two subplots per treatment were used for the
seed yield data in 1975 and one subplot in 1976.

h) Florets that set seed; in 1976 only, umbels were harvested
(just before the seed capsules shattered) from one sub-
plot per treatment and the florets that set seed were
counted.

i) The weight per seed; 100 seeds per primary umbel and
secondary ulbels were counted and weighed.

j) The number of seeds per floret: 1976 only.

Seed was harvested and thrashed by hand. Light seed and chaff
were floated from the good heavy seed. Seeds from the primary umbel
were kept separate and seeds from the secondary umbels were bulked
together for each plant.

Plot means were subjected to analysis of variance each year and
(for treatments 1 through 4) for both years combined. Variance due
to subplots was not included in the error variance until a preliminary
F-test had been performed (Sokal and Rohlf, p. 266-267). Tukey's
hsd procedure was used for mean separation at the 5! level (Steel and

Torrie, p. 109-110).

14
Only the combined data of the two years are presented and dis-

cussed in the text. All on tables may be found in the Appendix.

IV. RESULTS AND DISCUSSION

Days to Sprout Emergence (Table 1)

Storage at 2°C for 24 weeks delayed emergence by approximately
2 days. Inbred 2399 emerged first, followed by inbred 826, 2 days
later, and inbred 661-20, 12 days later. .

Storage at 2°C for 24 weeks delayed the emergence of inbreds
826 and 2399. However, inbred 661-20 responded in an opposite manner
and 10°C for 24 weeks delayed emergence. The combination treatments
had little effect on inbreds 2399 or 826, but 10°C for the second 12
weeks of storage delayed the emergence of inbred 661-20 as much as
10°C for the whole 24 weeks.

This difference in response suggests the inbreds may require

special handling to achieve optimum results in a breeding program.

Days to Flowering_(Table 2)

Storage at 10°C for 24 weeks or 10°C for the second 12 weeks
resulted in the earliest flowering. The treatment, 2°C for 24 weeks,
delayed flowering by approximately 5 days, while storage at 2°C for
the second 12 weeks delayed flowering by approximately 2.5 days.
These trends agree with earlier reports (Atkin and Davis, 1954;
DeHille and vest, 1975; Jones, 1927: Jones and Emsweller, 1939).

Both inbreds 2399 and 826 flowered at the same time and 6 days before

inbred 661-20.

15

16

Table 1. Mean number of days to sprout emergence of 3 onion inbred
lines following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 26.8f 26.4f 32.09 28.4
b b a B
2°C 12 wk— 19.9f 24.5g 35.5h 26.6
10°C 12 wk a ab be A
10°C 12 wk- 22.7f 25.2f 32.89 26.9
2°C 12 wk a ab ab A
10°C 24 wk 20.5f 23.1f 36.2g 26.6
a a c A
Inbred means 22.5F 24.86 34.1H

 

IHeans in columns followed by the same letter (a to b) and
means in rows followed by the same letter (f to h) are not signifi-
cantly different at the 5‘ level.

17

Table 2. Mean number of days to flowering of 3 onion inbred lines

following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 78.8f 80.0f 83.29 80.7
b b a C
2°C 12 wk- 72.7f 71.8f 81.69 75.4
10°C 12 wk a a a A
10°C 12 wk- 74.9f 76.8f 81.49 77.7
2°C 12 wk a b a B
10°C 24 wk 71.5f 72.2f 81.39 75.0
a a a A
Inbred means 74.5F 75.2F 81.9G

 

*Heans in columns followed by the same letter (a to c) and
means in rows followed by the same letter (f to g) are not signifi-
cantly different at the 5% level.

18

The storage treatments had no significant effect on inbred
661-20, but 2°C for 24 weeks significantly delayed flowering of
inbred 2399 more than any other treatment. Either 2°C for 24 weeks
or 2°C for the second 12 weeks delayed flowering of inbred 826.

The difference between the flowering dates of inbred 661-20
and the two other inbreds might cause problems for hybrid seed pro-
duction. A possible solution would be to store inbred 661-20 at 10°C
for 24 weeks and inbreds 2399 and 826 at 2°C for 24 weeks so that the
flowering dates would be more likely to coincide. This method of
altering flowering dates to promote “nicking” was suggested by

Atkin and Davis (1954).

Height of the Primary Seedstalk (Table 3)

The height of the seedstalks is important for two reasons:

1) they comprise a major amount of the photosynthetic area for the
seed plant and 2) tall seedstalks have a greater tendency to lodge
and become tangled with each other making cultural practices diffi-
cult. Where hybrid seed is being produced, separation of male and
female lines is essential.

The optimum height is not known, but higher seed yields have
been associated with medium storage (7° to 12°C) treatments (Jones,
1927: Jones and Emsweller, 1939) and with combination warm-cold
treatments (DeMille and Vest, 1976: Van Der Meer and Bennekom, 1969).
DeHille and Vest (1976) reported the seedstalks were slightly taller
after the combination treatments (2°C lst half-7°C 2nd half, and
7°C lst half-2°C 2nd half) than after the 7°C treatment.

In this study, bulbs stored at 10°C for 24 weeks produced the

shortest primary seedstalks, while storage at 10°C for 12 weeks

19

Table 3. Mean height (cm) of the primary seedstalks of 3 onion

inbred lines following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 97.6h 80.19 66.5f 81.4
c ab a B
2°C 12 wk- 93.0h 82.79 67.4f 81.0
10°C 12 wk b b a B
10°C 12 wk- 95.8h 81.69 70.4f 82.6
2°C 12 wk bc ab a B
10°C 24 wk 87.2h 78.39 69.1f 78.2
a a a A
Inbred means 93.4H 80.7G 68.4F

 

xMeans in columns followed by the same letter (a to c) and '
means in rows followed by the same letter (f to h) are not signifi-
cantly different at the 5% level.

20
followed by 2°C for 12 weeks resulted in the tallest primary seed-
stalks. The latter treatment also produced the highest seed yield.
Inbred 2399 produced the tallest primary seedstalks, and inbred
661-20 the shortest.

Inbred 661-20 was not significantly affected by the storage
treatments, but 2°C for 24 weeks did result in the shortest primary
seedstalks. However, this treatment resulted in the tallest primary
seedstalks for inbred 2399 and an intermediate height for inbred 826.
The combination treatments resulted in an intermediate height for
inbred 2399, but inbred 826 produced the tallest primary seedstalks

after storage at 2°C for 12 weeks followed by 10°C for 12 weeks.

Number of Leaves (Table 4)

Storage of the bulbs at 10°C for 24 weeks or at 10°C for the
first 12 weeks resulted in the highest number of leaves per plant
and this agrees with the findings of DeMille and Vest (1976). Inbred
2399 had the most leaves, inbred 661-20 the least, and inbred 826 an
intermediate number.

The storage treatments had no effect on inbred 661-20. For
inbreds 2399 and 826, 2°C for 24 weeks resulted in the fewest leaves,
while 10°C for 24 weeks resulted in the greatest number and the com—

bination treatments resulted in an intermediate number.

Umbels (Table 5)

Jones and Emsweller (1939) reported bulbs stored at 8° and 12°C
resulted in more umbels per plot and a higher seed yield. However,
DeMille and Vest (1976) found no significant differences between the
number of umbels per plant, but a significantly greater seed yield

after the 7°C lst half-2°C 2nd half treatment.

21

Table 4. Mean number of leaves per bulb for 3 onion inbred lines
following 4 storage treatments

 

 

 

Inbredx

Storage Treatment
treatments 2399 826 661-20 means
2°C 24 wk 12.9h 8.99 5.1f 9.0

a a a A
2°C 12 wk- 14.7h 9.89 4.9f 9.8
10°C 12 wk b ab a AB
10°C 12 wk- 14.7h 10.09 5.3f 10.0
2°C 12 wk b ab a AB
10°C 24 wk 15.5h 11.39 5.3f 10.7

b b a B
Inbred means 14.4H 10.0G 5.2F

 

xMeans in columns followed by the same letters (a to b) and
means in rows followed by the same letter (f to h) are not signifi-
cantly different at the 5‘ level.

22

Table 5. Mean number of umbels per bulb for 3 onion inbred lines

following 4 storage treatments

 

 

 

Inbred;
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 2.619 1.48fg 1.00f 1.69
a a a A
2°C 12 wk- 3.479 1.68f 1.00f 2.05
10°C 12 wk b a a B
10°C 12 wk- 3.129 1.38f 1.00f 1.83
2°C 12 wk b a a AB
10°C 24 wk 4.25h 2.499 1.04f 2.59
c b a C
Inbred means 3.36H 1.766 1.01F

 

xMeans in columns followed by the same letter (a to c) and
means in rows followed by the same letter (f to h) are not signifi-
cantly different at the 5‘ level.

23

In this study a variation in the number of umbels per plant was
noted. Storage at 10°C for 24 weeks resulted in the most umbels,
while 2°C for 24 weeks or 2°C for the second 12 weeks resulted in
the fewest. If 2°C was given for the first 12 weeks, it resulted in
an intermediate number. Inbred 2399 produced the most umbels, inbred
826 half as many, and inbred 661-20 only one per bulb.

Inbred 2399 produced the fewest umbels after storage for 24
weeks at 2°C and the most after storage for 24 weeks at 10°C, while
the combination treatments resulted in an intermediate number. For
inbred 826, exposure to 2°C at any time during storage resulted in
the fewest umbels, while 10°C for 24 weeks resulted in one more
umbel per bulb. The storage treatments had no effect on inbred

$61-20.

Florets

Bulb (Table 6)

Although the storage treatments had no significant effect on the
mean number of florets per bulb, the 2°C 12 week-10°C 12 week treat-
ment resulted in the greatest number of florets and the 2°C 24 week
treatment the smallest. Individually, inbred 2399 produced the
most florets per bulb, followed by inbreds 826 and 661-20.

Storage of inbred 826 at 10°C for 24 weeks or at 10°C for the
second 12 weeks resulted in the most florets per bulb. The treat-
ments had little effect on inbreds 2399 or 661-20. However, since
661-20 produced only 1 umbel per bulb, the next section gives a

better analysis of the number of florets per bulb for that inbred.

24

Table 6. Mean number of florets per bulb for 3 onion inbred lines

following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 1303.5h 843.89 504.5f 883.9
a a a A
2°C 12 wk- 1464.09 1232.29 316.0f 1004.1
10°C 12 wk a b a A
10°C 12 wk- 1408.8h 1003.59 467.8f 960.0
2°C 12 wk a ab a A
10°C 24 wk 1375.59 1201.29 354.5f 977.1
a b a A
Inbred means 1388.0H 1070.2G 410.7F

 

xMeans in columns followed by the same letter (a to b) and
means in rows followed by the same letter (f to h) are not signifi-
cantly different at the 5% level.

25
Umbel (Table 7)

Storage at 2°C for 24 weeks or at 2°C for the second 12 weeks
resulted in the greatest number of florets per umbel, while storage
at 10°C for 24 weeks resulted in the fewest florets per umbel.
Inbred 826 produced the greatest number of florets per umbel.

The treatments had no significant effect on inbred 2399, but
inbred 826 produced the fewest florets per umbel after storage at
10°C for 24 weeks. Storage of inbred 661-20 at 10°C for 24 weeks
or at 10°C for the second 12 weeks resulted in the fewest florets
per umbel (therefore also the fewest florets per bulb since it only

produced 1 umbel).

Primary Umbel (Table 8)

Storage at 2°C for 24 weeks or at 2°C for the second 12 weeks
resulted in the highest number of florets per primary umbel. Inbred
661-20 produced the fewest florets per primary umbel, inbred 2399
an intermediate number, and inbred 826 the most.

The storage treatments did not significantly affect inbred 2399.
Inbred 826 produced the most florets per primary umbel after the
combination treatments, while 10°C for 24 weeks resulted in the
least florets. Storage of inbred 661-20 at 2°C for 24 weeks or for

the second 12 weeks resulted in the most florets per primary umbel.

Secondary Umbel (Table 9)
The treatments had no significant effect on the number of

florets per secondary umbel.

26

Table 7. Mean number of florets per umbel for 3 onion inbred lines

following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 466.0f 657.59 504.5f 542.7
a b c B
2°C 12 wk- 406.2f 681.29 316.0f 467.8
10°C 12 wk a b a B
10°C 12 wk- 451.5f 703.09 467.8f 540.8
2°C 12 wk a b be B
10°C 24 wk 345.6: 450.2: 354. 5f 383. 2
a a ab A
Inbred means 417.2F 623.06 410.7F

 

xMeans in columns followed by the same letter (a to c) and
means in rows followed by the same letter (f to 9) are not signifi-
cantly different at the 5‘ level.

27

Table 8. Mean number of florets per primary umbel for 3 onion inbred
lines following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 525.5f 715.29 504.5f 581.7
a ab b B
2°C 12 wk- 490.89 833.5h 316.0f 546.8
10°C 12 wk a b a AB
10°C 12 wk- 581.5f 822.09 467.8f 623.8
2°C 12 wk a b b B
10°C 24 wk 448.8f >620.09 354.5f 474.4
a a ab A
Inbred means 511.66 747.7H 410.7F

 

xMeans in columns followed by the same letter (a to b) and
means in rows followed by the same letter (f to h) are not signifi-
cantly different at the St level.

28

Table 9. Mean number of florets per secondary umbel for 2 onion
inbred lines following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 means
2°C 24 wk 437.2 382.5 409.8
2°C 12 wk- 374.5 501.0 437.8
10°C 12 wk
10°C 12 wk- 366.5 389.8 378.2
2°C 12 wk
10°C 24 wk 313.5 323.5 318.5
Inbred means 372.9 399.2

 

xMeans in columns and means in rows are not significantly
different at the 5‘ level.

29
§ggggg§£3fiFlorets per Bulb (Table 10)

Storage at 2°C for 24 weeks or at 2°C for the last 12 weeks
resulted in the fewest secondary florets (florets from all secondary
umbels) per bulb. Inbred 2399 produced the most secondary florets
per bulb.

Inbred 826 produced the most secondary florets per bulb after
storage at 10°C for 24 weeks or at 10°C for the second 12 weeks.

The treatments affected 2399 very little.

Summary of the Floret Data

The inbreds responded quite differently from each other. Inbred
661-20 produced only one umbel per bulb and storage at 2°C for 24
weeks or at 2°C for the second 12 weeks resulted in a significantly
greater number of florets per umbel and therefore per bulb.

Storage of inbred 826'at 2°C for 24 weeks resulted in 1.48
umbels and the fewest florets per bulb. Storage at 2°C for the first
12 weeks resulted in approximately the same number of umbels (1.68),
but a significantly greater number of florets per bulb. If 2°C was
given for the second 12 weeks, inbred 826 again produced approximately
the same number of umbels (1.38), but an intermediate number of
florets per bulb. For the above three treatments, the number of
florets per umbel did not vary significantly. The 10°C 24 week
treatment resulted in 2.49 umbels per bulb, but this increase of
l umbel did not increase the total florets per bulb as might have
been expected. It simply resulted in significantly fewer florets per
umbel. Thus, while the number of umbels per bulb and the number of
florets per umbel were interrelated, the storage treatments had a

direct effect on each component independently.

30

Table 10. Mean number of secondary florets per bulb for 2 onion
inbred lines following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 means
2°C 24 wk 778.09 128.5f 453.2
a a A
2°C 12 wk- 973.29 398.5f 685.8
10°C 12 wk a ab AB
10°C 12 wk- 827.59 181.5f 504.5
2°C 12 wk a a A
10°C 24 wk 998.29 581.2f 789.7
a b B
Inbred means 894.26 322.4F

 

xMeans in columns followed by the same letter (a to b) and
means in rows followed by the same letter (f to g) are not signifi-

cantly different at the 5% level.

31

This complex interaction was observed for the number of florets
per primary umbel also. After storage at 10°C for 24 weeks inbred
826 produced the most umbels per bulb and fewest florets per primary
umbel. The combination treatments resulted in approximately 1.5
umbels per bulb, and the most florets per primary umbel. The 2°C
24 week treatment also resulted in approximately the same number of
umbels per bulb (1.48), but an intermediate number of florets per
primary umbel.

Inbred 2399 produced 4.25 umbels per bulb after the 10°C 24
week treatment while storage at 2°C for 24 weeks resulted in 2.69
umbels. The combination treatments resulted in approximately 3.29
umbels per bulb. Although for inbred 2399 the number of umbels per
bulb varied dramatically, the total florets per bulb did not. The
florets were simply distributed over the number of umbels.

The storage treatments did not significantly affect the number
of florets per umbel or primary umbel for inbred 2399. However, as
the number of umbels per bulb increased, the number of florets per
umbel or primary umbel decreased.

The number of florets per secondary umbel did not vary signifi-
cantly for either inbred 826 or 2399. However, when the number of
umbels per bulb was the largest, the number of florets per secondary
umbel was the smallest.

Atkin and Davis (1954) reported the Excel cultivar showed some
differences in the number of florets per umbel according to different
storage treatments, but these were not significant. In another
experiment they used the cultivar Australian Brown and collected
primary umbels. They reported storage treatments had a minimum

influence on the number of florets per umbel, but 0°C was significantly

32
poorer than 10°, 20°C or common storage. This does not agree with

the present study and is probably due to the different cultivar used.

Seed Yield

 

Bulb (Table 11)

 

The storage treatments did not significantly affect the total
seed yield per bulb. The 10°C 12 week-2°C 12 week treatment did
result in the best yield and this agrees with earlier studies
(DeMille and Vest, 1976: Van Der Meer and Van Bennekom, 1969; Woyke
and Manczek, 1965). Inbred 2399 produced the most seed and inbred

661-20 the least.

Umbel (Table 12)

Storage for the first 12 weeks at 10°C followed by 12 weeks at
2°C resulted in a significantly greater seed yield per umbel, while
24 weeks at 10°C resulted in the smallest yield. DeMille and Vest
(1976) reported similar results. Storage at 2°C for the first 12
weeks or for 24 weeks had an intermediate effect. Inbred 661-20

produced the least seed per umbel.

Primary Umbel (Table 13)

Storage at 10°C for 12 weeks followed by 12 weeks at 2°C
resulted in the highest seed yield per primary umbel, while 10°C for
24 weeks resulted in the lowest yield. Inbred 661-20 produced the
smallest amount of seed per primary umbel.

Storage of inbreds 2399 and 661-20 at 10°C for 24 weeks resulted
in the lowest yield, while 10°C for the first 12 weeks only resulted

in the highest yield. The treatments had less effect on inbred 826.

33

Table 11. Mean seed yield per bulb (grams) for 3 onion inbred lines
following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 7.8905h 4.66729 1.9696f 4.8424
2°C 12 wk- 9.95689 4.2232f 2.0608f 5.4136
10°C 12 wk
109C 12 wk- 10.99839 4.6520f 2.5392f 6.0632
2°C 12 wk
10°C 24 wk 9.3509h 4.67399 1.1458f 5.0569
Inbred means 9.5491H 4.55416 1.9288?

 

xMeans in columns and means in rows followed by the same
letter (f to h) are not significantly different at the 5% level.

34

Table 12. Mean seed yield (grams) per umbel for 3 inbred lines

following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 3.22729 3.34199 1.9696f 2.8462
b be ab BC
2’C 12 wk— 3.08869 2.83209 2.0608f 2.6605
10°C 12 wk ab ab b B
10°C 12 wk- 3.66179 3.72179 2.5392f 3.3075
2°C 12 wk b c b C
10°C 24 wk 2.28449 2.20609 1.1458f 1.8787
a a a A
Inbred means 3.06556 3.02546 1.9288F

 

xMeans in columns followed by the same letter (a to c) and
means in rows followed by the same letter (f to 9) are not signifi-
cantly different at the 5% level.

35

Table 13. Mean seed yield (grams) per primary umbel for 3 onion
inbred lines following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 3.72309 3.67699 1.9696f 3.1232
a a ab 8
2°C 12 wk- 3.95129 3.45769 2.0608f 3.1565
10°C 12 wk ab a ab B
10°C 12 wk- 4.68559 3.92369 2.5392f 3.7161
2°C 12 wk b a b C
10°C 24 wk 3.15759 3.15609 1.1458f 2.4864
a a a A
Inbred means 3.87956 3.5535G 1.9288F

 

xMeans in columns followed by the same letter (a to b) and
means in rows followed by the same letter (f to g) are not signifi-
cantly different at the 5% level.

36
Secondary_pmbel (Table 14)

Storage at 2°C for 24 weeks or at 2°C for the second 12 weeks
resulted in the highest seed yield per secondary umbel. Bulbs
stored at 10°C for 24 weeks produced the lowest yields, while those
at 10°C for the second 12 weeks produced an intermediate yield.

Inbred 2399 produced the most seed per secondary umbel.

Secondary Seed Yield per Bulb (Table 15)
The storage treatments had little effect on the secondary seed
yield (yield from all secondary umbels) per bulb. Inbred 2399 pro-

duced the most secondary seed per bulb.

Seed Yield Summary

The 10°C 12 week-2°C 12 week treatment resulted in the highest
seed yield per bulb, but the number of umbels and florets per bulb
was intermediate. Thus, the highest number of umbels per bulb (after
the 10°C 24 week treatment) did not increase the seed yield as might
have been expected. The 10°C 12 week-2°C 12 week treatment resulted
in a high number of florets per umbel and a significantly higher seed
yield per umbel. Storage at 10°C for 24 weeks resulted in the fewest
florets and lowest seed yield per umbel.

It is apparent the 10°C 12 week-2°C 12 week treatment was most
favorable for seed production. The treatment reduced the number of
umbels and increased the florets and seed yield per umbel. There-
fore, it appears there is an optimum number of umbels and florets per

umbel that results in the best seed yield.

37

Table 14. Mean seed yield (grams) per secondary umbel for 2 onion
inbred lines following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 means
2°C 24 wk 2.8564f 2.6938f 2.7751
a b B
2’C 12 wk- 2.6964f 1.6553f 2.1758
10°C 12 wk a ab AB
10°C 12 wk- 3.1206f 2.2823f 2.7014
2’C 12 wk a ab B
10°C 24 wk 2.0027f 1.0572f 1.5300
a a A
Inbred means 2.66906 1.9221?

 

xMeans in columns followed by the same letter (a to b) and
means in rows followed by the same letter (f to g) are not signifi-
cantly different at the 5‘ level.

38

Table 15. Mean secondary seed yield (grams) per bulb for 2 onion

inbred lines following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatments 2399 826 means
2°C 24 wk 4.16879 0.99le 2.5801
29C 12 wk- 6.00809 0.7394f 3.3737
10’6 12 wk
lO’C 12 wk- 6.31289 0.7259f 3.5194
2°C 12 wk
10‘C 24 wk 6.19349 1.509lf 3.8512
Inbred means 5.67076 0.9915F

 

*Means in columns and means in rows followed by the same
letter (f to 9) are not significantly different at the 5% level.

39

Weight per Seed

Unbel (Table 16)
The storage treatments had no significant effect on the weight
of seeds harvested from umbels. This result agrees with DeMille and

Vest (1976) .

Primary Umbel (Table 17)

The storage treatments did not affect the mean weight of seeds
harvested from primary umbels. Inbreds 2399 and 661-20 had the
largest seeds and inbred 826 the smallest.

The 2°C treatments resulted in the heaviest seeds from a primary
unbel for 2399 while storage at 10°C for 24 weeks resulted in seeds
that were approximately . 3 mg lighter. The treatments did not
affect inbred 826. For inbred 661-20, storage at 2°C for the first
12 weeks resulted in the heaviest seeds while 2°C for the second 12

weeks resulted in seeds that were .4 m9 lighter.

 

Seconggx Unbel (Table 18)

The storage treatments had no significant effect on the weight
of seeds harvested from secondary unbels.

For inbred 2399, seeds from primary or secondary umbels weighed
the same, but for inbred 826 the seeds from secondary umbels were

.4 m9 lighter.

Stu-nag

The treatments did not affect the mean weight of a seed. However,
the inbreds did respond differently, e.g., the 10°C 12 week-2°C 12
week treatment resulted in the heaviest seeds from the primary umbels

f01': inbred 2399 and the lightest for inbred 661-20. It is apparent

40

Table 16. Mean weight (mg) of seeds harvested from the umbels of 3
onion inbred lines following 4 storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 4.09 3.Sf 3.89 3.8
2°C 12 wk- 3.9g 3.4f 4.19 3.8
10°C 12 wk
10°C 12 wk- 4.09 3.5f 3.7f9 3.7
2°C 12 wk
10°C 24 wk 3.7fg 3.5f 3.99 3.7
Inbred means 3.96 3.5F 3.96

 

xMeans in columns and means in rows followed by the same
letter (f to g) are not significantly different at the 5% level.

41

Table 17. Mean weight (mg) of seeds harvested from primary umbels
of 3 onion inbred lines following 4 storage treatments

 

 

 

Inbredx

Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 4.09 3.5f 3.89 3.8

b a ab
2°C 12 wk- 3.99 3.6f 4.19 3.9
10°C 12 wk ab a b
10°C 12 wk- 4.09 3.5f 3.7f 3.7
2°C 12 wk b a a
10°C 24 wk 3.6f 3.7f9 3.99 3.7

a a ab
Inbred means 3.96 3.6? 3.96

 

xMeans in columns followed by the same letter (a to b) and
means in rows followed by the same letter (f to g) are not signifi-
cantly different at the 58 level.

42

Table 18. Mean weight (m9) of seeds harvested from secondary umbels

of 2 onion inbred lines following 4

storage treatments

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 means
2°C 24 wk 4.09 3.4f 3.7
2°C 12 wk- 3.9g 3.2f 3.6
10°C 12 wk
10°C 12 wk- 4.09 2.9f 3.4
2’6 12 wk
10°C 24 wk 3.99 3.2f 3.6
Inbred means 4.06 3.2?

 

xMeans in columns and means in rows followed by the same
letter (f to g) are not significantly different at the 5‘ level.

43
that, to achieve optimum results, the inbreds would have to be

handled differently.

Number of Florets that Set Seed

Bulb (Table 19)

Although the storage treatments had no significant effect,
storage at 10°C for 12 weeks followed by 2°C for 12 weeks resulted
in a greater number of florets that set seed per bulb. Bulbs stored
at 2°C for 24 weeks resulted in the poorest set per bulb. Inbred

2399 set the most florets, followed by inbreds 826 and 661-20.

Unbel (Table 20)

The 10°C 12 week-2°C 12 week treatment resulted in the highest
set per Mel and the 10°C 24 week treatment the lowest. Inbred 826
set the most florets per mel.

The treatments had no effect on inbreds 2399 and 661-20, but

inbred 826 set more florets per umbel after the 2°C treatments.

Primary Umbel (Table 21)

Although the storage treatments had no significant effect,
storage at 10°C for 12 weeks followed by 2°C for 12 weeks resulted

in the highest set per primary umbel. Inbred 826 set the most florets.

Seoond_a__ry Unbel (Table 22)

Storage at 2°C for 24 weeks resulted in the highest number of
florets that set seed per secondary umbel, while storage at 10°C for
24 weeks resulted in the lowest. The combination treatments resulted
in an intermediate number. Inbred 826 set approximately 100 more

florets per secondary umbel than inbred 2399.

44

Table 19. Mean number of florets that set seed per bulb for 3 onion
inbred lines following 4 storage treatments, 1976

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 6529 ' 7039 274f 543
2°C 12 wk- 8939 6789 289f 620
lO‘C 12 wk
10°C 12 wk- 9309 708f9 394f 677
2°C 12 wk
10°C 24 wk 10529 602f 292f 649
Inbred means 8823 6736 312?

 

xMeans in columns and means in rows followed by the same
letter (f to h) are not significantly different at the 5% level.

45

Table 20. Mean number of florets that set seed per umbel for 3
onion inbred lines following 4 storage treatments, 1976

 

 

 

Inbredx

Storage Treatment
treatment 2399 826 661—20 means
2°C 24 wk 272f 5309 274f 359

a b a AB
2°C 12 wk- 249f 5509 289f 363
10°C 12 wk a b a AB
10°C 12 wk— 290f 5229 394fg 402
2°C 12 wk a b a B
10°C 24 wk 238f 310f 248f 265

a a a A
Inbred means 262? 4786 301?

 

xMeans in columns followed by the same letter (a to b) and
means in rows followed by the same letter (f to 9) are not signifi-
cantly different at the 5% level.

46

Table 21. Mean number of florets that set seed per primary umbel for
3 onion inbred lines following 4 storage treatments, 1976

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 296f 5549 274f 374
2°C 12 wk- 320f 5829 289f 397
10°C 12 wk
10°C 12 wk- 376f 6079 394f9 459
2°C 12 wk
10°C 24 wk 336f 422f 264f 341
Inbred means 332? 5416 305?

 

xMeans in columns and means in rows followed by the same
letter (f to g) are not significantly different at the 5% level.

47

Table 22. Mean number of florets that set seed per secondary umbel
for 2 onion inbred lines following 4 storage treatments.

 

 

 

1976
Inbredx

Storage Treatment
treatment 2399 826 means
2°C 24 wk 255f 4679 361

a c B
2°C 12 wk- 222? 4109 316
10°C 12 wk a bc B
10°C 12 wk- 250f 286f 268
2°C 12 wk a ab AB
10°C 24 wk 2llf 180f 196

a a A
Inbred means 234? 3366

 

xMeans in columns followed by the same letter (a to b) and
means in rows followed by the same letter (f to g) are not signifi-
cantly different at the 5% level.

48

The treatments had no significant effect on inbred 2399, but
storage of inbred 826 at 2°C for 24 weeks or at 2°C the first 12
weeks resulted in a greater set than the other two treatments.
Secondary Florets that Set Seed
per Bulb (Table 23)

The storage treatments had no significant effect on the number
of secondary florets that set seed per bulb. However, storage at
10°C for 24 weeks resulted in the most secondary florets (florets
from all secondary umbels) per bulb and therefore it also resulted
in the highest number of secondary florets that set seed per bulb.
Inbred 2399 produced the largest number of secondary florets and

therefore the highest number that set seed.

Summary

A significantly larger number of florets set seed per umbel
after the 10°C 12 week-2°C 12 week treatment. The number of florets
that set seed per bulb, per primary umbel, and the secondary florets
that set seed per bulb were less affected by the storage treatments.

The treatments had no significant effect on the number of
florets that set seed per secondary umbel for inbred 2399. However,
storage of inbred 826 at 2°C for 24 weeks or at 2°C for the first

12 weeks resulted in a greater set per secondary umbel.

Number of Seeds per Floret
No significant differences were found. However, the 10°C 24
week treatment resulted in the fewest seeds per floret in every
category (Tables 24 through 27). The mean number of seeds per floret

per bulb was 2.38.

49

Table 23. Mean number of secondary florets that set seed per bulb
for 2 onion inbred lines following 4 storage treatments,

1976

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 means
2°C 24 wk 3579 148f 252
2’6 12 wk- 5739 96f 334
lO'C 12 wk
10°C 12 wk- 5539 101f 327
2°C 12 wk
lO‘C 24 wk 7169 179f 448
Inbred means 5506 131?

 

xMeans in columns and means in rows followed by the same
letter (f to g) are not significantly different at the 5% level.

50

Table 24. Mean number of seeds per floret per bulb for 3 onion
inbred lines following 4 storage treatments, 1976

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661—20 means
2°C 24 wk 3.17 2.28 2.61 2.68
2°C 12 wk- 2.67 2.16 2.80 2.54
10°C 12 wk
10°C 12 wk- 2.67 2.24 2.50 2.47
2°C 12 wk
10°C 24 wk 1.77 2.36 1.34 1.82
Inbred means 2.57 2.26 2.31

 

xMeans in columns and means in rows followed by the same

letter are not significantly different at the 5% level.

51

Table 25. Mean number of seeds per floret per umbel for 3 onion
inbred lines following 4 storage treatments, 1976

 

 

 

. Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 2.80 2.49 2.61 2.63
2°C 12 wk— 3.13 2.06 2.80 2.66
10°C 12 wk
10°C 12 wk- 2.93 2.38 2.50 2.60
2°C 12 wk
10°C 24 wk 2.12 2.61 1.58 2.10
Inbred means 2.74 2.38 2.37

 

xMeans in columns and means in rows are not significantly
different at the 5% level.

52

Table 26. Mean number of seeds per floret per primary umbel for 3
onion inbred lines following 4 storage treatments, 1976

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 661-20 means
2°C 24 wk 2.94 2.49 2.61 2.68
2°C 12 wk- 3.14 2.14 2.80 2.69
lO’C 12 wk
10°C 12 wk- 2.93 2.10 2.50 2.51
2°C 12 wk
10°C 24 wk 2.14 2.46 1.48 2.03
Inbred means 2.79 2.30 2.35

 

*Means in columns and means in rows are not significantly
different at the 5% level.

53

Table 27. Mean number of seeds per floret per secondary umbel for 2
onion inbred lines following 4 storage treatments, 1976

 

 

 

Inbredx
Storage Treatment
treatment 2399 826 means
2°C 24 wk 2.74 2.29 2.52
2°C 12 wk- 3.00 1.74 2.37
10°C 12 wk
10°C 12 wk- 2.87 3.68 3.28
2°C 12 wk
lO’C 24 wk 1.96 2.00 1.98
Inbred means 2.64 2.43

 

xMeans in columns and means in rows are not significantly
different at the 5% level.

V. SUMMARY AND CONCLUSIONS

In 1975 and 1976 three M.S.U. onion inbreds, 661-20, 826, and
2399, were given the following 4 storage treatments: 2°C 24 weeks,
2°C 12 weeks-10°C 12 weeks, 10°C 12 weeks-2°C 12 weeks, and 10°C 24
weeks. Data on seed yield and related factors were collected and
the results are summarized below:

1. The 2°C 24 week storage treatment delayed the emergence
of inbreds 2399 and 826, but lO'C for 24 weeks delayed inbred 661-20.

2. Flowering was delayed by storage at 2°C for 24 weeks, while
storage at 10°C for 24 weeks or at 10°C for the last 12 weeks
resulted in earlier flowering. Storage at 10°C for the first 12
weeks had an intermediate effect.

3. The 10°C 24 week treatment resulted in the shortest primary
seedstalks and the 10°C 12 week-2°C 12 week treatment the tallest.
Inbred 661-20 produced the shortest primary seedstalks after the
2°C 24 week treatment, while inbreds 2399 and 826 produced the
tallest.

4. The 10°C 24 week and 10°C 12 week-2°C 12 week treatments
resulted in the most leaves.

5. For inbreds 2399 and 826, the 10°C 24 week treatment
resulted in the most umbels per bulb and the 2°C 24 week and 10°C
12 week-2°C 12 week treatments the least. The higher number of

umbels did not produce highest number of florets or seed yield per

54

55
bulb. The storage treatments had no significant effect on inbred
661-20 and it only produced 1 umbel per bulb.

6. Storage of inbred 661-20 at 2’C for 24 weeks or at 2°C for
the second 12 weeks resulted in a significantly greater number of
florets per umbel (therefore per bulb).

Storage of inbred 826 at 2°C for 24 weeks resulted in 1.48
umbels and the fewest florets per bulb. Storage at 2°C for the
first 12 weeks resulted in approximately the same number of umbels
(1.68), but a significantly greater number of florets per bulb. If
2°C was given for the second 12 weeks, inbred 826 again produced
approximately the same number of umbels (1.38), but only an inter-
mediate number of florets per bulb. The 10‘C 24 week treatment
resulted in 2.49 umbels per bulb. This increase of l umbel per
bulb did not increase the total florets per bulb, but resulted in
significantly fewer florets per umbel.

Inbred 2399 produced 4.25 umbels after the 10°C 24 week treat-
ment while storage at 2°C for 24 weeks resulted in 2.69 umbels. The
combination treatments resulted in 3.29 umbels per bulb. Although
for inbred 2399 the number of umbels per bulb varied dramatically,
the total florets per bulb did not. The florets were simply dis-
tributed over the number of umbels.

7. The seed yield per bulb did not vary significantly, but was
the highest after the 10°C 12 week-2°C 12 week treatment. This
treatment resulted in the highest seed yield per umbel.

8. The storage treatments had no significant effect on the
weight per seed.

9. A significantly greater number of florets set seed per umbel

after the lO'C 12 week-2°C 12 week treatment.

56

10. Although not significant, the fewest seeds per floret
occurred after the 10°C 24 week treatment.

The storage treatments had no significant effect on the seed
yields per bulb. However, the 10°C 12 week-2°C 12 week treatment
resulted in the best yield, which agrees with earlier studies
(DeMille and Vest, 1976; van Der Meer and Van Bennekom, 1969).
Accompanying this higher seed yield was a high number of leaves per
bulb; tall primary seedstalks: the highest seed set and seed yield
per umbel: and a high number of florets and seeds per floret per
umbel. It appears that all factors were at an optimum level for
maximum seed production. Apparently this treatment conditions or
programs the bulb to allow (cause?) the optimum development of
complexly interrelated morphological factors and leads to a vigorous
healthy seed plant and a higher seed yield.

This treatment may approximate the natural environmental condi-
tions from'which these onions were domesticated, i.e., a gradually
cooling fall, cold winter, and a gradually warming spring.

Future work besides the 4 treatments should include a fifth
one: 10’C 8 weeks-2‘6 8 weeks-10°C 8 weeks. Since the inbreds
responded so differently, in a breeding program it would be necessary
to include all inbreds and classify the responses of each one. Then
the best storage temperatures could be provided for the highest

consistent seed yields.

APPENDIX

57

Table A-1. Analysis of variance: Effect of bulb storage treatments
on days to emergence, days to flowering, height (cm) of
the primary seedstalk. the total number of leaves per
bulb, and the total number of umbels per bulb, 1975 and
1976 combined

 

 

Height of

Days to Days to Primary Leavesl' unbels/
Source df Emergence1 Flowering Seedstalk Budb Bulb
Year 1 711.11*** 4,074.69*** 1,222.08*** 1.46ns 1.65***
Block+
Yearx 2 7.22ns 26.36ns 2.80ns 2.62ns .56*
Block
Tmt 3 25.68* 245.56*** 123.8l*** 18.08*** 5.62***
Inbred 2 1,834.01*** 806.80*** 7,543.14*** 1,037.51*** 69.35***
TxI 6 81.55*** 35.45“ 102.84*** 4.23ns l.57***
YxT 3 13.46ns 13.71ns 5.17ns 5.54ns .29ns
YxI 2 78.22*** 46.13* 17.4lns 22.50*** 1.55***
YxTxI 6 9.43ns 10.93ns 12.7lns S.llns .16ns
ERROR 118 7.31 11.19 16.02 2.82 .16
Total 143

 

*Mean squares.

*

Significant at the 5% level.
as

Significant at the 1% level.

it.
Significant at the .5% level.

58

Table A-2: Analysis of variance: Effect of bulb storage treatments
on number of florets for 3 M.S.U. onion inbreds, 1975

and 1976 combined

 

Florets/

 

Source df Primary Umbel1 Florets/Bulb Florets/umbel
Year 1 6,627.00ns 5,313.02ns 6,302.08ns
Block+

Yearx 2 5,075.08ns 32,761.27ns 7,567.50ns
Block

Tmt 3 47,971.00*** 31,872.9lns 68,294.8l***
Inbred 2 478,621.02*** 3,975,794.00*** 233,273.69***
TxI 6 18,605.27** 75,293.99* 15,116.74*
YxT 3 4,331.56ns 38,883.74ns 1,754.03ns
YxI 2 30,472.94** 72,206.33ns 40,833.52***
YxTxI 6 2,482.58ns 38,299.56ns 3,027.50ns
ERROR 22 4,692.76 27,310.36 5,015.82
Tbtal 47

 

1Mean squares.
*
Significant at the 5% level.

it
Significant at the 1% level.

it!
Significant at the .5% level.

59

 

 

Table A-3. Analysis of variance: Effect of bulb storage treatments
on the number of florets for 2 M.S.U. onion inbreds
(826 and 2399), 1975 and 1976 combined
Florets/Secondary Secondary Florets/
Source df Umbel1 Bulb
Year 1 760.5ns 57545.28ns
Block+Year 2 2038.56ns 45121.28ns
xBlock
Tmt 3 20976.88ns l96685.1l**
Inbred l 5512.50ns 2615756.00***
TxI 3 11256.08ns 23676.45ns
YxT 3 3945.58ns 57601.11ns
YxI l 861.12ns 197977.78*
YxTxI 3 1304.71ns 21183.45ns
Error 14 10405.06ns 35686.07ns
Total 31

 

1
Mean squares.

*
Significant at the 5% level.

it
Significant at the 1% level.

*i

*
Significant at the .5% level.

60

Table A-4. Analysis of variance: Effect of bulb storage treatments
on seed yield of 3 M.S.U. onion inbreds, 1975 and 1976
combined

 

 

Seed Yield/ 1 Seed Yield/ Seed Yield/
Source df Primary umbel Bulb Umbel
Year 1 7.2988*** 1.7953ns 9.9794***
Block+
Yearx 2 1.2307* 3.4S9lns 1.0256**
Block
Tmt 3 3.0324*** 3.4242ns 4.2546***
Inbred 2 17.4667*** 239.7620*** 6.6560***
TxI 6 .1669ns 2.4262ns .0666ns
YxT 3 .6838ns 5.0423ns .6638*
YxI 2 4.9652*** 11.5421*** 4.9706***
YxTxI 6 .3704ns 1.7762ns .3172ns
ERROR 22 .2260 1.6761 .1784
Total 47

 

1Mean squares.

*

Significant at the 5% level.
9*

Significant at the 1% level.

tit
Significant at the .5% level.

61

Table A-5. Analysis of variance: Effect of bulb storage treatments
on seed yield of 2 M.S.U. onion inbreds (826 and 2399),

1975 and 1976 combined

 

Seed Yield/Secondary

Secondary Seed

 

Source df Umbel]- Yield/Bulb
Year 1 5.56*** 2.70ns
Block+Year 2 .lOns 2.10ns
xBlock

Tmt 3 2.65** 2.32ns
Inbred l 4.46*** 175.16***
TxI 3 .32ns 2.28ns
YXT 3 1.62* 3.07ns
YxI l 10.45*** 1.9lns
YxTxI 3 .87ns 2.28ns
Error 14 .41 1.45
Total 31

 

1

Mean squares.

e .

Significant at the 5% level.
i *

Significant at the 1% level.

tit
Significant at the .5% level.

62

Table A-6. Analysis of variance: Effect of bulb storage treatments
on the weight per seed for 3 M.S.U. onion inbreds, 1975
and 1976 combined

 

 

Weight/Seed1 Primary Weight/Seed
Source df Umbel Umbel
Year 1 .1636* .0149ns
Block+Year 2 .0614ns .ll67*
xBlock
Tmt 3 .0317ns .0240ns
Inbred 2 .4798*** .9752***
TxI 6 .1074* .0706ns
YxT 3 .0686ns .0944ns
YxI 2 .0670ns .l346*
YxTxI 6 .0855* .0653ns
ERROR 22 .0324 .0317
Total 47

 

1Mean squares.

*

Significant at the 5% level.
i

*
Significant at the 1% level.

iii
Significant at the .5% level.

63

Table A-7. Analysis of variance: Effect of bulb storage treatments
on the weight per seed for 2 M.S.U. onion inbreds (826
and 2399), 1975 and 1976 combined

 

 

Source df weight/Seed Secondary Umbel1
Year 1 l.4995***
Block+Year 2 .2762ns
xBlock

Tmt 3 .1106ns
Inbred 1 4.4708***
TxI 3 .l490ns
YxT 3 .5905***
YxI l .5883*
YxTxI 3 .3184*
ERROR 14 .0860
Total 31

 

1Mean squares.

*

Significant at the 5% level.
it

Significant at the 1% level.

tit
Significant at the .5% level.

 

 

 

Table A-8. Analysis of variance: Effect of bulb storage treatments

on the number of florets that set seed for 3 M.S.U.

onion inbreds, 1976

Floret Set/ 1 Floret Set/ Floret Set/
Source df Primary umbel umbel Bulb
Block 1 782.04ns 1,232.67ns 630.38ns
Tmt 3 14,928.38ns 20,243.00* 19,966.49ns
Inbred 2 l33,988.79*** 105,569.54*** 663,032.38***
TxI 6 4,069.79ns 7,299.04ns 23,471.65ns
ERROR 11 6,748.50 4,550.76 14,832.10
Tetal 23
1

Mean squares.

*

Significant at the 5% level.
it

Significant at the 1% level.

tit
Significant at the .5% level.

65

Table A-9. Analysis of variance: Effect of bulb storage treatments
on the number of seeds per floret for 3 M.S.U. onion
inbreds, 1976

 

Seeds/Ploret1 Seeds/Floret Seeds/Floret

 

 

Source df Primary umbel umbel Bulb
Block 1 .0726ns .1190ns .0014ns
Tmt 3 .5870ns .4272ns .8786ns
Inbred 2 .5772ns .3555ns .2232ns
TxI 6 .2971ns .3323ns .2429ns
ERROR 11 .3788 .4121 ..4761
Total 23
1

Mean squares.

*

Significant at the 5% level.
it

Significant at the 1% level.

tit
Significant at the .5% level.

66

Table A-lO. Analysis of variance: Effect of bulb storage treatments
on the number of florets that set seed and seeds per
floret for 2 M.S.U. onion inbreds (2399 and 826), 1976

 

Floret Set/ Secondary Florets Seeds/Floret

 

 

Source df Secondary Umbel1 Set/Bulb Secondary Umbel
Block 1 1314.06ns 1.00ns .0030ns
Tmt 3 19956.73* 25894.50ns 1.1824ns
Inbred 1 40905.06*** 701406.25*** .1936ns

TxI 3 13795.23* 20935.08ns .7638ns
ERROR 7 2422.78ns 6970.28ns .3574ns
Total 15

1

Mean squares.

*
Significant at the 5% level.

it
Significant at the 1% level.

*tt
Significant at the .5% level.

LITERATURE CITED

LITERATURE CITED

Abdalla, A. A. and L. K. Mann. 1963. Bulb development in the onion
(Allium cepa L.) and effect of storage temperature on bulb
rest. Hilgardia 35:5.

Atkin, J. D. and 6. N. Davis. 1954. Altering onion flowering dates
to facilitate hybrid seed production. Calif. Agr. Expt.
Station Bull. 74.

Boswell, V. R. 1924. Influence of the time of maturity of onions
on the behavior during storage, and the effect of storage
temperature on subsequent vegetative and reproductive develop-
ment. Proc. Amer. Soc. Hort. Sci. 20:234-239.

DeMille, B. and G. Vest. 1975. Flowering date of onion bulbs as
affected by light and temperature treatments during storage.
J. Amer. Soc. Hort. Sci. 100:423-424.

DeMille, B. and 6. Vest. 1976. The effect of temperature and light
during bulb storage on traits related to onion seed production.
J. Amer. Soc. Hort. Sci. 101:52-53.

Hartsema, A. M. 1947. De periodieke ontivikkeling van Allium cepa
L. var. Zittauer Riesen. Med. Landbouwhoogeschool, Wageningen,
48:265.

Heath, 0. V. S. 1943. Studies in the physiology of the onion plant.
I. An investigation of factors concerned in the flowering
(”bolting") of onions grown from sets and its prevention.

Part I. Production and storage of onion sets, field results.
Ann. Appl. Biol. 30:208-220.

. 1943. Studies in the physiology of the onion plant. I.

An investigation of factors concerned in the flowering (”bolt-
ing“) of onions grown from.sets and its prevention. Part 2.
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