- Email: [email protected]
The effect of 4 storage treatments on seed yield components of 3 onion inbreds
Scientia Horticulturae, 11 (1979) 207-215 Elsevier Scientific Publishing Company, Amsterdam
207 - Printed
in The Netherlands
THE EFFECT OF 4 STORAGE TREATMENTS ON SEED YIELD COMPONENTS OF 3 ONION INBREDS
P.S. HESSE’ , G. VEST2 and S. HONMA3
’ Pan American Plant Co., Box 428, West Chicago, IL 60185 (U.S.A.) ‘Department of Horticulture, Oklahoma State University, Stillwater, OK 74074 (U.S.A.) ‘Department of Horticulture, Michigan State University, East Lansing, MI 48824 (U.S.A.) Journal
Article
(Accepted
No. 8800, Michigan
for publication
Agricultural
Experiment
Station.
18 April 1979)
ABSTRACT Hesse, P.S., Vest, G. and Honma, S., 1979. The effect of 4 storage components of 3 onion inbreds. Scientin Hortic., 11: 207-215.
treatments
on seed yield
Onion bulbs of 3 inbred lines were stored during the winter in 4 different storage temperature regimes. Traits directly and indirectly associated with seed production were studied the following summers. The inbred lines differed in their responses and many traits were affected by the storage treatments. The storage treatment of 10°C for 12 weeks followed by 2” C for 12 weeks resulted in a significantly higher seed yield than did storage at 2” C throughout the entire period. Inbred 2399 had a higher seed yield than the other inbreds. Associated with high seed yields of 2399 was early flowering, a high number of leaves/bulb, tall seed stalks and a high number of florets/bulb.
INTRODUCTION
It has been established that flowering and seed yield of onions (Allium ceL.) is affected by the storage temperature at which the mother bulbs are kept. Storage of bulbs at temperatures between 7.5 and 12°C has resulted in earlier flowering, a larger number of umbels, and a higher seed yield than that of bulbs stored at higher or lower temperatures or in common storage (Atkin and Davis, 1954; DeMille and Vest, 1976; Jones, 1927; Jones and Emsweller, 1939). It has also been reported (DeMille and Vest, 1976; Van der Meer and Van Bennekom, 1969) that changing the temperature during the storage period from a high (7-10°C) to a lower (2°C) temperature enhanced seed yields. The storage temperature of the mother bulb is also known to influence some of the factors that are thought to be associated with seed production. Woyke and Manczek (1965) reported that storage temperature affected the number of seed stalks/bulb, but the seed yield and number of seed stalks were not correlated. Mital and Srivastava (1964) reported that selection for an in-
pa
208
creased number of seed stalks/plant increased seed yield, but for some cultivars seed size decreased as the number of seed stalks increased, Early flowering onion plants have been reported to produce a greater number and higher quality of seed than late flowering ones (Prokhorov and Khomyakov, 1972), and the time of flowering is known to be influenced by storage temperature (Atkin and Davis, 1954; DeMille and Vest, 1975, 1976; Jones, 1927; Jones and Emsweller, 1939). Seed stalk height and number of leaves per plant are also influenced by storage temperature (DeMille and Vest, 1975,1976). Extremely high or low storage temperatures have been reported to inhibit or delay the formation of flower primordia, while temperatures of 11-12°C have been considered optimum (Jones and Mann, 1963). It has also been reported (Atkin and Davis, 1954) that a lo”, 20” C or “common” storage treatment resulted in significantly more florets/umbel than a 0” C storage treat ment. In most studies, open pollinated onion cultivars have been used to show the various storage treatment effects. The objective of our study was to use 3 highly inbred onion lines to determine the influence of storage temperature treatments on seed yield and various components of that yield. We chose inbred lines to determine effects of storage that should be considered in hybrid seed production. MATERIALS
AND METHODS
Bulbs of 3 onion inbred maintainer lines, MSU 661-20B, MSU 826B and MSU 2399B, were grown at the Michigan State University Muck Farm in 1974 and 1975. The bulbs were harvested, cured, sorted, graded for size and placed into one of the following 4 storage treatments: (1) 2°C for 24 weeks; (2) 2°C for 12 weeks followed by 10°C for 12 weeks; (3) 10°C for 12 weeks followed by 2°C for 12 weeks; (4) 10°C for 24 weeks. These treatments will be referred to as 2”C, 2”/1O”C, 10”/2”C and lO”C, respectively. Following the 24 weeks of storage, the bulbs were planted into the field and later covered with a 3.7 m X 24.4 m lumite cage. Bees were spaced throughout the cage to provide for pollination. Mature seed was harvested and thrashed by hand. Light seed and chaff were separated from the good seed by placing all seed in water and saving the heavy seed. Each treatment consisted of 15 bulbs/replication the first year and 30 bulbs/ replication the second year. The experimental design was a randomized complete block with 2 replications. Data were taken on 9 traits which will be detailed in the results. Data were subjected to analysis of variance for both years combined. The mean separations were done using Duncan’s new multiple range test (Steel and Torrie, 1960).
209 RESULTS
Days fern
planting to sprouting 2°C
2”/10” c
10”/2” c
10°C
Mean
___
i6.4 b g 26.8 b f
35.5 ab h 24.5 ab g 19.9 a f
32.8 ab g 25.2 ab f 22.7 a f
28.4 F
26.6 F
26.9 F
661-20
32.0 a
826 2399
X
36.2 b g 23.1 a f 20.5 a f -__
34.1 c 24.8 B 22.5 A
26.6 F
Sprouting of 661-20 was hastened by storage at 2°C and delayed at 10°C. However, 826 and 2399 responded in an opposite manner such that 2°C de layed sprouting and 10°C hastened it. 661-20 and 826 responded intermediately at 2”/1O”C and 10”/2”C, but 2399 responded to these treatments as it did to the 10°C treatment and sprouting was hastened. Inbred 2399 sprouted earlier than 826, which was much earlier than 661-20. Different responses of the inbreds to the different treatments are also apparent in the data. Days from planting to 1st flower
661-20 826 2399
X
2°C
2”/10” c
10”/2” c
10°C
Mean
83.2 a f 80.0 c f 78.8 b f
81.6 a g 71.8 a f 72.7 a f
81.4 a g 76.8 bc fg 74.9 ab f
81.3 a g 72.2 ab f 71.5 a f
81.9 B
80.7 G
75.4 F
77.7 F
75.0 F
75.2 A 74.5 A
The time required for 661-20 to flower was not affected by the storage treatments, but 2°C for 24 weeks delayed the flowering of 826 and 2399. The 10”/2”C treatment also delayed the flowering of 826. Both 826 and 2399 flowered approximately 7 days earlier than 661-20. When averaged across inbreds, 2°C caused later flowering than all other treatments. There were also differences between inbreds associated with the storage treatments.
210
Height (cm) of the primary seed stalk
661-20 826 2399 X
2°C
2”/10” c
10”/2” c
10°C
Mean
66.5 a f 80.1 a g 97.6 L h
67.4 a f 82.7 a g 93.0 ab h
70.4 a f 81.6 a g 95.8 b h
69.1 a f 78.3 a g 87.2 a h
68.4 A
81.4 F
81.0 F
82.6 F
78.2 F
-
80.7 B 93.4 c -.__
The height of the primary seed stalk of 661-20 and 826 was not significantly affected by the storage treatment. However, 2399 seed stalks from the 10°C treatment were shorter than those from the 2°C and 10”/2”C! treatments. The seed stalks of 661-20 were significantly shorter than 826 which were significantly shorter than 2399. Number of leaves per bulb 2°C 661-20
2399 X
10”/2” c
10°C
4.9 a
5.3 a f 10.0 ab g 14.7 ab h
5.3 a f 11.3 a
10.0 FG
10.7 G
5.1 a f
826
2”/10” c
f 8.9 a
g 12.9 a h 9.0 F
9.8 a f4.7 ab h 9.8 FG
T5.5 b h
-
Mean 5.2 A 10.0 B 14.4 c
The number of leaves of 661-20 was not influenced by the storage treatment. However, 826 and 2399 both had fewer leaves at 2°C than at 10°C. Overall, 661-20 had significantly fewer leaves than 826 which had fewer leaves than 2399, and the 2°C treatment induced fewer leaves than the 10°C treatment. Number of umbels per bulb
661-20 826 2399
X
2°C
2”/10” c
10”/2” c
10°C
Mean
1.00 a f 1.48 a f 2.61 a g
1.00 a f 1.68 a g 3.47 b h
1.00 a f 1.38 a f 3.12 ab g
1.04 a f 2.49 b g 4.25 c h
1.01 A
1.69 F
2.05 G
1.83 FG
2.59 H
1.76 B 3.36 C
211
Inbred 661-20 produced a single seed stalk and the storage temperature did not change this. 826 and 2399 produced significantly more umbels when stored at 10°C than when stored at the other treatments. 2399 also had significantly more umbels at 2”/1O”C than at 2°C which resulted in fewest seed stalks. Overall, 2399 had significantly more umbels than 661-20 and 826, and 826 had significantly more umbels than 661-20. The 10°C treatment induced the production of more umbels than did the other 3 treatments, and 2°C resulted in the lowest number of umbels. The individual inbreds responded differently to the different storage treatments. Number of florets per bulb 2°C
10”/2” c
10°C
g 1303.5 a h
316.0 a f 1232.2 b g 1464.0 a g
467.8 a f 1003.5 ab g 1408.8 a h
354.5 a f 1201.2 b g 1375.5 a g
883.9 F
1004.1 F
960.0 F
504.5 a
661-20 f 826 2399 X
Mean
2”/10” c
_~_._
843.8 a
410.7 A 1070.2 B 1388.0 c
977.1 F
The number of florets produced by 661-20 and 2399 were not affected by the storage treatment. However, 826 produced significantly more florets from the 2”/1O”C and 10°C treatments than the 2°C treatment. There were sig nificantly more florets produced by 2399 than by 826, and 826 produced significantly more than 661-20. There were significant differences between inbreds associated with the different storage treatments. Number of seeds per floret 2°C
2”/10”c
10”/2”c
10°C
Mean
661-20 826 2399
2.61 2.28 3.17
2.80 2.16 2.67
2.50 2.24 2.67
1.34 2.36 1.77
2.31 2.26 2.47
X
2.68
2.54
2.47
1.82
Because of the variability associated with the number of seeds per floret, no statistical differences were found associated with the treatments or the inbreds. There were numerical differences and trends associated with treatments and inbreds that may or may not be important.
212
Seed yield (g) per bulb 2°C
2”/10” c
10”/2” c
10°C
Mean
1.97 a f 4.67 a
2.06 a f 4.22 a
2.54 a f 4.65 a
1.15 a f 4.67 a
1.93 A
2399
;.89 a h
i.96 b h
X
4.84 F
5.41 FG
661-20 826
Loo h
b
:.35 ab h -.__
6.06 G
4.55 B 9.55 c
5.06 FG
The seed yield/bulb of 661-20 and 826 was not affected by the storage treatments. The yields of 2399, however, were influenced, and the seed yield associated with the 2”/10” C and 10”/2” C temperatures were significantly higher than the yield from the 2°C treatment. The inbreds differed significantly in that 2399 yielded more than the other 2 inbreds and 826 yielded more than 661-20. The 10”/2” C treatment resulted in significantly more seed yield than did the 2°C storage treatment. Weight (mg) of individual seed 2°C 661-20 826 2399 X
3.8 g 3.5 f 4.0 g 3.8
a a b F
2”/10” c
10”/2” c
10°C
Mean
4.1 g 3.4 f 3.9 g 3.8
3.7 f 3.5 f 4.0 g 3.7
3.9 ab g 3.5 a f 3.7 a f
3.9 B
b a ab F
a a b F
__~
3.5 A 3.9 B
3.7 F
The seed size of inbreds 661-20 and 2399 was influenced by the storage treatment. The largest seed of 661-20 was found with the 2”/1O”C treatment and the smallest with the 2°C and 10”/2”C treatments. With 2399 the smallest seed was associated with the 10°C treatment. The seed size of 826 was not affected by the storage treatment and this inbred had significantly smaller seed than the other 2 lines. DISCUSSION
It is obvious that inbreds were different in the time required to sprout and flower and that they each responded differently to the storage treatments. These differences need to be understood and considered in seed production and may necessitate proper storage and handling to ensure “nicking .” The
213
procedure of altering storage temperatures to alter flowering-dates has been suggested by Atkin and Davis (1954). The number of leaves, number of seed stalks and seed stalk height were considered in the study because of the photosynthetic area they comprise which may have an effect on seed yield. Our results showed that the inbreds with the tallest seed stalks had the highest yields. However, a cause-and-effect relationship is not implied. With lines 661-20 and 826 the treatments had no effect on seed stalk height or on the seed yield. Tall seed stalks may cause a problem in that they have a tendency to lodge, making cultural practices and separation of the seed and pollen parents difficult. The numbers of leaves, in general, were related to the seed yields of the different inbreds with the highest yielding inbred having the highest seed yield, and the lowest yielding inbred having the least number of leaves. Again a cause-and-effect relationship may or may not be involved. The number of seed stalks not only increases the photosynthetic surface, but also results in a larger number of umbels in which the seed can be borne. However, in this study the increase in the number of umbels did not increase the number of florets per bulb of the individual inbreds. However, the inbreds with the largest number of umbels also had the largest number of ,florets and the highest seed yields. The treatments did affect the number of seed stalks produced on both 826 and 2399, but did not change the single seed stalk trait of 661-20. Theoretically the number of florets produced by a plant should influence the amount of seed produced. Thus, a portion of this study was devoted to determining the number of florets produced and the number of good seed in each floret. The inbred with the highest number of florets had the highest yield and the inbred with the least number of florets had the lowest yield. The storage treatments did influence the number of florets produced by 826, but not by 661-20 and 2399. Although 661-20 had only 1 seed stalk/plant, there were numerical differences in the numbers of florets produced associated with storage treatment. With 826 there were significantly more umbels produced at the 10°C treatment than at the 2”/1O”C treatment. However, the number of florets produced from these treatments was the same. With 2399 also there were significant differences in the numbers of umbels/bulb associated with the storage treatments, but the numbers of florets/bulb did not change with either the storage treatment or the number of umbels. Thus it appears that the number of umbels/bulb and the number of florets/bulb respond independently to the storage treatments. The numbers of viable seed in each floret were essentially the same as no significant differences were found. In an earlier study, DeMille and Vest (1976) reported that storage treatments did not affect the number of umbels produced by an open pollinated cultivar, but that high seed yields were associated with a treatment which changed from 7 to 2°C during the storage period. It is apparent in the present study that the 10”/2”C treatment was favorable for seed yield, which was significantly greater than that of the 2°C treatment. This was not a result of more seeds/floret, florets/bulb or umbels/bulb.
214
Although the reason for this increase in seed yield is not exactly clear, it could be that the 10/2”C treatment conditioned or programmed the bulb to allow (cause?) the optimum development of complexly interrelated factors which lead to a vigorous healthy plant, and a higher seed yield. The other treatments that involved a 10°C temperature during the storage period also had seed yields similar to the 10”/2”C treatment. The 10”/2”C treatment, followed by planting into the field, may approximate the natural environmental conditions from which onions were domesticated, i.e. a gradually-cooling season, a cold season, and a gradually-warming season. The storage treatments had no significant effect on the weight of individual seed, but 826 had significantly smaller seed than the other 2 inbreds. Still the seed yield of 826 was significantly greater than that of 661-20. From this study it is apparent that inbred onion lines vary in their response to- storage temperature and in their seed yield potential. Thus it is possible to select inbreds for seed yield and to some extent control components of their yields through storage temperatures. Throughout this study, inbreds 826 and 2399 responded more to the treatments than did 661-20. Both of these inbreds are mild flavored onions. On the other hand, inbred 661-20 is a highly pungent onion. It is not known whether this trait is related to the results we obtained. Accompanying the high seed yields of 2399 (which produced more seed than the other inbreds) were earlier sprouting, earlier flowering, taller seed stalks, a higher number of umbels/bulb, a higher number of florets/bulb and larger individual seed than the other inbreds. Treatments which were associated with the higher seed yields caused earlier flowering, a higher number of leaves and a higher number of umbels than the treatment associated with the lowest seed yield. Many of the traits associated with bolting, flowering and seed production of the onion plant are now known to be influenced by the storage temperature of the mother bulb. In addition, it has been shown that bulbs of different genotypes respond differently to the storage environment as it pertains to traits associated with seed yield. These traits and their effect on the yield should be further elaborated to make it possible for better commercial production of hybrid onion seed.
REFERENCES Atkin, J.S. and Davis, G.N., 1954. Altering onion flowering dates to facilitate seed production. Calif. Agric. Exp. Stn. Bull., 74. DeMille, B. and Vest, G., 1975. Flowering date of onion bulbs as affected by light and temperatue treatments during storage. J. Am. Sot. Hortic. Sci., 100: 423-424. DeMille, B. and Vest, G., 1976. The effect of temperature and light during bulb storage on traits related to onion seed production. J. Am. Sot. Hortic. Sci., 101: 52-53. Jones, H.A., 1927. The influence of storage temperature on seed production in Ebenezer onion. Bloc. Am. Sot. Hortic. Sci., 24: 61-63.
215 Jones, H.A. and Emsweller, S.L., 1939. Effect of storage, bulb size, spacing and time of planting on production of onion seed. Calif. Exp. Stn. Bull., 628. Jones, H.A. and Mann, L.K., 1963. Onions and Their Allies. InterScience, New York, 286 pages. Mital, S.P. and Srivastava, G., 1964. Seed yield in relation to bulb size and number of seed stalks in onion (Allium cepa L). Indian J. Hortic., 21: 263-269. Prokhorov, I.A. and Khomyakov, P.I., 1972. The yield and quality of onion seed in relation to flowering date. Hortic. Abstr., 1974: 7708. Steel, R.G.D. and Torrie, J.H., 1960. Principles and Procedures of Statistics. McGraw-Hill, New York, 481 pages. Van der Meer, Q.P. and Van Bennekom, J.L., 1969. Some experiences with onions for seed. Hortic. Abstr., 1969: 4887. Woyke, H, and Manczek, M., 1965. Number of seed stocks and the seed yield of several newly bred and local onion varieties as affected by the temperature at which the bulbs had been held. Hortic. Abstr., 1967: 1055.
207 - Printed
in The Netherlands
THE EFFECT OF 4 STORAGE TREATMENTS ON SEED YIELD COMPONENTS OF 3 ONION INBREDS
P.S. HESSE’ , G. VEST2 and S. HONMA3
’ Pan American Plant Co., Box 428, West Chicago, IL 60185 (U.S.A.) ‘Department of Horticulture, Oklahoma State University, Stillwater, OK 74074 (U.S.A.) ‘Department of Horticulture, Michigan State University, East Lansing, MI 48824 (U.S.A.) Journal
Article
(Accepted
No. 8800, Michigan
for publication
Agricultural
Experiment
Station.
18 April 1979)
ABSTRACT Hesse, P.S., Vest, G. and Honma, S., 1979. The effect of 4 storage components of 3 onion inbreds. Scientin Hortic., 11: 207-215.
treatments
on seed yield
Onion bulbs of 3 inbred lines were stored during the winter in 4 different storage temperature regimes. Traits directly and indirectly associated with seed production were studied the following summers. The inbred lines differed in their responses and many traits were affected by the storage treatments. The storage treatment of 10°C for 12 weeks followed by 2” C for 12 weeks resulted in a significantly higher seed yield than did storage at 2” C throughout the entire period. Inbred 2399 had a higher seed yield than the other inbreds. Associated with high seed yields of 2399 was early flowering, a high number of leaves/bulb, tall seed stalks and a high number of florets/bulb.
INTRODUCTION
It has been established that flowering and seed yield of onions (Allium ceL.) is affected by the storage temperature at which the mother bulbs are kept. Storage of bulbs at temperatures between 7.5 and 12°C has resulted in earlier flowering, a larger number of umbels, and a higher seed yield than that of bulbs stored at higher or lower temperatures or in common storage (Atkin and Davis, 1954; DeMille and Vest, 1976; Jones, 1927; Jones and Emsweller, 1939). It has also been reported (DeMille and Vest, 1976; Van der Meer and Van Bennekom, 1969) that changing the temperature during the storage period from a high (7-10°C) to a lower (2°C) temperature enhanced seed yields. The storage temperature of the mother bulb is also known to influence some of the factors that are thought to be associated with seed production. Woyke and Manczek (1965) reported that storage temperature affected the number of seed stalks/bulb, but the seed yield and number of seed stalks were not correlated. Mital and Srivastava (1964) reported that selection for an in-
pa
208
creased number of seed stalks/plant increased seed yield, but for some cultivars seed size decreased as the number of seed stalks increased, Early flowering onion plants have been reported to produce a greater number and higher quality of seed than late flowering ones (Prokhorov and Khomyakov, 1972), and the time of flowering is known to be influenced by storage temperature (Atkin and Davis, 1954; DeMille and Vest, 1975, 1976; Jones, 1927; Jones and Emsweller, 1939). Seed stalk height and number of leaves per plant are also influenced by storage temperature (DeMille and Vest, 1975,1976). Extremely high or low storage temperatures have been reported to inhibit or delay the formation of flower primordia, while temperatures of 11-12°C have been considered optimum (Jones and Mann, 1963). It has also been reported (Atkin and Davis, 1954) that a lo”, 20” C or “common” storage treatment resulted in significantly more florets/umbel than a 0” C storage treat ment. In most studies, open pollinated onion cultivars have been used to show the various storage treatment effects. The objective of our study was to use 3 highly inbred onion lines to determine the influence of storage temperature treatments on seed yield and various components of that yield. We chose inbred lines to determine effects of storage that should be considered in hybrid seed production. MATERIALS
AND METHODS
Bulbs of 3 onion inbred maintainer lines, MSU 661-20B, MSU 826B and MSU 2399B, were grown at the Michigan State University Muck Farm in 1974 and 1975. The bulbs were harvested, cured, sorted, graded for size and placed into one of the following 4 storage treatments: (1) 2°C for 24 weeks; (2) 2°C for 12 weeks followed by 10°C for 12 weeks; (3) 10°C for 12 weeks followed by 2°C for 12 weeks; (4) 10°C for 24 weeks. These treatments will be referred to as 2”C, 2”/1O”C, 10”/2”C and lO”C, respectively. Following the 24 weeks of storage, the bulbs were planted into the field and later covered with a 3.7 m X 24.4 m lumite cage. Bees were spaced throughout the cage to provide for pollination. Mature seed was harvested and thrashed by hand. Light seed and chaff were separated from the good seed by placing all seed in water and saving the heavy seed. Each treatment consisted of 15 bulbs/replication the first year and 30 bulbs/ replication the second year. The experimental design was a randomized complete block with 2 replications. Data were taken on 9 traits which will be detailed in the results. Data were subjected to analysis of variance for both years combined. The mean separations were done using Duncan’s new multiple range test (Steel and Torrie, 1960).
209 RESULTS
Days fern
planting to sprouting 2°C
2”/10” c
10”/2” c
10°C
Mean
___
i6.4 b g 26.8 b f
35.5 ab h 24.5 ab g 19.9 a f
32.8 ab g 25.2 ab f 22.7 a f
28.4 F
26.6 F
26.9 F
661-20
32.0 a
826 2399
X
36.2 b g 23.1 a f 20.5 a f -__
34.1 c 24.8 B 22.5 A
26.6 F
Sprouting of 661-20 was hastened by storage at 2°C and delayed at 10°C. However, 826 and 2399 responded in an opposite manner such that 2°C de layed sprouting and 10°C hastened it. 661-20 and 826 responded intermediately at 2”/1O”C and 10”/2”C, but 2399 responded to these treatments as it did to the 10°C treatment and sprouting was hastened. Inbred 2399 sprouted earlier than 826, which was much earlier than 661-20. Different responses of the inbreds to the different treatments are also apparent in the data. Days from planting to 1st flower
661-20 826 2399
X
2°C
2”/10” c
10”/2” c
10°C
Mean
83.2 a f 80.0 c f 78.8 b f
81.6 a g 71.8 a f 72.7 a f
81.4 a g 76.8 bc fg 74.9 ab f
81.3 a g 72.2 ab f 71.5 a f
81.9 B
80.7 G
75.4 F
77.7 F
75.0 F
75.2 A 74.5 A
The time required for 661-20 to flower was not affected by the storage treatments, but 2°C for 24 weeks delayed the flowering of 826 and 2399. The 10”/2”C treatment also delayed the flowering of 826. Both 826 and 2399 flowered approximately 7 days earlier than 661-20. When averaged across inbreds, 2°C caused later flowering than all other treatments. There were also differences between inbreds associated with the storage treatments.
210
Height (cm) of the primary seed stalk
661-20 826 2399 X
2°C
2”/10” c
10”/2” c
10°C
Mean
66.5 a f 80.1 a g 97.6 L h
67.4 a f 82.7 a g 93.0 ab h
70.4 a f 81.6 a g 95.8 b h
69.1 a f 78.3 a g 87.2 a h
68.4 A
81.4 F
81.0 F
82.6 F
78.2 F
-
80.7 B 93.4 c -.__
The height of the primary seed stalk of 661-20 and 826 was not significantly affected by the storage treatment. However, 2399 seed stalks from the 10°C treatment were shorter than those from the 2°C and 10”/2”C! treatments. The seed stalks of 661-20 were significantly shorter than 826 which were significantly shorter than 2399. Number of leaves per bulb 2°C 661-20
2399 X
10”/2” c
10°C
4.9 a
5.3 a f 10.0 ab g 14.7 ab h
5.3 a f 11.3 a
10.0 FG
10.7 G
5.1 a f
826
2”/10” c
f 8.9 a
g 12.9 a h 9.0 F
9.8 a f4.7 ab h 9.8 FG
T5.5 b h
-
Mean 5.2 A 10.0 B 14.4 c
The number of leaves of 661-20 was not influenced by the storage treatment. However, 826 and 2399 both had fewer leaves at 2°C than at 10°C. Overall, 661-20 had significantly fewer leaves than 826 which had fewer leaves than 2399, and the 2°C treatment induced fewer leaves than the 10°C treatment. Number of umbels per bulb
661-20 826 2399
X
2°C
2”/10” c
10”/2” c
10°C
Mean
1.00 a f 1.48 a f 2.61 a g
1.00 a f 1.68 a g 3.47 b h
1.00 a f 1.38 a f 3.12 ab g
1.04 a f 2.49 b g 4.25 c h
1.01 A
1.69 F
2.05 G
1.83 FG
2.59 H
1.76 B 3.36 C
211
Inbred 661-20 produced a single seed stalk and the storage temperature did not change this. 826 and 2399 produced significantly more umbels when stored at 10°C than when stored at the other treatments. 2399 also had significantly more umbels at 2”/1O”C than at 2°C which resulted in fewest seed stalks. Overall, 2399 had significantly more umbels than 661-20 and 826, and 826 had significantly more umbels than 661-20. The 10°C treatment induced the production of more umbels than did the other 3 treatments, and 2°C resulted in the lowest number of umbels. The individual inbreds responded differently to the different storage treatments. Number of florets per bulb 2°C
10”/2” c
10°C
g 1303.5 a h
316.0 a f 1232.2 b g 1464.0 a g
467.8 a f 1003.5 ab g 1408.8 a h
354.5 a f 1201.2 b g 1375.5 a g
883.9 F
1004.1 F
960.0 F
504.5 a
661-20 f 826 2399 X
Mean
2”/10” c
_~_._
843.8 a
410.7 A 1070.2 B 1388.0 c
977.1 F
The number of florets produced by 661-20 and 2399 were not affected by the storage treatment. However, 826 produced significantly more florets from the 2”/1O”C and 10°C treatments than the 2°C treatment. There were sig nificantly more florets produced by 2399 than by 826, and 826 produced significantly more than 661-20. There were significant differences between inbreds associated with the different storage treatments. Number of seeds per floret 2°C
2”/10”c
10”/2”c
10°C
Mean
661-20 826 2399
2.61 2.28 3.17
2.80 2.16 2.67
2.50 2.24 2.67
1.34 2.36 1.77
2.31 2.26 2.47
X
2.68
2.54
2.47
1.82
Because of the variability associated with the number of seeds per floret, no statistical differences were found associated with the treatments or the inbreds. There were numerical differences and trends associated with treatments and inbreds that may or may not be important.
212
Seed yield (g) per bulb 2°C
2”/10” c
10”/2” c
10°C
Mean
1.97 a f 4.67 a
2.06 a f 4.22 a
2.54 a f 4.65 a
1.15 a f 4.67 a
1.93 A
2399
;.89 a h
i.96 b h
X
4.84 F
5.41 FG
661-20 826
Loo h
b
:.35 ab h -.__
6.06 G
4.55 B 9.55 c
5.06 FG
The seed yield/bulb of 661-20 and 826 was not affected by the storage treatments. The yields of 2399, however, were influenced, and the seed yield associated with the 2”/10” C and 10”/2” C temperatures were significantly higher than the yield from the 2°C treatment. The inbreds differed significantly in that 2399 yielded more than the other 2 inbreds and 826 yielded more than 661-20. The 10”/2” C treatment resulted in significantly more seed yield than did the 2°C storage treatment. Weight (mg) of individual seed 2°C 661-20 826 2399 X
3.8 g 3.5 f 4.0 g 3.8
a a b F
2”/10” c
10”/2” c
10°C
Mean
4.1 g 3.4 f 3.9 g 3.8
3.7 f 3.5 f 4.0 g 3.7
3.9 ab g 3.5 a f 3.7 a f
3.9 B
b a ab F
a a b F
__~
3.5 A 3.9 B
3.7 F
The seed size of inbreds 661-20 and 2399 was influenced by the storage treatment. The largest seed of 661-20 was found with the 2”/1O”C treatment and the smallest with the 2°C and 10”/2”C treatments. With 2399 the smallest seed was associated with the 10°C treatment. The seed size of 826 was not affected by the storage treatment and this inbred had significantly smaller seed than the other 2 lines. DISCUSSION
It is obvious that inbreds were different in the time required to sprout and flower and that they each responded differently to the storage treatments. These differences need to be understood and considered in seed production and may necessitate proper storage and handling to ensure “nicking .” The
213
procedure of altering storage temperatures to alter flowering-dates has been suggested by Atkin and Davis (1954). The number of leaves, number of seed stalks and seed stalk height were considered in the study because of the photosynthetic area they comprise which may have an effect on seed yield. Our results showed that the inbreds with the tallest seed stalks had the highest yields. However, a cause-and-effect relationship is not implied. With lines 661-20 and 826 the treatments had no effect on seed stalk height or on the seed yield. Tall seed stalks may cause a problem in that they have a tendency to lodge, making cultural practices and separation of the seed and pollen parents difficult. The numbers of leaves, in general, were related to the seed yields of the different inbreds with the highest yielding inbred having the highest seed yield, and the lowest yielding inbred having the least number of leaves. Again a cause-and-effect relationship may or may not be involved. The number of seed stalks not only increases the photosynthetic surface, but also results in a larger number of umbels in which the seed can be borne. However, in this study the increase in the number of umbels did not increase the number of florets per bulb of the individual inbreds. However, the inbreds with the largest number of umbels also had the largest number of ,florets and the highest seed yields. The treatments did affect the number of seed stalks produced on both 826 and 2399, but did not change the single seed stalk trait of 661-20. Theoretically the number of florets produced by a plant should influence the amount of seed produced. Thus, a portion of this study was devoted to determining the number of florets produced and the number of good seed in each floret. The inbred with the highest number of florets had the highest yield and the inbred with the least number of florets had the lowest yield. The storage treatments did influence the number of florets produced by 826, but not by 661-20 and 2399. Although 661-20 had only 1 seed stalk/plant, there were numerical differences in the numbers of florets produced associated with storage treatment. With 826 there were significantly more umbels produced at the 10°C treatment than at the 2”/1O”C treatment. However, the number of florets produced from these treatments was the same. With 2399 also there were significant differences in the numbers of umbels/bulb associated with the storage treatments, but the numbers of florets/bulb did not change with either the storage treatment or the number of umbels. Thus it appears that the number of umbels/bulb and the number of florets/bulb respond independently to the storage treatments. The numbers of viable seed in each floret were essentially the same as no significant differences were found. In an earlier study, DeMille and Vest (1976) reported that storage treatments did not affect the number of umbels produced by an open pollinated cultivar, but that high seed yields were associated with a treatment which changed from 7 to 2°C during the storage period. It is apparent in the present study that the 10”/2”C treatment was favorable for seed yield, which was significantly greater than that of the 2°C treatment. This was not a result of more seeds/floret, florets/bulb or umbels/bulb.
214
Although the reason for this increase in seed yield is not exactly clear, it could be that the 10/2”C treatment conditioned or programmed the bulb to allow (cause?) the optimum development of complexly interrelated factors which lead to a vigorous healthy plant, and a higher seed yield. The other treatments that involved a 10°C temperature during the storage period also had seed yields similar to the 10”/2”C treatment. The 10”/2”C treatment, followed by planting into the field, may approximate the natural environmental conditions from which onions were domesticated, i.e. a gradually-cooling season, a cold season, and a gradually-warming season. The storage treatments had no significant effect on the weight of individual seed, but 826 had significantly smaller seed than the other 2 inbreds. Still the seed yield of 826 was significantly greater than that of 661-20. From this study it is apparent that inbred onion lines vary in their response to- storage temperature and in their seed yield potential. Thus it is possible to select inbreds for seed yield and to some extent control components of their yields through storage temperatures. Throughout this study, inbreds 826 and 2399 responded more to the treatments than did 661-20. Both of these inbreds are mild flavored onions. On the other hand, inbred 661-20 is a highly pungent onion. It is not known whether this trait is related to the results we obtained. Accompanying the high seed yields of 2399 (which produced more seed than the other inbreds) were earlier sprouting, earlier flowering, taller seed stalks, a higher number of umbels/bulb, a higher number of florets/bulb and larger individual seed than the other inbreds. Treatments which were associated with the higher seed yields caused earlier flowering, a higher number of leaves and a higher number of umbels than the treatment associated with the lowest seed yield. Many of the traits associated with bolting, flowering and seed production of the onion plant are now known to be influenced by the storage temperature of the mother bulb. In addition, it has been shown that bulbs of different genotypes respond differently to the storage environment as it pertains to traits associated with seed yield. These traits and their effect on the yield should be further elaborated to make it possible for better commercial production of hybrid onion seed.
REFERENCES Atkin, J.S. and Davis, G.N., 1954. Altering onion flowering dates to facilitate seed production. Calif. Agric. Exp. Stn. Bull., 74. DeMille, B. and Vest, G., 1975. Flowering date of onion bulbs as affected by light and temperatue treatments during storage. J. Am. Sot. Hortic. Sci., 100: 423-424. DeMille, B. and Vest, G., 1976. The effect of temperature and light during bulb storage on traits related to onion seed production. J. Am. Sot. Hortic. Sci., 101: 52-53. Jones, H.A., 1927. The influence of storage temperature on seed production in Ebenezer onion. Bloc. Am. Sot. Hortic. Sci., 24: 61-63.
215 Jones, H.A. and Emsweller, S.L., 1939. Effect of storage, bulb size, spacing and time of planting on production of onion seed. Calif. Exp. Stn. Bull., 628. Jones, H.A. and Mann, L.K., 1963. Onions and Their Allies. InterScience, New York, 286 pages. Mital, S.P. and Srivastava, G., 1964. Seed yield in relation to bulb size and number of seed stalks in onion (Allium cepa L). Indian J. Hortic., 21: 263-269. Prokhorov, I.A. and Khomyakov, P.I., 1972. The yield and quality of onion seed in relation to flowering date. Hortic. Abstr., 1974: 7708. Steel, R.G.D. and Torrie, J.H., 1960. Principles and Procedures of Statistics. McGraw-Hill, New York, 481 pages. Van der Meer, Q.P. and Van Bennekom, J.L., 1969. Some experiences with onions for seed. Hortic. Abstr., 1969: 4887. Woyke, H, and Manczek, M., 1965. Number of seed stocks and the seed yield of several newly bred and local onion varieties as affected by the temperature at which the bulbs had been held. Hortic. Abstr., 1967: 1055.