BlON ' T o l M A N AND R o n a I d ) JOHNSON1
Introduction
D u r i n g the lifetime of the American Society of Sugar Beet Technologists, many reports have been made dealing with male sterility, sell fertility, Mendelian male sterility and self sterility, as these principles are related to sugar beet breeding (3) (4) (6) (7) (9)". It is not the purpose of this p a p e r to discuss technical aspects of the principles mentioned above, but to indicate how the various "breeding tools" have been adapted to the; com- mercial production of sugar beet hybrids.
Sugar beet hybrids, made by use of a cytoplasmic male-sterile and a self-fertile inbred, were first reported by Owen in 1946 (5). In the years to follow, many new inbred lines were produced by utilizing the true self- fertile character, and as lines of promise were developed, male-sterile equivalents of these lines were produced by introducing the cytoplasmic ! male-sterility factor and then backcrossing three or four times to the inbred line.
From this type of a program, the inbred C T 9 and its male-sterile equivalent were developed. T o p crosses and true hybrids made with C T 9 demonstrated, that u n d e r controlled conditions where the male sterile could be rogued carefully, hybrids could be produced that would yield up to 125 percent of the mass selected varieties in common use* by the sugar beet industry (1) .
In 1952, Owen reported a second type of male sterility called by him, Mendelian male sterility, because its inheritance was controlled entirely by genes in the germ plasm or cell nucleus, in contrast to the major in- fluence of the cytoplasm in cytoplasmic male sterility (8) . While the F, generation of a cytoplasmic: male-sterile and a type O pollinating line was completely male sterile, the F generation of a Mendelian male-sterile and a pollinating line was completely male fertile. Owen pointed out the sig- nificance of Mendelian male sterility in producing vigorous Fl pollinators for use in the commercial production of hybrid varieties (9) .
By 1952, the only a p p a r e n t stumbling block in the way of producing cytoplasmic male-sterile hybrids on a commercial scale was the occurrence, in the C T 9 male-sterile line, of an occasional pollen producer and more frequently, plants classed as semi-male steriles, which, under some condi- tions, might produce some pollen (7) .
T h e seriousness of these semi-male-sterile plants was evaluated by both the Amalgamated and Utah-Idaho Sugar Company. Field hybrids were produced and the male sterile in one set of plots was carefully rogued, while in the other plot, no roguing was done. T h e hybrids from these two plots were then thoroughly tested in variety plots and found to be identical \ r; i General Agricultural Superintendent and Research Assistant, respectively, Utah-Idaho Sugar Company, Salt Lake City, Utah.
2 Numbers in parentheses refer to literature cited.
154 J O U R N A L OF T H E A. S. S. B. T.
in performance (10) . T h i s d e m o n s t r a t e d t h a t the semi-male steriles in CT9 were n o t of commercial i m p o r t a n c e so long as Elite seed increases were rogued carefully to keep o u t any c o n t a m i n a n t s .
Hybrids were also p r o d u c e d to c o m p a r e the value of k e e p i n g the pollinator a n d male sterile separate, as c o m p a r e d to b l e n d i n g in the pol- linator as the commercial seed increase was m a d e . S u b s e q u e n t tests of these hybrids indicated, that where commercial top cross p a r e n t s were used as pollinators, or where F p o l l i n a t o r s were used, there was no a d v a n t a g e in p l a n t i n g the male sterile a n d p o l l i n a t o r separate.
W i t h this information as a b a c k g r o u n d , the U t a h - I d a h o Sugar Company decided, in the Fall of 1953, to begin commercial p r o d u c t i o n of multigerm hybrid sugar beet seed.
M o n o g e r m H y b r i d Seed D e v e l o p m e n t
F r o m the references already cited, it is e v i d e n t t h a t m a n y of the basic principles essential to the p r o d u c t i o n of sugar beet hybrids were fairly well developed by 1948 a n d that it h a d already been d e m o n s t r a t e d , with multi- germ i n b r e d lines, t h a t hybrids of s u p e r i o r yielding ability could be pro- duced.
In the Fall of 1948, discovery of the m o n o g e r m i n b r e d lines SLC 101 a n d SLC 107 was m a d e by V. F. a n d H a l e n Savitsky (11) . D u r i n g the next six years, m o n o g e r m lines of increased curly-top resistance a n d improved seed characteristics were developed (2) (14) . Self fertility a n d male sterility were p r i n c i p a l b r e e d i n g tools used in the d e v e l o p m e n t of basic breeding stocks lor the p r o d u c t i o n of m o n o g e r m hybrids (12) . By 1954, i n b r e d lines with improved yielding ability, high sucrose c o n t e n t , a n d curly-top resistance, higher t h a n U. S. 33, h a d been released to the sugar beet industry (13) .
In 1954, a d d i t i o n a l m o n o g e r m lines, derived by V. F. Savitsky from backcrossing the m o n o g e r m lines SLC 600 a n d SLC 175 to such curly-top varieties as U. S. 2 2 / 4 a n d U. S. 3 5 / 2 , were released by the U.S.D.A. to the sugar beet industry. T h e g r o u n d was now laid for the commercial produc- tion of m o n o g e r m hybrid seed. J u s t two years after commercial production of m u l t i g e r m hybrids began, the U t a h - I d a h o Sugar C o m p a n y shifted its entire commercial seed acreage to the p r o d u c t i o n of m o n o g e r m male-sterile hybrid seed.
P r o d u c t i o n of Elite Seed Stocks
Elite seed increases of cytoplasimc m a l e steriles a r e m a d e on isolated plots of a b o u t .5 acres in size. T h e following p l a n t i n g p a t t e r n is q u i t e gen- erally followed: 2 rows p o l l i n a t o r ; 2 rows b l a n k ; 12 rows m a l e sterile; 2 rows blank; 2 rows pollinator, etc. T h i s p l o t is r o g u e d carefully to eliminate pollen producers and as m a n y as possible of the semi-male steriles. In cases where m o n o g e r m elite stocks are b e i n g r e p r o d u c e d , the p l o t is also carefully rogued for m u l t i g e r m plants. All r o g u i n g is d o n e as early as possible to p r e v e n t p o l l i n a t i o n from u n d e s i r a b l e p l a n t s . R o g u i n g is facilitated if plants in the male-sterile strips are t h i n n e d to singles in the early spring.
Stock Seed Increases Stock seed increases are made on fields of from 5 to 10 acres in
size. The general planting scheme, as used with Elite seed plots, is followed.
VOL. IX. No. 2, J U L Y 1956 1.1 Stock seed fields are too large to make detailed roguing practical. Some roguing in monogerm stock seed increases may be done to eliminate stray multigerm plants. Contamination with occasional multigerm seed will possibly not be eliminated until multigerm seed is no longer being handled in any of the same e q u i p m e n t that is being used for monogerm seed.
As stock seed increases are being made, it is important that the male sterile, being produced for planting commercial seed acreage, has good vigor.
T h i s can, of course, be accomplished by producing an F, male sterile for commercial seed production. T h i s can be illustrated by an actual example.
In 1952, 610 MSmm x 610 mm was increased at Saint George. In 1953, 610 MS x 91 mm was increased in Saint George. In 195-1 (610 MS x 91 mm) x 91 mm was increased at both Saint George and in Oregon. In the Fall of 1955, the monogerm stock seed increases were (610 MS x 91 mm x 91 mm) x 108 mm. T h e Elite seed plot in Saint George, planted in the Fall of 1955, was (610 MS x 91 mm x 91 mm) x 117 mm and. in the Fall of 1956. the stock seed plot will be planted using this MS and 108 mm as the pollinator. All of these monogerm inbreds, except SLC 117 mm, were developed by V. F. Savitsky, working in cooperation with the lieet Sugar Development Foundation and the Sugar Crops Section of the United States Department of Agriculture. The SLC 117 mm inbred line was developed by Owen.
Use of these respective lines so as to keep the male-sterile seed in the
Fi generation insures a vigourous male sterile for both stock seed and com- mercial seed acreage.
Pollinators for Hybrid Seed
In producing C T 9 hybrids, two types of pollinators have been used:
Commercial varieties as top-cross parents and F, pollinators produced by using the SLC 824 aa Mendelian Male sterile.
Figure 1.—Elite seed plot for production of Ft pollinator. T h e 824 aa _. mendelian m a l e sterile pollinator strips on each side were 12-rows wide.
The pollinator variety was a sugar selection of SLC 202. Approximately 60 percent of the p l a n t s were rogued from the 824 aa strip.
156 J O U R N A L OF T H E A. S. S. B. T.
In p r o d u c i n g m o n o g e r m hybrids we have used almost exclusively Ft
pollinators. Variety test results indicate t h a t the F1 824 aa x C T 9 is one of the best we have used to d a t e .
T h e p r o d u c t i o n of F1 p o l l i n a t o r s is a r a t h e r tedious p r o c e d u r e because all the M e n d e l i a n male-sterile p l a n t s m u s t be inspected for sterility while still in the b u d stage a n d a p p r o x i m a t e l y 50 p e r c e n t of t h e p l a n t s r o g u e d out.
However, we have found it practical to p r o d u c e 500 to 600 p o u n d s of F1
p o l l i n a t o r in any o n e year (Figure 1) .
In p r o d u c i n g hybr id seed of e i t h e r m u l t i g e r m or m o n o g e r m , we have dyed the p o l l i n a t o r a n d then m i x e d it with the male sterile in the ratio of one p o u n d of p o l l i n a t o r to twenty p o u n d s of male sterile.
Practical Results of Hybrid Seed Program
Detailed data o b t a i n e d from extensive field trials are i n c l u d e d in another p a p e r a n d will n o t be r e p e a t e d h e r e . H o w e v e r , a s u m m a r y of the data p e r t a i n i n g to four of the C T 9 hybrids is shown in T a b l e 1.
T h e figures shown in T a b l e 1 are averages of four C T 9 hybrids as compared to 5 a n d 6 of what m i g h t be listed as l e a d i n g commercial vari- eties. In each case several of the commercial varieties were used as top- cross pollinators in m a k i n g the C T 9 hybrids t h a t were averaged for com- parison. It will be n o t e d t h a t the C T 9 hybrids gave an e n c o u r a g i n g per- formance at all locations.
It was also interesting to n o t e the p e r f o r m a n c e of top-cross hybrids as compared to the commercial top-cross p o l l i n a t o r p a r e n t . T h e s e com- parisons are given in T a b l e 2.
Table 1.—Comparison of the Average Performance of Commercial Varieties With the Performance of CT9 Male-Sterile Hybrids.
Location and Comparison Washington
Average Commercial Average Male-Sterile Idaho
Average Commercial Average Male-Sterile Garland
Average Commercial Average Male-Sterile So. Dakota
Average Commercial Average Male-Sterile Nebraska
Average Commercial Average Male-Sterile Combined Averages
Commercial varieties Male-Sterile Hybrids
Variety1
Hybrid Variety Hybrid Variety Hybrid Variety Hybrid Variety Hybrid
Tons Per Acre
19.46 20.72 20.93 22.19 21.44 22.58 17.86 19.80 17.64 18.28 19.47 20.71
Sucrose Percentage
15.56 15.69 18.43 18.31 14.75 14.72 15.05 15.02 15.00 15.06 15.76 15.76
Gross Sugar Per Acre
6060 6502 7714 8126 6324 6648 5376 5948 5292 5482 6153 6541
1 T h e six Commercial Varieties compared in these tests were:
In Idaho, Nebraska, South Dakota—U. S. 35/2; U. S. 22/3; SLC 202; G. W. 359; Klein E- and American No. 2-
In Utah and Washington—U. S. 35/2, U. S. 22/3, SLC 202, and Sugar Selection SLC 202
It will be noted that in every case the hybrids were higher than the top-cross pollinators in yield, although the hybrid with Klein E was not significantly higher than the Klein E parent. T h e increase in tonnage was strikingly higher when high sugar top-cross parents were used as compared to when tonnage type varieties were used as the top-cross parent.
T h e s e same relationships were obtained when the monogerm 610 MS was used -in hybrids with these same top-cross parents. These results are shown in T a b l e 3. It should be noted that the hybrids with the monogerm 6J0 MS gave the same percentage increase over the top-cross pollinator par- ents as did the multigerm hybrids with C T 9 .
In both T a b l e 2 and T a b l e 3, data are listed for a three-way hybrid where- SI.C 824 aa Mendelian male sterile was used to produce an F, pol-
: lifiator for the main purpose of increasing the sucrose percentage of the .„ Jhyferid. A further summary of the effect of introducing a high sugar variety -):i?fti€d the pollinator is shown in T a b l e 4. It is evident from these data, yf&0skt t h e use of SLC 824 aa to produce an F1 pollinator did increase the
3fc
158 J O U R N A L OF T H E A. S. S. B. T.
sucrose percentage, b u t it also decreased t o n n a g e sufficiently to result in less gross sugar p e r acre. T h i s does n o t m e a n t h a t some c o m b i n a t i o n s can- not be made where results would be m o r e favorable, or t h a t a different Mendelian male sterile m i g h t n o t react differently.
Table 4.—Comparison of Two-Way and Three-Way Hybrids Based on Results with G.W. 359 and Klein E Hybrids Planted at Four Locations.
Tons Beets Sucrose Percentage Gross Sugar Location Two-Way Three-Way Two-Way Three-Way Two-Way Three-Way
of Test Hybrids Hybrids Hybrids Hybrids Hybrids Hybrids Shelley, Idaho
8 Replications 8 Replications 8 Replications 8 Replications ebraska
12 Replications 12 Replications outh Dakota
12 Replications 12 Replications arland, Utah
15 Replications 21.93 21.50 23.58 22.68 17.75 20.31 21.64 21.90 24.01
22.69 19.82 20.26 18.32 18.52 18.79 19.19 18.37 22.25
17.77 17.20 17.81 17.33 15.01 14.54 14.98 14.53 14.14
18.41 17.79 18.31 17.26 15.08 14.86 15.08 14.85 14.51
7794 7396 8400 7860 5328 5906 6484 6364 6790
8354 7052 7420 6324 5586 5584 5788 5456 6456 Combined Average
of 95 Plots 21.70 19.80 15.92 16.24 6910 6432
C o m m e r c i a l Seed Acreage P l a n t e d in 1955
In the Fall of 1955, 588 acres of sugar beet seed were p l a n t e d for the purpose of p r o d u c i n g commercial m o n o g e r m hybrids. Based on monogerm seed yields o b t a i n e d in 1954, this acreage should p r o d u c e well in excess of 1,000,000 p o u n d s of m o n o g e r m seed. T h i s seed will be harvested in 1956 a n d will be p u t to commercial use in 1957 a n d 1958. No d a t a are available on the performance of the exact hybrids b e i n g p r o d u c e d . H o w e v e r , we have already seen in c o m p a r i n g d a t a in T a b l e s 2 a n d 3 that, w h e n the same pollinators were used, hybrids with C T 9 MS a n d 610 MS were very similar.
D a t a are available on the p o l l i n a t o r s used for the 1955 seed p l a n t i n g s . The M o n o g e r m male sterile used in the seed p l a n t i n g s was 91 MS r a t h e r than the 610 MS, for which d a t a are available. However, from available data (1954 G o v e r n m e n t R e p o r t to Beet Sugar D e v e l o p m e n t F o u n d a t i o n ) the 91 MS averaged 103 p e r c e n t of 610 MS in b o t h yield a n d sucrose percentage.
We can expect, therefore, t h a t hybrids p r o d u c e d using 91 MS will, in gen- eral, be three percent b e t t e r t h a n hybrids p r o d u c e d using 610 MS.
Actual performance of the p o l l i n a t o r s used in 1955 seed plantings of 610 MS hybrids a n d their calculated p e r f o r m a n c e with 91 MS are shown in T a b l e 5. T h e s e d a t a indicate t h a t m o n o g e r m hybrids, n o w p l a n t e d for seed p r o d u c t i o n , will exceed the present commercial variety in both ton- nage a n d sucrose percentage a n d t h a t their p e r f o r m a n c e will be equal to the best C T 9 hybrids which we have p r o d u c e d .
1 6 0 J O U R N A L OF T H E A. S. S. B. T.
(6) O W E N , F. V. 1948. Utilization of male sterility in b r e e d i n g superior varieties of sugar beets. Proc. Araer. Soc. Sug. Beet T e c h . p p . 156-161.
(7) O W E N , F. V. 1950. T h e sugar beet breeder's p r o b l e m of establishing male-sterile p o p u l a t i o n s for hybridization purposes. Proc. Amer.
Soc. of Sug. Beet T e c h . p p . 191, 194.
(8) O W E N , F. V. 1952. M e n d e l i a n male sterility in sugar beets. Proc.
Amer. Soc. Sug. Beets T e c h . p p . 371-376.
(9) O W E N , F. V. 1954. H y b r i d sugar beets m a d e by utilizing b o t h cyto- plasim cand m e n d e l i a n male sterility. Proc. Amer. Soc. Sugar Beet T e c h . VIII (2) :64.
(10) R U S H , GEORGE E. 1952. T h e relative performance of some non-rogued male-sterile hybrids. Proc. A m e r . Soc. Sug. Beet T e c h . p p . 65-69.
(11) SAVITSKY, V. F. 1950. M o n o g e r m sugar beets in t h e U n i t e d States.
Proc. Amer. Soc. Sug. Beet T e c h . p p . 156-159.
(12) SAVITSKY, V. F. 1952. M e t h o d s a n d results of b r e e d i n g work with m o n o g e r m beets. Proc. Amer. Soc. Sug. Beet T e c h . p p . 344-359.
(13) SAVITSKY, V. F., RYSER, G E O . K. 1954. Sugar c o n t e n t in mono- and m u l t i g e r m sugar-beet hybrids, carrying the gene m isolated from Michigan H y b r i d 18 a n d the gene m from variety U. S. 2 2 / 3 . Proc.
Amer. Soc. Sug. Beet T e c h . VIII (2) : 23-28.
(14) SAVITSKY, V. F., M U R P H Y , A L B E R T M . 1954. S t u d y of i n h e r i t a n c e for curly-top resistance in hybrids between M o n o - a n d M u l t i g e r m beets.
Proc. Amer. Soc. Sug. Beet T e c h . VIII (2) : 34-44.