5. Segregation for sucrose production in corn stalks.

 

F2 and backcross progenies of the cross T1 x C 103 were grown and analyzed for production of sugar in the stalk juice. Progenies were grown both at Mt. Carmel, Connecticut, and at Yaphank, five miles from the Brookhaven National Laboratory. Sugar determinations were made by using a hand refractometer in the field. A cylinder of corn stalk was out from each stalk with a cork borer and a pair of blunt-nosed pliers was used to express a drop or two of juice onto the refractometer surface. With the Bausch and Lomb Hand Refractometer this amount of juice is sufficient for a reading with accuracy of half a per cent. Some of the samples at the Brookhaven Laboratory were analyzed for reducing sugars. There seems to be a fairly good correlation betreen refractometer reading and sucrose per cent. An excellent correlation exists in sugar cane for refractometer reading and sucrose per cent. So it is not surprising to find it in corn stalks.

 

The C 103 plants analyzed at New Haven gave readings of 10.8 to 15.3 for a total of 32 plants. At Yaphank 16 progenies ranged from 10.0 � .67 to 15.1 � .29, indicating that progress has already been made in selecting lines of C 103 that are fairly high in sucrose content.

 

The T1 lines examined at Yaphank varied from 8.1 � .77 to 9.25 � 9.6, somewhat lower than C 103. Chemical tests in 1947 showed the sugar in the stalk of T1 to be composed largely of invert sugar, whereas the sugar of C 103 is largely sucrose. Possibly the hybrid T1 x 103 was not the best choice for the study of inheritance of sucrose percentage as undoubtedly the invert sugars of the T1 would cause a higher refractometer reading than comparable C 103 lines. Segregating progenies involving other lines crossed by C 103 are available for 1949 study. Another factor that may complicate the picture somewhat is the rather high variability within the C 103 line itself, and it is not known what particular C 103 line was used as the parent of the hybrid C 103 x T1. The rather wide range among progenies of C 103 for refractometer reading indicates that even supposedly pure lines can be quite heterozygous for factors which were not selected for or against.

 

With the above limitations in mind the data are presented in table 1. They fit a normal frequency distribution rather well, indicating several factors, at least, are responsible for sugar production in the stalk juice.

 

The data in table 1 are presented to show the variability within inbred lines and also the range in segregating progenies. Plants that produce no ear or a very poor ear usually run higher in sugar than those that produce a good ear, although it should be noted that sore plants that have produced good ears also had a high refractometer reading. It is plants of this type that might eventually have commercial possibilities. By further selection within C 103 lines it should be possible to increase the sucrose content of this line.

Table 1. Refractometer readings for maize inbreds, their hybrids and segregating progenies

 

Refractometer reading - class centers at 1.5% intervals

 

Pedigree

3.3

4.8

6.3

7.8

9.3

10.8

12.3

13.8

15.3

16.8

18.3

19.8

 

C 103 (plants) Conn.

 

 

 

 

 

5

11

13

3

 

 

 

C 103 (progenies) N.Y.

 

 

 

 

1

1

3

7

4

 

 

 

 

F1 C 103 x T1 (Conn.)

 

 

 

1

4

2

7

4

1

 

 

 

F1 C 103 x T1 (N.Y.)

 

1

6

10

6

3

4

2

3

 

 

 

 

T1 Conn. (plants)

 

 

 

 

 

 

 

1

1

1

3

 

T1 N.Y. (plants)

3

5

13

9

7

5

7

3

 

 

 

 

T1 N.Y. (progenies)

 

 

 

4

1

 

 

 

 

 

 

 

   (above plants)

 

 

 

 

 

 

 

 

 

 

 

 

 

(T1 x C 103) F2 Conn.

1

10

21

24

38

36

30

11

4

1

 

 

(T1 x C 103) F2 Conn. ears

 

 

 

 

 

 

3

1

4

8

 

 

   with poor set of seed

 

 

 

 

 

 

 

 

 

 

 

 

 

(T1 x C 103) F2 N.Y.

3

10

19

32

30

34

14

6

5

0

 

 

(T1 x C 103) F2 N.Y. ears

 

 

 

1

1

4

2

4

13

5

13

7

   with poor set of seed

 

 

 

 

 

 

 

 

 

 

 

 

 

(T1�C 103) x C 103 (Conn.)

2

5

8

17

18

27

28

21

4

2

 

 

(T1�C 103) x C 103 (Conn.)

 

3

16

17

37

3

1

12

9

10

 

 

   ears with poor set of seed

 

 

 

 

 

 

 

 

 

 

 

 

 

(T1�C 103) x C 103 (N.Y.)

 

3

16

17

37

32

21

12

7

 

 

 

(T1�C 103) x C 103 (N.Y.)

 

1

1

2

1

2

1

2

2

4

2

 

   ears with poor set of seed

 

 

 

 

 

 

 

 

 

 

 

 

 

In addition, a thorough search of existing lines might reveal some with a high sucrose content. Among the few we have sampled there is great variability. In table 2 are given a few of the inbred lines already examined with the average refractometer readings found.

 

Table 2. Refractometer rending of Su Su inbred lines

 

 

 

Plants with good ears

Inbred line

Place tested

No. examined

Average

 

C 102-1

Brookhaven Laboratory

1

8.4

C 102-2

"

3

9.5

C 102-3

"

8

12.4

C 102 x 103

"

3

8.0

C 1 7 x 103

"

1

10.0

 

Kr

"

6

8.2

C 1 7

"

10

9.2

K 4

"

4

4.9

Oh. 40 B-1

"

5

4.3

Oh. 40 B-2

"

5

6.7

 

Ill. A-1

"

2

7.5

Ind. 38-11 C.T.

"

7

10.7

Ind. 38-11

"

5

9.1

Ind. WF 9

"

8

6.8

BC WF 9

"

9

7.1

 

BC WF 9-2

"

7

9.0

LK

"

6

8.1

W 22

Connecticut

12

12.9

 

With such a range in refractometer readings among the few inbred lines sampled, it seems to indicate that an extensive examination of inbred lines should be made. When more information is available on the genetics of sugar production in inbred lines of corn, it should be possible to study more adequately the physiology of sugar production, perhaps using tagged Carbon14 as a tracer in such a study. The first step is to isolate lines that are pure for sucrose production and to try to ascertain the number of factors involved. This is being investigated further.

 

We wish to thank Dr. D. F. Jones and the Connecticut Experiment Station for their co�peration in growing some of the lines and for assistance in making the refractometer readings.

 

W. Ralph Singleton