Maize Genetics Cooperation Newsletter vol 81 2007

 

 

LLAVALLOL, ARGENTINA

Instituto Fitotecnico de Santa Catalina

Universidad Nacional De La Plata and CIGEN (CONICET-CIC-UNLP)

 

Maize quality breeding in Argentina.  I. Chemical analysis of waxy maize starch

--Corcuera, VR; Caro Sol�s, C; Garcia-Rivas, G; Tortoriello, C; Salmoral, EM

 

          In 1990, a breeding program was initiated at the Instituto Fitot�cnico Santa Catalina and CIGEN, located in Llavallol, province of Buenos Aires, Argentina (22 m.a.s., 34 48�S; 58 31�W), with the purpose of obtaining new starch and quality protein genotypes.  During the first stage of the program, several maize inbreds were developed, tested and selected following the classic methodology.  These inbreds carry single recessive (wx1, o2, o5, O9, O11, sh4) or double recessive (wx1 sh4; wx1 o2) genes.  Using some of the inbreds developed, single crosses were obtained and tested in several complete randomized block design field trials with three replicates conducted in Llavallol.  During the last year, the starch composition (% amylose and % amylopectin) of twenty-six inbreds and four single crosses was analyzed through molecular fractionation (Cur� and Krisman, 1990) and spectrophotometry.  The results of the starch molecular fractionation performed in inbreds and single crosses are shown in Tables 1 and 2.  The length of the external chains of each a-D glucane may be estimated from the ratio (A) of peaks and shoulder absorbances for the polysaccharide in the presence of I2Kl in a saturated CaCl2 solution.  Long external chains of glucopolysaccharides (amylose) usually yield a high �A� value (around 2-4).  Smaller values of �A� (around 1-1.8) are typical of the short- and branched-chains of amylopectin.  Our results (Table 3) show that the amylose contained in these genotypes has some degree of branching and therefore is not completely linear.  The amylopectin of the different genotypes has a similar degree of branching and is moderately branched.  The single crosses CIG10, CIG25 and CIG45 have a higher amylopectin content (81 to 88%).  As CIG10 was obtained by crossing a �normal� inbred  (female) x wx1 (male), its endosperm genotype is Wx Wx wx.  The amylopectin content in normal maize (Wx Wx Wx) is about 70 to 75%, thus the expression of only one recessive allele (wx1) raises the content of this a-D glucane by ca. 8 to 10 %.

 

Table 1.  Starch content and composition of inbreds.

 

Genotype

Starch %

Amylose %

Amylopectin %

R

3002 a

68.8

24.2

75.5

3.2

3008

67.8

26.4

73.6

2.8

3014a

69.3

22.0

78.0

3.5

3016a

70.1

20.1

80.0

4.0

3016 b

69.2

29.3

69.9

2.4

3020/1

69.5

21.0

79.0

3.8

3020a

70.7

20.3

79.7

3.9

3022a

73.1

18.0

82.0

4.6

3022a/1

70.0

11.1

89.0

8.0

3022a/2

70.7

16.0

84.0

5.3

3022 b

69.7

15.8

84.2

5.3

3022c

69.5

18.0

82.0

4.6

3043 b

70.9

29.9

70.1

2.3

3074a

69.9

9.0

91.0

10.1

3074b

71.3

17.1

82.8

4.8

3074c

71.9

20.0

80.0

4.0

3078a

71.6

9.0

91.0

10.1

3088

70.1

25.0

75.0

3.0

3092

69.0

20.0

80.0

3.0

3096 b

70.2

17.0

82.0

4.8

3098

69.1

24.0

76.0

3.2

3109

69.4

22.0

78.0

3.6

3115

70.4

29.0

71.0

2.3

3119

69.0

21.6

78.5

3.6

3132 a

70.7

27.1

72.8

2.7

3139a

70.2

24.0

76.0

3.2

R is the ratio of amylopectin to amylose.

 

Table 2.  Starch content and composition of single crosses.

 

Genotype

Starch %

Amylose %

Amylopectin %

R

CIG10

69.6

18.8

80.7

4.3

CIG24

73.4

20.0

79.9

4.0

CIG25

71.1

12.2

87.8

7.2

CIG45

71.0

11.1

88.9

8.0

CIG47

70.0

22.0

78.0

3.5

CIG50

72.4

20.3

78.7

3.9

CIG66

71.4

29.0

71.0

2.4

R is the ratio of amylopectin to amylose.

 

Table 3.  Spectrophotometric analysis of starch molecular components.

 

 

 

AMYLOSE

AMYLOPECTIN

 

 

lmax

lmax shoulder

A

lmax

lmax shoulder

A

 

Inbred

 

 

 

 

 

 

 

3002a

590.0

415.0

1.43

497.5

408.0

1.22

 

3016b

614.0

415.0

1.48

521.0

411.0

1.27

 

3022b

560.0

415.0

1.35

494.5

410.0

1.21

 

3043b

596.0

415.0

1.44

506.0

410.0

1.23

 

3096b

617.0

414.0

1.50

490.0

408.0

1.20

 

3115

589.0

414.0

1.42

525.5

411.0

1.28

 

3132a

620.0

415.0

1.49

500.5

411.0

1.22

 

Single-cross

 

 

 

 

 

 

CIG25

567.0

415.0

1.45

496.0

412.0

1.20

 

CIG47

590.0

410.0

1.48

522.0

411.0

1.27

 

CIG50

561.0

410.0

1.45

496.0

409.0

1.21

 

CIG66

599.0

410.0

1.46

521.0

408.0

1.28

A is the ratio of absorbances at the wavelengths lmax and lmax shoulder.

 

Maize Genetics Cooperation Newsletter vol 81 2007