Maize Genetics Cooperation Newsletter vol 81 2007
Instituto
Fitotecnico de Santa Catalina
Universidad
Nacional De La Plata and CIGEN (CONICET-CIC-UNLP)
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 I2�Kl 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