Maize Genetics Cooperation Newsletter vol 81 2007

 

Breeding implication of intra- and interheterotic group crosses as a source of new inbred lines in maize

--Has, V; Has, I

 

          Advanced cycle pedigree breeding is the most common method for developing maize inbreds.  Many of the current elite maize inbreds are derived from only a few progenitor inbreds; this breeding process systematically leads to a narrow maize germplasm within heterotic groups.  Maize breeders have sometimes used commercial hybrids as a source of new inbreds.  The effects of disrupting heterotic patterns in maize, by selfing from commercial hybrids, are not well understood.

          The objective of this study was to compare intra- and interheterotic group crosses as sources of new inbred lines.  We evaluated 425 inbred lines, created at the Agricultural Research Station in Turda, Romania.  The inbred lines have been derived from different sources of germplasm using conventional breeding techniques of pedigree selection and early-generation yield testing.  We used the following sources of germplasm for inbred line development:  local varieties 3%, composites 14%, improved elite inbred lines 47% and commercial hybrids 36%.

          Twelve of these inbred lines were selected by the year when they were finalized (Table 1).  The inbred lines have been crossed with two testers--inbred lines belonging to a flint heterotic pattern.  The testcrosses were evaluated in randomised complete block design in two locations for 2 years.  Analysis of variance was performed for grain yield, stalk and root lodging, kernel dry matter and selection index (Table 2). The new elite inbred lines were crossed with more testers (7-8 inbred lines per year) from different heterotic patterns.  They were evaluated (Table 3) by their GCA for the main characters.

          The testcross means showed good results for grain yield: TC385A, TA428, TE203, TD268, TC365, TC344, TD345; stalk and root lodging resistance: TD273, TD268, TC335, TC365, TC344; kernel dry matter:  TD273, TC335, TE210, TC344, TD345, TD348; selection index: TA428, TD268, TC365, TC344, TD345.

          In conclusion:

          1) The last years were characterized by a genetic gain in inbred lines development.

          2) GCA effects for the main characters were more favourable for inbred lines derived from improved elite inbreds and commercial hybrids.

          3) The local populations would be used as sources of inbred lines only after they were improved in a special program by recurrent or reciprocal-recurrent selection.

          4) The relative usefulness of intra- versus intergroup populations as sources of new inbreds depends on the particular inbreds used and/or on finding a suitable tester.


Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of authors.

 

 

Table 1.  Turda inbred lines listed by four decades of important use.

 

Inbred line

Decade of important use

Year finalized

Source of germplasm*

Origin of initial material

Maternal inbreds (m)

T248

1961 – 1970

1964

LCS

Commercial hybrid KS3

T291

1966

RYD

Local variety Ungheni 247

T243

1965

RYD

Commercial variety VIR42

T169a

1971 – 1980

1972

RYD x ?

(W153R x W37A) x Mihalţ256

T158

1971

RYD x ?

(W153R x W37A) x Mihalt 1745

T160

1971

RYD

Commercial hybrid KC3VI

TC243

1981 – 1990

1989

WF9 Group x RYD

Commercial hybrid

TB366

1987

LSC

W182B x T248-I

TC316

1988

? x LCS

S54 x MO17

TC344

1991 – 2000

1995

RYD

Commercial hybrid

TC335

1994

(LSC x RYD) x ID

(T248 x T291) x TB329

TE203

1996

RYD

TD2612 x T291

Paternal inbreds (n)

LO3

-

ELF

Pop de Lostrano

PI187

-

ELF

PTF x Pop Italia

RYD - Reid Yellow Dent; LSC - Lancaster Sure Crop ID - Iodent; ELF - European Late Flint

 

Table 2.  Additive genetic effects (ĝm) for m=12 inbred lines, n=3; a factorial crossing system m x n (12 x 3) x 2 locations x 2 years.

 

Trait

Grain yield

Dry matter of grain at harvest

Percent of plants not stalk lodging at harvest

Selection index

Inbred lines (m)*

T2483

- 0.61

- 0.07

6.77

6.09

T2911

2.17

- 0.34

4.62

6.45

T2433

- 1.84

- 0.84

- 6.29

- 8.97

-created in �1960

- 0.28

- 1.25

5.10

3.57

T169a2

- 11.55

2.00

4.88

- 4.67

T1583

1.33

0.17

- 9.14

- 7.64

T1603

- 12.98

0.59

2.13

- 10.26

-created in �1970

- 23.20

2.76

- 2.13

- 22.57

TC2433

8.26

- 1.04

- 2.06

5.16

TB3662

- 3.07

1.09

- 4.78

- 6.76

TC3162

- 0.87

- 2.10

0.56

- 2.41

-created in �1980

4.32

- 2.05

- 6.28

- 4.01

TC3443

7.52

- 0.58

- 0.92

6.02

TC3352

4.97

0.79

2.80

8.56

TE2032

6.67

0.36

1.45

8.48

-created in �1990

19.16

0.57

3.33

23.06

DL 5%

3.14

0.40

3.47

-

*Inbred lines were derived from: 1open-pollinated varieties; 2improved elite inbred lines; 3commercial hybrids.

 

         

Table 3.  General combining ability (GCA) specific to 11 new Turda inbred lines in maize.

 

Inbred line

Year of testing

No. crosses

Grain yield (DMG = 15.5%)

Percent of plants not stalk lodged at harvest

Dry matter of grain at harvest

Selection index %*

q/ha

%*

%

%*

%

%*

Source: BK of elite inbred lines

TC385 A

1999

41

101.3

98

92.0

99

72.0

103

100

2001

27

114.6

98

91.2

99

81.3

99

95

2002

35

113.1

109

91.6

95

80.2

99

102

GCA/ TC385A

108.8

99

91.9

98

76.2

101

99

TA428

1999

66

103.5

100

92.0

99

71.9

103

102

2001

3

127.3

108

82.0

89

81.1

98

95

2002

67

110.9

106

95.0

99

79.7

98

104

GCA/ TA428

107.7

103

93.3

99

75.9

100

103

TE203

1999

35

98.7

95

92.5

100

76.6

109

104

2001

85

115.1

98

88.5

96

82.5

100

94

2002

100

100.9

97

94.3

97

81.9

101

95

GCA/ TE203

106.0

97

91.8

97

81.3

102

96

TD273

1999

13

110.2

97

91.1

98

70.6

101

96

2001

23

110.5

94

96.3

100

82.6

100

99

2003

77

81.2

97

98.6

100

84.6

100

98

GCA/ TD273

90.5

96

97.3

100

82.6

100

98

TD268

2001

91

115.2

98

97.1

106

80.8

98

102

2003

61

86.5

103

96.5

98

82.9

98

100

GCA/ TD268

103.4

100

96.9

103

81.6

98

101

TC335

1999

21

94.9

92

94.0

102

73.3

105

97

2001

34

108.4

92

93.6

102

82.4

100

94

2003

29

85.1

102

96.4

98

84.1

100

99

GCA/ TC335

97.0

95

94.7

101

80.7

101

96

TC365

1999

38

109.3

106

93.5

101

70.7

101

108

2001

22

125.2

107

97.7

106

81.5

99

112

2002

40

109.5

105

95.7

99

80.2

99

103

2003

38

88.9

106

95.8

98

84.5

100

106

GCA/ TC365

106.3

106

95.4

100

79.0

100

107

Comparison mean: Saturn, Helga (commercial hybrids)

1999

50

103.5

100

92.5

100

70.1

100

100

2001

50

117.4

92.0

82.4

2002

50

104.2

96.5

80.9

2003

50

83.8

98.2

84.4

Source : commercial hybrids

TE210

1999

29

102.6

99

92.5

100

72.9

104

103

2001

44

111.5

95

89.5

97

83.5

101

94

2003

73

86.1

103

92.2

94

85.9

102

98

GCA/ TE210

97.0

100

91.4

96

82.6

102

98

TC344

1999

70

104.0

100

94.0

102

72.8

104

106

2001

125

119.9

103

92.4

101

82.1

100

102

2002

112

111.6

107

96.6

100

80.4

99

107

2003

55

90.8

108

94.4

96

84.5

100

104

GCA/ TC344

109.8

104

94.3

100

80.1

100

105

TD345

1999

34

102.7

99

91.5

98

74.3

106

103

2001

28

112.7

96

92.0

100

83.1

101

97

2002

56

107.7

103

95.0

98

82.0

101

103

2003

37

85.3

102

91.8

93

85.0

101

96

GCA/ TD345

102.2

101

92.9

97

81.2

102

100

TD348

1999

10

102.1

99

95

103

70.2

100

101

2002

55

101.3

97

96.7

100

81.9

101

99

2003

60

84.6

101

93.1

95

84.1

100

95

GCA/ TD348

93.3

99

94.8

98

82.0

100

97

Comparison mean: Saturn, Helga (commercial hybrids)

1999

50

103.5

100

92.5

100

70.1

100

100

2001

50

117.4

92.0

82.4

2002

50

104.2

96.5

80.9

2003

50

83.8

98.2

84.4

*GCA of the Turda inbred lines has been compared with the mean of the two hybrids.