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Combining ability for some quantitative characters in hexaploid wheat (Triticum aestivum L. em. Thell)

H. Singh, S.N. Sharma and R.S. Sain

All India Coordinated Wheat and Barley Improvement Project, Rajasthan Agriculture University, Agricultural Research Station, Durgapura-302 018, Jaipur, India.
E-mail:
snsarsdgprjpr@yahoo.com

Abstract

The F1 and F2 progenies of a ten-parent diallel cross (excluding reciprocals) were analyzed for combining ability for some quantitative traits in hexaploid wheat (Triticum aestivum L. em. Thell). The General (GCA) and specific combining ability (SCA) components of variance were significant for all traits. However, SCA component of variance was predominant indicating the predominance of non-additive gene effects for the traits studied except days to heading in both F1 and F2 generations. Among the parents, PBW 373 and UP 2425 were the best general combiners for grain yield and average to high combiners for other important traits. Parents HD 2329, WH 542, Raj 3077 and UP 2338 were the best general combiners for harvest index, grain yield per spike, early heading and dwarfness, respectively. Similar trends for GCA effects were observed in both F1 and F2 generations. The best specific crosses for grain yield were Raj 3765 HD 2285, HD 2285 PBW 343, Raj 3765 UP 2338 and PBW 343 Raj 3077. Many of the specific crosses for grain yield involved high average, average average and average poor general combiners. To ensure further increase in grain yield combinations of desirable yield components is advocated. Inclusion of F1 hybrids showing high SCA and having parents with good GCA, into multiple crosses, biparental mating, and diallel selective mating could prove a worthwhile approach for further amelioration of grain yield in hexaploid wheat.

Introduction

Further advancement in the yield of wheat requires certain information regarding the nature of combining ability of parents available for use in the hybridization program, and also the nature of gene action involved in expression of quantitative and qualitative traits of economic importance. General and specific combining ability effects are very important in constructing the next phase of a breeding programme. Diallel analysis provides a unique opportunity to test a number of parental lines in all possible combinations. Thus, the main objective of the present study was to identify the best combiners and their crosses on the basis of their general and specific combining ability for yield and its component traits.

Materials And Methods

Ten varieties of hexaploid wheat (Triticum aestivum L. Thell), namely, Raj 3765, HD 2285, UP 2425, UP 2338, PBW 373, HD 2329, WH 542, Raj 1482, PBW 343 and Raj 3077 were crossed in all possible combinations excluding reciprocals. The 10 parents and their resulting 45 F1’s and 45 F2’s were grown in a randomized block design with three replications at Agricultural Research Station, Durgapura, Jaipur, Rajasthan, India. Plots of parents and F1s consisted of two rows of 3 m length while each plot of F2 consisted of four rows with the spacing of 30 cm between rows and 10 cm between plants. Ten competitive plants in parents and F1’s and 30 plants in F2 progenies were sampled randomly. Combining ability analysis was carried out using Method II, Model I as suggested by Griffing (1956).

Results and Discussion

Analysis of variance for combining ability revealed GCA and SCA were highly significant for all traits studied in both F1 and F2 generations (Table 1). Thus, additive and non-additive gene effects were important in controlling inheritance of all characters studied. However, the GCA:SCA ratio normally favoured SCA in all the traits except for days to heading in both F1 and F2 generations indicating the preponderance of non-additive gene effects in the genetic control of traits. Other studies also indicated a preponderance of non-additive effects (Menon and Sharma 1997).

Estimates of GCA effects revealed that parents PBW 373 and UP 2425 were the best general combiners for grain yield and good to average combiners for most of the yield component characters (Table 2). However, the rest of the parents were poor combiners for grain yield and average to poor general combiners for most of the yield contributing traits. Parents HD 2329, WH 542, Raj 3077 and UP 2338 were the best general combiners for harvest index, grain yield per spike, early heading and dwarfness, respectively. Similar parental trends for GCA effects were observed in both F1 and F2 generations. Parent PBW 373 was a good combiner for early heading, tillers per plant and 1000-grain weight whereas UP 2425 was a good general combiner for early heading, tillers per plant, flag leaf area and 1000-grain weight. Therefore, there is still further scope for improving combining ability for component traits, as none of high combiners for grain yield was a high combiner or at least an average combiner for the desirable traits. Raj 3765 was a good combiner for early heading, shorter grain filling period, spikes number and harvest index; HD 2285 for early heading, dwarfness and harvest index; and Raj 1482 for dwarfness and harvest index. The parent PBW 343 was inconsistent in combining ability in both generations. However, it was a good combiner for shorter grain-filling period, flag leaf area, grain yield per plant in the F1 and dwarfness in the F2 generations. Similarly, combining ability was inconsistent for Raj 3077. However, it was a good combiner for tillers per plant, grain yield per plant in the F1, and flag leaf area and harvest index in the F2 generation. The parents PBW 373 and UP 2425 could be utilized extensively in the hybridization programme to accelerate the pace of genetic improvement of grain yield in hexaploid wheat.

Table 1. Analysis of variance showing mean squares for combining ability for different characters in hexaploid wheat

Character

GCA (9)

SCA (45)

Error (108)

GCA:SCA

F1

F2

F1

F2

F1

F2

F1

F2

Days to heading

98.54**

102.64**

7.61**

8.83**

0.51

0.50

2.13

1.87

Grain filling period

5.19**

5.11**

2.54**

3.99**

0.72

0.70

0.24

0.05

Plant height

72.96**

38.17**

36.29**

22.95**

0.94

0.93

0.17

0.11

Tillers per plant

2.06**

1.00**

1.23**

0.95**

0.05

0.05

0.12

0.01

Flag leaf area

9.69**

7.45**

21.78**

20.89**

0.71

0.70

-0.09

-0.11

Spike area

54.76**

50.92**

52.38**

50.46**

0.59

0.58

0.01

0.00

Grain yield per spike

0.208**

0.230**

0.115**

0.159**

0.01

0.01

0.15

0.81

1000- grain weight

30.24**

21.98**

18.40**

15.24**

0.84

0.82

0.11

0.07

Harvest index

44.80**

46.04**

20.17**

22.87**

1.33

1.32

0.21

0.17

Grain yield per plant

41.09**

30.18**

16.89**

16.87**

1.05

1.04

0.25

0.14

*Significant at p=0.05 and ** Significant at p=0.01

Table 2. Estimates of general and specific combining ability effects for important characters in hexaploid wheat.

Parent

Tillers per plant

Spike area

1000- grain weight

Harvest index

Grain yield per plant

 

F1

F2

F1

F2

F1

F2

F1

F2

F1

F2

P1

0.07

0.00

4.77**

4.60**

1.84**

-0.12

1.55**

1.26**

-0.63

-0.63

P2

-0.62**

-0.58**

0.67

1.04**

-2.05**

-2.13**

2.08**

1.19**

-4.27**

-3.70**

P3

0.60**

0.54**

-2.34**

-2.21**

3.08**

2.53**

-2.15**

-3.04**

1.25**

1.47**

P4

-0.08

-0.06

-3.47**

-3.30**

-0.03

-0.24

0.61

0.36

-0.55

-0.06

P5

0.51**

0.28**

-0.03

-0.29

1.12**

1.88**

-3.45**

-3.21**

1.77**

1.98**

P6

-0.56**

-0.18*

0.11

-0.08

-0.02

0.15

1.88**

1.74**

-1.64**

-1.06**

P7

-0.17*

-0.06

0.21

0.22

-1.27**

-0.93**

0.46

0.93*

0.62

0.30

P8

-0.01

0.06

0.38

0.15

-1.34**

-1.01**

1.52**

1.57**

0.95**

0.44

P9

-0.16*

-0.04

0.07

-0.03

-0.81**

-0.13

-1.89**

-2.00**

0.99**

0.25

P10

0.40**

0.04

-0.37

-0.08

-0.54

0.00

-0.59

1.20**

1.50**

1.01

SE (gI)

0.063

0.063

0.210

0.209

0.251

0.298

0.31

0.315

0.281

0.279

SE (gI-gj)

0.094

0.094

0.709

0.312

0.374

0.370

0.47

0.470

0.419

0.417

*Significant at p=0.05 and ** Significant at p=0.01; P1 = Raj 3765, P2 HD 2285, P3 = UP 2425, P4 = UP 2338, P5 = PBW 373, P6 = HD 2329, P7 = WH 542, P8 = Raj 1482, P9 = PBW 343 and P10 = Raj 3077

The estimates of SCA revealed that out of 45 crosses, 19 crosses in the F1 and 15 crosses in the F2 were found to be good specific combiners for grain yield. It is noteworthy that 14 crosses showed positive and significant SCA effects for grain yield in both F1 and F2 generations. The generation effects were also noticed in the SCA effects of the crosses. The highest positive significant SCA effect was exhibited by the cross Raj 3765 HD 2285 in both generations. Other good combinations, which showed significant SCA effects for grain yield in both the generations were HD 2285 PBW 343, Raj 3765 UP 2338, PBW 343 Raj 3077, Raj 3765 Raj 1482, PBW 373 HD 2329, PBW 373 Raj 1482, UP 2425 WH 542, UP 2425 UP 2338 and UP 2425 PBW 373 in both F1 and F2 generations. These crosses were higher yielding, and because in most crosses contained at least one good combiner parent, indicating that such combinations are expected to throw desirable transgressive segregants. All the best crosses for grain yield also showed average to high SCA effects for most of the yield components. It is, therefore, recommended that new materials should be used in future breeding efforts for recombining the desirable traits in the envisaged elite genotypes.

The study demonstrates that both additive (fixable) and non-additive (non-fixable) components of genetic variances were involved in governing inheritance although additive genetic variance was predominant. Therefore, biparental mating (Joshi and Dhawan 1966) and/or diallel selective mating (Jensen 1970) which allows intermating of selections in different cycles to exploit both additive and non-additive gene effect, could be useful in genetic improvement of characters of hexaploid wheat. Restricted recurrent selection by way of intermating the most desirable segregates followed by selection (Joshi 1979) may also prove to be an effective alternative approach to improving grain yield in this important species. Inclusion of F1 hybrids showing high SCA and having parents with good GCA, into multiple crosses, could also prove a worthwhile approach for tangible advancement of grain yield in hexaploid wheat

References

Arunachalam, V. 1976. Evaluation of diallel crosses by graphical and combining ability methods. Indian J. Genet., 36: 358-366.

Baker, R. J. 1978. Issues in diallel analysis. Crop Sci., 18: 533-536.

Griffing, B. 1956. Concept of general and specific combining ability in relation to diallel crossing system. Aust. J. Biol. Sci., 9: 463-493

Jensen, N.F. 1970. A diallel selective mating system for cereal breeding. Crop Sci., 10: 629-635.

Joshi, A.B. 1979. Breeding methodology for autogamous crops. Indian J. Genet., 39: 567-578.

Joshi, A. B. and Dhawan, N. L. 1966. Genetic improvement in yield with special reference to self fertilizing crops. Indian J. Genet., 26(A): 101-113.

Menon, U. and Sharma, S.N. 1997. Genetics of yield determining factors in spring wheat over environments. Indian J. Genet., 57(3): 301-306.

Panse, V.G. and Sukhatme, P.V. 1967. Statistical methods of agricultural workers. ICAR publication, New Delhi.

Panse, V.G. and Sukhatme, P.V. 1967. Statistical methods of agricultural workers. ICAR publication, New Delhi.

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