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Euphytica

, Volume 165, Issue 2, pp 279–291 | Cite as

Phenotypic diversity in cold-tolerant peanut (Arachis hypogaea L.) germplasm

  • H. D. Upadhyaya
  • L. J. Reddy
  • S. L. Dwivedi
  • C. L. L. Gowda
  • S. Singh
Open Access
Article

Abstract

Tolerance to low temperature is an important prerequisite for optimal performance of peanut (Arachis hypogaea L.) in a number of temperate peanut-growing environments. One hundred fifty-eight peanut accessions belonging to five botanical types, known to be tolerant to low temperature (12°C) at germination, were evaluated for phenotypic diversity for 15 morphological traits in the 2001 rainy season and for 15 agronomic and two seed quality traits in the 2001 rainy and 2001/2002 post-rainy seasons. Analysis of data, using the residual maximum-likelihood approach indicated that variance components due to genotypes were significant for all traits in the rainy and for all but two traits in the post-rainy season. Clustering based on scores of nine principle components delineated four clusters. The cold-tolerant genotypes and the standard control cultivars in the four clusters differed in mean, variance, and range both during rainy and post-rainy seasons for a range of agronomic traits, indicating the diversity among the clusters. The cold-tolerant accessions were superior to control cultivars for several agronomic traits compared with their respective controls in both the rainy and post-rainy seasons, so their use in breeding should result in genetically diverse cold-tolerant high-yielding peanut cultivars.

Keywords

Groundnut Cold tolerance Genetic diversity Principal component analysis 

Introduction

Peanut (Arachis hypogaea L.), also known as groundnut, is an important tropical legume grown for both oil production and human food, as it provides a good source of energy, protein, minerals, and vitamins. Peanut production environments are characterized by a warm, frost-free period of at least 90 days (Bunting et al. 1985), with mean temperatures between 24°C and 33°C, which is the optimum range for growth and dry-matter production (Ketring 1984). The peanut plant shows maximum growth at 28°C but experiences severe metabolic perturbations below 12°C (Bell et al. 1994a). Low temperature results in slow growth of both hypocotyl/radicle and epicotyl (Ketring et al. 1982). Night temperature determines both leaflet CO2 exchange rate, regardless of day temperature, and the efficiency of use of intercepted photosynthetically active radiation (Sinclair et al. 1993; Bell et al. 1994b). Low soil temperature delays pod initiation, and reduces number of mature pods/seeds, and seed weight (Golombok and Johanson 1997).

The importance of cold tolerance in peanut is well recognized for specific production environments in North America (Benedict and Ketring 1972; Singleton and Pattee 1989; Bell et al. 1994a), Australia (Bell et al. 1991), India (Bhagat et al. 1992), and China (Fu et al. 1988). A few cold-tolerant early-maturing cultivars with ability to germinate in cooler soils have been released in Canada (Agriculture Canada 1984, 1989). The low temperatures (<18°C) at sowing in the winter peanut crop in India result in slow seedling emergence and poor plant stand. Delay in seedling emergence extends crop duration beyond 120 days, exposing the crop to high temperatures at reproductive phase and pod damage due to early onset of monsoon rains (Bhagat et al. 1988). Poor germination due to low temperatures in spring-sown peanut crop has also been reported in China, Nepal, and Vietnam (Fu et al. 1988; Koirala 1996; Dan and Hong 1996). Identification and incorporation of cold tolerance are therefore important peanut breeding objectives in these countries.

Upadhyaya et al. (2001) screened 1,704 peanut core collection accessions (Upadhyaya et al. 2003) and four control cultivars (Gangapuri, M13, ICGS 44, and ICGS 76), using rolled paper towel testing (Ellis et al. 1985) for ability to germinate in an incubator set at 12°C day-night temperature. Seeds of hypogaea and hirsuta were treated with ethrel (2-chloroethylphosphonic acid) to break seed dormancy prior to cold-tolerant test. A sufficient quantity of distilled water was added to the tray so as to keep wet the 3–4 cm of paper rolls. The number of germinating seeds was recorded at 10 (fastigiata, vulgaris, aequatoriana, and peruviana types) and 15 (hypogaea and hirsuta types) days after incubation. The hypogaea types that showed less than 70% germination were retested, with the seed stored for at least 6 months, to avoid discrepancies that could arise due to seed dormancy. This experiment was repeated with the same number of entries during the 2000/2001 post-rainy season. In both seasons, accessions that showed 80% or higher germination for one seed source but not less than 70% from either seed source were considered tolerant to low temperature at germination. Based on two seasons’ evaluation, 158 peanut core collection accessions were identified as tolerant to low temperature (12°C), on the basis of 80% or higher germination for the best seed source and not less than 70% from the second source. Mean percentage seed germination in cold-tolerant entries ranged from 76% to 96%, compared with 36% to 55% in controls (M13, ICGS 44, and ICGS 76); the fourth control, Gangapuri, had 87% germination at 12°C (Table 1).
Table 1

Identity, country of origin, and germination (%) at 12°C in 1999/2000 and 2000/2001 post-rainy seasons harvested seeds in 158 cold-tolerant germplasm and control cultivars in peanut

Identity

Origin

Germination (%)

1999/2000 post-rainy

2000/2001 post-rainy

Mean

var. aequatoriana

ICG 7898

Ecuador

86

78

82

ICG 12553

Ecuador

90

86

88

ICG 12625

Ecuador

88

78

83

ICG 12719

Ecuador

84

76

80

var. fastigiata

ICG 115

India

86

100

93

ICG 282

USA

98

98

98

ICG 318

Brazil

82

88

85

ICG 376

Argentina

94

84

89

ICG 389

South Africa

92

88

90

ICG 397

USA

94

82

88

ICG 398

USA

92

80

86

ICG 445

Tanzania

82

96

89

ICG 457

USA

92

86

89

ICG 1158

India

92

94

93

ICG 1256

Uganda

86

100

93

ICG 1274

Indonesia

84

92

88

ICG 1298

Unknown

84

100

92

ICG 1384

Tanzania

86

98

92

ICG 1399

Malawi

92

70

81

ICG 1683

South Africa

94

72

83

ICG 1796

Senegal

94

98

96

ICG 1824

Zaire

90

84

87

ICG 1899

Uganda

92

98

95

ICG 1908

India

90

76

83

ICG 2039

Unknown

82

70

76

ICG 2057

China

88

94

91

ICG 2145

Sudan

90

76

83

ICG 2158

Uganda

98

75

87

ICG 2159

Sierra Leone

88

88

88

ICG 3125

Sudan

90

80

85

ICG 3219

Tanzania

88

94

91

ICG 3477

India

86

100

93

ICG 3510

Argentina

90

72

81

ICG 3726

India

92

96

94

ICG 3779

Tanzania

86

72

79

ICG 4087

USA

88

90

89

ICG 4670

Sudan

96

92

94

ICG 4788

Benin

82

92

87

ICG 4890

Argentina

94

98

96

ICG 4992

USA

94

92

93

ICG 5094

Brazil

84

86

85

ICG 5475

Kenya

94

88

91

ICG 5609

Sri Lanka

90

92

91

ICG 5964

Zimbabwe

86

92

89

ICG 6022

Sudan

96

92

94

ICG 6148

USA

98

94

96

ICG 6203

Zimbabwe

86

90

88

ICG 6220

Brazil

88

94

91

ICG 6221

Brazil

86

84

85

ICG 6340

Honduras

90

90

90

ICG 6421

Malawi

86

88

87

ICG 6565

Unknown

84

96

90

ICG 6570

Unknown

96

100

98

ICG 6706

Brazil

90

84

87

ICG 6725

Argentina

90

94

92

ICG 6878

Argentina

98

98

98

ICG 6888

Brazil

94

100

97

ICG 7005

Brazil

88

100

94

ICG 7013

India

86

92

89

ICG 7285

Zimbabwe

98

94

96

ICG 7352

Peru

94

96

95

ICG 7355

Paraguay

90

96

93

ICG 7777

Unknown

84

98

91

ICG 7812

Brazil

82

86

84

ICG 7884

Israel

96

92

94

ICG 7905

Zimbabwe

94

88

91

ICG 7929

Paraguay

94

100

97

ICG 7978

Russia & CIS

92

100

96

ICG 8360

Thailand

84

98

91

ICG 8485

Zimbabwe

84

74

79

ICG 8514

South Africa

84

84

84

ICG 8517

Bolivia

86

94

90

ICG 8570

Argentina

92

88

90

ICG 9141

Zaire

88

96

92

ICG 9144

Syria

84

98

91

ICG 9929

Zimbabwe

88

96

92

ICG 10075

Peru

90

70

80

ICG 10092

Zimbabwe

88

76

82

ICG 10371

Nigeria

84

92

88

ICG 10402

USA

84

78

81

ICG 10481

Venezuela

82

82

82

ICG 10495

Paraguay

90

72

81

ICG 10519

Australia

86

80

83

ICG 10549

Argentina

96

90

93

ICG 10554

Argentina

90

82

86

ICG 10566

Congo

92

94

93

ICG 10595

Brazil

86

80

83

ICG 10616

Argentina

98

92

95

ICG 10788

Tanzania

92

96

94

ICG 10900

Peru

84

98

91

ICG 11130

Brazil

94

74

84

ICG 11203

India

86

90

88

ICG 11605

Bolivia

86

70

78

ICG 12498

Brazil

92

74

83

ICG 12564

Uruguay

92

70

81

ICG 12665

Peru

88

88

88

ICG 12743

Bolivia

92

96

94

ICG 12963

Zimbabwe

86

90

88

ICG 13049

India

90

86

88

ICG 13097

Unknown

96

80

88

ICG 13284

Brazil

92

98

95

ICG 13288

Brazil

98

94

96

ICG 13430

Chad

92

82

87

ICG 13513

Central African Republic

90

98

94

ICG 13829

Uganda

90

78

84

ICG 14007

Central African Republic

82

70

76

ICG 14696

Brazil

90

92

91

var. hypogaea

ICG 956

India

86

72

79

ICG 1975

Sudan

96

74

85

ICG 2422

India

88

70

79

ICG 2506

India

96

76

86

ICG 2777

India

98

73

86

ICG 2925

India

86

71

79

ICG 3877

India

98

76

87

ICG 3987

India

100

76

88

ICG 4243

Australia

94

72

83

ICG 4250

Senegal

88

71

80

ICG 4331

India

96

76

86

ICG 4738

United Kingdom

90

76

83

ICG 5163

Brazil

98

78

88

ICG 5233

Israel

90

70

80

ICG 6143

USA

82

76

79

ICG 6361

India

96

75

86

ICG 6515

Israel

100

72

86

ICG 6686

China

86

84

85

ICG 7458

Nigeria

92

82

87

ICG 7932

South Africa

86

71

79

ICG 8748

Russia & CIS

100

82

91

ICG 8833

USA

92

70

81

ICG 8835

USA

94

70

82

ICG 9037

Côte d’Ivoire

98

70

84

ICG 9515

Mozambique

96

74

85

ICG 9556

Mozambique

92

72

82

ICG 9695

India

82

70

76

ICG 9873

Zambia

94

94

94

ICG 10105

Chad

86

82

84

ICG 10575

Israel

94

82

88

ICG 11109

Taiwan

98

80

89

ICG 11456

India

94

76

85

ICG 12360

India

100

83

92

ICG 13539

Togo

98

71

85

ICG 13724

Niger

88

70

79

var. peruviana

ICG 1709

Peru

96

94

95

ICG 1710

Peru

90

96

93

ICG 7293

Peru

94

92

93

ICG 10036

Peru

90

90

90

ICG 10037

Peru

82

100

91

ICG 10567

Peru

92

92

92

ICG 10911

Peru

86

82

84

ICG 10915

Peru

84

84

84

ICG 10945

Peru

88

96

92

ICG 11088

Peru

92

100

96

ICG 12112

Peru

92

94

93

var. vulgaris

ICG 1364

India

86

80

83

ICG 1988

Brazil

96

82

89

ICG 2344

USA

88

78

83

ICG 4749

Argentina

84

82

83

ICG 14966

Unknown

92

73

83

Control

    

Gangapuri (ICG 2738)

India

84

90

87

ICGS 44 (ICG 13941)

India

43

66

55

ICGS 76 (ICG 13942)

India

50

42

46

M-13 (ICG 156)

India

50

22

36

Trial mean (1,708 entries)

 

57.9

48.5

53.2

SE±

 

10.69

7.253

6.20

CV (%)

 

32.33

18.46

14.5

LSD (P = 0.05)

 

20.95

20.14

17.2

The present study was done to characterize phenotypic diversity for morphological and agronomic traits in the 158 cold-tolerant germplasm to identify genetically diverse accessions for use in peanut breeding to improve cold tolerance at germination.

Materials and methods

One hundred fifty-eight cold-tolerant peanut accessions, representing five botanical types (4 aequatoriana, 103 fastigiata, 11 peruviana, 5 vulgaris, and 35 hypogaea) and four released Indian control cultivars (Gangapuri, M13, ICGS 44, and ICGS 76) were evaluated for 15 morphological traits in field plantings in the 2001 rainy season and for 15 agronomic and two seed quality traits in the 2001/2002 post-rainy season at ICRISAT, Patancheru, India. Gangapuri (ICG 2738) belongs to subsp. fastigiata var. fastigiata (Valencia type) and matures in about 100 days. ICGS 44 (ICG 13941) belongs to subsp. fastigiata var. vulgaris (Spanish type), matures in about 120 days, and is adapted to the irrigated post-rainy season. Both M13 (ICG 156) and ICGS 76 (ICG 13942) belong to subsp. hypogaea var. hypogaea (Virginia type), mature in 120–135 days, and are adapted to rainy season conditions.

The experiment was conducted in an alpha design (Paterson and Williams 1976) with two replications in the rainy season and three replications in post-rainy season. Each accession was sown in a one row plot of 4 m length, with 60 cm between rows and 10 cm between plants in both the seasons. Morphological descriptors used included growth habit, branching pattern, stem color, stem hair, leaflet color, leaflet shape, leaflet hair, flower color, streak color on flower, peg color, seeds per pod, pod beak, pod constriction, pod reticulation, and primary seed color (IBPGR and ICRISAT 1992). Ten mature pods were randomly selected to record data on pod beak, constriction, and reticulation. Days to emergence, days to 50% flowering, pod yield per plot, pod length and width, seed length and width, and shelling percentage were recorded on a plot basis; number of primary branches, plant height, leaflet length and width, pods per plant, and pod yield per plant were recorded on five competitive plants; seeds per pod, and pod length and width were recorded on ten randomly selected mature pods; seed length and width were based on ten mature seeds; shelling percentage was on 200 g pods; and seed weight was of 100 randomly selected mature seeds. Oven-dried (100°C, 16 h) bulked seed samples were used to determine oil and protein contents in both the seasons. Oil content was determined using a magnetic resonance spectrometer (Jambunathan et al. 1985), and data was corrected to uniform 50 g kg−1 seed moisture content. Nitrogen concentration was determined by Technicon Autoanalyser (Pulse Instrumentation Ltd., Saskatoon SK) and then multiplied by 5.46 to convert nitrogen into crude protein content (Singh and Jambunathan 1980).

Data were analyzed by the residual maximum-likelihood (REML) mixed model method with genotypes as random and environments (seasons) as fixed in GENSTAT 9.1 (Payne et al. 2006). The best linear unbiased predictors (BLUPs) were calculated for 15 agronomic and two quality traits. Homogeneity of variances in two seasons was tested by the Bartlett’s test of homogeneity (Bartlett 1937). Meta-analysis of two seasons’ data was performed when variances were heterogeneous. The components of variance due to the various botanical types as a group and individually and their interactions with season were also estimated for all traits to determine if the botanical types differed or interacted with environment. Also a comprehensive genotype-by-environment analysis, considering all genotypes as one group, was done, and the variance components due to genotype (σ g 2 ), genotype-by-environment (σ ge 2 ), and residual variance (σ e 2 ) and their standard errors were calculated.

A phenotypic distance matrix was created by calculating the differences between all pair of accessions using all the descriptors. The diversity index was calculated by averaging all the differences in the phenotypic values for each trait divided by its respective range (Johns et al. 1997).

The mean observations of all traits for each environment were standardized by subtracting from each observation the mean value of the character and dividing by its respective standard deviation, providing standardized values for each trait with an average of 0 and standard deviation of 1. The standardized values were used for principal component analysis (PCA) using GENSTAT 9.1 (Payne et al. 2006). Cluster analysis was performed using scores of the first nine principal components (Ward 1963). Means and variances for quantitative traits in the different clusters were calculated. Differences for means among the clusters were tested using the Newman-Keuls procedure (Newman 1939; Keuls 1952) while the homogeneity of variances among the clusters was tested using Levene’s test (Levene 1960).

Results and discussion

Analysis based on botanical varieties

REML analysis indicated that the effect of season was highly significant for all agronomic traits (P ≤ 0.001–0.005), except for the number of primary branches. The effect of botanical variety was also highly significant (P ≤ 0.001–0.003) for all traits, except pod and seed width, and 100-seed weight. The season × botanical variety interaction was significant for nine traits (P ≤ 0.001–0.035), and nonsignificant for six traits (days to flowering, plant height, pod width, seed length, shelling percentage, and seed weight). In the 2001 rainy season, the effect of botanical variety was significant for five traits (leaf and pod length, seed width, plot yield, and shelling percentage) while in the 2001/2002 post-rainy season botanical variety was significant for all traits except for pod and seed width, shelling percentage, and seed weight (data not sown).

Estimates of components of variance for agronomic traits

Genotypic variance (σ g 2 ) was significant for 15 traits in 2001 rainy season and for 13 traits in 2001/2002 post rainy-season (Table 2). In the combined analysis (meta analysis) genotypic variance was significant for primary branches, plant height, leaflet length, leaflet width, seed width, and 100-seed weight (Table 2). Genotype-by-environment (σ ge 2 ) interaction was significant for all 15 traits.
Table 2

Estimates of variance components due to genotype (σ g 2 ) and genotype × environment (σ ge 2 ) and their standard errors (SE) for 15 quantitative traits in the 2001 rainy and 2001/2002 post-rainy seasons and combined analysis in cold-tolerant peanut germplasm evaluated at ICRISAT, Patancheru, India

Trait

2001 rainy season

2001–02 post-rainy season

Combined analysis

σ g 2

SE

σ g 2

SE

σ g 2

SE

σ ge 2

SE

Time to 50% emergence (days)

0.295

0.060

0.176

0.049

0.025

0.041

0.289

0.056

Time to 50% flowering (days)

8.329

0.970

2.547

0.534

0.046

0.622

6.512

0.854

Primary branch (no.)

0.338

0.050

0.024

0.147

0.019

0.062

0.295

0.077

Plant height (cm)

37.990

4.820

9.742

1.226

4.885

2.313

21.272

2.279

Leaflet length (mm)

31.590

4.260

24.580

3.104

6.620

3.330

30.240

3.920

Leaflet width (mm)

1.705

0.310

2.188

0.328

0.630

0.293

2.173

0.343

Pods per plant (no.)

3.775

0.820

3.710

1.250

<0.001

<0.01

4.850

0.770

Pod length (mm)

15.110

2.120

19.749

2.492

2.470

1.800

16.660

2.260

Pod width (mm)

0.818

0.110

2.340

1.720

<0.001

<0.01

1.733

0.238

Seed length (mm)

1.822

0.260

1.811

0.237

0.215

0.185

1.733

0.238

Seed width (mm)

0.175

0.040

0.192

0.035

0.056

0.025

0.124

0.029

Pod yield per plant (g)

2.592

0.670

10.440

2.070

0.340

0.830

5.390

1.230

Pod yield per plot (kg h−1)

29123.000

5135.000

256426.000

35076.000

30170.000

16270.000

155732.000

19871.000

Shelling percentage

15.120

2.590

11.430

1.960

1.740

1.560

11.560

2.070

100 seed weight (g)

22.610

3.570

46.470

6.060

6.580

3.240

26.450

3.840

Performance of cold-tolerant germplasm for agronomic traits

Accessions from fastigiata, aequatoriana, and peruviana (subsp. fastigiata) groups were compared with the control cultivar Gangapuri; accessions from vulgaris (subsp. fastigiata) were compared with control cultivar ICGS 44; and those belonging to hypogaea (subsp. hypogaea) were compared with with control cultivars ICGS 76 and M13. Table 3 lists the accessions with superior performance over their respective controls for various traits among different botanical varieties in the rainy and post-rainy seasons and across seasons. Of these, only 41 accessions from the five botanical varieties were significantly superior to their respective controls for 1–3 traits in the combined analysis. For example, 15 accessions were superior to the controls for pod yield (ICG#10915, 10567, 1710, 11088, 10945, 12625, 7898, 11130, 6148, 6022, 7013, 7905, 7884, 9515, and 4992), 5 for faster seed emergence (ICG#2422, 1364, 2344, 4749, and 1988), 1 for days to 50% flowering (ICG 14966), 9 for oil (ICG# 8833, 9695, 10575, 10036, 11203, 6340, 13513, 13430, and 14007) and 11 for protein (ICG# 9556, 8835, 9515, 10105, 4331, 1256, 1975, 7355, 398, 8485, and 1384) contents, 3 for pod yield and seed weight (ICG#1710, 6022, and 6148), and 1 each for pod yield and protein content (ICG 9515), seed weight and protein content (ICG 8485), and for seed weight and oil content (ICG 14007). However, only ICG# 12625, 10567, 1710, 10945, and 11088 were significantly superior for pod yield in both seasons. The variable performance of many accessions was mainly due to the significant genotype-by-environment interaction observed for most traits (Table 2).
Table 3

Accessions better or significantly better for various traits compared with their respective control cultivars in the 2001 rainy and 2001-2002 post-rainy seasons and combined analysis

Trait

2001 rainy season

2001–2002 post-rainy season

Combined

Emergence

FSTa: 1899, 6725, 7005, 7812, 3125, 13097, 115, and 3219f

AEQe: 7898

AEQ: 12625

PRUb: 10911

FST: 6221, 5964, 9929, 389, and 4992

FST: 7355, 6725, 115, 4992, 389

VULc: 1988, 4749 and 2343

HYP: 11456*, 6686*, 13724*, 9556* and 9515*

HYP: 2422*, 6686, 7932, 9556, 7458,

HYPd: 2925*, 6686*, 7458*, 1975*, 2506* and 956*

PRU: 11088, 10567, 1709, 10911 and 7293

PRU: 10567, 1709, 7293, 10911

VUL: 1988*, 2344, 14966, 4749, 1364

VUL: 1364*, 2344*, 4749*, 1988*

 

Days to flowering

FST: 7978*, 4890, 7352, 6340, 10616, 10402,

FST: 1899*, 8570, 7285, 1158, 5964

FST: 7978, 7285, 10402, 1158, 1899

3125, 115, 3219, 6570, 8514, 12498

HYP: 1975, 6143, 6515

HYP: 6515, 1975, 956, 9556, 6143

VUL: 1988, 4749, 2344

VUL: 14966, 4749

VUL: 14966*

Pod yield per plot

AEQ : 12625*

AEQ 12553*, 12625*, 7898*, 12719

AEQ: 12625*, 7898*

FST: 13284*, 2039*, 13513* and 1824*

FST: 10595*, 6148*, 6022*, 7013*, 7884*, 7905* and 4992*

FST: 11130*, 6148*, 7013*, 6022*, 7905*, 7884*, 4992*

HYP: 6686*

PRU: 10037*, 10567*, 1710*, 11088* and 10945*

HYP: 9515*, 1975, 9556, 956, 13539

PRU: 10036*, 10567*, 1710*, 1709*, 10915*, 10945*, 11088*

 

PRU: 10915*, 10567*, 1710*, 11088*, 10945*

Pods per plant

AEQ 12719, 12625

AEQ: 12719, 7898, 12625, 12553

AEQ: 7898, 12719, 12553, 12625

FST: 4087*, 1824*, 11130* and 8360*

FST: 11130, 10616, 2145, 7929, 5609

FST: 1899, 7929, 13049, 5609, 11130

HYP: 6686*, 11109, 3877, 4431, 5163, 1975

HYP: 3987, 7932, 13539, 9037

HYP: 9556, 13539, 9037

PRU: 10036, 1710, 7293, 1709, 10567

PRU: 10036, 10945, 10911, 10915, 11088

PRU: 10036, 10911, 11088, 10915, 10567

Yield per plant (g)

AEQ: 12719, 12625

AEQ: 12625*, 12553*, 7898*

AEQ: 12625*, 7898*, 12719, 12553

FST: 13513*, 1824*, 13049*

FST: 4992* and 6022*

FST: 6022*, 12963, 13049, 6340, 4992

HYP: 4331, 1975, 7932, 6686, 11109

HYP: 13539

HYP: 7932, 13539

PRU: 7293, 10567, 1710, 11088

PRU: 12112*, 1710*, 10915*, 10945*, 10911* and 11088*

PRU: 10911*, 10567*, 12112*, 10915*, 10945*, 1710*, 11088*

VUL: 2344, 14896

 

VUL: 2344

Shelling percentage

FST: 13829, 1796, 14696, 1824 and 2159

FST: 12498, 11203, 10549, 397 and 3510

FST: 6570, 12498, 13829, 14696, 11203

PRU: 1710

HYP: 1975

 
 

VUL: 10037

 

100-Seed weight

AEQ: 12625

AEQ: 12625, 12553, 7898

AEQ: 7898, 12625

FST: 8485*, 457, 6220, 1274, 1824

FST: 7013*, 14007*, 6022* and 6148*

FST: 8485*, 14007*, 6022*, 6148*

PRU: 1709, 11088, 12112, 1710

HYP: 8748

PRU: 12112*, 1710*, 10567, 10037, 11088

VUL: 14966

PRU: 12112* and 1710*

VUL: 14966

  

VUL: 14966, 1364

Oil contentf

AEQ: 12553, 12719, 12625

AEQ: 7898, 12625, 12553, 12719

AEQ: 12625

FST: 14007*, 13513*, 13430*

FST: 7777, 282, 10900, 12743, 12665

FST: 11203*, 6340*, 14007*, 13513*, 13430*

HYP: 10575*, 9695, 8833

HYP: 3987, 2925, 2506, 10575, 4250

HYP: 8833*, 9695*, 10575*, 9873, 6686, 11109

PRU: 1710*, 12112* and 10036*

PRU: 11088, 10945, 12112, 1710, 10036

PRU: 10036*

 

VUL: 4749, 1364

VUL: 1364

Protein contentf

FST: 1256, 7355, 398, 8485, 1386

FST: 8570, 13430, 1908, 2057, 445

AEQ: 12553

HYP: 1975*, 10105*, 9515, 4331, 8833

HYP: 4243, 8835, 956, 7932, 6515

FST: 1256*, 7355*, 398*, 8485*, 1384*

VUL: 1364

VUL: 1364, 14966, 4749, 1988

HYP: 9556*, 8835*, 9515*, 10105*, 4331*, 1975*

aFST = Fastigata, b PRU = Peruviana, c VUL = Vulgaris, d HYP = Hypogaea, e AEQ = Aequatoriana, f Analysis carried out at entry level only

* Accessions significantly better over their respective controls

Cluster composition and variation for morphological traits among clusters

PCAs based on the first nine principal components accounted for 79% of the total variation and resulted in four distinct clusters (Table 4). Cluster 1 comprised 23 accessions dominated by peruviana (47.8%) and fastigiata (30.4%) types. A majority of accessions in this cluster have erect growth habit, sequential branching, no stem pigmentation, leaflets almost glabrous on surfaces, peg pigmentation, pods with slight constriction and reticulation, and had 3-2-4-1/3-2-1-4/3-4-2-1 seeds per pod (more three-seeded than the other type of pods). Although there were five primary seed colors most of the accessions had tan-colored seeds. Of the 26 accessions included in cluster 2, 81% were hypogaea types, with most of the accessions having procumbent growth habit, alternate branching, no pigmentation on the stem (but pigmentation on pegs), subglabrous hairs in one or two rows along main axis, and green and glabrous leaflets. Most of the accessions have moderate pod beak and constriction, slight reticulation, and 2-1 seeds per pod (a high frequency of more two-seeded pods). The predominant seed color in this cluster was tan but the cluster included eight primary seed colors. In cluster 3, 54.3% of the accessions belonged to fastigiata and 34.3% to hypogaea. The cluster was characterized by erect growth with sequential branching, stem and peg pigmentation, subglabrous hairs on the main axis, light green glabrous leaflets, pods with slight beak, constriction and reticulation, and 3-2-4-1/3-2-1-4/3-4-2-1 seeds per pod. Red- and tan-colored seeds were predominant, although nine primary seed colors were recorded. Cluster 4 accessions were predominantly from fastigiata (95%), mostly with erect growth habit, sequential branching, stem and peg pigmentation, subglabrous hairs on the main axis, light-green glabrous leaflets, slight pod beak and constriction, and 3-2-4-1/3-2-1-4/3-4-2-1 seeds per pod. Red seed color was predominant, although eight primary seed colors were observed.
Table 4

Distribution of cold-tolerant peanut accessions and control cultivars in four clusters delineated by cluster analysis based on scores of nine principal components

Cluster

Botanical varieties

Accessions (ICG number)

1

aequatoriana

ICGs 7898, 12553, 12625, and 12719

fastigiata

ICGs 4992, 6022, 6148, 6340, 7013, 7884, and 14007

hypogaea

ICG 7932

peruviana

ICGs 1709, 1710, 7293, 10036, 10037, 10567, 10911, 10915, 10945, 11088, and 12112

2

fastigiata

ICGs 1683, 10075, 10554, and 11203

hypogaea

ICGs 956, 1975, 2422, 2506, 2777, 2925, 3877, 3987, 4331, 5163, 6143, 6361, 8748, 8833, 8835, 9037, 9556, 9695, 10105, 10575, and 11109

vulgaris

ICG 2344

3

fastigiata

ICGs 457, 1274, 1796, 1824, 2158, 2159, 3510, 4670, 4890, 5609, 5964, 6220, 6565, 8485, 9141, 9144, 9929, 10481, and 10595

hypogaea

M 13, ICGs 4243, 4250, 4738, 6686, 9515, 9873, 11456, 12360, 13539, and 13724, and ICGS 76

vulgaris

ICGs 1364, 4749, 14966 and ICGS 44

4

fastigiata

ICGs 115, 282, 318, 376, 389, 397, 398, 445, 1158, 1256, 1298, 1384, 1399, 1899, 1908, 2039, 2057, 2145, 3125, 3219, 3477, 3726, 3779, 4087, 4788, 5094, 5475, 6203, 6221, 6421, 6570, 6706, 6725, 6878, 6888, 7005, 7285, 7352, 7355, 7777, 7812, 7905, 7929, 7978, 8360, 8514, 8517, 8570, 10092, 10371, 10402, 10495, 10519, 10549, 10566, 10616, 10788, 10900, 11130, 11605, 12498, 12564, 12665, 12743, 12963, 13049, 13097, 13284, 13288, 13430, 13513, 13829, and 14696, and Gangapuri

hypogaea

5233, 6515, and 7458

vulgaris

1988

Variation for agronomic traits among clusters

In the rainy season the four clusters differed significantly for all traits except for pods per plant and pod width (Table 5). Cluster 2 and 4 accessions emerged faster and flowered earlier. Accessions in cluster 4 were taller, had large leaflets, and high seed protein content. Accessions in cluster 3 were shorter and had small leaflets, more primary branches, the highest seed yield, a high shelling percentage, and large seed size. Accessions in cluster 2 had the highest seed oil content. In the post-rainy season, differences were significant among four clusters for 17 traits. Cluster 1 and 4 accessions emerged faster and flowered earlier. Plants in cluster 1 accessions were taller, had larger leaflets, highest seed yield, large pod and seed size, and high seed oil content.
Table 5

Mean for agronomic traits in different clusters of cold-tolerant peanut germplasm accessions in the 2001 rainy and 2001–2002 post-rainy seasons at ICRISAT Center, Patancheru, India

Trait

Cluster 1

Cluster 2

Cluster 3

Cluster 4

Rainy season

Time to emergence (days)

8.0b

8.0b

8.4a

8.4a

Time to 50% flowering (days)

21.1b

19.8c

25.4a

19.9c

Primary branch (no.)

4.6b

4.4b

5.3a

4.4b

Plant height (cm)

28.6a

28.8a

18.7b

30.6a

Leaflet length (mm)

54.2a

53.5a

44.7b

55.2a

Leaflet width (mm)

23.0a

22.9a

21.5b

23.2a

Pods per plant (no.)

10.1a

10.7a

10.3a

10.7a

Pod length (mm)

33.3a

33.0a

31.0b

33.5a

Pod width (mm)

12.8a

12.8a

12.5a

12.8a

Seed length (mm)

14.2ba

13.9b

14.7a

14.0ba

Seed width (mm)

7.7b

7.6b

7.9a

7.6b

Pod yield per plant (g)

7.8a

7.9a

7.1b

7.8a

Pod yield per plot (kg)

529.2b

517.2b

617.9a

492.8b

Shelling (%)

58.1b

59.8ba

61.1a

59.0b

100-seed weight (g)

32.6b

32.1b

35.0a

32.3b

Oil content (%)

47.7ba

48.3a

47.1bc

46.5c

Protein content (%)

25.3b

23.7c

25.5b

27.4a

Post-rainy season

Time to emergence (days)

12.0c

12.8a

12.4b

12.1c

Time to 50% flowering (days)

48.3b

50.0a

48.0b

47.6b

Primary branch (no.)

4.5b

4.7a

4.6b

4.5b

Plant height (cm)

22.1a

13.0d

16.5c

18.1b

Leaflet length (mm)

57.5a

41.9c

46.0b

47.4b

Leaflet width (mm)

24.3a

19.8c

20.7b

21.2b

Pods per plant (no.)

16.2b

17.3a

16.0b

15.0c

Pod length (mm)

40.2a

33.3b

34.6b

35.2b

Pod width (mm)

14.3a

13.6b

13.8b

13.8b

Seed length (mm)

14.5a

13.7b

13.5b

12.7c

Seed width (mm)

8.3a

8.0b

8.3a

8.2a

Pod yield per plant (g)

22.3a

17.8b

17.5b

15.4c

Pod yield per plot (kg)

2562.7a

1745.4b

1688.4b

1360.2c

Shelling (%)

65.8b

66.1b

68.0a

68.4a

100-seed weight (g)

53.9a

44.3c

48.0b

46.7cb

Oil content (%)

49.6a

48.9ba

47.8ba

47.4c

Protein content (%)

23.6b

23.2b

24.6ba

25.3a

Differences between means of different clusters were tested using the Newman–Keuls test

Means followed by the same letter are not significantly different at P = 0.05

Heterogeneity of variances for various traits

Variance for 9 agronomic traits in the 2001 rainy and 8 traits in the 2001/2002 post-rainy seasons were heterogeneous (Table 6). In the rainy season, cluster 1 accessions had higher variances for plant height and leaflet length and cluster 3 accessions for pod yield per plot, 100-seed weight, and seed protein content. Higher variances for accessions in cluster 1 for pod length, in cluster 2 for pod yield and 100-seed weight, and in cluster 3 for pods per plant occurred in the post-rainy season.
Table 6

Traits with heterogeneous variances in four clusters for various agronomic traits in cold-tolerant peanut germplasm accessions, 2001-rainy and 2001–2002 post-rainy seasons, at ICRISAT, Patancheru, India

Trait

Entire

Cluster 1

Cluster 2

Cluster 3

Cluster 4

F value

P a

Rainy season

Time to 50% emergence (days)

0.2

0.2

0.1

0.2

0.1

4.48

0.0048

Primary branch (no.)

0.2

0.2

0.1

0.2

0.1

3.99

0.0089

Plant height (cm)

34.5

27.4

14.5

11.4

8.7

3.93

0.0098

Leaflet length (mm)

28.9

26.3

7.5

7.7

10.8

4.65

0.0038

Leaflet width (mm)

1.2

1.3

0.5

0.2

0.9

4.74

0.0034

Pods per plant (no.)

2.2

1.6

1

3.1

2.4

2.75

0.0449

Pod yield per plot(kg)

22725.9

23830.5

11155.8

43158

13063.4

4.55

0.0043

100-seed weight (g)

17.3

16.3

11.6

37.9

8.3

10.25

<.0001

Protein content (%)

5.6

2.6

5.7

6.8

2

5.37

0.0015

Post-rainy season

Pods per plant (no.)

4.1

4.3

4

5.4

2.1

3.37

0.0200

Pod length (mm)

18.9

39.9

24.1

9.4

7.4

7.39

0.0001

Seed length (mm)

1.8

2.2

3.1

1.6

0.5

8.87

<.0001

Seed width (mm)

0.1

0.1

0.1

0.1

0.1

2.96

0.0341

Pod yield per plant (g)

14.1

10.6

15.2

15

3.9

4.98

0.0025

Pod yield per plot (kg)

390860.7

334815.9

401850.4

392666.8

80495.8

5.54

0.0012

Shelling (%)

6.8

5.5

14.5

5.7

3

7.56

<.0001

100-seed weight (g)

37.1

61

66.3

26

10.7

6.63

0.0003

Variances were tested using Levene’s test

aP = probability at 0.5

Phenotypic diversity index among clusters

The clusters differed in terms of the biological status (whether landraces, breeding lines or cultivars) of the accessions involved in minimum and maximum phenotypic diversity indices (Table 7). Accessions with the least difference in phenotypic diversity index in the entire set were ICG 13288 (a landrace from Brazil) and ICG 10519 (an advanced cultivar from Australia). The accessions with the minimum diversity index in each cluster were two landraces from Peru (ICG 10945 and ICG 11088) in cluster 1, breeding lines (ICG 2506 and ICG 2925) from India in cluster 2, a landrace (ICG 6220) from Brazil and an advanced cultivar (ICG 9144) from Syria in cluster 3, and an accession with unknown origin (ICG 1298) and Indian cultivar Gangapuri (ICG 2738) in cluster 4.
Table 7

Phenotypic diversity in the cold-tolerant peanut germplasm accession in the entire set and in different clusters

Entire set

Phenotypic diversity

Mean phenotypic diversity index

0.188

Minimum phenotypic diversity index between ICG10519 and ICG 13288

0.062

Maximum phenotypic diversity index between ICG 12112 and ICG 156

0.408

Cluster 1

Mean phenotypic diversity index

0.277

Minimum phenotypic diversity index between ICG 10945 and ICG 11088

0.145

Maximum phenotypic diversity index between ICG 12112 and ICG 7932

0.437

Cluster 2

Mean phenotypic diversity index

0.261

Minimum phenotypic diversity index between ICG 2506 and ICG 2925

0.138

Maximum phenotypic diversity index between ICG 10075 and ICG 9037

0.517

Cluster 3

Mean phenotypic diversity index

0.255

Minimum phenotypic diversity index between ICG 6220 and ICG 9144

0.112

Maximum phenotypic diversity index between ICG 10595 and ICG 13942

0.450

Cluster 4

Mean phenotypic diversity index

0.209

Minimum phenotypic diversity index ICG 1298 and ICG 2738

0.101

Maximum phenotypic diversity index between ICG 1908 and ICG 7352

0.410

The maximum phenotypic diversity index in the entire set was between ICG 12112 (landrace from Peru) and ICG 156 (cultivar from India) while accessions with maximum diversity in individual clusters were ICG 12112 (landrace from Peru) and ICG 7932 (advance line from South Africa) in cluster 1, ICG 10075 (landrace from Peru) and ICG 9037 (landrace from Côte d’Ivoire) in cluster 2, ICG 10595 (landrace from Brazil) and ICG 13942 (cultivar from India) in cluster 3, and ICG 1908 (breeding line from India) and ICG 7352 (land race from Peru) in cluster 4.

Botanical varieties and cold tolerance

Differences for chilling injury among botanical types of peanut have been reported. Sellschop and Salmon (1928) found Valencia and Spanish types highly sensitive while Virginia bunch type had exceptional hardiness. Bell et al. (1991) reported a positive association between rate of emergence and mean daily temperature (17.8–23.2°C) in 16 peanut cultivars, indicating that air temperatures were always lower than those required for good germination. They however reported no significant differences (P < 0.05) in coefficients of temperature sensitivity either between cultivars of the same botanical type or between different botanical types. All cultivars used in their study had similar base temperature (T b) values for emergence (13.2°C). However, we found differences between accessions (irrespective of botanical type) in terms of their cold tolerance at emergence under lower temperatures (12°C) under laboratory conditions (Upadhyaya et al. 2001), indicating that cold-tolerant accessions identified in this study captured greater diversity for base-temperature tolerance at germination.

The cold-tolerant accessions reported in this study had substantial diversity for most agronomic traits and thus should be good sources to use in breeding programs for developing peanut cultivar that germinate at lower temperatures. It will also be interesting to study the reaction of these cold-tolerant accessions at various growth stages at which peanut is vulnerable to cold injury. Some of the identified accessions have good agronomic potential, and hence their use in breeding programs will not adversely affect exploitation of additive genetic variance in a self-pollinated crop such as peanut.

Notes

Open Access

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Copyright information

© The Author(s) 2008

Authors and Affiliations

  • H. D. Upadhyaya
    • 1
  • L. J. Reddy
    • 1
  • S. L. Dwivedi
    • 1
  • C. L. L. Gowda
    • 1
  • S. Singh
    • 1
  1. 1.International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)PatancheruIndia

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