Genetic Diversity for Agronomic Traits in Interspecific Crosses of Brassica

Maryam M, Farhatullah M, Iqbal A, Noor M, Khan FU, Farid A, Adnan M and Sohail A

Published on: 2019-11-05

Abstract

Search for genetic diversity is of crucial importance in prevailing climatic changes. The present study was therefore carried out to estimate genetic diversity for agronomic and morphological traits in interspecific crosses of brassica during the cropping season 2016-17. The genetic material of this study comprised 36 F7 brassica populations along with eight parental lines were planted in RCB design with two replications. F7 populations manifested significant variation for morphological traits. Population Bnr-23 had maximum 100-seed weight (0.71 g) whereas, population Bnr-36 was higher in seed yield plant-1 (15.8 g). Among F7 populations, moderate to high heritability was recorded for flowering, primary branches, plant height, silique length and seeds silique-1. Low to high heritability was estimated for main raceme length, siliques main raceme, maturity and seed yield, whereas high heritability was recorded for 100 seed weight. The results indicate further evaluation of these advanced lines before there release and commercial utilization.

Keywords

Genetic Diversity; Agronomic; Brassica; F7 Population; Parental Lines

Introduction

Brassica is one among the major sources of vegetable oil globally. Worldwide, oilseed brassica species are the 3rd most important comestible source of vegetable oil whereas palm and soybean remained first and second in the list respectively [1]. In Pakistan, it is the 2nd prime important vegetable oil source after cottonseed. Worldwide production of brassica is about 64.8 million tons. In Pakistan, total production is about 194 thousand tons annually whereas in Khyber Pakhtunkhwa total brassica production is only five thousand tons. Total share of Khyber Pakhtunkhwa was 2.58 thousand tons on average during the year 2015-16 (BSPD, 2017). Rapeseed (B. napus L.) is widely adapted to varied climatic conditions [2]. The genus Brassica contains many species, but six of these are widely cultivated. Out of six, three diploid species i.e. Brassica nigra (BB genome, 2n = 16), B. rapa (AA genome, 2n=20) and B. oleracea(CC genome, 2n=18) has been hybridized, developing three amphidiploid species i.e. B. juncea (genome AABB, 2n = 36), B. napus (genome, AACC, 2n = 38) and B. carinata (genome, BBCC, 2n = 34) [3]. Brassica rapa (rapes mustards, turnip), B. juncea (Brown mustard), B. oleraceae (cauliflower, cabbage, Brussels sprouts, broccoli) and B. nigra (black mustard) are the most useful cultivated species which are used as vegetables, herbs and spices (Dreyer and Jordan, 2000). Majority plant parts of oilseed species like stalk, sprouts, flowers, leaves and roots are comestible. Seed extracted oil is also used as flavour enhancing ingredient in food items. Some brassica species are also utilized as forage. Brassica genotypes cultivated in India and Pakistan, Brassica juncea and B. napus are mainly self-pollinated crops, however, it has been noticed that the rate of cross pollination in B. juncea and B.napus is about 8-18% and 20-30%, respectively [4,5]. This characterization of B. napus and B. juncea elevate the interspecific crosses among both species of brassica and help the breeders to develop new genetic alliance and more variability, a phenomenon called as introgression [6]. Introgressive hybridization is basically the gene flux from one specie to another. However, in several wide crosses of plants, partial hybrids with female-parent-type phenotypes and exact chromosome number but altered genomic composition have also been reported [7]. Estimation of genetic variability [8] and heritability [9] for several morphological attributes serve as an efficient tool. Commonly observed these parameters are influenced by environment due to the involvement of multiple gene inheritance in their expression. Heritability measures the relative effect of genes and environment that signifies the magnitude of the variation through which a trait would be transmitted into the next generations. Hence, conduct of the succeeding generations may be predicted and selection procedure may be ratified [10]. Genetic progression intimates the absolute relation between heritability and selection response. The expected selection response is also known as genetic advance. Based on the above mentioned facts the present study was conducted to:

  1. i) Determine genetic variability in F7 intro grassed populations based on different morphological traits.
  2. ii) Estimate the heritability and genetic advance for various morphological traits in F7 introgressed populations.

iii) Identify best populations for further breeding programs

Material and Methods

Field layout

During the cropping season of 2016-17 this research was carried out at Malakandher Research Farm, The University of Agriculture Peshawar. Since F7 generation was proceeded therefore 36 F6:7 populations seeds were sown in the field along with their parental lines to raise F7 populations (Table 1). Plant material was sown on 17th October 2016 using randomized complete block design in two replicates. Row length was 5m with 60 cm distance between them while plants were 30 cm apart to facilitate optimum plant growth.

Data were recorded on days to flowering, days to maturity, plant height, primary branches per plant, silique per main-raceme, silique length, seeds per silique, 100-seed weight and seed yield per plant.

Table 1: List of eight parental lines and 36 introgressed F6:7 brassica populations

                Parental lines

 

Bn-547

B. napus

 

Bn-531

B. napus

Bn-510

B. napus

Bn-525

B. napus

Bn-532

B. napus

Br-118

B. rapa

Bn-533

B. napus

Bj-109

B. juncea

F7 Populations

 

 

 

 

 

 

 

 

Bn-547×Bj-109

Genotypes

Selection based

 

 

 

 

 

Bn-533×Bj-109

Genotypes

Selection based

Bnj4

High OA

Bnj 42

High OA

Bnj 5

High OA, High LA

Bnj 48

High LA

Bnj 7

High OA

Bnj 49

High oil

Bnj 8

High OA, High LA

Bnj 51

High protein

Bnj 10

Low EA, High LA

Bnj 56

High OA

Bnj 12

High OA

 

Bn-531×Br-118

Bnr2

Low GSL

Bnj 13

High OA

Bnr4

High OA

Bnj 14

High OA

 

 

Bn-525×Br-118

Bnr6

Low EA

Bnj 16

High OA, High LA

Bnr7

Low EA

Bnj 18

Low GSL, High LA

Bnr12

High OA

Bnj 22

Low GSL

 

Bn-532×Br-118

Bnr15

High OA

Bn-510×Bj-109

Bnj 27

High oil

Bnr16

High OA

 

 

 

 

Bn-532×Bj-109

Bnj 32

High oil

 

Bn-533×Br-118

Bnr20

Low GSL

Bnj 36

High oil

Bnr22

High OA, Low EA

Bnj 38

High oil

Bnr23

Low EA

Bnj 39

High protein

 

 

Bn-547×Br-118

Bnr28

High OA

Bnj 40

High protein

Bnr32

High LA

Bnj 41

High oil

Bnr36

High LA

Estimation of Relative electrolyte leakage rate (RLR)

Electrolyte leakage was used to assess membrane permeability. Electrolyte leakage was measured through spectrophotometery method [18]. Leaf samples were washed with deionized water and cut into 1cm segments. Leaf samples were then placed in 50 ml falcon tube containing 20 ml of deionized water. The samples were incubated at room temperature (25ºC) on a shaker (100 rpm) for 24 h. Initial, electrical conductivity (EC) of the bathing solution (EC initial) was measured at 280 nm after incubation. After that, the samples were frozen at -20°C for 12 h to break the cell to induce maximum leakage. Now, samples were cooled down at room temperature and the final absorbance (EC final) was taken at 280 nm after thawing.

The EC (%) was calculated by using formula: (A280 initial/A280 final) ×100

Statistical analysis

Data recorded on biochemical and quantitative traits for each population were subjected to analysis of variance following Steel and Torrie (1980). Means were separated at 5% probability level. Heritability estimation provides knowledge about the inheritance of variance for a particular trait in a population. Estimation of broad sense heritability particularly for a trait was calculated through parental lines and their F7 populations variances obtained from each cross combination. It is followed by Mahmud and Kramer formula (1951).

Where     

h2 (BS) = Broad sense heritability

VF7= Variance of F7 population

VP1 & VP2 = Variance of Parent 1 and Parent 2

The assessment of segregating generations for the scope of possible selection is called Genetic advance. Allard in 1964 suggested the following formula which was used to estimate the genetic advance throughout the research.

GA = i h2 √σ2P

Where i=selection intensity

  √σ2P = Phenotypic standard deviation,

          h2 = heritability.

TTable 2: Mean squares for flowering, primary branches, plant height, main raceme length, silique main raceme-1of parental lines and their F7 populations. -1of parental lines and their

F7 populations.

SOV

df

Days to flowering

Primary branches plant-1

Plant height

Main raceme length

Silique main raceme-1

Replications

1

4.9

0.02

866.9

10.23

21.4

Genotypes

43

416.2**

  155.69**

25174.0**

11763.2**

27840.7**

Parents (P)

7

56.9*

  36.34**

3360.9**

651.96**

2272.70**

    F7 Population (F7)

35

337.5**

  117.01**

20827.1**

11080.7**

22895.8**

P vs. F7

1

21.8**

2.35*

986.1**

30.56*

2672.28**

Error

43

132.1

24.22

2730.3

327.93

1239.7

C.V%

 

1.64

9.45

3.97

3.4

7.24

 

Table 3: Mean squares for silique length, seed silique-1, maturity, 100-seed weight and seed yield plant-1of parental lines and their F7 populations.

F7 populations.

SOV

df

Silique length

Seed silique-1

Days to maturity

100-Seed weight

Seed yield plant-1

Replications

1

1.15

12.24

0.5

0.001

27.78

Genotypes

43

79.70**

738.41**

227.13**

1.43**

536.75**

Parents (P)

7

13.99*

114.16*

93.20**

0.13**

95.85*

F7 Population (F7)

35

52.46*

543.23**

128.57**

0.61**

397.46**

P vs. F7

1

13.25**

81.02**

5.37*

0.69**

43.44**

Error

43

34.83

308.14

58.81

0.26

211.72

C.V%

 

12.87

14.34

0.67

16.99

23.69

Table 4: Mean values for flowering, primary branches, plant height, main raceme length and silique main raceme-1 of parental lines and their F7 populations.

and their F7 populations.

Parental lines

Silique length(cm)

Seed silique-1

Days to maturity

100-seed weight(g)

Seed yield plant-1 (g)

Bn-547

108.5

10.6

211

80

63.8

Bj-109

104.3

6.5

192.2

89.7

44.4

Bn-510

107

8.7

184.6

77.1

65.3

Bn-532

106.1

6.1

179

74.9

74.1

Bn-533

104

8.1

203.9

88.3

54.7

Bn-531

109

10.1

200.5

80.8

85.4

Bn-525

103.7

7.3

209.5

68.7

56.3

Br-118

106.3

8.9

168

80.5

56.1

Parental Means

106.1

8.2

193.6

80

62.51

F7 Populations

       

Bnj4

107.3

11.6

199.6

71.9

73.1

Bnj5

107.3

6.6

185.4

103.7

85.4

Bnj7

109.3

7.1

213.4

66.2

89.5

Bnj8

108.9

7.8

183.1

104.3

114.6

Bnj10

108.2

8.5

185.6

91.6

111.3

Bnj12

105.3

7.7

208

72.7

106.5

Bnj13

110.4

9.1

222.3

84.8

71.1

Bnj14

109.9

10

187.1

80.7

66.9

Bnj16

109.6

6.5

167

67.2

84.2

Bnj18

113.5

10.2

210.7

76.1

78.9

Bnj22

107.6

7

168.6

75

99.5

Bnj27

106.9

10.6

182.8

78.5

110

Bnj32

106

6.4

209.3

65.2

73.9

Bnj36

106.1

8.5

234

83.9

84

Bnj38

104.9

8.1

212.8

98.7

90.4

Bnj39

110.6

6.8

191.5

90

78.4

Bnj40

107

7.5

185

76.2

62.2

Bnj41

106.6

7.3

180.5

78.2

49.3

Bnj42

106.7

6.1

185.5

90.6

87.8

Bnj48

104.7

8.5

190.8

58.4

53

Bnj49

105.1

7.9

214.7

89.2

80.1

Bnj51

106.4

9.3

210.7

86.6

59.2

Bnj56

104.8

8.8

192.4

87.3

54.1

Bnr2

104.9

8.1

212.7

56.3

48.9

Bnr4

107.9

7.9

230.7

84.1

62

Bnr6

113

6.7

223.9

68.7

71.7

Bnr7

108.8

8.4

197.2

77.7

85

Bnr12

107.5

7

216.3

103.5

70

Bnr15

106.7

6.9

224.7

89.6

72.7

Bnr16

105.5

7.1

200.3

87.1

70.3

Bnr20

107.4

7.3

214

90.4

78.6

Bnr22

108.5

8.5

220.8

61.6

100.4

Bnr23

106.5

7.4

210.2

84.5

56.9

Bnr28

106.6

6.5

188.3

89.4

57.4

Bnr32

105.7

6.4

207

69.1

51.9

Bnr36

104.4

7

216.6

96

75.6

Means of F7 Populations

107.4

7.864

202.3

81.5

76.8

Genotypes Means

107.2

7.94

200.7

81.3

74.2

LSD (0.05) Parents

4.14

1.77

18.84

6.53

12.7

LSD (0.05) F7 populations

3.56

1.52

16.18

5.61

10.9

Table 5: Means values for silique length, seeds silique-1, maturity, 100-seed weight and seed yield plant-1of parental lines and their F7 populations..

Parental lines

Silique length(cm)

Seed silique-1

Days to maturity

100-seed weight(g)

Seed yield plant-1 (g)

Bn-547

5.32

18.5

175.1

0.45

7.53

Bj-109

6.5

13.5

174.2

0.16

7.86

Bn-510

7.5

16.2

174.5

0.22

9.58

Bn-532

7.27

18.5

173.5

0.35

6.38

Bn-533

4.84

17.2

172.8

0.32

5.61

Bn-531

5.61

14.4

171.6

0.21

5.64

Bn-525

6.9

21.5

171.6

0.21

13.5

Br-118

5.42

13.3

167

0.25

6.92

      Parental Means

6.17

16.64

172.5

0.27

7.88

      F7 Populations

       

Bnj4

6.35

17.2

171.4

0.51

10

Bnj5

7.11

20

170.5

0.39

10.3

Bnj7

6.78

22.1

172

0.37

13.2

Bnj8

7.11

19.7

172.2

0.34

8.02

Bnj10

7.53

18.2

170.9

0.48

10.3

Bnj12

10.45

16.6

170.6

0.55

12.1

Bnj13

8.76

13.7

172.6

0.34

10.4

Bnj14

7.57

15.9

170.2

0.56

9.58

Bnj16

7.62

15.8

172.4

0.3

8.02

Bnj18

6.81

15.3

172.4

0.52

9.46

Bnj22

6.37

17.1

171

0.42

11.2

Bnj27

6.07

17.2

171.9

0.36

9.7

Bnj32

6.78

17.4

172.9

0.58

10.2

Bnj36

6.61

21.5

171.7

0.49

8.29

Bnj38

7.29

18.9

174.2

0.4

7.85

Bnj39

6.86

18.8

171.9

0.58

9

Bnj40

6.44

16.9

174.8

0.56

5.98

Bnj41

7.57

17.3

173

0.55

7.46

Bnj42

7.01

22

171.2

0.51

7.1

Bnj48

7.52

21.6

170.6

0.56

4.24

Bnj49

8.08

23.9

171.1

0.51

7.17

Bnj51

7.07

21

175

0.54

11.5

Bnj56

7.14

23.1

172.2

0.55

8.98

Bnr2

7.26

23.7

171.4

0.57

12.6

Bnr4

8.1

23.3

171.2

0.51

11.6

Bnr6

7.16

22.2

170

0.6

14.1

Bnr7

7.32

22

171.4

0.41

6.8

Bnr12

5.82

21

167.9

0.51

9.23

Bnr15

8.5

20.1

172.5

0.59

12.7

Bnr16

6.89

16.7

173.5

0.52

10.8

Bnr20

6.27

16.5

171.4

0.46

9.48

Bnr22

6.14

17.3

173.1

0.56

7.43

Bnr23

6.31

15.9

172

0.71

7.85

Bnr28

7.2

21.5

172.2

0.67

9.27

Bnr32

7.54

21

172.7

0.52

10.9

Bnr36

6.9

16.2

172.4

0.43

15.8

Means of F7 Populations

7.18

19.13

171.9

0.5

9.7

     Genotypes Means

6.99

18.67

172

0.46

9.37

      LSD (0.05) Parents

2.13

6.33

2.77

0.18

5.25

LSD (0.05) F7 populations

1.83

5.43

2.37

0.16

4.5

Results And Discussion

Analyses of variance

Data recorded on various morphological traits were subjected to analysis of variance. This analysis revealed significant as well as non-significant differences among all the traits. Each trait is being discussed in detail as under.

Days to flowering

Analysis of variance revealed significant (P≤0.01) differences among parental lines versus F7populations interaction, F7 populations while parental lines were significant (P≤0.05) for days to 50% flowering (Table 2). Early flowering among parental lines was recorded inBn-525(103.7 days) while late flowering was observed inBn-531(109 days). Among F7 populations, Bnr-36 was early in flowering (104 days) while Bnr-6 was late in flowering (113 days) (Table 4). Overall, parental populations were earlier in flowering (103.7days). Our findings are supported by the results of [11] and [12]. They reported significant differences (P≤0.01) while studying genetic variability, heritability and genetic advance for days to flowering in ten Brassica accessions. Estimation of broad sense heritability for days to flowering ranged between 0.49 and 0.66 in F7 populations. PopulationBnr-2 had high heritability (0.66) while Bnj-7 had the lowest recorded heritability (0.49). The range of expected genetic advance in F7 populations having 20% selection intensity was from 1.91 to 2.91. Maximum expected genetic advance (2.91) was recorded by Bnj-49, followed by population Bnr-16, Bnr-2 and Bnj-38 with the average value of 2.90, 2.85 and 2.69, respectively, while lowest (1.91) was recorded for Bnj-7 (Table 6). [13]. while studying genetic variability declared high genetic advance (3.6) for days to flowering in Brassica rapa.

TTable 6: Heritability and genetic advance for flowering, primary branches plant-1, plant height, main raceme length and silique main raceme-1 of F7 population.

Genotypes

Days to flowering

Primary branches

Plant height

Main raceme length

Silique main raceme-1

F7 populations

h2(BS)

G.A

h2(BS)

G.A

h2(BS)

F7 populations

h2(BS)

G.A

h2(BS)

G.A

Bnj4

0.57

2.41

0.47

0.91

0.81

6.98

0.45

5.06

0.91

10.22

Bnj5

0.58

2.42

0.57

1.26

0.98

19

0.28

2.65

0.86

7.76

Bnj7

0.497

1.91

0.37

0.75

0.94

13.2

0.74

15.2

0.84

7.18

Bnj8

0.61

2.66

0.4

0.74

0.98

20

0.15

1.36

0.84

7.12

Bnj10

0.52

2.08

0.71

1.94

0.98

19.3

0.38

3.61

0.75

5.38

Bnj12

0.55

2.29

0.49

1

0.94

11.5

0.75

12.4

0.69

4.05

Bnj13

0.56

2.34

0.42

0.79

0.9

14.2

0.56

7.04

0.74

7.67

Bnj14

0.54

2.17

0.65

1.55

0.97

15.9

0.75

10.9

0.9

9.15

Bnj16

0.52

2.07

0.35

0.68

0.99

30.5

0.82

15.8

0.88

8.39

Bnj18

0.59

2.54

0.76

2.17

0.57

6.72

0.75

11.5

0.73

5.57

Bnj22

0.55

2.26

0.5

0.98

0.99

30.2

0.72

12

0.48

3.19

Bnj27

0.64

2.72

0.59

1.29

0.97

20.3

0.63

9.4

0.63

5.88

Bnj32

0.6

2.68

0.56

1

0.73

7.59

0.58

12

0.55

5.96

Bnj36

0.6

2.61

0.32

0.47

0.9

21.2

0.7

9.63

0.57

5.87

Bnj38

0.61

2.69

0.67

1.36

0.9

8.01

0.49

4.97

0.61

7.95

Bnj39

0.57

2.44

0.78

2.77

0.88

14.1

0.45

4.48

0.5

4.39

Bnj40

0.51

2.02

0.57

1.11

0.93

17.5

0.7

11.8

0.57

5.36

Bnj41

0.56

2.35

0.36

0.51

0.57

18.9

0.74

11.2

0.36

2.88

Bnj42

0.52

2.1

0.55

1.09

0.92

16.1

0.45

4.66

0.49

6.16

Bnj48

0.53

2.25

0.36

0.8

0.59

10.4

0.62

16.7

0.53

4.74

Bnj49

0.64

2.91

0.65

2.35

0.67

8.46

0.47

6.51

0.56

5.83

Bnj51

0.58

2.4

0.6

1.98

0.8

8.33

0.54

6.35

0.48

4.15

Bnj56

0.56

2.26

0.69

4

0.72

11.6

0.52

5.88

0.63

6.28

Bnr2

0.66

2.85

0.81

2.61

0.8

10.6

0.52

17.3

0.31

3.53

Bnr4

0.62

2.53

0.61

1.07

0.89

18.2

0.39

5.25

0.26

2.36

Bnr6

0.53

2.13

0.54

1.03

0.64

13.7

0.5

10.8

0.22

2.42

Bnr7

0.58

2.42

0.7

1.63

0.85

13.1

0.45

6.73

0.03

0.84

Bnr12

0.57

2.37

0.81

2.01

0.4

6.89

0.32

5.07

0.09

0.94

Bnr15

0.6

2.61

0.77

1.56

0.8

14.1

0.11

0.98

0.31

3.89

Bnr16

0.63

2.91

0.58

1.31

0.86

12.4

0.6

9.3

0.29

3.93

Bnr20

0.61

2.67

0.64

1.43

0.86

12.8

0.25

3.03

0.5

6.26

Bnr22

0.59

2.51

0.79

2.24

0.85

13.6

0.6

14.4

0.51

6.73

Bnr23

0.6

2.55

0.62

1.42

0.72

7.38

0.38

4.81

0.38

4.35

Bnr28

0.56

2.31

0.64

1.24

0.96

17.4

0.25

2.51

0.7

7.1

Bnr32

0.51

2.02

0.74

1.8

0.95

13.6

0.59

13

0.71

7.11

Bnr36

0.5

1.97

0.5

1

0.93

12.1

0.55

7.42

0.78

8.89

 

Primary branches plant-1: For primary branches analysis of variance manifested significant differences (P≤0.01) between parental lines and F7 populations while parental lines versus F7 populations interaction were significant (P≤0.05)(Table 2). Comparison between F7and parental lines, F7 populations had more number of primary branches plant-1 (11.6) than parental lines (10.6) (Table 5). Among parental lines, most primary branches (10.6) were observed in Bn-547 while, minimum (6.1) were recorded for line Bn-532. Similarly, in F7 populations, maximum primary branches (11.6) were recorded for population Bnj-4 while minimum primary branches (6.3) for population Bnj-42, followed by population Bnj-27 and Bnj-18 with the mean value of 10.6 and 10.2, respectively (Table 4). These results supports the research of [14] and [15]. Significant differences were recorded (P≤0.01) for primary branches plant-1 in B. rapa and B. carinata, respectively. In F7 population heritability ranged from 0.32 to 0.81. Population Bnr-12had highest heritability with the mean value of 0.81. The lowest heritability was recorded for population Bnj-36 with mean value of 0.32 (Table 6). High genetic advance (46.7) was estimated for populationBnj-36 while lowest (4.0) for populationBnj-56 (Table 8). Related to the recent research, [16] reported low to high heritability (<20->50) along with genetic advance in interspecific crosses of B. carinata, B. napus, B. campestris, and B. juncea.

Plant height

Mean squares for plant height were significantly different (P≤0.01) among all the parental lines, F7 populations and parental lines versus F7populationsinteraction (Table 2). Overall, F7 populations had tallest plants (234 cm) as compared to their parental lines (211cm). Among parental lines, tallest plants were observed in Bn-547(211 cm) while shortest plants were observed in Br-118 (168 cm). In F7 populations, tallest plants were recorded in population Bnj-36(234 cm) followed by the population Bnr-4 and Bnr-15 with mean values of 230 cm and 224 cm respectively, while shortest plants (167 cm) in population Bnj-16 (Table 4). These results showed similarity towards [17] and findings [18]. They reported the similar results for plant height with significant (P≤0.01) variation in Brassica rapa advanced lines. Estimation of heritability for plant height ranged between0.40 and0.99 in F7 populations. Highest heritability (0.99) and genetic advance (30.5) was estimated for populationBnj-16while populationBnr-12 had minimum heritability (0.40) with lowest genetic advance (6.89) (Table 6). [19] Also revealed high heritability (0.82) for plant height with high genetic advance (49.2) in B. napus.

Main raceme length

Analysis of variance revealed significant differences (P≤0.01) between parental lines and F7 populations while parental lines versus F7 populations interaction was significant (P≤0.05) for main raceme length. Among parental lines, longest main raceme (89.7 cm) was recorded forBj-109while shortest (68.7 cm) for Bn-525. In F7 populations, longest main raceme (104.3 cm)was recorded for populationBnj-8 while shortest (56.3 cm) for population Bnr-2 followed by population Bnr-12, Bnj-5 and Bnj-38 with the mean values of 103.5 cm, 103.7 cm and 98.7cm respectively(Table 4). Among F7 populations, heritability ranged between 0.10 and 0.82. Maximum heritability (0.82) was recorded for population Bnj-16 and minimum (0.10) for population Bnr-15 (Table 8). High genetic advance (17.3) was estimated for population Bnr-2 while lowest (0.97) for population Bnr-15 (Table 6). Results of current study matches with the results of [20]. He recorded high heritability (0.76) in advanced Brassica (Brassica napus L.) generations.

E Silique main raceme-1: Significant variation (P≤0.01) was recorded for F7 populations, parental lines and parental lines versus F7populationsinteraction (Table 2). Overall, F7 populations exhibited maximum silique (114.6) than their parental lines (85.4). Among parental lines, maximum silique on main raceme (85.4) was observed for population Bn-531 while minimum (44) for population Bj-109. Among F7 populations, maximum siliques (114.6) on main raceme were recorded in population Bnj-8 whereas, minimum(48.9) were recorded for population Bnr-2 followed by the population Bnj-10, Bnj-22 and Bnj-12 having respective mean values of 111.3, 110 and 106.5 (Table 4). Estimation of Heritability ranged between 0.03 and 0.91 in F7 brassica populations. Population Bnr-7 had high heritability (0.91) with high genetic advance (10.2), whereas minimum heritability (0.03) and genetic advance (0.84) was observed for population Bnr-4 (Table 6). Results of minimum estimates of genetic advance (0.11) for silique main raceme-1 were also in line with [21] who worked on interspecific brassica crosses.

Silique length

Analysis of variance revealed highly significant variation (P≤0.01) for parental lines versus F7populationsinteraction while parental lines and F7 populations were significant (P≤0.05) for silique length (Table 3). Overall, F7 populations revealed longer silique than their parental populations. Among parental lines longest (7.5 cm) silique was recorded for Bn-510while shortest (4.8 cm) for Bn-533. In F7 populations, longest silique(10.45 cm) was recorded for populationBnj-12 while shortest(5.8 cm) for population Bnr-12 followed by population Bnj-13 and Bnj-4 having respective mean value of 8.76 and 8.10 cm(Table 5). Heritability estimates for silique length ranged between0.42 and 0.90. Maximum heritability (0.90) was observed for population Bnj-90 while minimum (0.42) for population Bnj-10. Among F7 populations, genetic advance ranged from 4.25 to 0.70. Population Bnj-6 had highest (4.25) genetic advance while population Bnj-22 had lowest (0.70) (Table 7). [15] Also reported high heritability (0.89) coupled with high genetic advance (16.4) in Brassica juncea L. for number of silique length.

Seeds silique-1: Significant (P≤0.01) variability is revealed through analysis of variance among F7populations and parental lines versus F7populationsinteractionwhile parental lines were significant (P≤0.05) for seeds silique-1(Table 3). Overall F7 populations withhold maximum seeds silique-1 than the parental lines. Population Bn-525 among parental lines exhibited maximum seeds silique-1 (21.5) whereas minimum (13.3) for Br-118. Similarly, among F7 populations maximum seeds silique-1(23.9) was recorded for population Bnj-49 while minimum (13.7) for Bnj-13 (Table 5). Uzair et al (2016) experimented on Brassica juncea and reported significant variation for seeds silique-1. Estimation of broad sense heritability ranged between0.44 and 0.98. Population Bnj-22 possessed highest heritability (0.98) and genetic advance (8.56) while lowest heritability (0.44) for population Bnr-16. Lowest genetic advance (1.20) was exhibited by population Bnr-20 (Table 7). [22] Also observed maximum heritability (0.92) with high genetic advance (23.2) for seeds silique-1 in Brassica juncea.
Days to maturity

High significant (P≤0.01) differences were revealed through analysis of variance for F7 populations and parental lines whereas parental lines versus F7populations interaction was recorded significant (P≤0.05) for days to maturity (Table 3). In parental lines, Br-118matured earlier (167 days) while Bn-547was late maturing (175 days). In F7 populations, early maturity (167 days) was recorded for Bnr-12 while Bnj-5 was late maturing (175 days) (Table 5). For days to maturity, estimation of broad sense heritability in F7 populations ranged between 0.17 and 0.79. High heritability (0.79) with highest genetic advance (3.39) was observed for Bnr-32followed by population Bnr-6 and Bnr-4 with average mean values of 0.73 and 0.71 respectively, while population Bnj-13 showed minimum heritability (0.17) and genetic advance (0.49) (Table 7). [23] Experimented on rapeseed (Brassica napus L.). He also reported low heritability (0.12) as well as genetic advance (4.6) for days to maturity correlation with seed yield.
100-seed weight
Significant variation (P≤0.01) were found for 100 seed weight among parental lines, F7 populations and parental lines versus F7populationsinteraction (Table 3). Overall, F7 populations had maximum seed weight (1.71 g) as compare to their parental lines (0.45 g). Parent Bn-547 exhibited maximum seed weight (0.45 g) while lowest (0.16g) for Bj-109. Among F7 populations, population Bnr-23 was observed with highest seed weight (0.71 g), while populationBnj-16had lowest seed weight (0.30 g) (Table 5). [24] Also reported highly significant variation in four intraspecific and interspecific Brassica crosses for 100-seed weight. Heritability estimation ranged between0.55 and 0.98, while genetic advance ranged from 0.03upto 0.18. PopulationBnj-7 had high heritability (0.98) with highest genetic advance (0.18) while population Bnj-39 exhibited low heritability (0.55) with lowest genetic advance (0.03) (Table 7). [14] While studying genetic variability and heritability in indigenous Brassica rapa L. accessions, recorded high heritability (0.85) for this trait,

Seed yield plant-1 : For seed yield plant-1analysis of variance revealed highly significant (P≤0.01) variation among F7 populations, parental lines while parental lines versus F7populationsinteraction were significant (P≤0.05) (Table 3). Overall, F7 populations exhibited higher seed yieldplant-1 (15.8) than their parental lines(13.5). Population Bn-525 was high yielding (13.5 g) among parental lines whereas populationBn-533was recorded low in yield(5.61 g). Among F7 populations, population Bnr-36 withhold maximum yield plant-1 (15.81 g) while minimum (4.24 g) for population Bnj-48 (Table 5). Populations Bnj-12 had the highest broad sense heritability (0.97) while population Bnj-39had lowest heritability (0.10). Maximum genetic advance (8.25) was observed for population Bnr-36 while lowest genetic advance (0.69) for population Bnj-40 (Table 7). [15] Also obtained high heritability (0.73) and genetic advance (18.1) in Indian mustard.

 

Conclusions

The studied F7 crosses revealed greater diversity for various desirable traits and thus the information may be used in further evaluation of the available germplasm for proper exploitation in future breeding programs. The population Bnr-36 in the cross Bn-547×Br-118, population Bnj-8 and Bnj-14 in the cross Bn-547×Bj-109, population Bnr-23 and Bnr-22 in the cross Bn-533×Br-118, population Bnr-36 in the cross Bn-547×Bj-118 and population Bnr-23 in the cross Bn-533×Bj-118 could be forward to next generations for developing varieties with maximum yield with early flowering plants, [25- longest main raceme with maximum number of siliques and maximum 100 seed weight.

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