52

ASSOCIATION STUDIES FOR MORPHOLOGICAL AND PHYSIOLOGICAL

TRAITS IN COWPEA (VIGNA UNGUICULATA (L.)WALP.)

M. H. Surpura and S. C. Sharma

ABSTRACTPhenotypic and genotypic correlation coefficients and path coefficient analysis were carried out using 25 genotypes of cowpea. Associationstudies revealed that number of pods per plant followed by biological yield per plant, harvest index, number of branches per plant, plantheight, seeds per pod, pod length and 100-seed weight exhibited positive and significantly high correlation with grain yield and can be usedas selection criteria in improving grain yield in cowpea. Days to 50% flowering and days to maturity were also negative and significantlycorrelated with grain yield. In path analysis it is revealed that the traits having high direct effect in favourable direction and positivesignificant correlation at genotypic level with grain yield can be considered as direct yield contributing characters. Therefore, it may beconcluded that characters harvest index, biological yield per plant, number of branches per plant, seeds per pod and number of pods perplant can be exploited in future cowpea breeding programmes.

Key words: cowpea, (Vigna unguiculata (L.)Walp.), Correlation, path coefficient analysis, association

M.Sc. Student, Assistant Research Scientist (PBG), Department of Genetics & Plant Breeding, Department of Seed Technology,

C.P. College of Agriculture, S.D. Agricultural University, Sardarkrushinagar - 385 506, Gujarat, India

INTRODUCTIONCowpea (Vigna unguiculata (L.) Walp.) is one of the most

important pulse crops. There hardly needs any emphasis onnutritional quality of cowpea that can simply be regarded as"Nutritional Tablet" on account of its high amount of protein(23.4%) of better biological values and carbohydrates (60.3%)besides containing important minerals (Ca, P and Fe) and vitamins(Vitamin-A, thiamine, riboflavin, niacin, folic acid and ascorbicacid). Cowpea is also suitable as good intercrop under bothintensive and limited resources growing conditions inclusivedrought or rainfed conditions and can also be squeezed inbetween two major crops. Knowledge of the interrelationshipbetween the different morphological and yield contributing traitsis necessary for drawing out sound breeding programmes for anycrop. Seed yield, being a complex quantitative traits, is governedby a large number of genes and is greatly influenced byenvironmental fluctuations, therefore, selection of elite genotypesbased on yield as such is not effective. Under suchcircumstances, a breeder has to find out some other characterswhich contribute to yield. Therefore, knowledge of associationof characters with seed yield and among themselves and theirdirect and indirect effects upon the yield is very helpful andprovides an effective measure in crop improvement programmeof cowpea.

MATERIAL AND METHODSThe experimental material consisted of 25 diverse genotypes

of cowpea (Vigna unguiculata (L.) Walp.) was grown in arandomized block design with three replications in Summer, 2012at Centre of Excellence for Research on Pulses, SardarkrushinagarDantiwada Agricultural University, Sardarkrushinagar, Gujarat.Each genotype was accommodated in 3 rows plot of 4 m length.The row to row spacing of 45 cm and plant to plant spacing of10 cm was adopted. The observation recorded for 16 different

traits viz., days to 50% flowering, days to maturity, plant height,number of branches per plant, number of pods per plant, podlength, seeds per pod, 100-seed weight, biological yield per plant,grain yield per plant, harvest index, relative water content, leafarea per plant, chlorophyll content, seedling vigour index andgermination stress index on five randomly selected plants fromeach plot. Phenotypic and genotypic correlation coefficients wereworked out using the method suggested by AL-Jibouri et al.(1958). The path coefficient analysis was done according toDewey and Lu (1959).

RESULTS AND DISCUSSIONCorrelation studies:In the present study, highest positive and significant

correlation with grain yield per plant was observed in number ofpods per plant followed by biological yield per plant, harvestindex, number of branches per plant, plant height, seeds per pod,pod length and 100-seed weight at both genotypic andphenotypic levels (Table 1). However, character days to maturityand days to 50% flowering showed negative and significantassociation at both genotypic and phenotypic levels with grainyield per plant revealing importance of early maturity in cowpea.Similar positive associations for one or other aforesaidcomponent characters with grain yield per plant in cowpea werealso reported by Kumari et al. (2010).

Variable results were obtained with regard to mutualassociation between component traits. However, most of thecharacters having positive association with grain yield per plantwere positively correlated with among themselves in present study(Table 1). Number of pods per plant showed higher positivesignificant association with grain yield was also exhibited positivesignificant correlation with biological yield per plant, harvestindex, number of branches per plant, plant height, pod length,seeds per pod and 100-seed weight. Similar correlations were also

The Allahabad Farmer, Vol. LXXIII, No. 4, October - December, 2017

Received 02-05-2017Accepted 24-10-2017

53

matched with the findings of Kumari et al. (2010) for plant heightand Bhardu and Navale (2011) for number of branches per plantin cowpea. Biological yield per plant which was an importantcomponent of yield per plant also exhibited significant andpositive correlation with leaf area per plant number of pods perplant, harvest index, plant height, number of branches per plant,100-seed weight and pod length. Harvest index also showedpositive and significant association with number of pods perplant, biological yield per plant, seeds per pod, number ofbranches per plant, pod length and plant height. Number ofbranches per plant exhibited positive and significant associationwith number of pods per plant, biological yield per plant, harvestindex, plant height and100-seed weight. Similar results were alsoconfirmed by Kumari et al. (2010) and Bhardu and Navale (2011).Plant height exhibited positive and significant association withbiological yield per plant, number of pods per plant, 100-seedweight, harvest index and number of branches per plant.

Seeds per pod was found to be positively and significantlycorrelated with harvest index, pod length and number of podsper plant. Pod length exhibited positive and significantassociation with seeds per pod, grain yield per plant, harvestindex, biological yield per plant, number of pods per plant and100-seed weight. Similar results were confirmed by Suganthi andMurugan (2008) for seeds per pod in cowpea. 100-seed weightwhich was also positive and significantly correlated with grainyield showed positive and significant association with plantheight, biological yield per plant, number of pods per plant,number of branches per plant and pod length. Similar results wereconfirmed by Singh and Verma (2002) for pod length and plantheight in cowpea. Days to maturity and days to 50% floweringshowed negative and significant correlation with grain yield andalso exhibited positive and significant mutual association. Thisshowed the importance of early maturity in cowpea as alsoobserved by Kumari et al. (2010).

In the light of the above results, it may be concluded thatnumber of pods per plant, biological yield per plant, harvest indexand number of branches per plant exhibited positive correlationof considerable magnitude with grain yield per plant and can beused as selection criteria in improving grain yield in cowpea.Mutual correlation among these traits suggests that simultaneousselection for these traits will have a better efficiency for improvingthe grain yield

PATH COEFFICIENT ANALYSIS:Path coefficient analysis has been useful in partioning direct

and indirect causes of correlation and allows a detailedexamination of specific forces acting to produce a givencorrelation. Simultaneously, it also measures the relativeimportance of each causal factor, thereby provides a realistic basisfor allocation of weightage to attributes in deciding a suitablecriterion for genetic improvement. Hence, path coefficientanalysed at genotypic level for grain yield. Residual effects werenegligible which indicates that variability of grain yield per plantwas completely governed by the characters included in theanalysis (Table 2). In present study, characters viz., number ofpods per plant, biological yield per plant, harvest index, numberof branches per plant, plant height, seeds per pod, pod lengthand 100-seed weight exhibited significant correlation with grainyield per plant.

Highest direct effect on grain yield in favourable direction wasexhibited by followed harvest index (0.547) by biological yield perplant (0.411), number of branches per plant (0.137), seeds per pod(0.109), 100-seed weight (0.096), days to maturity (0.095) and plantheight (0.032). Whereas, contribution of number of pods per plant(-0.193) and pod length (-0.243) were in unfavourable direction.On other hand for days to 50% flowering the direct effect (-0.121)was negative but in favourable direction with grain yield. Harvestindex also showed high positive significant correlation with grainyield mainly due to its positive direct effect on grain yield.However, it was also supported by indirect effects throughbiological yield per plant, number of branches per plant, seedsper pod, days to 50% flowering, 100-seed weight and plant height.The results were also confirmed the findings of Sawant (1994)and Nigude et al. (2004) in cowpea. Biological yield per plantshowed considerable significant positive correlation with grainyield and its direct effect was also positive. The indirect effectsof biological yield on grain yield was through other contributingcharacters viz., harvest index, days to 50% flowering, number ofbranches per plant, 100-seed weight, seeds per pod and plantheight were also considerable. There results were also confirmedthe findings of Kumawat and Raje (2005) and Baghizadeh et al.(2010) in cowpea.

Number of branches per plant had positive significantcorrelation with grain yield mainly due to its direct effect on grainyield. The positive association was also contributed by indirecteffects through biological yield per plant, harvest index, days to50% flowering, 100-seed weight and seeds per pod. Similar resultswere also supported by Baghizadeh et al. (2010) and Bharduand Navale (2011) in cowpea. Seeds per pod also exhibitedpositive significant correlation with grain yield and its direct effectwas also positive. The positive association was mainly due toits direct effects and indirect effects through harvest index,biological yield per plant, days to 50% flowering, number ofbranches per plant and100-seed weight on grain yield per plant.These findings were also supported by Udensi et al. (2012) incowpea.

100-seed weight had positive significant association with grainyield and its direct effect was also positive but in low magnitude.The positive association was mainly due to indirect effects viabiological yield per plant, harvest index, number of branches perplant, days to 50% flowering, plant height and seeds per pod.The correlation between days to maturity and grain yield per plantwas negative but significant, though its direct effect was positivebut low in magnitude. The negative association was mainly dueto indirect effect of this character on seed yield via biologicalyield per plant, harvest index, days to 50% flowering, number ofbranches per plant, pod length, 100-seed weight, plant height andseeds per pod. The results were also confirmed the findings ofKumawat and Raje (2005) in cowpea. Plant height exhibitedpositive and significant correlation with grain yield per plant andtheir direct effects on grain yield were also positive but havinglow magnitude. The positive association was mainly due toindirect effects via biological yield per plant, harvest index, daysto 50% flowering, number of pods per plant and 100-seed weight.Days to 50% flowering exhibited negative significant correlationwith grain yield mainly due to its negative direct effect. Theindirect effect of this character on seed yield via biological yieldper plant, harvest index, number of branches per plant, pod length,

M. H. Surpura and S. C. Sharma

54

Tabl

e 1:

Gen

otyp

ic a

nd p

heno

typi

c co

rrel

atio

n co

effic

ient

s for

diff

eren

t cha

ract

ers i

n co

wpe

a

Cha

ract

ers

Day

sPl

ant

No.

ofN

o. of

Pod

Seed

s10

0-se

edB

iolo

gica

lH

arve

stR

elat

ive

Leaf

are

aC

hlor

ophy

llSe

edlin

gG

erm

inat

ion

Gra

into

heig

htbr

anch

esPo

dsle

ngth

per

wei

ght

yield

per

inde

xw

ater

per p

lant

cont

ent

vigo

urst

ress

yiel

dm

atur

ity (c

m)

per p

lant

per p

lant

(cm

)po

d(g

)pl

ant (

g)(%

)co

nten

t(c

m2 )

inde

xin

dex

per p

lant

(%)

(g

)

Day

s to

50%

flow

erin

grg

0.92

0**

-0.5

20**

-0.5

65**

-0.5

53**

0.140

-0.1

36-0

.273

*-0

.686

**-0

.345

**-0

.362

**-0

.442

**-0

.329

**-0

.368

**-0

.547

**-0

.522

**rp

0.89

1**

-0.4

26**

-0.4

05**

-0.4

36**

0.142

-0.0

90-0

.179

-0.5

36**

-0.2

58*

-0.3

16**

-0.4

58**

-0.1

81-0

.313

**-0

.440

**-0

.409

**D

ays

to m

atur

ityrg

-0.4

47**

-0.6

15**

-0.4

80**

0.191

-0.0

06-0

.338

**-0

.579

**-0

.311

**-0

.262

*-0

.343

**-0

.153

-0.2

24-0

.440

**-0

.439

**rp

-0.3

16**

-0.4

44**

-0.3

37**

0.183

-0.0

14-0

.221

-0.4

22**

-0.2

52*

-0.2

05-0

.364

**-0

.029

-0.2

22-0

.303

**-0

.330

**Pl

ant h

eight

(cm

)rg

0.31

5**

0.51

9**

0.050

-0.1

580.

401*

*0.

602*

*0.

333*

*0.

458*

*0.

544*

*0.2

080.2

170.

415*

*0.

508*

*rp

0.27

6*0.

427*

*0.0

47-0

.041

0.38

7**

0.47

5**

0.25

7*0.

374*

*0.

439*

*0.1

910.2

230.

378*

*0.

402*

*N

umbe

r of b

ranc

hes p

er p

lant

rg0.

593*

*0.1

800.1

240.

273*

0.53

5**

0.39

7**

0.47

3**

0.46

3**

-0.1

090.

517*

*0.

570*

*0.

570*

*rp

0.48

2**

0.166

0.151

0.25

4*0.

425*

*0.

351*

*0.

331*

*0.

387*

*-0

.046

0.43

4**

0.42

6**

0.48

9**

Num

ber o

f pod

s pe

r plan

trg

0.34

5**

0.34

4**

0.28

4*0.

954*

*0.

923*

*0.

963*

*0.

979*

*0.

278*

0.81

8**

0.98

0**

0.99

4**

rp0.

296*

*0.

301*

*0.

235*

0.83

2**

0.70

2**

0.81

9**

0.84

6**

0.187

0.60

2**

0.84

4**

0.86

7**

Pod

lengt

h (c

m)

rg0.

419*

*0.

270*

0.35

4**

0.36

8**

0.44

9**

0.45

1**

0.32

4**

0.26

3*0.1

950.

397*

*rp

0.31

8**

0.25

8*0.

316*

*0.

307*

*0.

378*

*0.

382*

*0.

280*

0.192

0.178

0.35

7**

Seed

s pe

r pod

rg0.0

350.

316*

*0.

447*

*0.

348*

*0.

292*

*0.1

380.

361*

*0.

418*

*0.

428*

*rp

-0.0

070.2

140.

302*

*0.2

230.

275*

0.143

0.30

2**

0.34

9**

0.29

0*10

0-se

ed w

eight

rg0.

388*

*0.1

560.

288*

0.35

0**

0.091

-0.0

770.1

680.

311*

*rp

0.33

3**

0.178

0.193

0.24

9*0.1

11-0

.069

0.154

0.30

8**

Biol

ogica

l yiel

d pe

r plan

trg

0.72

4**

0.89

6**

0.99

8**

0.42

6**

0.64

2**

0.89

3**

0.90

7**

rp0.

598*

*0.

799*

*0.

847*

*0.

359*

*0.

492*

*0.

755*

*0.

866*

*H

arve

st in

dex

(%)

rg0.

795*

*0.

924*

*0.0

910.

771*

*0.

898*

*0.

854*

*rp

0.61

4**

0.67

4**

0.085

0.58

9**

0.71

5**

0.82

1**

Relat

ive

wate

r con

tent (

%)

rg0.

920*

*0.

438*

*0.

668*

*0.

873*

*0.

989*

*rp

0.78

1**

0.26

5*0.

590*

*0.

790*

*0.

827*

*Le

af a

rea

per p

lant (

cm2 )

rg0.

387*

*0.

691*

*0.

918*

*0.

985*

*rp

0.26

9*0.

572*

*0.

753*

*0.

790*

*Ch

loro

phyl

l con

tent

rg0.0

540.2

080.

337*

*rp

0.054

0.147

0.29

4**

Seed

ling v

igou

r ind

exrg

0.86

3**

0.77

6**

rp0.

720*

*0.

599*

*G

erm

inati

on st

ress

inde

xrg

0.97

6**

rp0.

808*

*

*, *

* Si

gnifi

cant

at 0

.05

and

0.01

leve

ls, re

spec

tivel

y.

The Allahabad Farmer, Vol. LXXIII, No. 4, October - December, 2017

55

Tabl

e 2:

Pat

h co

effic

ient

ana

lysi

s sho

win

g di

rect

and

indi

rect

effe

cts o

f diff

eren

t cha

ract

ers o

n gr

ain

yiel

d in

cow

pea

Cha

ract

ers

Day

s to

Day

sPl

ant

No.

of

No.

of

Pod

Seed

s10

0-se

edB

iolo

gica

lH

arve

stR

elat

ive

Lea

fC

hlor

ophy

llSe

edli

ngG

erm

inat

ion

Gen

otyp

ic50

%to

heig

htbr

anch

espo

dsle

ngth

per

wei

ght

yiel

d pe

rin

dex

wat

erar

eaco

nten

tvi

gour

stre

ssco

rrel

atio

nfl

ower

ing

mat

urit

y(c

m)

per

per

(cm

)po

d(g

)pl

ant

(g)

(%)

cont

ent

per

inde

xin

dex

with

gra

inpl

ant

plan

t(%

)pl

ant

yiel

d pe

r(c

m2 )

plan

t (g

)

Day

s to

50%

-0.1

210.

087

-0.0

17-0

.077

0.10

7-0

.034

-0.0

15-0

.026

-0.2

82-0

.189

-0.3

310.

111

-0.0

09-0

.125

0.39

9-0

.522

**flo

wer

ing

Day

s to

-0.1

120.

095

-0.0

14-0

.084

0.09

3-0

.047

-0.0

01-0

.032

-0.2

38-0

.170

-0.2

400.

086

-0.0

04-0

.076

0.30

5-0

.439

**m

atur

ity

Plan

t hei

ght

0.06

3-0

.042

0.03

20.

043

-0.1

00-0

.012

-0.0

170.

038

0.24

70.

182

0.42

0-0

.137

0.00

50.

074

-0.2

880.

508*

*(c

m)

No.

of

bran

ches

0.06

9-0

.058

0.01

00.

137

-0.1

15-0

.044

0.01

40.

026

0.22

00.

217

0.43

3-0

.116

-0.0

030.

175

-0.3

960.

570*

*pe

r pl

ant

No.

of

pods

0.06

7-0

.045

0.01

70.

081

-0.1

93-0

.084

0.03

80.

027

0.39

20.

505

0.88

2-0

.246

0.00

70.

226

-0.6

800.

994*

*pe

r pl

ant

Pod

leng

th (c

m)

-0.0

170.

018

0.00

20.

025

-0.0

67-0

.243

0.04

60.

026

0.14

60.

201

0.41

2-0

.113

0.00

90.

089

-0.1

350.

397*

*

Seed

s pe

r po

d0.

017

-0.0

01-0

.005

0.01

7-0

.066

-0.1

020.

109

0.00

30.

130

0.24

50.

319

-0.0

730.

004

0.12

2-0

.290

0.42

8**

100-

seed

0.03

3-0

.032

0.01

30.

037

-0.0

55-0

.066

0.00

40.

096

0.15

90.

085

0.26

4-0

.088

0.00

2-0

.026

-0.1

170.

311*

*w

eigh

t (g)

Bio

logi

cal

0.08

3-0

.055

0.01

90.

073

-0.1

84-0

.086

0.03

50.

037

0.41

10.

396

0.82

0-0

.252

0.01

10.

218

-0.6

200.

907*

*yi

eld

per

plan

t (g

)

Har

vest

0.04

2-0

.029

0.01

10.

054

-0.1

78-0

.089

0.04

90.

015

0.29

80.

547

0.72

8-0

.232

0.00

20.

261

-0.6

230.

854*

*in

dex

(%)

Rel

ativ

e w

ater

0.04

4-0

.025

0.01

50.

065

-0.1

86-0

.109

0.03

80.

028

0.36

80.

435

0.91

6-0

.231

0.01

10.

226

-0.6

060.

989*

*co

nten

t (%

)

Leaf

are

a pe

r0.

054

-0.0

330.

018

0.06

3-0

.189

-0.1

090.

032

0.03

30.

413

0.50

50.

843

-0.2

510.

010

0.23

4-0

.637

0.98

5**

plan

t (c

m2 )

Chl

orop

hyll

0.04

0-0

.015

0.00

7-0

.015

-0.0

54-0

.079

0.01

50.

009

0.17

50.

050

0.40

1-0

.097

0.02

60.

018

-0.1

440.

337*

*co

nten

t

Seed

ling

vigo

ur0.

045

-0.0

210.

007

0.07

1-0

.158

-0.0

640.

039

-0.0

070.

264

0.42

20.

612

-0.1

740.

001

0.33

9-0

.599

0.77

6**

inde

x

Ger

min

atio

n0.

070

-0.0

420.

013

0.07

8-0

.189

-0.0

470.

046

0.01

60.

367

0.49

10.

799

-0.2

310.

005

0.29

3-0

.694

0.97

6**

stre

ss in

dex

Res

idua

l eff

ect:

Gen

otyp

ic:

0.01

254

and

Phen

otyp

ic:

0.06

291

M. H. Surpura and S. C. Sharma

56

100-seed weight, plant height and seeds per pod were alsoappreciable. Similar results were also supported by Udensi et al.(2012) in cowpea.

On the other case, number of pods per plant showed highestpositive significant correlation with grain yield but its direct effectwas negative. Although the magnitude of direct effect on grainyield was very low in magnitude. The positive association wasmainly due to its indirect effect through harvest index, biologicalyield per plant, number of branches per plant, days to 50%flowering, seeds per pod, 100-seed weight and plant height. Podlength exhibited positive significant correlation with grain yieldalthough its direct effect was negative. The positive associationwas mainly due to indirect effects via harvest index, biologicalyield per plant, seeds per pod, 100-seed weight, number ofbranches per plant, days to maturity and plant height on grainyield. Similar finding were also reported by Bhardu and Navale(2011) in cowpea.

On considering the findings of correlation coefficients and pathanalysis it is revealed that the traits having high positivesignificant correlation at genotypic level with grain yield anddirect effect in favourable direction can be considered as directyield contributing characters. Further, with the support of abovefindings it may be suggested that cowpea ideotype should haveearly type with high harvest index, biological yield per plant,number of pods per plant, number of branches per plant, seedsper pod and 100-seed weight. Hence, it would be rewarding tolay more stress on these components of yield in selectionprogrammes for improvement of grain yield and drought tolerancein cowpea.

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The Allahabad Farmer, Vol. LXXIII, No. 4, October - December, 2017