Theoretical and Applied Genetics 47, 179-187 (1976) 9 by S p r i n g e r - V e r l a g 1976

Adaptive Responses and Genetic Divergence in a World Germplasm Collection of Chick Pea (Cicer arietinum L.) R.K.J.

Narayan

and A.J.

Macefield,

Department

of Agricultural

Botany,

U.C.W.,

Aberystwyth

(U.K).

Summary. A world germplasm collection of 5477 lines of chick pea were evaluated for eight characters related to fitness and yield at two locations in India. Multivariate analyses as Mahalanobis D e statistic, canonical analysis, and factor analysis were used for the classification of this material and to assess the genetic divergence between them. On D 2 analysis and grouping the whole collection fell into six clusters with substantial genetic divergence between }-hem. Despite the overall parallelism between genetic diversity and geographical distance stringent natural and human selection or geographical barriers preventing gene flow were found to have played a significant role in the genetic divergence of this material. Plant type was reflected as the most important character operating in the genetic divergence between geographical groups, followed by seed colour and flower colour. Significant negative correlations were found between I00 seed weight and number of seeds per pod and seed colour. Further independent classification using canonical analysis confirmed the results obtained from the D 2 analysis. Factor analysis was used to resolve the intercorrelations between the eight variables into fewer-meaningful factors which could explain the major forces in intraspecific differentiation. The loadings in the first factor reflected the importance of characters related to the reproductive capacity of the individual. Inclusion of flowering time and seed maturity time in the second factor which has an equal contribution suggests the importance of these characters in the competitive ability of the plant under natural and human selection.

In the present

Introduction

arietin~

Chick pea (Citer jor cultivated

L. ) being one of the five ma-

pulse crops

cal distribution.

has an extensive

No attempt

study the genetic

has

divergence

fective quantitative

geographi-

so far been

in this crop

made

through

to an ef-

approach,

and very

little is known

about the role of quantitative

characters

for subspeci-

fic differentiation. complex

Adaptation

response

in plant populations

affected by several

vidual and population

functions.

interacting

small

number

analysis

of genes

provides

natural used

1958;

causative

operating and human

influencing Majumdar

1960 andMurty

factors

or to a

for anal-

and their interrela-

It has been

populations

their genetic

and Rao

1958;

indi-

Multivariate

on and within plant populations selection.

to classify biological

factors

1970).

a useful statistical method

ysing the various tionships

(Bennett

Nair

and

and

under

successfully

divergence

related to fitness and yield was

used

characters

to assess

ture of genetic

divergence

in aworldgermplasm

tion of chickpea

using D 2 statistic of Mahalanobis

canonical

analysis

and factor analysis.

presented

in this communication.

Materials

and Methods

the nacollec( 1936 ),

The results

are

is a

It is unlikely that adap-

tive traits could be attributed to a single gene

study a set of quantitative

to identify (Anderson Mukherjee

et al., 1965).

The evaluation of the Chick pea germplasm was done at the Indian Agricultural Research Institute, New Delhi, India, during 1966-70.

The material comprised of 5477 varieties of chick pea from seventeen countries. The complete collection was grown at two locations in India in augmented randomised block designs with the major cultivars as controls. Eight plant characters were selected for the present analysis. The mean value for each character from the two locations was used for the analysis. The characters were scored as follows: I. Plant type: Spreading- 1, Semi-spreading-2, Erect-3. 2. Flower colour : White- 1, Pink-2, Violet-3. 3. Days to flower: Number of days from the date of sowing till 50 ~ of the plants in a line had flowered. (Each line had not less than 30 plants of a variety. ) 4. Days to seed maturity: Number of days from the date of sowing till the seeds have matured in 50 ~ of the plants in a line. 5. Pod size: Small-l, Medium-2, Large-3. 6. Number of seeds per pod: The average of 50pods selected at random from a line. 7. Weight of 100 seeds: Recorded in grams. 8. Seed colour : Pink or light pink- I, light-Brown-2, Brown-3, Yellow-4, Light green or green-5, Black-6.

180

R. K. J. Narayan

and A. J. Macefield:

Genetic Divergence

The total collection was grouped into 11 populations i as shown in Table 1. Countries contributing fewer than three varieties were grouped with geographically adjacent countries.

Table

1. Geographical

Population 1 2 3 4 5 6 7 8 9 10 II

origin

populations

2. Means

of Chick

No. of varieties

Origin unknown Afghanistan Algeria, Morocco Burma, India Iran, Iraq, Israel Mexico Nigeria, Sierra Leone, Tanganyka Pakistan United Arab Republic United States of America U.S.S.R.

Table

Germplasm

Collection of Chick Pea

From the residual matrix, four successive vectors and roots were calculated (see Rao 1952, 1964, Arunachalain 1967). Group constellations of the 11 populations were diagrammatically represented in the ~ - ha chart.

origin of the eleven

Geographical

in a World

for the eight characters

pea

included

27 6 29 1579 3761 12 6 34 8 8 7

of Chick colour

pea

Plant type

Flower

Days

to flower

Days

to maturity

Xl

Y1

x2

Y2

x3

Y3

x4

Y4

1.952 1.833 1 597 2 018 1 572 2 025 1 575 2 044 2.400 1.912 2.129

4.776 4.486 3.907 4.939 3.848 4.955 3.854 5.002 5.873 4.680 5.209

1.956 1.667 1.552 1.974 1.585 2.025 1.500 1.912 1.650 1.613 2.000

2.746 2.217 2.144 2.736 2.232 2.840 2.040 2.585 1.769 2.469 2.712

106.533 102.833 108.947 100.599 111.319 104.225 103.650 107.268 103.850 107.500 104.014

10.320 9.879 10.276 9.847 10.477 10.172 9.804 10.404 10.173 10.346 10.186

180.570 177.250 176.515 178.844 181.173 177.283 181.700 176.664 178.675 179.050 175.229

15.502 15.187 15.031 15.405 15.420 15.251 15.509 15.167 15.394 15.341 15.088

Population

1 2 3 4 5 6 7 8 9 10 11

Statistical Analysis A random sample of I00 varieties representing the 11 populations was chosen for variance analysis to ascertain whether significant differences existed for the means of the eight characters studied. D 2 Analysis The calculation of the D 2 values involved the following steps. (a) The uncorrelated linear combinations (y' s ) were obtained by pivotal condensation of the common dispersion matrix, of the correlated variables (x' s) (Rao 1952). (b) The mean values for the eight characters for different populations were transformed into the mean values of a set of uncorrelated linear combinations (Y's). (c) The D 2 between the ith and the jth populations for k characters was calculated as follows 2 . . . . 2 2 D I l = t~1(Ylt__ - YJt) . The D for k characters are calculated

separately

and added

up to give D e ij.

(d) The D-squares for each character for eachcombination were ranked in the descending order of magnitude and the rank totals were obtained for each character for all combinations (see Murty and Arunachalam 1967). The clustering of populations was by the method suggested by Rao (1952). After clustering, the intra and intercluster relationships were studied and the distances represented diagramatically using D values. Canonical

Canonical analysis in most cases permits the representation of the populations in a two dimensional chart depending on the proportion of variation accounted for by the first two roots. The between product sum matrix (A-matrix) is computed using the mean values of the uncorrelated linear combinations for all the characters for all the varieties. From the fourth power of the Amatrix, canonical vector 1 is retrievedby repeated iterations on a trial vector. After standardising the first canonical vector the first canonical root is extracted. Factor

i The word population is used here in a wider sense. It means a group of varieties arbitrarily pooled on the basis of geographical origin, see Table 1.

Analysis

Analysis

Among the several methods of factor analysis available the centroid method is popular and relatively simple. The centroid method outlined by Holzinger and Harman

R. K. J. Narayan

and A. J. Macefield:

Genetic

Divergence

in a World

(1941) was used in this analysis. The model assumes t h a t a s e t of p c o r r e l a t e d v a r i a b l e s a n d t h e i r i n t e r - c o r relations could be adequately described by k factors (k < p) which are linear and additive (Maxwell, 1961). The e x t r a c t i o n of f a c t o r s i n v o l v e d s u c c e s s i v e i t e r a t i o n s . T h e m a g n i t u d e of t h e c o e f f i c i e n t s of e a c h c h a r a c t e r ( f a c t o r l o a d i n g s ) a r e u s e d to u n d e r s t a n d t h e r e l a t i v e i m p o r t a n c e of t h o s e c h a r a c t e r s i n e a c h f a c t o r . In t h e c e n t r o i d m e t h o d , t h e e s t i m a t i o n of t h e f a c t o r l o a d i n g s is done through the quantities known as communalities. Cattel (1965) has defined communality as the portion of a v a r i a n c e of a v a r i a t e w h i c h i s d u e to k c o m m o n f a c t o r s . T h e e s t i m a t e s of c o m m u n a l i t i e s a r e o b t a i n e d b y an iterative procedure, starting with a trial vector (see A r u n a c h a l a m 1967 ; M u r t y e t a l . 1 9 7 0 ) . D2 , canonical and factor analyses were programmed on an IBM computer for the present analysis.

Germplasm

tively. Variance

studied.

1. D 2 A n a l y s i s

T h e c o e f f i c i e n t s of t h e u n c o r r e l a t e d

Pod size

are given in Tables

matrix 2 and

ations formed tra cluster

for the

six clusters

group,

100 s e e d . w e i g h t

Seed colour

x5

Y5

x6

Y6

x7

Y7

x8

Y8

2.378 2.333 2.372 2.149 2.296 2.400 2.375 2.091 2.075 2.225 2.314

5.506 5.276 5.472 4.898 5.303 5.574 5.328 4.842 4.504 5.121 5.352

1.300 1.233 1.358 1.498 1.417 1.613 1.276 1.448 1.225 1.463 '1.429

-0.866 -0.811 -0.325 -0.260 -0.322 0.245 -0.591 -0.538 -1.280 -0.343 -0.422

18.533 16.117 18.495 14.845 18.128 17.763 26.475 17.455 13.800 13.988 16.571

-1.224 -1.759 -1.195 -1.388 -1.312 -0.667 -0.932 -1.077 -2.376 -1.903 -1.206

3.080 1.833 2.895 2.979 2.839 3.063 2.500 2.750 3.250 2.688 4.289

2.318 1.511 2.748 1.621 2.535 1.930 2.813 1.555 2.177 1.572 3.077

Plant type xl xl x2 x3 x4 x5 x6 x7 x8

0.167

covariance

(Fig. 1). The inter and in-

average D 2 values are given in Table 5 o inter cluster

clusters

divergence

was observed

III a n d IV (D = 2 . 9 1 ) .

IV a n d V w e r e n e a r e r

3 respec-

N o . of s e e d s / p o d

T a b l e 3. V a r i a n c e

l i n e a r f u n c t i o n s of

y ' s a r e g i v e n i n T a b l e 4 . B a s e d o n t h i s , t h e 11 p o p u l -

between clusters and the variance-covariance

a n a l y s i s of 100 v a r i e t e s r e p r e s e n t -

e n c e s a m o n g t h e m e a n s f o r e a c h of t h e e i g h t c h a r a c t e r s

The maximum

eight characters

to e a c h o t h e r

Clusters

Days to flower x3

D a y s to mature x4

Pod size

0.057 0.240

-0.931 -1.063 146.933

-0.455 -0.490 14.546 134.941

0.012 -0.040 -0.721 0.588 0.202

x5

and within this

x's = actual means y's = transformed uncorrelated

N o . of seeds/pod x6

100 s e e d weight x7

Seed colour x8

0.016 0.040 0.831 0.569 -0.050 0.115

-0.269 -0.985 14.551 13.700 0.705 -0.920 35.744

0.174 0.558 0.148 -3.631 -0.389 0.294 -6.069 3.429

x(7)

x(8)

Table 4. The coefficients of x in the uncorrelated linear functions of y

y(1) y(2) y(3) y(4) y(5) y(6) y(7) y(8)

x(2)

0.245 -0.721 0 375 0 162 - 0 287 - 0 372 - 0 174 - 0 366

2. 129 0.286 O. 109 0.497 -0.470 0.399 -1.447

x(3)

0.085 -0.007 0.014 -0.019 -0.028 -0.014

x(4)

0.087 -0.011 -0.018 -0.024 0.010

x(5)

x(6)

2.326 0.075 -0.236 0.946

3.358 1.813 -0.665

I, II,

II a n d IV (D = 1 . 4 8 ) a n d IV a n d V (D =

matrix for the eight characters

Flower colour x2

x(1)

181

ing the eleven populations showed significant differ-

Results The means

Collection of Chick Pea

0.213 0.074

0.889

means

182

R.K.

J. Narayan Table

andA.

J. Macefield:

Genetic

5. Inter and intracluster

Divergence

average

in aWorld

Germplasm

Collection of Chick Pea

D 2 values

Cluster

I

II

III

IV

V

VI

I

0.57

3.04

7.63

3.16

2.51

1.79

II III

(0.76)

(1.74) 0.90 (0.95)

(2.76) 4.07 (2.02)

(1.78) 2.20 (1.48) 8.46 (2.91

(1.58) 3.11 (1.76) 5.06 (2.25) 2.21 (1.49)

(1.34) 1.52 (1.23) 4.71

III IV

(2.17)

1.83 (1.35) 1.18 (1.09)

V VI The D values

are given

in parenthesis.

1,5

"~

|

N

O,5 '~

|

Population

I II III IV V VI

3, 4,

Cluster

very

VI which

approximately V. Moreover

is of unknown

origin has to clusters

I and II have and 0.950 diversity

small

but

in itself.

Asia

and the Near

intra cluster

respectively,

suggesting

D

related

East.

values

Clusters of 0.755

substantial

genetic

within themselves.

The mean cluster

from

Fig.2. Group constellations of 11 populations chick pea (Cicer arietinum) in ~I - ~2 chart

them.

origins but are closely

average

values

prised

largely of spreading

whereas

clusters

mum

in clusters

clusters

6. Clusters

for each

I, II and VI corn-

Mean

I and

II, IV and V

(13.80).

Cluster

3

average

number

I, If, V and

of seeds

(18.78),

(16.64)

of seeds

and cluster

plant type,

VI

Ill having

of contribution

seed colour,

per pod.

and

per pod

plants,

was

maxi-

intermediate low

( 1.61 ) followed

the lowest

III

value for the

intermediate value

to total divergence

100 seed weight,

Plant type (28.1%

in

in cluster

the highest

VI having

of

semi-spread-

100 seed weight

IV showed

clusters (1.37)

to semi-spreading

If, IV and V contained

ing and erect types.

The order

for the eight characters

are given in Table

2

-1,5

I, II, IV and

to be heterogeneous

1

-1,0

2

that the 27 lines in this cluster have

different geographical to the material

between

equal distances

suggest

0

|

5, 7 8, I0, 9 6 11 I

little divergence

it appears

This might

J

@

|174 @-0,5

Intercluster distances are shown in D values, and intracluster distances as D 2 (Table 5)

showed

I

and their inter-relationships

Cluster

1.49)

-1

-2

-3

Fig. 1. Clusters

|

I

L

by

values (1.23). was

and number

of the total pair-

R. K. J. Narayan

and A. J. Macefield:

Table

Germplasm

for the eight characters Days to flowering

Days to mature

Pod size

No. of seeds per pod

I00 seed weight

Seed colour

I II III IV V VI

1.580 1.952 2.400 2.025 2.130 1.950

1.550 2.330 1.650 2.025 2.000 1.956

107.970 104.550 103.850 104.230 104.040 106.530

179.80 177.95 178.68 177.28 175.23 180.57

2.35 2.20 2.09 2.40 2.31 2.38

1.35 1.41 1.23 1.61 1.43 1.30

19.03 15.60 13.80 17.76 16.57 18.53

2.75 1.57 3.25 3.06 4.28 3.08

Table

7. The canonical

vectors

C. vector

Plant type

Flower colour

Days to flower

Days to mature

Pod size

Seeds per pod

I00 seed weight

Seed colour

Z1 Z2 Z3

-0.6524 O. 1926 0.6674

0.0755 0.4953 0.2607

0.0089 0.0146 0.0638

-0.0092 -0.0434 -0.0087

0.3365 0.0928 0.0712

0.2858 0.4475 0.0481

0.4672 0.3627 0.2746

0.3940 -0.6124 0.6322

sum

of all canonical

roots

&l = 19.837

&2 = 3.390

Contribution

of~ 1 = 71.88

have

character

was

(9.64

43 = 2.40

by

(16.26

~). The

seed

of similar

portance

colour

factors

of plant type,

ulations

of each 2 sug-

at both the lev-

is reflected

flower

per pod and

colour,

pears

Analysis independently

derived

lysis to verify the grouping Canonical

vectors

six canonical X 2 3.390,

obtained

~3 2.40,

the total variation

more

is explained

fore the predominant

a considerable

ical vectors

accounted

second

role in further

The absolute

magnitude

would

ters in primary

Since

84.16

alone

7o of

adequate

accounted

vectors

A similar

although

sign in vectors

I and

are changed.

3, The

could imply a balancing

optimum

between

different

situation is observed

for seed

of a lesser

magnitude

2 and 3. Hundred

tant in all the four vectors an important

are

Plant type ap-

vectors

in the vectors

in sign between

weight

indicating their relative

in canonical

effect for an intermediate plant types.

100 seed

with change

seedweight

and appears

role in the divergence

of

is impor-

to have

between

played popula-

tions. for

the second

for 20.97

~. There-

essentially

and third vectors

re-

playing

3. Factor

of canon-

indicate the relative role of characdifferentiations.

The ira-

Analysis

The total correlation factor loadings tors

divergence.

in the coefficients

and secondary

change

colour,

of the rela-

is considered

axis of variation

the first vector,

of the

~1 is 19.837,

~ of the total variation, together

sum

by the first two canoni-

the first vector

than 71.87

ana-

D 2 statistic.

representation

of the varieties

and third vectors

mains

of which

and the rest 1.97.

cal roots a two dimensional

Although

by

are given in Table 7. The

roots is 27.597

tive positions

by canonical

seed colour,

differentiations.

the directions

pop-

coefficients in the sec-

vectors

in secondary

to be important

although were

seeds

colour,

between

coefficients

Similarly,

in their corresponding

importance

Clusters

in the corresponding vector.

reflected

seed

differentiations

of the first canonical

ond and third canonical

els of differentiation.

2. Canonical

I00 seed weight,

and pod size in the primary

~) and the number

contribution

parellel in intra and interclusterD

the influence

;~3 = 8 . 6 9 Yo

~2 = 12.28

to the maximum

followed

100 seed weight

per pod

= 27.597

~

contributed

divergence,

~),

of seeds

Fig.2.

183

Collection of Chick Pea

Flower colour

comparisons)

gesting

in aWorld

Plant type

intercluster (23.01

means

Divergence

Cluster

The

wise

6. The cluster

Genetic

were

matrix

is given in Table

and communalities

found

to be

adequate

than 84 ~ of the total communality. the eight variables

is represented

each factor the magnitude

of these

8 andthe

in Table

9. Two fac-

to account

for more

Although

each

of

by a coefficient

in

coefficients

deter-

R. K. J. Narayan

184

Table

and A. J. Macefield:

8. Total correlation Plant type xl

xl x2 x3 x4 x5 x6 x7

matrix

Genetic

Divergence

for eight characters

in a World

in Chick

Germplasm

Collection of Chick Pea

pea

Flower colour x2

Days to flower x3

Days to mature x4

Pod size x5

No. of seeds per pod x6

100 seed weight x7

Seed colour x8

0.2839

-0.1879 -0.1790

-0.0957 -0.0861 0.1033

0.0654 -0.1813 -0.1325 0.1127

0.1182 0.2422 0.2021 0.1444 -0.3275

-0.1100 -0.3361 0.2008 0.1973 0.2628 -0.4533~

0.2298 0.6149~ 0.0066 0.1688 -0.4687~ 0.3967 -0.5482~

Significant at 5 %level ~ Significant at 1 ~ level. The diagonal values being unity are omitted

Table

9. Factor

loadings

Plant characters

I. 2. 3. 4. 5. 6. 7. 8.

As

mines

38.9

loadings

were

of seeds

per pod and seed colour.

seed weight degree. vour

significant,

for flower

are also implicated

The loadings

of seed colour,

days to flowering

Original

Calculated

0.361 0.598 0.132 0.249 -0.250 0.442 -0.322 0.416

-0.219 -0.504 0.396 0.505 0.176 - 0 . 109 0.402 -0.647

0.284 0.615 0.202 0.197 0.263 0.397 0.263 0.615 2.835

0.179 0.612 0.174 0.317 0.093 0.207 0.266 0.592 3.346

The first factor con-

~ of the total communality

and the factor colour,

number

111

123

36.9

47.2

notypes is polygenic in nature. Evaluation of subspecific differentiation and adaptive processes should therefore be done using populationparameters drawing upon the full resources of the genetic variabilityoffer-

P lant type and hundred

ed by that population. As pointed out by Stebbins (1965)

although

the action of natural

in the second flower

Communalities

2

of the different variables

tributed

factor were

colour,

and days to seed

to a lesser in fa-

I00 seed weight, maturity.

and evolution

tion of the population duals.

as a whole

Plant populations

of ecotypes rather

is a func-

than of indivi-

rest ricted to limited geograph-

ical area or subjected

to identical environmental

sures

gene

evolve

served man

adaptive

by genetic

selection.

complexes

linkage or stringent

Such

co-adaptive

which

pres-

are con-

natural or hu-

adjustment

of the ge-

was

operate

architecture

formation

Chick

From

Figure

geographically clusters

under

1 and Table adjacent

have

crop

a change

5 it wOuld group

clusters

is al-

acceler(Steb-

and no inin its breed-

environmental

countries

I and If. However,

na-

of phe-

in natural populations

suggesting varied

because

of the indivi-

systems

pea is an inbreeding

is available

ing behaviour

and their ul-

of a population

behaviour

in the breeding

ated the genetic divergence bins 1957).

to alarge

on the frequency

by the breeding

Changes

genes

features,

tural selection would The genetic

dependent

between

effects on morphological

notypes.

duals. response

selection

extent on the relationships timate

so controlled Discussion Adaptive

factor analysis

1

% of the total original communality

differentiation.

in the centroid

coefficients

of factors

the relative importance

in intra-specific

Factor

Plant type Flower colour Days to flowering Days to maturity Pod size N o . of s e e d s / p o d 100 s e e d w e i g h t Seed colour Total

Contribution

and communalities

conditions. be

seen

that

together

into

I (intracluster

R. K. J. Narayan

and A. J. Macefield:

Genetic Divergence

in a World

Germplasm

185

Collection of Chick Pea

D = 0 . 7 5 5 ) and II (D = 0 . 9 5 ) c o m p r i s e s u b s t a n t i a l g e -

VI o v e r l a p s t h e p r i m a r y and s e c o n d a r y c e n t r e s of o r i -

n e t i c d i v e r g e n c e within t h e m s e l v e s and c o v e r l a r g e

gin s u g g e s t e d by V a v i l o v .

g e o g r a p h i c a l a r e a . A f u r t h e r a n a l y s i s b a s e d on T o c h e r ' s

The p r i m a r y c h a r a c t e r s c o n t r i b u t i n g to g e n e t i c d i -

c l a s s i f i c a t i o n (Rao l o c . c i t . ) will be a t t e m p t e d to e x a -

v e r g e n c e h a v e v a r i o u s l y b e e n r e p o r t e d in d i f f e r e n t c u l -

m i n e the i n t r a g e o g r a p h i c a l d i v e r g e n c e in t h e s e p o p u -

t i v a t e d c r o p s . D a y s to 50 % f l o w e r i n g , plant h e i g h t ,

l a t i o n s . A c c o r d i n g to V a v i l o v (1951) t h e Indian c e n t e r

and tiller number

are reported

and the C e n t r a l A s i a t i c c e n t e r a r e the p r i m a r y c e n t r e s

divergence

of o r i g i n ( d i v e r s i t y ) of c u l t i v a t e d c h i c k p e a . The N e a r

Murty

E a s t e r n c e n t r e is s u g g e s t e d to be a s e c o n d a r y c e n t r e .

In chick pea however,

of grain crops

and Tiwari

tant ingredient The inclusion of the eight varieties from States in cluster II suggests

the possible

the United

ter IV comprises

Asia in the recent past. Clus-

varieties from

to Mexico

to the Mexican

Mexico.

by Spaniards

Columbina

dates

centre. back

Its introduction

era. Despite the close relatedness

northern

India for example

totally different agro-climatic

breeding

system,

cluster.

spreading

plant type becomes

genetic isolation

the differentiation

distinct ecotypes

may

1965, Gregor

1938,

netic differentiation

(Harland

(Swaminathan in Mexico

upon the

and the extent of into

be slow or very rapid (Bennett

under

1948),

reported

in Piswn inSouth

cultivated potatoes in India

1968) and pigeon peas

(Swaminathan

of such rapidge-

intense selection pressures

in new habitats are already America

of the Mexican

of a species

1939). Examples

transpiration

(C~anus

c~an)

1970).

plant type prevents

excess

Human

selection on seed weight, num-

ber of seeds per pod and seed colour could have acted as causes

of secondary

significant

negative

weight and number correlations

differentiation.

correlations

and seed colour. extensively

Table 8 shows

between

I00 seed

of seeds per pod. Similar negative

are also observed

between

The large seeded

in the Middle

other Mediterranean

seed

'Kabuli'

weight

type grown

east, India, Afghanistan

regions

likely that a conscious

is light coloured.

and It is

selection for seed-weight

resulted in an unconscious

Further

independent

tions by canonical

has

selection for seed colour as

graphical distances alone. Geographical barriers pre-

derived by D 2 analysis, type,

s e l e c t i o n f o r d i v e r s e a d a p t i v e g e n e c o m p l e x e s m u s t be

first canonical vector,

r e s p o n s i b l e f o r t h i s g e n e t i c d i v e r g e n c e . Ben n et t (1970)

of these characters

h as r e f e r r e d to r a p i d e c o t y p e d i f f e r e n t i a t i o n e v e n in

this species.

the a b s e n c e of r e p r o d u c t i v e i s o l a t i o n in o u t b r e e d i n g

seeds per pod and

s p e c i e s . S i m i l a r g e n e t i c d i v e r g e n c e is r e p o r t e d by T i m o t h y (1963) in

100 seed weight,

secondary

classification of these popula-

analysis confirms

v e n t i n g g e n e flow o r e l s e i n t e n s e n a t u r a l and h u m a n

Brass~ca,

specially advantageous In tropical regions how-

indicated by the negative correlations.

The m a x i m u m i n t e r c l u s t e r d i v e r g e n c e of c l u s t e r III

(1965) in

a

enabling the plant to survive under semi-

f r o m t h e r e s t cannot be e x p l a i n e d on the b a s i s of g e o -

M u r t y et a l .

where

conditions

Depending

selection pressure

it is cultivated as a winter

availability of sunshine,

for efficient photosynthesis.

arid conditions. varieties into a separate

In

of clus-

and natural sel-

has resulted in the genetic divergence

Chick pea

and intensity of sunshine.

ever an erect and bushy ection under

differentiation.

1970). impor-

Chick pea is

to the early post-

ter IV to clusters I, II and V, human

and Panwar

in tropical and sub tropical regions

daylength

crop with suboptimal not indigeneous

Ram

plant type was the most

grown

in the

et al., loc.cit. ;

introduction with varying

of these varieties from

1967 ; Jawahar

for primary

is extensively

to be important

(Vairavan

Fig. 2. The magnitudes

of plant

seed colour and pod size in the reflects the relative importance

in the primary

Similarly

seed

I00 seed

differentiation

third canonical

the classification

vectors.

colour, weight

differentiation flower

colour,

important

in the

is reflected in the second The changes

coefficients of plant type and seed colour between

r e l a t i o n s h i p b e t w e e n c l u s t e r s I, II, V and VI s u g g e s t s

tors indicate a balancing

h o m o g e n e i t y in e c o t y p i c d i f f e r e n t i a t i o n . Such h o m o g e -

timum

n e i t y co u l d s u g g e s t g e o g r a p h i c a l p r o x i m i t y to the c e n -

selection.

t r e s of o r i g i n of a p a r t i c u l a r s p e c i e s . It c o u l d a l s o

Factor

of the major

o p e r a t i n g on t h e s e v a r i e t i e s . H o w e v e r , in c h i c k p e a ,

ter and intraspecific

the g e o g r a p h i c a l d i s t r i b u t i o n of c l u s t e r s I, II, V and

examined

a meaningful

forces responsible

differentiation.

the genetic divergence

op-

of natural and human

analysis is useful to provide

assessment

vec-

effect for an intermediate

diverse influences

s u g g e s t s i m i l a r i t i e s of n a t u r a l and h u m a n s e l e c t i o n

and

in the signs of the

m a i z e , and V a i r a v a n et a l . (1973) in Oryza. The c l o s e

under

of

Murtyet

for the inal. (1970)

in the populations

of

186

R.K. J. Narayan

and A. J. Macefield 9 Genetic Divergence

five cultivated crops using centroid method analysis. From number

their analysis

it was

of factor

found that the

of factors and the factor loadings were

influ-

in a World Germplasm

implementation improvement

of advanced

crop. This was

Frankel

association between

the characters

under

stringent se-

and

reduced

genetic

(1950) has rightly remarked

failure depends

upon the recombinational

tributed substantially to the total communality

great technological advancements

with the reproductive

and to those characters

related to the components

fitness under natural and human situation is observed total communality Flower

38.9 % of the

of seeds per pod and seed col-

loadings in the first factor. The

inclusion of flowering time and seed maturity important,

of

contributed by the first factor.

colour, number

our, have important

ical mutagenesis

selection. A similar

in chick pea where

was

was con-

capacity of the species

"the success

or

Despite

in chemical

the

and phys-

evident during the genetic

are more

variability

readily found

cultivars and their wild relatives. This

the urgent need for large scale exploration

and conservation

of these varieties to enrich the breed-

ing stocks for future crop improvement.

time as

in the second factor suggests the significant

contribution of these characters

for the competitive

ability of these varieties under natural selection. Chick pea is important

as a major

etable protein in the predominantly

source

AcknowledGements

of veg-

cereal diet of de-

veloping nations like India. Despite the significant role of this crop in maintaining

an optimum

protein-

calorie ratio (Sukhatme

1970)in

large masses

very little effort was

of people,

for its genetic improvement

the everyday

diet of made

till recently. Most

of the

present day varieties are primitive cultivars. In contrast to the modern

cultivars of cereals

which are

of intense directional selection for yield and

products

that adaptive

useful for crop improvement

emphasises

As

variability".

it is increasingly

last three decades,

in the primitive

variability.

on the adaptability in the crop, that is

lection. They also found that the first factor which con-

cerned

practices for the

itive cultivars with high yielding varieties with phenotypic uniformity

in the genetic

breeding

of this crop will soon replace the prim-

enced by the past history of selection on a particular attributed to the changes

Collection of Chick Pea

We are grateful to Dr. B.R. Murty, Director, Nuclear Research Laboratory, I.A.R.I., New Delhi, for his encouragement to pursue this analysis and his helpful suggestions in the interpretation of the result. We thank Dr. V. Arunachalam for providing the computer programmes. One of us (R.K.J.N.) is grateful to Dr. M.S. Swaminathan, Director General, ICAR for his continued interest in this work and providing facilities. Our sincere appreciations and thanks are due to Mrs. S. Hyder and other staff members of the computer unit, U.C.W., Aberystwyth for their assistance in processing the data. We are grateful to Prof. H. Rees, Dept. of Agricultural Botany, for his kind suggestions in the preparation of the manuscript.

these varieties contain substantial genetic

uniformity, variability. Modern

breeding

programmes

tion of yield and phenotypic artificial environments practices,

the major

controlled. erodes

aim at the maximisa-

uniformity

tailored to suit

created by advanced components

This trend towards

agricultural

of which

are strictly

increasing

uniformity

the genetic variability in the cultivated crops.

Reduction

in the genetic variability has often resulted

in the poor

adaptive responses

diverse environmental

of crop

varieties

to

pressures.

The present evaluation of the chick pea germplasm collection has revealed comprised

substantial genetic variability

in these primitive varieties collected from

all over the world.

The

multivariate

tors influencing adaptive responses

analysis

gence in these primitive cultivars has shown cant interrelations co-adaptive

of fac-

and genetic diversignifi-

of genetic traits in the evolution of

gene complexes

and ecotypes.

The recent

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Dr. R.K.J. Narayan and Dr. A.J. Macefield Department of Agricultural Botany The University College of Wales Penglais Aberystwyth SY23 3DD ( United Kingdom)