Directory UMM :Data Elmu:jurnal:S:Scientia Horticulturae:Vol84.Issue1-2.Apr2000:

Scientia Horticulturae 84 (2000) 49±66

Estimation of variability parameters within
`Mysore' banana clones and their implication
for crop improvement
J.A. Sirisenaa,*, S.G.J.N. Senanayakeb
a

Regional Agricultural Research Centre, Department of Agriculture, Bandarawela, Sri Lanka
b
Department of Agricultural Biology, Faculty of Agriculture, University of Ruhuna,
Mapalana, Kamburupitiya, Sri Lanka

Received 14 October 1998; received in revised form 16 March 1999; accepted 16 July 1999

Abstract
A study was conducted with diverse accessions of Musa cv Mysore for a three year production
period to investigate the possibilities for genetic improvement through within-clone selection. Thus,
the phenotypic and genotypic variability, broad sense heritability (h2), phenotypic coef®cient of
variation (pcv), genotypic coef®cient of variation (gcv), expected genetic advance (ega) and
phenotypic and genotypic correlations were studied on economically important characters of

banana cv Mysore. Also the direct and indirect effects of some selected characters on yield were
studied.
From the pcv, gcv, h2, ega and genotypic and phenotypic correlations, it was found that the
pseudostem girth, fruit maturity period, bunch weight, total fruit weight, average fruit weight and
fruit circumference in the second comb had high genotypic variation and genotypic correlations
which would be bene®cial for crop yield improvement for banana cv Mysore through within-clone
selection. Fruit maturity period had a signi®cant negative correlations with yield and yield
components.
High levels of correlated responses in improvement of bunch weight could be obtained when
selection was made for average fruit weight and pseudostem girth. Selection for average fruit
weight was also likely to improve total fruit weight. Selection for a short fruit maturity period was
found bene®cial since fruit maturity period had negative correlated responses for improving bunch
weight and its components. The correlated response of the selected characters on improvement of
average fruit weight was very low. Selection for total fruit weight had a high response in
improvement of fruit circumference in the second comb.
*
Corresponding author. Tel.: ‡94-5722499; fax: ‡94-5722520.
E-mail address: ddrbwela@sri.lanka.net (J.A. Sirisena).

0304-4238/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.

PII: S 0 3 0 4 - 4 2 3 8 ( 9 9 ) 0 0 0 9 4 - 1

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J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

Path analysis revealed that average fruit weight had a high positive direct effect on bunch weight
while fruit circumference in the second comb, pseudostem girth and fruit maturity period had high
indirect effects on bunch weight via average fruit weight. Thus, a useful path diagram to show the
relationship of average fruit weight, pseudostem girth, fruit circumference in the second comb and
fruit maturity period to bunch weight has been proposed. # 2000 Elsevier Science B.V. All rights
reserved.
Keywords: Genetic variation; Genetic correlation; Musa spp.; Mysore; Path-analysis

1. Introduction
Bananas (Musa spp.) are native to Southeast Asia and make a most important
contribution to the international fruit industry in South and Southeast Asia
(Valmayor et al., 1991). Also there is no other fruit in the world, which surpasses
banana and plantains either in production tonnage or in trade volume in fresh
form (FAO, 1985). From its centre of origin in Southeast Asia, the banana was

introduced to all tropical and subtropical regions of the world where it gained
great importance and popularity (Simmonds and Shepherd, 1955). Banana is an
extremely frost-sensitive perennial with long life under proper farm management
techniques (Valmayor et al., 1991). The banana plant itself emerges above ground
from its rhizome in the form of overlapping long sheaths, which appear to form
the stem or trunk of the plant and are called a pseudostem. The plants emerge
continuously from a single rhizome. Therefore, a banana clump consists of
several plants in different growth stages on the one rhizome. The true stem of
banana plant emerges in the growth cycle through these overlapping leaf sheaths,
bearing an in¯orescence at its top. The in¯orescence drops `bracts' one by one
over a period of 5±7 days. As each `bract' falls from the stem it reveals a double
row of banana known as a `comb'. The bunch consists of several combs attached
to the peduncle, the distal part of the true stem. The time required from
emergence of sucker to harvesting varies with the cultivar and ranges from 1 to
1.5 years.
Of the numerous fruits grown in Sri Lanka, banana claims 69±70% of the total
area under fruit cultivation. Among the 28 cultivars grown in the country
(Simmonds, 1966), `Mysore' (`Embul', AAB group) is the most popular. The
average yield of cv Mysore varies from 12 to 16 t haÿ1 under irrigation. (Mannion
et al., 1992). Therefore, a crop improvement program is essential in order to

increase the potential yield. Since edible Musa are parthenocarpic, plants are
propagated using vegetative parts such as rhizomes and suckers from which
genetic variability does not arise. Therefore, crop improvement is dif®cult in
edible bananas. Genetic variability is created in Musa mainly through
hybridisation (through diploid bananas) (Vuylsteke and Swennen, 1993),
somaclonal variation (Hwang and Tang, 1996) and induced mutation (Silayoi

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

51

et al., 1995). However, their high capital involvement and time-consumption limit
the usefulness of these methods. Large numbers of banana and plantain cultivars
such as Mysore. Silk, Pisang ambon and Pisang awak (cooking type) have been
identi®ed based on existing natural variability (Simmonds, 1966). Also the
genetic variability between these cultivars has been extensively studied (Sree
Rangaswamy et al., 1980; Rosamma and Namboodiri, 1990; Rekha and Prasad,
1993). However, the information generated from these studies cannot be used
with respect to the within cultivar genetic improvement. In other words, the
existing genetic diversity between `Mysore' and `Silk' could not be used to

improve `Mysore' or `Silk' through selection using natural genetic variability.
This shows the importance of the exploitation of within clone genetic variability
to improve particular banana clone through selection.
The natural variability in existing populations of clones may occur due to
spontaneous mutations followed by natural selection as a response to climatic
stresses and to different environments (Wright, 1931). This variability may be
found in physiological and/or morphological characters of banana (Simmonds,
1966). Spontaneous mutations are important in banana improvement because it is
the only genetic variability that occurs naturally within the banana clones creating
new sub-clones. Spontaneous mutants have been reported in Musa with respect to
agronomic, bunch and fruit characters (Simmonds, 1966); i.e. off-types in `Gros
Michel' banana in Jamaica (Larter, 1934) and the dwarf plants of wild bananas
(Richardson, 1961). The `Dwarf Cavendish' banana is a mutant of an unknown
clone (Gross and Simmonds, 1954). The number of mutants that exists in a
population is proportional to the population size and the period of cultivation
(Simmonds, 1966), but in excess of the evolutionary needs (Wright, 1921),
occurring at a frequency of about 10ÿ4 per generation (Watson, 1970).
However, there is apparently no work reported on genetic improvement of
banana using variability and character association within a particular clone. Thus,
the objectives of the present study were to estimate the (1) phenotypic and

genotypic variability, (2) phenotypic and genotypic correlation between the
characters with signi®cant genetic variation, including yield with respect to
correlated response to selection, (3) direct and indirect effects of important
characters on yield using path coef®cient analysis and to (4) suggest a proper path
diagram between bunch yield and related characters.

2. Materials and methods
The experiments were conducted at the Regional Agricultural Research and
Development Centre, Angunakolapelssa, Sri Lanka (6±108N latitude; average
annual rainfall 1200 mm and 30 m elevation) during the period from 1992 to
1995.

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J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

2.1. Planting materials
Out of 200 banana accessions from Musa cv Mysore (`Embul' AAB group)
which had been collected from different agro±ecological zones representing a
major portion of the island of Sri Lanka, 37 banana accessions showing diversity

were included in the study. These banana accessions were multiplied in the ®eld
using naturally emerging suckers, in order to obtain suf®cient amount of planting
materials uniform in size and age.
2.2. Experimental design
Banana accessions were grown in a randomised complete block design with
three replications. Two clumps from each accession were maintained in each
block. The number of clumps per block was 74.
2.3. Crop management
Sword suckers, uniform in size (1.5±2.0 m long) and age (2 12 ±3 months) were
used as planting materials. Blades of large leaves of suckers and all the dead
portions of the rhizomes were removed. The rhizomes were treated with
`Dithane' fungicide mixed with dry wood-ash. Treated suckers were kept under
shade for about 24 h before planting. The suckers were planted in July 1992 in
planting holes (45 cm  45 cm  45 cm) with both within and between row
distance of 3 m. Each planting hole was ®lled with well-decomposed cattle
manure mixed with topsoil. Dolomite was applied as a calcium and magnesium
source at the rate of 600 g per planting hole as recommended by the Department
of Agriculture, Sri Lanka. Banana cultivar Pisang awak (dessert type) plants were
established around the experimental area to avoid border effects and wind
damage.

Carbofuran (3%) granules was applied at the rate of 15 g per planting hole at
the time of planting to control banana nematode Radopholus similis (Cobb)
Thone. When no rainfall for more than 10 days the soil was irrigated every 10
days so as to bring it to ®eld capacity to a depth of 75 cm. Fertiliser mixture of
12 : 8 : 34 (N : P2O5 : K2O) recommended by the Department of Agriculture was
applied at the rate of 450 g per clump at two months after planting. This was
repeated at four-month intervals. Fertiliser was applied at a 45 cm radius around
the clump at 3±5 cm deep in the soil. The ®rst daughter sucker was allowed to
emerge at four months after planting and the second was allowed to emerge at
¯owering (8±9 months after planting). The third one was allowed to emerge at the
time when the bunch matured (10±12 months after planting). Subsequently, one
additional sucker was allowed to emerge whenever the mother plant was removed
from the clump as a result of harvesting. Therefore, each clump consisted of one

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

53

plant until four months after planting, two plants from 4 to 9 months after
planting and three plants at 12 months after planting. Thereafter, three plants in a

clump with an age difference of 3±4 months were maintained. Harvesting was
done when one fruit of the ®rst or second comb of the bunch turned yellow. The
®rst year harvests were taken from the original plant and from a sucker that
emerged subsequently in each clump. Two harvests per clump were then taken
from two different suckers in each subsequent harvest year.

3. Data collection
Data were collected from the crop for three years in the present study. Two
harvests per clump were taken in each year from two different suckers. It has also
been observed that the maximum harvest potential in the clump of `Mysore'
banana was obtained in the ®rst harvest year itself (the second year of the crop),
the harvest per clump did not vary signi®cantly in the second or the third year
over the ®rst year (Sirisena and Senanayake, 1997). Therefore, data collection
was performed from the ®rst harvest year onwards.
3.1. Growth characters
The following growth characters were recorded: (1) Leaf blade length was
measured as a direct measurement from leaf blade base to the tip of the leaf at the
time of ¯owering. (2) Leaf blade breath was measured at the point where the
maximum breath exists in the leaf at the time of ¯owering. (3) Pseudostem girth
was measured 10 cm above the ground level at the time of harvesting. (4)

Pseudostem height was measured from the ground level to the base of the leaf
petioles at the time of harvesting. These measurements were recorded from the
two suckers per clump in each year from 1993 to 1995.
3.2. Fruit characters
The following fruit characters were recorded: (1) Fruit maturity period
measured from emergence of the in¯orescence to harvesting of the bunch. (2)
Bunch weight including 60 cm of peduncle before the ®rst comb. (3) Number of
combs having more than four ®lled fruits (true combs). (4) Total fruit weight as
the total weight of the true combs. (5) Number of fruits per bunch as counted only
on true combs. (6) Number of fruits per comb as calculated from the total number
of fruits and the number of combs. (7) Average weight of the fruit as calculated
from the total weight of the fruits and the total number of fruits. (8) Weight of the
second comb. (9) Fruit circumference in the second comb measured at the middle
of the fruit by wrapping a measuring tape around it. (10) Fruit length in the

54

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

second comb taken after removing fruit stalk and the bottle-neck part in the distal

end of the fruit. Fruit measurements were taken from three fruits per comb. These
measurements were recorded at each harvest of the clump during the three years
from 1993 to 1995.

4. Statistical procedures
4.1. Phenotypic and genotypic components of the variability
The following statistical model was used in the analysis
Pijk ˆ m ‡ gi ‡ yj ‡ bk ‡ …gy†ij ‡ eijk ;

(1)

where Pijk is the measured value for the ith accession in the jth year in the kth
block; m is the population mean; gi is the effect of the ith accession; yj is the effect
of the jth year; bk is the effect of the kth block; (gy)ij is the interaction between the
ith accession and the jth year; ejik is the random error component (includes
interaction effect of block with accessions, year and accession  year).
4.2. Phenotypic and genotypic variances
The analysis of variance and the expected mean squares (EMS) performed as
described by Hanson et al. (1956) and Singh and Choudhry (1985) are presented
in Table 1. The phenotypic variance s2p of a character comprises the genotypic
variance (s2g ) and the environment variance (s2e ). This relationship could be
expressed symbolically as follows:
s2p ˆ s2g ‡ s2e ;

(2)

Table 1
Analysis of variance and the expected mean squares for the model Pijk ˆ m ‡ gi ‡ yj ‡ bk ‡ …gy†ij
‡eijk : (r, a and y symbolise numbers of replicates, accessions and years, respectively; s2e :
environmental variance; s2y : variance due to year; s2a : variance due to accessions; s2ay : variance due
to AXY interaction effect)
Source

df

Expected mean squares

Blocks
Treatments
Accessions (A)

rÿ1
tÿ1
aÿ1

±
±
s2e ‡ rs2ay ‡ r:ys2a

Years (Y)

yÿ1

A Y

(aÿ1)(yÿ1)

Error

(tÿ1)(rÿ1)

s2e ‡ rs2ay ‡ r:as2y

s2e ‡ rs2ay
s2e

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

55

where s2e and s2g were estimated using EMS as follows
EMSaccessions ÿ EMSaccessionyear ˆ rys2g
…s2e ‡ rs2ay ‡ rys2a † ÿ …s2e ‡ rs2ay † ˆ rys2a ˆ rys2g ;

where, r ˆ 3 and y ˆ 3; then s2g could be computed.
Since s2e ˆ EMS for error, phenotypic variance was computed as follows:
s2p ˆ s2g ‡ EMS:

(3)

4.3. Estimation of broad sense heritability (h2), phenotypic coef®cient of
variation (pcv), genotypic coef®cient of variation (gcv) and expected genetic
advance (ega)
In this study h2 was calculated as the ratio of s2g and s2p . The ega of a given
character was estimated considering 5% selection from the parent population by
the method of Falconer (1976) and Singh and Choudhry (1985). The gcv and pcv
were computed for each character as described by Johnson et al. (1955) in order
to make comparisons between different characters.
4.4. Phenotypic and genotypic correlation
The covariance analyses were performed between the characters which showed
signi®cant variations among banana accessions. The covariance analyses were
performed as suggested by Singh and Choudhry (1985) and they are presented in
Table 2.
Estimates of covariance for environment (cove) and covariance for accessions
(covg) were obtained from the analysis. The phenotypic covariance (covp) was
expressed as cove ‡ covg and computed accordingly. The phenotypic correlation
Table 2
Analysis of covariance and the expected mean product for the model Pijk ˆ m ‡ gi ‡ yj ‡ bk
‡…gy†ij ‡ eijk (r, a and y symbolise numbers of replicates, accessions and year, respectively; cove:
environmental covariance; covy: covariance due to year; cova: covariance due to accessions; covay:
covariance due to AXY interaction)
Source of variation

df

Expected mean products (MP)

Blocks
Treatments
Accessions (A)
Years (Y)
A Y
Error

rÿ1
tÿ1
aÿ1
yÿ1
(aÿ1)(yÿ1)
(tÿ1)(rÿ1)

±
±
cove ‡ r.covy ‡ r.y cova
cove ‡ r.covay ‡ r.a covy
cove ‡ r.covay
cove

56

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

and genotypic correlation were estimated using following equations as described
by Falconer (1976);
covg
Genotypic-correlation n ˆ q ;
(4)
s2Gx1
s2Gx2
Phenotypic-correlation

covp
n ˆ q ;
s2Px1
s2Px2

(5)

where x1 and x2 are the two characters between which correlation was measured.
The expected change in one character as a result of selecting for another was
estimated in the following manner as described by Singh and Choudhry (1985);
Ry ˆ ihx
hy
rgxy
spy ;

(6)

where, Ry is the expected change in x by selecting y; i is the selection intensity; hx
is the heritability of x; hy is the heritability of y; rgxy is the genotypic correlation
coef®cient between x and y; spy is the phenotypic standard deviation of y.
4.5. Path analysis.
The path-coef®cients for direct and indirect effects were estimated for four
important characters with bunch yield. The path-coef®cient for direct and indirect
effects of x1 on bunch yield (y) is as follows (Singh and Choudhry, 1985)
rx1 y ˆ a ‡ rx1 x2
b ‡ rx1 x3
c ‡ rx1 x4
d;

(7)

where, rx1 y is the genetic correlation between the character and bunch yield; a, b,
c and d, are the direct effects of character x1, x2, x3, and x4, respectively on bunch
yield; y is the bunch yield; rx1 x2 :b, rx1 x3 :c and rx1 x4 :d, are the indirect effects of x1
and y via x2, x3 and x4, respectively.
Three more equations could be written as above for the direct and indirect
effects of x2, x3 and x4 on y. Solving the four equations, a, b, c and d could be
calculated. Since r values are already known, The indirect effect can be calculated.
Residual effects can be calculated as follows (Singh and Choudhry, 1985);
p
Residual-effect ˆ 1 ÿ a ‡ b ‡ c ‡ d:
(8)
5. Results
5.1. Phenotypic and genotypic variability
The mean squares for year, accessions and year  accessions with respect to 14
characters studied are presented in Table 3. The weight of the second comb and

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

57

Table 3
Analysis of variance Ð mean squares for analysis of 14 characters in Musa cv Mysore
Character

Mean squares
Year

Weight of second comb (kg)
Fruit Circumference in second comb (cm)
Bunch weight (kg)
Total fruit weight (kg)
Bunch maturity period (d)
Pseudostem girth (cm)
Average fruit weight (g)
F. length in second comb (cm)
No. of fruits per comb
Leaf length (cm)
Leaf width (cm)
Pseudostem height (cm)
No. of combs per bunch
No. of fruits per bunch
a
b

Accession
b

0.03
2.70a
52.80a
36.20a
188.0a
4538.00a
3034.00a
2.78b
54.10a
834.35a
39.85a
277 661.00a
69.90a
40 769.00a

a

0.71
2.36a
33.80a
22.20a
82.00a
112.00a
413.00a
4.12a
4.21a
4200.00a
128.58a
2097.00b
2.68b
1430.00b

Accession  year
0.17a
0.79b
11.83b
7.61b
32.80b
54.00b
231.00b
2.19a
300b
228.40b
5.18b
1023.00b
2.25b
1370.00b

signi®cant at 5% probability level,
not signi®cant

fruit length in the second comb showed signi®cant interaction between accessions
and year despite the signi®cant difference between accessions. Pseudostem
height, number of combs per bunch and number of fruits per bunch did not show
signi®cant difference between accessions. The rest of the nine characters showed
signi®cant difference between accessions but their accessions  year interaction
was not signi®cant (Table 3).
5.2. pcv, gcv, h2 and ega
The genetic analysis made for the nine characters which showed stable
differences between accessions is presented in Table 4. The gcv, pcv, h2 and ega
values are presented for the characters investigated (Table 4). The range of
phenotypic values in comparison to the general mean showed wide variability for
most of the characters studied (Table 4). A very low heritability value was
computed for number of fruits per comb (4%). The rest of the characters showed
heritability estimates of 13% or more. The expected genetic advance (ega) was
low for the number of fruits per comb (0.7%), bunch maturity period (1.3%) and
pseudostem girth (3.8%). The rest of the six characters showed ega estimates
more than 5% (Table 4).

58

Character

Leaf width (cm)
Leaf length (cm)
F. circumference in second comb (cm)
Bunch weight (kg)
Total fruit weight (kg)
Bunch maturity period (d)
Pseudostem girth (cm)
Average fruit weight (g)
No. of fruits per comb
a

Value

Heritability (%) egac (%)

Coefficient

Mean

Range

Phenotypic

Genotypic

pcva (%)

gcvb (%)

71.20
222.00
11.50
12.66
10.70
103.60
66.10
60.30
15.28

60.0±84.0
147.0±270.0
9.0±14.2
5.5±24.0
4.7±20.2
70.0±118.0
43.0±93.0
33.0±150.0
8.0±20.0

29.72
983.40
0.62
9.84
7.53
39.00
48.60
147.20
2.61

13.70
421.50
0.17
2.38
1.82
5.49
6.4
20.19
0.11

7
14
6
24
25
6
10
20
11

5
9
3
12
12
2
4
7
8

Phenotypic coef®cient of variation.
Genotypic coef®cient of variation.
c
Expected genetic advance at 5% selection.
b

Variance

46
43
27
24
24
14
13
13
4

5.8
8.0
4.3
14.5
13.7
1.3
3.8
7.2
0.7

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

Table 4
Phenotypic and genotypic components of variability and coef®cients of variation, broad sense heritability and expected genetic advance in growth and
bunch characters of Musa cv Mysore

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J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

Table 5
Phenotypic and genotypic correlation coef®cients among six characters of Musa cv Mysore
(`Embul' banana)
Character

Character
X1

Pseudostem
girth (X1)
Fruit maturity
period (X2)
Bunch weight
(X3)
Total fruit
weight (X4)
Average fruit
weight (X5)
F. Cir. second
comb (X6)
a
b

X2

X3

X4

X5

±
ÿ0.28 (ÿ0.03)b
0.77a (0.40a)

ÿ0.55a (ÿ0.15)

0.78a (0.36)

ÿ0.48a (ÿ0.08)

0.96a (0.91a)

0.87a (0.15a)

ÿ098a (ÿ0.16)

0.99a (0.62a)

0.99a (0.59a)

0.52a (0.16)

ÿ0.72a (ÿ0.17)

0.99a (0.44a)

0.94a (0.45a)

0.75a (0.41a)

Indicates signi®cant at 5% probability level.
Indicates phenotypic correlation coef®cients given in parenthesis.

5.3. Phenotypic and genotypic correlations
The phenotypic and genotypic correlation coef®cients of the six important
characters are presented in Table 5. The number of fruits per comb, leaf length
and width did not have signi®cant genetic correlation with the rest of the
characters, so they were not presented in Table 5. Fruit maturity period had
negative correlation with the bunch weight and its components. The positive and
high correlations were estimated between bunch weight and its component
characters.
Estimates of expected progress in improving bunch weight by selecting for
other characters (expressed in percentage of the progress expected from selecting
for bunch weight itself) are presented in Table 6. It shows that selection for other
Table 6
Progress expected in bunch weight resulting from selection for other characters expressed as a
percentage of the change expected when selection was done for bunch weight itself
Character on which the selection is performed

Progress expected in bunch weight (%)

Total fruit weight
Fruit Circumference in second comb
Average fruit weight
Pseudostem girth
Fruit maturity period

40.0
14.6
200.0
91.0
ÿ33.0

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J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

Table 7
Progress expected in total fruit weight resulting from selection for other characters expressed as a
percentage of the change expected when selection was for total fruit weight itself
Character on which the selection is performed

Progress expected in bunch weight (%)

Bunch weight
Fruit Circumference in second comb
Average fruit weight
Pseudostem girth
Fruit maturity period

47.0
14.5
113.0
51.8
ÿ30.0

characters particularly the average fruit weight and pseudostem girth has
signi®cant impact on the improvement of bunch weight. Selection for fruit
circumference in the second comb had a very low impact on the bunch
improvement. Estimates of expected progress in improving total fruit weight by
selecting for other characters (expressed in percentage of the progress expected
from selecting for total fruit weight itself) are presented in Table 7. Selection in
favour of average fruit weight increases the total fruit weight more than the
selection for bunch weight or direct selection for total fruit weight itself.
Selection for high pseudostem girth had a considerable correlated response on
improvement of total fruit weight. Estimates of expected progress in improving
average fruit weight by selecting for other characters (expressed as a percentage
of the change expected when selection was done for average fruit weight itself)
are presented in Table 8. It appears that the correlated response to increase
average fruit weight as a result of selecting for bunch weight and some of its
component characters was low (Table 8). Estimates of expected progress in
improving fruit circumference in the second comb by selecting for other charcters
(expressed as a percentage of the change expected when selection was done for
fruit circumference in the second comb itself) are presented in Table 9. Selection
in favour of total fruit weight increases the fruit circumference in the second
comb as much as 1.8 times that of direct selection for fruit circumference itself.
Tabel 8
Progress expected in average fruit weight resulting from selection for other characters Ð expressed
as a percentage of the change expected when selection was done for average fruit weight itself
Character on which the selection is performed

Progress expected in average fruit weight (%)

Bunch weight
Total fruit weight
Fruit Circumference in second comb
Pseudostem girth
Fruit maturity period

16.6
14.5
3.0
17.6
ÿ45.0

61

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

Table 9
Progress expected in fruit circumference in second comb resulting from selection for other
characters expressed as a percentage of the change expected when selection was done for fruit
circumference in second comb itself
Character on which the selection is performed

Progress expected in fruit circumference
in second comb (%)

Bunch weight
Total fruit weight
Pseudostem girth
Average fruit weight
Fruit maturity period

22
180
6
15
ÿ84

However, selection for fruit circumference in the second comb did not improve
bunch weight (Table 6), total fruit weight (Table 7) or average fruit weight (Table
8). Moreover, selection for long fruit maturity period had a high negative
response (±84%) on the fruit circumference in the second comb.
5.4. Path coef®cients for direct and indirect effects
The direct and indirect effects of average fruit weight, fruit circumference in
the second comb, pseudostem girth and fruit maturity period on the bunch weight
are presented in Table 10. The average fruit weight had a very high direct effect
(1.50) on bunch weight. The pseudostem girth had a negative direct effect despite
the high positive correlation coef®cient with bunch weight. However, pseudostem
girth had a high indirect effect with bunch weight via average fruit weight. Fruit
circumference in the second comb showed a low positive direct effect on bunch
yield, low positive indirect effect on bunch yield fruit maturity period but very
high positive indirect effect via average fruit weight (Table 10). The direct and

Table 10
Path coef®cients for direct and indirect effects of some of the important characters on bunch yield
of banana cv Mysore estimated through path coef®cient analysis
Character

Genotypic correlation Effects on the bunch yielda
with bunch yield
Direct Indirect effect via other characters
effect
X1
X2
X3
X4

Average fruit weight (X1)
0.99
F. Cir. in second comb (X2)
0.99
Pseudostem girth (X3)
0.77
F. maturity period (X4)
ÿ0.55
a

Residual effect ˆ 0.22.

1.50
±
0.63
1.12
ÿ0.68
1.30
ÿ0.87 ÿ1.47

0.47
±
0.32
ÿ0.45

ÿ0.59
ÿ0.35
±
0.19

0.85
0.62
0.24
±

62

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

indirect effects of fruit maturity period were generally negative with the bunch
weight.

6. Discussion
6.1. Phenotypic and genotypic components of the variability
With respect to the characters with signi®cant interaction effects of
accessions  year, the differences between accessions varied over years so that
selection of accessions for these characters would be dif®cult due to the lack of
stability of the average effects over years (Table 3).
Among the 12 characters with no signi®cant accession  year interaction, main
effects for accessions were found to be useful only in 9 characters while leaving
the rest of the characters unimportant for genetic variability among accessions
(Table 3). Among the nine characters, bunch weight, average fruit weight and
total fruit weight had a considerable pcv higher than 15% (Table 4). Only bunch
weight and total fruit weight had a gcv more than 10% indicating some promise
for genetic improvement. Sree Rangaswamy et al. (1980) estimated pcv and gcv
as 29% and 25%, respectively, for bunch weight, and 14% and 13%, respectively,
for stem girth in a range of dessert banana cultivars. The low pcv and gcv
estimated in the present study may be either due to the occurrence of low
spontaneous mutation rates (Wright, 1931) or to the small population size or to
both reasons. Out of the nine characters on which genetic analysis was done, only
bunch weight, leaf length and average fruit weight had moderate h2(13±43%) and
ega (7.2±14.5%) showing promise for genetic improvement (Table 4). Higher
heritability (75%) and ega (75%) were estimated for bunch weight and average
fruit weight in a large number of banana cultivars (Rekha and Prasad, 1993) may
be due to wide genetic variability of the germplasm belonging to different
genomic groups. It has also been reported that heritability estimates would be
reliable if accompanied by a high ega (Singh and Choudhry, 1985).
6.2. Phenotypic and genotypic correlations and correlated responses
Although the population size is comparatively low, considerable s2p and s2g were
found to exist between accessions for some of the characters which are likely to
relate with crop yield and fruit size. The pseudostem girth was positively
correlated with the bunch weight (Table 5). Therefore, selection for this character
may increase bunch weight as a correlated response. Selection for high
pseudostem girth should result in increase in bunch weight as much as if
selection is made on bunch weight itself (Table 6). This enables early selection of
superior accessions with respect to bunch weight. Results indicate that the

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

63

correlated response to yield of a character is very important for crop yield
improvement in addition to the other variability parameters. However, the prerequisites for a character to have a correlated response to yield are its high s2g ; h2
and high genetic correlation with yield. Surprisingly, as a correlated response to
bunch weight, the selection for high average fruit weight resulted in an increase in
bunch weight that was twice as great as of selection for bunch weight itself (Table
6). This is because the genotypic correlation between average fruit weight and
bunch weight was very high despite the moderate values of genetic variability, h2
and ega computed for average fruit weight (Table 5). However, low genetic
correlation (0.56) than that in the present study (0.77) was estimated between
pseudostem girth and the bunch weight in a large number of banana cultivars
(Rosamma and Namboodiri, 1990). Apparently, there are no reports on the
quanti®cation of correlated responses in banana for the comparison.
Selection for high fruit circumference in the second comb did not improve
bunch weight (Table 6) or average fruit weight (Table 8) as a correlated response
because phenotypic and genotypic variances of fruit circumference in the second
comb were very low (Table 4). Only a low progress could be made in average
fruit weight as a result of selecting for even bunch weight (16.6%), and
pseudostem girth (17.6%) (Table 8). Thus, average fruit weight can only be
improved through direct selection. Low expected progress (6%) in pseudostem
girth as a result of selecting in favour of fruit circumference in the second comb
may be due to low variances in fruit circumference of the second comb and the
low genetic correlation between the two characters. Rosamma and Namboodiri
(1990) were unable to observe a signi®cant genetic correlation between fruit
circumference and pseudostem girth in a range of banana cultivars.
Since, fruit maturity period had high negative correlations and correlated
responses (Tables 5±9) with bunch yield and its components, selection for early
maturity is expected to increase crop yield. However, a minimum length in the
maturity period is necessary for maximum yield. As a correlated response, the
fruit circumference in the second comb expects to be increased only when
selections done in favour of total fruit weight (Table 9). This suggests that high
genetic correlation between character and the crop yield is an important
requirement in addition to the high variability of the character for ef®cient
selection. Thus, genotypic correlation with crop yield may help to identify
characters, which would be useful in a selection program for yield. However, in
the present study genetic variability and variability components were estimated
based on the performance of genotypes in one location. Therefore, results could
be varied in another location due to signi®cant location  accession interaction.
However, the magnitude of variability components and character association of
these banana accessions provide valuable information for improving bunch yield
and the fruit size of `Mysore' banana through selection for this location and
locations with similar environments. This experiment was carried out under

64

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

typical environmental conditions prevailing during 1992±1995 at the Regional
Agricultural Research and Development Centre, Angunakolapelessa, Sri Lanka
and some of the climatic parameters during this period have been reported
previously (Sirisena and Senanayake, 1997). Improvement of fruit size increases
the unit price of the produce in banana due to the higher fruit grade. The high
bunch yield increases the productivity of the crop. Mannion et al. (1992)
estimated the average yield of the banana cv Mysore in a range of 12±16 t per
hectare per year while average yield in the present study being 25 t per hectare
per year (with the 1000 clumps per hectare and two harvests per clump per year).
This could be due to high management under the experimental conditions.
However, the bunch weight in the different accessions used in this study ranged
from 5.5 to 24 kg projecting the yield range of 11±48 t per hectare per year. This
shows the potential for increasing bunch yield by selecting the superior banana
accessions with respect to the characters identi®ed in this study.
Based on s2g , h2, ga and genotypic correlations and correlated responses, the
average fruit weight, total fruit weight, fruit circumference in the second comb,
pseudostem girth and fruit maturity period were identi®ed as important traits in a
selection program to improve bunch yield of Musa cv Mysore through withinclone selection. Also studies on direct and indirect effects of those characters on
bunch yield are important for an ef®cient selection program.
6.3. Path coef®cients for direct and indirect effects
The negative direct effect of pseudostem girth on bunch weight is misleading
because it has a positive correlation with bunch weight. This could be a result of
the indirect effect of pseudostem girth via average fruit weight, fruit
circumference in the second comb, fruit maturity period and other characters
not considered for path analysis. Results suggest that selection in favour of
pseudostem girth increase the bunch weight by changing the magnitude of
component characters. A very high positive correlation between average fruit
weight and bunch yield is mainly due to a positive direct effect and to positive
indirect effects on bunch weight via fruit circumference in the second comb and
fruit maturity period (Table 10). However, the negative indirect effect of average
fruit weight on bunch yield via pseudostem girth may be explained as a negative
direct effect of pseudostem girth on bunch yield. Fruit maturity period had
negative direct and indirect effects on bunch weight except via pseudostem girth
indicating that selection for a short maturity period may be always bene®cial. As
described by Belalcazar et al. (1991), this may occur because once the
in¯orescence has emerged, apical dominance is removed and the growth of
suckers enhanced, initiating competition between newly growing suckers and the
bunch for food reserves in the rhizome. Therefore, shorter the fruit maturity
period higher the competitive advantage of the bunch.

J.A. Sirisena, S.G.J.N. Senanayake / Scientia Horticulturae 84 (2000) 49±66

65

Fig. 1. Suggested path-diagram for correlation between bunch weight and some of the yield
components in Musa cv Mysore.

The higher path coef®cient for average fruit weight is due to its direct effect on
bunch yield. On the other hand, for all the other characters, the highest path
coef®cients were recorded always via average fruit weight. Therefore, in the path
diagram the effect of average fruit weight on bunch weight was basically direct
while the effects of the other three characters on bunch weight were basically
indirect via average fruit weight. Thus, the suggested path diagram is given in
(Fig. 1).

Acknowledgements
The authors acknowledge the Council for Agricultural Research Policy, Sri
Lanka for providing ®nancial support. We are very much thankful to Dr Sumith
Abesiriwardena for his technical guidance in preparing the paper.

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