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The study was conducted to assess the genetic diversity and
heritability of 147 exotic cotton genotypes for cotton leaf curl virus, yield
and fiber traits. The analysis of variance was highly significant for all the
traits indicate the existence of sufficient genetic variability among the
genotypes. The maximum genotypic and phenotypic coefficient of variance was
estimated for cotton leaf curl virus, seed cotton yield plant-1,
bolls plant-1. Whereas, the plant height, GOT, staple length
uniformity index, micronaire value and fiber strength found as moderate GCV and
PCV. High heritability coupled with high genetic advance over mean percent was
observed for cotton leaf curl virus, seed cotton yield plant-1, boll
weight, plant height, GOT, bolls plant-1, and micronaire value which
indicate that additive gene action is involved for controlling the traits. The
higher heritability with moderate genetic advance was recorded for fiber
strength and staple length, it occurrence the involvement of additive and
non-additive gene action. Whereas, uniformity index was found as high heritability
with low genetic advance suggested the influence of non-additive gene action. The
cluster 6 revealed highest mean values for bolls plant-1, GOT, seed
cotton yield plant-1, staple length and uniformity index. The
cluster 5 produced highest mean values for plant height and boll weight. While,
the cluster 4 obtained utmost mean values for micronaire, fiber strength and
cotton leaf curl virus. Therefore, the cluster analysis confirms that
sufficient genetic diversity among the genotypes for various traits studied.
The genotypes of these 3 clusters (cluster 4, 5 and 6) could be utilized in
cotton development strategy for yield, fiber traits and CLCV.

 

Key words: genetic diversity,
cluster analysis, variability, PCV, GCV, Cotton.

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Introduction

            Cotton is
important cash crop grown in Pakistan and it contributes significantly to the
national economy and is key source of livelihood for the rural people. The crop
is grown in hot and humid areas, where there are elevated pest hazards as some
insects and cotton leaf curl virus (CLCV) are particularly deleterious to yield
and its quality. Cotton leaf curl virus has appeared as important disease of
cotton in the country. The genetic diversity regarding CLCV is very extremely
low in locally evolved genotypes, which is major threat for cotton crop in the
country. Besides the cotton leaf curl virus diversity, various other traits
i.e. morphology, yield, fiber, insect pest and disease resistant is also
important Iftikhar et al. (2010).

 

            For any breeding
program diverse germplasm is essential, it is a precious material which
provides the source of genetic variability. Abd El-Sayyed et al. (2006)
reported that by utilizing cluster analysis techniques for measuring genetic
diversity to select promising lines in a certain cotton population. While
evaluating such level of variance would be helpful for selecting appropriate cotton
genotypes for enduring breeding program. According to Aremu (2005)
present association model of cluster analysis among genotypes and mutually
elite group arranged in such a way that same represent can exactly be assemble
in to same cluster.

 

            The knowledge
about genetic parameters i.e. phenotypic coefficient of variance (PCV),
genotypic coefficient of variance (GCV), genetic advance and heritability is
important to assess the characters for genetic improvement. These genetic
parameters are practical tools which help the breeder to plan appropriate
breeding strategy to achieve the objectives. The present investigation was
conducted to assess the genetic diversity among cotton genotypes by using
genetic variability, heritability and cluster analysis to choose the potential
genotypes for resistant against cotton leaf curl virus, yield and fiber traits
for utilization in breeding program.

 

 

Material and Method

            The research was
conducted at the experimental field of central cotton research institute Sakrand
during the year 2016-17. The seed of one hundred forty seven (147) cotton
genotypes were planted during the Kharif season, to evaluate the cotton leaf
curl virus, yield and economic characters. All the inputs and plant protection
measures were applied as per need of the crop. For the data recording 10 plants
were tagged from each genotypes and noted the characters seed plant height,
cotton yield plant-1, boll weight (g), bolls plant-1, GOT
(%), staple length (mm), uniformity index (%), micronaire value, fiber strength
(g tex-1) and cotton leaf curl virus disease (%). The data were statistically analyzed by using statistical
software Statistical Tool for Agricultural Research (STAR), Opstat and
Statistix-8.1. Cotton leaf curl virus (CLCuV) disease reaction was assessed
according to disease rating scale (Table-1) suggested by Akhtar et al.
(2010) and Farooq et al. (2011).         

 

Table-1: Cotton Leaf
Curl Virus (CLCuV) disease symptoms rating scale described by Akhtar et al.
(2010) and Farooq et al. (2011)

Symptoms

Disease rating

Disease Index (%)

Disease reaction

No
symptoms

0

0

Resistant

Thickening
of only secondary and tertiary veins

1

0.1-10

Highly tolerant

Thickening
of tertiary veins, secondary and primary veins

2

10-30

Tolerant

Vein
thickening, leaf curl or enation or both

3

30-50

Susceptible

Stunting
alone with vein thickening, leaf curl or enation

4

>50

Highly susceptible

 

Result and Discussion

            The analysis of
variance (ANOVA) mean square values presented in table-2, which shown highly
significant variation among the all genotypes for the characters studied, it
indicated the availability of abundance genetic variability in genotypes. Usually
maximum heritability values indicate the phenotypic and genotypic closer
values; these are very helpful for the selection of trait to improve plant
style. Only heritability does not endorse the amount for genetic improvement
that would be helpful for choosing the best individual, to some extent it rely
on the amount of genetic variation. Consequently, genetic advance and genetic
advance over mean expend the magnitude to provide the proposed amount of
progress that can be accomplish by selection.

 

Table-2: Analysis of variance (ANOVA) mean squares and basic
statistics of traits.

Source of Variation

Genotypes

Error

C.V (%)

LSD (5%)

LSD (1%)

Plant
Height (cm)

1334.2**

2.03

1.04

2.2

3.0

Bolls  Plant-1

284.6**

0.43

2.39

1.0

1.3

Boll
Weight (g)

1.80**

0.02

5.50

0.2

0.3

GOT
(%)

59.86**

0.03

0.57

0.3

0.3

Seed
Cotton Yield Plant-1 (g)

2380.83**

1.13

1.94

1.7

2.2

Staple
Length (mm)

12.37**

0.03

0.69

0.3

0.3

Uniformity
Index (%)

12.59**

0.11

0.40

0.5

0.7

Micronaire
value

1.20**

0.05

5.15

0.3

0.4

Fiber
Strength (g tex-1)

15.86**

0.44

2.41

1.0

1.4

CLCuV
(%)

982.53**

0.62

3.27

1.2

1.6

 

            The genetic
variability parameters; heritability, phenotypic coefficient of variance (PCV),
genotypic coefficient of variance (GCV) and genetic advance (GA) are depicted
in table -3, the PCV and GCV expressed in percentage to evaluate the
variability observed between the various traits. The maximum PCV and GCV was
estimated in cotton leaf curl virus (74.7/74.6), seed cotton yield plant-1
(51.5/51.5), Bolls plant-1 (35.5/35.4) and boll weight (27.4/26.9),
while moderate was observed for plant height, GOT, staple length, uniformity
index, micronaire value and fiber strength. 
The slight difference in coefficient of variance phenotypic and
genotypic indicated that characters are less affected by environment. Similar findings
reported by Ahsan et al. (2015), Raza et al. (2016), Shao et
al. (2016), Meena and Meena (2017) higher PCV and GCV for bolls
plant-1, boll weight and seed cotton yield plant-1 in
cotton genotypes. Whereas, low to moderate PCV and GCV for plant height, GOT
and fiber traits.

 

Table-3: Genetic variability parameters for various traits.

Traits

PCV

GCV

h2
(%)

GA

GA over mean (%)

Plant
Height (cm)

15.4

15.3

99.5

43.3

31.5

Bolls  Plant-1

35.5

35.4

99.5

20.0

27.8

Boll
Weight (g)

27.4

26.9

95.9

1.5

54.3

GOT
(%)

13.6

13.5

99.8

9.1

27.9

Seed
Cotton Yield Plant-1 (g)

51.5

51.5

99.8

57.9

106.0

Staple
Length (mm)

7.4

7.4

99.1

4.1

15.1

Uniformity
Index (%)

2.4

2.4

97.3

4.1

4.9

Micronaire
value

14.5

13.5

87.4

1.1

26.1

Fiber
Strength (g tex-1)

8.5

8.1

92.0

4.4

16.1

CLCuV
(%)

74.7

74.6

99.8

37.2

153.6

 

                Robinson et al. (1949)
categorized the heritability for various traits; low (60%). The genetic advance over mean percent classified for
different characters; >20% high, 10-20% moderate and 0-10% low were reported
by Johnson et al. (1955). High heritability combine with high genetic
advance over mean percent was recorded for cotton leaf curl virus (99.8 and
153.6), seed cotton yield plant-1 (99.8 and 106.0), boll weight
(95.9 and 54.3), plant height (99.5 and 31.5), GOT (99.8 and 27.9), bolls plant-1
(99.5 and 27.8), micronaire value (87.4 and 26.1) estimation of high
heritability with high genetic advance indicated that additive gene action is
involved for the controlling of these traits and it proposed the scope of
selection for these traits in cotton improvement. The fiber strength and staple
length were recorded high heritability with moderate genetic advance (92.0 and
16.1) and (99.1 and 15.1) respectively, it occurrence the involvement of
additive and non-additive gene action. The uniformity index was observed with
high heritability (97.3) and low genetic advance over mean percent (4.9), it
suggested the influence of non additive gene action for uniformity index. These
findings are according with Ahsan et al. (2015), Kumar and Katageri
(2017), Meena and Meena (2017). Osman and Khirdir (1974) reported that
high heritability coupled with high genetic advance is indication of additive
gene effects and accordingly with high genetic expand from selection would be
expected. Whereas, the low heritability together with low genetic advance is  resulting of non-additive gene effect and
expected low genetic gain from selection. 
 

 

            A dendrogram was
developed from cluster analysis of 147 exotic cotton genotypes into six
clusters on the basis of ten traits (yield, fiber traits and CLCV) presented in
fig.1. Cluster 1 contained 32 genotypes, cluster-2 included 45, cluster-3 into 16,
in cluster-4 was 10, cluster-5 comprised on 21 and cluster-6 included 23
genotypes depicted in table-5. The cluster 6 revealed highest mean values for bolls
plant-1 (35.5), GOT (38.1), seed cotton yield plant-1
(104.3), staple length (29.3) and uniformity index (86.8), the germplasm in
cluster 2 might be exploited in cotton improvement plan for maintaining the
traits to produce maximum yield. The cluster 5 produced highest mean values for
plant height (151.1) and boll weight (3.9). Whereas, the cluster 4 obtained
utmost mean values for micronaire (4.0), fiber strength (31.5) and cotton leaf
curl virus (9.6). Therefore, the cluster analysis confirms that sufficient
genetic diversity among the genotypes for various traits studied. The genotypes
of these 3 clusters (cluster 4, 5 and 6) could be utilized in cotton
development strategy for yield, fiber traits and CLCV. The wide range of
variation in germplasm through cluster grouping have been reported by Ayana
and Bekele (1998), Grenier et al. (2001), Haider et al.
(2012), Nazir et al. (2013) and Saeed et al. (2014)

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