GENETIC DIVERSITY AND CORRELATED RESPONSE TO SELECTION OF GRAIN YIELD AND ASSOCIATED CHARACTERS IN MAIZE (Zea mays L.)

_____________________________________________________________________________________________________
*Corresponding author: Email: obbello2002@yahoo.com;
Original Research Article
Journal of Basic and Applied Research
International
13(1): 56-61, 2016
ISSN: 2395-3438 (P), ISSN: 2395-3446 (O)
International Knowledge Press
www.ikpress.org
GENETIC DIVERSITY AND CORRELATED RESPONSE TO
SELECTION OF GRAIN YIELD AND ASSOCIATED
CHARACTERS IN MAIZE (Zea mays L.)
J. O. AGBOLADE1
, O. J. OLAWUYI2
, O. B. BELLO3*
, O. D. OLUSEYE1
AND R. J. 1. KOMOLAFE1
1
Department Plant Science and Biotechnology, Federal University, Oye Ekiti, Nigeria.
2
Department of Botany, University of Ibadan, Ibadan, Oyo State, Nigeria.
3
Department of Biological Sciences, Fountain University, Osogbo, Osun State, Nigeria.
AUTHORS’ CONTRIBUTIONS
This work was carried out in collaboration among all authors. Author JOA designed the study, wrote the
protocol and interpreted the data. Author ODO anchored the field study, gathered the initial data and performed
preliminary data analysis. Author OBB, the corresponding author and authors OJO and RJA managed the
literature searches and produced the initial draft. All authors read and approved the final manuscript.
Received: 22nd
July 2015
Accepted: 20th
August 2015
Published: 3rd
October 2015
__________________________________________________________________________________
ABSTRACT
Sixteen genotypes of maize were evaluated for genetic variability and character associations in the Research
Farm of the Department of Botany, University of Ibadan, Nigeria for 90 days in the 2012, 2013 and 2014
cropping seasons. Perforated polythene bags (18 × 9 cm) were filled with 6kg sandy-loam soil and were spaced
at a distance of 10 cm apart between rows. Three seeds from each genotype were then planted per bag without
treatment in three replicates. Data on plant and stem height, leaf width, leaf length and number of leaves were
collected after planting at 14 days interval on each replicate for a particular genotype. The plant height of
EVDT.Y200STRQPM genotype was significantly (p < 0.05) different from other genotypes, while genotype
pairs; TZE-OR2DTSTRQPM and 2009TZE-ORIDTSTRQPM, TZEI 22, TZEI 98 and OBANTAPA, TZEI 4,
TZEI 161, BODIJA as well as EVDT-W99STR, OJO, 98SYNWECSTRQPM were similar to each other. The
result of correlation coefficient shows that stem height was highly significant and positively correlated with the
plant height (p < 0.01; r = 0.91). The genotype is negative and non-correlated with plant height, stem height, leaf
width and number of leaves, but positive and non-significantly associated with leaf length, replicate and week
after planting.
Keywords: Maize genotype; character; variability; morphology; genetic diversity; germplasm.
1. INTRODUCTION
Maize (Zea mays L.) is one of the most widely grown
grain crops domesticated by indigenous peoples in
prehistoric times with 332 million metric tons
annually in the United States of America [1,2]. The
leafy stalk produces ears which contain grains called
kernels consisting of an endosperm, embryo, pericarp
and tip cap. The kernels are used in cooking as a
vegetable or starch [3]. Sugar-rich varieties called

Agbolade et al.; JOBARI, 13(1): 56-61, 2016
57
sweet corn are usually grown for human consumption,
while field corn varieties are used as chemical feed
stocks [1,2]. Maize also plays an important role in the
prevention of digestive ailments, and can be processed
for a range of uses both as an ingredient in food or
drinks, such as corn syrup in soft drinks or maize
meal and for industrial purposes [4]. The starch part
of the kernel is used in foods and many other products
such as adhesives, clothing, pharmaceutical tablets,
paper production, and can be converted into
sweeteners, and used in products such as sweets,
bakery products and jams. The oil from the embryo is
used in cooking oils, margarine and salad dressings,
while the protein, hulls and soluble part of the maize
kernel are used in poultry feed [5].
The applications of genetics in correlation studies are
used in evaluating variability in maize through
character association [5,6]. Environmental changes
across locations and years due to climatic conditions,
disease and pest pressures, soil fertility and socio-
economic factors affect the yield performance of
maize [5,7]. [4] emphasized the need to select
genotypes that outperform the local commercial
varieties in their 'safety-first screening approach.
Yield stability measures the ability of a variety to
maintain high yields across environments [8.9]. A
stable responsive genotype is one that is able to utilize
resources available in the high yielding environment
while maintaining above average performance in all
other environments. It is only the high yielding, stable
and responsive variety that will satisfy the needs of
farmers in their diverse and changing farming
environments [9]. The morphological characters of
maize which include plant height, stem height, leaf
length, leaf width, tassel arrangement, number of
leaves, ear length, cob diameter and yield may vary
depending on the genotype and environment in which
they are grown [5]. Therefore, this study examined the
contribution of genotypes and growth stages on
variations in morphological characters of maize
germplasm.
2. MATERIALS AND METHODS
2.1 Experimental Site and Sources of Planting
Materials
This study was carried out in an open field at the
Research Farm of the Department of Botany,
University of Ibadan, Ibadan, Nigeria between March
and May, 2012, 2013 and 2014. A total of sixteen
genotypes of maize were evaluated in this study.
Fourteen genotypes were collected from the
germplasm of the International Institute of Tropical
Agriculture (IITA), Ibadan, Nigeria and they include:
TZEI 161, TZEI 98, TZEI 25, TZEI 22, TZEI, TZEI
4, TZEOR2DTSTRQPM, DMRESRWQPM,
EVDTY2000STRQPM, TZEYDTSTRQPM,
EVDTW99STR, 98SYNWECST-RQPM,
2009TZEORIDTSTSTRQPM, OBANTAPA and
TZEYBPDTSTRQPM. Two varieties were also
obtained from Ojo and Bodija markets.
2.2 Research Design and Method of Planting
The experiment was laid out factorially in a complete
randomized design (CRD) with three replicates in
each polythene bag without treatments. Perforated
polythene bags (18 × 9 cm) were filled with 6 kg
sandy-loam soil, and were spaced at a distance of
10cm apart between the rows. Three seeds from each
genotype were then planted per bag without in three
different rows. Thinning was later carried out to leave
one healthy plant per pot at two weeks after planting.
Standard cultural practices such as proper weeding
and watering of plants were also carried out.
2.3 Data Collection and Analysis
Data were collected after planting at 14days interval
on each replicate for a particular genotype. Data on
the following growth characters were taken: Plant
height, Stem height, Leaf width, Leaf length and
Number of leaves. These were measured using a
meter rule in centimeter (cm), except number of
leaves which was determined by counting. Data
collected were subjected to analysis of variance
(ANOVA) using SPSS, version 16.0. The model for
analyses of variance included genotype, replicate,
weeks after planting. The means were separated by
Duncan's multiple range test at 5% level of
probability, while Pearson correlation co-efficient was
also done to establish relationship among the
characters.
3. RESULTS
3.1 Mean Square of Genotype, Replicate and
Different Growth Stages for
Morphological Characters of Maize
The results from Table 1 shows that the weeks after
planting was highly significant (p<0.01) for plant
height, stem height and number of leaves but non-
significant for leaf width and leaf length, while the
genotypic effect was highly significant for plant
height, stem height, leaf width and leaf length and
number of leaves.
3.2 Effect of Growth Stages on Morphological
Characters of Maize
The plant height and stem height are significantly
higher at 8 weeks after planting (WAP) with 71.06 cm

58
and 48.03 cm, respectively than other growth stages
(Table 2). The leaf length (50.86 cm) was the highest
at 2 WAP, while the highest number of leaves (8.21)
and leaf width (3.97 cm) were recorded at 4 WAP.
The 4, 6 and 8 WAP for plant height, stem height, leaf
width and number of leaves were not significantly
different from one another, while the leaf length at 2
WAP was significantly different from other weeks,
but significant differences did not exist between 6 and
8 WAP. The leaf width was not significantly different
from each other for all the weeks.
3.3 Genotypic Variation in Morphological
Characters of Maize
The plant height and stem height of
EVDT.Y200STRQPM were significantly (p<0.05)
higher and different from other genotypes (Table 3).
TZE-QR2DTSTRQPM and 2009TZE-
ORIDTSTRQPM genotypes were not significantly
(p>0.05) different from each other, but different from
TZEI 22, TZEI 98 and OBANTAPA, as well as TZEI
4, TZEI 161, BODIJA and EVDT-W99STR, OJO,
98SYNWECSTRQPM which were not different from
one another, but significantly different from
TZYBPDTSTRQPM.
The stem height for TZE-QR2DTSTRQPM,
2009TZEORIDTSTRQPM, TZEI 22, TZEI 98,
OBANTAPA and TZEI 161 genotypes were not
significantly different from each other, but different
from TZEI 25, TZEI 4 and BODIJA which are not
significantly different from each other. EVDT-
W99STR, OJO and 98SYNWECSTRQPM did not
produce significant effect from each other, but
significantly different from TZYBPDTSTRQPM. The
TZEI 98, 2009TZEORIDTSTRQPM and
EVDT.Y200STRQPM genotypes were significantly
higher but different for leaf width, leaf length and
number of leaves than other genotypes. There is no
genotypic difference among EVDT.Y2000STRQPM,
TZEYDTSTRQPM, TZE-QR2DTSTRQPM and
TZEI-22 as well as OBANTAPA, TZEI 25 and TZEI
4 for leaf width, while similar effect was observed for
BODIJA and OJO markets. The leaf length of
TZEYDTSTRQPM, TZE-QR2DTSTRQPM, TZEI
98, TZEI 25, TZEI 4, BODIJA and OJO produced
similar genetic effect different from TZEI 161,
EVDT-W99STR and 98SYNWECSTRQPM as well
as EVDT.Y2000STRQPM and OBANTAPA. The
genotypic effect for number of leaves per plant was
not significantly different in nine genotypes, while
TZEI 161 and OJO as well as EVDT-W99STR and
98SYNWECSTRQPM had genetic similarities.
3.4 Correlation Co-efficient of Five
Morphological Characters, Genotypes and
Growth Stages of Maize
The results in Table 4 show that stem height was
highly significant and positively correlated with the
plant height (p<0.01; r = 0.91). The leaf length was
highly significant and positively associated with plant
height (r = 0.72), stem height (r = 0.53) and leaf width
(r = 0.83), while the number of leaves was positively
related with plant height (r = 0.87), stem height (r =
0.75), leaf width (r = 0.87) and leaf length (r = 0.73).
The plant height was positive and strongly correlated
with stem height, leaf width, leaf length and number
of leaves with (p<0.01; r = 0.91, 0.87 and 0.72). There
was no association between plant height and
genotypes. Again, the leaf length and number of
leaves were strongly related with leaf width (p<0.01; r
= 0.83 and 0.87) respectively. The genotype was
negative and non-significantly related with plant
height (r = -0.22), stem height (r = -0.15), leaf width
(r = -0.24), leaf length (r = -0.17), number of leaves (r
= -0.19) and growth stages.
4. DISCUSSION
The growth stages and genotypes which recorded high
significant effect on most of the morphological
characters is an indication of variability which is a
key to crop improvement. This conforms to [4] who
had reported significant amount of variability for
different morphological traits in maize genotypes and
also reported significant genetic differences for
Table 1. Mean square of genotype, replicate, weeks after planting of five morphological characters of
maize
Source of variation Df PH SH LWD LL NL
Year 2 10.11 ns
3.21 ns
1.17ns
8.31ns
1.22 ns
Replicate 2 307.49ns
153.85ns
0.17ns
88.02ns
4.26ns
Weeks after planting 3 4210.96**
9034.21**
2.27ns
938.51ns
71.31**
Genotype 15 4069.67**
2933.30** 8.20**
1046.31**
29.81**
Error 171 619.47 421.40 1.88 264.74 6.67
Total 192 700.22 833.67 4.92 300.19 23.64
PH-Plant height, SH-Stem Height, LW-Leaf width, LL-Leaf length, NL-Number of leaves
**
P< 0.01 highly significant,*P< 0.05 significant

59
Table 2. Effect of growth stages on five morphological characters of maize
Weeks after Planting PH(cm) SH(cm) LW(cm) LL(cm) NL
2 50.89b
19.56b
3.49a
50.86a
5.48b
4 69.19a
46.57a
3.97a
45.67ab
8.21a
6 68.13a
46.27a
3.71a
40.40b
7.50a
8 71.06a
48.03a
3.92a
43.34b
7.83a
PH-Plant height, SH-Stem Height, LW-Leaf width, LL-Leaf length, NL-Number of leaves
Means with the same letter in the same column are not significantly different at P< 0.05 using Duncan’s Multiple Range
Test (DMRT)
Table 3. Genotypic variation in five morphological characters of maize
Genotypes PH(cm) SH(cm) LW(cm) LL(cm) NL
1. EVDT.Y2000STRQPM 1.01a
75.04a
4.52abc
51.58abc
9.17a
2. TZEYDTSTRQPM 86.26ab
68.38ab
4.48abc
50.92abcd
6.92abc
3. DMRESRWQPM 85.19abc
56.28bc
4.70ab
53.64ab
8.5ab
4. TZE-OR2DTSTRQPM 77.74bcd
39.85cd
4.18abc
44.94abcd
8.17ab
5.2009 TZE-ORIDTSTRQPM 74.06bcd
40.39cd
4.07abcd
58.69a
8.5ab
6. TZEI 22 71.44bcde
44.29cd
4.50abc
42.73bcd
8.00ab
7. TZEI 98 66.23bcde
37.30cd
4.85a
46.45abcd
8.33ab
8. OBANTAPA 64.02bcde
43.43cd
3.83abcde
51.73abc
7.67ab
9. TZEI 25 62.39cde
34.72d
3.93abcde
47.43abcd
7.58ab
10. TZEI 4 61.74de
34.38d
3.73abcde
45.20abcd
8.75ab
11.TZEI 161 61.43de
39.51cd
3.28cde
36.00cd
6.58bc
12. BODIJA 56.78de
33.02d
3.45bcde
49.21abcd
7.83ab
13. EVDT-W99STR 48.83e
29.22de
2.72ef
37.50cd
5.25cd
14. OJO MARKET 48.43e
27.40de
3.49bcde
49.68abcd
6.42bc
15. 98SYNWECSTRQPM 47.68e
25.78de
2.84def
36.00cd
5.00cd
16. TZYBPDTSTRQPM 23.73f
12.71e
1.78f
19.55e
3.42e
PH-Plant height, SH-Stem Height, LW-Leaf width, LL-Leaf length, NL-Number of leaves per plant
Means with the same letter in the same column are not significantly different at P> 0.05 using Duncan’s Multiple Range
Test (DMRT)
Table 4. Correlation co-efficient of five morphological characters, genotypes and growth stages of maize
PH(cm) SH(cm) LW(cm) LL(cm) NL REP WAP
SH(cm) 0.91**
LW(cm) 0.87**
0.73**
LL(cm) 0.72**
0.53* 0.83**
NL 0.87** 0.75** 0.87**
0.73**
WAP 0.22ns
0.35*
0.08ns
-0.17ns
0.231ns
0.00ns
Genotype -0.22ns
-0.15ns
-0.24ns
0.005ns
-0.19ns
0.00ns
0.00ns
PH-plant height, SH-stem height, LW-leaf width, LL-leaf length, NL-number of leaves, REP-replicate, WAP-week after
planting *, ** significant at P < 0.05 and P < 0.01respectively ns= non-significant
morphological characters of maize genotypes. The
reason for the observed differences in the
morphological characters at different weeks after
planting might be due to the variation in their genetic
makeup [4,10]. These results are in agreement with
those obtained by [4] who had reported significant
amount of variability for different morphological
traits in maize genotypes. [4] also reported increased
performance of heterogeneous populations over those
resulted from selfing. Therefore, the differences
observed for morphological characters in maize
genotypes might be due to genetic variations among
the hybrids. This supported the findings of [11]
who observed similar results on genetic differences
for plant height among different maize hybrids. The
morphological variation in the expression of the
characters however, could be due to the contributions
of genotype, environment and their interactions. The
genotypic variation measures the extent of genetic
variability in a crop species, and also quantifies the
extent of variability in different characters [12].

60
Correlations studies revealed the positive associations
of plant height with stem height, leaf length and leaf
width, and contributed significantly to the production
of number of leaves as similarly observed by [13-16].
The variation in morphological characters is essential
for selection in maize breeding [15,17]. The maize
improvement programme is dependent not only on the
amount of genetic variability present in the
population, but also on the extent to which it is
heritable, which sets the limit of progress that can be
achieved through selection [4,18-21].
5. CONCLUSION
The maize genotypes evaluated exhibited variability
for most of the traits. The morphological characters
could be encouraged for further selection in
improvement of maize breeding in Nigeria. The
findings from this research show genetic variability
among the studied germplasm. Values and data
recorded are representatives of these genetic variants,
and could be used as reference in similar studies.
However, further investigation is needed to examine
the contributions of environmental interaction to the
performance of maize genotypes.
COMPETING INTERESTS
Authors have declared that no competing interests
exist.
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GENETIC DIVERSITY AND CORRELATED RESPONSE TO SELECTION OF GRAIN YIELD AND ASSOCIATED CHARACTERS IN MAIZE (Zea mays L.)

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GENETIC DIVERSITY AND CORRELATED RESPONSE TO SELECTION OF GRAIN YIELD AND ASSOCIATED CHARACTERS IN MAIZE (Zea mays L.)