ABSTRACT
Field experiments were conducted at the Teaching and Research Farm of the Department of
Crop Science, Faculty of Agriculture, University of Nigeria, Nsukka to commence the
process of developing high yielding maize with resistance to stem borers in a humid
environment. The specific objectives were to (i) screen some maize genotypes for agronomic
traits and stem borer resistance (ii) estimate some genetic parameters of the genotypes
studied. Twenty maize genotypes used comprised twelve maize genotypes collected from the
International Institute of Tropical Agriculture (IITA) namely (2009 TZE OR1 DT STR QPM
(TOR1), AMA TZBR – Y – F2 (AMA), TZBR COMP – 2 – YC1F2 (COMP2), BR 9928
DMRSR (B28), DMR – LSR – Y (DMR), TZE – Y – POP DT STR QPM (POP), 2009 TZE
OR2 DT STR QPM (TOR2), 99 TZE Y – STR QPM (99 TZE), BR 9943 DMRSR (B43),
TZBR COMP – YC1F2 (COMP1), EV DT – Y – 2000 STR QPM (EVDT) and TZEE – Y –
POR STR QPM CO (PORC)) and eight (8) local accessions (Ugwuachara (UG), Umukasi
(UM), ORBA1, Obukpa (OB), ORBA2, Edem Ani (EA), Isakpu (IS) and Ajuona (AJ)) from
Enugu state, Nigeria. The parameters measured include days to tasselling, silking, maturity,
stem girth, number of leaves, ear height, plant height, ear length, ear diameter, number of
kernel per row, number of rows per ear, number of kernel per cob, number of ear per plant,
shelling percentage, ear weight, grain yield, brown spot disease, lodging incidence, stem
borer infestation, number of exit holes and tunnel damage length. General combining ability
(GCA) of the parents and specific combining ability (SCA) of the hybrids were estimated
using Graffings’ model 1 method 2 in a 10 x 10 diallel cross. Among the parents, POP and
PORC had significantly (p < 0.05) shorter days to tasselling (55.67 and 56.00) and silking
(57.00 and 58.33), respectively than other genotypes. The parent UG had significantly (p <
0.05) higher ear weight (209.40 g) and grain yield (6.23 ton/ha) among other genotypes. The
ORBA2 parents gave significantly (p < 0.05) higher number of kernel per cob (419.50) and
hundred grain weights (33.60 g) while the parent UM gave the highest number of ears per
plant (1.48). The parent OB obtained the highest stem borer infestation (20 %), number of
exit hole (2.83) and tunnel damage length (7.37 cm). Majority of the hybrids produced
performed significantly (p < 0.05) higher than the parents in most of the traits. The hybrid
UG x ORBA2 had significantly higher ear weight (350 g) and grain yield (11.35 ton/ha). The
hybrid UM x B43 obtained significantly higher number of ear per plant (1.83) while UM x
OB hybrid gave highest number of kernels per cob (611.30). The hybrid B28 x B43 had
highest positive better parent heterosis (BPH) for ear weight (136.56 %) and grain yield
(193.83 %). The hybrid UG x B28 (101.16 %) obtained higher BPH on number of kernel per
cob while UM x B43 (26.88%) was higher on number of ear per plant. The hybrid PORC x
B28 had the least stem borer infestation (6.14 %) while TOR1 x B43 obtained lower number
of exit holes (1.00) and tunnel damage length (7.12 cm). The ORBA1 parent was the best
combiner among all the parents while POP x PORC was the best combiner among all the
hybrids in yield and yield attributes. A cross involving B28 x B43, ORBA1 x B28, ORBA1 x
ORBA2, ORBA2 x B43, PORC x B28, TOR1 x B43, TOR1 x POP, TOR1 x PORC, TOR1 x
UM, UG x B43, UG x UM, UM x B28, UM x B43 and UM x OB could be resistant to stem
borer while a cross involving UG x ORBA2, ORBA2 x B43, ORBA2 x UM, PORC x B43,
UG x B43 and UM x B28 could also serve as potential hybrids for improving maize yield.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgement iv
Table of content v
List of tables vii
Abstract ix
INTRODUCTION 1
LITERATURE REVIEW
Origin and Distribution of maize 3
Climatic and soil requirement 3
Production constraint 4
Maize disease 4
Maize stem borers 4
Genetic diversity and improvement on maize 5
Breeding methods 6
Recurrent selection 6
Phenotypic or simple recurrent selection 8
Combining ability 8
Heterosis 10
MATERIALS AND METHODS
Site Location 12
Land preparation and planting 12
Fertilizer application and weeding 12
Materials 12
Experiment 1 12
Experiment 2 13
Experiment 3 14
Statistical analysis 16
vi
RESULTS
Evaluation of the maize parents 20
Evaluation of the maize parent on the incidence of brown spot disease,
stem borer infestation and lodging. 23
Principal components analysis for the maize parents studied. 25
Correlation coefficient of the maize genotypes studied. 27
Path coefficient analysis of the maize genotypes studied. 29
The mean square and genetic parameters for some of the quantitative
traits studied on the maize genotypes 31
Evaluation of phenological, morphological, yield and yield component
traits of the maize inbred parent 33
Evaluation of incidence of brown spot disease, lodging, stemborer infestation
and stemborer related traits 36
Evaluation of the parent and F1 on phenological, morphological, yield and
yield components traits of the maize genotypes 38
Evaluation of brown spot disease incidence, lodging, stem borer infestation,
number of exit hole and tunnel length on F1 hybrids and the parents of the
maize studied. 43
Estimates of Better Parent Heterosis (BPH) on the phenological, morphological,
yield and component traits of the maize hybrid studied. 46
Estimates of Better Parent Heterosis (BPH) on brown spot disease
incidence, lodging incidence and stem borer infestation and stem borer
related traits on the maize genotypes 49
The variance component of the General Combining Ability of (GCA)
and Specific Combining Ability (SCA) of the maize traits studied. 51
Estimate of General Combing Ability (GCA) of the maize parents. 55
Estimate of the specific combining ability (SCA) of the maize hybrid use
in the study 60
DISCUSSION 64
Conclusion and recommendation 71
REFERENCES 72
Appendix
CHAPTER ONE
Maize (Zea mays L.) belongs to the family of grass Gramineae (Poaceae). It is a tall,
monoecious annual plant with male and female flowers in separate places on the same plant
with an extensive fibrous root system. Its centre of origin is Mesoamerican region, now
Mexico and Central America (Doebley, 1994) and its domestication started at least 6000
years ago. Maize is one of the most productive and widely adapted crop species in the world.
It is cultivated in all parts of the world except Antarctica. Loamy or silty loam soil or silty
clay loam is the ideal soil type for its cultivation and a pH of 6.5 to 7.5 is the most preferred
for its growth. It is among the leading cereal crops after wheat and rice with regard to
cultivation area, total production and consumption (Olakojo and Akinlosotu, 2004;
CIMMYT, 2004; Olawuyi et al., 2010). Global production amounted to 130 million hactare
with output of 574 million metric tons (Ito, 1998).
Maize is an important staple food crop for millions of people both in developed and
developing countries. It is relatively high yielding, easy to digest, easily processed and
cheaper than other cereals. In Nigeria, maize is used directly for human consumption as well
as infant nutrition in the form of porridge during weaning period, without any protein
supplement such as egg, meat or beans which are comparatively expensive especially for
poor-resource families in the rural areas (Yusuf, 2010). In Africa, maize is consumed as a
starchy base in a wide variety of porridges, pastes, grits and beer. Fresh harvested maize is
eaten parched, baked, roasted or boiled and plays an important role in filling the hunger gap
after dry season. The starch extracted from maize grain is used in making confectionary and
noodles. It could be used as feed for livestock and other industrial purposes.
Several breeding methods have been used by maize breeders to develop new cultivars and the
choice of a specific breeding method will depend on the type of cultivar. Recurrent selections
method has been used for population improvement of maize (Roger et al., 1998; Leta, 2010)
with prospect of improving yields and other agronomic traits. The use of phenotypic recurrent
selection has been effective in improving characters such as protein, yield, oil, maturity of
maize and its cycle can be completed within two years (Obi, 2006). Studies comparing effects
of different selection procedures exist in the literature (Ajala et al., 2009) and one could
expect 2 to 7% increase per cycles in grain yield depending on the germplasm and selection
method (CIMMYT 1981; Darrah, 1986). Breeding for improved varieties requires a thorough
2
understanding of the genetic mechanisms governing yield and yield components (Saleem et
al., 2002; Unay et al., 2004).
In Africa, maize production is constrained by a number of stress factors including a complex
of pests and diseases that significantly reduce the quality and quantity of production (Akande
and Lamidi, 2006). Insects (e.g. stem borer) and mites are among the most important pests of
maize (Bosque- Perez, 1995). Stem borer causes losses ranging between 5-73% of potential
yield loss under different agro-ecological conditions (Seshu-Reddy and Walker 1990; De
Groote 2002; De Groote et al., 2003). In spite of the importance and high demand of maize in
Nigeria, yield across the country has not been able to meet the increasing population and the
yield potential of our present varieties has not been fully explored. Thus, there is need to
utilize available genetic resources to reconstruct the ideotype of the plant in order to meet the
increasing population and profitable maize production through improvement in grain yield,
pest (stem borer) or disease resistance and other desirable agronomic traits.
The objectives of this study were to:
1. screen maize genotypes for yield, agronomic traits and stem borer resistance
2. estimate some genetic parameters on the genotypes studied
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